Microwave-assisted oxidative roasting of molybdenum concentrate to MoO3: process optimization and kinetic analysis

An efficient and environmentally benign route for producing molybdenum trioxide (MoO3) from molybdenum concentrate was developed through microwave-assisted oxidative roasting. The thermodynamic feasibility of the oxidation process was first evaluated, followed by a systematic investigation of the dielectric properties of the constituent phases at elevated temperatures. The results demonstrate that MoS2 exhibits strong microwave absorption behavior, whereas MoO3 and SiO2 are essentially microwave-transparent, enabling selective heating of the sulfide phase and thereby promoting oxidation efficiency. Process parameters, including roasting temperature, holding time, and microwave power-to-mass ratio, were optimized to maximize MoO3 formation. Under optimal conditions of 700 °C, 90 min, and 100 W/g, the roasted product achieved a MoO3 content of 62.39wt%. Kinetic analysis indicates that microwave irradiation significantly lowers the onset temperature of oxidation to approximately 300 °C. In the temperature range of 500–700 °C, the oxidation of molybdenum concentrate by microwaves is governed by internal diffusion, with an apparent activation energy Ea of 33.29 kJ/mol, compared with the activation energy of 137.97 kJ/mol under conventional heating, microwave-assisted roasting markedly reduces the energy barrier and accelerates the reaction kinetics. These findings demonstrate the strong potential of microwave technology for clean, energy-efficient molybdenum extraction and provide valuable kinetic insights for its industrial application.