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Heterogeneous sulfite-based advanced oxidation process is extremely promising for the removal of various industrial pollutants owing to its generation of multiple reactive oxygen species (ROS), while the unclear mechanism of S(IV) conversion and ROS generation hinder its practical applications. Here, the iron-copper bimetallic was synthesized for potassium pyrosulfate catalysis, which was designed for insight into the mechanism of micropollutant degradation driven by sulfur species conversion. Experimental and theoretical calculations have shown that the reaction process and corresponding mechanisms can be significantly distinguished into three different stages. Stage one prepares sufficient Fe(III) for the initiation of the reaction, while stage two generating ROS and reduces S(IV). In the stage three, the low-valent sulfur produced from S(IV) combines with iron-copper materials to form highly active sulfur sites, which react with O 2 to generate a large number of hydroxyl radicals (•OH). Furthermore, a variety of contaminants were used to validate the universality of the system, and their wide distribution in wastewater implies broad application prospects. This research provides in-depth interpretations of the induced mechanism of sulfur species conversion in the sulfite heterogeneous system, provides a solid theoretical foundation for the engineering application of the system., 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 © 2024 Elsevier B.V. All rights reserved.)

How the anion ligands of manganese precursors affect the catalytic activity of amorphous manganese oxides (MnOx) in Fenton-like process is poorly understood. Here, five amorphous MnOx synthesized by Mn(II) precursors with different ligands were characterized and adopted to activate peracetic acid (PAA) for bisphenol A (BPA) degradation. Although > 90 % BPA removal was achieved in the five MnOx/PAA processes via both adsorption and oxidation, the oxidation k obs greatly differentiates by the ligands types with the order of MnOx-N > MnOx-S > MnOx-Cl > MnOx-AA > MnOx-OA. Ligands types would affect the specific surface area of MnOx and their ability to adsorb BPA, however which is not the decisive factor in determining the contaminant oxidation efficiency. Multiple experimental results indicate that the generation of oxygen vacancies induced by the ligands alters the Mn(III)/Mn(IV) ratio, ultimately contributing to the different efficiency of BPA oxidation driven by the direct electron transfer mechanism. Moreover, amorphous MnOx holds the promise of practical applications in catalytic PAA of various micropollutants with good stability. This study advances the fundamental understanding of ligand-regulated amorphous MnOx-catalyzed PAA process., 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 © 2024 Elsevier B.V. All rights reserved.)

Herein, an N-coordinated Fe site dispersed in porous carbon frameworks (Fe-NC) fabricated from zeolitic imidazolate frameworks encapsulated with iron acetylacetonate (Fe(acac) 3 @ZIFs) was employed to activate peroxymonosulfate (PMS) for the attenuation of sulfisoxazole (SIZ) and treating real hospital wastewater. The constructed Fe-NC/PMS system exhibited good catalytic stability for SIZ degradation, maintaining excellent degradation performance over multiple cycles with virtually no leaching. The quenching experiments, electron paramagnetic resonance (EPR) capture analyses, and semi-quantitative measurements showed that singlet oxygen ( 1 O 2 ) and high-valent metal-oxo species were mainly responsible for SIZ degradation by Fe-NC/PMS. Significantly, ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS/MS) was used to trace 134 pharmaceutical contaminants in real hospital wastewater. Effective degradation was achieved for 87 % of the pharmaceutical contaminants by the Fe-NC/PMS process. Seventy-four pharmaceutical contaminants were eliminated. Taken together, this work successfully established the Fe-NC/PMS technology using the developed iron-based materials and explored its application to real hospital wastewater treatment, providing an eco-friendly and effective strategy for treating wastewater., 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 © 2024 Elsevier B.V. All rights reserved.)

Spatially confined structure exhibits surprising physics and chemistry properties that significantly impact the thermodynamics and kinetics of oxidation reactions. Herein, porous carbons are rationally designed for tunable nanopore structures (micropores, 4.12 % ∼ 91.64 %) and diverse spatial confinement ability, as indicated by their differential enhancement performances in the Fenton oxidation. Porous carbons can alter the characteristics of the charge transport process for accelerating sustainable electron shuttle between hydrogen peroxide and iron species, and thus exhibit long-term performance (17 cycling tests). The positive spatial confinement for boosting Fenton oxidation (charge transport, mass transfer) occurs in nanochannels < 1 nm, while the diminished effect ranges of 1-1.5 nm, and the adverse effect ranges greater than 1.5 nm. The density functional theory calculation provides further support for certifying the promoted charge transport process and spatial confinement for hydroxyl radical inside the confined nanochannel structure (below 1 nm, especially) by the comparatively large electron cloud and the relatively negative adsorption energy, respectively. Coupling nanochannels with the Fenton oxidation greatly utilize hydrogen peroxide, due to spatial nanoconfinement and selective adsorption towards target contaminants. This strategy of deploying nanochannels in catalyst design can be applied for the elaborate construction of efficient nanostructured catalysts for environmental remediation., 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 © 2024 Elsevier B.V. All rights reserved.)

Both adsorption and oxidation occur and contribute to organics removal in carbonaceous materials based advanced oxidation processes, while the correction of adsorption and oxidation, and the role of adsorption in the veritable removal of organic are not clear. Herein, we investigated the performance of carbamazepine (CBZ) removal by peroxymonosulfate (PMS) activated by magnetic Fe-doped biochar through two models of pre-adsorption oxidation and synchronous adsorption oxidation processes. The adsorption process was better fitted by pseudo-second-order kinetic model and the adsorption mechanism was obtained by comprehensive analysis of equilibrium adsorption capacities, surface functional groups, specific surface area, pore volume, and I D /I G value. It is noted that pre-adsorption highly inhibited the further oxidation of CBZ in 0.5Fe@LSBC700/PMS system due to the occupied catalytic active sites. Total CBZ removal in pre-adsorption oxidation (45 %) was inferior to synchronous adsorption oxidation (∼100 %), as well as the veritable CBZ oxidation removal of 27 % for pre-adsorption oxidation vs ∼100 % in synchronous adsorption oxidation at 30 min. Oxidation degradation of CBZ based on radical oxidation was identified by quenching experiments and electron paramagnetic resonance measurements. This work is conducive to identifying the role of adsorption during the removal of organics in the adsorption-oxidation process, as well as veritable adsorption and oxidation removal of organics., 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 © 2024 Elsevier B.V. All rights reserved.)

In this study, cobalt molybdate (CoMoO 4 ) activated peracetic acid (PAA) was developed for water purification. CoMoO 4 /PAA system could remove 95% SMX with pseudo-first-order reaction rate constant of 0.15410 min -1 , which was much higher than CoFe 2 O 4 /PAA, FeMoO 4 /PAA, and CoMoO 4 /persulfate systems. CoMoO 4 /PAA system follows a non-radical species pathway dominated by the high-valent cobalt (Co(IV)), and CH 3 C(O)OO • shows a minor contribution to decontamination. Density functional theory (DFT) calculation indicates that the generation of Co(IV) is thermodynamically more favorable than CH 3 C(O)OO • generation. The abundant Co(IV) generation was attributed to the special structure of CoMoO 4 and effect of molybdenum on redox cycle of Co(II)/Co(III). DFT calculation showed that the atoms of SMX with higher ƒ 0 and ƒ - values are the main attack sites, which are in accordance with the results of degradation byproducts. CoMoO 4 /PAA system can effectively reduce biological toxicity after the reaction. Benefiting from the selective of Co(IV) and CH 3 C(O)OO • , the established CoMoO 4 /PAA system exhibits excellent anti-interference capacity and satisfactory decontamination performance under actual water conditions. Furthermore, the system was capable of good potential practical application for efficient removal of various organics and favorable reuse. Overall, this study provides a new strategy by CoMoO 4 activated PAA for decontamination with high efficiency, high selectivity and favorable anti-interference., 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 © 2024 Elsevier B.V. All rights reserved.)

Solution pH is one of the primary factors affecting the efficiency of water decontamination. Although the influence of pH on oxidants activation, catalyst activity, and reactive oxygen species have been widely explored, there is still a scarcity of systemic studies on the changes in the oxidation behavior of organic pollutants at different pH levels. Herein, we report the influence laws of pH on the forms, reactivities, active sites, degradation pathways, and products toxicities of organic pollutants. Changes in pH cause the protonation or deprotonation of organic pollutants and further affect their forms and chemistry (e.g., electrostatic force, hydrophobicity, and oxidation potential). The oxidation potential of organic pollutants follows the order: protonated form > pristine form > deprotonated form. Moreover, protonation or deprotonation can modify the active sites and degradation pathways of organic pollutants, wherein deprotonation renders them more susceptible to electrophilic attack, while protonation reduces their activity against electrophilic and nucleophilic attacks. Additionally, pH adjustments can modify the degradation pathway and the toxicity of transformation products. Overall, pH changes can affect the oxidation fate of organic pollutants by altering their structure, which distinguishes it from the effect of pH on oxidants or oxidant activation processes., 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 © 2024 Elsevier B.V. All rights reserved.)

In this study, the porous carbon material (FeN-BC) with ultra-high catalytic activity was obtained from waste biomass through Fe-N co-doping. The prominent degradation rate (> 96.8%) of naproxen (NAP) was achieved over a wide pH range (pH 3.0-9.0) in FeN-BC/PAA system. Unlike previously reported iron-based peracetic acid (PAA) systems with • OH or RO • as the dominated reactive species, the degradation of contaminants was attributed to singlet oxygen ( 1 O 2 ) produced by organic radicals (RO • ) decomposition, which was proved to be thermodynamically feasible and favorable by theoretical calculations. Combining the theoretical calculations, characteristic and experimental analysis, the synergistic effects of Fe and N were proposed and summarized as follows: i) promoted the formation of extensive defects and Fe 0 species that facilitated electron transfer between FeN-BC and PAA and continuous Fe(II) generation; ii) modified the specific surface area (SSA) and the isoelectric point of FeN-BC in favor of PAA adsorption on the catalyst surface. This study provides a strategy for waste biomass reuse to construct a heterogeneous catalyst/PAA system for efficient water purification and reveals the synergistic effects of typical metal-heteroatom for PAA activation., 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 © 2024 Elsevier B.V. All rights reserved.)

A novel "ferrate/percarbonate (Fe(VI)/SPC) co-oxidation process" was used to treat ciprofloxacin (CIP) and various micropollutants (MPs), which owned better performance than mixture of Fe(VI), Na 2 CO 3 and H 2 O 2 . The mechanism investigation found that the low-concentration H 2 O 2 (1-2 µM) released by SPC can promote the high-valent iron intermediates (Fe(IV)/Fe(V)) of Fe(VI) to the MP oxidation, and Fe(VI) products can also activate SPC to produce hydroxyl radical (·OH). The interactive activation of Fe(VI) and SPC was realized, which retained the high selectivity of Fe(VI) to electron-rich pollutants, and also made up the oxidation of electron-deficient pollutants through •OH, improving the degradation effect of various MPs by 20-30%, and the rate constant was increased by 1 to 3 times. Moreover, non-purgeable organic carbon (NPOC) determination confirmed that •OH participation reduced the NPOC value of CIP from 5.43 mg/L to 4.37 mg/L. The transformation pathway of CIP showed that Fe(VI)/SPC resulted in more hydroxylation intermediates of CIP than Fe(VI) alone. Acute toxicity assays found that the photoinhibition rate of CIP treated with Fe(VI) alone was 14.5%, while the sample treated with Fe(VI)/SPC showed no significant photoinhibition effect, which proved that the new process had good detoxification properties for CIP., 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 © 2024 Elsevier B.V. All rights reserved.)

Traditional Fenton and Fenton-like processes are affected by the sluggish kinetics of Fe(II) regeneration and Fe(III) accumulation. This research revealed that the degradation efficiency of pollutants was significantly increased by adding Fe(III) to the Vis/PS system. A mechanism is proposed in which photosensitivity pollutants can boost Fe(III) to produce Fe(II) under visible light irradiation. Intriguingly, Fe(III) rapidly combines with LVF in aqueous environments to form Fe(III)-LVF complexes. This research confirms that Fe(III)-pollutant complexes are generated. The proportion of complexes are calculated using mathematical models. Furthermore, the production of Fe(IV) is verified in the Vis/PS/Fe(III) system, which also plays a vital role in boosting LVF degradation. Overall, this study provides comprehensive insights into the degradation mechanism of micropollutants, involving hydroxyl radical (OH∙), Fe(IV), and Fe(III)-LVF complexes, providing an efficient and green strategy for contaminant removal during wastewater treatment., 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 © 2023 Elsevier B.V. All rights reserved.)

Iron-based PAA activation process is a promising advanced oxidation process for water decontamination which depends on Fe(II) as the main reactive site for PAA activation, resulting in various reactive oxidative species (ROSs) generation. For practical application, the impact of water matrix chloride ion (Cl - ) on ROSs production and contaminants removal should be carefully considered. In this study, it's found that the introduction of Cl - (0.1-10 mM) could significantly enhance the reaction rate of the rapid stage (k obs1 ) up to 2.15 times at the initial pH of 4.25 in the Fe(II)/PAA system. Further studies demonstrated that the improved removal capacity of NAP resulted from Cl - induced R-O • generation as indicated by the exposure dose of R-O • increasing from 7.74 × 10 -11 M•s to 1.44 × 10 -10 M•s, rather than chlorine-containing radicals' generation. DFT calculation results suggested that the formed Fe(II)-Cl - complexes could easily activate PAA to generate more ROSs for NAP removal. Moreover, Fe(II)/PAA treatment can alleviate the biological toxicity of pollutants via both the Escherichia coli test and toxicity assessment. The obtained new knowledge manifested that Cl - can boost ROSs generation and conversion in iron-based PAA systems, providing guidance for the efficient decontamination of chlorine-containing sewage with PAA-based AOPs., 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 © 2023 Elsevier B.V. All rights reserved.)

Facing the constraints of critical agglomeration and poor reusability of CuFe 2 O 4 in catalytic applications, the feasibility of synthesizing a composite catalyst using carbon coating technology for efficient TC removal with enhanced PDS activity was investigated. The composite catalyst (CuFe 2 O 4 @C) can stimulate both radical (SO 4 •- and HO•) and non-radical ( 1 O 2 ) pathways to dominate the catalytic reaction for removing 95.7% of the TC in 60 min. Meanwhile, the defective structure of the external carbon layer protected the internal CuFe 2 O 4 from excessive oxidation, allowing the CuFe 2 O 4 @C to maintain over 90% TC removal after 5 cycles with less interference from inorganic anions, demonstrating significant catalytic performance and satisfactory reusability. Finally, the DFT calculations and TEST evaluation were performed to discuss the structural properties of TC and its toxicity assessment during the whole degradation process, while three possible degradation pathways were proposed. Significantly, the carbon-coated composite catalysts of potential universal applicability for multi-pathway PDS activation offered an attractive new strategy for the effective degradation of antibiotic wastewater., 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 © 2023. Published by Elsevier B.V.)

Periodate-based advanced oxidation processes have been diffusely practiced for pollutant decontamination. However, the thermo-activation of periodate process (heat/PI), an effective water pollution removal process, has been rarely discussed, and the degradation pathway of this heat/PI system requires investigation. In this work, tetracycline antibiotics were selected as the model micropollutant for the comprehensive evaluation of the heat/PI system. The heat/PI system exhibited good performance for tetracycline (TC) remediation with temperature increases. The principal reactive oxidative species in the heat/PI system was confirmed using quenching experiments and electron paramagnetic resonance experiments. Further, the potential reactive sites in the TC were identified based on the density functional theory calculation. Based on the detection results of intermediates, there was no significant difference in byproducts generated during TC degradation under various temperatures in the heat/PI system. The Toxicity Estimation Software Tool (T.E.S.T.) method was applied to calculate the individual toxicity of the byproducts. This study contributes to a comprehensive explanation of the process of the thermal activation of periodate, and in particular, it explains the source of oxidation power, the transformation of byproducts, and the toxicity of reaction systems., 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 © 2023 Elsevier B.V. All rights reserved.)

In this study, we demonstrate that Fe(III)-doped g-C 3 N 4 can efficiently activate peracetic acid (PAA) to degrade electron-rich pollutants (e.g., sulfamethoxazole, SMX) over a wide pH range (3-7). Almost ∼100% high-valent iron-oxo species (Fe(V)) was generated and acted as the dominant reactive species responsible for the micropollutants oxidation based on the analysis result of quenching experiments, 18 O isotope-labeling examination and methyl phenyl sulfoxide (PMSO) probe method. Electrochemical testing (e.g., amperometric i-t and linear sweep voltammetry (LSV)) and density functional theory (DFT) calculations illustrated that the main active site Fe atom and PAA underwent electron transfer to form Fe(V) for attacking SMX. Linear free energy relationship (LFER) between the pseudo-first-order rates of different substituted phenols (SPs) and the Hammett constant σ + depicted the electrophilic oxidation properties. The selective oxidation of Fe(V) endows the established system remarkable anti-interference capacity against water matrices, while the Fe(V) lead to the formation of iodinated disinfection by-products (I-DBPs) in the presence of I - . Fe(III)-doped g-C 3 N 4 /PAA system showed excellent degradation efficiency of aquaculture antibiotics. This study enriches the knowledge and research of high-valent iron-oxo species and provides a novel perspective for the activation of PAA via heterogeneous iron-based catalysts and practical environmental applications., 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 © 2023 Elsevier B.V. All rights reserved.)

Ferrate (Fe(VI)) has aroused great research interest in recent years due to its environmental benignancy and lower potential in disinfection by-product generation. However, the inevitable self-decomposition and lower reactivity under alkaline conditions severely restrict the utilization and decontamination efficiency of Fe(VI). Here, we discovered that Ru(III), a representative transition metal, could effectively activate Fe(VI) to degrade organic micropollutants, and its performance on Fe(VI) activation exceeded that of previously reported metal activators. The high-valent metal species (i.e., Fe(IV)/Fe(V) and high-valent Ru species) made a major contribution to SMX removal by Fe(VI)-Ru(III). Density functional theory calculations indicated the function of Ru(III) as a two-electron reductant, leading to the production of Ru(V) and Fe(IV) as the predominant active species. The characterization analyses proved that Ru species was deposited on ferric (hydr)oxides as Ru(III), indicating the possibility of Ru(III) as an electron shuttle with the rapid valence circulation between Ru(V) and Ru(III). This study not only develops an efficient way to activate Fe(VI) but also offers a thorough understanding of Fe(VI) activation induced by transition metals., 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 © 2023 Elsevier B.V. All rights reserved.)

The acceleration of Fe(III)/Fe(II) conversion in Fenton systems is the critical route to achieve the long-lasting generation of reactive oxygen species towards the oxidation of refractory contaminants. Here, we found that waste leather derived porous carbon materials (LPC), as a simple and readily available metal-free biochar material, can promote the Fe(III)/H 2 O 2 system to generate hydroxyl radicals ( • OH) for oxidizing a broad spectrum of contaminants. Results of characterizations, theoretical calculations, and electrochemical tests show that the surface carbonyl groups of LPC can provide electron for direct Fe(III) reduction. More importantly, the graphitic-N on surface of LPC can enhance the reactivity of Fe(III) for accelerating H 2 O 2 induced Fe(III) reduction. The presence of LPC accelerates the Fe(III)/Fe(II) redox cycle in the Fe(III)/H 2 O 2 system, sustainable Fenton chain reactions is thus initiated for long-lasting generation of hydroxyl radicals without adding Fe(II). The continuous flow mode that couples in-situ Fenton-like oxidation and LPC with excellent adsorption catalytic properties, anti-coexisting substances interference and reusability performance enables efficient, green and sustainable degradation of trace organic pollutants. Therefore, the application of metal-free carbon materials in Fenton-like system can solve its rate-limiting problem, reduce the production of iron sludge, achieve green Fenton chemistry, and facilitate the actual engineering application of economic and ecological methods to efficiently remove trace organic contaminants from actual water sources., 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 © 2023 Elsevier B.V. All rights reserved.)

Periodate (PI) has recently been studied as an excellent oxidant in advanced oxidation processes, and its reported mechanism is mainly the formation of reactive oxygen species (ROS). This work presents an efficient approach using N-doped iron-based porous carbon (Fe@N-C) to activate periodate for the degradation of sulfisoxazole (SIZ). Characterization results indicated the catalyst has high catalytic activity, stable structure, and high electron transfer activity. In terms of degradation mechanism, it is pointed out that the non-radical pathway is the dominant mechanism. In order to prove this mechanism, we have carried out scavenging experiments, electron paramagnetic resonance (EPR) analysis, salt bridge experiments and electrochemical experiments, which demonstrate the occurrence of mediated electron transfer mechanism. Fe@N-C could mediate the electron transfer from organic contaminant molecules to PI, thus improving the efficiency of PI utilization, rather than simply inducing the activation of PI through Fe@N-C. The overall results of this study provided a new understanding into the application of Fe@N-C activated PI in wastewater treatment., 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 © 2023 Elsevier B.V. All rights reserved.)

At present, the potential mechanism of manganese oxide (MnO 2 ) activation of PI and the key active sites of PI activation are still unclear and controversial. To this end, three different crystal forms of MnO 2 were prepared in this study and used to activate PI to degrade pollutants. The results showed that different crystal types of MnO 2 showed different catalytic abilities, and the order was γ-MnO 2 > α-MnO 2 > β-MnO 2 . Through quenching experiments, EPR tests, Raman experiments and in situ electrochemical experiments, it has been confirmed that electron transfer-mediated non-free radical process is the main mechanism of pollutant degradation, in which the active substance is the highly active metastable intermediate complex (MnO 2 /PI*). Hydroxyl radical (HO • ), superoxide radical (O 2 •- ), singlet oxygen ( 1 O 2 ) and iodine radical (IO 3 • ) did not participate in pollutant degradation. The quantitative structure-activity relationship analysis confirmed that the catalytic performance of MnO 2 was highly positively correlated with the surface Mn(IV) content, which indicated that the surface Mn(IV) site was the main active site. Overall, this study will be of great help to the design and application of manganese dioxide activation for periodate degradation of pollutants., 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 © 2023 Elsevier B.V. All rights reserved.)

As a novel strategy, peracetic acid (PAA) based advanced oxidation processes (AOPs) are being used in micropollutant elimination due to their high oxidation and low toxicity. In this study, Co 2 Ca 1 Al 1 -LDO as a kind of layered double oxides (LDOs) was successfully synthesized, and it is the first time to apply Co 2 Ca 1 Al 1 -LDO for activating PAA. The Co 2 Ca 1 Al 1 -LDO/PAA system showed excellent removal efficiencies for various micropollutants with removal ratios ranging from 90.4% to 100% and k values from 0.087 min -1 to 0.298 min -1 . In the degradation period, various reactive oxygen species (ROS) are involved in the system, while organic radicals (R-O • ) with a high concentration of 5.52 × 10 -13 M are the dominant ROS in the contaminants degradation process. Compared to other ROS, R-O • had the largest contribution ratio (more than 85%) to pollutant degradation. Further analysis demonstrated that C1, C2, C3, C4, C5, C6 and N11 concentrated on the aniline group of SMX are the main attack sites based on the density functional theory (DFT) results, which is consistent with the degradation products. The toxicity of contaminants was obviously reduced after removing in this system. Furthermore, Co 2 Ca 1 Al 1 -LDO showed good reusability and stability, and Co 2 Ca 1 Al 1 -LDO/PAA system had excellent removal ability in actual water bodies containing inorganic anions, showing good application potential. Importantly, this study explored the feasibility of applying LDO catalysts in PAA-based AOPs for micropollutants elimination, providing new insights for subsequent research., 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 © 2023 Elsevier B.V. All rights reserved.)

Zerovalent iron (ZVI)-based Fenton-like processes have been widely applied in degrading organic contaminants. However, the surface oxyhydroxide passivation layer produced during the preparation and oxidation of ZVI hinders its dissolution and Fe(III)/Fe(II) cycling, and restricts the generation of reactive oxygen species (ROS). In this study, copper sulfide (CuS) was found to effectively enhance the degradation of diverse organic pollutants in the ZVI/H 2 O 2 system. Moreover, the degradation performance for the actual industrial wastewater (i.e., dinitrodiazophenol wastewater) in the ZVI/H 2 O 2 system was impressively improved by 41% with CuS addition, and the COD removal efficiency could reach 97% after 2 h of treatment. Mechanism investigation revealed that the introduction of CuS accelerated the sustainable supply of Fe(II) in the ZVI/H 2 O 2 system. Specifically, Cu(I) and reductive sulfur species (i.e., S 2- , S 2 2- , S n 2- and H 2 S (aq)) from CuS directly induced efficient Fe(III)/Fe(II) cycling. The iron-copper synergistic effect between Cu(II) from CuS and ZVI expedited Fe(II) generation from ZVI dissolution and Fe(III) reduction by formed Cu(I). This study not only elucidates the promotion effects of CuS on ZVI dissolution and Fe(III)/Fe(II) cycling in ZVI-based Fenton-like processes, but also provides a sustainable and high-efficiency iron-based oxidation system for removal of organic contaminants., 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 © 2023 Elsevier B.V. All rights reserved.)

In this study, vanadium powder (V) was employed as a cocatalyst to enhance the Fenton-like system. The V-Fe(III)/H 2 O 2 system can rapidly produce hydroxyl radicals and completely oxidize chloramphenicol with exceptionally high stability for long-term operation. The low-valent vanadium sites on the surface during the stepwise oxidation of vanadium from V 0 to V(IV) can donate electrons for direct H 2 O 2 activation and indirect Fenton reaction by reducing Fe(III) to produce hydroxyl radicals. Meanwhile, density functional theory (DFT) calculation unveils that low-valent vanadium sites of vanadium can lengthen Fe-O bonds of FeOH 2+ to elevate the oxidation potential of Fe(III) and promote Fe(III) reduction induced by H 2 O 2 . The self-cleaning effect of vanadium under acidic conditions can maintain reactive sites for sustainable electron donation and long-lasting enhanced Fenton oxidation. This study provides a novel enhanced Fenton oxidation for water remediation and the first mechanistic insights into the origins of V-based advanced oxidation technologies, it may also be beneficial to treat vanadium-contained wastewater., 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 © 2023 Elsevier B.V. All rights reserved.)

Herein, electro-catalysis (EC) as the electron donor to accelerate the continuable Fe(III)/Fe(II) cycles in different inorganic peroxides (i.e., peroxymonosulfate (PMS), peroxydisulfate (PDS) and hydrogen peroxide (HP)) activation systems were established. These electro-cocatalytic Fenton-like systems exhibited an excellent degradation efficiency of sulfamethoxazole (SMX). A series of analytical and characterization methods including quenching experiments, probe experiments, and electron paramagnetic resonance spectrometry (EPR) were implemented to systematically sort out the source and yield of reactive oxygen species (ROS). A wide kind of ROS including hydroxyl radical ( • OH), singlet oxygen ( 1 O 2 ), and sulfate radical (SO 4 •- ), which contributed 38%, 37%, and 24% were produced in EC/Fe(III)/PMS system, respectively. • OH was the dominant ROS in both EC/Fe(III)/PDS and EC/Fe(III)/HP processes. According to the analysis of SMX degradation routes and biotoxicity, abundant degradation pathways were identified in EC/Fe(III)/PMS process and lower environmental impact was achieved in EC/Fe(III)/HP process. The diversiform ROS of EC/Fe(III)/PMS system makes it exhibit greater environmental adaptability in complex water matrixes and excellent low-energy consumption performance in many organic pollutants degradation. Continuous flow treatment experiments proved that the three systems have great sustainability and practical application prospect. This work provides a strong basis for constructing suitable systems to achieve different treatment requirements., 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 B.V. All rights reserved.)

In this work, a g-C 3 N 4 supported NiCx nanoclusters catalyst (NiCx-CN) was developed, and its performance in activating peroxymonosulfate (PMS) was evaluated. Mechanism investigation stated that although singlet oxygen ( 1 O 2 ) was formed in the catalytic process, its contribution to BPA elimination was weeny. Interestingly, through the experiment with dimethyl sulfoxide as the probe, it was considered that the high-valent nickel-oxo species (Ni &+ =O), generated after the interaction of NiCx-CN and PMS, was the dominating reactive oxygen species (ROS). Theoretical calculations (DFT) implied that NiCx-CN might lose electrons to generate high-valent Ni, which was consistent with the detection of Ni 3+ on the surface of the used NiCx-CN. Besides, the prepared NiCx-CN showed advantages in resisting the interference of inorganic anions. Meanwhile, three BPA degradation routes had been proposed based on the transformation intermediates. This study will establish a new protocol for PMS activation using heterogeneous Ni-based catalysts to efficiently degrade organic pollutants via a nonradical mechanism., 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 B.V. All rights reserved.)

The regeneration of Fe(II) is the rate-limiting step in the Fenton/Fenton-like chain reactions that seriously hinder their scientific progress towards practical application. In this study, we proposed iron boride (FeB) for the first time as a new material to sustainably decompose H 2 O 2 to generate hydroxyl radicals, which can non-selectively degrade a wide array of refractory organic pollutants. Fe(II) can be steadily released by the stepwise oxidation of FeB to stimulate Fenton reaction, meanwhile, B-B bonds as electron donors on the surface of FeB effectively promote the regeneration of Fe(II) from Fe(III) species and significantly accelerate the production of hydroxyl radicals. The low generation of toxic by-products and the high utilization rate of iron species validly avoid the secondary organic/metal pollution in the FeB/H 2 O 2 system. Therefore, FeB mediated Fenton oxidation provides a novel strategy to realize a green and long-lasting environmental remediation., 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 B.V. All rights reserved.)

In this study, natural molybdenite (MoS 2 ) was applied to activate peroxymonosulfate (PMS) for the removal of atrazine (ATZ) and its degradation mechanism was investigated. Molybdenite exhibits superior catalytic performance. The best condition for atrazine degradation efficiency (>99%) was obtained with molybdenite concentration of 0.4 g/L, PMS concentration of 0.1 mM, and ATZ concentration of 12 μM within 10 min under experimental conditions. Electron paramagnetic resonance (EPR) test and chemical probe test further proved that HO • and SO 4 •- played important roles in the molybdenite/PMS system, and SO 4 •- was dominant. Meanwhile, Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) tests showed that sulfur vacancies and edge sulfur played important roles in the system. Edge sulfur was conducive to Mo 4+ exposure, while sulfur vacancy facilitated electron transfer and reduced Mo 6+ back to Mo 4+ . Combined with DFT calculation, the role of sulfur in the degradation process was verified. Besides, five ATZ degradation pathways were proposed. Finally, the degradation ability of the molybdenite/PMS system for different pollutants and in actual water bodies was also explored. This work provided ideas for exploring the degradation of organic contaminants by natural minerals., (Copyright © 2022. Published by Elsevier B.V.)

Sodium bismuthate dihydrate (NaBiO 3 .2 H 2 O, NBH) nanosheets were successfully prepared in this study using the persulfate oil bath oxidation method. Benefited from the unique layered structure of NBH, the Fe(III) as a variable valence metal ion was explored for enhancing NBH activation of peroxymonosulfate (PMS) to degrade levofloxacin (LVF) in the visible-light catalytic system. Based on results of the reactive oxygen species (ROS) quenching experiments and electron paramagnetic resonance (EPR) analysis, singlet oxygen ( 1 O 2 ) and superoxide radical (O 2 ·- ) were identified as the main ROS. The morphology, chemical structure, and optical properties of NBH were analyzed using various characterization methods. It was confirmed that Fe(III) embedded in the NBH via the ion exchange with Na, resulting in lattice oxygen vacancies on the surface of the NBH, after the formation of oxygen defect sites, reacts with PMS in the solution to produce active oxygen species with oxidizing efficiency. This study expands the technological application of NBH in the catalytic oxidation of variable valence metals, which are essential for the removal of fluoroquinolone antibiotics., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The sluggish oxidation kinetics of ferrate (Fe(VI)) at neutral and slightly alkaline pH impedes its rapid abatement of micropollutants in practical application. This work discovers that graphite (GP), a metal-free carbonaceous material, can be a promising material to improve the reactivity of Fe(VI) in the pH range of 7.0 - 9.0. The performance of the GP/Fe(VI) process for sulfamethoxazole (SMX) removal was further evaluated via altering the dosages of Fe(VI), GP, and SMX. Probe analysis and quenching experiments identified Fe(IV) and Fe(V) as the primary active species responsible for the removal of organic compounds in the GP/Fe(VI) system. The detailed activation mechanism of GP is discussed via analyzing the surface chemical changes of GP exposed to Fe(VI). It is found that the carbonyl groups on GP surface execute a critical role in Fe(VI) activation. The GP/Fe(VI) system shows powerful anti-interference ability to environmental background substances. Therefore, the new oxidation process proposed in this work holds a great application prospect for contamination remediation. Finally, we discuss the underlying degradation pathways of SMX by the GP/Fe(VI) system. This study not only develops a promising system for the removal of micropollutants but also provides an in-depth insight into the activation mechanism of metal-free carbonaceous material in Fe(VI) oxidation process., (Copyright © 2022 Elsevier B.V. All rights reserved.)

In order to accelerate the photo-Fenton reaction process of Fe(III) under visible light irradiation, BiOI was introduced into the Fe(III)/peroxydisulfate (PDS) system. The catalytic oxidation performance of vis-light/BiOI/Fe(III)/PDS system was evaluated using bisphenol AF (BPAF) as a representative organic contaminant. Within 30 min, nearly 100% of BPAF was degraded, proving that the system had an excellent ability to degrade organic pollutants in water. Free radical quenching experiments, electron spin resonance (ESR), and molecular probing experiments determined that the main reactive species in the system were hydroxyl radicals ( • OH) and sulfate radicals (SO 4 •- ). The comparative experiments showed that the degradation rates were closely related to the PDS consumption, while the Fe(II) absorbed on the surface of BiOI was responsible for the PDS consumption. The production pathway of Fe(II) was analyzed by XRD, FTIR and XPS characterization, the Fe(III) on the surface of BiOI was reduced by photogenerated electrons to generate Fe(II). The result confirmed that the reduction of Fe(III) by photogenerated electrons could effectively inhibit the recombination of electron-hole pairs, and accelerate the reduction progress of Fe(III)/Fe(II) cycle that was the rate-limiting step in PDS activation. Afterwards, a reliable mechanism for degradation of BPAF in visible light/BiOI/Fe(III)/PDS system was proposed. Finally, the influence of reactant dosages, visible light intensity, initial pH, humic acid (HA) and anions in the solution on the degradation of BPAF were discussed., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Metal leaching and catalytic stability are the key issues in Fenton-like reaction. Herein, a hollow yolk-shell nanoreactor (HYSCN) with shell confined Co species was fabricated for peroxymonosulfate (PMS) activation to degrade carbamazepine (CBZ). The uniform Co nanoparticles were completely anchored in a hollow void, further confined by a porous N-doped carbon shell. The unique construction significantly reduces Co species leaching in PMS activation and enhances catalytic stability. Co leaching came from HYSCN dropped by almost fourfold compared to CN-8 without shell confined (0.403 mg/L to 0.120 mg/L). The catalytic stability is also greatly improved, confirming the dominant role of heterogeneous catalysis in the HYSCN/PMS system. HYSCN exhibits excellent catalytic performance compared to a solid structure (SCSCN), demonstrating the significance of hollow structures. Mechanism study found that HO • , SO 4 •- and 1 O 2 induced in HYSCN/PMS system and the relative contributions were distinguished and quantified by stoichiometric methods. The UPLC-Q-TOF-MS/MS was used to identify the CBZ degraded intermediate products and the possible degradation pathway was proposed. This study will provide theoretical guidance for reducing metal leaching and improving catalytic stability in the PMS activation., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Recently, the enhancing role of hydrogen peroxide (H 2 O 2 ), a self-decay product of ferrate (Fe(VI)), on Fe(VI) reactivity has received increasing attention. In this study, we found that calcium peroxide (CaO 2 ) as a slow-releasing reagent of H 2 O 2 could also enhance the Fe(VI) performance for removing sulfamethoxazole (SMX). Compared with sole Fe(VI), sole CaO 2 and Fe(VI)-H 2 O 2 systems, the Fe(VI)-CaO 2 system showed higher reactivity to remove SMX. The radical scavenger and chemical probe test results indicated that the better oxidation performance of Fe(VI)-CaO 2 system than Fe(VI) alone was ascribed to the generation of Fe(Ⅳ) and Fe(Ⅴ) rather than • OH. In addition, the performance of Fe(VI)-CaO 2 system for degradation of contaminants was also superior to Fe(VI)-Na 2 SO 3 , Fe(VI)-NaHSO 3 and Fe(VI)-Na 2 S 2 O 3 systems under the same experimental conditions. Moreover, the effects of critical operating parameters, inorganic anions, inorganic cations, and humic acid on the degradation of SMX by Fe(VI)-CaO 2 system were revealed. The Fe(VI)-CaO 2 system exhibited good applicability in authentic water. Finally, the underlying degradation intermediates of SMX by Fe(VI)-CaO 2 system and their toxicity were confirmed. In conclusion, this study provides a new strategy for enhancing the oxidation capacity of Fe(VI) and comprehensively reveals the oxidation mechanism., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In this study, the effects of ferric ion (Fe 3+ ) on the degradation of atrazine (ATZ) in Bi 2 MoO 6 /peroxymonosulfate (PMS) system under visible light irradiation was investigated. With the addition of Fe 3+ , ATZ in the visible light/Bi 2 MoO 6 /PMS system degraded rapidly after 20 min treatment (removal rate > 99%). The enhancement of ATZ removal can be attributed to the role of Fe 3+ . As an electron transfer mediator, Fe 3+ not only inhibits the recombination of photo-charges and prolongs the life of photogenerated carriers, but also promotes the activation of PMS by accelerating the electron transfer from Bi 2 MoO 6 to PMS. The generation of • OH and SO 4 •- in the system was determined via electron paramagnetic resonance (EPR) technology and quenching experiments. Furthermore, the characterization of Bi 2 MoO 6 before and after reaction, influence of the reaction parameters (i.e., catalyst and PMS dosages, Fe 3+ and ATZ concentration, initial pH), influence of inorganic anions and humic acid, and the recyclability of catalyst in the vis/Bi 2 MoO 6 /PMS/Fe 3+ system was also investigated. Additionally, the existence of Fe 3+ also exhibits a wide selectivity for the degradation of different pollutants and high treatment efficiency. In general, the vis/Bi 2 MoO 6 /PMS/Fe 3+ system demonstrated the potential as an efficient, economical, and environment-friendly water treatment process., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Among all homogeneous catalysts, cobalt ions show the highest catalytic performance for the activation of peroxymonosulfate (PMS). Herein, we report a Co 2+ /PMS/H 3 BO 3 system that can effectively generate reactive oxygen species (ROS) with ultra-low Co 2+ dosage (5 μg/L). Co 2+ /PMS/H 3 BO 3 system showed ultrafast reactivity and wide applicability for various pollutants. Sulfamethoxazole (SMX, 2 mg/L) could be completely removed within 5 min, and the corresponding k obs reached up to 1.1239 min -1 . The introduction of H 3 BO 3 significantly promoted the generation of ROS. The turnover frequency (TOF) calculated through dividing k obs by the cobalt ions concentration is as high as 224.78 min -1 , which is much higher than most of the current research. Through a series of theoretical and experimental analyses, the complex of H 2 BO 3 - B(OH) 5 B(OH) 3 - ) was inferred to be the key substance that led to the excellent performance of the system. This work provides new insights into the Co 2+ /PMS system in the presence of borate buffer., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Currently, many catalysts are inconvenient to separate from water, and the solvents used in the preparation process are not environmentally friendly, resulting in low recovery efficiency and secondary pollution. In this study, the magnetic and porous regenerated cellulose/carbon nanotubes/Fe 3 O 4 nanoparticles (RC/CNTs/Fe 3 O 4 NPs) composites were synthesized for activation of peroxydisulfate (PDS) in a green alkaline-urea system. The RC/CNTs/Fe 3 O 4 NPs-PDS system achieved 100% removal of bisphenol A compared with CNTs (~64.6%), RC (~0%) or Fe 3 O 4 NPs (~0%), which was closely related to the introduction of defects and functional groups, nitrogen doping and conductive networks. Interestingly, the strong interaction between CNTs and the sheath-like protective layer formed by urea on the cellulose surface promotes the introduction of nitrogen into the composites at the preparation temperature of 70 °C. Moreover, the mechanism of the system was found to be a typical non-radical pathway. Fortunately, there is no leaching of iron ions in the system, and the effects of the actual waterbody, initial pH, and different anions are negligible. The recycling and separation experiments revealed the practicality and superiority of the composite. This work provides a feasible and sustainable strategy for the application of natural cellulose-supported catalysts., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Recently, an increasing number of works have been reported about iron-based materials applied as catalysts in peroxide activation processes to degrade pollutants in water. Iron-based catalysts include synthetic and natural iron-based materials. However, some synthetic iron-based materials are difficult to scale up in the practical applications due to high cost and serious secondary environmental pollution. In contrast, natural iron-based minerals are more available and cheaper, and also hold a great promise in peroxide activation processes for pollutant degradation. In this review, we classify different natural iron-based materials into two categories: iron oxide minerals (e.g., magnetite, hematite, and goethite,), and iron sulfide minerals (e.g., pyrite and pyrrhotite,). Their overview applications in peroxide activation processes for pollutant degradation in wastewaters are systematically summarized for the first time. Moreover, the peroxide activation mechanisms induced by natural minerals, and the influences of reaction conditions in different systems are discussed. Finally, the application prospects and existing drawbacks of natural iron-based minerals in the peroxide activation processes for wastewater treatment are proposed. We believe this review can shed light on the application of natural iron-based minerals in peroxide activation processes and present better perspectives for future researches., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Single-atom catalysts (SACs) have attracted considerable attention from researchers because of their distinct structures and characteristics, especially in maximizing atomic utilization and elevating the intrinsic catalytic activity. More recently, SACs have been becoming a burgeoning area of the environmental field and are extensively applied to remove various refractory organic pollutants. This review summarizes the emerging synthetic and characterization strategies of SACs and analyzes their development tendency. Besides, the application of SACs in advanced oxidation processes (AOPs, e.g., catalysis of H 2 O 2 , activation of persulfates and photocatalysis) is discussed. The excellent removal of pollutants depends on the fast generation of reactive oxygen species (SO 4 •- , • OH, 1 O 2 , and O 2 •- ). The advantages of SACs in AOPs are summarized, and constructive opinions are put forward for the stability and activity of the catalyst. Finally, the opportunities and challenges faced by SACs and its future development direction in the AOPs catalytic field are proposed., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The generation of sludge is the main issue in iron-based electrochemical techniques. Interestingly, in this study, the effluent was totally limpid and iron sludge did not generate when dissolved silicate (Na 2 SiO 3 ) was used as the electrolyte in an electrolysis catalyzed ozone (ECO-Na 2 SiO 3 ) system. More importantly, the pseudo-first-order rate constants (0.112 min -1 ) for DMAC degradation in ECO-Na 2 SiO 3 process was much higher than those of ECO systems using other electrolytes. An inhibition film formed on the iron electrode surface was identified to inhibit excess corrosion of iron electrodes and efficiently catalyze decomposition of ozone simultaneously. It was confirmed that hydroxyl radical ( • OH) played a dominant role for the degradation of DMAC, and O 2 •- and H 2 O 2 were also contained in ECO-Na 2 SiO 3 system. The contributions of contained oxidative reactions in ECO-Na 2 SiO 3 system were quantitatively evaluated. Finally, the degradation pathway of DMAC was proposed. This work provides an effective way for protecting electrode from corrosion in electrochemical process., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A series of in-situ carbon-doped TiO 2 (C x /TiO 2 ) composites with a porous and crystalline structure were successfully synthesized via one-step and low-temperature calcination of titanium metal-organic framework (MOF), MIL-125(Ti). The resultant materials were comprehensively investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), N 2 adsorption-desorption measurements, UV-vis diffuse reflectance spectrum (DRS), photoluminescence (PL) spectra and photoelectrochemical measurements, and their photocatalytic activities for bisphenol A (BPA) degradation were assessed. Compared with the benchmark TiO 2 photocatalyst (P25), the C x /TiO 2 composite material with high specific surface, lower band gap, and reduced photogenerated electron hole ratio exhibited outstanding photodegradation activity and durability for BPA, which could be attributed to the combined effect of co-doping of multiple carbon species (substituent carbon and carbonate) and porous structure. During BPA degradation, the holes and superoxide radicals were the primary role oxidative species in the reaction process. Therefore, this new efficient photocatalyst is promising candidate for photodegradation of organic pollutants., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this work, cobalt-nickel powder (Co-NP) synthesized through electroless plating was used as a heterogeneous bimetallic catalyst for peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX) in the aqueous phase. Compared with different oxidation systems and different catalysts, it was proved that Co-NP had excellent catalytic ability, fast electron transfer rate and good stability. The effects of key parameters (initial pH, SMX concentration, catalyst and PMS dosages) on SMX degradation and ion leaching were studied in detail. Furthermore, the sensitivity of inorganic anions and different pollutants towards the Co-NP/PMS system was studied to investigate its application in natural water bodies. Quenching test showed that the main reactive oxygen species generated during the reaction were OH and SO 4 - , of which SO 4 - played a predominating role. Combined with XPS analysis, the activation mechanism was concluded that free radicals were mainly generated through the valence change of Co and Ni. Based on the seven intermediates measured through ultrahigh performance liquid chromatograph-mass spectrometry (UPLC-QTOF-MS/MS), the possible degradation pathways of SMX were proposed. Notably, this study provided a new kind of supporter for advanced oxidation processes and electroless plating technology., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this study, bismuth molybdate (Bi 2 MoO 6 ) nanosheets were prepared via a facile hydrothermal method and applied to activate peroxymonosulfate (PMS) for atrazine (ATZ) elimination under visible light irradiation. An effective photocatalytic synergy was observed in vis/Bi 2 MoO 6 /PMS system. The Bi 2 MoO 6 catalyst showed an excellent stability and extremely low metal leaching in the vis/Bi 2 MoO 6 /PMS system which were characterized by XRD, XPS, HRTEM, SEM and FT-IR technologies. Besides, the influence of operation parameters (i.e., Bi 2 MoO 6 dosage, PMS concentration, initial pH, ATZ concentration, co-existing anions, and humic acid) on the removal of ATZ were also investigated in detail. The best ATZ degradation efficiency (> 99 %) was obtained with Bi 2 MoO 6 dosage of 0.6 g/L, PMS concentration of 0.8 mM, and ATZ concentration of 2.5 mg/L after 60 min. UV-vis DRS and Mott-Schottky analysis were taken to evaluate the band structure of Bi 2 MoO 6 . Trapping experiments and EPR detection demonstrated that superoxide radicals, hydroxyl radicals, sulfate radicals and h + both contributed to ATZ degradation, of which hydroxyl radical OH) and h + were the major species. Besides, the performance of vis/Bi 2 MoO 6 /PMS system for different pollutant removal was also investigated. Finally, the possible degradation products were monitored by UPLC-QTOF-MS/MS and the pathways of ATZ degradation were put forward. Overall, the vis/Bi 2 MoO 6 /PMS system shows the potential for the removal of organic pollutants in environmental remediation., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Expanded graphite (EG) immobilized nickel ferrite (NiCo 2 O 4 ) was successfully constructed by a simple hydrothermal approach and applied for the degradation of sulfamethoxazole (SMX) in model wastewater by peroxymonosulfate (PMS) activation. The features of prepared catalysts were characterized by SEM, TEM, EDS, XRD, BET, TPD and XPS techniques. The influences of several critical parameters including the prepared NiCo 2 O 4 -EG dosages, PMS concentrations, temperature, initial solution pH and inorganic ions on SMX removal were studied in details. In particular, the synthesized NiCo 2 O 4 -EG exhibits excellent catalytic performances for SMX depredation over a wide pH range (pH 3.0-11.0). Besides, the transformation of various reactive oxygen species (SO 4 - , HO, O 2 - and 1 O 2 ) with the change of initial pH was investigated by the electron paramagnetic resonance (EPR) and quenching tests. In addition, twelve major degradation intermediates of SMX were detected by UPLC-QTOF-MS/MS. Finally, the PMS activation mechanism in NiCo 2 O 4 -EG/PMS system by the synergistic coupling of EG and NiCo 2 O 4 were put forward. In brief, this work provided a promising and potential catalyst for PMS activation to remove SMX from wastewater., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this work, the cellulose-enriched mesocarp of tangerine peels (TP) and the lignin-enriched epicarp of the peels (e-TPs) were used as examples to unveil the link between the basic components (cellulose, hemicellulose and lignin) in lignocellulosic biomass and catalytic activity of biochar towards peroxymonosulfate (PMS) activation. The TP biochar exhibits sheet-like morphology and high porosity, while the e-TPs biochar shows a bulk morphology. Accordingly, the former outperformed the latter in terms of catalytic degradation of phenol with PMS, attributing to the higher content of cellulose than lignin in the TP precursor, which was further supported by comparing the catalytic activity of biochar prepared from binary mixtures containing different proportions of cellulose and lignin. Nonradical oxidation pathway based on singlet oxygen ( 1 O 2 ) and electron-transfer mechanism was involved in the TP biochar/PMS system and the key role of CO group in biochar for 1 O 2 generation was computationally demonstrated. Additionally, the unique porous structure and surface chemistry of TP biochar endows it an excellent adsorbent for various organic pollutants. Herein, this work provides an insight into the effect of lignocellulosic biomass source on the catalytic property of biochar, which would be beneficial to screen lignocellulosic biowastes to prepare high-performance biochar for water remediation., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Annular iron sheet (AIS), playing a dual role of anode electrode and source of activator, was combined with electrolysis technology for the activation of persulfate to improve the degradation of 2, 4-dinitrophenol (DNP) in aqueous solution. In this study, effects of current density (0-10.0mA/cm 2 ), persulfate (PS) dosage (0-8.0mM), initial pH (3.0-11.0), reaction temperature (25-60°C) and reaction time (0-30min) on COD removal of DNP in aqueous solution were investigated, respectively. COD removal reached its maximal value (63.4%) after 15min treatment due to the synergistic effect in electro/AIS/PS system under the optimal conditions. Furthermore, comparative studies of 7 different experimental processes were setup. In addition, the reasonable DNP degradation pathway was proposed based on intermediates detected by HPLC. According to characterization analysis of SEM-EDS, XRD and XPS of the generated flocculation in electro/AIS/PS system, the possible reaction mechanism was proposed in detail. In a word, the electrolysis process coupled with annular iron sheet as anode activating persulfate technology shows a significant synergetic effect in enhancing degradation of DNP in aqueous solution., (Copyright © 2017 Elsevier B.V. All rights reserved.)

To remove the toxic and refractory pollutants in the phthalonitrile resin wastewater and improve its biodegradability, a combined process (i.e., CaCl2+AA+Fe/Cu/air) was developed to pretreat this wastewater obtained from a phthalonitrile resin manufacturing plant in southwestern China. First, CO3(2-) was precipitated and removed by adding CaCl2. Furthermore, its ultra-high concentrated NO2(-) (22.7±0.1 g/L) was reduced into N2 by adding amidosulphonic acid (AA). Meanwhile, two control experiments were setup to confirm the superiority of the combined process (i.e., CaCl2+AA). Subsequently, the wastewater was further treated by Fe/Cu/air process after the removal of CO3(2-) and NO2(-). The results suggest that the developed method not only could effectively remove the ultra-high concentrated CO3(2-) (>99%) and NO2(-) (>99%), but also could obtain high COD (58.8%) and colority (95.2%) removal efficiencies. Meanwhile, B/C ratio of this wastewater increased from 0.19 to 0.45, which suggests the biodegradability also was improved significantly. Finally, the high treatment efficiency was mainly attributed to the synergistic effects of CaCl2, AA and Fe/Cu/air. Therefore, the combined process is a promising pretreatment process for the ultra-high concentrated wastewater from phthalonitrile resin manufacturing., (Copyright © 2016 Elsevier B.V. All rights reserved.)

To decompose or transform the toxic and refractory reverse osmosis (RO) concentrate and improve the biodegradability, 1stFe/Cu/air-Fenton-2ndFe/Cu/air were developed to treat RO concentrate obtained from an amino acid production plant in northern China. First, their operating conditions were optimized thoroughly. Furthermore, 5 control experiments were setup to confirm the superiority of 1stFe/Cu/air-Fenton-2ndFe/Cu/air and synergistic reaction between Fe/Cu/air and Fenton. The results suggest that the developed method could obtain high COD removal (65.1%) and BOD5/COD ratio (0.26) due to the synergistic reaction between Fe/Cu/air and Fenton. Under the optimal conditions, the influent and effluent of 1stFe/Cu/air-Fenton-2ndFe/Cu/air and 5 control experiments were analyzed by using UV, FTIR, EEM and LC, which confirm the superiority of 1stFe/Cu/air-Fenton-2ndFe/Cu/air. Therefore, the developed method in this study is a promising process for treatment of RO concentrate., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In order to further compare the degradation capacity of Fe(0) and Fe/Cu bimetallic system under different aeration conditions, the mineralization of PNP under different aeration conditions has been investigated thoroughly. The results show that the removal of PNP by Fe(0) or Fe/Cu system followed the pseudo-first-order reaction kinetics. Under the optimal conditions, the COD removal efficiencies obtained through Fe(0) or Fe/Cu system under different aeration conditions followed the trend that Fe/Cu (air)>Fe/Cu (N2: 0-30 min, air: 30-120 min)>control-Fe (air)>Fe/Cu (without aeration)>Fe/Cu (N2)>control-Fe (N2). It revealed that dissolved oxygen (DO) could improve the mineralization of PNP, and Cu could enhance the reactivity of Fe(0). In addition, the degradation of PNP was further analyzed by using UV-vis, FTIR and GC/MS, and the results suggest that Fe/Cu bimetallic system with air aeration could completely break the benzene ring and NO2 structure of PNP and could generate the nontoxic and biodegradable intermediate products. Meanwhile, most of these intermediate products were further mineralized into CO2 and H2O, which brought about a high COD removal efficiency (83.8%). Therefore, Fe/Cu bimetallic system with air aeration would be a promising process for toxic refractory industry wastewater., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In this study, the US-ZVI system was used to produce the strong reductants including H and nascent Fe(2+) ions to eliminate the toxicity of the high concentration p-nitrophenol (PNP) wastewater. The effect of the reactor structure, initial pH, ZVI dosage, ultrasonic power and initial PNP concentration on the removal efficiency of PNP from water was investigated intensively. The results show that a higher removal rate can be obtained by using a conical structure reactor, and the lower initial pH can aid the acceleration of PNP removal rate by using US-ZVI system. Furthermore, the removal efficiencies of PNP increased obviously with the increase of initial ZVI concentration from 0 to 15 gL(-1). Also, the treatment capacity of ZVI was enhanced remarkably by the ultrasonic irradiation, and the US-ZVI system can maintain high treatment efficiency for the high concentration PNP wastewater (500-10,000 mgL(-1)). Meanwhile, the high removal efficiency of PNP was mainly resulted from the synergistic reaction of ZVI and US. At last, the main degradation product (i.e., p-aminophenol) was detected by gas chromatography-mass spectrum (GC-MS). Thus, the reaction pathway of PNP in the US-ZVI system is proposed as a reducing process by the H and nascent Fe(2+) ions., (Copyright © 2013 Elsevier B.V. All rights reserved.)

As past studies presented, there is obvious defect that the fillers in the Fe(0)/GAC reactor begin to be passive after about 60 d continuous running, although the complicated, toxic and refractory ABS resin wastewater can be pretreated efficiently by the Fe(0)/GAC reactor. During the process, the Fe(3)(PO(4))(2) and FePO(4) crystals with high density in the passive film are formed by the reaction between PO(4)(3-) and Fe(2+)/Fe(3+). Meanwhile, they obstruct the formation of macroscopic galvanic cells between Fe(0) and GAC, which will lower the wastewater treatment efficiency of Fe(0)/GAC reactor. In this study, in order to remove the Fe(3)(PO(4))(2) and FePO(4) crystals on the surface of the passive fillers, the bacteria were acclimated in the passive Fe(0)/GAC reactor. According to the results, it can be concluded that the Fe(3)(PO(4))(2) and FePO(4) crystals with high density in the passive film could be decomposed or removed by the joint action between the typical propionic acid type fermentation bacteria and sulfate reducing bacteria (SRB), whereas the PO(4)(3-) ions from the decomposition of the Fe(3)(PO(4))(2) and FePO(4) crystals were released into aqueous solution which would be discharged from the passive Fe(0)/GAC reactor. Furthermore, the remained FeS and sulfur (S) in the passive film also can be decomposed or removed easily by the oxidation of the sulfur-oxidizing bacteria. This study provides some theoretical references for the further study of a cost-effective bio-regeneration technology to solve the passive problems of the fillers in the zero-valent iron (ZVI) or Fe(0)/GAC reactor., (Copyright © 2012 Elsevier B.V. All rights reserved.)