The effect of impurity ions on the pH adjustment for vanadium-bearing acid leaching solution by selective electrodialysis

Abstract

Leaching of vanadium shale with sulfuric acid results in a vanadium acid leaching solution with low pH and many impurity ions. Monovalent selective electrodialysis was employed to adjust the pH of the acid leaching solution by recovering the sulfuric acid. The results demonstrated that CIMS monovalent selective cation exchange membrane had good performance in separating H+ and VO2+ for various vanadium shale acid leaching solutions without Fe3+. The effect of the concentration of impurity ions was investigated. Under the optimum concentration of impurity ions, The treatment time was 125 min, the V rejection ratio reached 98.06%, the water loss rate was controlled at 5.25%, and the pH was adjusted from 0.08 to 1.8. Mg2+ had the best optimization effect on vanadium rejection. Al3+ had the best optimization effect in reducing water loss. F− had the best optimization effect on the treatment time. Meanwhile, the effect of impurity ions on the pH adjustment of acid leaching solution was discussed qualitatively. SEM-EDS analysis confirmed that Fe3+ fouled the membrane and caused the loss of vanadium. Since Fe3+ and PO43− in the acid leaching solution formed FePO4 precipitates. Selective electrodialysis was used to treat vanadium-bearing acid leaching solution, the pH could meet the requirements of separation and purification without consuming any reagent. This process is clean and efficient, and the recycled acid is reused without producing waste water or residue.