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[Display omitted] • A novel catalytic behavior was revealed in defective nanozymes. • Defects and self-supplied vacancies greatly boosted the generation of reactive oxygen species. • The catalytic behavior was confirmed for the degradation of tetracycline. • Defective nanozymes exhibited an ultrafast degradation rate (26.0 min−1 g−1 L). • Breaking the limitation of pH and expanding its scope of action (pH>5.0). Although nanozymes have shown significant potential in wastewater treatment, enhancing their degradation performance remains challenging. Herein, a novel catalytic behavior was revealed for defective nanozymes with catalase-mimicking characteristics that efficiently degraded tetracycline (TC) in wastewater. Hydroxyl groups adsorbed on defect sites facilitated the in-situ formation of vacancies during catalysis, thereby replenishing active sites. Additionally, electron transfer considerably enhanced the catalytic reaction. Consequently, numerous reactive oxygen species (ROS) were generated through these processes and subsequent radical reactions. The defective nanozymes, with their unique catalytic behavior, proved effective for the catalytic degradation of TC. Experimental results demonstrate that •OH, •O 2 −, 1O 2 and e− were the primary contributors to the degradation process. In real wastewater samples, the normalized degradation rate constant for defective nanozymes reached 26.0 min−1 g−1 L, exceeding those of other catalysts. This study reveals the new catalytic behavior of defective nanozymes and provides an effective advanced oxidation process for the degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

• An updated review on ROS implicated in AOPs for pharmaceutical waste is presented. • Potential ROS are implicated in the pharmaceutical waste degradation. • Mechanistic insights regarding ROS-mediated reaction pathways are discussed. • The main detected transformation products of ACT using specific ROS are reported. Innately designed to induce physiological changes, pharmaceuticals are foreknowingly hazardous to the ecosystem. Advanced oxidation processes (AOPs) are recognized as a set of contemporary and highly efficient methods being used as a contrivance for the removal of pharmaceutical residues. Since reactive oxygen species (ROS) are formed in these processes to interact and contribute directly toward the oxidation of target contaminant(s), a profound insight regarding the mechanisms of ROS leading to the degradation of pharmaceuticals is fundamentally significant. The conceptualization of some specific reaction mechanisms allows the design of an effective and safe degradation process that can empirically reduce the environmental impact of the micropollutants. This review mainly deliberates the mechanistic reaction pathways for ROS-mediated degradation of pharmaceuticals often leading to complete mineralization, with a focus on acetaminophen as a drug waste model. [ABSTRACT FROM AUTHOR]

• The mechanisms involved in the Fenton process were comprehensively elaborated. • The factors determining the influence of pH were emphatically illustrated. • We differentiate several Fenton-like process through their promoting mechanisms. • Substantive proposals toward future were proposed in this review. Fenton and Fenton-like processes, which could produce highly reactive species to degrade organic contaminants, have been widely used in the field of wastewater treatment. Therein, the chemistry of Fenton process including the nature of active oxidants, the complicated reactions involved, and the behind reason for its strongly pH-dependent performance, is the basis for the application of Fenton and Fenton-like processes in wastewater treatment. Nevertheless, the conflicting views still exist about the mechanism of the Fenton process. For instance, reaching a unanimous consensus on the nature of active oxidants (hydroxyl radical or tetravalent iron) in this process remains challenging. This review comprehensively examined the mechanism of the Fenton process including the debate on the nature of active oxidants, reactions involved in the Fenton process, and the behind reason for the pH-dependent degradation of contaminants in the Fenton process. Then, we summarized several strategies that promote the Fe(II)/Fe(III) cycle, reduce the competitive consumption of active oxidants by side reactions, and replace the Fenton reagent, thus improving the performance of the Fenton process. Furthermore, advances for the future were proposed including the demand for the high-accuracy identification of active oxidants and taking advantages of the characteristic of target contaminants during the degradation of contaminants by the Fenton process. [ABSTRACT FROM AUTHOR]

S and Co co-doped carbon catalysts were prepared via pyrolysis of MOF-71 and thiourea mixtures at 800°C at a mass ratio of MOF-71 to thiourea of 1:0.1 to effectively activate peroxymonosulfate (PMS) for methylene blue (MB) degradation. The effects of two different mixing routes were identified on the MB degradation performance. Particularly, the catalyst obtained by the alcohol solvent evaporation (MOF-AEP) mixing route could degrade 95.60% MB (50 mg/L) within 4 min (degradation rate: K = 0.78 min−1), which was faster than that derived from the direct grinding method (MOF-DGP, 80.97%, K = 0.39 min−1). X-ray photoelectron spectroscopy revealed that the Co–S content of MOF-AEP (43.39at%) was less than that of MOF-DGP (54.73at%), and the proportion of C–S–C in MOF-AEP (13.56at%) was higher than that of MOF-DGP (10.67at%). Density functional theory calculations revealed that the adsorption energy of Co for PMS was −2.94 eV when sulfur was doped as C–S–C on the carbon skeleton, which was higher than that when sulfur was doped next to cobalt in the form of Co–S bond (−2.86 eV). Thus, the C–S–C sites might provide more contributions to activate PMS compared with Co–S. Furthermore, the degradation parameters, including pH and MOF-AEP dosage, were investigated. Finally, radical quenching experiments and electron paramagnetic resonance (EPR) measurements revealed that 1O2 might be the primary catalytic species, whereas ·O2− might be the secondary one in degrading MB. [ABSTRACT FROM AUTHOR]

Hospital wastewater contains microorganisms, heavy metals, toxic chemicals, and different drugs that might be treated insufficiently or not at all before they enter municipal wastewater, causing numerous problems for humans and other living organisms. The aim of this study was to assess the performance of the UV/H2O2/S2O82- process in the treatment of hospital wastewater. This process has been modelled and optimised using the statistical response-surface method (RSM), and the regression analysis showed that the data were well-fitted with a second-order polynomial equation. Based on the model, the biochemical oxygen demand (BOD) removal efficiency can reach 93.2% in optimal conditions of pH = 3.1, H2O2 dosage of 203.1 mg/L, and NaPS dosage of 44.7 mg/L. The results showed that in the presence of both persulphate and hydrogen peroxide, the process efficiency was higher in acidic conditions and in the range of the design experiment, more oxidants had more efficiency. Turbidity, total Kjeldahl nitrogen (TKN), total organic carbon (TOC), total coliform, and E. coli were also studied as supplementary parameters, and removal efficiencies of about 78.53%, 70%, 52%, 99%, and 99.8% were achieved, respectively. Kinetic studies revealed that the data were well-fitted with the second-order kinetic model and had a regression coefficient of 0.97 and a rate constant of 0.0018 (L/mg min). [ABSTRACT FROM AUTHOR]

A novel catalyst was synthesised in a way that it could be applied in simultaneous adsorption and heterogeneous Fenton processes. The granulated Fe3O4/CuBDC/Cellulose nanocomposites were synthesised with a novel in-situ granulation method in a rotary autoclave reactor, and they were efficient in the removal of a detrimental trisazo dye, direct blue 71 (DB71). The catalysts were characterised by various analyses. In order to fulfill the expectation from the catalysts traits, many parameters were evaluated meticulously such as the effect of modification of Fe3O4 nanoparticles, the ratio of Fe3O4 to CuBDC in the nanocomposite, the stability of the catalyst, and diverse catalyst characterisations (SEM, EDX, FTIR, XRD, BET, XPS). The rotating speed of the autoclave was optimised by carrying out computational fluid dynamics (CFD) simulations; 60 rpm rotating speed was selected among the other ones to achieve catalysts that were more homogeneous. Moreover, the dye elimination process was conducted in a pilot fluidised bed reactor. The impacts of three diverse parameters on the removal efficiency were assessed by response surface method (RSM) to optimise them, 96.85% dye removal was achieved in a 30-min process (the initial DB71 concentration = 10 mg/L, the H2O2 concentration = 8.55 mM, and the catalyst dosage = 7.12 g/L). The study of the dye elimination mechanism and thermodynamics of the process indicated endothermic, spontaneous, favourable, and physical adsorption of DB71 on the catalysts. Reutilisation of granulated catalysts at least for ten treatment cycles without regeneration process incorporating high and stable degradation efficiency (11% performance reduction), exhibited the exceeding performance of the highly durable well-designed catalysts in the simultaneous adsorption and heterogeneous Fenton processes. [ABSTRACT FROM AUTHOR]

Ozonation (O3) is a widely used advanced oxidation process (AOP) for the treatment of wastewater, while its drawbacks include high energy consumption and poor solubility must be reduced or eliminated. Hence, a combined catalytic ozonation process with H2O2 and S2O82- was employed to degrade mono ethylene glycol (MEG) and eliminate ecological risks during the treatment of gas refinery wastewater. In this study, the reduction of chemical oxygen demand (COD) and MEG from wastewater by O3, O3/H2O2, O3/Na2 S2O8, O3/GAC, O3/GAC/S2O82- and O3/GAC/H2O2 oxidation treatment systems were investigated. The optimal treatment conditions were obtained as O3 dosage of 0.81 g h−1, H2O2 (0.15 mol L−1), S2O82- (2 g L−1), GAC (7 g L−1), pH of 11 and 60 min reaction time. The results revealed that the highest rate of degradation of MEG, COD reduction and the minimum electrical energy per order from the wastewater were 87.6%, 78.1% and 1.01 kWh/m3 respectively for O3/GAC/S2O82- process and 91.0%, 82.5% and 0.877 kWh/m3 respectively for O3/GAC/H2O2 process. The MEG degradation rate constant by O3/GAC/H2O2 system about 6.2 times and O3/GAC/S2O82- system over 5.3 times were higher than O3. After calculation, the synergy factors in O3/GAC with H2O2/S2O82- systems are more than 4.7, demonstrating that both systems have a strong synergistic effect. The finding related to the OH° trapping agent illustrates that indirect oxidation by OH° plays a vital role in the degradation of MEG. The performance of GAC stability was checked and resulted in the GAC also showing good stable catalytic activity in five consecutive cycles of use. The degradation pathways of MEG in the O3/GAC with H2O2 or S2O82- system were proposed based on intermediate analysis. The main intermediates found in MEG oxidation include glycolaldehyde, glycolic acid, glyoxal, glyoxylic acid, oxalic acid and formic acid. Finally, modification of wastewater treatment suggested that the burping phenomenon and the glycol foaming tendency were not observed. [ABSTRACT FROM AUTHOR]

In this study, novel dual wave-absorbing ZnFe 2 O 4 /CNTs nanoparticles were successfully fabricated using a microwave hydrothermal method and applied for enhanced microwave-induced catalytic degradation of bisphenol A (BPA) in aqueous solution. The effects of various process parameters, including Fe3+ concentration (mass ratio of ZnFe 2 O 4 to CNTs), MW irradiation time, MW power, initial BPA concentration, and catalyst dose on the degradation process were thoroughly assessed. The results indicate that ZnFe 2 O 4 /CNTs nanoparticles effectively utilize MW energy to generate more hot spots and exhibit superior MW catalytic activity at a 1.0:10.0 mass ratio (ZnFe 2 O 4 :CNTs), due to the synergistic effect between ZnFe 2 O 4 nanoparticles and CNTs under MW irradiation. Additionally, hydroxyl radicals (·OH) play a major role in the degradation process, while superoxide radicals (·O 2 −) and holes (h+) play relatively minor roles. Potential intermediates and degradation pathways in the ZnFe 2 O 4 /CNTs/MW system have also been identified. Thus, the integrated ZnFe 2 O 4 /CNTs/MW technology shows great promise for treating environmental endocrine disruptors (EEDs) in water and wastewater. [ABSTRACT FROM AUTHOR]

Heterogeneous cobalt-based catalysts have recently gained attention as persulfate activators to degrade dyes and organic pollutants in sulfate radical-based advanced oxidation processes (SR-AOPs). This study fabricated magnetic cobalt nanoparticles embedded in a carbonaceous hydrogel (Co@C) using high-temperature pyrolysis of the Co2+-embedded chitosan-graft-poly(acrylic acid) (Co2+-embedded CTS-g-PAA) hydrogel. Subsequently, the prepared Co@C was evaluated as a peroxymonosulfate (PMS) activator for degrading azo dyes. The catalyst showed the highest performance toward reactive red 141 (RR141) than Congo red, methyl orange, direct yellow 50, and reactive black 5. RR141 was completely degraded within 10 min, with a 3.20 min–1 pseudo-first-order rate constant. The degradation rate increased with higher catalyst dosage, PMS dosage, and temperature. The pH of the solution had a minimal effect on the degradation of RR141, indicating that the catalyst could be effective across a wide pH range. Moreover, the quenching experiment and the electron paramagnetic resonance analysis indicated that the catalytic system generated SO4•−, HO•, O2•−, and 1O2. The RR141 degradation was slightly affected by Cl−, NO3−, and SO42−. The catalyst demonstrated high efficiencies in real water samples. The catalyst could be easily recovered using a magnet and reused for ten cycles with only a 10% degradation efficiency loss. Furthermore, the catalyst could effectively degrade other organic pollutants, including tetracycline and 4-nitrophenol. This study demonstrates that the Co@C catalyst can effectively purify wastewater via SR-AOPs. [ABSTRACT FROM AUTHOR]