Cr(VI) recovery from chromite ore processing residual using an enhanced electrokinetic process by bipolar membranes.

Abstract An electrokinetic (EK) system improved by a bipolar membrane (BPM) (BPM-EK) was used to recycle hexavalent chromium (Cr(VI)) from the chromite ore processing residual (COPR) in the form of H 2 CrO 4. The results showed that electrolyte concentrations in anode chamber (AC) and cathode chamber (CC) influenced the cell voltage and that 0.6 mol/L HNO 3 in the AC and 1.0 mol/L NaNO 3 in the CC were the optimal electrolyte concentrations. The current density also affected cell voltage, pH value of the COPR chamber (COPRC), Cr(VI) recovery efficiency, current efficiency (CE), and specific energy consumption (SEC). The optimal current density was 3.0 mA/cm2. Compared to traditional EK processes, a higher CE and a lower SEC were obtained when two and three COPRC were equipped in the BPM-EK system and the Cr(VI) recovery efficiencies of all COPRCs were higher than 82%. With the increase in the number of equipped COPRC from one to two and three, CE increased from 0.60% to 1.67% and 2.30% and SEC decreased from 0.906 to 0.433 and 0.395 kW h/g, respectively. Experimental results showed that the BPM-EK process is an effective method for the recovery of Cr(VI) from COPR. Graphical abstract fx1 Highlights • An improved electrokinetic system was used to recycle Cr(VI) from the COPR. • The current density had some effects on the cell voltage and COPR pH. • The recovery efficiency of Cr(VI) in different system was higher than 82.0%. • The CE increased and the SEC decreased in more COPRCs equipped system. [ABSTRACT FROM AUTHOR]