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[Display omitted] • ACF cathode exhibits excellent performance in PAA activation for SMX elimination. • ACF could maintain persistent catalytic ability under a cathodic electric field. • •OH generated from ACF cathode plays the dominant role in organics degradation. • Degradation intermediates of SMX are harmless to the aquatic ecology. Advanced oxidation processes (AOPs) based on peracetic acid (PAA) could generate various radicals with low by-product generation, making them a vital technology in the remediation of organic pollution. Maintaining the activity and continuous operation of catalytic systems in water treatment processes was a highly challenging research topic. Herein, the electrochemical process with an activated carbon fiber (E-ACF) cathode was devised to boost the activation of PAA (E-ACF-PAA) for persistent elimination of organics. Compared to other commonly used electrodes, the ACF cathode displayed superior PAA activation ability and higher sulfamethoxazole (SMX) removal. The applied cathodic electric field could protect ACF from PAA oxidation, maintaining its long-term catalytic ability over 50 cycles. Based on radical quenching studies, the EPR test, and the estimation of radical contribution, the E-ACF-PAA process was identified as a radical dominant system. Importantly, isolated chamber experiments proved that PAA was mainly decomposed on the cathode to produce hydroxyl radicals (OH) for SMX degradation, while the anode played a negligible role. According to toxicity prediction and algae growth tests, the degradation products were harmless to the aquatic ecology. Remarkably, continuous flow experiments over a 24 h and different water matrix tests have also proven applicability in practical scenarios. This work provided novel insights into the electrochemical activation of PAA and further expanded the potential applications of PAA-based AOPs in the remediation of organic pollution. [ABSTRACT FROM AUTHOR]

Treatment of a persistent organic pollutant, carbamazepine (CBZ), in aqueous solution by a novel and sustainable method, Electro-activated carbon fiber-peroxydisulfate (E-ACF-PDS), was investigated and compared with ACF adsorption, Peroxydisulfate (PDS), ACF-peroxydisulfate (ACF-PDS), E-Pt (Pt-plating titanium as cathode in electrolysis), E-ACF (ACF as cathode in electrolysis), and Electro-Pt-peroxydisulfate (E-Pt-PDS) processes, respectively. The removal rate of CBZ by E-ACF-PDS was 98.78% in 30 min, which was much higher than that of the others. Besides, several tests were performed to investigate the role of operational conditions (pH, peroxydisulfate concentration, electrode potential, temperature, and water matrix) in E-ACF-PDS process. Moreover, it is worth noting that even after recycling ACF for 100 times, the removal rate of CBZ in 30 min decreased only slightly from 98.78% to 97.35% in E-ACF-PDS process. In addition, the surface functional groups, FTIR spectrum, Raman spectrum, BET surface area, micropore volume, and SEM images of ACF before and after long time service were investigated and the results revealed that the ACF could maintain the original features in E-ACF-PDS process even after 100 cycles, while the ACF alone was seriously damaged in ACF-PDS process after 50 cycles. These results suggested that the E-ACF-PDS process could remarkably enhance the removal of CBZ in aqueous solution due to the simultaneous adsorption of contaminants and the increase in the generation of active radicals on ACF. The electrons on cathode could inhibit the destruction of ACF caused by chemical oxidation such as sulfate radicals, hydroxyl radicals, and peroxydisulfate. Therefore, the E-ACF-PDS process may provide an effective and sustainable approach to water treatment for the elimination of contaminants of emerging concern in water. [ABSTRACT FROM AUTHOR]

Removal of nitrobenzene (NB), a carcinogenic and refractory pollutant, in aqueous solution by adsorption, ozonation, electrolysis, and electro-peroxone (E-peroxone) with activated carbon fiber (ACF) was investigated, respectively. Kinetic analyses of NB removal by all the processes followed pseudo-first-order kinetics and the K app of E-peroxone-ACF was 14.90 × 10 −2 min −1 , which was much higher than the others. Besides, the K app of E-peroxone-ACF process reduces slightly to 12.18 × 10 −2 min −1 even after 100 times of ACF recycle, showing a sustainable activity. Moreover, according to the pore texture characteristics, surface functional groups, FTIR, and SEM images, E-peroxone process does not considerably alter the ACF surface, whereas ozone alone can cause substantial damage to it. These results suggested that ACF was induced from an initiator/a promoter into an electrocatalyst in ozonation by free electrons injection. Moreover, comparing with titanium cathode, ACF can remarkably improve the removal of NB in E-peroxone due to the synchronous adsorption of pollutants and ozone as well as the enhancement of H 2 O 2 generation. It indicates that the ACF cathode is a promising material for organic pollutants removal in the E-peroxone process. [ABSTRACT FROM AUTHOR]

• Novel nitrogen-doped carbon fiber aerogel (N-CFA) was obtained by carbonization of cotton and urea in one-step. • 1O 2 instead of radicals was the predominant reactive oxidant species in N-CFA/PMS process. • CBZ degradation pathways mainly by 1O 2 were firstly proposed. • CBZ was removed in different water matrices with a satisfactory efficiency in N-CFA/PMS process. Nitrogen-doped carbon as metal-free catalysts exhibited exceptionally catalytic activities in environmental remediation fields. Herein, a novel nitrogen-doped carbon fiber aerogel (N-CFA), which was conveniently prepared using cotton and urea by a direct high temperature carbonization in one-step, was used to activate peroxymonosulfate (PMS) for the degradation of carbamazepine (CBZ) in water. Characterization results demonstrated that the key active sites (pyridinic N, pyrrolic N, and graphitic N) were formed in the process of nitrogen doping into the carbon fiber aerogel. More importantly, singlet oxygen (1O 2) instead of conventional OH and SO 4 − was suggested as the predominant reactive oxygen species (ROS) during N-CFA/PMS process based on the scavenger inhibition tests, and confirmed by molecular probe and liquid-phase electron paramagnetic resonance (EPR) experiments. It was speculated that nitrogen-containing functional groups played a key role in inducing the non-radical pathway. Moreover, CBZ degradation pathways mainly by 1O 2 were firstly proposed based on intermediates. The N-CFA/PMS system could achieve a CBZ degradation rate of 100% within 50 min, which was significantly higher than the catalytic effect of several carbon materials (ACF, GAC, and GO) and even higher than the catalytic effect of various metal-based catalysts including Co 3 O 4 , CuO, Fe 3 O 4 , and Fe 2 O 3. It was also noted that the CBZ was removed with a satisfactory efficiency in different water matrices with inorganic anions (HCO 3 –, Cl−, H 2 PO 4 −, SO 4 2−, and NO 3 –) and humic acid (HA). Thus, this study proposed a benign and highly efficient oxidation technology, which would exhibit wide potential for environmental restoration. [ABSTRACT FROM AUTHOR]