Effect of processing parameters on the microwave assisted aluminothermic reduction of molybdenite

Abstract

In this work, the microwave assisted aluminothermic reduction of molybdenite (MoS2) was first demonstrated, and then the reaction was optimized using different processing parameters. A self-sustainable combustion front was readily induced in a compressed stoichiometric mixture of MoS2 and Al using microwave ignition. However, the reduction reaction (3MoS2 + 4Al = 3Mo + 2Al2S3) could not be fully completed mainly due to the rapid progress of the combustion front and insufficient available Al to fully reduce MoS2. A leaching process in HCl was also adapted to remove the Al2S3 byproduct and unreacted aluminum. Moreover, the effect of compaction pressure, excess Al and mechanical activation was further investigated to optimize the aluminothermic reduction reaction. Adding excess Al over the stoichiometric ratio shifted the reaction toward producing more Mo metal with lower retained MoS2. While the effect of compaction pressure on the reaction products was found to be negligible, it could affect the ignition temperature and the propagation rate of the combustion front. Mechanical activation had two crucial effects on the aluminothermic reduction of MoS2: decreasing the ignition temperature and increasing the reaction progression. A mechanically activated MoS2/Al powder mixture, which was prepared by 30 min ball milling with 0.5 mol excess Al and compressed at 70 MPa, exhibited the best overall efficiency for aluminothermic reduction of MoS2 to produce Mo metal.