Title of Invention

"METHOD OF PREPARING NANOCRYSTALLINE MGO AND ZNO PRODUCTS AND USING SAME FOR REMOVING FLUORIDE AND ARSENIC FROM CONTAMINATED WATER"

Abstract The present invention relates to a method for producing surface activated porous nanocrystalline magnesium oxide and zinc oxide products for removal of fluoride and arsenic species from drinking water/ground water/aqueous medium comprising developing a synthetic reaction under combustion process for preparing magnesium oxide and zinc oxide products having large surface area from their respective metal nitrates as oxidizer and glycine as a fuel; and selection and employing of combustion derived nanocrystalline magnesium oxide and zinc oxide products as adsorbents for removing fluoride and As(III) and As(V) from drinking water/ground water/aqueous medium. The present invention further relates to a method a method for producing surface activated porous nanocrystalline magnesium oxide and zinc oxide products for removal of fluoride and arsenic species from drinking water/ground water/aqueous medium wherein said method involves removal of fluoride and arsenic species having various valence states from fluoride and arsenic contaminated drinking water/ground water/aqueous medium comprising the steps of removing of fluoride from said water using magnesium oxide as adsorbent; and removing of arsenic species from said water using magnesium oxide and zinc oxide as adsorbents.
Full Text FIELD OF INVENTION
The present invention generally in general relates to the establishment /development of a simple, novel, low cost and scaled up synthetic reaction in short time under combustion process.
Particularly the present invention relates to the synthesis of surface activated nanocrystalline magnesium oxide and zinc oxide products.
More particularly, the present invention relates to the selection of materials and removing fluoride and As(III) and As(V) from contaminated waters using magnesium oxide and zinc oxide products as adsorbents.
DESCRIPTION OF RELATED ART
The US patent No 7,138,063 granted to Teter, et al. on November 21, 2006 wherein it is stated that about an improved water decontamination process comprising contacting water containing anionic.contaminants with an enhanced coagulant to form an enhanced floe, which more efficiently binds anionic species (e.g., arsenate, arsenite, chromate, fluoride, selenate, and borate, and combinations thereof) predominantly through the formation of surface complexes. The enhanced coagulant comprises a trivalent metal cation coagulant (e.g., ferric chloride or aluminum sulfate) mixed with a divalent metal cation modifier (e.g., copper sulfate or zinc sulfate). This process as disclosed and granted is different from the process of our invention as the invention of the present inventors depends on the totally new concept that is preparation and use of nanoparticles of certain metallic oxides for removal or control of the contaminants in the contaminated water or water based solutions.
In another US patent 7,014,771 granted to Bandyopadhyay, et al. on March 21, 2006 wherein the invention relates to a process for the preparation of arsenic free water and an apparatus therefor. The present invention also relates to a porous ceramic useful for pressure filtration in order to produce arsenic free water. The present invention particularly relates to a process for preparing arsenic free ( apparatus therefor. This process is also expensive like the one disclosed in the US patent No 7,138,063 whereas the invention as disclosed herein is cost effective.
In the US patent 6,863,825 which was granted to Witham, et al. on March 8, 2005 wherein the said process teaches the removal of Arsenic from water and other aqueous feeds by (1) treating the feed with a compound containing cerium in the +4 oxidation state, preferably cerium dioxide, to oxidize arsenic in the +3 oxidation state to arsenic in the +5 oxidation state and (2) removing the arsenic in the +5 oxidation state from the aqueous phase, normally by contacting the treated feed with alumina or other precipitating agent containing cations in the +3 oxidation state.
No prior art teaches the simultaneous removal of fluoride and arsenic and arsenic in +3 and +5 state from the contaminated waters. It is the first time by the inventors who invented the concept of using nanoparticles of Mg and Zn Oxides for the effective removal of the above said contaminants in an effective manner by a simple and cost effective method that is by adsorption.
Nanoparticles of known substances observed to behave in an unexpected way and some times the results achieved by the said nanoparticles are surprising and amazing and non-obvious. It was not expected by the present inventors that MgO and ZnO nanoparticles probably in crystalline form can be used for the removal of contaminants such as fluoride and arsenic.
I. Fluoride contamination in ground /drinking water
To certain extent (0.6 ppm, as per the WHO) fluoride ingestion is necessary for bone and teeth developments, but excessive ingestion causes a disease known as fluorosis. This has been observed in persons when water contains more than 3-6 mg/L of fluoride. Skeletal fluorosis affects young and old alike. Fluoride can also damage the foetus- if the mother consumes water and food, with a high concentration of fluoride during pregnancy/breast feeding, infant mortality due to calcification of blood vessels can also occur. The fluorosis is often over looked because of the misconception prevailing that fluoride will only affect bone and teeth. Fluoride, when consumed in excess can cause several ailments besides skeletal and dental fluorosis [1]. The WHO standards [2] and BIS: 10500 1983[3] permit only 1,5 mg/L as a safe limit of fluoride in drinking water for human consumption. Fluorosis continues to be an
endemic problem and more and more areas are being discovered regularly that are affected by fluorosis in different parts of the world. Excess fluoride in ground water has been encounted in Pakistan, Bangladesh, Argentina, United States of America, Morocco, Middle East countries, Japan, South African countries, New Zealand, Thailand, China, Sri Lanka, Spain, Holland, Italy and Mexico [4].
The problem of fluorosis has reached an alarming stage. In India, as many as 200 districts spread across 17 states are suffering from high fluoride concentration. A population of some 25 million has been affected and approximately 66 million people are described as population at risk [5]. The most affected areas in India as reported [1.4] are:
(a) 50-100 % districts in Andhra Pradesh, Tamilnadu, Uttar Pradesh, Gujarat and Rajasthan.
(b) 30-50 % districts in Bihar, Haryana, Karnataka, Maharashtra, Madhya Pradesh, Punjab,
Orissa and West Bengal.
(c) Fluoride exists fairly abundantly in the earth's crust and can enter ground water by natural process like weathering and leaching of bedrock. The minerals / rocks rich in fluoride are flurospar Cap2 (sedimentary rock, lime stones and sand stones), cryolite NasAlFPOe (igneous, granite) and fluorapatite Ca$ (PO) 2Ca(FCl) 2- Water is a major source of fluoride intake. High profile of fluoride in ground water is observed in 4.6 % of geographical area (8900 km2) of Karnataka. The incidence of very high levels of fluoride contamination in the districts has occurred in the eastern and southern belts covering the districts of Gulburga, Raichur, Bellary, Chitradurga, Tumkur and Kolar and are scattered in rest of Karnataka. The reported concentration range of fluoride in ground water is 1.55 -7.4 ppm [4].
Defluoridation of water has been carried out using various methods like coagulation and precipitation process[6] (named as Nalgonda technique), use of locally derived sample of silty clay[7], natural materials,[8] soil sorbent[9] and oxide minerals[10,ll]. The removal of excessive fluoride (F~) from drinking water was also attempted using ion exchange/adsorption process in which commercially available metal oxides like activated alumina, magnesia and other materials were used [1,3,]
All these above reported methods are expensive, pH dependent and creates large waste stream. There is an urgent need to develop a low-cost method and/or device for the purpose of reducing fluoride content in the supply of potable water in problematic areas.
The present defluoridation process can also removes other predominant ions in water such as chlorides and nitrates. For instance, it is observed that the nitrate content along with fluoride in bore well water samples decreased from 6 to 44%.
II. Arsenic contamination in ground/drinking water
Arsenic, the world's most hazardous chemical [1], is found to exist within the shallow zones of groundwater of many countries like Argentina, Bangladesh, India, Pakistan, Mexico, Mongolia, Germany, Thailand, China, Chile, USA, Canada, Hungary, Romania, Vietnam, Nepal, Myanmar, Cambodia, etc. in various concentrations [2-3]. In some places in Bangladesh its concentration is as high as lOOO^g/L [4]. Considering the lethal impact of arsenic on human health, environmental authorities have taken a more stringent attitude towards the presence of arsenic in water. World Health Organization (WHO) in 1993 and National Health and Medical Research Committee (NHMRC), Australia, in 1996 had recommended maximum contaminant level (MCL) of arsenic in drinking water as 10 and 7 (j.g/L respectively [5,6]. European Commission has also reduced the MCL of arsenic in drinking water from 50 to 10ng/L in 2003 [7]. Environmental Protection Agency (EPA), USA, has decided to move forward in implementing the same MCL of arsenic that is recommended by WHO for drinking water in 1993 [8]. Japan and Canada has reduced the MCL for arsenic in drinking water to 10 and 25 u£/L, respectively. The MCL for arsenic in countries like India, Bangladesh, Taiwan, China, Vietnam, etc. is also 50 jag/L [9].
Water is one of the most important media through which arsenic enters into the human body. As the diagnosis and medication of the arsenic related diseases are difficult the treatment of contaminated water as a preventive measure appears to be an effective alternative to combat arsenic poisoning. Arsenic may be available in water in variable oxidation states (+5, +3, 0,-3) [10-11]. From contaminated water it can be converted into insoluble compounds and can be co-precipitated with the hydro oxides of Fe and Mn in aqueous medium under certain conditions [12-15]. Like other heavy metals it may also be adsorbed by suitable adsorbent.
Arsenic can be removed from contaminated water by physico-chemical as well as biological techniques. These techniques are classified as below:
I. Physico-chemical techniques
(a) Adsorption
(b) Ion exchange
(c) Precipitation-coagulation
(d) Membrane filtration
(e) Permeable reactive methods
II. Biological techniques
(a) Phytoremediation
(b) Biological treatment with living microbes/bio-filtration
The modes of contamination of water by arsenic, arsenic metabolism and its poisoning effects, severity of the arsenic poisoning around the world, and the efforts to solve this problem by conventional laboratory based technology and search for new upgraded technology are discussed below.
Arsenic problem in groundwater in West Bengal was first recognized [16] in the late 1980s and the health effects are now reasonably well documented. More recently, the scale of the problem in other states with similar geology like Assam, Bihar, Uttar Pradesh, Tripura, Manipur, Arunachal Pradesh and Nagaland, has also been reported [16]. The affected aquifers of the region are mainly Holocene alluvial and deltaic sediments, similar to those in large parts of Bangladesh. Geologically, the Bengal basin is in intense neotectonic activity[22] and its west, north and east are bordered by the Indian Shield, Shillong Plateau and Naga-Lusai erogenic belt respectively. Recent estimates suggest that elevated concentrations of As exist in groundwater of nine districts of West Bengal, namely Murshidabad, Malda, Nadia, North 24 Parganas, South 24 Parganas, Bardhaman, Howrah, Hoogly and Kolkata. Nearly 50 million people living in 3200 villages in nine of the total 18 districts of West Bengal, covering 38,865 km2, are exposed to drinking water, containing As
above 50 mg/L Rice and vegetable fields irrigated by groundwater receive a large amount of arsenic through shallow tube-wells in the affected areas of North 24-Parganas and Murshidabad, West Bengal Elevated concentrations of As have been reported from Ganges-Gaghra Plain, Ballia district, eastern Uttar Pradesh Bhojpur, Buxar and Shahebganj districts, Bihar and Jharkhand situated on the western banks of the Ganges [16]. In Northeastern India, arsenic has been detected in 21 of the total 24 districts of Assam and three districts in Tripura, six in Arunachal Pradesh, one in Manipur and two in Nagaland [17].
Based on USEPA, the currently best available technologies for As(V) removal are summarized as follows along with their disadvantages listed in parenthesis: Ion exchange resins (sulfate concentration has to be SUMMARY OF THE INVENTION
It is the primary objective of the proposed invention to Development of novel, simple, safe, clean and low cost technique which can easily be implemented at household level.
It is an object of the present invention to provide synthetically formed nanostructured metal-oxides.
A further object of the invention is to make nanostructured metal-oxides in an open container and at atmospheric temperature.
Another object of the invention is to provide a method for preparing metal-oxide skeletal structures from metal salts.
Another object of the invention is to provide a method of forming metal-oxide nanostructured solid skeletons using solution COMBUSTION PROCESS.
Another object of the invention is to a method of controlling or maintaining the desired limits of certain chemicals present either in elemental form or in ionic form of the contaminated water by adsorbing the said chemicals characterized in that the said adsorption is on the surface of the nanoparticles of metallic oxides preferably the said nanoparticles are prepared afresh or prepared insitu.
Another object of the invention is to provide treated water which meets the WHO and Indian Standards with respect to the allowable or tolerable presence of contaminants in the drinking water.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. The invention involves a method for making nanostructured metal-oxide. The method can be carried out using an open container, such as a beaker, and at atmospheric temperature. The method employs the use of metal salts with solvents, such as water and ethanol, and involves the dissolution of the metal salt in the solvent.
While various embodiments, materials, parameters, etc., along with operation sequences have been described and / or illustrated to exemplify and explain the principles of the invention, such are not intended to be limited. Modifications and changes may become apparent to those skilled in the art, and it is intended that the invention be limited only by the scope of the appended claims.
Nanocrystalline metal oxides are prepared through simple and cost effective combustion route using metal nitrates as oxidizers and amine derivatives as fuel in few minutes. These metal oxides have been characterized using PXRD, SEM, and surface area and porosity measurements. The powder XRD patterns confirm the crystallinity and phase purity of the as made powders. The scanning electron micrograph (SEM) images reveal that the combustion derived powder is porous and agglomerated with fine particles. The particle size of the powders is found to be in the nanoscale with a large surface area. As made Metal oxides are used as adsorbents for the removal of fluoride and Arsenic (III and V) from ground water samples. The experimental parameters such as stirring time, sedimentation time, and dosage quantity and pH variation are optimized. The results reveal that 92 % fluoride and 96 %Arsenic (III and V) could be removed using 0.1 g of nanosized metal oxides from 10 ppm of fluoride and 1000 ppb Arsenic (III and V) synthetic solutions. The metal oxides employed in this technique are low cost, eco-friendly and non-toxic. Comparable with the reported data, in this technique 90 % minimization of sludge could be achieved. The generated sludge can be regenerated and reused as adsorbent. It is value added product and can be used in the pharmaceutical and chemical industries. This simple and novel method can easily be implemented in household level to community water supply schemes in rural India.
The metal oxides obtained through combustion synthesis are in nanosize and having high surface area. These are used as adsorbents in the present investigation which are eco-friendly and non-toxic. Mineral acids are required to adjust the desired limit of pH of the treated water samples. In the present investigation, only two chemicals (adsorbent and mineral acids) are required in the process of removal of fluoride and Arsenic (III and V) present in ground water.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows the schematic representation of combustion synthesis of metal oxides
Figure 2 shows the removal of fluoride and As (III) and As (V) content in standard solutions/synthetic water and in ground water
DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiments of the present invention will now be explained with reference to the accompanying. It should be understood however that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. The following description and drawings are not to be construed as limiting the invention and numerous specific details are described to provide a thorough understanding of the present invention, as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. However in certain instances, well-known or conventional details are not described in order not to unnecessarily obscure the present invention in detail.
Figure 1: Synthesis of MgO and ZnO powders
MgO and ZnO products of nanodimension were prepared by solution combustion process. An aqueous solution containing stoichiometric amount of magnesium or zinc nitrate as oxidizer and glycine as a fuel was taken in a pyrex dish (corresponds to equivalent stoichiometric ratio of oxidizer to fuel (O/F) Oe =1.0). The pyrex dish was introduced into a muffle furnace (Make PSM Instruments, Bangalore) maintained at 400 °C. The redox mixture boiled and formed a white residue. Then burning appeared at one end and propagated throughout the mass within a minute. A fine powder with black colour was obtained. It turned white MgO after allowing it at the same temperature in the muffle furnace for 30 min. In case of ZnO, no need for further heat treatment once it is formed. The theoretical equation assuming complete combustion of redox mixture used for the synthesis of MgO/ZnO may be written as
9M(NO3)2(aq) + 10NH2CH2COOH (aq) -» 9MO (s) +14N2(g) +20CO2 (g) +25H2O (g) (1)
(M = Mg and Zn)
Figure 2: Procedure for removal of fluoride and arsenic (III and V) from the ground water
The calibrated Fluoride ion meter (using standard 5 and 10 ppm of fluoride solution) and Atomic Absorption spectrometer, (using 500 ppb and 1000 ppb of As (III and V) standard solution) were used respectively for the estimation of fluoride and As (III and V) contents
present in synthetic/standard solution, as well as ground water samples. The removal of fluoride and As (III and V) utilizing batch shaking process on magnetic stirrer were performed. In each experiment, 100 mL of synthetic/standard solutions/ ground water containing fluoride and As (III and V) were taken in 250 mL beaker and to this; a known quantity of as-made adsorbents (0.15 g, MgO powder for fluoride and Arsenic and ZnO powder for Arsenic only) were added. In a batch of experiments, the optimum values of variables like pH (the process is independent of pH), stirring time (10 min), and sedimentation time (20 min) were maintained. The fluoride and As (III and V) contents left out in water after the treatment with the adsorbents were measured. The fluoride and As (III and V) adsorbed adsorbents settled at the bottom of the beaker were separated by decantation and it is termed as sludge. This standard procedure was extended for removing fluoride and As (III) and As (V) from drinking water/ground water/aqueous medium with same experimental parameters.
Nanocomposites are multicomponent materials in which at least one of the component phases has one or more dimensions (length, width, or thickness) in the nanometer size range, usually defined as 1 to 100 nm. Energetic nanocomposites are a class of materials that have a fuel component and an oxidizer component intimately mixed in which at least one of the component phases which meets the size definition. In the present invention glycine acts as a fuel and the metallic nitrates acts as oxidizer(s).
The aqueous solution of magnesium nitrate and glycine forms a complex. In low temperature solution combustion process there is a self-sustaining chemical reaction between metal salt and glycine (suitable organic fuel). Hydrated metal salts were chosen as the metal precursors, not only they fundamentals for the method, and fulfill the following requirements.
- Their solubility in water is very high
- The NOs groups being the oxidizing agents.
- Good homogenization can be achieved in the solution
- Few hundreds degrees are enough to melt them
Hence hydrated salts are more favored in this respect, although the water molecules do not affect the total valences of the nitrates and are, therefore relevant for the chemistry of the combustion.
Recent advancements in synthesis procedures, in particular thermal decomposition of appropriate metal complexes M(L)X, has allowed the synthesis of nanoscale materials. In the current study, a similar procedure has been used to prepare metal oxide nanoparticles. The basic idea to reduce the size distribution of nanoparticles in this process is a short burst of nucleation followed by slow controlled growth. This can be achieved by separating the nucleation and growth processes. The dissociation of one or two ligands from the precursors at 300-350 °C is the cause of a short burst of nucleation while the remaining ligands dissociate at around 400 °C (reflux temperature) controlling the growth rate.
Simple and low cost chemicals are used in the present investigation. The adsorbents are eco-friendly and non-toxic. The fluoride and Arsenic (III and V) removal capacity of nanosized metal oxides are very high as compared to the reported methods. It is also observed that the nitrate content along with fluoride in ground well water samples decreased from 6 to 44 %. This simple and novel method can easily be implemented in household level to community water supply schemes in rural India. The generated sludge is a value added product and this can be regenerated and reused as adsorbent. This can be used in the pharmaceutical and chemical industries. There is no wastage of chemicals in the entire process. This is a unique technique in which both Arsenic (III) and Arsenic (V) could be removed simultaneously besides fluoride. This is a scaled up synthesis in environmentally benign. In choosing materials for study, metal oxides are very attractive since they are highly ionic and high melting, and it would be expected that samples of very small particle size might be stable and isolable. Furthermore, reactive surface sites on these oxides have been studied extensively, especially for metal oxide crystals and powders.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that
various changes and modifications are possible and are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.

References cited (Removal of fluoride from ground water)
1. C. R. Nagendra Rao, "Fluoride And Environment- A Review, pp. 386 - 399,
Proceedings of the Third International Conference on Environment and Health "eds.
Martin J. Bunch, V. Madha Suresh and T. Vasantha Kumaran, University of Madras,
Chennai, and Faculty of Environmental Studies, York University. 15-17 December
(2003).
2. WHO, Guidelines for drinking water quality. World Health Organization, Geneva,
P-41, 1993.
3. IS10500 'Indian standard code for drinking water' BIS INDIA. (1983).},
4. RGNDWM, Prevention and Control of Fluorosis in India, Water Quality and
Defluoridation Techniques , Vol.11, Published by Rajiv Gandhi National drinking
Water Mission, Ministry of Rural Development, New Delhi (1993).
5. S. S.Latha, S.RAmbika, and S.J.Prasad, "Fluoride Contamination Status of Ground
Water in Karnataka, Curr, Sci., 730, 34,(1999).
6. WHO-UNICEF Concluded Sponsored Study with Planning Commission
Collaboration /Joint Monitiring Programme, The Times of India ,1-3, 11.8.2004).
7. W. G. Nawlakhe, D. N. Kulkarni, B. N. Pathak and K. R. Bulusu, "Defluoridation of
Water by Nalgonda Technique," Indian J. Environmental Health, 17(1) 26-65
(1975).
8. M. Agarwal, K. Rai, R. Shrivastav and S. Dass, "Defluoridation of Water Using
Amended Clay," J. Cleaner Production, 77,439-44(2003).
9. S. Chidambaram, A. L. Ramanathan and S. Vasudevan, "Fluoride Removal Studies
in Water Using Natural Materials," Water SA, 29 (3) 339 (2003).
10. Yanxin Wang and Eric J. Reardon, "Activation and Regeneration of a Soil Sorbent
for Defluoridation of Drinking Water," Applied Geology, 16, 531-39 (2001).
11. D. Mohapatra, D. Mishra, S. P. Mishra, G. Roy Chaudhury and R. P. Das, "Use of
Oxide Minerals to Abate Fluoride from Water, " /. Colloid and Interface Science,
275, 355-59 (2004).
References cited {Removal of arsenites [As (III)] and arsenates [As (V)] from ground water}
1. Comprehensive Environmental Response, Compensation and Liability Act
(CERCLA), USEPA, 2003.
2. S. Bhattacharjee, S. Chakravarty, S. Maity, V. Dureja, K.K. Gupta,Metal contents in
the ground water of Sahebgunj district, Jharkhand, India, with special reference to
arsenic, Chemosphere 58 (2005) 1203-1217.
3. P.L. Smedley, D.G. Kinniburgh, A review of the source, behaviour and distribution of
arsenic in natural waters, Appl. Geochem. 17 (2002) 517-568.
4. C.F. Harvey, C.H. Swartz, A.B.M. Badruzzaman, N. Keon-Blute, W. Yu, M.A. Ali,
J. Jay, R. Beckie, V. Niedan, D. Brabander, P.M. Gates, K.N. Ashfaque, S. Islam,
H.F. Hemond, M.F. Ahmed, Arsenic mobility and groundwater extraction in
Bangladesh, Science 298 (2002) 1602-1606.
5. WHO, Guidelines for drinking water quality. World Health Organization, Geneva, P-
41, 1993.

6. NHMRC Australian Drinking Water Guidelines. National Health and Medical
Council, Agriculture and Resource Management Council of Australia and New
Zealand, Commonwealth of Australia. PF S93, 1996.
7. European Commission Directive. 98/83/EC, related with drinking water quality
intended for human consumption. Brussels, Belgium, 1998.
8. EPA Office of Ground water and drinking water. Implementation guidance for the
arsenic rule. EPA report-816-D-02-005, Cincinnati, USA, 1998.
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(2002)2143-2145.
10. S. Chakraborty, V. Dureja, G. Bhattacharya, S. Maity, S. Bhattacharjee, Removal of
arsenic from ground water using low cost ferruginous manganese ore, Water Res. 36
(2002) 625-632.
U.S. Mohammad, Arsenic chemistry in soils: an overview of therm odynamic predictions
and field observations, Water Air Soil Poll. 93 (1997) 117-136.
12. I. Katsoyiannis, A. Zouboulis, H. Althof, H. Bartel, Arsenic removal from ground . waters using fixed bed up flow bioreactor, Chemosphere 47 (2002) 325-332.
13. J.G. Hering, P. Chen, J.A. Wilkie, M. Elimelech, S. Liang, Arsenic removal by ferric
chloride, J. AWWA 88 (1996) 155-167.
14. J.G. Hering, P.-Y. Chen, J.A. Wilkie, M. Elimelech, Arsenic removal from drinking
water during coagulation, J. Environ. Eng. 123 (1997) 800-807.
15. L.S. McNeill, M. Edwards, Arsenic removal during precipitative softening,!. Environ.
Eng. 123 (1997) 453-460.
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WE CLAIM
1. A method for producing surface activated porous nanocrystalline magnesium oxide and
zinc oxide products for removal of fluoride and arsenic species from drinking
water/ground water/aqueous medium comprising the steps:
(a) developing a synthetic reaction under combustion process for preparing magnesium
oxide and zinc oxide products having large surface area from their respective metal
nitrates as oxidizer and glycine as a fuel; and
(b) selection and employing of combustion derived nanocrystalline magnesium oxide and
zinc oxide products as adsorbents for removing fluoride and As(III) and As(V) from
drinking water/ground water/aqueous medium.

2. The method of claim 1, wherein said step involves the preparation of magnesium oxide
and zinc oxide products including the step of making aqueous solution by mixing
magnesium nitrate or zinc nitrate as oxidizer and glycerin as a fuel in stoichiometric
ratio.
3. The method of claim 2, wherein said step involves the heating of solution of redox
mixture at temperature of 105 °C to 120 °C.
4. The method of claim 3, wherein said step involves heating the wet mixture at
temperature greater than 200 °C less than 600 °C.
5. The method of claim 4, wherein said heating step is performed so that magnesium
oxide and zinc oxide produced products are nanocrystalline in nature.
6. The method of claim 5, wherein said heating time is maintained in between 15 min to
75 min.
7. The method of claim 2, wherein said nanocrystalline products are voluminous, porous
and agglomerated fine particles, and the magnesium oxide has cubic phase and zinc
oxide has hexagonal phase.
8. The method of claim 7, wherein said products have mean primary crystalline diameter
within the range 10-33 nm.
9. The method of claim 7, wherein said products have a specific surface area of about 107
m2/g and 18.7 m2/g and the pore volume is about 7.8 nm and 6.0 nm.10. The method of claim 1, wherein said method involves removal of fluoride and arsenic
species having various valence states from fluoride and arsenic contaminated drinking
water/ground water/aqueous medium comprising the steps of:
(a) removing of fluoride from said water using magnesium oxide as adsorbent; and
(b) removing of arsenic species from said water using magnesium oxide and zinc
oxide as adsorbents.

11. The method of claim 10, wherein said arsenic contaminated water comprising As (III)
and As(V).
12. The method of claim 10, wherein said removal of fluoride by magnesium oxide and
As(III) and As(V) by both magnesium oxide and zinc oxide through adsorption process.
13. The method of claim 1, wherein said removal technique comprising establishment of
the experimental parameters like stirring time, sedimentation time, adsorbent quantity
and variation of pH for the removal of fluoride and arsenic species from contaminated
water.
14. The method of claim 10, wherein said stirring time, sedimentation time and adsorbent
quantity and pH are well established.
15. The method of claim 10, wherein said resulting water comprises less than 1.2 mg/L of
fluoride and arsenic 10 ug/L (WHO Guidelines for drinking water equality, World
Health Organization, Geneva, 2, 249 (1984), and IS 10500 'Indian standard code for
drinking water' BIS INDIA. (1983).},
16. The method of claim 10, wherein said water is fluoride and arsenic contaminated
drinking water/ground water/aqueous medium
17. The method of claim 10, wherein said generated sludge has regenerated and reused.
18. The method of claim 10, wherein said generated sludge has regenerated by washing
with acid/alkali.
19. The method of claim 10, wherein said generated sludge has regenerated by calcinating
washed sludge at temperature greater than 200 °C less than 600 °C.
20. The method of claim 10, wherein said generated sludge has regenerated sludge was
reused for removal of fluoride at temperature greater than 200 °C less than 600 °C.
21. The method for producing surface activated porous nanocrystalline magnesium oxide
and zinc oxide products for removal of fluoride and arsenic species from drinking
water/ground water/aqueous medium substantially described herein the detailed description.

Documents:


Patent Number 258833
Indian Patent Application Number 261/DEL/2007
PG Journal Number 07/2014
Publication Date 14-Feb-2014
Grant Date 10-Feb-2014
Date of Filing 08-Feb-2007
Name of Patentee DEPARTMENT OF SCIENCE AND TECHNOLOGY
Applicant Address TECHNOLOGY BHAVAN, NEW MEHRAULI ROAD, NEW DELHI, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 CHANDRAPPA GUJJARAHALLI NO. 1716, 6TH MAIN, 2ND STAGE, E BLOCK, RAJAJI NAGAR BANGALORE 560010
2 NAGAPPA BASAPPA NO. 242, 9TH MAIN, PIPE LINE ROAD, VIJAYANAGAR BANGALORE 560040
PCT International Classification Number C02F
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA