A new process for separation of chromium from iron by selective phosphate precipitation

The selective phosphate precipitation process is proposed for the effective Cr/Fe separation in acidic solutions after the pretreatment of Fe³⁺ reduction. The effects of dosage of Na₃PO₄ as the precipitant, the initial pH, reaction temperature and time on Cr/Fe separation are experimentally studied. The optimal conditions are determined as follows: initial pH of 2.0, PO₄^3-/Cr³⁺ molar ratio of 0.375, reaction temperature of 90 ℃, reaction time of 60 min. Under the above conditions, the precipitation of Cr is achieved as 98.53% while that of Fe is only 1.42%. This new process is proved to be applicable to a wide range of Fe concentration of the solutions and the impurities, such as Cu²⁺, Zn²⁺, Ni²⁺ and Cl^- have no obvious effects on the selective precipitation of Cr, which provides a new alternative process for the separation and resourcelization of Cr from Cr^-containing materials.