Selective partitioning of tungsten (VI) and molybdenum (VI) through the immobilization of Cyanex272 on resin

The separation of tungsten (W) and molybdenum (Mo) from ammonium tungstate solutions poses a significant challenge in hydrometallurgy due to their nearly identical chemical properties. This study synthesized a novel Cyanex272-immobilized styrene-divinylbenzene (St-DVB) resin to achieve selective partitioning of W and Mo through an extractive chromatography approach. Systematic investigations under static and dynamic conditions identify pH 2.0 as optimal for maximizing Mo adsorption. Thermodynamic analysis revealed an entropy-driven endothermic adsorption mechanism, where elevated temperature enhances Mo selectivity while maintaining favorable kinetics. FTIR, XPS analysis demonstrated the coordination of MoO₂²⁺ with the phosphinic acid groups (–PO(O⁻)) in Cyanex272. Adsorption isotherms aligned with the Langmuir model, indicating that monolayer chemisorption is dominated by ligand-metal coordination. Kinetic analysis revealed pseudo-second-order behavior, with external mass transfer and intraparticle diffusion as sequential rate-limiting steps. Ammonia solution (2.0 mol·L⁻¹) achieved >99.9 % desorption efficiency, enabling resin regeneration and closed-loop resource recovery. Column adsorption demonstrated exceptional performance, removing 99.88 % Mo from industrial-grade feed (100 g·L⁻¹ W, 0.5 g·L⁻¹ Mo) while maintaining effluent Mo below 0.6 mg·L⁻¹, with a separation factor (β_Mo/W) of 9.63 × 10⁵. The purified solution met stringent standards for high-purity ammonium paratungstate (APT) production. By synergizing solvent extraction selectivity with ion-exchange practicality, this method offers an industrially scalable and environmentally sustainable solution to the persistent WMo separation challenge, with potential applications in advanced material manufacturing.