SOLVENT-EXTRACTION OF CHROMIUM(III) WITH BIS-(2-ETHYL HEXYL) PHOSPHORIC-ACID IN BENZENE AND OTHER SOLVENTS

The partition of chromium(III) between sulphuric acid solutions and solutions of bis-(2-ethyl hexyl)-phosphoric acid (abbreviated as HDEHP or H2A2) in benzene has been investigated as a function of the contact time, the acidity of the aqueous phase, temperature and the concentrations of the extractable metal, sulphate, nitrate and acetate ions and the extractant. The extraction ratio has been found to increase with decreasing cation and sulphate ion concentration, with increasing extractant concentration and pH upto about 4.5 at which extraction levels off. The extraction was found to be independent of NO3- and Ac- ion concentration. From the temperature dependency data, the enthalpy change of extraction has been calculated to be ΔH = 15.73 Kcal/mole. From these data the equation for the extraction reaction has been suggested as: (Cr(OH)j)3-j++1.5 H2A2=CrA3+jH2O+(3-j)H+ where, j = 0 to 3. The diluent effect has also been studied. © 1979.