| abstract |
The process of separating citric acid and/or isocitric acid and their salts from aqueous solutions containing said acids or their salts, and especially from fermentation solutions, consists in contacting said solutions under pressure with a permselective membrane. The material composing said membrane has introduced thereinto acid or basic groups so as to yield membranes of predetermined swelling power. Preferred membranes are those consisting of polyimide or polyamide polycondensation products which are modified by acid or basic groups, of polysulfones modified by acid groups, or of vinyl polymers modified by acid or basic groups. Adjustment of the starting solutions to a pH lower than 3.0 is advantageously effected by means of polyvinylsulfonic acid. |