Separation of Rhenium and Molybdenum from Simulated Leachate by L35-(NH 4 ) 2 SO 4 Aqueous Two-Phase System

A green aqueous two-phase system (ATPS) using L35, a difunctional PEO-PPO-PEO triblock copolymer surfactant (HO(EO)11(PO)16(EO)11H), was developed for the selective extraction of Re(VII) and Mo(VI). The effects of pH, temperature, L35 concentration, (NH4)2SO4 concentration, and extraction time were systematically investigated. The results showed that pH played a critical role on the separation of Re(VII) and Mo(VI). At pH 7.0, molybdenum was almost completely transferred into the salt rich phase. Increasing temperature suppressed the extraction of molybdenum, whereas the extraction of rhenium rose initially and subsequently decreased. Higher L35 concentrations enhanced the extraction of both metals, and increasing (NH4)2SO4 concentration improved the separation performance. Under optimal conditions (pH 7, 20 wt% L35, 14 wt% ((NH4)2SO4, 313.15 K, 2 h), the extraction efficiency of rhenium reached 99.09% from a mixed solution containing 0.4 wt% Mo and 0.16 wt% Re, with a separation factor of 9815. For a simulated leach solution (6 wt% Mo, 0.1 wt% Re), rhenium extraction reached 98.1% with a separation factor of 465. FT-IR, ESP, and ALIE analyses indicated that the C-O-C groups in the PEO segment of L35 interact with ReO4−. The L35-(NH4)2SO4 ATPS provides an efficient and environmentally friendly strategy for the separation of rhenium and molybdenum.