Highly efficient oxidation of chromium (III) with hydrogen peroxide in alkaline medium

Many technologies have been proposed to oxidize chromium, such as roasting-water leaching technology and hydrometallurgical methods such as pressure oxidative leaching coupled with oxygen, ozone, permanganate and ferrate, but the problems associated with the high temperature, low overall resource utilization efficiency, high energy consumption, and the environmental pollution, still remain unsolved. This paper focuses on the oxidation process of chromium (III) with hydrogen peroxide (H₂O₂) in an alkaline medium. The effect of parameters including dosage of H₂O₂, dosage of NaOH, reaction time, reaction temperature and stirring rate on the oxidation efficiency of chromium were investigated. The oxidation efficiency was significantly affected by the dosage of H₂O₂ and NaOH, reaction time and reaction temperature took second place; last was the stirring rate. Oxidation efficiency was nearly 100% under the optimal conditions: volume ratio of H₂O₂ to mass of Cr₂(SO₄)₃ of 2.4 mL/g, mass ratio of NaOH to Cr₂(SO₄)₃ 0.6 g/g, reaction time of 90 min, reaction temperature of 90 °C and stirring rate of 500 rpm.