Title of Invention	SURFACE MODIFIED ZEOLITE
Abstract	Present invention deals with the cost effective surface modified zeolite materials developed from commercial zeolites and flyash based zeolites treating with surface modifiers like hexadecyltrimethyl ammonium bromide (HDTMA-Br). The formation of zeolitic materials with anionic characteristics requires treatment with surfactant with initial concentrations greater than its critical micelle concentration (CMC). The sorption of oxyanions on surfactant modified zeolite (SMZ) may be attributed to surface complexation and surface precipitation. Incorporation of metal ions on SMZ showed improved anion uptake for dearsnification of water probably due to synergistic effect and is able to meet the stringent target of 10 ppb of As on portable water being adopted by most of the countries. High selectivity, faster kinetics and high adsorption capacity ensures cost effectiveness of this product as compared to other low cost products for dearsenification. Zeolite analogues with anionic characteristics have been developed for their applications for removal of arsenic from water. The material developed can also be used to remove other anions like chromium and seleniums

Title of Invention

SURFACE MODIFIED ZEOLITE

Abstract

Present invention deals with the cost effective surface modified zeolite materials developed from commercial zeolites and flyash based zeolites treating with surface modifiers like hexadecyltrimethyl ammonium bromide (HDTMA-Br). The formation of zeolitic materials with anionic characteristics requires treatment with surfactant with initial concentrations greater than its critical micelle concentration (CMC). The sorption of oxyanions on surfactant modified zeolite (SMZ) may be attributed to surface complexation and surface precipitation. Incorporation of metal ions on SMZ showed improved anion uptake for dearsnification of water probably due to synergistic effect and is able to meet the stringent target of 10 ppb of As on portable water being adopted by most of the countries. High selectivity, faster kinetics and high adsorption capacity ensures cost effectiveness of this product as compared to other low cost products for dearsenification. Zeolite analogues with anionic characteristics have been developed for their applications for removal of arsenic from water. The material developed can also be used to remove other anions like chromium and seleniums

Full Text	Field of invention: The present invention relates to a surface modified zeolite. Further, it relates to a process for synthesis of surface modified zeolites for sequestration of anions. More particularly, it relates to a process for removal of toxic elements from water using surface modified zeolite and recovering of the said surface modified zeolite Background and prior art of the Invention: In the backdrop of the widespread public concern about vast sections of population potentially like West-Bengal (India) and Bangladesh exposed to consumption of ground water containing high concentration of arsenic, the urgency for delineating appropriate treatment strategy for arsenic removal is realized to overcome the grave threat of chronic arsenic poisoning. Recent epidemiogical evidence of the toxicity of inorganic arsenic suggests that the current maximum contaminant level (MCL) may not be sufficiently protective for human health; the probable WHO guideline value of 10 \|j.g/L is based on both estimated health risks and the practical quantitation level. The estimated cost of compliance with more stringent levels (in the range 2-20 \|o.g/L) is quite high. The existing treatment technologies, such as coagulation, softening, and adsorption on alumina or activated carbon and reverse osmosis accomplish arsenic removal to meet the current standard of 50 u.g/L. However, imposition of low arsenic MCL is likely to require implementation of new treatment practices or significant modification of the existing treatment practices. It needs to be emphasized that only a few de-arsenification technologies in vogue have been successfully demonstrated in the field. To achieve this stringent target, novel materials need to be developed wherein zeolites are emerging as potential materials, which can be suitably functionalised to target specific pollutants of concern. Zeolites can be best defined as hydrated crystalline, alumino-silicates with uniform pore size, reversible hydration, ion-exchanging sorptive, and sieving ability. These characteristics are to be exploited for targeting anions in specific arsenate/ arsenite ion. It is really challenging to tackle anionic pollutants using functionalised faujasitic zeolites and has been achieved by modifying the surface of the zeolites to selectively target anion. Reference may be made to Li, Zhaohui, et al. (2000) wherein they studied the removal of oxyanions viz. nitrate, arsenate, chromate, etc. using surface modified clay. Natural kaolinite was treated with hexadecyltrimethylammonium bromide (HDTMA-Br) to a level twice than that of the cation exchange capacity (CEC). Sorption of each oxyanions was well described by the Langmuir isotherm. Desorption of bromide counter ion indicated that each of the oxyanions was retained by ion exchange on HDTMABr bilayer formed on the organo-kaolinite. It was unaffected by solution in the pH range of 5-9, but at pH 11 the bilayer was affected due to competition of OH" for the anion exchange sites. The results demonstrated that properly prepared organoclays could remove oxyanions as well as non-polar organics, from contaminated water. Reference may be made to Krishana et al. (2001) wherein adsorption of chromate by surface modified clays like kaolinite and montomorillinonite modified with cationic surfactant hexadecyltrimethylammonium bromide was reported. It was observed that the amount of chromate absorbed is dependent on pH and that the removal goes on decreasing with increasing pH and it becomes negligible over pH 8 (23). Clays also have the inherent disadvantage of swelling and shrinkage associated with them and therefore cannot be used effectively for treatment purposes. Reference may also be made to Li et al. (1998) wherein it has been reported that planar nitrate sorbs more on surfactant modified zeolite surface than tetrahedral chromate. In the presence of sulphate or nitrate, chromate sorption is hindered due to competition or sorption sites, quantitative sorption of nitrate and chromate and desorption of bromide indicate that the sorption of oxyanions is primarily due to surface anion exchange. However, the material has limited exchange potential due to limited exchange capacity of the natural zeolite. Reference may be made to Tucker et al. (1995) wherein a method for removing anions from water is provided, wherein a complexing agent such as a cationic polyelectrolyte is added to unreacted water. The cationic polyelectrolyte complexes with anions, such as chromate and are filtered. The complex is then treated with a regeneration agent, such as barium chloride or lead chloride to precipitate ions and to regenerate complexing agent, which can be reused for water treatment. However, the method faces difficulty in its practical application for drinking water wherein the requirement of an ultra filtration membrane to retain the retention complex and then regeneration of the same makes the process tedious and expensive. Reference may be made to Hamann et al. (1994) wherein coagulation and lime softening was reported extensively for the removal of arsenic. Adsorption - coprecipitation with hydrolysing metals such as A13+ and Fe3+ is the most commonly used treatment technique for removing arsenic from water. Iron coagulation achieves high As (III) and As (V) removal than alum coagulation. This mode of treatment generates sludge, disposal of which, in turn maybe a problem. Willey (1987) studied the use of treatment processes such as reverse osmosis (RO), ion exchange, adsorption or electrodialysis. These methods are quite expensive for usage in domestic purposes. Reference may be made to Huang et al. (1989) wherein arsenic removal by adsorption has also been evaluated extensively. It was reported therein that activated carbon adsorption was not effective for the removal of arsenic, but pre-treatment of activated carbon with iron salts has been shown to improve the sorption capacity of arsenic. This method suffers form drawback of having lower and limited loading of iron, which in turns decreases, the adsorption capacity. Reference may be made to Bowman et al. (1998) wherein the uptake of the surfactants hexadecyltrimethylammonium bromide (HDTMA-Br) by a natural clinoptilolite rich zeolite and subsequent retention of aqueous solutes was studied. SMZ has shown weak sorption capacity for cations such as Pb(II), Sr(II), and strong sorption for anions such as CrO42". This is in contrast to the natural zeolite, which are good cation exchangers. The results suggested formation of stable HDTMABr bilayer on the external surface of zeolite, which retained anions via anion exchange mechanism. SMZ thus proved to be a useful sorbent for anion removal. However, natural zeolite by virtue of its low exchange capacity and other impurities associated, sorbs anion to a lower degree, which can be improved by using synthetic zeolites. Reference may be made to Alkesaddra et al. (2000) wherein adsorption of sulphate, hydrochromate, and dihydrogen phosphate, anions on the surfactant-modified clinoptilolite was studied. The SMZ was prepared by the adsorption of cis-1 aminooctaden-9 (oleyamine) on both modified and unmodified natural clinoptilolite. It was observed that oleyamine adsorbed on H+-clinoptiolite by protonation of NHa group has shown strong anion adsorbing tendency as compared to Ca and Na-clinoptilolite derivatives, which are weak anion adsorbents. The differences in anion adsorption are attributed to the fact that oleylamine forms hydrogen bonding with Ca and Na-clinoptilolite and thus yields insufficient adsorption sites for anions. Reference may be made to U.S. Patent 6,326,326, (December 4, 2001) Feng et al. wherein, they developed an organized assembly of functional molecules with specific interfacial functionality (functional group(s)) was attached to available surfaces including within mesopores of a mesoporous material. The method of which the present invention avoids the standard base soak that would digest the walls between the mesopores by boiling the mesoporous material in water for surface preparation then removing all but one or two layers of water molecules on the internal surface of a pore. Suitable functional molecule precursor is then applied to permeate the hydrated pores and the precursor then undergoes condensation to form the functional molecules on the interior surface(s) of the pore(s). These materials are reported to perform at very low concentration and have high adsorption capacity. Reference may be made to U.S. Patent 5,833,739, (November 10,1998) wherein, Klatte, et al. developed a process for coating zeolite crystals with paraffin, a wax other than paraffin, a fat or oil, or a mixture of at least one QAC and a wax, fat, or oil was reported. Preferably, the crystals were dehydrated until they have about 5% moisture content, and were then mixed with paraffin to produce paraffin-coated zeolite crystals having a desired content of paraffin. Zeolite crystal having pores coated with wax, fat, oil, or a mixture of at least one QAC and wax, fat, or oil is positively charged and has tendency to attract anions. The coating of paraffin/wax applied to zeolite crystal prior to adsorption of QAC may limit its application for removal of anions; in specific arsenic from drinking water. Reference may be made to Zhaohui Li et al. (1999) wherein, Natural zeolite and ZVI were homogenized and pelletized to maintain favourable hydraulic properties while minimizing materials segregation due to bulk density difference. The zeolite/ZVI pellets were modified with the cationic surfactants hexadecyltrimethyl ammonium bromide to increase contaminant sorption and thus the contaminant concentration on the solid surface. Results of chromate sorption /reduction indicates that the chromate sorption capacity of palletised SMZ/ZVI is at least 1 order of magnitude higher than that of zeolite/ZVI pellets. The SMZ material developed in the present invention overcomes the following drawbacks of the conventional materials in vogue: > Lack of selectivity of conventional adsorbents for arsenic at low concentrations > Lack of versatility of conventional for adsorbents for sorption of wide range of pollutants ranging from cationic to anionic > Limited efficiency of conventional adsorbent > Frequent regeneration and disposal by virtue of its possible conversion to value added ceramic precursors by heat treatment > Transfer of arsenic by stabilization of SMZ at higher temperature > Cost effectiveness of other adsorbents by offering single unit for wide array of pollutants vis-a-vis multiple units required for targeting wide array of pollutants > Sludge generation associated with conventional chemical method viz. alum treatment, chemical precipitation etc. > Hazardous chemical handling etc. by providing technically non-tedious and clean process. > Improvisation in quality of life vis-a-vis improved quality of water. Objects of the invention: The main object of the present invention is to provide surface modified zeolites. Another object of the present invention is to provide a process for synthesis of surface modified zeolites for sequestration of anions. Yet another object of the present invention to provide a process for removal of toxic elements from water using surface modified zeolite and recovering of the said surface modified zeolite Still another object of the present invention is to provide a process for removal of toxic elements such as chromate, arsenate and selenate from water using surface modified zeolite a surface modified zeolite. Detailed description of the invention: Accordingly, the present invention provides a surface modified zeolites comprising: a) a zeolite selected from the group of zeolite A, zeolite X, flyash based zeolite, faujasitic zeolite of Y type; b) one of the modifier selected from the group of surfactant, surface modifier, metal chelating ligand; c) and iron wherein the ratio of the ingredient present in the said surface modified zeolite ranges from 1 : 0.003 : 0.25 to 1 : 0.045 : 25 respectively. In an embodiment of the present invention, the surfactant used is selected from the group of hexamdecyltrimethyl ammonium bromide (HDTMA-Br), sodium lauryl sulphate and other related compounds. In another embodiment of the present invention, the surface modifier used is selected from the group of tetrapropoylammonium bromide (TPA-Br), tetramethylammonium bromide (TBA-Br), tetramethylammonium bromide (TMA-Br) and related compounds. In further another embodiment of the present invention, the metal chelating ligands used is selected from the group of dimercaptosuccinic acid DMSA), dimercaptopropionic acid and related compounds. In yet another embodiment of the present invention, the surface modified zeolite synthesized has the following characteristics: calcium binding capacity: 400meq/100g surface area: 500m2/g crystallinity: 90-92% cubic crystal structure dso average particle size of 4-10 \i Further, the present invention also provides a process for the synthesis of surface modified zeolites useful for sequestration of anions, wherein the said process comprising the steps of: a) washing the zeolite selected from the group of zeolite A, zeolite X, flyash based zeolite, faujasitic zeolite of Y type etc. with distilled water followed by post modification using one of the modifier selected from the group of surfactant, surface modifier or metal chelating ligand by mixing and stirring of zeolite and modifier for 6- 8hratpH6.0topH11.0; b) filtering and washing the product obtained from step (a); c) drying the product obtained from step (b) at 90-100°C for 2-3 hr to obtain surface modified zeolite materials; d) filtering the surface modified zeolite materials obtained from step (c) to get surface modified zeolite crystals or optionally subjecting the surface modified zeolite to treatment with iron to get surface modified zeolite crystals In an embodiment of the present invention, the surface modified zeolite synthesized has the following characteristics: calcium binding capacity: 400meq/100g surface area: 500m2/g crystallinity: 90-92% cubic crystal structure d50 average particle size of 4-10\|j. In another embodiment of the present invention, the surfactant used is selected from the group of hexamdecyltrimethyl ammonium bromide (HDTMA-Br), sodium lauryl sulphate, and other related compounds. In further another embodiment of the present invention, faujasitic zeolites of A & Y type is used for post modification using surfactants. In yet another embodiment of the present invention faujasitic zeolite of A-type is post treated with surfactant viz. Hexadecyltrimethyl ammonium bromide (HDTMA-Br) to synthesize surface modified zeolite (SMZ-A). In still another embodiment of the present invention, faujasitic zeolite of Y type is post treated with surfactant viz. HDTMA-Br to synthesis surface modified zeolite (SMZ-Y). In still another embodiment of the present invention, the surface modifiers is selected from the group of tetrapropoylammonium bromide (TPA-Br), tetramethylammonium bromide (TBA-Br), tetramethylammonium bromide (TMA-Br) and related compounds. In still another embodiment of the present invention, zeolite of Y and A type were subjected to different other surface modifiers like quaternary ammonium compounds viz. TPA-Br, TBA-Br. In still another embodiment of the present invention, the metal chelating ligands used is selected from the group of dimercaptosuccinic acid DMSA), dimercaptopropionic acid and related compounds. In still another embodiment of the present invention, zeolite of Y and A type were subjected to metal chelating ligands viz; Dimercaptosucinnic acid, dimercaptopropoionic acid. In still another embodiment of the present invention, the concentration of surfactant, surface modifier, and metal chelating ligand is in the range from 200 mg/1 to 2,000 mg/1. In still another embodiment of the present invention, the iron treatment is carried out by using ferrous sulphate solution in the concentration ranges from 0.1 to l.OM. In still another embodiment of the present invention, SMZs were thoroughly characterized to study their structural and thermal stability using XRD, SEM, and particle size analysis. Further, the present invention also provides a method for removal of anionic pollutants from water using surface modified zeolite and recovery of the said surface modified zeolite, wherein the said method comprising the steps of: a) contacting anionic pollutants containing water with surface modified zeolite for 0-10 minutes; b) subjecting the anionic pollutants sorbed surface modified zeolite obtained from step (a) to high temperature treatment at 700-800 degree C for its conversion into ceramic precursors or optionally recovering the surface modified zeolite by using caustic soda solution. In an embodiment of the present invention, the simulated water containing anionic pollutants is prepared by dissolving sodium salt of arsenate and chromate In another embodiment of the present invention, the said pollutants are selected from the group of chromate, arsenate and selenate. In further another embodiment of the present invention, the concentration of said pollutants arsenate is in the range of 1-150 mg/1. In yet another embodiment of the present invention, the concentration of arsenate is in the range of 1-150 mg/1. In still another embodiment of the present invention, the concentration of chromate is in the range of 1-100 mg/1. In still another embodiment of the present invention, the surface modified zeolite used for the removal of said pollutants in the range of 0.2-125/25 ml. In still another embodiment of the present invention, the 0.1-1M caustic soda solution used for recovery of said surface modified zeolite is in the range. Surface modified zeolite (SMZ) materials have been developed from zeolite, which are being used for targeting wide array of pollutants ranging from cationic to anionic components. The need for this kind of versatile materials for environmental remediation is being realized, wherein, the commercially available zeolites are finding restricted usage due to prohibitive costs for tackling individual pollutants. To overcome this problem, a process for SMZ has been developed which can be exploited for wide array of pollutants thus overcoming the cost implications of tackling individual pollutants. It is of immense practical importance to develop materials with tailored properties to sequester anionic pollutants in addition to cationic pollutants. Zeolites are alumino-silicate materials with properties to attract positive charged ions and, therefore, are widely used for sequestration of cationic pollutants like lead, cadmium and also ammonium ion, generally through ion-exchange process. The first step towards synthesis of SMZs is surface treatment to modify the surface chemistry of zeolite through a simple process of surface modification using surfactant and quaternary ammonium compounds. Treatment of zeolites with surfactant concentration less than critical micelle concentration (CMC) results in the formation of SMZ with hydrophobic characteristics whereas treatment of zeolites with surfactant concentration greater than its CMC renders anionic characteristic to the SMZ. These anionic SMZ have been given an additional treatment with FeSO4 solution to incorporate iron for synergistic effect not reported so far to the best of our knowledge. Treatment of zeolite with mercapto-compounds results in the materials with enhanced selectivity and affinity. This material has not been reported so far to the best of our knowledge. The development of such innovative versatile materials is expected to bring out revolutionary changes in the area of water and waste water treatment by offering a single unit vis-a-vis multiple units required for treatment of waste, which are generally multi component. In the present invention, it is proposed to overcome the major problem of arsenic removal by developing new materials to attain the stringent target of 10 ppb and offering cost attractive alternative to conventional methods and materials. Faujasitic zeolites are basically cation exchangers and hydrophilic in nature and cannot be used for targeting anions. This challenge is to be met by modifying the surface of the zeolites by treating it with surface modifiers like surfactants and quaternary ammonium and mercapto compounds. The SMZ with increased loading results in the formation of bilayer, which has an affinity for anionic compounds. Synthesis of Surface Modified Zeolite Zeolite was washed with distilled water several times till its pH reaches to 10.0 to 10.5. Pre-weighed quantity of washed zeolite sample was then mixed with different initial concentration of surfactant i.e. hexadecyltrimethyl ammonium bromide solution in 1:100 (solid: liquid) ratio. The surfactant concentration was ranging from 100 mg/1 to 800 mg/1 for 10 g of zeolite. The solution was agitated for 7 to 8 hr at 150 rpm on a shaker at pH 8.0 to 8.5. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 4 to 6 hr. The SMZ-A sample synthesized as such was then mechanically ground with a mortar and pestle to fine particle size. Surface modified zeolite having variable surfactant loading was then used for removal of arsenic. The same procedure was repeated for modification of surface zeolite-A/X samples as above for comparative studies. The different surface modified zeolites having different surfactant loading was then used for removal of arsenic in water. Synthesis of Metal Treated Surface Modified Zeolite Zeolite A was washed with distilled water several times till its pH reaches to 10.0 to 10.5. Pre weighed quantity of washed zeolite A sample was then mixed with different initial concentration of surfactant i.e. hexadecyltrimethyl ammonium bromide (HDTMA-Br) solution in 1:100 (solid : liquid) ratio. The surfactant concentration was ranging from 100 mg/1 to 800 mg/1 for 10 g of zeolite A. The solution was agitated for 7 to 8 hr at 150 rpm on a shaker at pH 8.0 to 8.5. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 6 hr. The SMZ-A sample synthesized as such was then mechanically ground with a mortar and pestle to fine particle size. The metal treatment was given by stirring the SMZ-A in varying quantities of FeSC>4 solution (0.1 - 0.5 M) for 24 hours. Conversion to ceramic precursors Zeolite used for sorption of arsenate was separated and dried at 100°C. The dried mass was heated up to 300°C. The heated mass was cooled and crushed. It was then subjected to heating up to 800°C. The sintered mass was subjected to TCLP test for leaching of As and was dissolved in hydrochloric acid to monitor the As content. Methods of Analysis Pre-weighted quantity of surface modified zeolite was mixed with 25 ml of solution of arsenic with concentration ranging from 1-5 mg/1 of variable initial concentration. The pH was maintained at about 6.5 to 7.0 by the addition of dilute HC1. The mixture was then shaken on shaker at 150 rpm and filtered. The filtrate was analysed for arsenic using AAS and ICP-AES. Characterization SMZ-A, which appears to be suitable for removal of anions, has been characterized with respect to crystallinity, particle size and morphological characteristics. The morphological characteristics of Zeolite-A also appear to be different from that of SMZ-A (P.I) indicating sorption of surfactant. XRD patterns of zeolite-SMZ-A are less in comparison with FAZ-A. Present invention is applicable to the preparation of a very large species of materials since there are more than 140 zeolite crystal structures and large number of surface modifying agent. The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of present invention. Example 1 Zeolite-A was washed with distilled water several times till its filtrate pH reaches to 10.0 to 10.5. lOg of washed zeolite A sample was then mixed with surfactant i.e. hexadecyltrimethyl ammonium bromide solution in 1:100 (solid: liquid) ratio. The surfactant concentration was 100mg/l. The sample was designated as SMZ-l.The solution was agitated for 7 to 8 hr at 150 rpm on shaker at pH 8.0 to 8.5. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 6 hr. The SMZ-A sample synthesized as such was then mechanically ground with a mortar and pestle to fine particle size. The powdered SMZ-A was used for adsorption of arsenic .The efficiency of sample is illustrated in Table 1. (Table Removed) Example The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 200mg/l. The sample was designated as SMZ-2. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table 1. Example I The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 300mg/l. The sample was designated as SMZ-3. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Tablel. Example I The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 500mg/l. The sample was designated as SMZ-4. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example Id The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 800mg/l. The sample was designated as SMZ-5. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example le The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 1000mg/l. The sample was designated as SMZ-6. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example If The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 1200mg/l. The sample was designated as SMZ-7. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table 1. Example Ig The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 1500mg/l. The sample was designated as SMZ-8. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table 1. Example Ih The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 1800mg/I. The sample was designated as SMZ-9. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table 1. Example li The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 2000mg/l. The sample was designated as SMZ-10. The powdered SMZ-A was used for. adsorption of arsenic. The efficiency of sample is illustrated in Table 1. Example Ij The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 2200mg/l. The sample was designated as SMZ-11. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table 1. Example Ik The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 2500mg/l. The sample was designated as SMZ-12. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example - 2 Zeolite A was washed with distilled water several times till pH of the filtrate is 10.0 to 10.5. lOg of washed zeolite A sample was then mixed with quaternary ammonium compounds (QAC) solution in 1:100 (solid: liquid) ratio. The QAC concentration was 100 mg/1. The solution was agitated for 7 to 8 hr at 150 rpm on gyratory shaker at pH 8.0 to 8.5. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 6 hr. The sample was designated as SMZ-13. The SMZ-A sample synthesized as such was then mechanically ground with a mortar and pestle to fine particle size. The powdered SMZ-A was used for adsorption of arsenic .The efficiency of sample is illustrated in Table 2. (Table Removed) Example 2a The same procedure Was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 200mg/l. The sample was designated as SMZ-14. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in. Example 2b The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 300mg/l. The sample was designated as SMZ-15. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example 2c The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 500mg/l. The sample was designated as SMZ-16. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example 2d The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 800mg/l. The sample was designated as SMZ-17. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table2. Example 2e The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 1000mg/l. The sample was designated as SMZ-18. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example 2f The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 1200mg/l. The sample was designated as SMZ-19. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table2. Example 2g The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 1500mg/l. The sample was designated as SMZ-20. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example 2h The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 1800mg/l. The sample was designated as SMZ-21. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example 2i The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 2000mg/l. The sample was designated as SMZ-22. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example 2j The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 2200mg/I. The sample was designated as SMZ-23. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example 2k The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 2500mg/l. The sample was designated as SMZ-24. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Example 3 The same procedure was repeated as described in example 1 for preparation of SMZ-A-5. The as-synthesized SMZ-A-5 was then used for removal of arsenic at initial concentration of 5.0 mg/1. The results are detailed (Table Removed) Example 3b The same procedure was repeated as described in example 3 except for the initial concentration of arsenic solution wherein the concentration employed was 25 mg/1. The results are detailed (Table Removed) Example 4 The same procedure was repeated as described in example 1 for preparation of SMZ-A-5. The as-synthesised SMZ-A-5 was then used for removal of chromate at initial concentration of 5.0 mg/1. The results are detailed in Table 4 (Table Removed) . Example 4a The same procedure was repeated as described in example 4 except for initial concentration of arsenic solution wherein the concentration employed was 10 mg/1. The results are detailed in Table 4a. (Table Removed) Example 4b The same procedure was repeated described as in example 4 except for initial concentration of arsenic solution wherein the concentration employed was 25 mg/1. The results are detailed in Table 4b. (Table Removed) Example 5 The same procedure was repeated as described in example 1 for preparation of SMZ wherein commercial zeolite-A was treated with surfactant concentration of 200 mg/1. The as-synthesized sample was further treated with 0.2 M solution of FeSC>4 to obtain the surfactant and metal treated SMZ designated as SMZ-A-25. The as-synthesized samples were used to study the removal of arsenic at fixed initial concentration of 1 mg/1. The results are detailed in (Table Removed) Example 5a The same procedure was repeated as described in example 5 except for variation in treatment with surfactant wherein the concentration employed was 1000mg/l. The sample was designated as SMZ-A-26. The as-synthesised sample was used for adsorption of arsenic. The efficiencies of samples are illustrated in Table 5. Example 5b The same procedure was repeated as described in example 5 except for variation in treatment with surfactant wherein the concentration employed was 2000mg/l. The sample was designated as SMZ-A-27. The as synthesised sample was used for adsorption of arsenic. The efficiencies of samples are illustrated in Table 5. Example 6 The same procedure was repeated as described in example 1 for preparation of SMZ wherein commercial zeolite-A was treated with surfactant concentration of 200 mg/1. The as-synthesized sample was further treated with 0.2 M solution of FeSC>4 to obtain the surfactant and metal treated SMZ designated as SMZ-A-28. The as-synthesized samples were used to study the removal of arsenic at fixed initial concentration of 1 mg/1. The results are detailed in Table 6. (Table Removed) N.D.: Non Detectable * Initial surfactant concentration used for treatment ** Initial metal concentration used for treatment Example 6a The same procedure was repeated as described in example 6 except for variation in treatment with surfactant wherein the concentration employed was 1000mg/l. The sample was designated as SMZ-A-29. The as-synthesised sample was used for adsorption of arsenic. The efficiencies of samples are illustrated in Table 6. Example 6b The same procedure was repeated as described in example 6 except for variation in treatment with surfactant wherein the concentration employed was 2000mg/l. The sample was designated as SMZ-A-30. The as-synthesised sample was used for adsorption of arsenic. The efficiencies of samples are illustrated in Table 6. (Table Removed) Example 7 Zeolite-A was washed with distilled water several times till its filtrate pH reaches to 10.0 to 10.5. lOg of washed zeolite A sample was then mixed with 0.2 M solution of ferrous sulphate. The solution was agitated for 7 to 8 hr at 150 rpm on shaker. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 6 hr. The iron treated zeolite samples as synthesized was given the same treatment as detailed in example 1 to obtain the metal and surfactant treated SMZ designated as SMZ-A-31. SMZ-A-32 and SMZ-A-33 were synthesised by treating iron zeolite-A with surfactant concentrations of 1000 mg/1 and 2000mg/l. The as-synthesized samples were used to study the removal of arsenic at fixed initial concentration of 1 mg/1. The results are detailed in Table 7. N.D.: Non Detectable * Initial surfactant concentration used for treatment ** Initial metal concentration used for treatment Example 8 The same procedure was repeated as described in example 7 except for treatment with tetrabutyl ammonium hydroxide (TBAOH) as surface modifiers. The TBAOH concentration used was 200 mg/1 and the sample was designated as SMZ-A-34. SMZ-A-35 and SMZ-A-36 were synthesized by treating zeolite-A with TBAOH concentration of 1000 mg/1 and 2000 mg/1. The as-synthesised samples were used for adsorption of arsenic. The efficiencies of samples are illustrated in Table 8. (Table Removed) N.D.: Non Detectable * Initial surfactant concentration used for treatment ** Initial metal concentration used for treatment Example 9 Zeolite-A was washed with distilled water several times till its filtrate pH reaches to 10.0 to 10.5. Ig of washed zeolite A sample was then mixed with an alcoholic solution of 2,3-dimercapto-1-propanesulphonic acid (DMSA). The concentration of DMSA used was 3000 mg/1. The solution was agitated for 4 to 5 hr at 150 rpm on shaker. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 6 hrs. The sample synthesized as such was then mechanically ground with a mortar and pestle to fine particle size. The sample was designated as SMZ-A-37. SMZ-A-38 and SMZ-A-39 were synthesized by treating zeolite-A with DMSA concentration of 6000 mg/1 and 9000 mg/1. The as-synthesised samples were used for adsorption of arsenic .The efficiencies of samples are illustrated in Table 9. (Table Removed) Example 10 The same procedure was repeated as described in example 12 except for the ligand wherein the DMSA was replaced with 2,3-dimercapto-l-propanol (DMPA). The sample was 25 designated as SMZ-A-40. SMZ-A-41 and SMZ-A-42 were synthesized by treating zeolite-A with DMPA concentration of 6000 mg/1 and 9000 mg/1. The as synthesised samples were used for adsorption of arsenic .The efficiencies of samples are illustrated in Table 10. (Table Removed) Advantages; The main advantages of the present invention are: Offers selectivity over conventional adsorbents for arsenic at low concentrations Offers versatility over conventional adsorbents for sorption of wide range of pollutants ranging from cationic to anionic High adsorption capacity over conventional adsorbents Possible frequent regeneration and disposal by virtue of its conversion to value added ceramic precursors by heat treatment Stabilization/immobilisation of arsenic in SMZ at higher temperature. Offers cost effectiveness over other adsorbents by offering single unit for wide array of pollutants/chemical species vis-a-vis multiple units required for targeting wide array of pollutants/chemical species. No problem of sludge generation which are generally associated with conventional chemical methods viz. alum treatment, chemical precipitation etc. No problem of hazardous chemical handling etc. by providing technically non-tedious and clean process. 1. Surface modified zeolites comprising: a) zeolite selected from the group of zeolite A, zeolite X, flyash based zeolite, faujasitic zeolite of Y type b) modifier selected from the group of surfactant, surface modifier, metal chelating ligand c) iron in the ferrous state ( ~ e ~ + ) in the ratio that ranges from 1 : 0.003 : 0.25 to 1 : 0.045 : 25 respectively. 2. Surface modified zeolite as claimed in claim 1, wherein the said surfactant is selected from the group of hexamdecyltrimethyl ammonium bromide (HDTMA-Br), sodium lauryl sulphate. 3. Surface modified zeolite as claimed in claim 1, wherein the said surface modifier is selected from the group of tetrapropoylammonium bromide (TPA-Br), tetramethylammonium bromide (TBA-Br), tetramethylammonium bromide (TMA-Br). 4. Surface modified zeolite as claimed in claim 1, wherein one of the modifier of metal chelating ligands is selected from the group of dimercaptosuccinic acid (DMSA), dimercaptopropionic acid. 5. Surface modified zeolites as claimed in claim 1 is useful for removal of toxic elements chromate and arsenate from water

Full Text

Field of invention:
The present invention relates to a surface modified zeolite.
Further, it relates to a process for synthesis of surface modified zeolites for sequestration of anions.
More particularly, it relates to a process for removal of toxic elements from water using surface modified zeolite and recovering of the said surface modified zeolite
Background and prior art of the Invention:
In the backdrop of the widespread public concern about vast sections of population potentially like West-Bengal (India) and Bangladesh exposed to consumption of ground water containing high concentration of arsenic, the urgency for delineating appropriate treatment strategy for arsenic removal is realized to overcome the grave threat of chronic arsenic poisoning. Recent epidemiogical evidence of the toxicity of inorganic arsenic suggests that the current maximum contaminant level (MCL) may not be sufficiently protective for human health; the probable WHO guideline value of 10 |j.g/L is based on both estimated health risks and the practical quantitation level. The estimated cost of compliance with more stringent levels (in the range 2-20 |o.g/L) is quite high. The existing treatment technologies, such as coagulation, softening, and adsorption on alumina or activated carbon and reverse osmosis accomplish arsenic removal to meet the current standard of 50 u.g/L. However, imposition of low arsenic MCL is likely to require implementation of new treatment practices or significant modification of the existing treatment practices. It needs to be emphasized that only a few de-arsenification technologies in vogue have been successfully demonstrated in the field. To achieve this stringent target, novel materials need to be developed wherein zeolites are emerging as potential materials, which can be suitably functionalised to target specific pollutants of concern. Zeolites can be best defined as hydrated crystalline, alumino-silicates with uniform pore size, reversible hydration, ion-exchanging sorptive, and sieving ability. These characteristics are to be exploited for targeting anions in specific arsenate/ arsenite ion. It is really challenging to tackle anionic pollutants using functionalised faujasitic zeolites and has been achieved by modifying the surface of the zeolites to selectively target anion.
Reference may be made to Li, Zhaohui, et al. (2000) wherein they studied the removal of oxyanions viz. nitrate, arsenate, chromate, etc. using surface modified clay. Natural kaolinite was treated with hexadecyltrimethylammonium bromide (HDTMA-Br) to a level twice than that of the cation exchange capacity (CEC). Sorption of each oxyanions was well described

by the Langmuir isotherm. Desorption of bromide counter ion indicated that each of the oxyanions was retained by ion exchange on HDTMABr bilayer formed on the organo-kaolinite. It was unaffected by solution in the pH range of 5-9, but at pH 11 the bilayer was affected due to competition of OH" for the anion exchange sites. The results demonstrated that properly prepared organoclays could remove oxyanions as well as non-polar organics, from contaminated water.
Reference may be made to Krishana et al. (2001) wherein adsorption of chromate by surface modified clays like kaolinite and montomorillinonite modified with cationic surfactant hexadecyltrimethylammonium bromide was reported. It was observed that the amount of chromate absorbed is dependent on pH and that the removal goes on decreasing with increasing pH and it becomes negligible over pH 8 (23). Clays also have the inherent disadvantage of swelling and shrinkage associated with them and therefore cannot be used effectively for treatment purposes.
Reference may also be made to Li et al. (1998) wherein it has been reported that planar nitrate sorbs more on surfactant modified zeolite surface than tetrahedral chromate. In the presence of sulphate or nitrate, chromate sorption is hindered due to competition or sorption sites, quantitative sorption of nitrate and chromate and desorption of bromide indicate that the sorption of oxyanions is primarily due to surface anion exchange. However, the material has limited exchange potential due to limited exchange capacity of the natural zeolite.
Reference may be made to Tucker et al. (1995) wherein a method for removing anions from water is provided, wherein a complexing agent such as a cationic polyelectrolyte is added to unreacted water. The cationic polyelectrolyte complexes with anions, such as chromate and are filtered. The complex is then treated with a regeneration agent, such as barium chloride or lead chloride to precipitate ions and to regenerate complexing agent, which can be reused for water treatment. However, the method faces difficulty in its practical application for drinking water wherein the requirement of an ultra filtration membrane to retain the retention complex and then regeneration of the same makes the process tedious and expensive.
Reference may be made to Hamann et al. (1994) wherein coagulation and lime softening was reported extensively for the removal of arsenic. Adsorption - coprecipitation with hydrolysing metals such as A13+ and Fe3+ is the most commonly used treatment technique for removing arsenic from water. Iron coagulation achieves high As (III) and As (V) removal

than alum coagulation. This mode of treatment generates sludge, disposal of which, in turn maybe a problem.
Willey (1987) studied the use of treatment processes such as reverse osmosis (RO), ion exchange, adsorption or electrodialysis. These methods are quite expensive for usage in domestic purposes.
Reference may be made to Huang et al. (1989) wherein arsenic removal by adsorption has also been evaluated extensively. It was reported therein that activated carbon adsorption was not effective for the removal of arsenic, but pre-treatment of activated carbon with iron salts has been shown to improve the sorption capacity of arsenic. This method suffers form drawback of having lower and limited loading of iron, which in turns decreases, the adsorption capacity.
Reference may be made to Bowman et al. (1998) wherein the uptake of the surfactants hexadecyltrimethylammonium bromide (HDTMA-Br) by a natural clinoptilolite rich zeolite and subsequent retention of aqueous solutes was studied. SMZ has shown weak sorption capacity for cations such as Pb(II), Sr(II), and strong sorption for anions such as CrO42". This is in contrast to the natural zeolite, which are good cation exchangers. The results suggested formation of stable HDTMABr bilayer on the external surface of zeolite, which retained anions via anion exchange mechanism. SMZ thus proved to be a useful sorbent for anion removal. However, natural zeolite by virtue of its low exchange capacity and other impurities associated, sorbs anion to a lower degree, which can be improved by using synthetic zeolites.
Reference may be made to Alkesaddra et al. (2000) wherein adsorption of sulphate, hydrochromate, and dihydrogen phosphate, anions on the surfactant-modified clinoptilolite was studied. The SMZ was prepared by the adsorption of cis-1 aminooctaden-9 (oleyamine) on both modified and unmodified natural clinoptilolite. It was observed that oleyamine adsorbed on H+-clinoptiolite by protonation of NHa group has shown strong anion adsorbing tendency as compared to Ca and Na-clinoptilolite derivatives, which are weak anion adsorbents. The differences in anion adsorption are attributed to the fact that oleylamine forms hydrogen bonding with Ca and Na-clinoptilolite and thus yields insufficient adsorption sites for anions.
Reference may be made to U.S. Patent 6,326,326, (December 4, 2001) Feng et al. wherein, they developed an organized assembly of functional molecules with specific interfacial functionality (functional group(s)) was attached to available surfaces including within

mesopores of a mesoporous material. The method of which the present invention avoids the standard base soak that would digest the walls between the mesopores by boiling the mesoporous material in water for surface preparation then removing all but one or two layers of water molecules on the internal surface of a pore. Suitable functional molecule precursor is then applied to permeate the hydrated pores and the precursor then undergoes condensation to form the functional molecules on the interior surface(s) of the pore(s). These materials are reported to perform at very low concentration and have high adsorption capacity.
Reference may be made to U.S. Patent 5,833,739, (November 10,1998) wherein, Klatte, et al. developed a process for coating zeolite crystals with paraffin, a wax other than paraffin, a fat or oil, or a mixture of at least one QAC and a wax, fat, or oil was reported. Preferably, the crystals were dehydrated until they have about 5% moisture content, and were then mixed with paraffin to produce paraffin-coated zeolite crystals having a desired content of paraffin. Zeolite crystal having pores coated with wax, fat, oil, or a mixture of at least one QAC and wax, fat, or oil is positively charged and has tendency to attract anions. The coating of paraffin/wax applied to zeolite crystal prior to adsorption of QAC may limit its application for removal of anions; in specific arsenic from drinking water.
Reference may be made to Zhaohui Li et al. (1999) wherein, Natural zeolite and ZVI were homogenized and pelletized to maintain favourable hydraulic properties while minimizing materials segregation due to bulk density difference. The zeolite/ZVI pellets were modified with the cationic surfactants hexadecyltrimethyl ammonium bromide to increase contaminant sorption and thus the contaminant concentration on the solid surface. Results of chromate sorption /reduction indicates that the chromate sorption capacity of palletised SMZ/ZVI is at least 1 order of magnitude higher than that of zeolite/ZVI pellets.
The SMZ material developed in the present invention overcomes the following drawbacks of the conventional materials in vogue:
> Lack of selectivity of conventional adsorbents for arsenic at low concentrations
> Lack of versatility of conventional for adsorbents for sorption of wide range of
pollutants ranging from cationic to anionic
> Limited efficiency of conventional adsorbent
> Frequent regeneration and disposal by virtue of its possible conversion to value added
ceramic precursors by heat treatment

> Transfer of arsenic by stabilization of SMZ at higher temperature
> Cost effectiveness of other adsorbents by offering single unit for wide array of
pollutants vis-a-vis multiple units required for targeting wide array of pollutants
> Sludge generation associated with conventional chemical method viz. alum treatment,
chemical precipitation etc.
> Hazardous chemical handling etc. by providing technically non-tedious and clean
process.
> Improvisation in quality of life vis-a-vis improved quality of water.
Objects of the invention:
The main object of the present invention is to provide surface modified zeolites.
Another object of the present invention is to provide a process for synthesis of surface modified zeolites for sequestration of anions.
Yet another object of the present invention to provide a process for removal of toxic elements from water using surface modified zeolite and recovering of the said surface modified zeolite
Still another object of the present invention is to provide a process for removal of toxic elements such as chromate, arsenate and selenate from water using surface modified zeolite a surface modified zeolite.
Detailed description of the invention:
Accordingly, the present invention provides a surface modified zeolites comprising:
a) a zeolite selected from the group of zeolite A, zeolite X, flyash based zeolite,
faujasitic zeolite of Y type;
b) one of the modifier selected from the group of surfactant, surface modifier,
metal chelating ligand;
c) and iron
wherein the ratio of the ingredient present in the said surface modified zeolite
ranges from 1 : 0.003 : 0.25 to 1 : 0.045 : 25 respectively.
In an embodiment of the present invention, the surfactant used is selected from the group of hexamdecyltrimethyl ammonium bromide (HDTMA-Br), sodium lauryl sulphate and other related compounds.

In another embodiment of the present invention, the surface modifier used is selected from the group of tetrapropoylammonium bromide (TPA-Br), tetramethylammonium bromide (TBA-Br), tetramethylammonium bromide (TMA-Br) and related compounds.
In further another embodiment of the present invention, the metal chelating ligands used is selected from the group of dimercaptosuccinic acid DMSA), dimercaptopropionic acid and related compounds.
In yet another embodiment of the present invention, the surface modified zeolite synthesized has the following characteristics:
calcium binding capacity: 400meq/100g
surface area: 500m2/g
crystallinity: 90-92%
cubic crystal structure
dso average particle size of 4-10 \i
Further, the present invention also provides a process for the synthesis of surface modified zeolites useful for sequestration of anions, wherein the said process comprising the steps of:
a) washing the zeolite selected from the group of zeolite A, zeolite X, flyash based
zeolite, faujasitic zeolite of Y type etc. with distilled water followed by post
modification using one of the modifier selected from the group of surfactant, surface
modifier or metal chelating ligand by mixing and stirring of zeolite and modifier for 6-
8hratpH6.0topH11.0;
b) filtering and washing the product obtained from step (a);
c) drying the product obtained from step (b) at 90-100°C for 2-3 hr to obtain surface
modified zeolite materials;
d) filtering the surface modified zeolite materials obtained from step (c) to get surface
modified zeolite crystals or optionally subjecting the surface modified zeolite to
treatment with iron to get surface modified zeolite crystals
In an embodiment of the present invention, the surface modified zeolite synthesized has the following characteristics:
calcium binding capacity: 400meq/100g surface area: 500m2/g crystallinity: 90-92%

cubic crystal structure
d50 average particle size of 4-10|j.
In another embodiment of the present invention, the surfactant used is selected from the group of hexamdecyltrimethyl ammonium bromide (HDTMA-Br), sodium lauryl sulphate, and other related compounds.
In further another embodiment of the present invention, faujasitic zeolites of A & Y type is used for post modification using surfactants.
In yet another embodiment of the present invention faujasitic zeolite of A-type is post treated with surfactant viz. Hexadecyltrimethyl ammonium bromide (HDTMA-Br) to synthesize surface modified zeolite (SMZ-A).
In still another embodiment of the present invention, faujasitic zeolite of Y type is post treated with surfactant viz. HDTMA-Br to synthesis surface modified zeolite (SMZ-Y).
In still another embodiment of the present invention, the surface modifiers is selected from the group of tetrapropoylammonium bromide (TPA-Br), tetramethylammonium bromide (TBA-Br), tetramethylammonium bromide (TMA-Br) and related compounds.
In still another embodiment of the present invention, zeolite of Y and A type were subjected to different other surface modifiers like quaternary ammonium compounds viz. TPA-Br, TBA-Br.
In still another embodiment of the present invention, the metal chelating ligands used is selected from the group of dimercaptosuccinic acid DMSA), dimercaptopropionic acid and related compounds.
In still another embodiment of the present invention, zeolite of Y and A type were subjected to metal chelating ligands viz; Dimercaptosucinnic acid, dimercaptopropoionic acid.
In still another embodiment of the present invention, the concentration of surfactant, surface modifier, and metal chelating ligand is in the range from 200 mg/1 to 2,000 mg/1.
In still another embodiment of the present invention, the iron treatment is carried out by using ferrous sulphate solution in the concentration ranges from 0.1 to l.OM.
In still another embodiment of the present invention, SMZs were thoroughly characterized to study their structural and thermal stability using XRD, SEM, and particle size analysis.

Further, the present invention also provides a method for removal of anionic pollutants from water using surface modified zeolite and recovery of the said surface modified zeolite, wherein the said method comprising the steps of:
a) contacting anionic pollutants containing water with surface modified zeolite
for 0-10 minutes;
b) subjecting the anionic pollutants sorbed surface modified zeolite obtained from
step (a) to high temperature treatment at 700-800 degree C for its conversion
into ceramic precursors or optionally recovering the surface modified zeolite
by using caustic soda solution.
In an embodiment of the present invention, the simulated water containing anionic pollutants is prepared by dissolving sodium salt of arsenate and chromate
In another embodiment of the present invention, the said pollutants are selected from the group of chromate, arsenate and selenate.
In further another embodiment of the present invention, the concentration of said pollutants arsenate is in the range of 1-150 mg/1.
In yet another embodiment of the present invention, the concentration of arsenate is in the range of 1-150 mg/1.
In still another embodiment of the present invention, the concentration of chromate is in the range of 1-100 mg/1.
In still another embodiment of the present invention, the surface modified zeolite used for the removal of said pollutants in the range of 0.2-125/25 ml.
In still another embodiment of the present invention, the 0.1-1M caustic soda solution used for recovery of said surface modified zeolite is in the range.
Surface modified zeolite (SMZ) materials have been developed from zeolite, which are being used for targeting wide array of pollutants ranging from cationic to anionic components. The need for this kind of versatile materials for environmental remediation is being realized, wherein, the commercially available zeolites are finding restricted usage due to prohibitive costs for tackling individual pollutants. To overcome this problem, a process for SMZ has been developed which can be exploited for wide array of pollutants thus overcoming the cost implications of tackling individual pollutants. It is of immense practical importance to develop materials with tailored properties to sequester anionic pollutants in addition to cationic pollutants. Zeolites are alumino-silicate materials with properties to attract positive

charged ions and, therefore, are widely used for sequestration of cationic pollutants like lead, cadmium and also ammonium ion, generally through ion-exchange process. The first step towards synthesis of SMZs is surface treatment to modify the surface chemistry of zeolite through a simple process of surface modification using surfactant and quaternary ammonium compounds. Treatment of zeolites with surfactant concentration less than critical micelle concentration (CMC) results in the formation of SMZ with hydrophobic characteristics whereas treatment of zeolites with surfactant concentration greater than its CMC renders anionic characteristic to the SMZ. These anionic SMZ have been given an additional treatment with FeSO4 solution to incorporate iron for synergistic effect not reported so far to the best of our knowledge. Treatment of zeolite with mercapto-compounds results in the materials with enhanced selectivity and affinity. This material has not been reported so far to the best of our knowledge. The development of such innovative versatile materials is expected to bring out revolutionary changes in the area of water and waste water treatment by offering a single unit vis-a-vis multiple units required for treatment of waste, which are generally multi component.
In the present invention, it is proposed to overcome the major problem of arsenic removal by developing new materials to attain the stringent target of 10 ppb and offering cost attractive alternative to conventional methods and materials. Faujasitic zeolites are basically cation exchangers and hydrophilic in nature and cannot be used for targeting anions. This challenge is to be met by modifying the surface of the zeolites by treating it with surface modifiers like surfactants and quaternary ammonium and mercapto compounds. The SMZ with increased loading results in the formation of bilayer, which has an affinity for anionic compounds.
Synthesis of Surface Modified Zeolite
Zeolite was washed with distilled water several times till its pH reaches to 10.0 to 10.5. Pre-weighed quantity of washed zeolite sample was then mixed with different initial concentration of surfactant i.e. hexadecyltrimethyl ammonium bromide solution in 1:100 (solid: liquid) ratio. The surfactant concentration was ranging from 100 mg/1 to 800 mg/1 for 10 g of zeolite. The solution was agitated for 7 to 8 hr at 150 rpm on a shaker at pH 8.0 to 8.5. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 4 to 6 hr. The SMZ-A sample synthesized as such was then mechanically ground with a mortar and pestle to fine particle size. Surface modified zeolite having variable surfactant loading was then used for removal of arsenic. The same procedure was repeated for modification of surface zeolite-A/X samples as above for comparative studies. The different

surface modified zeolites having different surfactant loading was then used for removal of arsenic in water.
Synthesis of Metal Treated Surface Modified Zeolite
Zeolite A was washed with distilled water several times till its pH reaches to 10.0 to 10.5. Pre weighed quantity of washed zeolite A sample was then mixed with different initial concentration of surfactant i.e. hexadecyltrimethyl ammonium bromide (HDTMA-Br) solution in 1:100 (solid : liquid) ratio. The surfactant concentration was ranging from 100 mg/1 to 800 mg/1 for 10 g of zeolite A. The solution was agitated for 7 to 8 hr at 150 rpm on a shaker at pH 8.0 to 8.5. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 6 hr. The SMZ-A sample synthesized as such was then mechanically ground with a mortar and pestle to fine particle size. The metal treatment was given by stirring the SMZ-A in varying quantities of FeSC>4 solution (0.1 - 0.5 M) for 24 hours.
Conversion to ceramic precursors
Zeolite used for sorption of arsenate was separated and dried at 100°C. The dried mass was heated up to 300°C. The heated mass was cooled and crushed. It was then subjected to heating up to 800°C. The sintered mass was subjected to TCLP test for leaching of As and was dissolved in hydrochloric acid to monitor the As content.
Methods of Analysis
Pre-weighted quantity of surface modified zeolite was mixed with 25 ml of solution of arsenic with concentration ranging from 1-5 mg/1 of variable initial concentration. The pH was maintained at about 6.5 to 7.0 by the addition of dilute HC1. The mixture was then shaken on shaker at 150 rpm and filtered. The filtrate was analysed for arsenic using AAS and ICP-AES.
Characterization
SMZ-A, which appears to be suitable for removal of anions, has been characterized with respect to crystallinity, particle size and morphological characteristics. The morphological characteristics of Zeolite-A also appear to be different from that of SMZ-A (P.I) indicating sorption of surfactant. XRD patterns of zeolite-SMZ-A are less in comparison with FAZ-A.

Present invention is applicable to the preparation of a very large species of materials since there are more than 140 zeolite crystal structures and large number of surface modifying agent.
The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of present invention.
Example 1
Zeolite-A was washed with distilled water several times till its filtrate pH reaches to 10.0 to 10.5. lOg of washed zeolite A sample was then mixed with surfactant i.e. hexadecyltrimethyl ammonium bromide solution in 1:100 (solid: liquid) ratio. The surfactant concentration was 100mg/l. The sample was designated as SMZ-l.The solution was agitated for 7 to 8 hr at 150 rpm on shaker at pH 8.0 to 8.5. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 6 hr. The SMZ-A sample synthesized as such was then mechanically ground with a mortar and pestle to fine particle size. The powdered SMZ-A was used for adsorption of arsenic .The efficiency of sample is illustrated in Table 1.
(Table Removed)
Example
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 200mg/l. The sample was designated as SMZ-2. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table 1.
Example I
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 300mg/l. The sample was designated as SMZ-3. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Tablel.
Example I
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 500mg/l. The sample was designated as SMZ-4. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example Id
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 800mg/l. The sample was designated as SMZ-5. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example le
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 1000mg/l. The sample was designated as SMZ-6. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example If
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 1200mg/l. The sample was designated as SMZ-7. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table 1.
Example Ig
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 1500mg/l. The sample was designated as SMZ-8. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table 1.
Example Ih
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 1800mg/I. The sample was designated as SMZ-9. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table 1.
Example li
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 2000mg/l. The sample was designated as SMZ-10. The powdered SMZ-A was used for. adsorption of arsenic. The efficiency of sample is illustrated in Table 1.
Example Ij
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 2200mg/l. The sample was designated as SMZ-11. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table 1.
Example Ik
The same procedure was repeated as described in example 1 except for variation in treatment with surfactant wherein the concentration employed was 2500mg/l. The sample was designated as SMZ-12. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example - 2
Zeolite A was washed with distilled water several times till pH of the filtrate is 10.0 to 10.5. lOg of washed zeolite A sample was then mixed with quaternary ammonium compounds (QAC) solution in 1:100 (solid: liquid) ratio. The QAC concentration was 100 mg/1. The solution was agitated for 7 to 8 hr at 150 rpm on gyratory shaker at pH 8.0 to 8.5. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 6 hr. The sample was designated as SMZ-13. The SMZ-A sample synthesized as such was then mechanically ground with a mortar and pestle to fine particle size. The powdered SMZ-A was used for adsorption of arsenic .The efficiency of sample is illustrated in Table 2.
(Table Removed)

Example 2a
The same procedure Was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 200mg/l. The sample was designated as SMZ-14. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in.
Example 2b
The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 300mg/l. The sample was designated as SMZ-15. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example 2c
The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 500mg/l. The sample was designated as SMZ-16. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example 2d
The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 800mg/l. The sample was designated as SMZ-17. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table2.
Example 2e
The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 1000mg/l. The sample was designated as SMZ-18. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example 2f
The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 1200mg/l. The sample was designated as
SMZ-19. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in Table2.
Example 2g
The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 1500mg/l. The sample was designated as SMZ-20. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example 2h
The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 1800mg/l. The sample was designated as SMZ-21. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example 2i
The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 2000mg/l. The sample was designated as SMZ-22. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example 2j
The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 2200mg/I. The sample was designated as SMZ-23. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example 2k
The same procedure was repeated as described in example 2 except for variation in treatment with QAC wherein the concentration employed was 2500mg/l. The sample was designated as SMZ-24. The powdered SMZ-A was used for adsorption of arsenic. The efficiency of sample is illustrated in
Example 3
The same procedure was repeated as described in example 1 for preparation of SMZ-A-5. The as-synthesized SMZ-A-5 was then used for removal of arsenic at initial concentration of 5.0 mg/1. The results are detailed

(Table Removed)
Example 3b
The same procedure was repeated as described in example 3 except for the initial concentration of arsenic solution wherein the concentration employed was 25 mg/1. The results are detailed
(Table Removed)

Example 4
The same procedure was repeated as described in example 1 for preparation of SMZ-A-5. The as-synthesised SMZ-A-5 was then used for removal of chromate at initial concentration of 5.0 mg/1. The results are detailed in Table 4
(Table Removed)
.
Example 4a
The same procedure was repeated as described in example 4 except for initial concentration of arsenic solution wherein the concentration employed was 10 mg/1. The results are detailed in Table 4a.

(Table Removed)
Example 4b
The same procedure was repeated described as in example 4 except for initial concentration of arsenic solution wherein the concentration employed was 25 mg/1. The results are detailed in
Table 4b.
(Table Removed)

Example 5
The same procedure was repeated as described in example 1 for preparation of SMZ wherein commercial zeolite-A was treated with surfactant concentration of 200 mg/1. The as-synthesized sample was further treated with 0.2 M solution of FeSC>4 to obtain the surfactant and metal treated SMZ designated as SMZ-A-25. The as-synthesized samples were used to study the removal of arsenic at fixed initial concentration of 1 mg/1. The results are detailed in
(Table Removed)

Example 5a
The same procedure was repeated as described in example 5 except for variation in treatment with surfactant wherein the concentration employed was 1000mg/l. The sample was designated as SMZ-A-26. The as-synthesised sample was used for adsorption of arsenic. The efficiencies of samples are illustrated in Table 5.
Example 5b
The same procedure was repeated as described in example 5 except for variation in treatment with surfactant wherein the concentration employed was 2000mg/l. The sample was designated as SMZ-A-27. The as synthesised sample was used for adsorption of arsenic. The efficiencies of samples are illustrated in Table 5.
Example 6
The same procedure was repeated as described in example 1 for preparation of SMZ wherein commercial zeolite-A was treated with surfactant concentration of 200 mg/1. The as-synthesized sample was further treated with 0.2 M solution of FeSC>4 to obtain the surfactant and metal treated SMZ designated as SMZ-A-28. The as-synthesized samples were used to study the removal of arsenic at fixed initial concentration of 1 mg/1. The results are detailed in Table 6.
(Table Removed)

N.D.: Non Detectable
* Initial surfactant concentration used for treatment
** Initial metal concentration used for treatment
Example 6a
The same procedure was repeated as described in example 6 except for variation in treatment with surfactant wherein the concentration employed was 1000mg/l. The sample was designated as SMZ-A-29. The as-synthesised sample was used for adsorption of arsenic. The efficiencies of samples are illustrated in Table 6.
Example 6b
The same procedure was repeated as described in example 6 except for variation in treatment with surfactant wherein the concentration employed was 2000mg/l. The sample was designated as SMZ-A-30. The as-synthesised sample was used for adsorption of arsenic. The efficiencies of samples are illustrated in Table 6.
(Table Removed)

Example 7
Zeolite-A was washed with distilled water several times till its filtrate pH reaches to 10.0 to 10.5. lOg of washed zeolite A sample was then mixed with 0.2 M solution of ferrous sulphate. The solution was agitated for 7 to 8 hr at 150 rpm on shaker. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 6 hr. The iron treated zeolite samples as synthesized was given the same treatment as detailed in example 1 to obtain the metal and surfactant treated SMZ designated as SMZ-A-31. SMZ-A-32 and SMZ-A-33 were synthesised by treating iron zeolite-A with surfactant concentrations of 1000 mg/1 and 2000mg/l. The as-synthesized samples were used to study the removal of arsenic at fixed initial concentration of 1 mg/1. The results are detailed in Table 7.
N.D.: Non Detectable
* Initial surfactant concentration used for treatment
** Initial metal concentration used for treatment
Example 8
The same procedure was repeated as described in example 7 except for treatment with tetrabutyl ammonium hydroxide (TBAOH) as surface modifiers. The TBAOH concentration used was 200 mg/1 and the sample was designated as SMZ-A-34. SMZ-A-35 and SMZ-A-36 were synthesized by treating zeolite-A with TBAOH concentration of 1000 mg/1 and 2000 mg/1. The as-synthesised samples were used for adsorption of arsenic. The efficiencies of samples are illustrated in Table 8.
(Table Removed)

N.D.: Non Detectable
* Initial surfactant concentration used for treatment
** Initial metal concentration used for treatment
Example 9
Zeolite-A was washed with distilled water several times till its filtrate pH reaches to 10.0 to 10.5. Ig of washed zeolite A sample was then mixed with an alcoholic solution of 2,3-dimercapto-1-propanesulphonic acid (DMSA). The concentration of DMSA used was 3000 mg/1. The solution was agitated for 4 to 5 hr at 150 rpm on shaker. The solution was then filtered and the solid residue was washed with double distilled water and air dried for 6 hrs. The sample synthesized as such was then mechanically ground with a mortar and pestle to fine particle size. The sample was designated as SMZ-A-37. SMZ-A-38 and SMZ-A-39 were synthesized by treating zeolite-A with DMSA concentration of 6000 mg/1 and 9000 mg/1. The as-synthesised samples were used for adsorption of arsenic .The efficiencies of samples are illustrated in Table 9.
(Table Removed)

Example 10
The same procedure was repeated as described in example 12 except for the ligand wherein the DMSA was replaced with 2,3-dimercapto-l-propanol (DMPA). The sample was
25

designated as SMZ-A-40. SMZ-A-41 and SMZ-A-42 were synthesized by treating zeolite-A with DMPA concentration of 6000 mg/1 and 9000 mg/1. The as synthesised samples were used for adsorption of arsenic .The efficiencies of samples are illustrated in Table 10.
(Table Removed)

Advantages;
The main advantages of the present invention are:
Offers selectivity over conventional adsorbents for arsenic at low concentrations
Offers versatility over conventional adsorbents for sorption of wide range of pollutants
ranging from cationic to anionic
High adsorption capacity over conventional adsorbents
Possible frequent regeneration and disposal by virtue of its conversion to value added
ceramic precursors by heat treatment
Stabilization/immobilisation of arsenic in SMZ at higher temperature.
Offers cost effectiveness over other adsorbents by offering single unit for wide array
of pollutants/chemical species vis-a-vis multiple units required for targeting wide
array of pollutants/chemical species.
No problem of sludge generation which are generally associated with conventional
chemical methods viz. alum treatment, chemical precipitation etc.
No problem of hazardous chemical handling etc. by providing technically non-tedious
and clean process.

1. Surface modified zeolites comprising:
a) zeolite selected from the group of zeolite A, zeolite X, flyash based zeolite, faujasitic
zeolite of Y type
b) modifier selected from the group of surfactant, surface modifier, metal chelating ligand
c) iron in the ferrous state ( ~ e ~ + )
in the ratio that ranges from 1 : 0.003 : 0.25 to 1 : 0.045 : 25 respectively.
2. Surface modified zeolite as claimed in claim 1, wherein the said surfactant is selected
from the group of hexamdecyltrimethyl ammonium bromide (HDTMA-Br), sodium
lauryl sulphate.
3. Surface modified zeolite as claimed in claim 1, wherein the said surface modifier is
selected from the group of tetrapropoylammonium bromide (TPA-Br),
tetramethylammonium bromide (TBA-Br), tetramethylammonium bromide (TMA-Br).
4. Surface modified zeolite as claimed in claim 1, wherein one of the modifier of metal
chelating ligands is selected from the group of dimercaptosuccinic acid (DMSA),
dimercaptopropionic acid.
5. Surface modified zeolites as claimed in claim 1 is useful for removal of toxic elements
chromate and arsenate from water

Documents:

646-del-2006-Abstract-(31-10-2012).pdf

646-del-2006-abstract.pdf

646-del-2006-Claims-(31-10-2012).pdf

646-del-2006-claims.pdf

646-del-2006-correspondence-others 1.pdf

646-del-2006-Correspondence-Others-(19-10-2012).pdf

646-del-2006-Correspondence-Others-(31-10-2012).pdf

646-del-2006-correspondence-others.pdf

646-del-2006-description(complete).pdf

646-del-2006-form-1.pdf

646-del-2006-form-18.pdf

646-del-2006-form-2.pdf

646-del-2006-Form-3-(19-10-2012).pdf

646-del-2006-form-3.pdf

646-del-2006-form-5.pdf

646-del-2006-Petition-137-(19-10-2012).pdf

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Patent Number

256699

Indian Patent Application Number

646/DEL/2006

PG Journal Number

29/2013

Publication Date

19-Jul-2013

Grant Date

18-Jul-2013

Date of Filing

10-Mar-2006

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	RISHI NARAYAN SINGH	National Environmental Engineering Research Institute, NEERI, Nehru Marg Nagpur-20
2	NA	NA
3	SIDDHARTH ULHAS MESHRAM	National Environmental Engineering Research Institute, NEERI, Nehru Marg Nagpur-20
4	AMIT KUMAR BANSIWAL	National Environmental Engineering Research Institute, NEERI, Nehru Marg Nagpur-20
5	NITIN KUMAR LABHSETWAR	National Environmental Engineering Research Institute, NEERI, Nehru Marg Nagpur-20
6	SUKUMAR DEVOTTA	National Environmental Engineering Research Institute, NEERI, Nehru Marg Nagpur-20
7	SADHANA SURESH RAYALU	National Environmental Engineering Research Institute, NEERI, Nehru Marg Nagpur-20
8	PAWAN KUMAR	National Environmental Engineering Research Institute, NEERI, Nehru Marg Nagpur-20

PCT International Classification Number

B01J 29/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA