A novel anion exchange method based on in situ selectively reductive desorption of Cr(VI) for its separation from V(V): Toward the comprehensive use of hazardous wastewater

In China, the wastewater produced after vanadate precipitation (AVP wastewater) from industrial vanadium extraction contains toxic V(V) and carcinogenic Cr(VI). When considering environmental protection and wastewater use, V(V) and Cr(VI) must be extracted and separated from the hazardous AVP wastewater. However, separating V(V) and Cr(VI) is difficult because of their highly similar physicochemical properties. Herein, we propose a novel anion exchange method based on the in situ selectively reductive desorption of Cr(VI) to separate and extract V(V) and Cr(VI) using a weak organic reductant (ethanol) to selectively reduce Cr(VI) anions and transform them into Cr3+ cations, while maintaining V(V) in a H2V10O284- anion form. We indicate that the efficient separation of Cr(VI) from V(V) can be attributed to selective Cr(VI) anion reduction via ethanol. We applied this anion exchange method to separate and recover Cr(VI) and V(V) in AVP wastewater with a Cr(VI) recovery of 95.59% and a V(V) recovery of 94.54%. The final Cr2O3 and V2O5 products had a purity of 98.03% and 96.82%, respectively. This study provides novel insights into the simultaneous separation and extraction of analog transition metals and a comprehensive method to use hazardous wastewater.