Acid leaching–extraction–circulation process based on Mo(VI) coordination with H3PO4 to efficiently extract molybdenum from different components of molybdenum calcine

Abstract

Ammonia nitrogen wastewater generated during the ammonia decomposition of molybdenum calcine causes serious environmental pollution. To address this issue, a novel acidic leaching–extraction–circulation process is proposed to efficiently extract molybdenum (Mo) from different molybdenum calcine components (MoO2, MoO3, and CaMoO4). This process differs from traditional alkali leaching methods as it relies on the coordination of Mo(VI) with H3PO4 to yield soluble H3PMo12O40 while adding sulfuric and nitric acids to achieve the efficient one-step leaching of complex raw ores. The addition of sulfuric acid not only enhances the oxidation of nitrate ion, effectively leading to the co-leaching of MoO2, which cannot be directly complexed by phosphoric acid, but also results in the decomposition of molybdophosphoric heteropoly acid into H3PO4 for cyclic leaching, thus reducing the production cost. Since most of the Mo in acidic lixivium is present as MoO22+ due to the depolymerization of H3PMo12O40, the acidic extractant P507 is employed to extract Mo in the organic phase via cation exchange with MoO22+. The H+ released during the extraction hinders the conversion of MoO22+ to PMo12O403– and regenerates sulfuric acid in the raffinate, which can be reused in cyclic leaching. This study provides an effective and environmentally friendly approach for the industrial extraction of Mo.