Eco-friendly chromium recovery from hazardous chromium-containing vanadium extraction tailings via low-dosage roasting

The Cr recovery from the Cr-containing tailings of vanadium extraction always generates large amounts of hazardous wastewater sludge and solid waste. This work proposed an eco-friendly Cr recovery method based on low-dosage soda roasting for a new kind of Cr-containing tailing, the Mg-based tailing. The low dosage of soda ensures the targeted conversion of Cr-bearing phases in the Mg-based tailing during roasting and minimizes the soda roasting of accompanying phases other than Cr-bearing phases, leading to the minimization of waste discharge. In the optimal condition of low-dosage soda roasting-water leaching, the Cr extraction efficiency is as high as 93.25 %; from the leach liquor, the Cr2O3 product is obtained by Na2S reduction, precipitation, and calcination with total Cr recovery of 92.93 %. For Cr extraction, the soda dosage has been reduced by 20 % while the production rates of hazardous sludge, leach residue, and CO2 have been reduced by 30 %, 18 %, and 20 %, respectively. This work exemplifies the control of targeted phase conversion to minimize hazardous wastes, which provides a novel strategy for eco-friendly resource utilization of hazardous tailings.