WO2019001875A1

WO2019001875A1 - Composition for purification of turbid water

Info

Publication number: WO2019001875A1
Application number: PCT/EP2018/063978
Authority: WO
Inventors: Srinivasa Gopalan Raman; Sumana ROYCHOWDHURY
Original assignee: Unilever NV; Conopco Inc
Current assignee: Unilever NV; Conopco Inc
Priority date: 2017-06-29
Filing date: 2018-05-29
Publication date: 2019-01-03
Anticipated expiration: 2019-12-29
Also published as: BR112019027193A2; MX2019015216A

Abstract

Disclosed is a composition for purification of water comprising: (i) a polymer "A"; and, (ii) an anionic polymer B having weight average molecular weight of at least 0.5 Million Daltons selected from polysaccharides, poly(meth)acrylates, proteins, modified cellulose, and polyacrylamide; where said polymer "A" comprises repeating units α and β in which, "α" is H2C=C(R1 )-C(O)O-(CH2)n-N+(R2)(R3)-(CH2)p-X where - R1 represents a hydrogen atom or a linear or branched C1 to C6 alkyl group; - R2 and R3, independently of each other, represent an alkyl, hydroxyalkyl or aminoalkyl group in which the alkyl group is a linear or branched C1 to C6 alkyl; - n = 1 to 4; - p = 2 to 8; - X represents a negatively charged functional group selected from carboxylate, sulphonate, sulphate or phosphate, and where "β" is H2C=C(R1 )-C(0)0-(CH2)n-N(R2)(R3) in which R1, R2, R3, n and p have the same meaning as assigned in reference to repeating units "α".

Description

COMPOSITION FOR PURIFICATION OF TURBID WATER Field of the invention The invention relates to a composition for purification of impure water, especially turbid water which usually contains particulate impurities.

Background of the invention There is increasing need for efficient and cost effective means to improve the quality of water at the point of use. For example, groundwater is a major source of drinking water at home, especially in developing countries, but groundwater is often contaminated with sediments and other particulates which makes the water turbid. Not only is turbid water less appetizing to drink, but in some cases it contains harmful bacteria and suspended solids which may damage the appliances, such as dishwashers and washing machines which use such water.

One way of removing turbidity is by precipitating the suspended matter using a flocculent like alum (potassium aluminum sulfate dodecahydrate or aluminium sulphate). When turbid water is treated with a flocculent, the electrostatic repellent forces which keep the solids suspended get neutralised and the solids agglomerate to form larger particles called 'floes' which settle slowly to the bottom of the container which holds the water. Disadvantage of using alum as the flocculent is that the performance is substantially compromised at lower temperature and there is poorer efficiency towards attracting organic suspended solids. A relatively large dose becomes necessary.

Adding excess amount of coagulant beyond the charge-neutralization point results in formation of metal coagulant precipitates by sweep flocculation. Some examples are metal hydroxides e.g., AI(OH)3, Fe(OH)3 and FeC . Al-based salts or Fe-based salts are added in sufficient amount so that they form amorphous particles of AI(OH)3 or Fe(OH)3. These amorphous particles entrap suspended solids thereby reducing the turbidity of water. AI(OH)3 or Fe(OH)3 particles with entrapped suspended solids called sweep floes are generally 100 μηη or lower. At this size, it is still difficult to separate them from the water by, e.g. filtration or decantation. Moreover, the rate of settling of the sweep floes is very slow. Although ferric chloride is good at attracting inorganic solids, it is observed that the tendency to attract organic solids is lower. The kinetics can be improved by adding a polymeric flocculent, such as

polyacrylamides (including acrylamide-acrylate copolymers). This type of flocculation includes the addition of a polymer flocculent with molecular weight of at least 100 kDa. These polymers are believed to adsorb on the sweep floes and thereby bring the sweep floes together to form bigger and stronger floes. This phenomenon is known as "bridging flocculation". This bridging mechanism helps increase the settling velocity of the floes for faster purification of water.

US 2014/158633 AA (PSMG LLC) describes a flocculent composition comprising a blend of a particulate polyethylene oxide and a particulate polyacrylamide.

The order of these processes is regulated by the differences in dissolution kinetics; the electrolyte flocculants are readily soluble as compared to the polymeric flocculents.

Betaine-based amphoteric polymers have been applied in detergent compositions. US 8,883,262 BB (RHODIA RECHERCHES AND TECH, 2014) describes a hard surface cleaning composition comprising a combination of (a) a sulphobetaine or carboxybetine zwitterionic polymer and (b) at least one cationic polymer. The US patent further describes hard surface cleaning compositions containing a combination of (a) a phosphobetaine zwitterionic polymer and (b) at least one anionic polymer.

Metal-free flocculation/coagulation compositions are not widely known/used due to their inability to clarify/purify dirty turbid water.

EP 16192021.0 (Unilever, unpublished) discloses a composition comprising an anionic polymeric flocculent (polyacrylamide), an amphoteric polymer having carbo/sulpho betaine units. The application is particularly effective against turbid water.

However, there is still an unmet need for coagulating compositions that are equally or almost equally effective against hard as well as soft water. While turbidity of impure water is a concern for those who need to use it for consumption and other household chores, the hardness, or alternatively the softness of the water may become a factor which limits or restricts the applicability of commercially available compositions/kits for purifying such water.

Summary of the invention

We have determined that a composition comprising a polymeric flocculent (such as polyacrylamide) along with a polymer having repeating units of particular type is able to provide the desired technical effect in soft as well as hard water.

It is believed that the ingredients interact synergistically with each other to purify the turbid water which may be hard or soft. Usually such compositions are effective in either of the situation but not both.

Detailed description of the invention

As used herein the term "comprising" encompasses the terms "consisting essentially of" and "consisting of". Where the term "comprising" is used, the listed steps or options need not be exhaustive.

Unless otherwise specified, numerical ranges expressed in the format "from x to y" are understood to include x and y. In specifying any range of values or amounts, any particular upper value or amount can be associated with any particular lower value or amount.

Except in the examples and comparative experiments, or where otherwise explicitly indicated, all numbers are to be understood as modified by the word "about".

All percentages and ratios contained herein are calculated by weight unless otherwise indicated. As used herein, the indefinite article "a" or "an" and its corresponding definite article "the" means at least one, or one or more, unless specified otherwise.

The various features of the present invention referred to in individual sections above apply, as appropriate, to other sections mutatis mutandis. Consequently, features specified in one section may be combined with features specified in other sections as appropriate. Any section headings are added for convenience only, and are not intended to limit the disclosure in any way. The term 'flocculation' as used herein refers to a process of contact and adhesion whereby the particles of a dispersion form larger-size clusters.

The term "turbidity" as used herein refers to the cloudiness or haziness of a fluid caused by a large number of individual particles.

The unit "NTU" as used herein refers to Nephelometric Turbidity Units (NTU), as measured by the nephelometer, Turbiquant 2100T, manufactured by Merck. The nephelometer is preferably calibrated by using the standard formazin solutions as recommended by the instrument manufacturer. The nephelometer measures the propensity of particles to scatter a light beam focused on them.

The term "inert filler" as used herein refers to particulate component(s) in the composition that do not significantly contribute to the clarification of turbid water. The term hardness of water is the French hardness and indicated as FH.

The term "polyacrylamide" as used herein, unless indicated otherwise, refers to a polymer derived from acrylamide, and derivatives thereof (such as N,N- dimethacrylamide and N-isopropylacrlyamide) and/or methacrylamide and derivatives thereof.

For a given amount of soil present in a litre of water, if the turbidity of such water is measured, then there will be significant difference between the values depending on the hardness of the water. It is observed, in such cases, the turbidity of the soft(er) water is higher than the hard(er) water. It is known that particles of soil have a negative Zeta potential and in soft water there are no counterions to screen these charges. Therefore, the negative potentials keep the particles separated from each other and prevent, or at least significantly reduce, the coalescence of the particles. This leads to more stable colloids which appear more turbid. However, in hard(er) water, the cations eg, (Ca²⁺, Mg²⁺) present in water screen the charges. This reduces the stability of the colloidal particles which manifests itself as lower turbidity.

In accordance with first aspect is disclosed a composition for purification of water. The composition of the invention comprises:

(i) a polymer "A"; and,

(ii) an anionic polymer "B".

Coagulation is generally understood as the process whereby the forces holding the solids in suspension are overcome or neutralized. In other words, the suspended solids are destabilized. Flocculation is the process whereby destabilized suspended solids are brought together to form larger aggregates.

Flocculation results in aggregation of particles or groups of particles into larger groups of particles or floes. Here, flocculation is defined to include the process of particle destabilization and collection into larger aggregates.

Anionic Polymer B The anionic polymer B is selected from polysaccharides, poly(meth)acrylates, proteins, modified cellulose, and polyacrylamide. The weight average molecular weight of the anionic polymer B is at least 0.5 Million Daltons. More preferably it is 1 to 10 Million Daltons. It is preferred that the molecular weight of the anionic polymer B does not exceed 20 Million Da. For avoidance of doubt, the unit Da (Dalton) as used herein refers to atomic mass unit (amu, the less commonly used SI unit). The term anionic polymer, as used herein refers to any type of polymer comprising functional groups that can carry one or more negative charges in aqueous systems, e.g. carboxyl groups, phosphate groups and/or sulphate groups. The anionic polysaccharides can be derived from any source and/or may be obtained by modification, e.g. derivatization, of a polysaccharide. Preferably the anionic

polysaccharides according to the present invention is selected from the group comprising carrageenans, alginates, agar, pectins, modified pectins, gellan gum, xanthan gum, furcellaran, dextran sulphate, modified starches, exopolysaccharides and mixtures thereof. The polysaccharides are non-cellulosic in origin.

Alternatively, and more preferably the polymer B is polyacrylamide. Preferably the polyacryamide is anionic in nature. Alternatively, it is nonionic. Some useful trademarked materials icnklude the Magnafloc® and Dynafloc® grade of polymers.

Examples of suitable poly(meth)acrylate polymers include polyacrylates, acrylate copolymers or alkali swellable emulsion acrylate copolymers (e.g., ACULYN® and CARBOPOL®. A commercially available cross-linked acrylic acid copolymer includes the CARBOPOL® Ultrez series and CARBOPOL® Aqua SF-1 .

Examples of suitable modified celluloses include alkyl or carboxyalkyl celluloses such as hydroxyethyl cellulose, sodium carboxymethyl cellulose, methyl cellulose and hydroxypropyl cellulose. Other preferred modified celluloses include ethyl hydroxyethyl cellulose (EHEC), carboxymethylhydroxyethyl cellulose (CMHEC), hydroxypropyl hydroxyethyl cellulose (HPHEC), methylhydroxypropyl cellulose (MHPC),

methylhydroxyethyl cellulose (MHEC), carboxymethyl methyl cellulose (CMMC), hydrophobically modified carboxymethyl cellulose (HMCMC), hydrophobically modified hydroxyethyl cellulose (HMHEC), hydrophobically modified hydroxypropyl cellulose (HMHPC), hydrophobically modified ethyl hydroxyethyl cellulose (HMEHEC), hydrophobically modified carboxymethylhydroxyethyl cellulose (HMCMHEC), hydrophobically modified hydroxypropyl hydroxyethyl cellulose (HMHPHEC), hydrophobically modified methyl cellulose (HMMC), hydrophobically modified methylhydroxypropyl cellulose (HMMHPC), hydrophobically modified

methylhydroxyethyl cellulose (HMMHEC), and hydrophobically modified carboxymethylmethyl cellulose (HMCMMC) and hydrophobically modified hydroxyethyl cellulose (cationic HMHEC).

It is preferred that the polymer B is water-soluble. By that it means solubiliy of the polymer in water at 25 degC is at least 40 mg/litre.

For a list of other suitable polymers that may be used as polymer B, reference may be to the polymers described in Kirk-Othmer Encyclopedia of Chemical Technology or any other equivalent standard reference book.

Polymer A

The polymer "A" comprises repeating units a and β in which,

"a" is H2C=C(R1 )-C(0)0-(CH2)n-N+(R2)(R3)-(CH2)p-X where

- R1 represents a hydrogen atom or a linear or branched C1 to C6 alkyl group;

- R2 and R3, independently of each other, represent an alkyl, hydroxyalkyl or aminoalkyl group in which the alkyl group is a linear or branched C1 to C6 alkyl;

- n = 1 to 4;

- p = 2 to 8;

- X represents a negatively charged functional group selected from carboxylate, sulphonate, sulphate or phosphate,

and where "β" is H2C=C(R1 )-C(0)0-(CH2)n-N(R2)(R3) in which - R1 , R2, R3, n and p have the same meaning as assigned in reference to repeating units "a". It is preferred that the X is a carboxylate group. Preferably R1 is methyl or ethyl group. Preferably R is methyl group. Preferably R3 is methyl group. It is preferred that n=1 to 3. Preferably p=1 to 3.

While the corresponding groups/substituents in a and β are identical which is the more preferred scenario, it is also possible that they are not identical.

For example, it is preferred that the X is a carboxylate group in a and β, but it is possible that X is a carboxylate group in a and the same X is sulphonate group in β. The negatively charged entity e.g., COO^" or SO3^" are always accompanied by the corresponding cationic counter ion (e.g. Na⁺) so that the charges are balanced, but the counter ion is not included in the structure in this description. The polymer identified as A may or not be commercially available but the same could be easily prepared using methods which are known in the art.

For example, a method for synthesis of a polymer "A" preferred in accordance with the invention is disclosed hereinafter.

The first stage involves synthesis of polydimethylaminoethylmethacrylate (pDMAEMA)

The pDMAEMA polymer is synthesized by free radical polymerization. A 50 % aqueous (w/w) solution of the DMAEMA monomer is stirred at room temperature under nitrogen atmosphere for 30 minutes. 2.5 wt% of potassium persulfate (initiator) is added to this mixture and the temperature is raised to 40 °C. The reaction is carried out for 20 hours (or until completion). The homopolymer is isolated by precipitation in hexane followed by re- dispersion of the sticky polymeric mass in water to obtain a 50% aqueous solution of the polymer.

Functionalization of the above homopolymer to get a polymer A:

The process involves post-polymerization modification of the pDMAEMA polymer, synthesized as above.

A one-pot reaction is done by contacting pDMAEMA with appropriate molar equivalent (variable as per need or requirement) of sodium monochloroacetate. The reaction is carried out at 80 °C for 10 hours (or until complete conversion has been achieved). The final polymer A can be isolated by precipitation in acetone, followed by vacuum drying at 40 °C and re-dispersion in water to obtain a 50% aqueous dispersion of polymer A for further use.

The structure of a preferred polymer A is shown below:

The number of repeating units of repeating units a and β may vary. However, it is preferred that a accounts for 10 to 90 parts by weight of said polymer A, the balance being accounted for by the repeating units β. Further preferably, a accounts for 20 to 80 parts by weight of said polymer A, the balance being accounted for by the repeating units β-

It is preferred that the compositions of the invention comprise from 1 to 20 wt% of the polymer A and from 0.5 to 10 wt% of the polymer B. More preferably the compositions comprise 2 to 10 wt% of the polymer A and 0.5 to 5 wt% of the polymer B.

It is particularly preferred that the compositions of the invention comprise not more than 1 wt% metal-based flocculent based on the total weight of the composition. Preferably and more particularly the metal-based flocculent is a salt comprising at least one of Al or Fe. These compounds are almost always used in compositions for treatment of water, particularly turbid waste water.

Examples include ferrous sulphate, ferric sulfate, aluminium sulfate, aluminium chloride and polyaluminium chlorides.

While it is not necessary, the compositions of the invention preferably further comprise inert inorganic filler having surface area up to 10 m²/g and porosity upto 30 volume %. Suitable examples include of feldspar, sand, calcium carbonate, talc, kaoline, bentonite, attapulgite, alumina or MgO. Surface area measurements can be done using the BET method (Brunauer et al. "Adsorption of Gases in Multimolecular Layers". Journal of the American Chemical Society (1938) 60(2): 309-319.) Porosity can be measured using mercury porosimetry about which reference may be made to the following website. (http://www.micromeritics.com/Repository/Files/Mercury_Porosemitry_Theory_poster_. pdf)

Filler according to the invention may be any inorganic material which preferably is non- reactive to any other ingredients present in the system. It is typically a solid with high density. For the sake of clarity, the filler is not the same as metal based flocculent.

The inorganic filler is preferably selected from natural or synthetic clays and water insoluble inorganic salts. Preferred fillers include feldspar (KAISi308), kaoline, bentonite and Attapulgite, as well as alumina (including silica alumina compositions) and MgO. It is particularly preferred that the compositions of the invention comprise feldspar as the filler.

The inorganic filler is believed to increase the number of particles. The increased particle number density results in faster floe formation. The floes formed are also heavier due to the extra mass of the filler and therefore settle faster. Due to its higher density, it is thought to increase the settling velocity of the floe and improve the overall flocculation kinetics.

The inorganic filler is present in the composition in a concentration of 5 to 95 wt%. The inorganic filler is preferably present in a concentration of 20 to 95 wt%.

It is preferred that dolomite clay (CaMg(CC>3)2) is not used in a large amount, preferably not more than 10 percent by weight of the filler material, more preferably less than 5 percent, still more preferably less than 1 percent, or even 0 percent by weight of the filler material. Dolomite is found to cause effervescence when producing pastes probably reacting with acidic salts present in the formulation. This happens more specifically in presence of moisture or if some formulation ingredient contains water, which is thought to hamper the clarification of some wash or rinse liquors. MgO is reactive to many compounds, as generally known to the skilled person. It may cause exothermic reaction, causing heat formation and may give processing problems in some compositions, especially in the presence of water which in turn affects the efficiency of formulation. 2:1 clays e.g. attapulgite, bentonite are known to retain more liquid in its structure which is thought to be the reason to delay the release of a cationic material in the desired time scale which affects the efficiency of formulation. Therefore, 2:1 clays are less preferred in the compositions according to the invention. Consequently, attapulgite, MgO and/or dolomite are not preferred in a large amount, preferably not more than 10 wt% of the composition.

The most preferred fillers are 1 :1 clays, most preferably kaolin or feldspar. The inert filler preferably has a mass weighted mean particle size in the range of 5 to 500 micrometer, more preferably in the range of 10 to 150 micrometer, most preferably in the range of 50 to 90 micrometer. The inert filler preferably has a surface area of up to 1 m²/g and a porosity of up to 30 vol.%. The composition according to the present invention may be provided, for instance, in the form of a solid (e.g. a powder or tablet), a paste or a gel. In accordance with a preferred embodiment, the water clarification composition is a powder.

The water purification composition preferably is a powder having a mass weighted mean particle size in the range of 10 to 100 micrometers, more preferably in the range of 50 to 90 micrometers.

The process In accordance with a second aspect is disclosed a process for purification of water, said process comprising the steps of:

(i) dosing the composition of the first aspect at a dosage level of 0.2 to 10 grams per litre of water to be purified;

(ii) agitating the water to induce formation of floes; and, (iii) separating, by any means, the floes from the water to obtain purified water.

In the process of the present invention the composition is preferably dosed at a dosage level of 0.2 to 5 grams per litre water. More preferably the dosage level is 0.5 to 5 grams per litre water and most preferably it is 0.5 to 3 grams per litre water.

Dispersing of the composition in the water to be clarified can be achieved by agitating the water, example by stirring. It is preferred that water is agitated for at least 10 seconds, more preferably for 15 to 60 seconds and most preferably for 15 to 50 seconds. Different patterns of stirring may be followed applied, e.g. stirring-pause- stirring or stirring-pause or variations thereof.

The separation of the floes from the water is preferably performed by filtration, decantation and combinations thereof. More preferably the separation of the precipitate from the water is performed by filtration.

Turbidity of the purified water is about 5 and preferably less than 5 NTU.

Typically, the water to be purified may have initial turbidity of about 60 NTU.

The invention is further illustrated by the following non-limiting examples. Examples Example 1 : Purification of water using compositions according to the invention

This experiment was conducted to find out how a composition in accordance with the invention interacts with turbid water and to what extent the turbidity of the water reduces. For this purpose, two compositions in accordance with the invention were prepared. For comparison, three compositions outside the invention were also prepared. Details are shown in Table 1. The weight average molecular weight of anionic polyacrylamide was 6 Million Daltons.

Table 1 lngredient wt% Composition reference code

1 2 3 4 5

Feldspar (filler) 94.0 94.0 94.0 94.0 94.0 pCBMA 4.75 0 2.38 0 0

pDMAEMA 0 4.75 2.37 0 0

pDMAEMA-co-pCBMA (70:30) 0 0 0 4.75 0

(as the Polymer A)

pDMAEMA-co-pCBMA (50:50) 0 0 0 0 4.75 (as the Polymer A)

Anionic polyacrylamide 1 .25 1 .25 1.25 1 .25 1.25 As the Polymer B

Total, including minors 100 100 100 100 100

Note:

• pCBMA means poly(carboxybetaine methacrylate)

• pDMAEMA means poly(dimethylaminoethyl methacrylate)

· In pCBMA-co-pDMAEMA (30:70), the repeating units a account for 30 parts by weight of said polymer A, balance accounted by repeating units β

• In pCBMA-co-pDMAEMA (50:30), the repeating units a account for 50 parts by weight of said polymer A, balance accounted by repeating units β

• Compositions 1 , 2 and 3 were outside the invention; Compositions 4 and 5 are according to the invention

Five litres of water (0 FH) was poured into a glass container. To this water, 1 gram soil was added. The water turned turbid. In another container, five litres of 80 FH water was poured to which the same amount of soil was dosed. The (initial) turbidity of the 0 FH and 80 FH water with the soil in it was 50 NTU and 30 NTU, respectively.

Thereafter, 4.05 g of the concerned composition was dosed into each container. After dosing it, the water was stirred for 20 seconds, followed by a waiting period of 10 seconds, further followed by stirring for 20 seconds. At this point, some floes started forming. The water was left undisturbed for two minutes to allow the floes to settle to the bottom of the container. An aliquot of water from each container was taken and its turbidity was measured using a standard turbidity meter. Lower the turbidity (which is expressed in NTU), better the performance of the composition. In particular, turbidity scores less than 5 NTU were considered superior performance.

The data is summarised in Table 2. Table 2

As can be seen in Table 2, all the compositions outside the invention (1 , 2 and 3) failed to meet the required standards because turbidity of treated/purified water was more than 5 NTU in at least one of the two situations. Even an admixture of the two polymers (Composition Reference 3) did not provide expected results. On the other hand each composition according to the invention met the required standards of turbidity less than 5 NTU and this was an unexpected technical effect, especially considering the fact that, referring particularly to Composition 3, the same effect was not provided by the constituents of the Polymer A (i.e. two separate polymers made up solely by the a and β units).

Example 2: The Effect of metallic ions

The following composition (Reference Code A) was prepared and subjected to tests disclosed under the heading Example 1. The observations are summarised in Table 4.

Table 3

Ingredient wt%

Feldspar (filler) 88.0 pDMAEMA-co-pCBMA (50:50) 4.75 (as the polymer A)

Anionic polyacrylamide 6 Million Daltons 1 .25 As the anionic polymer B

Aluminium chlorohydrate 6.0

Total 100 Table 4

The data indicates that although a substantial amount of Aluminium chlorohydrate was present in the composition, the purified water remained a lot turbid in the case of the experiment with soft water.

Claims

1. A composition for purification of water comprising:

(i) a polymer "A"; and,

(ii) an anionic polymer "B" having weight average molecular weight of at least 0.5 Million Daltons selected from polysaccharides, poly(meth)acrylates, proteins, modified cellulose, and polyacrylamide;

where said polymer "A" comprises repeating units a and β in which,

"a" is H2C=C(R1 )-C(0)0-(CH2)n-N+(R2)(R3)-(CH2)p-X where

- R1 represents a hydrogen atom or a linear or branched C1 to C6 alkyl group;

- n = 1 to 4;

- p = 2 to 8;

and where "β" is H2C=C(R1 )-C(0)0-(CH2)n-N(R2)(R3) in which R1 , R2, R3, n and p have the same meaning as assigned in reference to repeating units "a".

2. A composition as claimed in claim 1 comprising not more than 1 wt% metal-based flocculent based on the total weight of the composition.

3. A composition as claimed in claim 1 or 2 wherein said repeating units a account for 20 to 80 parts by weight of said polymer A, the balance being accounted for by the repeating units β.

4. A composition as claimed in any of claims 1 to 3 wherein X is carboxylate group.

5. A composition as claimed in any of claims 1 to 4 wherein said anionic polymer is polyacrylamide.

6. A composition as claimed in any of claims 1 to 5 wherein said molecular weight is 1 to 10 Million Daltons.

7. A composition as claimed in any of claims 2 to 6 wherein said metal-based flocculent is a salt comprising at least one of Al or Fe.

8. A composition as claimed in any of claims 1 to 7 wherein said composition further comprises an inert inorganic filler having surface area up to 10 m²/g and

porosity up to 30 volume %.

9. A composition as claimed in claim 8 wherein said inorganic filler is at least one of feldspar, sand, calcium carbonate, talc, kaoline, bentonite, attapulgite, alumina or MgO.

10. A composition as claimed in claim 9 wherein said filler is feldspar.

11. Process for purification of water, said process comprising the steps of:

(i) dosing the composition as claimed in any of claims 1 to 10 at a dosage level of 0.2 to 3 grams per liter of the water to be purified;

(ii) agitating water to induce formation of floes; and,

(iii) separating, by any means, the floes from the water to obtain purified water.