Chromium extraction with organic solvents. Part 1. Extraction with DEHPA

Abstract

Chromium and its compounds give toxic and/or hazardous characteristics to all those industrial wastes, solids or liquids, that contain them. Organic solvent extraction is a technique that allows the recovery of chromium contained in these residues. In this work the extraction of Cr(III) from aqueous solutions with solutions of a cationic reactive (DEHPA) in kerosene is studied. In the same way the stripping process was studied. It has been found that Cr(III) and DEHPA react in a 1/1 molar ratio, being the extraction kinetics very fast. Final aqueous phase final pH influence extraction yield, so that it is necessary to work with pH values between 3 and 4. It must be added a modifier (isodecanol) to the organic phase to avoid the formation of a third phase in the stripping process. The concentration of isodecanol has to be higher than 15 %, so the organic phase used was a solution of 12.5 % v/v DEHPA in kerosene and 20 % v/v isodecanol. The stripping process is slow and must be carried out in an oxidant alkalyne medium, thus an aqueous solution of NaOH and H₂O₂ was used. An increase in the concentration of NaOH and H₂O₂ leads to an increase in the stripping yield initially, and becomes stable when concentrations of NaOH and H₂O₂ used are higher than 0.45 N and 4 % v/v respectively.