GB837224A - Improvements in accelerating the sedimentation of solids in turbid aqueous liquids - Google Patents

Abstract

A mixture, which is colloidally soluble in water and which is suitable for addition to turbid aqueous liquids in order to accelerate the sedimentation of solids therefrom (see Group I), comprises (a) a wood ether obtained by reacting wood with chloracetic acid, and (b) a polyvinyl or polyacrylic compound containing carboxylic groups. Component (a) may be employed in the form of the wood ether itself, or the sodium, potassium or ammonium salt thereof. Component (b) may be polyacrylic acid, polymethacrylic acid or a copolymer derived from (i) acrylic or methacrylic acid, and (ii) vinyl methyl ether, acrylamide, methacrylamide, acrylonitrile, acrylic acid esters, maleic acid or styrene. Copolymers derived from three or more monomers may also be employed, while the carboxyl groups may be neutralized to form salts thereof, such as the sodium, potassium or ammonium salts. In addition to components (a) and (b), other water-soluble polymerization or condensation products, for example aldehyde resins or hydroxy-ethylated polyamides, may be incorporated. In the examples, a mixture of (a) wood ether, and (b) vinyl methyl ether/maleic acid or acrylamide/acrylic acid copolymer is described. Specifications 508,547 and 775,805 are referred to.ALSO:The sedimentation of solids in turbid aqueous liquids, especially liquids which have been used for washing coal, is accelerated by introducing into the liquid (a) a wood ether and (b) a vinyl or acrylic homopolymer or copolymer containing carboxylic groups, both (a) and (b) being colloidally soluble in water. The sedimentation is carried out in the absence of inorganic flocculating agents. Additive (a) may be a wood ether formed by the reaction of wood with chloracetic acid of the sodium, potassium of ammonium salt of such a wood ether. Additive (b) may be polyacrylic acid, polymethacrylic acid or a copolymer derived from (i) acrylic acid or methacrylic acid, and (ii) vinyl methyl ether, acrylamide, methacrylamide acrylonitrile, acrylic acid esters, maleic acid or styrene. Copolymers derived from three or more monomers may also be employed, while the carboxyl groups may be neutralized to form salts thereof, such as the sodium, potassium or ammonium salts. In addition to additives (a) and (b), other water-soluble polymerization or condensation products, for example aldehyde resins or hydroxy-ethylated polyamides, may be incorporated. In examples, the sedimentation of coal washing liquors is described using (a) wood ether and (b) vinyl methyl ether/maleic acid or acrylamide/acrylic acid copolymer. The effect of omitting additive (a) or (b) is described. Specifications 508,547 and 775,805 are referred to.