Polycarboxylic acid extraction

摘要

The invention pertains to method for recovering polycarboxylic acid from an aqueous mixture comprising the steps of: providing an aqueous mixture comprising polycarboxylic acid and at least 5 wt.% dissolved halide salt, based on the total weight of water and dissolved material in the aqueous mixture, extracting the polycarboxylic acid from the aqueous mixture into a first organic liquid comprising an organic solvent selected from the group consisting of ketones and ethers, thereby obtaining an organic polycarboxylic acid solution and an aqueous waste liquid comprising the halide salt, and extracting the polycarboxylic acid from the organic carboxylic acid solution into an aqueous liquid, thereby obtaining an aqueous polycarboxylic acid solution and a second organic liquid. The method according to the invention allows a combined purification and concentration step for feed solutions of polycarboxylic acids.