The interaction between microwave and vanadium-bearing shale: A study on the microwave-assisted leaching mechanism of vanadium

Abstract

Microwave heating technology has received considerable attention for vanadium-bearing shale (VBS) leaching. In this paper, a multi-physics model was established to investigate the electromagnetic response of VBS. Simultaneously, microwave enhanced leaching mechanism was revealed from the perspective of VBS thermal response. The simulation results indicated that the heating time of microwave heating is only 1/18 of that of conventional heating. VBS particles during the leaching process generate high-temperature hotspots (235–261 °C) much higher than the leaching environment (100 °C) due to electric field polarization. Higher temperature leads to faster chemical reaction rate, which affects the diffusion efficiency of products outside the sample over time. The VBS leaching process is mainly controlled by two stages: Microwave energy can reduce the activation energy of the stage Ⅰ from 41.57 kJ/mol to 21.28 kJ/mol and the activation energy of the stage Ⅱ from 59.61 kJ/mol to 43.65 kJ/mol. After microwave irradiation, the surface energy of VBS will increase, and the energy of the leaching system will also be higher, accelerating the erosion and damage of H⁺ on muscovite. Meanwhile, the hydration and hardening phenomenon of gypsum induced by hot spots causes gypsum to transform into hard gypsum on the surface of mica. The growth stress generated during the growth process of hard gypsum will damage the structure of muscovite. The microwave-assisted leaching mechanism of VBS can give more guidance for microwave application.