Cooperative light irradiation and in-situ produced H2O2 for efficient tungsten and molybdenum deposition in microbial electrolysis cells

Abstract

Tungsten (W) and molybdenum (Mo) deposition from ore dressing wastewater is a promising process for recovery of W and Mo with simultaneous ore dressing wastewater treatment, but suffers from consumption of large amount of extraction agent and energy, and generation of excess secondary polluted sludge. Here we reported light irradiation and in-situ produced H2O2 cooperatively enhanced W and Mo deposition in microbial electrolysis cells (MECs), achieving deposition of 81.5 ± 1.7% (W) and 97.2 ± 2.4% (Mo) with a Coulombic efficiency (CE) of 82.5 ± 1.5%. Only 52.0 ± 1.4% (W), 75.7 ± 2.1% (Mo) and 38.6 ± 1.4% (CE) were observed in the controls in the absence of both in-situ produced H2O2 and light irradiation, 62.4 ± 2.2% (W), 84.1 ± 1.5% (Mo) and 51.3 ± 1.7% (CE) with light irradiation only, and 57.6 ± 1.6% (W), 81.7 ± 1.7% (Mo) and 71.6 ± 0.8% (CE) with in-situ produced H2O2 only. A shift from the in-situ produced H2O2 at a period of 2.5 h to the absence of this species for another 2.5 h further improved W (98.1%) and Mo (100%) deposition. These results provide a sustainable and environmentally benign approach for efficient W and Mo recovery. The evidence of influence factors including light irradiation, in-situ produced H2O2, shift from in-situ produced H2O2 to the absence of this species, and applied voltage can contribute to improving understanding of and optimizing W and Mo deposition in MECs.