Direct preparation of micro and nano antimony trioxide using antimony concentrate via microwave roasting: Mechanism and process

Antimony sulfide (Sb2S3) concentrate is the main source for the production of antimony oxides and metallic antimony. Few researches have focused on preparing Sb2O3 crystals and Sb2O3 nanomaterials from minerals directly. In this research, a clean, short, direct preparation of Sb2O3 crystals and nanomaterials via microwave oxidation roasting using antimony sulfide minerals is investigated. A thermodynamic analysis of oxidation and the dielectric properties of antimony sulfide minerals reveal the reaction trends and heating characteristics of microwave oxidation roasting. The experimental results show that the Sb content within the crystalline product is 97.05% under roasting conditions of 400 °C for 45 min under an air flow of 0.8 m3/h. During roasting, the phase transformation follows the order of Sb2S3→Sb2O3→Sb2O4. The oxidation mechanism shows that the microwave field enhances the molecular and Knudsen diffusion, increasing the reaction entropy. The rapid, selective microwave roasting favors rapid primary nucleation and the formation of Sb2O3 crystals. For volatile components, directional growth of Sb2O3 nanorods and microspheres with nanostructures is enhanced under the alternating electromagnetic field. This clean and innovative method gives a promising and feasible technology for efficient utilization of minerals to prepare micro and nanomaterials.