Strongly coordinating mediator enables single-step resource recovery from heavy metal-organic complexes in wastewater
Wei Shi, Jiayi Li, Fei Gao, Lijun Meng, Xiao Su, Zhiwei Wang
Abstract
Heavy metals complexed with organic ligands are among the most critical carcinogens threatening global water safety. The challenge of efficiently and cost-effectively removing and recovering these metals has long eluded existing technologies. Here, we show a strategy of coordinating mediator-based electro-reduction (CMBER) for the single-step recovery of heavy metals from wastewater contaminated with heavy metal-organic complexes. In CMBER, amidoxime with superior coordinating abilities over traditional ligands is immobilized by an amidoximation reaction onto a flow-through electrode that concurrently functions as a filtration device. This unique process spontaneously captures heavy metal ions at the -N-OH and -NH2 groups of the amidoxime from their complexes without external energy input (ΔG of amidoxime mediator with Cu(II): −6.59 eV), followed by direct in situ electro-reduction for metal recovery. The reduction of captured Cu(II) to Cu(0) regenerates the amidoxime’s active sites, enabling continuous capture of Cu(II). Operating at a voltage of 3 V and a water flux of 250 L m−2 h−1, the CMBER system achieves a Cu(II) recovery rate of 97.6% and demonstrates an energy efficiency of 340.1 g kWh−1. This energy efficiency significantly outperforms existing technologies, showing a nearly fivefold improvement. CMBER creates a new dimension for cost-effective resource recovery and water purification. Heavy metal-organic complexes are among the most critical carcinogens threatening global water safety. Here, the authors report a strategy of coordinating mediator-based electro-reduction for the single-step recovery of heavy metals from wastewater contaminated with heavy metal-organic complexes.