Hydrometallurgical separation of Mo and Re from Rhenium-Containing molybdenum calcine for efficient rhenium recovery

Abstract

Rhenium, a strategically critical and highly scarce metal, is typically recovered as a byproduct of molybdenum smelting owing to its limited global reserves. During the oxidative roasting process of molybdenum concentrates, rhenium is primarily distributed in the flue gas scrubbing solution, dust, and molybdenum calcine. However, the high molybdenum content in the calcine, which significantly exceeds that of rhenium, hinders rhenium extraction. The low efficiency of rhenium separation and recovery from molybdenum-containing calcine has long prevented the effective utilization of rhenium-containing molybdenum resources. This article proposes an efficient and eco-friendly hydrometallurgical rhenium-recovery process, involving critical steps, including mixed H₂SO₄/H₃PO₄ leaching and cationic extraction of molybdenum, followed by the cyclic enrichment, anionic extraction, and sodium thiocyanate stripping of rhenium. This methodology facilitates the efficient extraction of rhenium from molybdenum calcine, and the leaching rates of molybdenum and rhenium reach 98 % under optimized conditions. Subsequently, molybdenum was selectively extracted from lixivium using P204, achieving the initial effective separation of molybdenum and rhenium. Thereafter, the P204 raffinate was subjected to cyclic leaching, significantly enriching the rhenium concentration in the raffinate to 42.13 mg/L after seven cycles. Finally, rhenium was selectively extracted from the enriched raffinate using an N263-2-octanol system. Then, the rhenium loaded on N263 was stripped using sodium thiocyanate, achieving the secondary separation of molybdenum and rhenium, with efficient rhenium recovery. This process, characterized by seamless integration and efficient operation, significantly enhances the rhenium extraction efficiency, opening a new avenue for the efficient utilization of rhenium-containing molybdenum calcine.