Removal of iron from Cr-electroplating solution by extraction with di(2-ethylhexyl)phosphoric acid in kerosene

The extraction of iron(III) from aqueous sulphate solution was studied using di(2-ethylhexyl)phosphoric acid (HA) mixed with kerosene. Distribution ratios were investigated as a function of the concentration of sulphuric acid, extractant, metal, hydrogen ion as well as the phase ratio and loading capacity of the extractant. The extracted iron species was suggested as [Fe(HA₂)₃] and the extraction constant was found to equal (9.1 ± 0.5) × 10². The thermodynamic functions calculated from the temperature dependence data referred to the endothermic nature of the extraction process. The method of extraction was successfully applied to remove the iron from the chromium electroplating solution giving purification percent of about 97.5%.