A novel membrane-integrated sustainable technology for downstream recovery of molybdenum from industrial wastewater

Abstract

An experimental investigation was conducted to recover and recycle a precious metal (molybdenum) while treating industrial wastewater using a novel membrane-integrated hybrid technology. Hollow-fiber crossflow modules containing ultrafiltration and nanofiltration membranes in the recirculation mode successfully separated 96.5% of the molybdenum from industrial wastewater. The volume of feed wastewater (250 L) was reduced by ∼94%, and the molybdenum concentration was increased from 1.32 to 10.2 g/L using a VNF-1 membrane for its smooth recovery (98.7%) as ammonium molybdate by chemical precipitation under response-surface-optimized conditions of critical parameters of NH4+/Mo ratio (1.32), pH (1.7), temperature (62 °C), and time (15.7 h). Further, ammonium molybdate was converted into MoO3 of high purity (99.4%) using thermal decomposition at 500 °C for 30 min. This is the first proof-of-concept demonstrating the use of a membrane system to recover molybdenum from industrial wastewater to promote a circular economy for recycling and regenerating valuable resources.