Title of Invention

A PROCESS FOR THE FLOCCULATION OF COLLOIDAL SUSPENSION USING ULTRA LOW CONCENTRATION OF LOW MOLECULAR WEIGHT POLYMER

Abstract

A process for the flocculation of colloidal suspension using a known low molecular weight polymer in ultra low concentration comprising: a) preparing an aqueous suspension of the colloid having a solid content from parts per million to 5% weight; b) adjusting the ionic strength of the suspension to 0.01 to 0.2 M by adding a known alkali metal salt as herein described under stirring; c) adjusting the pH of the suspension to 3 to 11 by adding a known pH modifier as herein described under stirring; d) adding an aqueous solution of a known low molecular weight polymer having molecular weight of 2000 - 450000 g/mol in ultra low concentration of 25 to 6000 ppb under stirring; and e) allowing the colloid to settle.

Full Text

FORM 2 THE PATENTS ACT 1970 (39 of 1970) AND THE PATENTS RULES, 2003 COMPLETE SPECIFICATION (See Section 10; rule 13) TITLE OF THE INVENTION A process for the flocculation of colloidal suspension using ultra low concentration of low molecular weight polymer APPLICANTS TATA CONSULTANCY SERVICES LIMITED, an Indian company having its registered office at 11th Air India Building, Nariman Point, Mumbai 400 021 Maharashtra, India INVENTORS Kalyan Kumar Das and Pradip, both Indian nationals of TATA CONSULTANCY SERVICES LIMITED, an Indian company having its registered office at 11th Air India Building, Nariman Point, Mumbai 400 021, Mumbai 400 021 Maharashtra, India and Ponisseril Somasundaran, of Department of Earth and Environmental Engg. Materials Science & Engg. Langmuir Centre for Colloids and Interfaces, 911 SW Mudd Building, 500 West, 120th Street, Henry Krumb School of Mines,Columbia University, New York, NY 10027, United State of America, US citizen. PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed. ORIGINAL 575/MUM/2000 TECHNICAL FIELD OF INVENTION This invention relates to a process for the flocculation of colloidal suspension using ultra low concentration of low molecular weight polymer. Flocculation is routinely employed in solid/liquid separations, mineral processing, ceramic processing, pulp and paper manufacturing, paints, pigments, chemical processing, water clarification, effluent treatment, waste processing or slurry transport. PRIOR ART Colloidal suspensions are known to settle on their own only at the pzc (point of zero charge) of the colloids. Colloidal suspensions are otherwise known to be flocculated by using polymers. Flocculation of colloids using polymers is a complex process and depends on several process parameters such as solids loadings, particle size, shape, morphology or charge of the colloid; pH of the suspension medium; concentration, ionicity, orientation, conformation or molecular weight of the polymer or the 2 hydrodynamic conditions such as agitation, mode of polymer addition or conditioning time. For the purpose of flocculation of a colloid, a suspension of the colloid is made in a solvent, usually water, followed by addition of the polymer. Prior to addition of the polymer, optionally the pH of the suspension may be adjusted with a pH modifier. The pH value of the suspension and the type and concentration of polymer are chosen by trial and error depending on the nature of the colloidal system such as solids loading. The polymers used may be synthetic, of the cationic type (e.g. polyethylenimine), anionic type (e.g. polyacrylic acid, polystyrene sulfonate) or non-ionic type (e.g. polyethylene oxide, polyvinyl pyrrohdone) or they may be natural polymers (e.g. starch, guar gum). They may be homopolymerc or co-polymers or a combination of polymers. The concentration of the polymers used in industries for flocculation is high i.e. ppm (parts per million) concentrations to a few weight percent (1 weight percent = 10000 ppm) and the polymers also have high molecular weights of the order of one to several millions. The colloidal suspensions contain ppm to ~5% weight of solids, usually 1-2% weight, in particle sizes of 1 nm to 10 urn, usually ~ Ium. High molecular weight polymers are expensive. Moreover their use in high concentrations (tens of ppm to a few 3 ■j weight percent) further makes the process of flocculation expensive. Also use of very high ppm concentrations of polymer may cause crowding of the polymeric segments at the solid-liquid interface in the suspension, thereby leading to dispersion, rather than llocculation of the colloid. When low molecular weight polymers in the molecular weight range of 2000 to 100,000 in tens of ppm to a few weight percent concentration are added to a colloidal suspension, the colloidal suspension is dispersed. Thus low molecular weijjht polymers in ppm levels are used as dispersants. Low molecular weight polymers are not known or reported to have been used in the llocculation of colloidal suspensions. DESCRIPTION OF INVENTION An object of the invention is to provide a process for the llocculation of colloidal suspension by employing low molecular weight polymer in ultra low concentration of ppb. Another object of the invention is to provide a process for the llocculation of colloidal suspension using low molecular weight polymer in ultra low concentration of ppb, which is comparatively cheaper. 4 Another object of the invention is to provide a process for the flocculation of colloidal suspension using low molecular weight polymer in ultra low concentration of ppb, which is efficient. Another object of the invention is to provide a process for the flocculation of colloidal suspension using low molecular weight polymer in ultra low concentration of ppb, which is easy and convenient to carry out. According to the invention there is provided a process for the flocculation of colloidal suspension using a known low molecular weight polymer in ultra low concentration comprising : a) preparing an aqueous suspension of the colloid having a solid content from parts per million to 5% weight; b) adjusting the ionic strength of the suspension to 0.01 to 0.2 M by adding a known alkali metal salt under stirring; c) adjusting the pH of the suspension to 3 to 11 by adding a known pH modifier under stirring; 5 d) adding an aqueous solution of a known low molecular weight polymer having molecular weight of 2000 - 450000 g/mol in ultra low concentration of 25 to 6000 ppb under stirring; and e) allowing the colloid to settle. Preferably, the solid content in the colloidal suspension is 0.01 to 1 % by weight. The colloidal suspension according to the invention may comprise minerals, synthetic oxides, pulp and paper, pigments, paints, ceramics or refractory materials, preferably solid media such as alumina, titania, zirconia, kaolin, iron oxide or a mixture thereof. The ionic strength of the suspension is preferably maintained at 0.02 to 0.1 M. The alkali metal salt may be sodium or potassium chloride or nitrate. 6 Preferably the pH of the suspension is 3.5 to 7. The pH modifier may be an alkali such as sodium or potassium r hydroxide or an inorganic acid such as nitric acid or hydrochloric acid. The polymer may be polyacrylic acid (PAA), polyacrylamide (PAM) or polystyrene sulfonate (PSS). Preferably a polymer with molecular weight of 2000 to 250,000 g/mol is used. Preferably the concentration of the polymer in the aqueous suspension is 100 to 1000 ppb. According to the invention flocculation of colloidal suspensions is carried out efficiently using low molecular weight polymers in ultra low concentrations of ppb by exercising a judicious selection/control of the ionic strength and pH of the suspension depending on factors such as polymer or colloid. Use of low ppb concentrations of low molecular weight 7 polymer within the defined ionic strengths of the suspension makes flocculation inexpensive having regard to the fact that the cost of electrolyte is low. The process of the invention besides being efficient, is simple, easy and convenient to carry out because it is easy and convenient to make and handle low concentrations of polymer. The following experimental examples are illustrative of the invention but not limitative of the scope thereof. Example 1 A colloidal suspension of alumina [A1203, 0.5% by weight of sample] was prepared by dispersing 1 gram of alumina powder (AKP-15 of Sumitomo Corporation, Japan, particle size 0.7 um, sp. gravity 3.97) in 190 ml water in a beaker. The ionic strength of the suspension was kept constant at 0.03 M NaCl. The suspension was ultrasonicated using a maximum of 75 watts energy and conditioned for 60 minutes on a magnetic shaker using a stirring bar. After the adjustment of pH to 3.5 with HN03, the suspension was further conditioned for a period of 60 minutes as described earlier followed by addition of 10 ml of an aqueous solution of 8 polyacrylic acid such that the concentration of polyacrylic acid in the suspension was 100 ppb. The addition was carried out over a period of 1 minute. (The aqueous solution of polyacrylic acid was prepared by appropriately diluting a 25% aqueous solution of 50,000 g/mol polyacrylic acid polymer of specific gravity 1.25, of Polysciences, USA). After the addition of the polymer solution, the suspension was further stirred and allowed to settle for 45 seconds before removing a fixed amount (40% by volume) by suction. The top and bottom portions were filtered, dried and weighed separately. The efficiency of flocculation was 90% as expressed in terms of weight percent settled in the beaker. The procedure of Example 1 was followed by varying different parameters. The polymers used were commercially available. The results were as follows. 9 10 11 12 MW = Molecular weight of the polymer Cone. = Concentration of the polymer I.S = Ionic strength of the suspension Eff. = Flocculation efficiency Barring examples 8, 12, 14, 15 and 18 and on comparing example 6 with the remaining examples, particularly example 5, it is clear that maintenance of ionic strength using electrolyte dramatically improved flocculation. In the absence of any electrolyte i.e. at ~ 10'6 M or less ionic strength, poor flocculation was observed using even high concentration of polymer. Barring example 6, on comparing the remaining examples, particularly examples 8 to 11 and 12 & 13 and 19 & 20, it is clear that efficiency of flocculation increased with ionic strength. Barring examples 6, 8, 12, 14, 15 and 18, on comparing the remaining examples, particularly example 16 with example 17 it is clear that 13 with an increase in ionic strength, the concentration of polymer (in ppb) required may be reduced to achieve higher efficiency. 14 We Claim : 1) A process for the flocculation of colloidal suspension using a known low molecular weight polymer in ultra low concentration comprising: a) preparing an aqueous suspension of the colloid having a solid content from parts per million to 5% weight; b) adjusting the ionic strength of the suspension to 0.01 to 0.2 M by adding a known alkali metal salt as herein described under stirring; c) adjusting the pH of the suspension to 3 to 11 by adding a known pH modifier as herein described under stirring; d) adding an aqueous solution of a known low molecular weight polymer having molecular weight of 2000 - 450000 g/mol in ultra low concentration of 25 to 6000 ppb under stirring; and e) allowing the colloid to settle. 2) A process as claimed in claim 1, wherein the solid content in the colloidal suspension is 0.01 to 1 % by weight. 15 3) A process as claimed in claim 1 or 2, wherein the colloidal suspension is alumina, 4) A process as claimed in claim 1 or 2, wherein the colloidal suspension is Zirconia. 5) A process as claimed in claim 1 or 2, wherein the colloidal suspension is titania. 6) A process as claimed in anyone of claims 1 to 5, wherein the polymer is polyacrylic acid. 7) A, process as claimed in anyone of claims 1 to 5, wherein the polymer is pclyacrylamide. 8) A process as claimed in anyone of claims 1 to 5, wherein the polymer is polystyrenesulfonate. 16 9) A process as claimed in anyone of claims 1 to 8, wherein the polymer has a molecular weight of 2000 to 250000 g/mol. 10) A process as claimed in any one of claims 1 to 9, wherein the aqueous solution of the polymer is in concentration of 100 to 1000 ppb. 11) A process as claimed in any one of claims 1 to 10, wherein the pH of the suspension is 3.5 to 7. 12) A process as claimed in any one of claims 1 to 11, wherein the ionic strength of the suspension is 0.02 to 0.1 M. 13) A process for the flocculation of colloidal suspension using a known low molecular weight polymer in ultra low concentration substantially as herein described particularly with reference to the Examples 1 to 5, 7, 9 to 11, 13,16, 17, 19 to 22. Dated this 20th day of June 2000 (Arindam Paul) of DePENNING & DePENNING Agent for the Applicants 17

Documents:

575-mum-2000-cancelled pages(13-9-2006).pdf

575-mum-2000-claims(granted)-(13-9-2006).doc

575-mum-2000-claims(granted)-(13-9-2006).pdf

575-mum-2000-correpondence 1(15-9-2004).pdf

575-mum-2000-correpondence 2(13-9-2006).pdf

575-mum-2000-correspondence(ipo)-(16-3-2007).pdf

575-mum-2000-form 1(13-9-2006).pdf

575-mum-2000-form 1(22-6-2000).pdf

575-mum-2000-form 13(18-7-2006).pdf

575-mum-2000-form 19(29-9-2003).pdf

575-mum-2000-form 2(granted)-(13-9-2006).doc

575-mum-2000-form 2(granted)-(13-9-2006).pdf

575-mum-2000-form 26(22-6-2000).pdf

575-mum-2000-form 3(13-9-2006).pdf

575-mum-2000-form 3(22-6-2000).pdf

575-mum-2000-form 5(13-9-2005).pdf

575-mum-2000-form 6(15-9-2004).pdf

575-mum-2000-form 6(8-9-2004).pdf

575-mum-2000-power of attorney(18-7-2006).pdf