SOLVENT EXTRACTION OF CHROMIUM(Vl) BY 3-(4-PYRIDYL)-l,5-DIPHENYL PENTANE

The distribution equilibrium of Cr(VI) between an aqueous sulfuric acid solution of potassium bichromate and a nitrobenzene solution of 3-(4-pyridyl)-l,5-diphenyl pentane (PDPP or B) has been studied. Hydrogen chromate ion among several ionic species of Cr(VI) in the aqueous solution is extractable in the present system. The chromium concentration in the organic phase is correlated with the concentrations of hydrogen chromate and hydrogen ion in the aqueous phase with PDPP in the organic phase. The interfacial reaction rate is also obtained and it gives the equilibrium relation by equating the extraction rate with the stripping rate. Results of the freezing point depression of the organic solution and the interfacial tension, obtained for the present system, indicate that the Cr(VT)-PDPP complex in the organic phase might be the aggregation of several molecules of chromate acid and PDPP, and that the complex is surface active. A Cr(VI)-PDPP complex adsorbed at the liquid-liquid interface reacts with hydrogen chromate ion in the aqueous phase consecutively.