MnO₂/TiO₂ Nanotube Array-Coated Titanium Substrates as Anodes for Electrocatalytic Oxidation of As(III) in Aqueous Solution

Abstract

The conversion of As­(III) to As­(V) in groundwater is an urgent issue, owing to the higher mobility, stronger toxicity, and weaker binding ability of As­(III). In this work, the electrocatalytic oxidation of As­(III) was efficiently achieved with a facile and environmentally benign method by using hierarchical MnO2-deposited TiO2 nanotube arrays (MnO2/TNAs) as the anode. The electrocatalytic oxidation performance of the as-fabricated MnO2/TNA-coated anode was systematically investigated. The results exhibited that such as-fabricated MnO2/TNAs had a high oxidation efficiency of 90% at a low concentration of As­(III) (1 mg L–1). Furthermore, the reaction mechanism was systematically studied by electron spin resonance and free radical capture experiments. The oxidation of As­(III) was accomplished via both direct oxidation on the anode surface and indirect oxidation of the reactive oxygen species. The highly efficient TNA-based anode offers a potentially promising advanced material for electrochemical oxidation of trace As­(III) in the practical field.

Self-supported electrocatalysts for the hydrogen evolution reaction

“…Titanium materials have been deemed as the optimum substrate candidates due to their natural abundance, excellent corrosion resistance to acidic and alkaline media, processability, and good chemical stability. [146][147][148][149][150] Inspired by the merits, Li et al fabricated Co-doped anatase TiO 2 nanorod arrays on a Ti plate (Co-TiO 2 @Ti(H 2 )) with 1D structure, abundant oxygen vacancies (OVs), and good hydrophilic feature by ion exchange process and calcination treatment (Fig. 7a-c).…”

Direct Electrocatalytic Reduction of As(III) on CuSn Alloy Electrode: A Green and Sustainable Strategy to Recover Elemental Arsenic from Arsenic Wastewater

“…13−15 Electrocatalytic oxidation of As(III) to As(V) occurs when a positive voltage is applied to the anode, leading to the direct conversion of adsorbed As(III) to As(V). 15 Additionally, •OH generated from the reaction between the anode and water indirectly facilitates the conversion process. 16,17 Although these oxidation methods effectively transform As(III) to As(V), the resultant As(V) still maintains its toxicity, which requires further separation from water, typically through adsorption processes.…”

“…Biological oxidation has shown promise, as proteobacteria have been proven effective in oxidizing As­(III) to As­(V) . Photocatalytic oxidation provides another option, involving indirect oxidation using hydroxyl radicals (·OH) and superoxide radicals (·O 2 – ), or direct oxidation through photogenerated holes. , Alternatively, electrocatalytic oxidation is a notable and straightforward technology that efficiently converts As­(III) to As­(V) under ambient conditions. − Electrocatalytic oxidation of As­(III) to As­(V) occurs when a positive voltage is applied to the anode, leading to the direct conversion of adsorbed As­(III) to As­(V) . Additionally, ·OH generated from the reaction between the anode and water indirectly facilitates the conversion process. , Although these oxidation methods effectively transform As­(III) to As­(V), the resultant As­(V) still maintains its toxicity, which requires further separation from water, typically through adsorption processes. , Therefore, it is desirable to develop an alternative and sustainable strategy for arsenic removal from water, mitigating its harmful impact and enabling arsenic recovery.…”

Tackling Challenges of Long-Term Electrode Stability in Electrochemical Treatment of 1,4-Dioxane in Groundwater

“…We explore pulsed electrolysis where short pulses of the electric current, typically ranging from milliseconds to seconds, are periodically applied using the same electrode material for both anode and cathode. − Our focus is on determining whether reversing polarity can minimize electrode deactivation caused by the self-oxidation of catalytic active centers on the anode in a low-conductivity water matrix, − thereby enabling effective, long-term treatment of 1,4-dioxane. To realize the proposed pulsed electrolysis scheme, we develop an electrode featuring highly conductive titanium suboxide nanotubes (TiO x NTs, 1 < x < 2) − by first anodizing Ti material to form nanotubes and subsequently reducing them to enhance conductivity and electrochemical reactivity. In contrast to previous studies that predominantly employed plates of Ti, − we here employ a Ti mesh as a porous electrode substrate as well as a newly developed two-step reduction method, specifically designed for the intended treatment scheme.…”