Flocculation of suspended solids from aqueous media

Claim 1

An improved method for flocculating suspended clay particulate solids from an acidic aqueous medium having a pH of less than about 3 and for increasing the clarity of said aqueous medium which comprises initially (1) contacting the aqueous medium with a flocculating amount of a water-soluble polymer having an anionic character comprising, in polymerized form, from about 50 to about 80 weight percent acrylamide and from about 20 to about 50 weight percent 2-acrylamide-2-methylpropane sulfonic acid or alkali metal salt thereof; followed by (2) contacting the suspension with a clarifying amount of a water-soluble polymer having comprising, in polymerized form, from about 10 to about 99 weight percent acrylamide and from about 1 to about 90 weight percent of a quaternized nitrogen-containing ethylenically unsaturated monomer wherein said polymer having an anionic character contains a molar concentration of sulfonate moieties sufficient to provide flocculant activity in the acidic aqueous medium that is greater than the flocculant activity of an acrylamide/acrylic acid polymer having the same molecular weight and a molar concentration of carboxylate moieties similar to the molar concentration character, flocculating said suspended clay particulate solids, and settling the flocculated clay particulate solids from said aqueous medium.