METHOD FOR REMOVING CADMIUM FROM PHOSPHORIC ACID

摘要

Method for removing cadmium from phosphoric acid by the use of the permeation process through a liquid membrane. The method is comprised of: a) formulating an emulsion of the aqueous-in-organic type wherein the dispersed aqueous phase is the re-extraction phase and the organic phase contains an extraction agent of formula (1) wherein R1 and R2 are aliphatic, arylic or aromatic radicals and n can be simultaneously 1 or 0; b) dispersing said emulsion in a phosphoric acid solution; c) removing the aqueous phase which contains the cadmium-free phosphoric acid; and d) breaking the cadmium-laden emulsion to recycle the extraction agent. The obtained phosphoric acid may have a cadmium content of 1.5 ppm and may be used in the production of fertilizers. A preferred emulsion contains bis (2,4,4trimethylpentyl) monothiophosphinic acid as agent for the selective extraction of cadmium.