FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
Title of invention:
ARSENIC REMOVAL FILTER USING NANO IRON COATED RICE HUSK
ASH
Applicant
TATA Consultancy Services Limited A company Incorporated in India under The Companies Act, 1956
Having address:
Nirmal Building, 9th Floor,
Nariman Point, Mumbai 400021.
Maharashtra, India
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention relates to a method for preparing filter media for removing arsenic contamination. More particularly, the invention relates to method of coating nano iron particles on Rice Husk Ash (RHA) for preparing filter media.
BACKGROUND OF THE INVENTION
Arsenic contamination of ground water is fatal to human health. According to a report issued by World Health Organization (WHO) approximately 57 million people drink groundwater with arsenic concentrations. According to World Health Organization's arsenic concentration of 10 parts per billion in the ground water is safe, but in reality the concentration is higher in the groundwater.
Arsenic concentration in ground water occurs basically due to anoxic conditions of the subsurface. Different filtration technologies have been developed for removal of the arsenic from the ground water. These technologies mainly discloses about method, system and device for removing arsenic and iron contamination from the water.
Some of the commonly used filtration apparatus known to us in the art are kanchan arsenic filter (KAF) and '3-kalshi' filtration assembly that enables arsenic removal from drinking water and also enables microbiological removal of treatment.
The disclosed filter technology requires filter media which constitutes group of different arsenic removal materials such as iron nail, rice husk ash (RHA), aluminum, wood charcoal and fine sand. Rice husk ash (RHA) is commonly used filter media due to easy availability and cost effective nature.

Another technology i.e. developing tremendously is nanotechnology. Nanotechnology enables to create new materials with a vast range of application. One of the developments in the field is related to water filtration. The nano iron particles are used for removing arsenic from water. The common method for preparation of nano iron particles is from green tea extract.
Of the above mentioned state of the art technologies, the nano iron coated RHA is the most effective technique for removing arsenic. But, the problem of clogging, sludge disposal, high treatment cost and inconvenient process of producing nano iron coated RHA remains unaddressed. Thus, there is a need to provide a method which provides cost effective, simple and scalable method for coating of nano iron particle with RHA. There is also a need to provide a device for providing a high removal capacity for arsenic using a nano iron filter media.
OBJECTS OF THE INVENTION
The principal object of the present invention is to provide a method for preparing a coaled nano iron rice husk ash (RHA), which further acts as a filter media for removing arsenic contamination from the water.
Another object of present invention is to provide an apparatus for removal of arsenic impurities from water, which is simple, efficient and environmental friendly.
Yet another object of present invention is to provide an environmental friendly method for coating of nano iron on Rice Husk Ash (RHA).
Yet another object of present invention is to provide the nano iron particles that constitutes high surface volume ratio enabling the property of active arsenic removal material.

Yet another object of present invention is to provide a method for preparation of green tea extract which further used for preparation of nano iron coated rice husk ash (RHA).
Another significant object of the invention is to provide an apparatus adapted in a manner to prevent clogging and sludge deposition in the apparatus.
SUMMARY OF THE INVENTION
Before the present apparatuses and methods are described, it is to be understood that this invention in not limited to the particular apparatuses, and methodologies described, as there can be multiple possible implementation styles of the present invention which are not expressly illustrated in the present disclosure. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present invention which will be limited only by the appended claims.
The present invention provides a method of preparing a filter media for removal of arsenic and iron contamination from water via using a green tea extract, the said method comprising preparation of green tea extract. The method further comprises addition of 200 ml of 0.2 Molar solutions (M) of ferric salt solution to 200 ml of green tea extract containing 0.2 g of gum Arabic. Fine precipitate of nano iron is formed. To this suspension 25 g of Boiler RHA of size -212 +425 micron is added. This suspension is kept in a stirred vessel for 30 min. The pH of suspension is adjusted by adding 1 Molar solution (M) sodium hydroxide solution. The final pH of suspension is kept at 3-4. After stirring the mixture was filtered and dried in the oven a! 100 degree Celsius for 2 to 3 hours.

Another aspect of the invention is to provide an apparatus for filtering of arsenic and iron contamination from water, the said apparatus comprises a filter chamber, wherein the filter chamber further comprises a nano iron coated rice husk ash adapted to receive contaminated water from an inlet means disposed on the said apparatus and capable of eliminating arsenic therefrom to the level below 50 parts-per-billion (ppb).
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing summary, as well as the following detailed description of preferred embodiments, are better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings a few exemplary constructions of the invention; however, it is to be understood that the invention is not limited to the specific apparatuses and methods disclosed in the drawings.
Figure. 1 is a flow diagram depicting method for preparation of nano iron coated rice husk ash (RHA) according to one exemplary embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments are described in detail using the drawings. Note that the disclosed invention is not limited to the following description and it will be easily understood by those skilled in the art that various changes and modifications can be made in modes and details without departing from the spirit and the scope of the disclosed invention. Therefore, the disclosed invention is not interpreted as being limited to the description of the embodiments below.
The present invention relates to a method for preparing a filter media for removal of arsenic and iron contamination from water via using a green tea extract, the said

method comprising preparation of green tea extract; adding 200 ml of 0.2 Molar solution (M) of ferric solution drop wise to 400 mi of the green tea extract containing 0.2 gram of gum Arabic forming fine precipitate of nano iron; adding 25 gram of rice husk ash (RHA) to step (b) in the suspension; stirring the suspension in a stir tank reactor; filtering the stirred suspension; and drying the filtrate via a drying means.
The present invention further relates to a rice husk ash (RHA) as substrate for coating with nano iron by a controlled and optimized process.
According to an embodiment 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 residual contains 85-95 % silica, 4-12% carbon and rest comprising various metal oxides such as alkali, alkali earth and iron oxides. The rice husk ash (RHA) is crypto-crystalline or amorphous and highly porous structure, the surface area of rice husk ash is as high as 80-100 square meters per gram, depending on the conditions employed for combustion of rice husk.
In an embodiment of the invention the filter media comprises a rice husk ash (RHA) coated with nano iron.
In another embodiment of the invention method of preparing green tea extract is provided. The green tea extract is prepared by adding green tea leaves 12 grams to 400 mi boiling water (approximately 90 degree Celsius). The green tea leaves in boiling water is stirred for 15 min and allowed to cool to room temperature. This . suspension is centrifuged and filtered to get green tea extract.
The present invention discloses method for preparation of nano iron coated rice husk ash (RHA). The method is divided in two parts. a) Preparation of green tea extract; and

b) Preparation of nano iron coated RHA.
According to an embodiment of the invention the green tea extract is prepared by adding green tea leaves 12 gram to 400 ml boiling water (90 C). The green tea leaves in boiling water is stirred for 15 min and allowed to cool to room temperature. This suspension is centrifuged and filtered to get green tea extract.
According to an embodiment of the invention 200 ml of 0.2 Molar solution (M) of ferric salt solutions is added to 400 ml of green tea extract containing 0.2 gram of gum Arabic. Fine precipitate of nano iron is formed. To this suspension 25 gram of Boiler RHA of size -212 +425 micron was added. This suspension was kept in a stirred vessel for 30 min. The pH of suspension is adjusted by adding 1 Molar solution (M) sodium hydroxide solution. The final pH of suspension was kept at 4. After stirring the mixture was filtered and dried in the oven at 100 degree Centigrade for 2-3 hours.
According to another embodiment of the invention the nano iron particles is adapted for high surface volume ratio enabling the property of active arsenic removal
material.
According to another embodiment of the invention an apparatus for filtering of arsenic and iron contamination from water is provided, the said apparatus comprising a filter chamber comprising a nano iron coated rice husk ash (RHA) adapted to receive contaminated water from an inlet means disposed on the said apparatus and capable of eliminating arsenic therefrom to the level below 50 parts-per-billion (ppb).
According to another embodiment of the invention the apparatus is provided comprising a housing provided with an inlet and an outlet, and at least one layer of

filter media comprising a nano iron coated rice husk ash (RHA) positioned in between two water permeable holding means.
This invention also relates to method of purifying water from arsenic contamination comprising the steps of passing arsenic contaminated water through a filter media of nano iron coated rice husk ash.
Figure 1 is a flow diagram depicting method (100) for preparation of nano coated rice husk ash (RHA) according to one exemplary embodiment of the invention.
The process starts at the step 10 preparation of green tea extract. In the steps 20 adding 200 ml of 0.2 Molar solution (M) ferric solution drop wise to 400 ml of the green tea extract containing 0.2 gram of gum arabic forming fine precipitate of nano iron. At the step 30, adding 25 gram of rice husk ash (RHA) to step (20). At the step 40, stirring of the suspension is done in a stir tank reactor. At the step 50, filtering the stirred suspension via a vacuum/pressure filter and the process ends at the step 60 drying the filtrate via an oven/dryer to form the nano iron coated RHA.
The following examples are illustrative of the present invention but not limitative of the scope thereof.
Example 1
Green tea extract is prepared by boiling 12 g of green tea in 400 ml of distilled water. The green tea leaves were separated by centrifuge to get green tea extract. 200 ml of 0.2 M ferric chloride solution was added to 400 ml of green tea extract with gentle stirring. The ferric salt was reduced to form nano iron size of 150-250 nm. 25 g of rice husk ash was then slowly added to slurry of nano iron and kept soaked for 15 minutes. Then sodium hydroxide (NaOH) solution of I- Molar solution (M) strength

was then slowly added to the nano iron coated ash slurry with gentle stirring. Addition of the NaOH was stopped when the pH of the slurry was 3.0 to 3.5. The pH adjusted slurry was allowed to settle for 15-20 min. After settling the coated rice husk ash, the excess liquid was filtered off in a Buckner funnel. The filter cake was dried in an oven at 90-100 °C for 2 -3 hours. A highly friable dry cake resulted which could be readily crushed into a powder.
20 gram of nano iron coated rice hush ash powder was placed in a glass cylinder to form a bed of 3.5-cm diameter and 3-cm height. A layer of sand 1-cm 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. Ground water pH 7.5 -8.5, conductivity 750-800 mho/cm was spiked with sodium arsenate to give 300-ppb (parts per billion) concentration of arsenic. The spiked water was continuously passed through the filter bed at flow rate of 1-1.2 liters/hour and the filtered water in the output was monitored for arsenic at regular intervals. After passing 12-13 litres of water, the calculated arsenic uptake capacity of coated rice husk ash medium was 0.2 -0.25 mg/g. It shows that input water of 300 ppb (parts per billion) arsenic concentration after passing through the filter bed resulted in less than 50 ppb (parts per billion) of arsenic in the filtered water.

Example 2
Nano iron coated rice husk ash powder was prepared following the procedure of Example 1 and 200 ml of 0.4 Molar solution (M) Ferric chloride solution was added to tea extract to form nano iron. This nano iron slurry was mixed with 25 gram rice husk ash. Next,l Molar solution (M) NaOH solution was added slowly with continuous stirring such that the pH of the slurry reached 3.0 to 3.5.
20 gram of nano iron coated rice husk ash powder was tested as described in Example 1. The arsenic uptake capacity of the filter was found to be 0.4-0.45mg/g when 22-23 litres of tap water spiked with arsenic of 300 ppb (parts per billion) was passed through the filter bed of coated rice husk ash. This shows that input water of 300 ppb (parts per billion) arsenic concentration after passing through the filter bed resulted in less than 50 ppb (parts per billion) of arsenic in the filtered water. Example 3
Nano iron coated rice husk ash powder was prepared following the procedure of Example 1 and 24 gram of tea extract is prepared in 400 ml of water and 200 ml of 0.4 Molar solution (M) Ferric chloride solution was added to this tea extract to form nano iron. This nano iron slurry was mixed with 25 gram rice husk ash. Next, 1 Molar solution (M) NaOH solution was added slowly with continuous stirring such that the pH of the slurry reached 3.0 to 3.5.

20 gram of nano iron coated rice husk ash powder was tested as described in Example 1. The arsenic uptake capacity of the filter was found to be 0.4~0.45mg/g when 22-23 litres of tap water spiked with arsenic of 300 ppb (parts per billion) was passed through the filter bed of coated rice husk ash. This shows that input water of 300 ppb (parts per billion) arsenic concentration after passing through the filter bed resulted in less than 50 ppb (parts per billion) of arsenic in the filtered water.
Example 4
Nano iron coated rice husk ash powder was prepared following the procedure of Example 1 and 12 gram of tea extract is prepared in 400 ml of water and 200 ml of 0.4 Molar solution (M) Ferric chloride solution was added to this tea extract to form nano iron. This nano iron slurry was mixed with 50 gram rice husk ash. Next. 1 Molar solution (M) NaOH solution was added slowly with continuous stirring such that the pH of the slurry reached 3.0 to 3.5.
20 gram of nano iron coated rice husk ash powder was tested as described in Example 1. The arsenic uptake capacity of the filter was found to be 0.2-0.25mg/g when 12-13 litres of tap water spiked with arsenic of 300 ppb (parts per billion) was passed through the filter bed of coated rice husk ash. This shows that input water of 300 ppb (parts per billion) arsenic concentration after passing through the filter bed resulted in less than 50 ppb (parts per billion) of arsenic in the filtered water,

Example 5
20 gram of prepared nano iron coated rice husk ash was tested as described in Example 2. Tap water (pH 7.0 -7.5, conductivity 100-120 mho/cm) was spiked with sodium arsenate to give 300-ppb (parts per billion) concentration of arsenic. The spiked water was continuously passed through the filter bed at flow rate of 1-1.2 liters/hour and the filtered water in the output was monitored for arsenic at regular intervals. The arsenic uptake capacity of the filter was found to be 0.9-1.0 mg/g when 38- 40 litres of tap water spiked with arsenic of 300 ppb (parts per billion) was passed through the filter bed of coated rice husk ash. This shows that input water of 300 ppb (parts per billion) arsenic concentration after passing through the filter bed resulted in less than 50 ppb (parts per billion) of arsenic in the filtered water.
Example 6
20 gram of prepared nano iron coated rice husk ash was tested as described in Example 2. Ground water (pH 7.5 -8.5, conductivity 750-800 mho/cm) was spiked with sodium arsenate to give 150-ppb (parts per billion) concentration of arsenic The arsenic uptake capacity of the filter was found to be 0.4-0.45mg/g when 38- 40 litres of tap water spiked with arsenic of 150 ppb (parts per billion) was passed through the filler bed of coated rice husk ash. This shows that input water of 150 ppb (parts per billion) arsenic concentration after passing through the filter bed resulted in less than 50 ppb (parts per billion) of arsenic in the filtered water.

The preceding description has been presented with reference to various embodiments of the invention. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described apparatuses and methods of operation can be practiced without meaningfully departing from the principle and scope of this invention.
ADVANTAGES OF THE INVENTION
1) The present invention uses rice husk ash (RHA) which is the cheapest material of large reactive surface area, available freely all over the world.
2) The present invention provides an apparatus that is a highly affordable filtering medium par excellence for removal of suspended matter from drinking water.
3) The present invention provides a preparation of nano iron particles using a green tea extract providing greener route process.
4) The present invention provides a preparation of stable nano iron particles using a green tea extract and a dispersant
5) The present invention employed a novel method of coating nano iron produce by green tea extract on the rice husk ash surface.

WE CLAIM:
1. A method of preparing a filter media for removal of arsenic and iron contamination from water by using a green tea extract, the said method comprising steps of
a) preparation of the green tea extract;
b) adding 200 ml of 0.2 Molar solution (M) ferric solution drop wise to 200 ml of the green tea extract containing 0.2 gram of gum arabic forming fine precipitate of nano iron;
c) adding 25 g of rice husk ash (RHA) to step (b) in the suspension;
d) stirring the suspension in a stir tank reactor;
e) filtering the stirred suspension ; and
f) drying the filtrate via a drying means to form the nano iron coated RHA.

2. The method according to claim 1, further comprises adding 1 Molar solution sodium hydroxide solution to the suspension in the step (c) for adjusting pH to 3 to 4.
3. The method according to claim I, wherein the green tea extract is prepared by adding and stirring green tea leaves 2 to 3 gram to 200 ml boiling water, cooling the mixture, filtering and drying the mixture in the oven.
4. The method according to claim 1, wherein the drying means is an oven / dryer.
5. An apparatus for filtering of arsenic and iron contamination from water, the said apparatus comprising a filter chamber comprising a nano iron

coated rice husk ash adapted to receive contaminated water from an inlet means disposed on the said apparatus and capable of eliminating arsenic therefrom to the level below 50 parts-per-billion (ppb).