Experiment on Back-extraction of Cr(Ⅲ) in Acidic Extractant by Alkali

Back-extraction of chromium from acidic extractant is difficult, whose recovery is generally low. This paper studies the back -extraction of Cr (Ⅲ) in acidic extractant by alkali based on the different complexing speciation of Cr (Ⅲ) and OH^- in various acidic solution. The optimized conditions for P204 and P507 extractants are as follows: O/A is 1, sodium hydroxide concentrations are 0.5 mol/L and 2 mol/L, separately; back-extraction times are 10 and 20 min, and the recoveries reach 98.3 % and 98.8% after 4 steps back -extraction at room temperature.