Search

To improve the performance and solve the restrictions of UV/chlorine process (e.g., the narrow pH application range and high disinfection by-products (DBPs) formation), a Fe 2+ assisted advanced oxidation process with electrochemically generated chlorine (UV/E-Cl/Fe 2+ ) was proposed for carbamazepine (CBZ) degradation, which eliminated CBZ (5 mg/L) within 4 min under the optimal conditions. Compared with UV/electro-generated chlorine (UV/E-Cl) and anodic oxidation-chlorination/Fe 2+ (AO-Cl/Fe 2+ ) processes, the apparent first-order kinetics constant in UV/E-Cl/Fe 2+ increased by 2.56 and 3.18 times respectively, and the energy consumption was lower (1.15 kWh/m 3 -log). Simultaneously, the pH application range could be expanded to 9, and DBPs formed in this process were 17.1% less than those in UV/E-Cl. Through quenching tests, electron paramagnetic resonance (EPR) experiments, measurement of • OH concentration, quantification of methyl phenyl sulfoxide (PMSO) and benzosulfone (PMSO 2 ) and processes comparison, possible CBZ degradation pathways and mechanism of UV/E-Cl/Fe 2+ were proposed, in which Fe(IV) played the dominant role in the early stage, while the production of radicals (i.e., • OH and Cl • ) was enhanced with the increase of chlorine generation, accelerating the CBZ removal. Furthermore, this process demonstrated wide application prospect in treating various contaminants and real wastewaters. In conclusion, this study offers an effective and energy-efficient method for organic pollutants degradation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

As nitrate contamination causes serious environmental problems, it is necessary to develop stable and efficient electrocatalysts for efficient electrochemical nitrate reduction reaction (ENRR). Here, a nonprecious Co 3 O 4 /carbon felt (CF) electrode with a 3D structure was prepared by integrating electrodeposition with calcination methods. This 3D structured Co 3 O 4 /CF electrode exhibits a high-rate constant of 1.18 × 10 -4 s -1 cm -2 for the ENRR, surpassing other Co 3 O 4 electrodes in previous literature. Moreover, it also has an excellent stability with a decrease of 6.4% after 10 cycles. Density functional theory calculations, electron spin resonance analysis, and cyclic voltammetry were performed to study the mechanism of the ENRR on the Co 3 O 4 /CF electrode, proving that atomic H* (indirect pathway) plays a prominent role in NO 3 - reduction and clarifying the synergistic effect of Co(III) and Co(II) in the Co(II)-Co(III)-Co(II) redox cycle for the ENRR: Co(III) prefers the adsorption of NO 3 - and Co(II) favors the production of H*. Based on this synergy, a relatively large amounts of Co(II) on the surface of the Co 3 O 4 /CF electrode (1.3 Co(II)/Co(III) ratio) was maintained by controlling the temperature of calcination to 200 °C with a lower energy barrier of H* formation of 0.46 eV than other ratios, which is beneficial for forming H* and enhancing the performance of the ENRR. Thus, this study suggests that building 3D structure and optimizing Co(II)/Co(III) ratio are important for designing efficient Co 3 O 4 electrocatalyst for ENRR.