CHEMISTRY OF CR(VI) SOLVENT-EXTRACTION USING TRI-N-OCTYLAMINE

Experiments were carried out to clarify the mechanism for the extracti on of Cr(VI) from sulfate-containing aqueous solutions using tri-n-oct ylamine (TOA). The results were consistent with a two-step reaction me chanism, initially involving complexation of TOA with bisulfate follow ed by substitution of bisulfate with bichromate in the complex. Experi mental results support the contention that the first step only occurs with bisulfate and not with sulfate, explaining why the extraction dec reases rapidly for initial pH values above 2. The equilibrium coeffici ent for the overall extraction reaction was determined to be 10(6).