An insight on the mechanism of efficient leaching of vanadium from vanadium shale induced by microwave-generated hot spots

Microwave heating can rapidly and uniformly raise the temperature and accelerate the reaction rate. In this paper, microwave heating was used to improve the acid leaching, and the mechanism was investigated via microscopic morphology analysis and numerical simulation by COMSOL Multiphysics software. The effects of the microwave power, leaching temperature, CaF2 dosage, H2SO4 concentration, and leaching time on the vanadium recovery were investigated. A vanadium recovery of 80.66% is obtained at a microwave power of 550 W, leaching temperature of 95 & DEG;C, CaF2 dosage of 5wt%, H2SO4 concentration of 20vol%, and leaching time of 2.5 h. Compared with conventional leaching technology, the vanadium recovery increases by 6.18%, and the leaching time shortens by 79.17%. More obvious pulverization of shale particles and delamination of mica minerals happen in the microwave-assisted leaching process. Numerical simulation results show that the temperature of vanadium shales increases with an increase in electric field (E-field). The distributions of E-field and temperature among vanadium shale particles are relatively uniform, except for the higher content at the contact position of the particles. The analysis results of scale-up experiments and leaching experiments indicate high-temperature hot spots in the process of microwave-assisted leaching, and the local high temperature destroys the mineral structure and accelerates the reaction rate.

Automated summary

Microwave heating was used to improve acid leaching in this study. The effects of various factors on vanadium recovery were investigated through analysis and simulation. A vanadium recovery of 80.66% was achieved using microwave heating. Compared to conventional leaching, microwave-assisted leaching increased vanadium recovery by 6.18% and reduced leaching time by 79.17%.