Integrating natural tourmaline with energy conversion ability to magnetically assembled electrode: Boosted electrochemical oxidation wastewater treatment performance

Novel anodes are desirable in the development of electrochemical oxidation wastewater treatment (EOWT). Magnetically assembled electrode (MAE) is a novel modular electrode format that physically adsorbs magnetic particles (auxiliary electrodes, AEs) onto the main electrode (ME) by magnetic force which realizes an effective and sustainable EWOT process but puts a new requirement on AEs polarization. Therefore, tourmaline (Tml), a natural mineral with ferroelectricity, pyroelectricity, and piezoelectricity, was introduced into the MAE in this study. Tml particles were expected to utilize waste heat or mechanical energies in electrolysis (e.g., Joule heat, bubble strike) and give extra electricity to the stacked AEs (Fe3O4/Sb-SnO2 granules herein) to fully active MAE. Tml’s effects were investigated via different MEs (Ti/IrO2-Ta2O5, graphite, Ti/Sb-SnO2), different wastewater, different Tml sizes, loading amounts, and different conditions (e.g., current density). Results show that all these conditions could affect the buffering of Acid red G degradation, Tml could offer a 10∼40% buff. Medium Tml size and loading as well as low or medium current density (e.g., 2 mA·cm−2 or 20 mA·cm−2) are appropriate. For real wastewater degradation, Tml facilitates macromolecule destruction. This study may start a new application route of abundant natural energy-converting materials in the EOWT area.