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

Abstract

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.

Insights into the Mechanism of Selective Removal of Heavy Metal Ions by the Pulsed/Direct Current Electrochemical Method

“…Many studies have used different novel electrodes by the DC electrodeposition method to reduce heavy metal ion pollution to below-safe water drinking levels. − However, most of these studies have focused on aqueous solutions of a single pollutant. In fact, there are various cations, such as Na + , Ca 2+ , and Mg 2+ , in wastewater, which are higher in content than heavy metal ions, leading to intense competition for active adsorption sites. , These coexisting positively charged ions will be adsorbed on the electrode surface, thus rejecting the heavy metal ions approaching the cathodic electrode due to Coulomb repulsion, making many surface-active sites inaccessible. , Therefore, it is a significant challenge to achieve efficient DC electrodeposition of heavy metal ions in a complex aqueous solution, mainly due to the limited migration of heavy metal ions approaching the cathodic electrode.…”

Natural Pyrite-assisted Mechanochemical Recovery of Insoluble Manganese from Electrolytic Manganese Residue: Kinetics and Mechanisms

“…Electrolytic metal manganese (EMM) is an important strategic material extensively used in metallurgical and chemical applications, especially as a fundamental element of batteries for new energy vehicles. 1 Since 2000, China has become the world's largest producer, consumer, and exporter of EMM products in the world. Meanwhile, to produce 1 ton of EMM, 10−12 tons of electrolytic manganese residue (EMR) would be produced.…”