Synergic process of molybdenum recovery and ceramic preparation for clean and efficient utilization of industrial leaching residues

Abstract

Ammonia-leaching residues of roasted molybdenite concentrates are intractable wastes and are mostly stockpiled in factories. Common treatments suffer from low Mo recovery and secondary pollution. This study has developed a synergistic process involving a single-step roasting with the addition of Al₂O₃ and MoO₃ to recover Mo and simultaneously prepare porous refractories from the residues containing 5.6% Mo. The Mo separation efficiency, ceramic properties, and thermal behaviors—including chemical reactions, melting transformations, ceramic structure evolutions, and Mo species migrations—were comprehensively investigated. It was found that the addition of Al₂O₃ facilitated CaMoO₄ decomposition to release volatile MoO₃, thus promoting Mo recovery. The mullite started to form at about 900 °C, grew into whiskers, and further into interconnected clusters, under the catalytic effect of liquid MoO₃ and the sintering effect of glassy melt. Liquid MoO₃ was scattered on the outer surface of whisker clusters, achieving a high separation efficiency of over 98% after roasting at 1300 °C for 150 min. Meanwhile, a ceramic with a high porosity of 64.2% and a high compressive strength of 21.2 MPa was obtained, exhibiting promise for serving as a high-temperature insulation refractory. Overall, this study presents a novel approach for both the profound recovery of Mo and the value-added utilization of gangue minerals derived from CaMoO₄-bearing wastes.