Electrochemical mineralization of sulfamethoxazole over wide pH range using FeIIFeIII LDH modified carbon felt cathode: Degradation pathway, toxicity and reusability of the modified cathode

Abstract

Hierarchical three-dimensional (3D) porous architecture Fe II Fe III layered double hydroxide (LDH) multiwall was grown on carbon-felt (CF) substrate via solvothermal process. The asdeposited Fe II Fe III LDH/CF cathode was composed of highly oriented and well crystallized interconnected nanowalls with high electrical conductivity and excellent catalytic activity over a wide pH range (pH 3 -9) for heterogeneous electro-Fenton (HEF) degradation of antibiotic sulfamethoxazole (SMT) in aqueous medium. Mineralization efficiencies (in terms of TOC removal) of ~97%, 93% and 90% was achieved at pH 3, 6 and 9 respectively for Fe II Fe III cathode during HEF treatment of 0.2 mM SMT solution at applied current density of 7.5 mA cm -2 using Ti4O7 anode. Comparative electro-Fenton (EF-Fe 2+ ) with 0.2 mM Fe 2+ or electrooxidation with H2O2 production (EO-H2O2)studies using raw CF cathode at similar experimental conditions showed relatively lower mineralization with highest TOC removal efficiency of 77% and 64% obtained at pH 3 for EF-Fe 2+ and EO-H2O2 respectively. Oxidative degradation of SMT in HEF system was by (i) Ti4O7( • OH) generated at anode surface at all pH studied, (ii) surface catalyzed process and (iii) contribution from homogeneous catalyzed process at pH 3 due to leached iron ions. The prepared Fe II Fe III LDH/CF exhibited excellent catalytic stability with good reusability up to 10 cycles of 4 h treatment at pH 6. Initial SMT solution showed relatively high toxicity but total detoxification of the solution was attained after 8 h of treatment by HEF with Fe II Fe III LDH/CF cathode. HEF with Fe II Fe III LDH/CF cathode is an exciting technique for remediation of organic contaminated wastewater.

Nature, Mechanisms and Reactivity of Electrogenerated Reactive Species at Thin‐Film Boron‐Doped Diamond (BDD) Electrodes During Electrochemical Wastewater Treatment

“…[39,71] However, recently Oturan's group has reported the fourth possible attack mode of BDD( * OH) onto organic molecules, which involves ipso substitution of the hydroxyl radical on the organic pollutants, especially, saturated aliphatic compounds ( Figure 5). This has been demonstrated during electrochemical treatment of different organic pollutants such as pharmaceuticals, [5,[74][75][76] herbicides [31,77] and synthetic dyes solutions. This has been demonstrated during electrochemical treatment of different organic pollutants such as pharmaceuticals, [5,[74][75][76] herbicides [31,77] and synthetic dyes solutions.…”

Environmental Applications of Boron‐Doped Diamond Electrodes: 1. Applications in Water and Wastewater Treatment

“…Also, magnetite and zero‐valent iron were found as effective heterogeneous catalysts to degrade dye rhodamine B and salicylic acid in aqueous medium . Recently, incorporation of the catalyst into the cathode material was successfully carried out for heterogeneous electro‐Fenton process …”

“…[182][183][184] Recently, incorporation of the catalyst into the cathode material was successfully carried out for heterogeneous electro-Fenton process. [185][186][187]…”

Electrochemical Abatement of Analgesic Antipyretic 4‐Aminophenazone using Conductive Boron‐Doped Diamond and Sub‐Stoichiometric Titanium Oxide Anodes: Kinetics, Mineralization and Toxicity Assessment

“…OH) radicals which can completely mineralize any class of organic pollutants ,,,. However, sub‐stoichiometric titanium oxides especially Ti 4 O 7 has been recently proposed as alternative low cost electrodes for both AO and EF processes ,. It is considered significantly less expensive option compared to BDD because it is solely prepared from TiO 2 which is one of the cheapest feedstock on earth and has easy production route ,.…”