Membranes for sepn. of liquids by evaporation

摘要

New membrane for the separation of liquids by evaporation consists of a polymeric substance which in its main chain contains a glycosidic skeleton comprising cationic groups and/or anionic groups of which at least some form a salt with counter-anions and/or counter-anions. Pref. anionic groups are sulphate ester, sulphonic acid, carboxylic acid, phosphate ester and phosphonic acid residues. Preferably, 9-70 mol % of the anionic groups are bound to polyvalent metal ions, so as to effect cross-linking. Pref. cationic groups are ammonium groups and groups in which an N-atom is coordinated with a polyvalent metal ion. Preferred polymeric substances are salts of alginic acid or alginic acid derivs., salts of anionic cellulose derivs., salts of chitosan or chitosan derivs., and salts of cationic cellulose derivs. In a new process for evaporation by means of a membrane, a mixture of water and an organic liquid or a mixture of two organic liquids is separated by evaporation using a separating membrane as defined above which has been dried to a water content not exceeding 25 wt.%.