GB1460626A - Purification of water - Google Patents

Abstract

1460626 Purification of water using polymeric biguanides IMPERIAL CHEMICAL INDUSTRIES Ltd 28 April 1975 [22 May 1974] 22782/74 Heading C1C A method for the purification of water which is contaminated by suspended solid matter and micro-organisms, comprises adding to the contaminated water a polymeric biguanide or a salt thereof in amount sufficient to substantially flocculate and precipitate the suspended solid matter and to kill at least some of the microorganisms, the polymeric biguanide in its free base form having a recurring polymer unit represented by the formula wherein X and Y, which may be the same or different, represent bridging groups respectively, n and m having values from 3 to 12, or X and Y represent other bridging groups in which, taken together, the total number of carbon atoms directly interposed between the pairs of nitrogen atoms linked by X and Y is from 10 to 16, and wherein the polymeric biguanide comprises a mixture of polymers in which the individual polymer chains are of different lengths, the number of individual polymer units taken together in any polymer chain being from 3 to 80, and wherein the groups terminating the polymer chains, which groups may be the same or different, are selected from -NH 2 , -NH-C(=NH)-NHCN and wherein R 1 is hydrogen or a substituted or unsubstituted aliphatic, cycloaliphatic, araliphatic or aromatic hydrocarbon radical containing from 1 to 18 carbon atoms and R 2 is a substituted or unsubstituted aliphatic, cycloaliphatic, araliphatic or aromatic hydrocarbon radical containing from 1 to 18 carbon atoms. Purified or potable water can be obtained from natural waters, e.g. lake or river waters, and also from water used to wash vegetables such as leeks, lettuce and carrots. Poly-(hexamethylene biguanide) or its hydrochloride is the preferred chemical, used at a concentration of 0À0001 to 1À0% by weight based on the weight of water.