GB826770A - Process of coagulating aqueous dispersions of finely divided solids and coagulants for use in such process - Google Patents

Abstract

An aqueous solution of a polymer, formed by condensation in aqueous solution of an alkylene polyamine with a halohydrin which contains either (i) two or more chlorine, bromine or iodine atoms, or (ii) one chlorine, bromine or iodine atom and one epoxy group, the condensation being conducted so that a thickening short of gel formation occurs, is employed as a coagulant of aqueous suspensions of finely divided solids (see Group I). The alkylene polyamine may be a compound of formula H2N(CnH2nNH)xH wherein n is an integer and x is one or more. Amines specified are ethylene, and 1,2- and 1,3-propylene diamines, diethylene triamine, triethylene tetramine, tetraethylene pentamine, and polypropylene and polybutylene polyamines. The halohydrins mentioned are alpha-dichlorohydrin, dibromohydrin, diiodohydrin, epichlorohydrin and epibromohydrin. The polymer may be one whose 20% aqueous solution of pH about 12.6 has a viscosity of 7-200 c.p. at 75 DEG F. The preparation of aqueous solutions of tetraethylene pentamine/epichlorohydrin condensation polymers with softened water is described in Examples (1) and (2). Compositions of the polymers in aqueous solution with one or more of the following are described: sodium aluminate, bentonite, alum, iron sulphate, saponite, lime, soda ash, soda, H2SO4, NaOH, KOH and anionic polymers including polyacrylic acid, sodium polyacrylate, polymethacrylic acid, polystyrene sulphonic acid, polyacrylamide, partially hydrolysed acrylamide, polyvinyl pyrrolidone, and polyvinyl alcohol.ALSO:Aqueous suspensions of finely divided solids are coagulated by adding an aqueous solution of a polymer formed by condensation in aqueous solution of an alkylene polyamine with a halohydrin which contains either (i) two or more chlorine, bromine or iodine atoms or (ii) one chlorine, bromine or iodine atom and one epoxy group, the condensation being conducted so that a thickening short of gel formation occurs. The coagulation process may be applied (a) to turbid naturally occurring waters in order to free them of suspended matter and render them suitable for industrial use, (b) to turbid waters produced by treating hard water with precipitants for the hardness components (such precipitants being, for example, disodium phosphate, lime, soda ash, sodium aluminate or mixtures of these), (c) to sewage waters and (d) to industrial waste waters such as phosphate mine waters, coal washing waters, clay suspensions and calcium carbonate suspensions. The alkylene polyamine may be a compound of formula H2N (CnH2nNH)x H wherein n is an integer and x is one or more. The halohydrins mentioned are alpha dichlorohydrin, dibromohydrin, diiodohydrin, epichlorohydrin and epibromohydrin. The alkylene polyamine/halohydrin polymer may be employed for coagulation in conjunction with another coagulant such as sodium aluminate, clays (e.g. bentonite), alum, iron sulphate, high molecular weight water-soluble anionic polymers, acid, lime, or a blend of any two or more of these. The high molecular weight water-soluble anionic polymers have a molecular weight of at least 10,000, have a structure derived by the polymerization of at least one mono-olefinic compound through the aliphatic unsaturated group, and contain a plurality of anionic groups such as carboxyl and sulphonic acid groups or carboxylite salt groups, and may be copolymers. Examples of such anionic polymers are polyacrylic acid, sodium polyacrylate, polymethacrylic acid and polystyrene sulphonic acid. In addition to these anionic polymers, polypolar polymers and mixed polyanionic/polypolar copolymers may also be employed. Such polymers are, for example, polyacrylamide, partially hydrolysed polyacrylamide, polyvinylpyrrolidone and polyvinyl alcohol. In examples, (A) tetraethylene pentamine/epichlorohydrin condensation polymer (Polymer X) is used to coagulate the suspended solid matter in turbid waters which are water containing molybdenum ore tailings, phosphate mine water or water softened by heating with caustic soda and disodium orthophosphate; (B) raw sewage or raw sewage water is coagulated using Polymer X in conjunction with alum or in conjunction with bentonite and sodium aluminate (with or without lime); (C) water is coagulated with polymer X in conjunction with alum (with or without sulphuric acid), ferric sulphate or bentonite; (D) water, which has been softened with lime and soda in the presence of clay and tannin, is coagulated with Polymer X in conjunction with sodium aluminate and bentonite; (E) water is treated with Polymer X, lime, soda, bentonite and sodium aluminate in conjunction; and (F) salt petroleum refinery water from the desalting of petroleum is coagulated with Polymer X in conjunction with bentonite and sodium aluminate.