A WATER PURIFICATION COMPOSITION

The present disclosure provides a water purification composition for treatment of water. The present disclosure also provides a method of making a water purification composition for treatment of water.

DESCRIPTION OF RELATED ART

Clean potable water is a basic human requirement. However, a large portion of the world's population, especially those living in developing counties do not have access to clean potable water. Growing population, lack of sanitary condition, poverty, poor planning, industrial pollution, over exploitation of natural water and national disasters are the main reasons of contamination of water. This contaminated drinking water is a major vector of disease agents; from viruses to multicellular parasites (helminthes) causing diarrhea, dysentery, fever, anemia etc. Many water purification devices like in-line (electricity operated) devices, terminal end devices including counter top and faucet mounted filtration and self-contained batch system including gravity fed systems have been introduced into the market. The maintenance requirements and the high cost of consumables of these purifiers pose hurdles for the adoption of these devices. The major consumable of these purifiers is the composition used for the purification of water.

A variety of water purification compositions have been disclosed in the prior art including low cost alternatives such as rice husk ash, sand, activated carbon, diatomaceous earth etc. However, when such compositions are used alone for treatment of water, satisfactory removal of biological contaminants is not achieved. Further, filters that use compositions such as rice husk ash alone are bulky as a large amount of the composition is required to achieve satisfactory performance.

In order to enhance the performance these compositions have been coated with bactericidal agents such as silver. Indian patent application No. l576/MUM/2008 discloses rice husk ash coated with silver nanoparticles for treatment of water. Since rice husk ash is brittle, continuous flow of water through the silver nanoparticle coated rice husk ash bed creates compaction and channel formation in the bed. This leads to inconsistent flow of water and instances of choking of the bed. Moreover, as silver nanoparticles are unevenly distributed within the composition inconsistencies in leaching of silver ions is observed. This results in variation in anti-microbial activity during water purification.

Thus, there is a need for a water purification composition that is inexpensive, easy to use and shows removes microbial contamination from drinking water consistently.

SUMMARY

A water purification composition is disclosed. The water purification composition comprises porous granules of a particulate material, silver nanoparticles and polyvinyl alcohol matrix, wherein the silver nanoparticles and the particulate material are embedded in the polyvinyl alcohol matrix, the particulate material, polyvinyl alcohol and silver nanoparticles being present in a ratio of 100: 4.5: 0.7 to 100: 10: 0.7 on weight basis, and the porous granules having a size in a range of 0.1 mm to 3 mm.

A method for preparing a water purification composition is also disclosed. The method comprises the steps of preparing an aqueous solution of polyvinyl alcohol; preparing a mixture of particulate material and silver nanoparticles; mixing the aqueous solution of polyvinyl alcohol with the mixture of particulate material and silver nanoparticles to obtain aggregates of the particulate material, silver nanoparticles and polyvinyl alcohol; and drying the aggregates to obtain the water purification composition comprising porous granules of the particulate material, silver nanoparticles and polyvinyl alcohol matrix, wherein the silver nanoparticles and the particulate material are embedded in the polyvinyl alcohol matrix, and the porous granules have a size in the range of 0.1 mm to 3 mm.

A further method for preparing a water purification composition is disclosed. The method comprising the steps of preparing an aqueous solution of silver nanoparticles and polyvinyl alcohol; mixing the aqueous solution of silver nanoparticles and polyvinyl alcohol with a particulate material to obtain aggregates of particulate material, silver nanoparticles and polyvinyl alcohol; and drying the aggregates to obtain the water purification composition comprising porous granules of the particulate material, silver nanoparticles and polyvinyl alcohol matrix, wherein the silver nanoparticles and the particulate material are embedded in the polyvinyl alcohol matrix, and the porous granules have a size in the range of 0.1 mm to 3 mm. 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 disclosure generally relates to a water purification composition for treatment of water. Specifically, the water purification composition comprises porous granules of a particulate material, silver nanoparticles and a polyvinyl alcohol matrix, wherein the silver nanoparticles and particulate material are embedded in the polyvinyl alcohol matrix. The particulate matter, the polyvinyl alcohol, and silver nanoparticles are present in the porous granules in a ratio of 100:4.5:0.7 to 100:10:0.7 on weight bases. The porous granules have a size in a range of 0.1mm to 3mm.

The term "granule" as referred to herein means particles in the size range of 0.1 mm to 3 mm comprising silver nanoparticles and particulate material embedded in the polyvinyl alcohol matrix. The polyvinyl alcohol matrix with embedded silver nanoparticles may be in the form of a coating on the particulate material. The granules are characterized by uniform loading of silver nanoparticles throughout the granules and high porosity.

In accordance with an aspect, the granules are suitable as a water purification composition for removal of biological contaminants from water. The "particulate material" as referred to herein means a material that may be used for formation of granules. The particulate material includes but is not limited to rice husk ash, activated carbon, sand, diatomaceous earth, kaolinite, alumina, zinc oxide, titanium oxide, iron oxide, silica or mixtures thereof. The particulate material has a size in the range of 75 microns to 3.0 mm. In accordance with an aspect, the particulate material is rice husk ash, having a particle size in range of 75 microns to 100 microns.

In accordance with an aspect, the polyvinyl alcohol has a degree of hydrolysis of at least 70%. The polyvinyl alcohol has a molecular weight in a range of 75000 to 145000 Daltons. In accordance with an aspect, the silver nanoparticles are capped silver nanoparticles.

The silver nanoparticles includes but is not limited to silver nanoparticle-chitosan composite, silver nanoparticle-polyvinyl alcohol composite or silver nanoparticles-polyvinyl pyrrolidone composite.

The disclosure also relates to a method for preparing a water purification composition. In accordance with an embodiment, the method comprises preparing an aqueous solution of polyvinyl alcohol and preparing a mixture of particulate material and silver nanoparticles. The aqueous solution of polyvinyl alcohol is mixed with the mixture of particulate material and silver nanoparticles to obtain aggregates of the particulate material, silver nanoparticles and polyvinyl alcohol. The aggregates are dried to obtain the water purification composition, the water purification composition comprising porous granules of silver nanoparticles and particulate material embedded in the polyvinyl alcohol matrix.

The aqueous solution of polyvinyl alcohol may be prepared by dissolving polyvinyl alcohol in water maintained at a temperature of approximately 60°C or greater than 60°C. Alternatively, the aqueous solution of polyvinyl alcohol may be prepared by adding polyvinyl alcohol to water at room temperature and heating said solution to approximate 60°C or higher. Said solution may be stirred to ensure complete dissolution of polyvinyl alcohol in water. The aqueous solution of polyvinyl alcohol has a concentration in a range of 5 to 20% weight by weight.

In accordance with an aspect, the aqueous solution of polyvinyl alcohol and the mixture of particulate material and silver nanoparticles are mixed in a ratio of 1:3 to 5:6 weight by weight. In accordance with an alternate embodiment, the method for preparing water purification composition comprises the steps of preparing an aqueous solution of silver nanoparticles and polyvinyl alcohol and mixing the aqueous solution of silver nanoparticles and polyvinyl alcohol with a particulate material to obtain aggregates of particulate material, silver nanoparticles and polyvinyl alcohol. The aggregates are dried to obtain the water purification composition comprising porous granules of silver nanoparticles and particulate material embedded in the polyvinyl alcohol matrix.

The aqueous solution of silver nanoparticles and polyvinyl alcohol may be prepared by dissolving polyvinyl alcohol in an aqueous suspension of silver nanoparticles. The suspension of silver nanoparticles may be obtained by a method comprising preparing an aqueous solution of a capping agent, dissolving a silver precursor in the aqueous solution of the capping agent and reducing the silver precursor by adding a reducing agent. The capping agent includes polyvinyl alcohol, polyvinyl pyrolidone, or chitosan. The silver precursor may be silver nitrate. The reducing agent may be sodium citrate, sodium borohydride or sodium hydroxide. The aqueous suspension of silver nanoparticles may also be prepared by adding silver nanoparticles in powder or paste form to water.

Alternatively, silver nanoparticles may be dissolved in an aqueous solution of polyvinyl alcohol to prepare the aqueous solution of silver nanoparticles and polyvinyl alcohol. In accordance with an aspect, the silver nanoparticles are capped nanoparticles. The silver nanoparticles may be silver nanoparticle-chitosan composite, silver nanoparticle- polyvinyl alcohol composite or silver nanoparticles-polyvinyl pyrrolidone composite.

The particulate material includes but is not limited to rice husk ash, activated carbon, sand, diatomaceous earth, kaolinite, alumina, zinc oxide, titanium oxide, iron oxide, silica or mixtures thereof. The particulate material has a size in the range of 75 microns to 3.0 mm.

In accordance with an aspect, the particulate material is rice husk ash, having a particle size in range of 75 microns to 100 microns. In accordance with an aspect, the rice husk ash is ground to obtain rice husk ash having a size in the range of 75 micron to 100 microns. In accordance with an aspect, polyvinyl alcohol in the aqueous solution of silver nanoparticles and polyvinyl alcohol is in a range of 5%to 20% weight by weight.

In accordance with an aspect, the aqueous solution of silver nanoparticles and polyvinyl alcohol is mixed with the particulate material in a ratio of 1:3 to 5:6 weight by weight.

In accordance with an aspect, the aggregates of particulate material, silver nanoparticles and polyvinyl alcohol are dried to reduce the moisture content to at least 2% by weight of the aggregates. The aggregates are dried at a temperature of 80°C for a period of at least one hour to obtain the porous granules. To avoid formation of lumps, the aggregates may be mixed intermittently. The dried granules may also be sieved to remove any finer particles.

In accordance with an aspect, the polyvinyl alcohol has a degree of hydrolysis of at least 70%. The polyvinyl alcohol has a molecular weight in a range of 75000 to 145000 Daltons. Specific Embodiments:

A water purification composition comprising porous granules of a particulate material, silver nanoparticles and polyvinyl alcohol matrix, wherein the silver nanoparticles and the particulate material are embedded in the polyvinyl alcohol matrix, the particulate material, polyvinyl alcohol and silver nanoparticles being present in a ratio of 100: 4.5: 0.7 to 100: 10: 0.7 on weight basis, and the porous granules having a size in a range of 0.1 mm to 3 mm.

Such water purification composition(s), wherein polyvinyl alcohol has a degree of hydrolysis of at least 70%.

Such water purification composition(s), wherein polyvinyl alcohol has a molecular weight in a range of 75000 to 145000 Daltons.

Such water purification composition(s), wherein the particulate material is any of rice husk ash, activated carbon, sand, diatomaceous earth, kaolinite, alumina, zinc oxide, titanium oxide, iron oxide and silica.

Such water purification composition(s), wherein the particulate material is rice husk ash having a particle size in range of 75 microns to 100 microns. Such water purification composition(s), wherein the silver nanoparticle is any of silver nanoparticle-chitosan composite silver nanoparticle-polyvinyl alcohol composite and silver nanoparticle -polyvinyl pyrrolidone composite.

Further specific embodiments:

A method for preparing a water purification composition, the method comprising the steps preparing an aqueous solution of polyvinyl alcohol; preparing a mixture of particulate material and silver nanoparticles, mixing the aqueous solution of polyvinyl alcohol with the mixture of particulate material and silver nanoparticles to obtain aggregates of the particulate material, silver nanoparticles and polyvinyl alcohol; and drying the aggregates to obtain the water purification composition comprising porous granules of the particulate material, silver nanoparticles and polyvinyl alcohol matrix, wherein the silver nanoparticles and the particulate material are embedded in the polyvinyl alcohol matrix, and the porous granules have a size in the range of 0.1 mm to 3 mm.

Such method(s), wherein the aqueous solution of polyvinyl alcohol has a concentration in a range of 5 to 20% weight by weight.

Such method(s), wherein the silver nanoparticles is any of silver nanoparticle-chitosan composite and silver nanoparticle-polyvinyl alcohol composite.

Such method(s), wherein the aqueous solution of polyvinyl alcohol and the mixture of particulate material and silver nanoparticles are mixed in a ratio of 1:3 to 5:6 weight by weight.

A method for preparing a water purification composition, the method comprising the steps of: preparing an aqueous solution of silver nanoparticles and polyvinyl alcohol; mixing the aqueous solution of silver nanoparticles and polyvinyl alcohol with a particulate material to obtain aggregates of particulate material, silver nanoparticles and polyvinyl alcohol; and drying the aggregates to obtain the water purification composition comprising porous granules of the particulate material, silver nanoparticles and polyvinyl alcohol matrix, wherein the silver nanoparticles and the particulate material are embedded in the polyvinyl alcohol matrix, and the porous granules have a size in the range of 0.1 mm to 3 mm.

Such method(s), wherein polyvinyl alcohol in the aqueous solution of silver nanoparticles and polyvinyl alcohol is in a range of 5% to 20% weight by weight. Such method(s), wherein polyvinyl alcohol has a degree of hydrolysis of at least 70%.

Such method(s), wherein polyvinyl alcohol has a molecular weight in a range of 75000 to 145000 Daltons.

Such method(s), wherein the particulate material is any of rice husk ash, activated carbon, sand, diatomaceous earth, kaolinite, alumina, zinc oxide, titanium oxide, iron oxide and silica.

Such method(s), wherein the particulate material is rice husk ash having a particle size in the range of 75 microns to 100 microns.

Such method(s), wherein the silver nanoparticles and the particulate material are in a ratio of at least 7: 1000 weight by weight.

Such method(s), wherein the aqueous solution of silver nanoparticles and polyvinyl alcohol is mixed with the particulate material in a ratio of 1:3 to 5:6 weight by weight.

Such method(s), wherein the aggregates of particulate material, silver nanoparticles and silver nanoparticles are dried to reduce moisture content to at least 2% by weight of the aggregates.

Such method(s), wherein the aggregates are dried at a temperature of 80°C for a period of 2 hours.

The following example(s) of a water purification composition for treatment of water and a method for preparing a water purification composition for treatment of water are exemplary and should not be understood to be in any way limiting.

Example 1:

5 Kg of rice husk ash (particle size of <75 -100 microns) was taken in a sigma mixer to which silver nanoparticle-chitosan composite having 35 grams of silver nanoparticles was added to obtain a mixture of rice husk ash and silver nanoparticles. The quantity of silver in the silver nanoparticle-chitosan composite was calculated using standard silver titration method. To said mixture 1.5 to 4.0 Kgs of aqueous solution of polyvinyl alcohol (PVA), prepared by dissolving 15 Kg of polyvinyl alcohol in 85 Kg of water was added to obtain aggregates of silver nanoparticles, rice husk ash and polyvinyl alcohol. The aggregates were dried at a temperature of 80°C to obtain granules of 0.1 mm to 3 mm diameter. The granules have rice husk ash, polyvinyl alcohol and silver nanoparticles in a ratio of 100: 10: 0.7 on weight basis.

The granules were prepared using different molecular weight polyvinyl alcohol however the ratios were maintained as mentioned above. For each molecular weight polyvinyl alcohol two or more filters containing 70grams of granules were prepared. Filters were challenged with test water with an input bacterial load of more than 1 million bacteria per mL (6 log and above). The output was given a stand-time of 3 hours as well as a 6 hours post filtration time. The output bacterial load was determined through plate counting method and the log reduction was calculated. The filters were challenged with the test water after a predetermined volume of water had passed through the cartridges. Tables 1, discloses the performance of granules comprising fully hydrolyzed 72000 molecular weight polyvinyl alcohol. Table 2, discloses bactericidal performance of granules prepared with partially hydrolyzed 124000 molecular weight polyvinyl alcohol. Table 3 discloses bactericidal performance of granules prepared with fully hydrolyzed 145000 molecular weight polyvinyl alcohol.

Table 1: Bactericidal performance of granules prepared with fully hydrolyzed 72000 Molecular

Weight (MW) Pol vinyl alcohol

Flow Water

Experiment Contact Input- Output- Log

Filter Name Rate Passed

No* Time CFU/ml CFU/ml Reduction

(L)

PVA (-72000 MW) -1 3hr 1180000 0 6.07 5.8 5

PVA (-72000 MW) -1 6hr 1180000 0 6.07 5.8 5

1

PVA (-72000 MW) -2 3hr 1180000 0 6.07 8.75 5

PVA (-72000 MW) -2 6hr 1180000 0 6.07 8.75 5

PVA (-72000 MW) -1 3hr 1200000 0 6.08 5.7 245

PVA (-72000 MW) -1 6hr 1200000 0 6.08 5.7 245

2

PVA (-72000 MW) -2 3hr 1200000 0 6.08 8.3 271

PVA (-72000 MW) -2 6hr 1200000 0 6.08 8.3 271 PVA (-72000 MW) -1 3hr 2580000 0 6.41 4.45 529

PVA (-72000 MW) -1 6hr 2580000 0 6.41 4.45 529

3

PVA (-72000 MW) -2 3hr 2580000 0 6.41 7.5 557

PVA (-72000 MW) -2 6hr 2580000 0 6.41 7.5 557

PVA (-72000 MW) -2 3hr 1620000 0 6.21 8.2 729

4

PVA (-72000 MW) -2 6hr 1620000 0 6.21 8.2 729

PVA (-72000 MW) -1 3hr 1330000 0 6.12 845

5

PVA (-72000 MW) -1 6hr 1330000 0 6.12 845

PVA (-72000 MW) -1 3hr 1320000 0 6.12 6.5 1046

6

PVA (-72000 MW) -1 6hr 1320000 0 6.12 6.5 1046

PVA (-72000 MW) -1 3hr 1500000 0 6.18 2 1268

7

PVA (-72000 MW) -1 6hr 1500000 0 6.18 2 1268

PVA (-72000 MW) -1 3hr 2100000 32.5 4.81 2.5 1779

8

PVA (-72000 MW) -1 6hr 2100000 0 6.32 2.5 1779

PVA (-72000 MW) -1 3hr 1090000 uc 0.00 7.4 2111

9

PVA (-72000 MW) -1 6hr 1090000 0 6.04 7.4 2111

PVA (-72000 MW) -1 3hr 1420000 uc 0.00 3.9 2506

10

PVA (-72000 MW) -1 6hr 1420000 223.5 3.80 3.9 2506

Some experiments were conducted in duplicate. Duplicate experiments have been indicated by numeral , in the Filter Name above. Table 2: Bactericidal performance of granules prepared with partially hydrolyzed 124000 Molecular Weight (MW) Polyvinyl alcohol

Outp

Log Flow Water

Experiment Contact Input- ut-

Filter Name Reduct Rate Passed

No* Time CFU/ml CFU/

ion (L/h) (L) ml

PVA (-124000

3hr 0 6.18 4.4 6 MW) - 1 1500000

PVA (-124000

6hr 0 6.18 4.4 6 MW) - 1 1500000

1

PVA (-124000

3hr 0 6.18 6 5 MW) - 2 1500000

PVA (-124000

6hr 0 6.18 6 5 MW) - 2 1500000

PVA (-124000

3hr 1280000 0 6.11 3.4 246 MW) - 1

2

PVA (-124000

6hr 1280000 0 6.11 3.4 246 MW) - 1

PVA (-124000

3hr 1840000 0 6.26 4.7 251 MW) - 2

3

PVA (-124000

6hr 1840000 0 6.26 4.7 251 MW) - 2

PVA (-124000

3hr 1000000 0 6.00 4.3 511 MW) - 2

4

PVA (-124000

6hr 1000000 0 6.00 4.3 511 MW) - 2

PVA (-124000

5 3hr 1150000 0 6.06 1.7 499

MW) - 1 PVA (-124000

3hr 1810000 0 6.26 2 811 MW) - 2

6

PVA (-124000

6hr 1810000 0 6.26 2 811 MW) - 2

PVA (-124000

7 6hr 0 6.24 1002

MW) - 2 1750000

PVA (-124000

3hr 2100000 5 5.62 3.6 1262 MW) - 2

8

PVA (-124000

6hr 2100000 0 6.32 3.6 1262 MW) - 2

PVA (-124000

3hr 1090000 277.5 3.59 5.1 1560 MW) - 2

9

PVA (-124000

6hr 1090000 1 6.04 5.1 1560

MW) - 2

* Some experiments were conducted in duplicate. Duplicate experiments have been indicated by numeral 2, in the Filter Name above.

Table 3: Bactericidal performance of granules prepared with fully hydrolyzed 145000 Molecular Weight (MW) Polyvinyl alcohol

MW)-2

PVA (-145000

6hr 2760000 0 6.44 4.2 6 MW)-2

PVA (-145000

3hr 2760000 0 6.44 4.4 6 MW)-3

PVA (-145000

6hr 2760000 0 6.44 4.4 6 MW)-3

PVA (-145000

3hr 2760000 0 6.44 4.2 6 MW)-4

PVA (-145000

6hr 2760000 0 6.44 4.2 6 MW)-4

PVA (-145000

3hr 2760000 0 6.44 4 6 MW)-5

PVA (-145000

6hr 2760000 0 6.44 4 6 MW)-5

PVA (-145000

3hr 2110000 0 6.32 6.4 293 MW)-1

PVA (-145000

6hr 2110000 0 6.32 6.4 293 MW)-1

PVA (-145000

3hr 2110000 0 6.32 5.2 265 MW)-2

PVA (-145000

6hr 2110000 0 6.32 5.2 265 MW)-2

PVA (-145000

3hr 2110000 0 6.32 5.6 274 MW)-3

PVA (-145000

6hr 2110000 0 6.32 5.6 274 MW)-3

3hr

PVA (-145000 2110000 0 6.32 5.3 286 MW)-4

PVA (-145000

6hr 2110000 0 6.32 5.3 286 MW)-4

PVA (-145000

3hr 2110000 0 6.32 6.2 288 MW)-5

PVA (-145000

6hr 2110000 0 6.32 6.2 288 MW)-5

PVA (-145000

3hr 0 6.24 273 MW)-6 1750000

PVA (-145000

6hr 0 6.24 273 MW)-6 1750000

PVA (-145000

3hr 0 6.24 249 MW)- 8 1750000

PVA (-145000

6hr 0 6.24 249 MW) - 8 1750000

PVA (-145000

3hr 0 6.24 274 MW)-9 1750000

PVA (-145000

6hr 0 6.24 274 MW)-9 1750000

PVA (-145000

3hr 0 6.24 251 MW) - 10 1750000

PVA (-145000

6hr 0 6.24 251 MW) - 10 1750000

PVA (-145000

3hr 2100000 0 6.32 4.2 544 MW)-3

PVA (-145000

6hr 2100000 0 6.32 4.2 544 MW)-3

3hr

PVA (-145000 2380000 193.5 4.09 5.3 743 MW)-1

PVA (-145000

6hr 2380000 0 6.38 5.3 743 MW)-1

PVA (-145000

3hr 2380000 113 4.32 4.3 752 MW)-5

PVA (-145000

6hr 2380000 0 6.38 4.3 752 MW)-5

PVA (-145000

3hr 1480000 0 6.17 3.7 774 MW)-2

PVA (-145000

6hr 1480000 0 6.17 3.7 774 MW)-2

PVA (-145000

3hr 1480000 0 6.17 3.8 785 MW)-4

PVA (-145000

6hr 1480000 0 6.17 3.8 785 MW)-4

PVA (-145000

3hr 1090000 0 6.04 4.2 820 MW)-3

PVA (-145000

6hr 1090000 0 6.04 4.2 820 MW)-3

PVA (-145000

3hr 1850000 1 6.27 5.05 1020 MW)-1

PVA (-145000

6hr 1850000 0 6.27 5.05 1020 MW)-1

PVA (-145000

3hr 1850000 0 6.27 4.6 1020 MW)-5

PVA (-145000

6hr 1850000 0 6.27 4.6 1020 MW)-5

3hr

PVA (-145000 1450000 13 5.05 2.5 1004 MW)-3

PVA (-145000

6hr 1450000 2.5 5.76 2.5 1004 MW)-3

PVA (-145000

3hr 1200000 223 3.73 4.55 1269 MW)-1

PVA (-145000

6hr 1200000 95.5 4.10 4.55 1269 MW)-1

PVA (-145000

3hr 710000 45.5 4.19 2 1287 MW)-2

PVA (-145000

6hr 710000 5 5.15 2 1287 MW)-2

PVA (-145000

3hr 1580000 155 4.01 4.7 1496 MW)-1

PVA (-145000

6hr 1580000 4.5 5.55 4.7 1496 MW)-1

PVA (-145000

3hr 1580000 19.5 4.91 2.8 1255 MW)-4

PVA (-145000

6hr 1580000 1.5 6.02 2.8 1255 MW)-4

PVA (-145000

3hr 1420000 141.5 4.00 8.5 1553 MW)-6

PVA (-145000

6hr 1420000 1.5 5.98 8.5 1553 MW)-6

PVA (-145000

3hr 1500000 305.5 3.69 4 1531 MW)-5

PVA (-145000

6hr 1500000 13 5.06 4 1531 MW)-5

3hr

PVA (-145000 2200000 301 3.86 3.65 1782 MW)-1

PVA (-145000

6hr 2200000 54.5 4.61 3.65 1782 MW)-1

PVA (-145000

3hr 2200000 410.5 3.73 4 1595 MW)-2

PVA (-145000

6hr 2200000 166.5 4.12 4 1595 MW)-2

PVA (-145000

3hr 2200000 267.5 3.92 3.55 1490 MW)-4

PVA (-145000

6hr 2200000 68 4.51 3.55 1490 MW)-4

PVA (-145000

3hr 1600000 18 4.95 4.9 1247 MW)-3

PVA (-145000

6hr 1600000 9 5.25 4.9 1247 MW)-3

PVA (-145000

3hr 1600000 24 4.82 4 1712 MW)-5

PVA (-145000

3hr 1500000 9.5 5.20 2.35 1880 MW)-1

PVA (-145000

6hr 1500000 1.5 6.00 2.35 1880 MW)-1

PVA (-145000

3hr 1500000 42 4.55 2.45 1695 MW)-2

PVA (-145000

6hr 1500000 1 6.18 2.45 1695 MW)-2

PVA (-145000

3hr 1500000 75.5 4.30 3.35 1925 MW)-6

6hr

PVA (-145000 1500000 5 5.48 3.35 1925 MW) - 6

PVA (-145000

3hr 1500000 55.5 4.43 2.75 1730 MW) - 9

PVA (-145000

6hr 1500000 14.5 5.01 2.75 1730 MW) - 9

PVA (-145000

18 3hr 1350000 526.5 3.41 2.8 1552

MW) - 10

* Some experiments were conducted several times. Experiments have been indicated by numeral 2, 3, 4 etc., in the Filter Name above.

Example 2:

To lOOg of an aqueous solution of polyvinyl alcohol, 0.3 g or more silver nanoparticles in chitosan composite in the form of powder or paste was mixed. In order to improve distribution of silver nanoparticles citric acid was added to polyvinyl alcohol in a concentration of 0.5% weight by weight of the polyvinyl alcohol solution. Alternatively, the silver nanoparticles were also synthesized in aqueous solution to obtain a silver nanoparticle suspension. Polyvinyl alcohol was dissolved in the silver nanoparticles suspension wherein the silver concentration was in the range of 0.3g or more per lOOg. The aqueous solution of silver nanoparticles polyvinyl alcohol was mixed with activated carbon (of known Particle Size Distribution) in the ratio of 1:3 in a sigma mixer to obtain aggregates of silver nanoparticles, particulate material and polyvinyl alcohol. The aggregates were spread on trays and dried at 80° C for one hour or more. To avoid formation of lump, in the course of drying the granules were intermittently mixed. The dried granules were sieved to remove fines if any and were directly used for preparing cartridges. Table 4 discloses the results obtained by using the water purification composition. Table 4: Bactericidal performance of granules comprising activated carbon, silver nanoparticles and polyvinyl alcohol (MW -72000)

Experime Log Water

Contact Input- Output- Flow nt No Filter Name Reductio Passed

Time CFU/ml CFU/ml Rate

n (1)

1 Granules comprising

Silver nanoparticles,

activated carbon and 3hr 1650000 0 6.22 5.5 5 polyvinyl alcohol

matrix

2 Granules comprising

Silver nanoparticles,

activated carbon and 3hr 1850000 32 4.76 5.4 246 polyvinyl alcohol

matrix

3 Granules comprising

Silver nanoparticles,

activated carbon and 3hr 875000 345 3.40 4.8 514 polyvinyl alcohol

matrix

4 Granules comprising

Silver nanoparticles,

activated carbon and 3hr 1620000 107 4.18 3.8 735 polyvinyl alcohol

matrix

5 Granules comprising

Silver nanoparticles,

activated carbon and 3hr 2140000 252.5 3.93 3.1 1502 polyvinyl alcohol

matrix

6 Granules comprising 3hr 1790000 7 5.41 6.8 2310 Silver nanoparticles, activated carbon and

polyvinyl alcohol

matrix

Example 3:

To lOOg of an aqueous solution of polyvinyl alcohol, 0.3g or more silver nanoparticles in chitosan composite in the form of powder or paste was mixed. In order to improve distribution of silver nanoparticles citric acid was added to polyvinyl alcohol in a concentration of 0.5% weight by weight of the polyvinyl alcohol solution. Alternatively the silver nano particles were synthesized in aqueous solution to obtain a silver nanoparticle suspension. Polyvinyl alcohol was dissolved in the silver nanoparticle suspension wherein the silver concentration was in the range of 0.3g or more per lOOg. The aqueous solution of silver nanoparticles polyvinyl alcohol was mixed with sand (of known PSD) in the ratio of 1:3 in a sigma mixer to obtain aggregates of silver nanoparticles, particulate material and polyvinyl alcohol. The aggregates were spread on trays and dried at 80° C for one hour or more. To avoid formation of lump, in the course of drying the granules were intermittently mixed. The dried granules were sieved to remove fines if any and were directly used for preparing cartridges. Table 5 discloses the results obtained by using the water purification composition.

Table 5: Bactericidal performance of granules comprising sand, silver nanoparticles and polyvinyl alcohol

Flow

Experiment Contact Input- Output- Log Rate Water

Filter Name Passed

No Time CFU/ml CFU/ml Reduction (liters/ho (liters) ur)

Granules

comprising

Silver

1 nanoparticle 3hr 2720000 0 6.4 6.15 430 s, sand and

polyvinyl

alcohol matrix

Granules

comprising

Silver

nanoparticle

2 3hr 620000 0 5.8 4.6 541 s, sand and

polyvinyl

alcohol

matrix

Granules

comprising

Silver

nanoparticle

3 3hr 1100000 0 6.0 5.7 788 s, sand and

polyvinyl

alcohol

matrix

Granules

comprising

Silver

nanoparticle

4 3hr 960000 2 5.7 5.3 1529 s, sand and

polyvinyl

alcohol

matrix

INDUSTRIAL APPLICABILITY

The water purification composition comprising particulate material- silver nanoparticles-polyvinyl alcohol matrix effectively removes the microbial content from water. As the water purification composition is in the form of granules that are highly porous, no choking or channeling is observed when the water purification composition is packed in a bed. Moreover, as polyvinyl alcohol is used for granulation, granules formed are stronger and do not disintegrate due to varying water conditions such as pH. The method of making a water purification composition described above is easy to perform and cost effective. The homogeneity of the silver nanoparticles loaded onto the particulate material such as rice husk ash can be maintained and easily controlled by the process disclosed. The silver nanoparticles are mixed with the particulate matter or the polyvinyl alcohol, during the formation of the porous granules resulting in even distribution of the silver nanoparticles in the granules. As the method disclosed is largely a dry process, it is energy efficient and can easily be scaled up.