Simultaneous Recovery of NH3–N and Removal of Heavy Metals from Manganese Residue Leachate Using an Electrodialysis System

The problem of high concentration of NH3–N and heavy metals in manganese residue leachate (MRL) needs to be solved urgently as it can harm the surrounding soil, water bodies, and even the ecological system. In this study, a novel electrodialysis system with a self-growing titanium dioxide nanowire (TiO2 NW) electrode is proposed to recover NH3–N and remove heavy metals from MRL. Plant growth experiments and ecotoxicity studies are used to evaluate the ecological risks of the reuse of recovered NH3–N. In the electrodialysis system with a proton membrane to separate the two chambers, 87%–97% removal of heavy metals and 95% recovery of NH3–N from MRL can be achieved. The obtained recovery solution from the cathode chamber can greatly promote the plant growth. The ecotoxicity experiment results further reveal that the recovered NH3–N can optimize the soil microbial community structure by promoting the reproduction of the genus Bacillus and thus improve soil fertility. This work can provide a new perspective on the harmless disposal and resource recovery of MRL.