Title of Invention

"A CROSSLINKED GALACTOMANNAN POLYSACCHARIDE RESIN AND PROCESS FOR PREPARING THE SAME."

Abstract

The present invention relates to a crosslinked galactomannan polysaccharide resin and process for the preparation of said crosslinked galactomannan polysaccharide resin with 0.1 to 1 degree of crosslinking for the removal of toxic metal ions from water. The process includes the following steps of preparing a slurry of the galactaomannan polysaccharide with a solvent; adding an alkali to said slurry to obtain an alkaline solution; heating and stirring the alkaline solution in step (ii) at 35-50°C; and treating the alkaline solution in step (iii) with epichlorohydrin with continuous stirring for 4-5 hours at 35-50°C to obtain the resin.

Full Text

FIELD OF INVENTION The present invention relates to the development of a crosslinked polysaccharide resin for the removal of toxic metal ions from water. BACKGROUND OF INVENTION Water is contaminated with a number of toxic metal ions like ions of copper , chromium, iron, arsenic, cadmium etc. Various technologies have been developed for the removal of these ions. In the seven districts of Bengal concentration of arsenic in well water is quite high (0.2 - 3.7mg/l). In water, the most common valence states of arsenic are As(V), or arsenate, which is more prevalent in aerobic surface waters and As(lll), or arsenite, which is more likely to occur in anaerobic ground waters. In the pH range of 4 to 10, the predominant As (III) compound is neutral in charge, while the As (V) species are negatively charged. Removal efficiencies for As(lll) are poor compared to removal of As(V) by any of the technologies evaluated so far due to the negative charge. The prior technologies perform most effectively when treating arsenic in the form of As(V). As (III) may be converted through pre-oxidation to As(V). Data on oxidants indicate that chlorine, ferric chloride, and potassium permanganate are effective in oxidizing As(lll) to As(V). Pre-oxidation with chlorine may create undesirable concentrations of disinfection by-products. Ozone and hydrogen peroxide should oxidize As(lll) to As(V), but no data are available on performance. The following technologies have been evaluated for the removal of arsenic from water so far. Coagulation/Filtration is an effective treatment process for removal of As(V) according to laboratory and pilot-plant tests. The type of coagulant and dosage used affects the efficiency of the process. Within either high or low pH ranges, the efficiency of Coagulation/Filtration is significantly reduced. Alum performance is slightly lower than ferric sulfate. Other coagulants were also less effective than ferric sulfate. However, said process has certain drawbacks. Regeneration of alum or ferric sulfate after coagulation of As is not possible. Disposal of the arsenic-contaminated coagulation sludge is of high concern especially if nearby landfills are unwilling to accept such a sludge. Lime Softening operated within the optimum pH range of greater than 10.5 is likely to provide a high percentage of As removal for influent concentrations of 50 µg/L. However, lime softening has certain drawbacks. It is difficult to reduce As from influent concentrations of 50 ug/L consistently to 1 ug/L by lime softening alone. Systems using lime softening may require secondary treatment to meet that goal. Other drawbacks of Coagulation/Filtration and Lime Softening processes are • Not appropriate for most small systems--high cost, need well trained operators, and variability in process performance • Coagulation/Filtration & lime softening alone may have difficulty in consistently meeting a low-level Minimum concentration limit. Ion Exchange may be useful as a polishing step. Disposal of sludge may be a problem Activated Alumina is effective in treating water with high total dissolved solids. However, selenium, fluoride, chloride, and sulfate, if present at high levels, may compete for adsorption sites. AA is highly selective towards As(V). However, said process has certain drawbacks. Its strong attraction to As (v) results in regeneration problems, possibly resulting in 5 to 10 percent loss of adsorptive capacity for each run. Other drawbacks are • Lack of availability of F-1 alumina. Testing of substitute not yielding same results. • Chemical handling requirements may make this process too complex and dangerous for many small systems • Activated Alumina may not be efficient in the long term, as it seems to lose significant adsorptive capacity with each regeneration cycle Highly concentrated waste streams-disposal of brine may be a problem Ion Exchange can effectively remove arsenic. However, sulfate, total dissolved solids, selenium, fluoride, and nitrate compete with arsenic and can affect run length. Passage through a series of columns could improve removal and decrease regeneration frequency. Suspended solids and precipitated iron can cause clogging of the Ion Exchange bed. Systems containing high levels of these constituents may require pretreatment. However, ion exchange method has certain drawbacks. Suspended solids and precipitated iron can cause clogging of the Ion Exchange bed. Systems containing high levels of these constituents may require pretreatment. Highly concentrated waste by-product stream- disposal of brine may be a problem. Brine recycling might reduce the impact. Sulfate levels affect run length Reverse Osmosis provided removal efficiencies of greater than 95 percent when operating pressure is at ideal psi. If Reverse Osmosis is used by small systems, 60% water recovery will lead to an increased need for raw water. The water recovery is the volume of water produced by the process divided by the influent stream (product water/influent stream). Electrodialysis Reversal is expected to achieve removal efficiencies of 80 percent. One study demonstrated arsenic removal to 3 ug/L from an influent concentration of 21 ug/L. Nanoflit ration was capable of arsenic removals of over 90%. The recoveries ranged between 15 to 20%. A recent study showed that the removal efficiency dropped significantly during pilot-scale tests where the process was operated at more realistic recoveries. However, reverse osmosis, electrodialysis reversal and nanofiltration have certain drawbacks. Discharge of reject water or brine (about 20-25 percent of influent) is of high concern in water-scarce regions. The increased water recovery can lead to increased costs for arsenic removal. Extensive corrosion control could be required. OBJECT OF THE INVENTION The main object of the present invention is to provide a process for the preparation of a crosslinked polysaccharide resin for the removal of toxic metal ions. Another object of the present invention is to provide a crosslinked polysaccharide resin which is a low cost edible product. Still another object of the present invention is to provide a crosslinked polysaccharide resin which can remove both forms of arsenic i.e. the As(V), or arsenate, which is more prevalent in aerobic surface waters and As(lll), or arsenite, which is more likely to occur in anaerobic ground waters. Further objective of the present invention is to provide the crosslinked polysaccharide resin in bead form. SUMMARY OF THE INVENTION In order to achieve the said objective the present invention provides for a process for the preparation of a crosslinked galactomannan polysaccharide resin with 0.1 to 1 degree of crosslinking for the removal of toxic metal ions from water comprising of the following steps : • preparing a slurry of the galactaomannan polysaccharide with a solvent. • adding an alkali to said slurry to obtain an alkaline solution. • heating and stirring the alkaline solution in step (ii) at 35-50°C. • treating the alkaline solution in step (iii) with epichlorohydrin with continuous stirring for 4-5 hours at 35-50°C to obtain the resin. This invention further relates to a crosslinked galactomannan polysaccharide resin for removal of toxic metal ions from water whenever prepared by said process. DESCRIPTION OF THE INVENTION A crosslinked polysaccharide resin can be used to remove toxic metal ions from water. This resin can remove both forms of arsenic i.e. the As(V), or arsenate, which is more prevalent in aerobic surface waters and As(lll), or arsenite, which is more likely to occur in anaerobic ground waters. Process for preparation of the Arsenic selective Cross linked Polysaccharide Resin: The resin has been synthesized by cross-linking derivatization of guar gum which is a biodegradable edible polysaccharide powder having 3000-4000 cps viscosity for its 1% aqueous solution. For this purpose 0.1 to 1 degree of cross-linking of guar gum was done. One mole of guar gum, 486 g were taken in a round bottom flask and slurried with 100 ml dioxane. 20 ml of 50% aqueous solution of NaOH was added to it. Then the mixture was stirred at 45° C on a magnetic stirrer. Five more such alkaline guar gum solutions were prepared. These solutions were then reacted with 9.253 g ( 0.1 mole), 18.506 g ( 0.2 mole), 37.012 g ( 0.4 mole), 46.265 g ( 0.5 mole) and 92.53 g ( 1 mole) of epichlorohydrin with continuous stirring at 45° C. After 4 hrs of stirring, the compounds were filtered and washed with HCl-methanol, methanol and then dried. These white- yellowish powders were insoluble in water. Their FTIR spectral characterization was done which showed the presence of cis-hydroxyl groups. Similarly 500 g of guar gum seeds were made alkaline with 20 ml of 50% aqueous solution of NaOH. Then the mixture was stirred at 45° C on a magnetic stirrer. Five more such alkaline guar gum beads mixtures were prepared. These mixtures were then reacted with 9.253 g ( 0.1 mole), 18.506 g ( 0.2 mole), 37.012 g ( 0.4 mole), 46.265 g ( 0.5 mole) and 92.53 g ( 1 mole) of epichlorohydrin with continuous stirring at 45° C. After 4 hrs of stirring, the cross-linked beads were filtered and washed with HCl-methanol, methanol and then dried. These white- yellowish beads were insoluble in water. The FTIR spectra of the powders of these beads showed the presence of cis-hydroxyl groups in the matrix. EXAMPLE Preparation of As containing solution and its analysis 1 g of As2O3 was dissolved in a 2 ml of 10% aqueous NaOH solution and made up to 250 ml with distilled water in graduated flask. 25 ml of this solution were taken in a flask, 25 ml distilled water, 50 ml of 12 N hydrochloric acid and 5 ml of chloroform were added to it. The solution was then cooled and was titrated against 0.025 M KI03 solution. The purple colour of the solution turning into very pale yellow colour due to formation of end product I Cl. This titration showed that presence of As(lll) in the solution was 350 mg per 1000 ml of the solution. Treatment of As containing solution with the crosslinked galactomannan polysaccharide 100 ml solution of arsenic (35 mg As in 100 ml water) was treated with 1g of the crosslinked galactomannan (guar gum) polysaccharide. The mixture was mixed and filtered. In the filtrate As(lll) content was analysed titrimetrically, it showed the concentration of Arsenic to be less than 1 microgram per litre. Similarly we tested the removal of arsenate from the 350 mg/l water and it was observed that As content in the solution was 1-1.2 microgram per litre. The bead form of the resin was also tested for removal of arsenic from water that also reduces the concentration of arsenic below 1 microgram per liter by 2 g of the beads. ADVANTAGES OF THE CROSSLINKED GALACTOMANNAN POLYSACCHARtDE RESIN The advantages of the crosslinked galactomannan polysaccharide resin are as follows: 1. The resin is very much suitable for removal of arsenite and arsenate from the open sources as well as the well waters of the arsenic affected areas. 2. It reduces the As(lll) and As (V) concentration in Treated Water to below 1µg /L, which is within the WHO limit of potable water. 3. It can remove Arsenite and arsenate (As V) both forms of As from water. 4. In the bead form it can be used in columns for removal of arsenic on smaller scale. 5. It is not affected by other ions present in water. 6. It does not require any oxidants like chlorine, ferric chloride, or potassium permanganate for oxidizing As(iii) to As(V). So it does not create undesirable concentrations of disinfection by-products. 7. The resin can be regenerated by washing with very dilute 0.1 - 2 N Hydrochloric acid in a column. 8. Disposal of this regenerated and free from arsenic resin is also very easy by mixing it in road building material. The regeneration of other reported materials for removal of arsenic is not possible. The arsenic could be removed from the new polysaccharide based resin and the generated solution can be reused for chemical purpose. Resin is also cheaper than the Alumina and lime coagulation processes. It could be regenerated and reused more than 20 times; finally it can be disposed off by mixing in Road construction material or by biodegradation also. Therefore, the sludge disposal, regeneration and the final disposal of the crosslinked galactomannan polysaccharide resin is easy, which is not possible with other as removal systems. I Claim: 1. A process for the preparation of a crosslinked galactomannan polysaccharide resin with 0.1 to 1 degree of crosslinking for the removal of toxic metal ions from water comprising of the following steps : i. preparing a slurry of the galactaomannan polysaccharide with a solvent, ii. adding an alkali to said slurry to obtain an alkaline solution, iii. heating and stirring the alkaline solution in step (ii) at 35- 50°C. iv. treating the alkaline solution in step (iii) with epichlorohydrin with continuous stirring for 4-5 hours at 35-50°C to obtain the resin. 2. The process as claimed in claim 1, wherein said solvent is water or an organic solvent. 3. The process as claimed in claim 2, wherein the organic solvent is dioxane or tetrahydrofuran. 4. The process as claimed in claim 1, wherein the alkali is sodium or potassium hydroxide. 5. A crosslinked galactomannan polysaccharide resin for removal of toxic metal ions from water whenever prepared by the process claimed in claim 1. 6. A crosslinked galactomannan polysaccharide resin as claimed in claim 5, wherein the resin can be regenerated by washing with 0.1 - 0.2N hydrochloric acid. 7. A crosslinked galactomannan polysaccharide resin as claimed in claim 5, wherein the resin is in the bead form. 8. The resin as claimed in claim 5, wherein the crosslinked galactomannan polysaccharide is guargum.

Documents:

387-DEL-2008-Abstract-(29-05-2012).pdf

387-DEL-2008-Claims-(01-08-2012).pdf

387-del-2008-claims.pdf

387-DEL-2008-Correspondence Others-(01-08-2012).pdf

387-DEL-2008-Correspondence Others-(24-08-2011).pdf

387-DEL-2008-Correspondence Others-(29-05-2012).pdf

387-del-2008-correspondence-others.pdf

387-del-2008-description (complete).pdf

387-DEL-2008-Form-1-(29-05-2012).pdf

387-del-2008-form-1.pdf

387-DEL-2008-Form-18 (22-02-2008).pdf

387-del-2008-form-2.pdf

387-del-2008-form-3.pdf

387-DEL-2008-GPA-(24-08-2011).pdf