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Currently, various strategies have been applied to activate persulfate (PS) for contaminant removal from water. However, the background phosphate ions in water affect PS activation and organic degradation, and the mechanism of their influence on the processes is still controversial. In this review, the possible effects of different phosphate forms (HPO 4 2- , H 2 PO 4 - , and PO 4 3- ) on PS activation and contaminant degradation were systematically evaluated and summarized. Specifically, HPO 4 2- promotes contaminant degradation in direct peroxymonosulfate (PMS) oxidation and thermal/PMS systems, while it exhibits inhibition to thermal/peroxodisulfate (PDS) and ultraviolet (UV)/PDS systems. Meanwhile, H 2 PO 4 - inhibits most oxidation processes based on PMS and PDS, except for non-metal dominated and metal assisted PMS systems. Coexisting HPO 4 2- and H 2 PO 4 - could present beneficial effects in thermal, Co 2+ and non-metal activated and metal assisted PMS systems. Nevertheless, their inhibitory effects were found in direct PMS oxidation, UV/PMS (or PDS) and metal dominated PMS systems. Generally, phosphate ions inhibit PMS/PDS activation through competing adsorption with PMS or PDS on the solid surface, forming a complex with metal ions, as well as occupying active sites on solid catalysts. In addition, phosphate ions can quench radicals for reduced degradation of contaminants. However, phosphate ions could weaken the bond dissociation energy via combining with PMS and contaminants or form a complex with Co 2+ , thus displaying a facilitative effect. This review further discusses major challenges and opportunities of PS activation with co-existing phosphates and will provide guidance for better PS utilization in real water treatment practice., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Persulfate-based nonradical oxidation processes (PS-NOPs) are appealing in wastewater purification due to their high efficiency and selectivity for removing trace organic contaminants in complicated water matrices. In this review, we showcased the recent progresses of state-of-the-art strategies in the nonradical electron-transfer regimes in PS-NOPs, including design of metal and metal-free heterogeneous catalysts, in situ/operando characterization/analytical techniques, and insights into the origins of electron-transfer mechanisms. In a typical electron-transfer process (ETP), persulfate is activated by a catalyst to form surface activated complexes, which directly or indirectly interact with target pollutants to finalize the oxidation. We discussed different analytical techniques on the fundamentals and tactics for accurate analysis of ETP. Moreover, we demonstrated the challenges and proposed future research strategies for ETP-based systems, such as computation-enabled molecular-level investigations, rational design of catalysts, and real-scenario applications in the complicated water environment. Overall, this review dedicates to sharpening the understanding of ETP in PS-NOPs and presenting promising applications in remediation technology and green chemistry.

Low efficiency in energy conversion has long been the bottleneck in sonochemistry-based water treatment technologies. In this work, we reported a simple and efficient strategy by introducing mechanical agitation into a low powered ultrasonic system to facilitate the production of cavitation bubbles. The coupled system remarkably intensifies the evolution of reactive oxygen species (ROS) for degradation of refractory organic pollutants. We in-situ monitored the generation of hydroxyl radicals (•OH) by selective scavenging tests and chemical trapping experiments. The operational factors such as rotation speed, gas atmosphere, solution temperature and pH were carefully evaluated for their impacts on the degradation of a plastic microcontaminant, diethyl phthalate (DEP). It was found that the degradation efficiency is closely related to the population of cavitation bubbles in the solution, which was collaboratively governed by the aforementioned factors. A high mechanical agitation speed (600 rpm), great solubility of inert gas atmosphere (Argon), and low reaction temperature (15 ºC) are beneficial to the generation of cavitation bubbles and the associated production of ROS. This work shows a facile strategy to intensify the mechanical energy-to-chemical conversion and provides new mechanistic insights into the ultrasound-based advanced oxidation without external chemical inputs., 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 © 2021. Published by Elsevier Ltd.)

Recently, antibiotics with high ecotoxicity have been ubiquitously detected in aquatic environment. The photocatalysis/persulfate-oxidation hybrid (PPOH) system has been proved as a promising strategy for antibiotic degradation. The efficient antibiotic removal is due to the favorable synergistic effects between photocatalysis and persulfate activation. To our best knowledge, relevant reviews on the photo-assisted persulfate activation (PPA) system have been reported, while the research progress on persulfate-assisted photocatalysis (PAP) and concurrent photocatalysis-persulfate activation (CPPA) systems for antibiotic wastewater treatment have yet been summarized. Hence, the PPOH systems are categorized into PPA, PAP and CPPA systems in this review. Besides, the performance of antibiotic degradation and internal mechanism in the coupled oxidation system are summarized and analyzed comprehensively. Finally, conclusions and future prospects of PPOH systems in antibiotic wastewater treatment are proposed. This study provides an overview of PPOH system and outlines the future research direction of the system in practical treatment of antibiotic wastewater., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Clean water production calls for highly efficient and less energy-intensive technologies. Herein, a novel concept of a sequential ultrafiltration-catalysis membrane is developed by loading Co 3 O 4 /C@SiO 2 yolk-shell nanoreactors into the fingerlike channels of a polymeric ultrafiltration membrane. Such a sequenced structure design successfully integrates selective separation with peroxymonosulfate-based catalysis to prepare a functionalized molecular sieve membrane, which exhibits excellent decontamination performance toward multipollutants by filtering the water matrices containing humic acid (HA) and bisphenol A (BPA). In this study, 100% rejection of HA and 95% catalytic degradation of BPA were achieved under a low pressure of 0.14 MPa and an ultrahigh flux of 229 L m -2 h -1 , corresponding to a retention time of 3.1 s. Notably, the removal performance of multiple pollutants essentially depends on the ordered arrangement of ultrafiltration and catalysis. Moreover, the flow-through process demonstrated significant enhancement of BPA degradation kinetics, which is 21.9 times higher than that of a conventional batch reactor. This study provides a novel strategy for excellent removal of multiple pollutants in water.

Heterogeneous electro-Fenton (HEF) reaction has been considered as a promising process for real effluent treatments. However, the design of effective catalysts for simultaneous H 2 O 2 generation and activation to achieve bifunctional catalysis for O 2 toward •OH production remains a challenge. Herein, a core-shell structural Fe-based catalyst (FeNC@C), with Fe 3 C and FeN nanoparticles encapsulated by porous graphitic layers, was synthesized and employed in a HEF system. The FeNC@C catalyst presented a significant performance in degradation of various chlorophenols at various conditions with an extremely low level of leached iron. Electron spin resonance and radical scavenging revealed that •OH was the key reactive species and Fe IV would play a role at neutral conditions. Experimental and density function theory calculation revealed the dominated role of Fe 3 C in H 2 O 2 generation and the positive effect of FeN x sites on H 2 O 2 activation to form •OH. Meanwhile, FeNC@C was proved to be less pH dependence, high stability, and well-recycled materials for practical application in wastewater purification.

Nanocarbon-based persulfate oxidation emerges as a promising technology for the elimination of organic micropollutants (OMPs). However, the nature of the active site and its working mechanism remain elusive, impeding developments of high-performance oxidative technology for water treatment practice. Here, we report that defect-rich carbon nanotubes (CNTs) exhibit a superior activity in the activation of peroxymonosulfate (PMS) for OMP oxidation. Quantitative structure-activity relationship studies combined with theoretical calculations unveil that the double-vacancy defect on CNTs may be the intrinsic active site, which works as a conductive bridge to facilitate the potential difference-dominated electron transfer from the highest occupied molecular orbital of OMPs to the lowest unoccupied molecular orbital of PMS. Based on this unique mechanism, the established CNTs@PMS oxidative system achieves outstanding selectivity and realizes the target-oriented elimination of specific OMPs in a complicated aquatic environment. This work sheds new light on the mechanism of carbocatalysis for selective oxidation and develops an innovative technology toward remediation of practical wastewater.

Enhanced elimination of aniline in aqueous solution was achieved by coupling electrosorption of aniline and electrochemical activation of peroxydisulfate (PDS) at multi-walled carbon nanotube (MWCNT) cathode, in which a synergistic effect occurred. It was found that PDS could be effectively activated under a small voltage at MWCNT cathode owing to the specific pore structures of MWCNTs. A nonradical oxidation pathway instead of radical-based oxidation was proposed from the cathodic activation of PDS, wherein PDS molecules with a modified electronic structure was suggested to be the principal reactive species. Meanwhile, the influences of various operation parameters such as electrode potential, PDS concentration, presence of chloride ions on the elimination efficiency, and the stability of MWCNT electrode were also attempted. Therefore, the electrochemical activation of PDS by MWCNT cathode is a promising energy-saving method for the treatment of organic pollutants in wastewater., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Adsorptive removal of a toxic sulfonamide antibiotic, sulfachloropyradazine (SCP), from aqueous solution was studied on several metal organic frameworks, UiO-66 and ZIF-67, for the first time. UiO-66 exhibited a much higher adsorption capacity than ZIF-67, fast kinetics, and easy regeneration for reuse, demonstrating as a promising adsorbent in wastewater treatment processes. The batch adsorption shows an adsorption capacity of SCP at 417mg/g on UiO-66. The kinetic adsorption of SCP on UiO-66 reached equilibrium just in 10min and the kinetics fits accurately with a pseudo 2nd order model. A plausible mechanism was proposed based on pH effect, pK a value of the adsorbate and Zeta potential of UiO-66. The high adsorption is mainly contributed to hydrophobicity and π-π interactions along with electrostatic interactions. Thermodynamic studies show the spontaneous adsorption and exothermic process. The easy regeneration and high adsorption capacity confirms structural stability of the robust UiO-66 in wastewater treatment processes, making it suitable for a large scale application., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Novel uniform ellipsoid α-Mn2O3@α-MnO2 core/shell (McMs) nanocomposites were prepared via a hydrothermal process with a shape-control protocol followed by calcination at different temperatures. The properties of the composites were characterized by a number of techniques such as thermogravimetric analysis (TGA), X-ray diffraction (XRD), N2 adsorption, and scanning electron microscopy (SEM). The core/shell materials were much effective in heterogeneous oxone(®) activation to generate sulfate and hydroxyl radicals for degradation of aqueous phenol. The McMs composites demonstrated catalytic activity for 100% phenol decomposition in short duration varying between 20 and 120 min, much higher than that of homogeneous Mn(2+) system with 95% phenol degradation in 120 min. They also showed a higher activity than single-phase α-Mn2O3 or α-MnO2. The catalytic activity of phenol degradation depends on temperature, oxone(®) concentration, phenol concentration, and catalyst loading. The catalysts also showed a stable activity in several cycles. Kinetic study demonstrated that phenol degradation reactions follow a first order reaction on McMs catalysts giving activation energies at 32.1-68.8 kJ/mol. With the detection of radicals by electron paramagnetic resonance (EPR), the generation mechanism was proposed., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Barley straw, an agricultural waste, was chemically modified and evaluated for the removal of emulsified oils from aqueous solution. The chemical modification was performed using NaOH and a cationic surfactant, hexadecylpyridinium chloride monohydrate (CPC). The surface textural and chemical properties of the surfactant modified barley straw (BMBS) were characterized by N(2) adsorption, FT-IR, SEM and water soluble mineral content. The adsorption tests were carried out in batch adsorption system for removal of standard mineral oil (SMO) and canola oil (CO) from water. For both emulsified oils in wastewater, adsorption was found to be strongly related with solution pH. The isotherm study indicated that emulsified oil adsorption on BMBS could be fitted well with the Langmuir model other than Freundlich model. The maximum adsorption capacity for CO and SMO at 25 degrees C determined from the Langmuir isotherm is 613.3 and 584.2 mg g(-1), respectively. Desorption tests in water solution show that oil is strongly bonded with adsorbent and desorption is only about 1-2% in 24 h.

Fly ash is solid waste from combustion process, containing oxide minerals and unburned carbon. In this investigation, fly ash has been separated into metal oxide mineral section and unburned carbon. The fly ash with different contents of unburned carbon was employed for humic acid adsorption to investigate the influence of unburned carbon on adsorption. It is found that metal oxides and unburned carbon in fly ash exhibit significant difference in humic acid adsorption. The unburned carbon plays the major role in adsorption. Higher content of unburned carbon in fly ash results in higher surface area and thus higher humic acid adsorption. Fly ash and unburned carbon exhibit adsorption capacity of humic acid of 11 and 72 mg/g, respectively, at 30 degrees C, pH 7. Humic acid adsorption is also affected by ion strength, pH, and temperature. The thermodynamic calculations indicate that the adsorption is endothermic nature with DeltaH(0) and DeltaS(0) as 5.79 kJ/mol and 16.0 J/K mol, respectively.

Solid-state conversion of fly ash to an amorphous aluminosilicate adsorbent (geopolymer) has been investigated under different conditions and the synthesised material has been tested for Cu2+ removal from aqueous solution. It has been found that higher reaction temperature and Na:FA ratio will make the adsorbents achieving higher removal efficiency. The adsorbent loading and Cu2+ initial concentration will also affect the removal efficiency while the adsorption capacity exhibits similarly at 30-40 degrees C. The adsorption capacity of the synthesised adsorbent shows much higher value than fly ash and natural zeolite. The capacity is 0.1, 3.5 and 92 mg/g, for fly ash, natural zeolite, and FA derived adsorbent, respectively. The kinetic studies indicate that the adsorption can be fitted by the second-order kinetic model. Langmuir and Freundlich isotherms also can fit to the adsorption isotherm.

Natural zeolite and synthetic zeolite, MCM-22, were employed as effective adsorbents for a basic dye, methylene blue, removal from wastewater. Two methods, Fenton oxidation and high temperature combustion, have been used for regeneration of used materials. It is found that MCM-22 exhibits equilibrium adsorption at 1.7 x 10(-4) mol g(-1), much higher than the adsorption of natural zeolite (5 x 10(-5) mol g(-1)) at initial dye concentration of 2.7 x 10(-5)M and 30 degrees C. Solution pH will affect the adsorption behaviour of MCM-22. Higher solution pH results in higher adsorption capacity. The regenerated adsorbents show different capacity depending on regeneration technique. Physical regeneration by high temperature combustion will be better than chemical regeneration using Fenton oxidation in producing effective adsorbents. Regeneration of MCM-22 by high temperature treatment can make the adsorbent exhibit comparable or superior adsorption capacity as compared to the fresh sample depending on the temperature and time. The optimal temperature and time will be 540 degrees C and 1h. The Fenton oxidation will recover 60% adsorption capacity. For natural zeolite, regeneration can not fully recover the adsorption capacity with the two techniques and the regenerated natural zeolites by the two techniques are similar, showing 60% adsorption capacity of fresh sample. Kinetic studies indicate that the adsorption follows pseudo-second-order kinetics.

MCM-22 was employed as an effective adsorbent for removal of basic dyes including methylene blue, crystal violet, and rhodamine B from aqueous solution. The adsorption kinetics and isotherms were investigated. The adsorption capacity of MCM-22 for three dyes follows an order of MB > CV approximately RB. Kinetic studies indicate that the adsorption follows the pseudo second-order kinetics and the adsorption is a two-step diffusion process with film diffusion dominating the process. The adsorption isotherm can be well fitted by both the Langmuir and the Freundlich models. Thermodynamic calculations suggest that the adsorption of basic dyes on MCM-22 is an endothermic reaction.

Fly ash, natural zeolite, and unburned carbon separated from fly ash have been employed as low-cost adsorbents for dye adsorption in methylene blue-containing wastewater. It is found that the unburned carbon exhibits a much higher adsorption capacity than raw fly ash and natural zeolite. The adsorption capacities of fly ash, natural zeolite, and unburned carbon for methylene blue are 2 x 10(-5), 5 x 10(-5), and 2.5 x 10(-4) mol/g, respectively. Investigation also indicates that adsorption is influenced by initial dye concentration, particle size, dye solution pH, and adsorption temperature. Adsorption on unburned carbon increases with the initial dye concentration, solution pH, and temperature, but reduces with the increasing particle size. Kinetic studies show that adsorption of methylene blue on fly ash, natural zeolite, and unburned carbon can be best described by the pseudo-second-order adsorption model and that adsorption is a two-step diffusion process. The apparent activation energies for methylene blue adsorption on unburned carbon in the first and second diffusion processes are 12.4 and 39.3 kJ/mol, respectively.

Rhodamine B (RhB) is extensively used for dyeing purposes, and cannot be completely removed using traditional water treatment technologies. Here, we report for the first time the photodegradation of RhB using nitrogen-doped titanium dioxide (N-TiO2) on reduced graphene oxide (rGO) composite (N-TiO2/rGO). The work primarily highlights the synergistic effect of the incorporation of N-TiO2 and rGO and its kinetic study for the photodegradation of RhB. The N-TiO2/rGO composite was synthesized by dispersing titanium(IV) isopropoxide and urea, followed by annealing treatment via the hydrothermal method with rGO. Scanning electron microscopy (SEM) images illustrated that N-TiO2 particles with an irregular round shape and white color were dispersed onto the rGO surface. X-Ray diffraction (XRD) patterns revealed that N-TiO2/rGO composite showed an anatase phase of TiO2 with a diffraction peak of 2θ = 25.622°. The gas sorption analysis (GSA) showed that N-TiO2/rGO had surface area, pore volume, and pore size of 53.393 m2/g, 0.096 cc/g, and 3.588 nm, respectively. The thermogravimetric-differential thermal analysis (TG-DTA) showed an anatase phase of TiO2 that appeared at a temperature of 200–500 °C, with a weight loss of 2.50%. According to the ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) study, TiO2, N-TiO2, and N-TiO2/rGO had band gap energies of 3.25, 2.95, and 2.86 eV, respectively. The highest photodegradation of RhB was obtained at the optimum condition in pH 2 with a photocatalyst mass of 20 mg and an irradiation time of 90 min. The photocatalytic activity of N-TiO2/rGO using visible light showed a higher percentage of photodegradation at 78.29%, compared to 44.08% under UV light. The kinetic study of the photodegradation of RhB using N-TiO2/rGO followed the pseudo-second-order model. [ABSTRACT FROM AUTHOR]

Meeting the escalating demand for clean water resources is one of the key challenges to ensure a sustainable future. Catalysis plays an important role to advance the chemical reactions required for wastewater efficient remediation. How to exploit high‐performance catalysts to boost the pivotal reaction kinetics always attracts researchers' enthusiasm. Perovskite oxides as a novel class of functional materials can be tuned to confer compositional flexibilities and provide rich and unique structural properties. As the rising‐star material, it has been widely probed for electrocatalysis, photocatalysis, and membrane‐catalysis for energy conversion, but received less attention in water treatment. In this review, the advances of perovskite oxides for advanced oxidation processes (AOPs) in water remediation are comprehensively elaborated. A fundamental understanding of the crystal structures and properties of perovskite oxides as well as the basic principles of AOPs is firstly provided. Then, emphasis is placed on how to tune the perovskite oxides to suit various AOPs. The strategies to design novel perovskite oxides to enhance the catalytic activities in AOPs have been highlighted. It is expected that after reading this review, readers will have a clearer vision of the background, the state of the art development, and general guidelines for future directions regarding research in this area. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) have been extensively employed for peroxymonosulfate-based advanced oxidation processes (PMS-AOPs), because of the maximum atomic efficiency offered by homogeneous-dispersed metal atoms and facile recyclability attained by the heterogeneous substrate. Intriguingly, though SACs with atomically isolated metal–nitrogen moieties have shown exceptional activities in PMS-AOP-based water treatment, their catalytic performances and mechanisms varied with the structures. In this review, the catalytic mechanisms of SACs/PMS systems were summarized. Specifically, nonradical reactive oxygen species are involved in the majority of the reactions, while singlet oxygenation, electron-transfer, and high-valent metal-oxo species are identified as dominant nonradical pathways. We also discussed the effects of metal center, metal loading, and substrate on the overall catalytic activities and mechanisms in PMS-AOPs. The pivotal roles of coordination environment in modulating the activity of SACs and reaction pathways were highlighted. Furthermore, an outlook on future challenges and prospective for SACs in water purification is presented. [Display omitted] [ABSTRACT FROM AUTHOR]

This review highlights the advances of sulfate radical (SO 4 •−)-based advanced oxidation processes (SR-AOPs) in water remediation using waste biomass-derived carbon materials as heterogeneous catalysts. After giving a brief overview of SR-AOPs and biomass-derived carbon materials, we showcase various formation pathways of SO 4 •− during peroxydisulfate (S 2 O 8 2−) or peroxymonosulfate (HSO 5 −) activation by various catalytic sites on carbons. The influences of water constituents or parameters and mechanism for SO 4 •− to react with organics are also summarized. We then outline challenges and future research directions to make waste biomass-derived carbon as a mainstream catalyst in SR-AOPs for industrial wastewater and water treatment. [ABSTRACT FROM AUTHOR]

Photocatalysis is a green technology and has received increasing attention owing to its potential in solving environmental problems in a sustainable manner. Among the candidates of semiconductor photocatalysts, graphitic carbon nitride (g-C 3 N 4) stands out for environmental purification because of its elemental abundances, structure robustness, and high performances. In this paper, we present a mini review of sustainable photocatalytic remediation of micropollutants over morphology-engineered g-C 3 N 4. The methods for advanced morphology control of g-C 3 N 4 are discussed and insights into morphology-dependent photocatalysis over g-C 3 N 4 are unveiled. The review also provides perspectives of challenges and solutions to sustainable water purification over the metal-free polymer materials. [Display omitted] • Photocatalytic remediation over morphology-engineered g-C 3 N 4 are reviewed. • The methods for advanced morphology control of g-C 3 N 4 are discussed. • The morphology-dependent photocatalysis over g-C 3 N 4 are unveiled. • Future challenges and solutions to sustainable water purification using polymer materials are provided. [ABSTRACT FROM AUTHOR]

Abstract: Natural zeolites are abundant and low cost resources, which are crystalline hydrated aluminosilicates with a framework structure containing pores occupied by water, alkali and alkaline earth cations. Due to their high cation-exchange ability as well as to the molecular sieve properties, natural zeolites have been widely used as adsorbents in separation and purification processes in the past decades. In this paper, we review the recent development of natural zeolites as adsorbents in water and wastewater treatment. The properties and modification of natural zeolite are discussed. Various natural zeolites around the world have shown varying ion-exchange capacity for cations such as ammonium and heavy metal ions. Some zeolites also show adsorption of anions and organics from aqueous solution. Modification of natural zeolites can be done in several methods such as acid treatment, ion exchange, and surfactant functionalisation, making the modified zeolites achieving higher adsorption capacity for organics and anions. [Copyright &y& Elsevier]

[Display omitted] Emerging environmental issues urge for energy-saving, clean and efficient water treatment technologies. Piezoelectric materials are promising to meet the needs via driving piezocatalysis-based advanced oxidation technologies (AOTs). Because of the non-centrosymmetric nature of piezoelectric materials, they demonstrate unique features by creating a built-in electric field via dipole polarization to generate polarized holes, electrons, and reactive oxygen species for water decontamination. This review covers the recent advances of piezoelectric nanomaterials and their applications in water remediation via piezocatalysis, piezo-photocatalysis, piezoelectric Fenton (piezo-Fenton), and piezocatalytic Fenton-like processes. We have discussed the features of piezoelectric nanomaterials, mechanisms of different piezocatalytic systems, stability of piezoelectric catalysts, and opportunities for new research directions. Perspectives on future design of novel nanostructured piezoelectric materials and promising combination with other catalytic systems for AOTs will also be provided. [ABSTRACT FROM AUTHOR]

[Display omitted] • Key features and challenges of polyaniline (PANI)-based adsorbents are summarized; • Mechanisms of adsorption/desorption on PANI-based adsorbents are discussed; • Roles of low-cost materials and 2D nanosheets in PANI-based adsorbents are highlighted; • We offer perspectives and future directions in developing PANI-based adsorbents. Access to clean water and sanitization is crucial to all life on Earth, and has been listed among the United Nations Sustainable Development Goals. Adsorption is a simple and economical technology for water purification. However, conventional adsorbents, such as zeolites, biochar, activated carbon and clay minerals, have some limitations, particularly their unsatisfactory adsorption efficiencies. Polyaniline (PANI), a stable conducting polymer with facile synthesis, nitrogen-rich functional groups, and tuneable morphology, is a promising candidate for adsorbing various pollutants. This review attempts to critically assess PANI-based adsorbents in terms of their advantages, disadvantages, and separation mechanisms in pollutant removal. Low-cost natural and waste materials, and emerging ultrathin 2D nanosheets can also be promising adsorbents. We highlight the significant roles of low-cost materials as well as emerging 2D nanosheets in enhancing the performance of PANI-based adsorbents. Combining PANI-based adsorbents and low-cost materials or 2D nanosheets can not only address the challenges of PANI-based adsorbents (e.g., low surface areas and thus low adsorption efficiencies), but also employ the synergistic effects of these adsorptive materials. As a result, the PANI-based hybrid adsorbents have enhanced functionality, and improved pollutant removal performance. Finally, we offer insightful perspectives and future research directions in developing PANI-based adsorbents with low-cost and 2D materials. [ABSTRACT FROM AUTHOR]

Photocatalysis has emerged as a prevailing and clean technology for water purification. In this work, we developed a facile approach for fabricating in-plane carbon/carbon nitride heterojunctions (CN-PDs) that induced 100 % photodegradation of naproxen under visible light irradiation in a nonradical manner. Experimental and simulation results collectively revealed that the incorporated carbon rings in carbon nitride (CN) significantly accelerate the charge dynamics of excitons, leading to a higher concentration of hot carriers. In addition, a lower intersystem crossing energy barrier was observed for the unique nanostructure compared to pristine CN, enabling an efficient energy-transfer-mediated oxygen activation to selectively generate singlet oxygen. An optimized composition of carbon rings (CN-PDs 0.1) enhanced the photodegradation of naproxen compared to CN. This study established the structure-activity relationships in selective photooxidation. The findings will benefit advanced design of high-performance nonmetal photocatalysts for organic wastewater treatment. [Display omitted] • Polymer dots was employed to implant carbon rings into carbon nitride matrix. • A 100 % nonradical pathway was evidenced in the photodegradation of naproxen. • Carbon rings in CN-PDs can expedite the dynamics of photo-excited charge carriers. • Intersystem crossing was facilitated in CN-PDs for more singlet oxygen generations. • The optimized nonradical pathway on CN-PDs 0.1 led to an efficient naproxen removal. [ABSTRACT FROM AUTHOR]

Herein, we delved into the dual charge modulation of built-in electric field (BIEF) within photocatalysts on degradation of bisphenol A (BPA) via a photocatalysis coupling peroxymonosulfate activation (PC-PMS) system. Thiophene rings were incorporated into the carbon nitride conjugated structure (CN-TDC-X) to tailor the BIEF for enhanced PC-PMS mediated wastewater purification. Advanced characterizations and theoretical calculations confirmed that CN units of the planar heterojunction acted as electron donors in the dark, activating PMS to generate reactive oxygen species of SO 4 •− and •OH, and facilitating electron transfer process (ETP) via non-radical pathways. While the motifs containing thiophene rings served as electron donors under light irradiation, initiating the production of h+, O 2 •−, 1O 2 , and activating the ETP pathway. The dual sites modulation by BIEF contributed to the efficient degradation of BPA in PC-PMS system. The work provides valuable insights into the manipulator in photo-Fenton-like process for sustainable and environmentally-friendly water purification. [Display omitted] • Incorporation of TDC into the C 3 N 4 conjugated structure to tailor BIEF. • Elucidation of the dual modulation mechanism of BIEF in the PC-PMS system. • Demonstration of C 3 N 4 units as electron donors in the dark for PMS activation. • Identification of CN-TDC-m as electron donor under light for PMS activation. • Achievement of high efficiency in pollutant removal and actual wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fundamentals of photocatalytic membrane reactors (PMRs) are elucidated in harnessing solar energy for water purification. • Photothermal effect is introduced in PMRs to augment the efficiency and longevity. • Recent advancements in PMRs for wastewater treatment are examined. • Challenges in PMRs for efficient and stable operations are discussed. Membrane separation and photocatalytic degradation are two important technologies for wastewater purification. However, practical applications are hindered by membrane fouling in membrane separation and the low efficiency of photocatalysis. A promising solution lies in the fusion of photocatalysis and membrane technology, capitalizing on their respective strengths and addressing their weaknesses. This comprehensive review endeavours to present a thorough examination of recent advancements in photocatalytic membrane materials and reactors for wastewater treatment. Key facets encompass the fundamentals of photodegradation, the contributions of different light bands to waste removal, various fabrication techniques for diverse types of photocatalytic membrane reactors, and the optimization of operational parameters. Notably, the innovative incorporation of the emerging photothermal effect into photocatalytic membrane technology has significantly augmented its efficiency and longevity in wastewater treatment. Furthermore, insightful commentary will be provided to assess the progress made in utilizing this cutting-edge technology for pollutant removal. Ultimately, the paper will conclude by summarizing key findings and addressing emerging challenges associated with the integration of these processes. The implementation of this advanced technology has the potential to revolutionize conventional wastewater treatment, offering a sustainable and environmentally friendly approach to large-scale wastewater purification. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS 2) has emerged as a versatile activator in persulfate-based advanced oxidation processes (PS-AOPs). As a polymorphic layered material, MoS 2 shows variable physicochemical properties including electrical, optical, catalytic and piezoelectric properties depending on the crystal structure. Accordingly, MoS 2 can serve as a cocatalyst/catalyst to directly activate persulfate and the activation efficiency can be further improved through converting external stimulus (e.g., light and mechanical force) into chemical/thermal energy. This review presents the recent advances of MoS 2 -based materials as effective catalysts in various PS-AOPs. We systematically compare the properties of three MoS 2 polytypes (1 T, 2 H and 3 R) and their applications in PS-AOPs. Meanwhile, modifications on MoS 2 and the persulfate activation processes with different functions of MoS 2 -based materials are discussed. Moreover, critical issues and research directions in MoS 2 future applications in PS-AOPs are addressed, with prospects towards implementation of self-powered water treatment systems with additional energy recovery. [Display omitted] • Properties of 1 T, 2 H and 3 R MoS 2 polytypes are systematically compared. • Various roles of MoS 2 -based materials playing in PS-AOPs are summarized. • Modifications on MoS 2 to improve persulfate activation efficiency are introduced. • Activation processes with different functions of MoS 2 -based materials are discussed. • Research directions in MoS 2 future applications in PS-AOPs are suggested. [ABSTRACT FROM AUTHOR]

Nanocarbon-catalyzed advanced oxidation processes for wastewater remediation are green and state-of-the-art methods, nevertheless, the origins of carbocatalysis remain unresolved. In this study, carbon nanotubes (CNTs) are employed as typical metal-free catalysts for catalytic peroxymonosulfate (PMS) activation and phenol oxidation. The surface chemistry and electronic properties of CNTs are deliberately tailored by liquid acid oxidation and subsequent thermal treatment. It is unveiled that the electron-rich carbon surface and carbonyl groups can affect organic adsorption capacity of the carbocatalysts and modulate persulfate activation in different catalytic manners. Furthermore, the relationship between the surface chemistry (oxygen functionality and electron density) and carbocatalysis is established, which is decisive to regulate the radical/nonradical pathways in the catalytic oxidation for water purification. This study provides new insights to carbon-catalyzed persulfate activation with manipulated reaction pathways and redox potentials. Image 1 [ABSTRACT FROM AUTHOR]

• Carbon quantum dots (4 mg/L) improved 10–40% removal of organic pollutants by 30 μM of Fe(VI). • The reaction kinetics in Fe(VI)/cqds system were 1.1–22.8 times than that in Fe(VI) system. • Fe(VI)/CQDs system showed excellent resilience in complex water matrices and improved the utilizing efficiency of Fe(VI). • CQDs reacted as the electron shuttle to mediate direct electron transfer process from organic pollutants to Fe(VI). Fe(VI) is a versatile agent for water purification, and various strategies have been developed to improve its pollutant removal efficiency. Herein, it was found that in addition to intermediate iron species [Fe(IV)/Fe(V)], direct electron transfer (DET) played a significant role in the abatement of organic pollutants in Fe(VI)/carbon quantum dots (CQDs) system. Around 86, 83, 73, 64, 52, 45 and 17% of BPA, DCF, SMX, 4-CP, phenol, p-HBA, and IBP (6 μM) could be oxidized by 30 μM of Fe(VI), whereas with the addition of CQDs (4 mg/L), the oxidation ratio of these pollutants increased to 98, 99, 80, 88, 87, 66 and 57%, respectively. The negative impact induced by solution pH and background constituents on Fe(VI) abatement of pollutants could be alleviated by CQDs, and CQDs acted as catalysts for mediating DET from organic pollutants to Fe(VI). Theoretical calculation revealed that iron species [Fe(VI)/Fe(V)/Fe(IV)] was responsible for the oxidation of 36% of phenol, while DET contributed to the oxidation of 64% of phenol in the Fe(VI)/CQDs system. Compared with iron species oxidation, the CQDs mediated DET from pollutants to Fe(VI) was more efficient for utilizing the oxidation capacity of Fe(VI). The DET mechanism presented in the study provides a prospective strategy for improving the pollution control potential of Fe(VI). [Display omitted] [ABSTRACT FROM AUTHOR]

Emerging contaminants can be removed effectively in heterogeneous Fenton-like systems. Currently, catalyst activity and contaminant removal mechanisms have been studied extensively in Fenton-like systems. However, a systematic summary was lacking. This review summarized: 1) The effects of various heterogeneous catalysts on emerging contaminants degradation by activating H 2 O 2 ; 2) The role of active sites in different catalysts during the activation of H 2 O 2 and their contribution to the generation of active species; 3) The modulation of degradation pathways of emerging contaminants. This paper will help scholars to advance the controlled construction of active sites in heterogeneous Fenton-like systems. Suitable heterogeneous Fenton catalysts can be selected in practical water treatment processes. [Display omitted] • The various catalysts on contaminants by activating H 2 O 2 are compared in detail. • The contribution of active sites to active species production is summarized. • The information of active species acting on emerging contaminants is discussed. • The possible research directions of active sites in H 2 O 2 -AOPs are proposed. [ABSTRACT FROM AUTHOR]

• The effect of dissolved organic matters (DOM) on organic degradation was explored. • Oxidation pathway of different DOM compounds was elucidated. • Evolution of DOM and inhibition mechanisms to pollutant degradation were revealed. • CHO-, CHON-, CHOS-, CHOP- and CHONP-based molecules showed moderate inhibition. Dissolved organic matters (DOM) are widely present in different water sources, causing significant effects on water treatment processes. Herein, the molecular transformation behavior of DOM during peroxymonosulfate (PMS) activation by biochar for organic degradation in a secondary effluent were comprehensively analyzed. Evolution of DOM was identified and inhibition mechanisms to organic degradation were elucidated. DOM underwent oxidative decarbonization (e.g., –C 2 H 2 O, −C 2 H 6 , –CH 2 and –CO 2), dehydrogenation (–2H) and dehydration reactions by ·OH and SO 4 ·−. N and S containing compounds witnessed deheteroatomisation (e.g., –NH, –NO 2 + H , –SO 2 , –SO 3 , –SH 2), hydration (+H 2 O) and N/S oxidation reactions. Among DOM, CHO-, CHON-, CHOS-, CHOP- and CHONP-containing molecules showed moderate inhibition while condensed aromatic compounds and aminosugars exhibited strong and moderate inhibition effects on contaminant degradation. The fundamental information could provide references for the rational regulation of ROS composition and DOM conversion process in a PMS system. This in turn offered theoretical guidance to minimize the interference of DOM conversion intermediates on PMS activation and degradation of target pollutants. [ABSTRACT FROM AUTHOR]

Chitosan (CS) extracted from lobster shells (Persian Gulf, Iran), was grafted with amino functionalized multiwalled carbon nanotube (MWCNT). This novel material was characterized by FE-SEM and FT-IR and used for the ultrasound-assisted removal of Pb 2+ ions and eriochrome cyanine R (ECR) dye. A central composite design (SCCD) under response surface methodology was used for studying the influences of important variables in removal process such as initial ECR and Pb 2+ ions concentrations, adsorbent mass and sonication time on the removal efficiency. Linear, 2FI, quadratic and cubic models were performed and a quadratic model was selected for analysis of each response. ANOVA for the quadratic model shows the F-value parameter (820.44 and 537.12 for ECR and Pb 2+ ions removal, respectively) and very low p -value (<0.0001), implying that the model was highly significant for understudy analytes adsorption. To achieve maximum removal, the optimum condition was determined and were set as:19.34 and 18.20 mg L −1 ,0.018 g and 9.35 min for initial ECR and Pb 2+ ion concentrations, adsorbent mass and sonication time, respectively. At these optimum conditions, 97.06% of ECR and 99.29% of Pb 2+ ions were removed in a short time. [ABSTRACT FROM AUTHOR]

In this study, graphitic carbon nitride was engineered to produce metal-free melem/g-C 3 N 4 hybrid photocatalysts through a hydrothermal technique. It was revealed that the hydrothermal treatment of g-C 3 N 4 could produce a hybrid structure of “thorn ball” liked melem on g-C 3 N 4 layer at a high temperature, and was able to modify the photoelectronic properties of g-C 3 N 4 . The spectroscopic measurements implied that a melem/g-C 3 N 4 hybrid has better light absorption and lower electron/hole recombination than pristine g-C 3 N 4 . Therefore, the melem/g-C 3 N 4 photocatalysts can decompose methylene blue solution under artificial sunlight with a higher rate and also present good stability. [ABSTRACT FROM AUTHOR]

• HPO 4 2− accelerated while H 2 PO 4 − inhibited PMS activation at > 50 mM. • H 2 PO 4 − inhibited the function of C O, pyridine N and defects for PMS activation. • HPO 4 2− promoted C O and graphitic N sites for PMS activation. • HPO 4 2− facilitated SO 4 - formation, but H 2 PO 4 − suppressed OH and SO 4 - release. • 1O 2 contribution first elevated, then dropped with rising phosphate concentration. The peroxymonosulfate (PMS) oxidation processes have received considerable attention for water treatment. The influence of monohydrogen phosphate and dihydrogen phosphate on PMS system is still controversial. A biochar activated PMS system was constructed to investigate the HPO 4 2−/H 2 PO 4 − effects on sulfamethoxazole degradation. Results showed that the presence of H 2 PO 4 − inhibited PMS activation, while the co-existing HPO 4 2− played a positive role. Therefore, it might be inaccurate to assess the activation capacity of a catalyst for PMS activation when using phosphate as a buffer solution. Importantly, H 2 PO 4 − inhibited the function of C O, pyridine N and defects for PMS activation. However, HPO 4 2− promoted C O and graphitic N sites for sulfamethoxazole (SMX) degradation. The contributions of OH and SO 4 − to SMX degradation decreased with the increase of H 2 PO 4 − concentration. The production of SO 4 − was accelerated with the increase of HPO 4 2− concentration, promoting pollutants degradation. The contribution of 1O 2 first increased and then decreased with the rise of HPO 4 2−/H 2 PO 4 − concentration. This study elucidated the roles of H 2 PO 4 − and HPO 4 2− in PMS system and revealed the corresponding specific influence mechanisms, promoting the application of PMS systems for antibiotic wastewater purification. [ABSTRACT FROM AUTHOR]

S-scheme photocatalytic systems driven by semiconductors are highly promising to degrade deleterious antibiotics in a sustainable manner. Here, ultrathin TiO 2 (B) nanosheets-decorated hierarchical In 2 S 3 spheres were fabricated for the photocatalytic degradation of tetracycline. The optimized IT-1.5:1 heterojunction attains stronger visible light-harvesting ability, superior electron-hole transfer efficiency, and abundant coupling heterointerfaces to generate reactive radicals, achieving an impressive removal efficiency of 97.3%, which is approximately 3.2 and 2.1-fold greater than TiO 2 (B) and In 2 S 3. Furthermore, the possible degradation pathways of tetracycline were proposed based on the calculated Fuki indexes and intermediates detected by a HPLC-MS. On In 2 S 3 /TiO 2 (B) interfaces, the migration of electrons from TiO 2 (B) to In 2 S 3 and an intensive built-in electronic field resulted in S-scheme mode, instead of type-II. The In 2 S 3 /TiO 2 (B) S-scheme structure offers an internal electron channel at the interface and maintains the active sites with high potentials for photocatalysis. This study provides protocols for rational design of S-scheme catalysts for sustainable water purification. [Display omitted] [ABSTRACT FROM AUTHOR]

Limestones and their modifications from Nordkalk Corporation (Finland) flotation fines (FF) and filter sand (FS) as potential adsorbents for AMD treatment and wastewater purification from Cu, Fe, Zn and Ni ions were studied. Limestones were capable of binding significant amounts of Cu and Fe from synthetic AMD solutions and wastewater, while unmodified limestones were not good for Zn and Ni removal. Two methods of surface area modification were suggested. The first one with 2 M solution of NaCl and the second one with wastewater from Norilsk Nickel Harjavalta. The structure of materials and their surface area were characterized by SEM, EDX, MIR spectroscopy and nitrogen adsorption methods. Optimal amount of adsorbents for different model and real solutions was found. Adsorption kinetics showed that the adsorption equilibrium was reached within approximately 8 h. The kinetic data fits to a pseudo second order model with correlation coefficients greater than 0.999. The adsorption capacity was the highest at solution pH range of 6–7. Langmuir, Toth and Sips models were used to fit the adsorption isotherms. Based on the parameters calculated from models, the adsorption capacity decreased in the order of Cu > Fe > Zn > Ni for FF and Fe > Cu > Zn > Ni for FS. The research showed that the proposed modified limestones can be successfully used for AMD neutralization and removal of Cu(II), Fe(III), Zn(II) and Ni(II). [ABSTRACT FROM AUTHOR]

• A novel EP-SPE system by coupling EP process with SPE was designed to purify plasticizers in water. • EP-SPE does not require additional supporting electrolytes, while the electrolysis energy consumption was reduced by 26.6 times. • EPR detection and kinetic model were used to reveal mechanisms of EP-SPE. • Four varieties of natural waters were chose to investigate universal applicability of EP-SPE. Electro-peroxone (EP) reaction has been considered as a promising process for real effluent treatments. However, the use of the technology in natural water conditions is limited by low electrical conductivity and high operating costs. Herein, a novel electrochemical system was designed to overcome this constrain by coupling EP with a solid polymer electrolyte (EP-SPE). Performances of EP-SPE system were thoroughly evaluated by comparing the decomposition and energy efficiencies of various plasticizers in different systems. The EP-SPE system achieved 50% of pollutants mineralization in only 10 min with the electrolysis energy consumption of 1.0 kWh · m − 3 , While the conventional EP system (not) adding salt compounds (CEP-(N) AS) need 30 (60) min to reach 50% of pollutants mineralization with 3.8 (26.6) kWh · m − 3 . Kinetics and mechanisms of EP-SPE were investigated in detail, while electronic paramagnetic resonance (EPR) detection and kinetic model revealed the occurrence, transient concentration and degradation contribution of reactive oxidizing species (ROS). Furthermore, tests of variety of SPEs and natural waters demonstrated universal applicability of EP-SPE. Additionally, EP-SPE did not show any performance deterioration after 15 runs. Therefore, this work provides a feasible technology for plasticizer purification in natural water. [Display omitted] [ABSTRACT FROM AUTHOR]

Conversion of digestate into biochar-based catalysts is an effective strategy for disposal and resource utilization. The active sites on biochar correlated with reactive species formation in peroxymonosulfate (PMS) system directly. Clarifying the structure-performance relationship of digestate derived biochar in PMS system was essential for decomposition of contaminants. Herein, dairy manure digestate derived biochar (DMDB) was prepared for PMS activation and sulfamethoxazole (SMX) degradation. The higher pyrolysis temperature could promote effective sites generation. Especially, the DMDB-800 catalyst exhibited excellent performance for PMS activation, achieving 90.2% degradation of SMX within 60 min. Based on the correlation analysis between log (k) values and active sites, defects, graphite N and C O were identified as dominant sites for PMS activation. The 1O 2 oxidation and surface electron transfer were critical routes for SMX degradation. Besides, the degradation pathways of SMX were proposed according to DFT calculations and intermediates determination. The cleavage of the sulfonamide bond, hydroxylation of the benzene ring and oxidation of the amino group mainly occurred during SMX degradation. Overall, this study provides deep insights into the enhanced mechanism of tunable active sites on DMDBs for PMS activation, boosting the application of digestate biochar for water treatment in advanced oxidation systems. [Display omitted] • Dairy manure digestate derived biochar (DMDB) was prepared with tunable structure. • The enhanced SMX removal was ascribed to 1O 2 oxidation and electron transfer. • Structure-performance relationship of DMDBs in PMS system was revealed. • Graphitic N and defects were key active sites on DMDBs for PMS activation. • The SMX degradation pathways were proposed theoretically and experimentally. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrolysis of ZIF-8 containing Fe2+ and Cu2+ has produced Fe-Cu@N-C. • Fe-Cu@N-C has superior activity for organic pollutant removal and CrVI reduction. • Singlet oxygen was verified as the dominant active species for organic oxidation. • Surface-adsorbed atomic hydrogen was responsible for effective reduction of CrVI. • Bimetallic active sites and porous carbon structure promoted catalytic activity. Exploring highly stable and efficient non-precious metal catalysts for decontamination of various non-biodegradable contaminants is a major challenge. Herein, Fe, Cu-coordinated ZIF-derived bimetal encapsulated N-doped carbon nanotubes (Fe-Cu@N-C) were developed and employed as novel bifunctional catalysts for organic oxidation and CrVI reduction. Pyrolysis of ZIF-8 containing Fe2+ and Cu2+ has successfully produced Cu nanoparticles and atom-dispersed Fe bimetals embedded in N-doped carbon nanotube catalysts. It was observed that the obtained optimal Fe-Cu@N-C possessed outstanding activity and stability for efficient degradation of organic contaminants via PMS activation, and toxic CrⅥ reduction with Formic acid (FA) as the reductant. Singlet oxygen (1O 2 ·) was verified as the dominant active species for organic oxidation, while surface-adsorbed atomic hydrogen (H*) was responsible for effective reduction of CrVI to CrIII in the Fe-Cu@N-C/FA system. Compared with other ZIF derived systems such as Fe@N-C, Cu@N-C, and metal-free N-C, Fe-Cu@N-C exhibited prominent catalytic activities, which were attributed to bimetallic active sites (Fe-N x and Cu-N x), high N-doped level, large surface area and conductivity of porous carbon structure for fast mass and electron transport. This report provides a new approach to design highly efficient multifunctional catalysts for the purification of water to remove various types of pollutants. [ABSTRACT FROM AUTHOR]

• Degradation pathways of typical PPCP pollutants in ECWAO over MnO@C/GF are studied. • Removal kinetics and mineralization efficiencies of PPCPs are compared. • Theoretical calculation is performed assuming nucleophilic attack in ECWAO reaction. • Structure activities of aromatic, fused-ring and sulfonamide PPCPs are compared. • Mineralization efficiency of PPCP is correlated with its chemical structure. The world-wide accumulation of pharmaceuticals and personal care products (PPCPs) in water environment emphasizes the urgent development of effective PPCPs removal technologies. In this work, the feasibility of electrocatalytic wet air oxidation (ECWAO) technology for the treatment of six typical PPCP pollutants was evaluated, and their degradation pathways were studied. The ECWAO reaction of PPCPs was found to fit to the first-order kinetics, with apparent rate constants in an order of triclosan (0.206 min−1) > bisphenol A (0.104 min−1) > tetracycline (0.062 min−1) > ciprofloxacin (0.041 min−1) > ibuprofen (0.035 min−1) > sulfamethoxazole (0.026 min−1). The PPCP compounds with aromatic ring and oxygenated groups were mineralized at relatively higher efficiencies than the fused-ring or sulfonamide compounds. The degradation pathways of the PPCPs were proposed based on the detected intermediates and with the aid of quantum chemical calculation. Toxicity and biodegradability analyses demonstrated the ECWAO reaction was able to diminish the toxicity of PPCPs and improve their biodegradability. The specific energy consumption (SEC) of the ECWAO system varied from 11.7 to 19.53 kW h kg-TOC-1 in treating the different PPCP S. Such values were at least one order of magnitude lower than the SECs of conventional electro-oxidation systems. Practice on real lake water treatment showed promising potential of the ECWAO technology for cost-effective and safe elimination of PPCPs pollution. [ABSTRACT FROM AUTHOR]

In this work, low-cost carbon-based materials were developed via a facile one-pot pyrolysis of oily sludge (OS) and used as catalysts to activate peroxymonosulfate (PMS) for removing aqueous recalcitrant pollutants. By adjusting the pyrolysis temperature, the optimized OS-derived carbocatalyst manifested good performance for PMS activation to abate diverse organic pollutants in water treatment. Particularly, an average removal rate of 0.87 mol phenol per mol PMS per hour at a catalyst dosage of 0.2 g L−1 is attained by the OS-derived carbocatalyst, higher than many other documented catalysts. A series of experimental evidences consolidated that organic pollutants were oxidized mainly via electron-transfer mechanism albeit the detection of singlet oxygen (1O 2) from PMS activation driven by the OS-derived carbocatalyst. Specifically, the proportion of carbonyl groups (C˭O) in the carbocatalyst adopted with selective modification treatments to tailor the surface chemistry was found to be linearly correlated with the catalytic activity and theoretical calculations demonstrated that the reactions between C˭O and PMS to form surface reactive complexes were more energetically favorable compared to 1O 2 generation. Herein, this study not only offers a new strategy for reusing OS as value-added persulfate activators but also deepens the fundamental understanding on the nonradical regime. [Display omitted] • Low-cost carbocatalyst was prepared by one-pot pyrolysis of oily sludge (OS). • OS-derived carbocatalyst was highly efficient to activate peroxymonosulfate. • Carbonyl groups play a key role in electron-transfer nonradical mechanism. • A value-added and reuse approach of OS in water remediation was offered. [ABSTRACT FROM AUTHOR]

Catalytic membranes can simultaneously realize physical separation and chemical oxidation in one integrated system, which is the frontier technology for effective removal of organic containments in wastewater treatment. The catalytic membrane coupled with advanced oxidation processes (AOPs) not only significantly enhances the pollutant removal efficiency but also inhibits the fouling of the membrane via self-cleaning. In this review, the preparation approaches of catalytic membranes including blending, surface coating, and bottom-up synthesis are comprehensively summarized. The different integrated catalytic membrane systems coupled with photocatalysis, Fenton oxidation, persulfate activations, ozonation and electrocatalytic oxidation are discussed in terms of mechanisms and performance. Besides, the principles, influencing factors, advantages and issues of the different catalytic membrane/oxidation systems are outlined comparatively. Finally, the future challenges, and research directions are suggested, which is conducive to the design and development of catalytic membrane-oxidation systems for practical remediation of organic containing wastewater. [Display omitted] • The preparation approaches of catalytic membranes are summarized. • The catalytic membranes coupled with advanced oxidation systems are classified. • The principles and advantages of catalytic membrane/oxidation systems are outlined. • The future challenges of catalytic membrane-based water treatment are proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metal-free C 3 N 5 showed enhanced visible-light-driven PMS/PDS activation. • Efficient pollutant degradation and water disinfection was achieved. • Narrower bandgap, richer defects, and higher N ratio make higher PMS/PDS activation. Although Fenton-like processes have been widely applied to treat emerging micropollutants (EMs) in wastewater, conventional activators used to activate peroxymonosulfate (PMS) or peroxydisulfate (PDS) still suffer from the problems of metal leaching and limited catalytic stability for practical applications. Herein, metal-free C 3 N 5 was synthesized and employed as an activator for PMS activation. With the aid of visible light, C 3 N 5 exhibited an excellent PMS activation capacity for EMs degradation, even better than popular C 3 N 4. This is because C 3 N 5 can harvest more visible light, prolong the lifetime of photogenerated carriers, and enhance PMS adsorption by more N active sites. Additionally, efficient EMs degradation and water disinfection were also achieved by visible light driving C 3 N 5 activated PDS. This work demonstrates a new metal-free material for environmental-friendly advanced oxidation processes for the efficient water purification. [ABSTRACT FROM AUTHOR]

• Co 2 AlO 4 /CoAl 2 O 4 @Al 2 O 3 monoliths (CAMs) were derived from ZIF-67@γ-Al 2 O 3 pellets. • The surface chemistry of CAMs affected their catalytic activities in PMS activation. • The activities of CAMs linearly correlated with Co3+/Co2+ and O Defect /O Lattice ratios. • Co3+-rich CAMs showed robust catalytic activity, stability and reusability. • OH was the decisive oxidant in CAMs/PMS system for metronidazole removal. Immobilizing metal-organic frameworks in macro-supports to form three-dimensional catalysts holds a great promise in environmental remediation, however quantitative structure/property-catalytic activity relationship remains unknown currently. In this work, we constructed Co 2 AlO 4 /CoAl 2 O 4 @Al 2 O 3 monoliths derived from ZIF-67@γ-Al 2 O 3 pellets and systematically investigated their surface chemistry-activity relationships in peroxymonosulfate (PMS) activation for organic degradation. The activities of Co 2 AlO 4 /CoAl 2 O 4 @Al 2 O 3 catalysts were selectively correlated with their ratios of Co3+/Co2+ and O Defect /O Lattice. The optimized Co 2 AlO 4 /CoAl 2 O 4 @Al 2 O 3 demonstrated an excellent catalytic efficacy toward PMS activation for metronidazole removal in a wide pH range (3.29–10.26) and OH was the dominant oxidant for metronidazole oxidation. The catalyst also exhibited desirable performance for eliminating other emerging contaminants and enduring catalytic activity and stability in PMS activation without regeneration. This study provides new prospects in rational design of robust, cost-effective and self-cleaning/repairing three-dimensional Co-based macroscale-catalysts with an outstanding and lasting catalytic activity for water purification. [ABSTRACT FROM AUTHOR]

• Sludge components and dewatering methods impact the properties of biochar. • Thermochemical methods influence the characteristics of sludge biochar. • The mechanisms and removal performance of pollutants by biochar are introduced. • High-temperature carbonized sludge biochar exhibits excellent performance. • This review offers a sustainablewayof sludge reutilizationfor water purification. Environment-friendly and cost-effective disposal and reutilization of sludge wastes are essential in wastewater treatment processes (WWTPs). Converting activated sludge into biochar via thermochemical treatment is a promising technology for waste management in WWTPs. This review summarizes the compositions of sludge, the dewatering methods, and the thermochemical methods whichinfluence the structures, chemistry, and catalytic performances of the derived biochar. Moreover, the physiochemical characteristics and chemical stability of sludge biochar are discussed. Catalytic applications of biochar are highlighted, including the reaction mechanisms and feasibility for catalytic removal of organic contaminants. High-temperature carbonized sludge biochar exhibits excellent performance for persulfate activation in advanced oxidation processes due to the graphitic carbon structure, newly-created active sites, and fine-tuned metal species. Therefore, the sludge biochar can be produced via cost-effective and eco-friendly approaches to immobilize harmful components from sludge and remediate organic pollution in wastewater, offering a sustainable route toward sludge reutilization into value-added products for water purification. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Boron could activate peroxymonosulfate (PMS) for plasticizer degradation. • Nonradical N dopedcarbon nanotube/PMS system was unable to eliminate phthalates. • •OH yield was about 2.5 times higher than that of SO 4 − in kinetics. • The activity of boron largely depended on solution pH in PMS activation. • The boron/PMS system was effective for plasticizer degradation in real water matrix. Plasticizer pollution in drinking water and aquatic systems has raised global concerns due to the lasting and chronic hazards to marine life and public health. Metal-free materials are promising as green catalysts for wastewater purification. In this study, amorphous boron was applied as a metal-free activator to decompose peroxymonosulfate (PMS) for the degradation of plasticizers in water. Integrating radical trapping and selectively quenching tests with kinetic evaluation and electrochemical analysis, hydroxyl radical was found to be the dominating reactive oxygen species (ROS). With a strong oxidative capacity, the boron/PMS system can effectively degrade both bisphenols and phthalates plasticizers. In contrast, a carbon nanotube-catalyzed PMS system mediated a nonradical pathway to oxidize the electron-rich plasticizer (bisphenol A), but ineffectively to decompose the highly recalcitrant phthalates plasticizers (diethyl phthalate). Moreover, we unveiled that the boron surface was oxidized to boron oxide during the redox reaction, and the oxide would be self-cleaned in the acidic solution to regenerate fresh boron and restore the activity during the cyclic operations. Therefore, this work not only gains new insights into the radical and nonradical oxidations by metal-free catalysis, but also provides feasible technologies for plasticizer purification in water. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• N-doping of biochar induced a variation of persistent free radicals (PFRs). • Different types of PFRs were found on hydrochar and N-doped hydrochar (NHC). • NHC was a robust catalyst for degradation of endocrine disrupting compounds. • Graphitic N played a role in both radical and nonradical pathways for the degradation. Metal-free carbocatalysts are raising increased interest in advanced oxidation processes (AOPs) for green degradation of aqueous organic pollutants. In the present study, a series of N-doped hydrochars (NHCs) was prepared from pinewood biomass and used in carbocatalysis toward catalytic peroxymonosulfate (PMS) activation to degrade refractory endocrine disrupting compounds. Nitrogen-doping was found to regulate the concentrations and types of persistent free radicals (PFRs) on hydrochar, promoting the electron transfer and oxidative degradation of the contaminants. Mechanistic studies revealed that graphitic N not only shows a strong electron transfer to facilitate PMS activation in a nonradical pathway, but also induces the formation of oxygen-centered PFRs from the structure defects for a radical oxidation pathway. More importantly, the PMS/NHC system demonstrates efficient degradation and satisfactory stability for real water treatment. This study has gained in-depth understanding on the roles of N-dopants in radical and nonradical pathways of biomass-based carbocatalysis, and will provide a promising and environmental-friendly route for efficient degradation of refractory endocrine disrupting compounds for green remediation. [ABSTRACT FROM AUTHOR]

• Shape-controlled LBCM perovskites were prepared for peroxymonosulfate activation. • Cubic LBC 0.8 M 0.2 obtained higher activity than octahedral LBC 0.2 M 0.8. • Oxygen vacancies acted at the dominant active sites. • SO 4 •− was the primary ROS among •OH, SO 4 •−, and 1O 2 for mineralization. • Synergistic effect was observed for organics destruction when coupled with ozone. The soaring pressure on clean environment urges for high-performance and robust catalysts in water treatment to secure the sustainability of water resources. In this work, shape-controlled perovskites La 0.5 Ba 0.5 Co x Mn 1-x O 3-δ (LBC x M 1-x) were applied as peroxymonosulfate (PMS) activators to generate reactive oxygen species (ROS) for water purification. Owing to the presence of abundant oxygen vacancies and low-valence Co2+ cations, cubic-shaped LBC 0.8 M 0.2 exhibited a much higher catalytic activity than octahedral LBC 0.2 M 0.8 with a better structural stability and controlled metal leaching. Iodometric titration and solid electron paramagnetic resonance (EPR) validated that an increase of Co/Mn ratios would produce abundant oxygen vacancies as active sites to bond with and activate PMS molecules, facilitated by the redox couples of Co2+/Co3+ and Mn3+/Mn4+. Competitive radical tests and in-situ EPR spectra suggested that SO 4 •− was the dominant ROS. This study provides new insights into the structure-performance relationship of shape- and defect-dependent perovskites in environmental catalysis. [ABSTRACT FROM AUTHOR]