FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICA TION
(See section 10, rule 13)
1. Title of the invention
METHOD OF MAKING A WATER PURIFICATION COMPOSITION
2. Applicant(s)
Name Nationality Address
TATA CHEMICALS LIMITED INDIA BOMBAY HOUSE, 24 HOMI MODI STREET, MUMBAT-
400001
3. Preamble to the description
COMPLETE SPECIFIC A TION
The following specification particularly describes the invention and the manner in which it is
to be performed.

The present disclosure provides a method of making a water purification composition for removal of arsenic from water. The present disclosure also provides a water purification composition for removal of arsenic from water.
BACKGROUND
Arsenic, resulting from industrial and mine waste discharges or from natural erosion of arsenic containing rocks, is often found in surface and ground water. Common chemical forms of arsenic in the environment include arsenate (As(V)), arsenite (As(III)), dimethylarsinic acid (DMA) and monomethylarsenic acid (MMA). Arsenic occurs in drinking water in two major oxidation states: As(V), arsenate and As(IlI), arsenite. The consumption of drinking water containing even low levels of arsenic over long periods of time has been shown to be deleterious to human health. A range of diseases have been linked to arsenic exposure via drinking water including cancers, dermal lesions and skin diseases.
The WHO and USEPA (United States Environmental Protection Agency) have changed the recommended maximum permissible level of arsenic concentration in the drinking water from 50 ppb to 10 ppb. However, most of the developing nations are still using the previously prescribed limit of 50 ppb as their national standards. This is mainly due to the fact that there are tremendous economic costs involved in achieving the present WHO guidelines.
Furthermore, arsenic contamination poses a greater challenge for developing nations. This is because water treatment required for removal of arsenic often involves technologies that are relatively complex and costly. This problem is intensified in rural areas where access to safe drinking water is already limited.

There are number of commercially available arsenic removal methods that are suitable for the treatment of drinking water including anion exchange resins, activated alumina and iron flocculation processes. Conventional polymeric anion exchangers have a low selectivity for arsenate, and thus the high concentration of sulfate in drinking water successfully competes with arsenate for available anion exchange sites resulting in a short operational life. While on the other hand, Coagulation using iron floc as a treatment method is highly effective in removing arsenic from water but generates large amounts of a ferric hydroxide floc which will require safe disposal in a landfill. Therefore, capital equipment requirements are generally high.
Additionally, method of preparing iron oxide impregnated chitosan bead(s) using reverse phase suspension method is known in the art (Bingjie Liu et. al, "As (III) removal from aqueous solution using a-Fe203-impregnated chitosan beads"; 2010 International Conference on Digital Manufacturing & Automation; pp-289-292). The method used for preparing said beads is reverse phase suspension cross-linking method, wherein reverse phase suspension is prepared to facilitate mixing of two immiscible compounds i.e. organic and inorganic compounds. Further other reagents such as crosslinking agents and stabilizing agents are required to facilitate the formation of said beads. The said method is not easy to perform.
There is therefore a need for a water purification composition which is effective in removing both arsenic species (As(V) and As(III)) from water and a cost effective method of making a water purification composition for removal of arsenic from water.
SUMMARY
A method of making a water purification composition is disclosed. The method comprises of forming a chitosan solution by dissolving chitosan in an organic acid

solution, adding iron oxide particles to the chitosan solution and mixing the same to obtain a mixture, adding an alkali solution to the mixture at a predetermined rate to precipitate an iron oxide-chitosan matrix is disclosed. The method further comprises of washing and drying of the precipitate, grinding the precipitate and sieving the ground precipitate to obtain granules of a desired size.
A water purification composition for removal of arsenic from water is also disclosed. The water purification composition comprises of porous granules of an iron oxide-chitosan matrix wherein size of the iron oxide particles is in the range of 80 nm -300 nm and concentration of the iron oxide particles in the granules is at least 75%.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates X-Ray diffraction measurement A) Diffraction pattern of iron oxide powder obtained as a waste from a steel manufacturing plant (X-ray peaks match with standard diffraction pattern for alpha-Fe2O3); and B) Diffraction pattern of granules.
Figure 2 illustrates morphology and particle size of iron oxide particles and granules using Scanning Electron Microscopy.
Figure 3 Thermo Gravimetric Analysis (TGA) of iron oxide particles and granules.
Figure 4 illustrates column design and fabricated column packed with the granules.
DETAILED DESCRIPTION
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the disclosed process, and

such further applications of the principles of the invention therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
Reference throughout this specification to "one embodiment" "an embodiment" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase "in one embodiment", "in an embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The term "granule" as referred to herein means particles in the size range of 0.15 mm to 1 mm comprising iron oxide particles and chitosan. The garnules are characterized by high percentage loading of iron oxide particles and high porosity.
The present disclosure provides a method of making a water purification composition. Particularly, a method of making a water purification composition for removal of arsenic from water is disclosed. More particularly, a method of making a water purification composition for removal of arsenic from water comprising forming a chitosan solution by dissolving chitosan in an organic acid solution, adding iron oxide particles to the chitosan solution and mixing the same to obtain a mixture, adding an alkali solution to the mixture at a predetermined rate to precipitate an iron oxide-chitosan matrix is disclosed. The method further comprises of washing and drying of the precipitate, grinding the precipitate and sieving the ground precipitate to obtain granules of a desired size.
In accordance with an aspect, the granules obtained after grinding and sieving of the ground precipitate have size in the range of 0.15 mm to 1 mm.

In accordance with an aspect, the granules obtained are porous with concentration of iron oxide particles in the granule being at least 75% (w/w). By way of specific example, the concentration of iron oxide particles in the granule is 85% (w/w).
In accordance with an aspect, the granules are suitable as a water purification composition for removal of arsenic from water. The granules are capable of removing both As(III) and As(V). The chitosan present in the granules also adsorbs arsenic from water thus showing synergistic effect during purification of water.
In accordance with an embodiment, the chitosan is not more than 25% by weight in the granule. By way of specific example, chitosan is 15% by weight in the granule.
In accordance with an embodiment, the chitosan solution is prepared by dissolving chitosan in a citric acid solution.
In accordance with an aspect, the iron oxide particles added to the chitosan solution are nanoparticles of iron oxide. The nanoparticles of the iron oxide are obtained as a by-product of a steel manufacturing plant. By way of example, Table 1 enlists the properties of the iron oxide particles used in the disclosed method.

Table 1
In accordance with an embodiment, the chitosan is 10% by weight of the iron oxide particles. In other words, chitosan and iron oxide particles are used in a weight ratio of 1:10.

% Iron Oxide BET Surface Tap Particle Size
(by XRF) area density Distribution
(0.1% powder in DW,
Sonicated for 10 mins)
90 - 95 % Fe2O3 3.56 m2/g 0.9cc/g 80 to >300 nm

In accordance with an embodiment, the iron oxide particles aggregate in the presence of chitosan to facilitate formation of the desired sized granules.
In accordance with an embodiment, the iron oxide particles have a size in a range of 20-1000 nm and preferably in the range of 80 nm to 300 ran.
In accordance with an aspect the rate of addition of alkali solution is approximately 100 ml/min. It is preferred that the rate of addition of alkali solution is not more than 100 ml/min.
In accordance with an embodiment, the alkali solution is 10 % w/v solution of sodium hydroxide.
In accordance with an embodiment, the precipitated iron chitosan matrix is washed with distilled water, preferably twice.
In accordance with an embodiment, drying of the precipitate obtained after washing is carried out at a temperature of 90-100°C in a drying oven.
In accordance with an embodiment, drying is followed by grinding of the precipitate having about 20-25% moisture content. Grinding is carried out in a mixer to facilitate breaking of lumps. The grounded precipitate is then dried at a temperature of 90-100°C. Thus obtained dried precipitate is subjected to sieving utilizing nylon net with approximate 1 mm pore size and the dried precipitate that passes through the net is collected.
In accordance with an embodiment, the precipitate collected after passing through the nylon net is subjected to sieving through a mesh of 150 urn pore size to obtain granules. In accordance with an aspect, the granules should be at least 150 μm in size. The granules are collected on top of the mesh.
The present disclosure also provides a water purification composition for removal of arsenic from water. Particularly, the present disclosure provides a water purification

composition prepared by method disclosed herein. The water purification composition comprises of porous granules of an iron oxide-chitosan matrix wherein size of the iron oxide particles is in the range of 80 nm - 300 nm and concentration of the iron oxide particles in the granules is at least 75%.
The following example(s) of preparing a water purification composition for removal of arsenic from water and a water purification composition thereof are exemplary and should not be understood to be in any way limiting. Example 1:
About 500 grams of citric acid is dissolved in 10 litres of distilled water by stirring for 15 minutes in a vessel to obtain a solution. 200 grams of chitosan is added to the said solution under constant stirring for 1 hour to facilitate mixing of chitosan thoroughly in the solution. 2000 grams of iron oxide powder (nanoparticles) is added slowly under stirring to the solution obtained from the previous step followed by stirring for 1 hour to facilitate mixing of iron oxide particles properly. 2 litres of 10% (w/v) sodium hydroxide solution is added to the solution obtained from the previous step to facilitate precipitation of iron-chitosan matrix with the help of a master flex pump, such that the rate of addition of sodium hydroxide is 100 ml/min. Addition of sodium hydroxide solution is followed by stirring for 1 hour. After said stirring, the contents of the vessel are transferred to a beaker of 10 litres capacity. The precipitate is allowed to settle down. Separate the precipitate by decanting water from the beaker. The precipitate is then washed by adding 2 litres of distilled water to the beaker followed by stirring for 5 minutes. The precipitate is then allowed to settle down and separated from the beaker again by decanting water from the beaker. The precipitate is washed again by repeating the step of washing. After washing the precipitate twice, the precipitate is transferred to a drying tray for drying at a temperature of 90-100°C. Drying is carried out in a drying oven. The precipitate having

20-25% of moisture is then subjected to mild grinding to facilitate breaking of lumps followed by drying at a temperature of 90-100°C. The dried precipitate thus obtained is subjected to sieving through the nylon net having pore size of approximately 1 milimetre. The precipitate remaining on the top of the net is grounded to facilitate breaking. The dried precipitate which passes through the net is collected and sieved through a mesh of pore size 150 μm to obtain granules. The granules are collected on the top of the mesh. The granules have a size in the range of 0.15 milimetre to 1 milimetre. Example 2:
As illustrated in Figure 2, scanning electron micrograph study of the iron oxide particles and the granules indicate that there is no change in particle size and morphology of the iron oxide particles during the formation of the granules by the method disclosed herein. Thus there will be no reduction in the performance of the iron oxide in the gramile(s) of water purification composition. Further, BET surface area analysis of iron oxide particles and the granules is conducted and the results obtained are reproduced below (Table 2):

Sample BET Surface Area
Iron oxide particles 3.56 m2/gm
Granules (Iron oxide -Chitosan) 2.83 m2/gm
Table 2
The results indicate no significant reduction of surface area due to granulation of iron oxide particles. Example 3:
Figure 3 illustrates Thermo gravimetric analysis (TGA) of the iron oxide particles and the granules. TGA of iron oxide particles indicates no weight loss. TGA analysis of the granules indicates weight loss of approximately 15% which is attributed to the fact that

the granules are composed of 85% (w/w) of iron oxide particles and 15% (w/w) of the
chitosan.
Example 4:
Fabrication of column and using the same for water filtration:
Iron oxide granules are accommodated in a cylindrical column with a screen to protect iron fine leaching. Appropriate flow rate is maintained using a knob attached outside the column. Figure 4 illustrates the details about the column fabricated using the granules prepared by the disclosed method. The cylindrical column used to fabrication is 500 mm in height and 50 mm in diameter and is fabricated with a distinctively designed screen of pore size ~5 microns. The screen used is designed in a manner that aids in restricting escape of the granules with the output water and overcoming choking of filter over its life. The columns are packed with 300 g of iron oxide granules of size range 150 microns to 1 mm. Packing height of granules vary from 1/2 to 1/3 of the column height as the tap density of iron oxide powder varies from 0.5 to 1.1 g/cc. Once granules are packed, approximately 4 litres of RO (reverse osmosis) water is passed through the granules to remove fine particles of iron oxide (washing of color solution), which passes through the screen. Washing is continued until clear liquid is obtained as an output. Thereafter, washed packed columns are used in a filter for purification of arsenic contaminated water.
The granules upon coming in contact with water absorbs it and starts swelling indicating that water is entering inside the granules easily. The easy access of water inside the granules allows arsenic ions in the water to bind to the iron oxide particles. Example 5:
The granules packed in the column when tested by passing over a volume of 750 litres of simulated influent water composition identified by NSF/ANSI STANDARD-53

Drinking Water Treatment Units - Health Effects guidelines, produced efficient removal of arsenic (As(V) and As(III)), as illustrated in Table 3, 4 and 5.
Table 3 AS (III) removal efficiency:

Volume of Input
Flow Output
Water arsenic
rate in Arsenic in
passed in (HI) in ppb
lit/hour lrr ppb
2.9 21 50 3
2.46 54 50 10
2.74 98 50 7
2.26 135 50 5
2.9 166 50 0
2.2 204 50 0
2.4 290 50 0
2.7 318 50 5
2.4 348 50 5
1.84 410 50 0
1.92 527 50 5
1.64 653 50 5
1.56 783 50 0
Table 4
AS (V) removal efficiency:

Flow rate in lit/hour Water
passed in
Itr Input
arsenic (V)
in ppb Output
Arsenic in ppb
2.3 12 150 0
2.6 26 150 0
2.9 78 150 0
3 91 150 5
3.2 125 150 0
2.7 158 150 10
2.7 182 150 5
2.* 228 150 5
2.78 255 150 10
2.6 273 150 10
2.65 347 150 25
2.5 410 150 10
2.5 455 150 5
2.4 520 150 10
2.4 610 150 10
2.1 685 150 5
2.2 730 150 10
2 780 150 10
Table 5
AS (III and V) removal efficiency:

Flow rate in lit/hour Volume of
Water
passed in
ltr Input
arsenic
(III+V) in
ppb Output
Arsenic in
ppb
2.7 7 200 5
2.6 46 200 10
2.63 64 200 0
2.7 123 200 0
2.8 195 200 0
2.48 241 200 0
2.6 307 200 25
2.7 355 200 10
2,25 427 200 10
1.98 509 200 5
2.64 570 200 10
2.8 611 200 10
2.54 639 200 25
2.1 720 200 0
2.2 760 200 10
SPECIFIC EMBODIMENTS ARE DESCRIBED BELOW
A method of making a water purification composition for removal of arsenic from water comprising forming a chitosan solution by dissolving chitosan in an organic acid solution, adding iron oxide particles having size in the range of 80 nm to 300 ran to the

chitosan solution and mixing the same to obtain a mixture, adding an alkali solution to the mixture at a rate of not more than 100 ml/min to precipitate an iron oxide-chitosan matrix, washing and drying the precipitate; and grinding the precipitate and sieving the ground precipitate to obtain granules having size in the range of 0.15 mm to 1 mm; wherein the granules obtained are porous with concentration of iron oxide in the granule being at least 75% and are suitable as a water purification composition for removal of arsenic from water.
Such method (s), wherein the chitosan is 10% by weight of the iron oxide particles.
Such method (s), wherein the iron oxide particles are obtained from waste of a steel manufacturing plant.
A water purification composition for removal of arsenic from water comprising porous granules of an iron oxide-chitosan matrix wherein size of the iron oxide particles is in the range of 80 nm - 300 run and concentration of the iron oxide particles in the granules is at least 75%.
Such water purification composition(s), wherein the granules are not less than 150 urn in size.
INDUSTRIAL APPLICATION
The method of making a water purification composition for removal of arsenic from water described above is easy to perform and utilize waste generated from a steel manufacturing plant as a starting material. The granules obtained from the method described above are efficient in removing arsenic (As(III) and As(V)) from water as the concentration of iron oxide in the granules is high. Therefore, large amount of iron oxide can be packed in a column for purification of water thereby avoiding use of other materials such as carbon, sand and binders. The granules are highly porous and their swelling

property is advantageous for packing the same in a loose bed with appropriate mesh size. The chitosan used for the preparation of said granules also adsorbs arsenic (in addition to the iron oxide particles) from water thus showing synergistic effect during purification of water.

WE CLAIM:
1. A method of making a water purification composition for removal of arsenic from
water comprising:
forming a chitosan solution by dissolving chitosan in an organic acid solution;
adding iron oxide particles having size in the range of 80 nm to 300 nm to the chitosan
solution and mixing the same to obtain a mixture;
adding an alkali solution to the mixture at a rate of not more than 100 ml/min to
precipitate an iron oxide-chitosan matrix;
washing and drying the precipitate; and
grinding the precipitate and sieving the ground precipitate to obtain granules having
size in the range of 0.15 mm to 1 mm;
wherein the granules obtained are porous with concentration of iron oxide in the
granule being at least 75% and are suitable as a water purification composition for
removal of arsenic from water.
2. A method of making a water purification composition for removal of arsenic from water as claimed in claim 1, wherein the chitosan is 10% by weight of the iron oxide particles.
3. A method of making a water purification composition for removal of arsenic from water as claimed in claim 1, wherein the iron oxide particles are obtained from waste of a steel manufacturing plant.

4. A water purification composition for removal of arsenic from water comprising porous granules of an iron oxide-chitosan matrix wherein size of the iron oxide particles is in the range of 80 nm - 300 nm and concentration of the iron oxide particles in the granules is at least 75%.
5. A water purification composition for removal of arsenic from water as claimed in claim 4, wherein the granules are not less than 150 μm in size.