Process and Kinetics of Preparing Ammonium Molybdate from Molybdenum Concentrate by Microwave Roasting-Ammonia Leaching

On the basis of previous work, this paper systematically investigates the influence parameters and leaching kinetics of the ammonia leaching process of molybdenum calcine obtained by microwave roasting. The conditions of the ammonia leaching process of calcined molybdenum were optimized by changing the parameters of ammonia concentration, solid–liquid ratio, and leaching temperature. The results show that, when the concentration of ammonia was 25%, the mass of calcined molybdenum and the volume of ammonia were 1/2 g/ml, the leaching temperature was 75°C, and the leaching time was 60 min, the leaching efficiency of molybdenum can reach 91.74%, and the content of ammonium molybdate in the leaching product was 97.23 wt.%. In the leaching process, MoO₃ in the solid phase is dissolved by ammonia to form ammonium molybdate, which conforms to the shrinking core model. The activation energy of the reaction is 57.8 kJ/mol and the rate control step is determined by the mixed model of chemical reaction and product layer diffusion. The apparent rate equation is expressed as: \(\frac{1}{3}\ln \left( {1 - x} \right) + \left( {1 - x} \right)^{{ - \frac{1}{3}}} - 1 = 14.97\omega_{{{\text{ammonia}}}}^{2.004} (L/S)^{ - 2.44} e^{{\frac{ - 57800}{{{\text{RT}}}}}} t\) $\frac{1}{3}ln\left(1-x\right)+{\left(1-x\right)}^{-\frac{1}{3}}-1=14.97{\omega }_{\text{ammonia}}^{2.004}{(L/S)}^{-2.44}{e}^{\frac{-57800}{\text{RT}}}t$ .