Indian Patents. 207190:A FILTER MEDIA FOR REMOVAL OF FLUORIDE ION CONTAMINATION FROM WATER, A DEVICE AND A METHOD FOR PURIFYING FLUORIDE ION CONTAMINATED WATER

Title of Invention	A FILTER MEDIA FOR REMOVAL OF FLUORIDE ION CONTAMINATION FROM WATER, A DEVICE AND A METHOD FOR PURIFYING FLUORIDE ION CONTAMINATED WATER
Abstract	A filter media for removal of fluoride ion contamination from water comprising rice husk ash having aluminium hydroxide coated on the surface thereof.

Full Text	FORM 2 THE PATENTS ACT 1970 (39 of 1970) COMPLETE SPECIFICATION (See Section 10; rule 13) TITLE A filter media for removal of fluoride ion contamination from water, a device and a method for purifying fluoride ion contaminated water APPLICANTS Tata Consultancy Services (a Division of Tata Sons Limited) of Bombay House, Sir Homi Mody Street, Mumbai - 400023, Maharashtra, India, an Indian company INVENTOR Under Section 28(2) "vivek Ganvir, Kalyan Kumar Das and Prakash Chand Kapur, Tata Research Development and Design Centre, a division of Tata Consultancy Services which in turn is a division of Tata Sons Limited, an Indian company of 54B, Hadapsar Industrial Estate, Pune 411013, India, all Indian nationals The following specification particularly describes the nature of this invention and the manner in which it is to be performed : ORIGINAL 09-12-2003 GRANTED 02-07-2004 FIELD OF INVENTION This invention relates to a filter media for removal of fluoride ion contamination from water, a device and a method for purifying fluoride ion contaminated water. The World Health Organization (WHO) prescribes guideline of 1.5 ppm fluorine for safe drinking water [WHO (1996) report on 'Fluorine and fluorides', Environmental Health Criteria 36, International Programme on Chemical Safety, WHO, 1984]. The WHO guideline values for fluoride in drinking water were re¬evaluated in 1996. Presence of relatively high fluoride content in drinking water greater than 1.5 ppm has serious health consequences. It causes dental and skeletal fluorosis, an insidious long termed, cumulative and irreversible disease. Available data indicate that tens of millions people in at least 25 countries around the globe are affected by fluorosis. Closer home, 19 of India's 32 states are identified as endemic with fluorosis where fluoride concentrations as high as 38.5 ppm have been reported [Down to Earth, 27-41, April 15, 2003]. Unfortunately, due to various techno-socio-economic reasons, prevention of fluorosis through the treatment of drinking water can become an almost intractable problem [Heidweiller, V.M.L., (1992) Fluoride Removal Methods. In: Endemic Fluorosis In Developing Countries: Causes, Effects and Possible Solutions, Chap. 6, Frencken, J.E. (Ed.), Report of a Symposium held in Delft, the Netherlands, NIPG-TNO, Leiden; and Bulusu, K.R., Sundaresan, B.B., Pathak, B.N., Nawlakhe, W.G.(1979) Fluorides in Water, Defluoridation Methods and Their Limitations. Journal of the Institution of Engineers (India), 60,1-25]. Techniques for removal of fluoride fall into two broad categories, namely, precipitation and adsorption. A prominent method for removal of fluoride from water belonging to the first category is the well known Nalgonda technique [Nawlakhe, W.G., Kulkarni, D.N., Pathak, B.N. and Bulusu, K.R.. Defluoridation of Water by Nalgonda Technique, Indian Journal of Environmental Health, 1975, 17(1), 26-65]. It comprises of treating water with alum (aluminium sulphate) and lime to form precipitate of fluoride-aluminium complex which is separated by sand filter to give potable water of less than 1.5 ppm fluoride. The Nalgonda method is a multi-stage process involving precipitation and separation. It may be economical but not simple enough for adoption in the rural setting. Another prominent method belonging to the second category for removal of fluoride from water comprises of abstraction of fluoride ions by adsorption on the alumina surface [Fink, G.J. and Lindsay, F.K. (1936) Activated Alumina for Removing fluorides from Drinking Water. Industrial and Engineering, 28(9), 947-948]. In both the methods, an aluminium compound having hydroxyl (OH-) ions on the surface is employed for replacing and/or complexing with the fluoride ions (F~) in water. Activated alumina is an expensive material, its fluoride removal capacity is rather low and it is unlikely to be readily available in villages. Similar conclusions can be derived with respect to some other methods reported in the literature, for example defluoridation using bone charcoal [AWWA (1971) Defluoridation of Water. In: Water Quality and Treatment, 436-440, 3rd Edition, McGraw-Hill] and fired clay [Moges, G., Zwenge, F. and Socher, M. (1996) Preliminary Investigations on the Defluoridation of Water Using Fired Clay Chips. Journal of African Earth Science, 21(4), 479-482]. One of the recent and promising methods for fluoride removal is through contact precipitation. This method comprises of precipitation as well as adsorption. Here calcium, and phosphate compounds are added to the water upstream through catalytic filter bed of bone charcoal [Dahi, E. (1996) Contact Precipitation for Defluoridation of Water. Paper presented at 22nd WEDC Conference, New Delhi, 9-13 September 1996]. This method is a multi-stage process which involves precipitation and separation. These fluoride treatment methods are generally designed for community level operations, which invariably introduces additional and, at times insurmountable challenges in organizing local management structures such as village cooperatives and motivating them for successful implementation of the technology on a sustained basis. Studies have been reported on hydrous alumina oxides for adsorption of fluoride ions [Hao, O.J. and Huang, C.P. (1986) Adsorption characteristics of fluoride onto hydrous alumina. Journal of Environmental Engineering, 112(6), 1054-1069]. There are also reports of the use of aluminium hydroxide coated sand for removal of microbial contaminants from water [Lukasik, Jerszy (1998), The Removal of Microbial and Chemical Contaminants from Aqueous Solutions by Particles Coated with Iron and Aluminium Hydroxides, Ph. D Dissertation, University of Florida]. But removal of fluoride from water using aluminium hydroxide coated sand or any other substrate has not been reported till date. An object of the invention is to provide an aluminium hydroxide coated rice husk ash filter media for efficient and cost effective removal of fluoride in water meant for drinking which is suitable for domestic and household applications. Another object of the invention is to provide a method for making aluminium hydroxide coated rice husk ash based filter media which is simple, economical and convenient to implement in rural settings. The novelty and originality of our invention lie in employing rice husk ash as the substrate for coating widi aluminium hydroxide by a controlled and optimized process. This approach has significant advantages, which could overcome the problems associated with presently available methods as briefly stated above. DETAILED DESCRIPTION OF THE INVENTION Rice husk is a perennially renewable agro-waste available at virtually no cost wherever rice paddy is grown. On combustion, the rice husk ash residue contains 85-95% silica, 4-12% carbon and rest comprising various metal oxides such as alkali, alkali earth and iron oxides. Because of its crypto-crystalline or amorphous and highly porous structure, the BET (Brunauer Emmett Teller) surface area of rice husk ash can be as high as 80-100 square meters per gram, depending on the conditions employed for combustion of rice husk. Because rice husk ash is lighter in bulk density and has an order of magnitude greater surface area per unit mass than sand, it acquires when coated with aluminium hydroxide, near ideal combination of properties as a filter media with fluoride removal properties. Rice husk ash may be produced by burning rice husk in heaps, in a step grate furnace, tube-in-basket (TiB) burner [Kapur P. C, (1985) Production of bio-silica from the combustion of rice husk in TiB burner, Powder Tech, 44, 63-67] or obtained from boilers and brick kiln etc., provided it is free of unburned husk and wood tars, grit, stones and fused lumps of silica. The size of rice husk ash should be between 38 to 850 microns preferably less than 425 micron (passing 37mesh). The rice husk ash does not remove fluoride on it's own and it is necessary to coat it with aluminium hydroxide. The coated rice husk ash is prepared by precipitation of aluminium hydroxide on the surface of the rice husk ash using aluminium salt and strong alkali. Our extensive investigations show that for best results it is important to optimize the coating process. The optimum conditions require that pH at the coating stage should be maintained preferably between 4-7. The concentration of the aluminium salt used for coating should preferably lie between 0.1-1 M and strong alkali used should be six times the concentration of aluminium salt. The precipitation of aluminium hydroxide on rice husk ash surface should be dried at 90 to 120°C, preferably at 100 to 110°C. The aluminium hydroxide coated rice husk ash produced in this manner has an approximate BET surface area of 20 - 50 square meter per gram. The amount of aluminium hydroxide deposited on the rice husk ash varies from 0.39 to 0.54 gram per gram of rice husk ash. This invention relates to a filter media for removal of fluoride ion contamination from water which comprises rice husk ash having aluminium hydroxide coating on the surface thereof. This invention also relates to a device for purifying fluoride ion contaminated water which comprises a housing provided with an inlet and outiet means and a layer of rice husk ash coated with aluminium hydroxide filter media positioned in between two water permeable holding means housed therein. This invention also relates to a method of purifying water from fluoride ion contamination which comprises the steps of passing water having high fluoride concentration through a filter media of rice husk ash coated with aluminium hydroxide and thereafter collecting the water which has been filtered therethrough. The following experimental examples are illustrative of the invention but not limitative of the scope thereof. Example 1 50 g of rice husk ash was added to 250 ml of 0.5 M aluminium sulphate solution and kept soaked for 15 minutes. Then 210 ml of sodium hydroxide (NaOH) solution of 3M strength was slowly added to the aluminium sulphate and ash slurry with gende stirring. The NaOH reacted with aluminium sulphate to form aluminium hydroxide which deposited on rice husk ash particles^Addition of the NaOH was stopped when the pH of the slurry was 4.6 to 4.9. After settling the coated rice husk ash, excess liquid was filtered off in a Buckner funnel. The filter cake was dried in an oven at 110 °C for 5 -7 hours. A highly friable dry cake resulted which could be readily crushed into a powder. 20 g of aluminium hydroxide coated rice hush ash powder was placed in a plastic cylinder to form a bed of 3.5 cm diameter and 3 cm height. A layer of sand 1 cm in height was placed at the bottom of the column to hold back the fine ash particles in the filter bed. A layer of 1 cm sand was placed on the top of the ash bed. Tap water (pH 7 -7.3, conductivity 80-120 mho/cm) was spiked with sodium fluoride to give 10 ppm (parts per million) concentration of fluoride. The spiked water was continuously passed through the filter bed at flow rate of 2-2.2 liters/hour and the filtered water in the output stream was monitored for fluoride at regular intervals. After passing 14-15 litres of water, the calculated fluoride uptake capacity of coated rice husk ash medium was 7-7.5 mg/g. It shows that input water of 10 ppm fluoride concentration after passing through the filter bed resulted in less than 1.5 ppm of fluoride in the filtered water. Example 2 Aluminium hydroxide coated rice husk ash powder was prepared following the procedure of Example 1. 250 ml of 0.7 M aluminium sulphate solution was mixed with 50 g rice husk ash. Next, 220 ml of 4 M NaOH solution was added slowly with continuous stirring such that the pH of the slurry reached 4.8 to 5. 20 g of aluminium hydroxide coated rice husk ash powder was tested as described in Examplel. The fluoride uptake capacity of the filter was found to be llmg/g when 22-23 litres of tap water spiked with 10 ppm fluoride was passed through the filter bed of coated rice husk ash. This shows that input water of 10 ppm fluoride concentration after passing through the filter bed resulted in less than 1.5 ppm of fluoride in the filtered water. Example 3 20 g of aluminium hydroxide coated rice husk ash (as prepared by the method described in Example 2) was tested for fluoride removal. The fluoride uptake capacity of the filter was found to be 9-10mg/g when 38- 40 litres of tap water spiked with 5 ppm fluoride concentration was passed through the filter bed of coated rice husk ash. This shows that input water of 5 ppm fluoride concentration after passing through the filter bed resulted in less than 1.5 ppm of fluoride in the filtered water. Example 4 Aluminium hydroxide coated rice husk ash powder was prepared following the procedure of Example 1. 250 ml of 0.7 M aluminium sulphate solution was mixed with 50 g rice husk ash. Next, 260 ml of 4M NaOH solution was added slowly with continuous stirring such that the pH of the slurry reached 6.8 to 7. 20 g of aluminium hydroxide coated rice husk ash powder of was tested as described in Example 1. The fluoride uptake capacity of the filter was found to be 7-8mg/g when 15-16 litres of tap water spiked with fluoride of 10 ppm concentration was passed through the filter bed of coated rice husk ash. This shows that input water of 10 ppm fluoride concentration after passing through the filter bed resulted in less than 1.5 ppm of fluoride in the filtered water. It is seen from the examples 1, 2, 3 and 4 that the filter of the invention removes fluoride from water below acceptable levels i.e. 1.5 ppm. WE CLAIM 1. A filter media for removal of fluoride ion contamination from water comprising rice husk ash having aluminium hydroxide coated on the surface thereof. 2. The filter media as claimed in claim 1, wherein said rice husk ash coated with aluminium hydroxide is either in cake or powder form. 3. The filter media as claimed in claims 1 and 2, wherein aluminium hydroxide is coated on rice husk ash by precipitation. 4. The filter media as claimed in claims 1 to 3, wherein said precipitation of aluminium hydroxide on the surface of rice husk ash is carried out by treating ^ rice husk ash with an aluminium salt solution in the presence of a strong alkali. 5. The filter media as claimed in claim 4, wherein the concentration of aluminium salt solution is 0.1 M to 1 M and the precipitation is effected at a pH ranging from 4 to 7. 6. The filter media as claimed in claims 4 and 5, wherein the concentration of alkali is about six times the concentration of said aluminium salt. 7. The filter media as claimed in claims 4 and 5, wherein the precipitation of aluminium hydroxide on rice husk ash surface should/be dried at 90 to 120°C, preferably at 100 to 110°C. 8. The filter media as claimed in claims 1 to 7, wherein said aluminium hydroxide coated on rice husk ash has a BET (Brunauer Emmett Teller) surface area of 20-50 square meter per gram. 9. A device for purifying fluoride ion contaminated water comprising a housing provided with an inlet and outlet means, and, at least one layer of filter media consisting of rice husk ash coated with aluminium hydroxide positioned in between two water permeable holding means. 10. A filter media for removal of fluoride ion contamination from water substantially as herein described. 11. A device for purifying fluoride ion contaminated water/substantially as herein described. Dated this 9th day of December 2003. (Karuna Goleria) of DePENNING & DePENNING Agent for the Applicants

Full Text

FORM 2
THE PATENTS ACT 1970 (39 of 1970)
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE
A filter media for removal of fluoride ion contamination from water, a device and a method for purifying fluoride ion contaminated water
APPLICANTS
Tata Consultancy Services (a Division of Tata Sons Limited) of Bombay House, Sir Homi Mody Street, Mumbai - 400023, Maharashtra, India, an Indian company
INVENTOR
Under Section 28(2)
"vivek Ganvir, Kalyan Kumar Das and Prakash Chand Kapur, Tata Research Development and Design Centre, a division of Tata Consultancy Services which in turn is a division of Tata Sons Limited, an Indian company of 54B, Hadapsar Industrial Estate, Pune 411013, India, all Indian nationals
The following specification particularly describes the nature of this invention and the manner in which it is to be performed :

ORIGINAL
09-12-2003

GRANTED
02-07-2004

FIELD OF INVENTION
This invention relates to a filter media for removal of fluoride ion contamination from water, a device and a method for purifying fluoride ion contaminated water.
The World Health Organization (WHO) prescribes guideline of 1.5 ppm fluorine for safe drinking water [WHO (1996) report on 'Fluorine and fluorides', Environmental Health Criteria 36, International Programme on Chemical Safety, WHO, 1984]. The WHO guideline values for fluoride in drinking water were re¬evaluated in 1996. Presence of relatively high fluoride content in drinking water greater than 1.5 ppm has serious health consequences. It causes dental and skeletal fluorosis, an insidious long termed, cumulative and irreversible disease. Available data indicate that tens of millions people in at least 25 countries around the globe are affected by fluorosis. Closer home, 19 of India's 32 states are identified as endemic with fluorosis where fluoride concentrations as high as 38.5 ppm have been reported [Down to Earth, 27-41, April 15, 2003]. Unfortunately, due to various techno-socio-economic reasons, prevention of fluorosis through the treatment of drinking water can become an almost intractable problem [Heidweiller,

V.M.L., (1992) Fluoride Removal Methods. In: Endemic Fluorosis In Developing Countries: Causes, Effects and Possible Solutions, Chap. 6, Frencken, J.E. (Ed.), Report of a Symposium held in Delft, the Netherlands, NIPG-TNO, Leiden; and Bulusu, K.R., Sundaresan, B.B., Pathak, B.N., Nawlakhe, W.G.(1979) Fluorides in Water, Defluoridation Methods and Their Limitations. Journal of the Institution of Engineers (India), 60,1-25].
Techniques for removal of fluoride fall into two broad categories, namely, precipitation and adsorption. A prominent method for removal of fluoride from water belonging to the first category is the well known Nalgonda technique [Nawlakhe, W.G., Kulkarni, D.N., Pathak, B.N. and Bulusu, K.R.. Defluoridation of Water by Nalgonda Technique, Indian Journal of Environmental Health, 1975, 17(1), 26-65]. It comprises of treating water with alum (aluminium sulphate) and lime to form precipitate of fluoride-aluminium complex which is separated by sand filter to give potable water of less than 1.5 ppm fluoride. The Nalgonda method is a multi-stage process involving precipitation and separation. It may be economical but not simple enough for adoption in the rural setting.
Another prominent method belonging to the second category for removal of fluoride from water comprises of abstraction of fluoride ions by adsorption on the alumina surface [Fink, G.J. and Lindsay, F.K. (1936) Activated Alumina for Removing

fluorides from Drinking Water. Industrial and Engineering, 28(9), 947-948]. In both the methods, an aluminium compound having hydroxyl (OH-) ions on the surface is employed for replacing and/or complexing with the fluoride ions (F~) in water. Activated alumina is an expensive material, its fluoride removal capacity is rather low and it is unlikely to be readily available in villages. Similar conclusions can be derived with respect to some other methods reported in the literature, for example defluoridation using bone charcoal [AWWA (1971) Defluoridation of Water. In: Water Quality and Treatment, 436-440, 3rd Edition, McGraw-Hill] and fired clay [Moges, G., Zwenge, F. and Socher, M. (1996) Preliminary Investigations on the Defluoridation of Water Using Fired Clay Chips. Journal of African Earth Science, 21(4), 479-482].
One of the recent and promising methods for fluoride removal is through contact precipitation. This method comprises of precipitation as well as adsorption. Here calcium, and phosphate compounds are added to the water upstream through catalytic filter bed of bone charcoal [Dahi, E. (1996) Contact Precipitation for Defluoridation of Water. Paper presented at 22nd WEDC Conference, New Delhi, 9-13 September 1996]. This method is a multi-stage process which involves precipitation and separation. These fluoride treatment

methods are generally designed for community level operations, which invariably introduces additional and, at times insurmountable challenges in organizing local management structures such as village cooperatives and motivating them for successful implementation of the technology on a sustained basis.
Studies have been reported on hydrous alumina oxides for adsorption of fluoride ions [Hao, O.J. and Huang, C.P. (1986) Adsorption characteristics of fluoride onto hydrous alumina. Journal of Environmental Engineering, 112(6), 1054-1069]. There are also reports of the use of aluminium hydroxide coated sand for removal of microbial contaminants from water [Lukasik, Jerszy (1998), The Removal of Microbial and Chemical Contaminants from Aqueous Solutions by Particles Coated with Iron and Aluminium Hydroxides, Ph. D Dissertation, University of Florida]. But removal of fluoride from water using aluminium hydroxide coated sand or any other substrate has not been reported till date.
An object of the invention is to provide an aluminium hydroxide coated rice husk ash filter media for efficient and cost effective removal of fluoride in water meant for drinking which is suitable for domestic and household applications.

Another object of the invention is to provide a method for making aluminium hydroxide coated rice husk ash based filter media which is simple, economical and convenient to implement in rural settings.
The novelty and originality of our invention lie in employing rice husk ash as the substrate for coating widi aluminium hydroxide by a controlled and optimized process. This approach has significant advantages, which could overcome the problems associated with presently available methods as briefly stated above.
DETAILED DESCRIPTION OF THE INVENTION
Rice husk is a perennially renewable agro-waste available at virtually no cost wherever rice paddy is grown. On combustion, the rice husk ash residue contains 85-95% silica, 4-12% carbon and rest comprising various metal oxides such as alkali, alkali earth and iron oxides. Because of its crypto-crystalline or amorphous and highly porous structure, the BET (Brunauer Emmett Teller) surface area of rice husk ash can be as high as 80-100 square meters per gram, depending on the conditions employed for combustion of rice husk. Because rice husk ash is lighter in bulk density and has an order of magnitude greater surface area per unit mass than sand, it acquires when coated with aluminium hydroxide, near ideal combination of properties as a filter media with fluoride removal properties.

Rice husk ash may be produced by burning rice husk in heaps, in a step grate furnace, tube-in-basket (TiB) burner [Kapur P. C, (1985) Production of bio-silica from the combustion of rice husk in TiB burner, Powder Tech, 44, 63-67] or obtained from boilers and brick kiln etc., provided it is free of unburned husk and wood tars, grit, stones and fused lumps of silica. The size of rice husk ash should be between 38 to 850 microns preferably less than 425 micron (passing 37mesh). The rice husk ash does not remove fluoride on it's own and it is necessary to coat it with aluminium hydroxide. The coated rice husk ash is prepared by precipitation of aluminium hydroxide on the surface of the rice husk ash using aluminium salt and strong alkali. Our extensive investigations show that for best results it is important to optimize the coating process. The optimum conditions require that pH at the coating stage should be maintained preferably between 4-7. The concentration of the aluminium salt used for coating should preferably lie between 0.1-1 M and strong alkali used should be six times the concentration of aluminium salt. The precipitation of aluminium hydroxide on rice husk ash surface should be dried at 90 to 120°C, preferably at 100 to 110°C. The aluminium hydroxide coated rice husk ash produced in this manner has an approximate BET surface area of 20 - 50 square meter per gram. The amount of aluminium hydroxide deposited on the rice husk ash varies from 0.39 to 0.54 gram per gram of rice husk ash.

This invention relates to a filter media for removal of fluoride ion contamination from water which comprises rice husk ash having aluminium hydroxide coating on the surface thereof.
This invention also relates to a device for purifying fluoride ion contaminated water which comprises a housing provided with an inlet and outiet means and a layer of rice husk ash coated with aluminium hydroxide filter media positioned in between two water permeable holding means housed therein.
This invention also relates to a method of purifying water from fluoride ion contamination which comprises the steps of passing water having high fluoride concentration through a filter media of rice husk ash coated with aluminium hydroxide and thereafter collecting the water which has been filtered therethrough.
The following experimental examples are illustrative of the invention but not limitative of the scope thereof.
Example 1
50 g of rice husk ash was added to 250 ml of 0.5 M aluminium sulphate solution and kept soaked for 15 minutes. Then 210 ml of sodium hydroxide

(NaOH) solution of 3M strength was slowly added to the aluminium sulphate and ash slurry with gende stirring. The NaOH reacted with aluminium sulphate to form aluminium hydroxide which deposited on rice husk ash particles^Addition of the
NaOH was stopped when the pH of the slurry was 4.6 to 4.9. After settling the coated rice husk ash, excess liquid was filtered off in a Buckner funnel. The filter cake was dried in an oven at 110 °C for 5 -7 hours. A highly friable dry cake
resulted which could be readily crushed into a powder.
20 g of aluminium hydroxide coated rice hush ash powder was placed in a plastic cylinder to form a bed of 3.5 cm diameter and 3 cm height. A layer of sand 1 cm in height was placed at the bottom of the column to hold back the fine ash particles in the filter bed. A layer of 1 cm sand was placed on the top of the ash bed. Tap water (pH 7 -7.3, conductivity 80-120 mho/cm) was spiked with sodium fluoride to give 10 ppm (parts per million) concentration of fluoride. The spiked water was continuously passed through the filter bed at flow rate of 2-2.2 liters/hour and the filtered water in the output stream was monitored for fluoride at regular intervals. After passing 14-15 litres of water, the calculated fluoride uptake capacity of coated rice husk ash medium was 7-7.5 mg/g. It shows that input water of 10 ppm fluoride concentration after passing through the filter bed resulted in less than 1.5 ppm of fluoride in the filtered water.

Example 2
Aluminium hydroxide coated rice husk ash powder was prepared following the procedure of Example 1. 250 ml of 0.7 M aluminium sulphate solution was mixed with 50 g rice husk ash. Next, 220 ml of 4 M NaOH solution was added slowly with continuous stirring such that the pH of the slurry reached 4.8 to 5.
20 g of aluminium hydroxide coated rice husk ash powder was tested as described in Examplel. The fluoride uptake capacity of the filter was found to be llmg/g when 22-23 litres of tap water spiked with 10 ppm fluoride was passed through the filter bed of coated rice husk ash. This shows that input water of 10 ppm fluoride concentration after passing through the filter bed resulted in less than 1.5 ppm of fluoride in the filtered water.
Example 3
20 g of aluminium hydroxide coated rice husk ash (as prepared by the method described in Example 2) was tested for fluoride removal. The fluoride uptake capacity of the filter was found to be 9-10mg/g when 38- 40 litres of tap water spiked with 5 ppm fluoride concentration was passed through the filter bed of coated rice husk ash. This shows that input water of 5 ppm fluoride concentration after passing through the filter bed resulted in less than 1.5 ppm of fluoride in the filtered water.

Example 4
Aluminium hydroxide coated rice husk ash powder was prepared following the procedure of Example 1. 250 ml of 0.7 M aluminium sulphate solution was mixed with 50 g rice husk ash. Next, 260 ml of 4M NaOH solution was added slowly with continuous stirring such that the pH of the slurry reached 6.8 to 7.
20 g of aluminium hydroxide coated rice husk ash powder of was tested as described in Example 1. The fluoride uptake capacity of the filter was found to be 7-8mg/g when 15-16 litres of tap water spiked with fluoride of 10 ppm concentration was passed through the filter bed of coated rice husk ash. This shows that input water of 10 ppm fluoride concentration after passing through the filter bed resulted in less than 1.5 ppm of fluoride in the filtered water.
It is seen from the examples 1, 2, 3 and 4 that the filter of the invention removes fluoride from water below acceptable levels i.e. 1.5 ppm.

WE CLAIM
1. A filter media for removal of fluoride ion contamination from water comprising rice husk ash having aluminium hydroxide coated on the surface thereof.
2. The filter media as claimed in claim 1, wherein said rice husk ash coated with aluminium hydroxide is either in cake or powder form.
3. The filter media as claimed in claims 1 and 2, wherein aluminium hydroxide is coated on rice husk ash by precipitation.
4. The filter media as claimed in claims 1 to 3, wherein said precipitation of aluminium hydroxide on the surface of rice husk ash is carried out by treating ^ rice husk ash with an aluminium salt solution in the presence of a strong alkali.
5. The filter media as claimed in claim 4, wherein the concentration of aluminium salt solution is 0.1 M to 1 M and the precipitation is effected at a pH ranging from 4 to 7.
6. The filter media as claimed in claims 4 and 5, wherein the concentration of alkali is about six times the concentration of said aluminium salt.

7. The filter media as claimed in claims 4 and 5, wherein the precipitation of aluminium hydroxide on rice husk ash surface should/be dried at 90 to 120°C, preferably at 100 to 110°C.
8. The filter media as claimed in claims 1 to 7, wherein said aluminium
hydroxide coated on rice husk ash has a BET (Brunauer Emmett Teller)
surface area of 20-50 square meter per gram.

9. A device for purifying fluoride ion contaminated water comprising a housing
provided with an inlet and outlet means, and, at least one layer of filter media consisting of rice husk ash coated with aluminium hydroxide positioned in
between two water permeable holding means.
10. A filter media for removal of fluoride ion contamination from water substantially as herein described.
11. A device for purifying fluoride ion contaminated water/substantially as herein described.
Dated this 9th day of December 2003.
(Karuna Goleria) of DePENNING & DePENNING Agent for the Applicants

Documents:

1256-mum-2003-cancelled pages(9-12-2003).pdf

1256-mum-2003-claims(granted)-(9-12-2003).doc

1256-mum-2003-claims(granted)-(9-12-2003).pdf

1256-mum-2003-correspondence(8-12-2005).pdf

1256-mum-2003-correspondence(ipo)-(3-3-2005).pdf

1256-mum-2003-form 1(6-12-2003).pdf

1256-mum-2003-form 1(9-12-2003).pdf

1256-mum-2003-form 19(14-11-2004).pdf

1256-mum-2003-form 2(granted)-(9-12-2003).doc

1256-mum-2003-form 2(granted)-(9-12-2003).pdf

1256-mum-2003-form 26(8-8-2004).pdf

1256-mum-2003-form 3(16-3-2004).pdf

1256-mum-2003-form 6(15-9-2004).pdf

1256-mum-2003-form 6(8-9-2004).pdf

1256-mum-2003-form 8(14-1-2004).pdf

1256-mum-2003-power of attorney(14-1-2004).pdf

1256-mum-2003-power of attorney(23-6-2004).pdf

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Patent Number

207190

Indian Patent Application Number

1256/MUM/2003

PG Journal Number

30/2007

Publication Date

27-Jul-2007

Grant Date

24-May-2007

Date of Filing

09-Dec-2003

Name of Patentee

TATA CONSULTANCY SERVICES LIMITED

Applicant Address

11TH FLOOR, AIR INDIA BUILDING, NARIMAN POINT, MUMBAI 400 021.

Inventors:

#	Inventor's Name	Inventor's Address
1	VIVEK GANVIR	TATA CONSULTANCY SERVICES LIMITED 11TH FLOOR, AIR INDIA BUILDING, NARIMAN POINT, MUMBAI 400 021.
2	PRAKASH CHAND KAPUR	TATA CONSULTANCY SERVICES LIMITED 11TH FLOOR, AIR INDIA BUILDING, NARIMAN POINT, MUMBAI 400 021.
3	KALYAN KUMAR DAS	TATA CONSULTANCY SERVICES LIMITED 11TH FLOOR, AIR INDIA BUILDING, NARIMAN POINT, MUMBAI 400 021.

PCT International Classification Number

C02F 1/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA