GB1401307A - Method of thickening solids in aqueous waste - Google Patents

Abstract

1401307 Flocculating solids NALCO CHEMICAL CO 12 Sept 1972 [22 Nov 1971 23 Nov 1971 2 Feb 1972] 42342/72 Heading C1C A method of thickening or dewatering solids in aqueous wastes (e.g. sewage, coal mining slurry or pulp mill sludge) comprises adding to the waste an aqueous solution of a water-soluble addition polymer prepared by the inverse emulsion technique and separating the resultant flocculated solids, e.g. by settling or vacuum filtering. The polymeric solution is prepared by (a) forming a water-in-oil emulsion from a water phase containing one or more ethylenically unsaturated monomers, an inert hydrophobic liquid and an emulsifying agent (b) polymerizing the monomer(s) to produce a latex, the polymerization being initiated by free radicals produced from free-radical yielding catalysts at elevated temperature, or by high energy radiation or U.V. radiation and (c) producing the polymeric solution from the polymer-containing emulsion, e.g. by using water together with cationic, anionic or non- ionic surfactants (many listed), agitation, heat, pH shift and/or electric fields. The preferred polymers are homopolymers of acrylamide, acrylic acid and dimethylaminoethyl methacrylate and copolymers of acrylic acid or acrylamide with sodium acrylate, dimethylaminoethyl methacrylate or dimethyl sulphate quaternary salt of the last mentioned compound. The hydrophic solvent may comprise one or more hydrocarbons or substituted hydrocarbons, e.g. benzene, toluene, xylene, mineral oils, kerosenes, naphthas and petrolatums. The emulsifier may be hexadecyl sodium phthalate, sorbitan monooleate or monostearate, cetyl or stearyl sodium phthalate or metal soaps. The free radical yielding initiator may be benzoyl peroxide, lauroyl peroxide, 2,2<SP>1</SP> azobies (isobutyronitrile) or potassium persulphate.