Sulfate Radical-based Advanced Oxidation Processes Research Articles

High-efficiency PMS activation by difunctional Co-Fe PBA/g-C3N4 S-scheme heterojunction for oxytetracycline degradation: Performance evaluation and mechanism insight

The utilization of sulfate radical-based advanced oxidation processes (SR-AOPs) has captivated the academic community due to their minimal energy requirements and superior efficacy in peroxomonosulfate (PMS) activation for pollutant decomposition. Notwithstanding these advantages, engineering an effective and economical catalyst for PMS activation presents a considerable hurdle. In the present study, a metal-organic framework of CoFe PBA is ingeniously anchored onto g-C3N4 nanosheets, resulting in the formation of an innovative CoFe PBA/g-C3N4 S-scheme heterojunction that demonstrates remarkable efficiency in PMS activation. Intriguingly, the catalytic efficiency of CoFe PBA/g-C3N4 surpasses that of g-C3N4 and CoFe PBA by 7-fold and 2.33-fold, respectively. The heightened activity of CoFe PBA/g-C3N4 heterojunction is attributed to the enhanced charge transfer efficiency, a consequence of the successful heterojunction formation. Concurrently, the ability of photoexcited electrons to reduce Co3+/Fe3+ to Co2+/Fe2+ bolsters PMS activation. Significantly, this heterojunction retains unparalleled stability in degrading oxytetracycline without discernible performance attenuation, heralding its commendable prospects in real-world applications. Besides, mechanism exploration indicates that SO4−, h+, and electron transfer contribute to oxytetracycline degradation in the CoFe PBA/g-C3N4 system. This investigation serves as a beacon for the strategic development of highly active and stable catalysts for PMS activation, aiming at environmental decontamination.

Insights into the removal of sulfamethazine and sulfonamide-resistant bacteria from wastewater by Fe-Mn spinel oxide modified cow manure biochar activated peroxymonosulfate: A nonradical pathway regulated by enhanced adsorption and 3d orbital electron reconstruction

Effectively regulating nonradical pathways is crucial for adapting to complex water environments in sulfate radical-based advanced oxidation processes (SR-AOPs). This study prepared manganese ferrite-modified cow-manure biochar composites (BC-FM) as peroxymonosulfate activators to remove sulfamethazine (SMT) and sulfonamide-resistant bacteria (SA-ARB) from wastewater. The extensive conjugated graphitic structure in biochar induced Fe 3d orbital electron reconstruction, promoting empty orbitals formation and enhancing peroxymonosulfate inner-sphere complexation. This facilitated 100 % electron-transfer-dominated nonradical regulation. BC-FM exhibited remarkable catalytic performance, with apparent rate constant of 0.170 min−1 for SMT, inactivating ∼8.6 log of SA-ARB, and effectively blocking horizontal transfer of antibiotic resistance genes in both single and complex pollution systems (SMT/SA-ARB). Moreover, ion leaching experiments, cycling tests, real-water experiments, fluidized-bed and fixed-bed experiments demonstrated BC-FM’s potential for prolonged utilization and practical implementation. This study offers new insights into designing high-performance, environment-friendly bimetal catalysts and provides a basis for remediating organic contaminants with SR-AOPs in livestock wastewater.

Insight in sulfadiazine degradation by peroxymonosulfate activated by polydopamine-derived nitrogen-doped carbon supported CoFe2O4: Co leaching inhibition and degradation enhancement

Heterogeneous catalyst-mediated sulfate radical-based advanced oxidation processes (SR-AOPs) showed excellent performance during antibiotics degradation. Spinel was a promising catalyst for SR-AOPs, but the secondary contamination due to metal ions leaching needed to be addressed. And the destruction of catalyst structure could lead to the reduction of catalytic activity and the difficulty of recovery. Thus, a novel nitrogen-doped carbon (NC)-supported CoFe2O4 (CoFe2O4@NC) was synthesized as the activator of PMS for sulfadiazine (SDZ) degradation under low Co leaching conditions. The consequences indicated that the CoFe2O4@NC/PMS system exhibited higher PMS decomposition efficiency and reaction stoichiometry efficiency than the bare CoFe2O4/PMS systems (CoFe2O4-180 and CoFe2O4-800), which in turn demonstrated a better SDZ removal performance. Under the condition of CoFe2O4@NC dosage 0.1 g/L, PMS concentration 0.5 mM, solution pH 6.8 and temperature 25°C, SDZ (20 mg/L) was almost completely degraded within 60 min. XPS analysis showed that the NC not only protected and stabilized CoFe2O4, but also provided additional active sites for PMS activation. During SDZ degradation, SO4•−, HO•, •O2− and 1O2 were involved in the reaction, among which SO4• and HO• made the main contribution. Meanwhile, CoFe2O4@NC could be recovered by magnetic separation, and showed great stability (Co leaching 0.852 mg/L) and reusability. In the fifth cycle experiment, 85.02 % SDZ degradation was obtained. Based on the detected intermediates (12 intermediates were identified) and DFT calculations, possible degradation pathways for SDZ in CoFe2O4@NC/PMS were proposed. The condensed dual descriptor indicated that the N7, N11, and C15 atoms on SDZ molecule were the main sites of electrophilic attack, which was consistent with the detected intermediates. The degradation of SDZ involved hydroxylation of NH2, cleavage of S−N and extrusion of SO2. This study explored the improvements made in NC support material to catalytic performance and resistance to dissolution of spinel, providing new insights for subsequent researches.

Nanostructured NiCo2S4 immobilized on nickel foam as recyclable catalyst for activating peroxymonosulfate toward doxycycline degradation: Performance and mechanism

The existing powder catalysts used in sulfate radical-based advanced oxidation processes (SR-AOPs) commonly suffer from severe limitation due to the difficulty of recycling and inadequate exposure of the active site. In this work, spinel sulfide (NiCo2S4) was uniformly grown on 3D nickel foam (NF) through a one-step hydrothermal route for the activation of peroxymonosulfate (PMS) toward highly efficient degradation of doxycycline (DOX). Due to the synergistic effect of Ni and Co in the NiCo2S4, the NiCo2S4/NF (0.6 g/L) combined with PMS (3.0 mmol L-1) can promote a nearly complete degradation (98.2 %) toward 0.3 mmol/L DOX within 6 min. Density functional theory (DFT) calculations illustrated that the NiCo2S4/NF can adsorb PMS through a unique Ni-S-Co structure and “conducting bridge” mode of NF, accelerating the electron transfer from NiCo2S4/NF to PMS and the subsequent O-O bond cleavage. Especially, the Co/Ni dual-site enhanced the adsorption of PMS and promotes electron transfer to form surface-activated PMS complex (catalyst-PMS*), leading to the generation of surface-bound reactive oxygen species (ROS) on the NiCo2S4 surface. Quenching experiments and ESR tests demonstrated that radicals such as SO4•-, 1O2, •OH and surface-bound ROS play a vital role in DOX degradation. Moreover, the potential mechanism and pathway of DOX degradation are reasonably deduced by investigating and analyzing the intermediates with liquid chromatography-mass spectromsetry (LC-MS). Consequently, this study provides a deep insight on the systhsis of spinel sulfide and its intrinsic mechanism of PMS activation toward organic contaminant degradation.

Preparation of iron selenide decorated 1T/2H molybdenum disulfide catalysts for peroxymonosulfate activation: Effect of phase transition

The sulfate radical-based advanced oxidation process is recognized as an effective approach for acetaminophen (ACT) degradation. Modification of MoS2 through phase engineering can contribute to enhancing peroxymonosulfate (PMS) activation performance. In this work, we decorated MoS2 with FeSe2, aiming to alter the 1T/2H phase ratio of MoS2. Experiments and calculations suggested that the incorporation of FeSe2 increases the activation pathway through the Fe(III)/Fe(II) cycle and prompts a phase transition from 2H to 1T, providing active sites and boosting charge transfer between FeSe2 and MoS2. The optimum catalyst (FeSe2@MoS2-10) showed high efficiency in PMS activation, achieving complete removal of ACT within 20 min. The pseudo-first-order rate constant (kapp) on this catalyst is 17.7 times higher than that of the MoS2/PMS system. This study provides a new direction for promoting phase transition and improving the catalytic reactivity of MoS2-based catalysts, expanding their potential applications in pharmaceutical wastewater treatment.

Potential application of SDSO-layered double hydroxide in wastewater treatment: Synergy between hydrophobicity and activation activity

The hydrophobic surface properties of catalysts, generally overlooked in the field of sulfate radical-based advanced oxidation processes (SR-AOPs), have significant potential in enhancing the applicability of catalysts in realistic wastewater treatment. The conflicting nature of hydrophobicity and activation activity presents considerable challenges in developing heterogeneous oxidation. To overcome such limitation, herein, different surfactants were employed to regulate the surface properties of CoCu-layered double hydroxides (LDH) for the activation of peroxymonosulfate (PMS). Our results demonstrated that by comparison with sodium dodecyl sulfate (SDS) and sodium laurate (SLA), sodium dodecyl sulfonate (SDSO) regulated LDH (SDSO-LDH) exhibited the most effective interpolation of organic anions into the interlayer space, simultaneously showing efficient ability for PMS activation and hydrophobicity. The SDSO-LDH/PMS system exhibited excellent degradation performance of various emerging contaminants (ECs), with Co(IV) = O and SO4•- species identified as the dominant oxidative intermediates. Density functional theory (DFT) calculations further confirmed the thermodynamic feasibility of these reactions. Moreover, the effective degradation of intrinsic organic substances in realistic wastewater and sustained hydrophobicity establishes SDSO-LDH a competitive candidate catalyst for SR-AOPs. The synergy between activation activity and hydrophobicity offers a novel perspective for the application of SR-AOPs in wastewater treatment.

Self-supporting CoFe2O4 nanoparticles on 2D g-C3N4/2D loofah activated carbon mediated peroxymonosulfate activation for tetracycline degradation

For antibiotic contaminants, biomass have been regarded as one of the most resource of functional carbonaceous materials due to its biocompatibility, biodegradability, and good adsorption/degradation performance. Herein, a self-supporting CoFe2O4 nanoparticles on 2D g-C3N4/2D loofah activated carbon (CoFe2O4/g-C3N4/BC) is successfully synthesized by simple hydrothermal method using loofah as carbon source and melamine as nitrogen source. The obtained CoFe2O4/g-C3N4/BC materials have a stable hierarchical sandwich structure with macroporous and mesoporous and a large surface area (189.52 m2/g), which can be used as an adsorbent/catalyst for the adsorption/degradation of organic pollutants. With these beneficial properties, the CoFe2O4/g-C3N4/BC material mediated peroxymonosulfate activation exhibits superior catalytic activity in the degradation of organic pollutants under ambient conditions. A model pollutant tetracycline (TC) can be rapidly degraded by 94.97 % within 25 min. The degradation efficiency was sustained at 88.21 % even after five operational cycles, with the cobalt metal leaching rate consistently below 50 μg/L. The inhibition experiment indicates that the main active species in the CoFe2O4/g-C3N4/BC + PMS system are SO4•−, HO• and 1O2, and the degradation of TC is achieved by the synergistic effect of free radical and non-radical pathways. This study provides a new perspective on the treatment of antibiotic wastewater via the sulfate radicals based-advanced oxidation processes (SR-AOPs).

Revolutionizing Tetracycline Hydrochloride Remediation: 3D Motile Light-Driven MOFs Based Micromotors in Harsh Saline Environments.

Traditional light-driven metal-organic-frameworks (MOFs)-based micromotors (MOFtors) are typically constrained to two-dimensional (2D) motion under ultraviolet or near-infrared light and often demonstrate instability and susceptibility to ions in high-saline environments. This limitation is particularly relevant to employing micromotors in water purification, as real wastewater is frequently coupled with high salinity. In response to these challenges, ultrastable MOFtors capable of three-dimensional (3D) motion under a broad spectrum of light through thermophoresis and electrophoresis are successfully synthesized. The MOFtors integrated photocatalytic porphyrin MOFs (PCN-224) with a photothermal component made of polypyrrole (PPy) by three distinct methodologies, resulting in micromotors with different motion behavior and catalytic performance. Impressively, the optimized MOFtors display exceptional maximum velocity of 1305±327µms-1 under blue light and 2357±453µms-1 under UV light. In harsh saline environments, these MOFtors are not only maintain high motility but also exhibit superior tetracycline hydrochloride (TCH) removal efficiency of 3578±510mgg-1, coupling with sulfate radical-based advanced oxidation processes and peroxymonosulfate. This research underscores the significant potential of highly efficient MOFtors with robust photocatalytic activity in effectively removing TCH in challenging saline conditions, representing a substantial advancement in applying MOFtors within real-world water treatment technologies.

ZIF-67-natural sponge derived macroarchitectures as efficient catalytic converters for 4-nitrophenol removal

Sulfate radical-based advanced oxidation processes (SR-AOPs) is a very efficient wastewater treatment technology and has great potential for environmental remediation. However, finding efficient catalysts for activation of peroxomonosulfate (PMS) is still challenge. In this work, we synthesized a ZIF-67-coated natural sponge composite (ZS) using the in-situ growth method, and the material obtained after carbonization (ZSC) was used to activate PMS for better removal of 4-nitrophenol (4-NP). Natural sponges as carriers for loaded MOF materials can better stimulate the ability of composites to activate PMS, for example: (1) Prevents deactivation of MOF particles due to the occurrence of aggregation; (2) Solves the problems caused by the powder characteristics of the MOF particles themselves, prevents secondary contamination, and is easy to recycle; (3) Limit the risk of loss of MOF particles. The removal efficiency of ZSC-activated PMS for 4-NP (10 ppm) was remarkable at 99 %. Natural sponges as carriers, are taken from the natural environment, which is more affinity with the environment, reduces the risk of pollution and highlights the sustainability of the material. This study proposes a green and sustainable material for the removal of 4-NP to provide technical support for water ecological management.

LaCoO3/Graphene Catalysts As a Novel Catalyst for Peroxymonosulfate Activation to Degrade Aquatic Organic Pollutants: A Singlet Oxygen-Dominated Nonradical Pathway

Trace organic pollutants including pharmaceuticals, industrial chemicals, pesticides, and personal care items pose considerable risks to the environment and human health due to their enduring nature, toxicity, and tendency to accumulate in biological systems [1,2]. In addressing this, sulfate radical-based advanced oxidation processes have emerged as highly promising advanced oxidation process methods for water and wastewater treatment in the past decade. Recently, transition metal-based perovskites like LaCoO3 nanoparticles have gained attention in sulfate radical-based advanced oxidation processes due to their structural and compositional flexibility, strong electronic conductivity, and ability to create oxygen vacancies [3]. However, their practical application is hindered by metal leaching during wastewater treatment. Additionally, the robust and scalable synthesis of stable perovskite-based catalysts with large surface areas is crucial for their practical implementation in wastewater treatment but has been rarely achieved so far.In this study, we developed a cost-effective and scalable approach to produce novel LaCoO3/graphene nanocomposites for eliminating organic pollutants from wastewater. These newly developed catalysts demonstrated outstanding catalytic degradation (> 99%) of diclofenac, metoprolol, carbamazepine, and bisphenol A at a high concentration (40 mg/l) in less than 10 minutes in the peroxymonosulfate activation system, with a respective mineralization of 57%, 55%, 61%, and 62%. This improved performance compared to LaCoO3 nanoparticles is attributed to the nanocomposite's abundant oxygen vacancies, synergistic effects between LaCoO3 and graphene, and its larger surface area. More importantly, the LaCoO3/graphene nanocomposites showed good catalytic performance over a broad range of pH (from 3 to 11) and exhibited excellent reusability with consistent catalytic activity. Moreover, their catalytic efficacy remained largely unaffected in samples of drinking water and tap water, presenting high resistance to co-existing ions and NOM, proving the potential of LaCoO3/graphene materials for practical application in real wastewater treatment systems.The fabrication of LaCoO3/graphene composites effectively prevents cobalt leaching and increases the content of Co2+ in the structure, resulting in significantly higher catalytic activity than that of pure LaCoO3. Experiments involving radical quenching and electron paramagnetic resonance revealed the involvement of both radical (SO4 •–, •OH and O2 •–) and non-radical pathways (1O2) in pollutant degradation, with the 1O2 radical playing a predominant role in the oxidation of the pollutant. The relative contributions of •OH, SO4 •–, and 1O2/O2 •– were determined to be 13.4%, 32.6%, and 54% for bisphenol A removal, respectively. Overall, our findings demonstrate the potential utilization of the LaCoO3/graphene system for peroxymonosulfate activation in environmental remediation. REFERENCES: [1] A. Asghar, M. Hammad, K. Kerpen, F. Niemann, A.K. Al-Kamal, D. Segets, H. Wiggers, T.C. Schmidt, Ozonation of carbamazepine in the presence of sulfur-dopped graphene: Effect of process parameters and formation of main transformation products, Sci. Total Environ. 864 (2023) 161079. https://doi.org/https://doi.org/10.1016/j.scitotenv.2022.161079.[2] M. Hammad, P. Fortugno, S. Hardt, C. Kim, S. Salamon, T.C. Schmidt, H. Wende, C. Schulz, H. Wiggers, Large-scale synthesis of iron oxide/graphene hybrid materials as highly efficient photo-Fenton catalyst for water remediation, Environ. Technol. Innov. 21 (2021) 101239. https://doi.org/https://doi.org/10.1016/j.eti.2020.101239.[3] M. Hammad, B. Alkan, A.K. Al-kamal, C. Kim, M.Y. Ali, S. Angel, H.T.A. Wiedemann, D. Klippert, T.C. Schmidt, C.W.M. Kay, H. Wiggers, Enhanced heterogeneous activation of peroxymonosulfate by Ruddlesden-Popper-type La2CoO4+δ nanoparticles for bisphenol A degradation, Chem. Eng. J. 429 (2022) 131447. https://doi.org/https://doi.org/10.1016/j.cej.2021.131447.

Carbon defects-enriched NBC-C3N5@CoMn with ultrafast modulation of redox couples for efficient degradation of contaminant

The inefficiency of catalysts in sulfate radical-based advanced oxidation processes (SR-AOPs) is primarily attributed to the sluggish circulation of redox couples. Herein, a carbon defects-enriched NBC-C3N5@CoMn (NCC) was synthesized through a self-assembly approach. The carbon defects within the NCC induce the electron trap effect, thereby facilitating the efficient cycling of redox couples in photo-Fenton-like processes during contaminant degradation. This effect enables the self-regeneration of the NCC catalyst. The reductive redox couples (Co (II) and Mn (II)) are continuously regenerated following the degradation process. Within the NCC, CoMn layered double hydroxides (LDHs) act as primary active sites, promoting the generation of hydroxyl radicals (•OH), sulfate radicals (SO4•-) and singlet oxygen (1O2) through continuous electron gain and loss. Additionally, the internal electric field established within the NCC further accelerates electron transfer. Density Functional Theory (DFT) calculations confirm that the carbon defects-enriched NCC exhibits lower adsorption energies and higher electron transfer efficiencies than carbon defect-deficient NCC. This study introduces a novel photocatalyst with self-regenerating capabilities, presenting an innovative approach to regulate redox couples in SR-AOPs for sustainable degradation.

“Frozen” π-π stacking on perylene diimide molecules induces oxygen vacancies synergistic activation of persulfate towards degradation of tetracycline

Oxygen vacancy-rich self-assembled perylene diimide (OV-SA-PDI) supramolecules were prepared via freeze-drying, which froze the molecular backbone by retaining π-π stacking to induce additional OVs. The OVs content on OV-SA-PDI (1.956 × 1013 spins·mm−3) was 1.9 times that of SA-PDI (1.029 × 1013 spins·mm−3) with vacuum drying. The photocatalytic performance of OV-SA-PDI was demonstrated to be excellent in activating persulfate (PS) to degrade tetracycline (TC), achieving a remarkable degradation efficiency of 94.6% in 60 min under visible light (Vis). Mechanistic studies revealed a synergistic interaction among OV-SA-PDI, PS, and Vis to produce an abundance of active species. Vis activated a small portion of PS to produce ∙OH and SO4∙−, whereas the photogenerated electrons generated by OV-SA-PDI directly cleaved the O-O bond to produce abundant SO4∙−. Furthermore, the OVs acted as an electron trap to promote carrier separation and produced 10.0 μM 1O2 within 12 min. The active species were determined to decompose TC into low-toxicity products with lower molecular weights (m/z = 352, 340, and 227). This study presented a novel approach to the introduction of OVs into organic semiconductors and offered a mechanistic analysis of the synergistic relationship between defective organic semiconductors and sulfate radical-based advanced oxidation processes for wastewater treatment.

FeCo@hydrochar nanocomposites as efficient peroxymonosulfate activator for organic pollutant degradation.

Sulfate radical-based advanced oxidation processes (SR-AOPs) are renowned for their exceptional capacity to degrade refractory organic pollutants due to their wide applicability, cost-effectiveness, and swift mineralization and oxidation rates. The primary sources of radicals in AOPs are persulfate (PS) and peroxymonosulfate (PMS) ions, sparking significant interest in their mechanistic and catalytic aspects. To develop a novel nanocatalyst for SR-AOPs, particularly for PMS activation, we synthesized carbon-coated FeCo nanoparticles (NPs) using solvothermal methods based on the polyol approach. Various synthesis conditions were investigated, and the NPs were thoroughly characterized regarding their structure, morphology, magnetic properties, and catalytic efficiency. The FeCo phase was primarily obtained at [OH-] / [Metal] = 26 and [Fe] / [Co] = 2 ratios. Moreover, as the [Fe]/[Co] ratio increased, the degree of xylose carbonization to form a carbon coating (hydrochar) on the NPs also increased. The NPs exhibited a spherical morphology with agglomerates of varying sizes. Vibrating-sample magnetometer analysis (VSM) indicated that a higher proportion of iron resulted in NPs with higher saturation magnetization (up to 167.8 emu g-1), attributed to a larger proportion of FeCo bcc phase in the nanocomposite. The best catalytic conditions for degrading 100ppm Rhodamine B (RhB) included 0.05g L-1 of NPs, 2mM PMS, pH 7.0, and a 20-min reaction at 25°C. Notably, singlet oxygen was the predominant specie formed in the experiments in the SR-AOP, followed by sulfate and hydroxyl radicals. The catalyst could be reused for up to five cycles, retaining over 98% RhB degradation, albeit with increased metal leaching. Even in the first use, dissolved Fe and Co concentrations were 0.8 ± 0.3 and 4.0 ± 0.5mg L-1, respectively. The FeCo catalyst proved to be effective in dye degradation and offers the potential for further refinement to minimize Co2+ leaching.

Efficient removal of tetrabromobisphenol A in the Mn1Fe0.5Al0.5-LDO@BC/peroxymonosulfate water purification system

Tetrabromobisphenol A (TBBPA) brominated flame retardants in water posed threat to the ecological system due to its persistence and biomagnification. In this work, an efficient water purification system based on sulfate radical-based advanced oxidation processes (SR-AOPs) with Mn1Fe0.5Al0.5-LDO@BC as the core was constructed by adjusting the key preparation parameters, optimizing catalyst performance and exploring operating conditions. Under the optimal conditions of Mn1Fe0.5Al0.5-LDO@BC/PMS system (calcination temperature of 600 oC, 0.1 g/L Mn1Fe0.5Al0.5-LDO@BC, 0.15 mM PMS, pH value of 7–), 15 mg/L TBBPA was almost completely degraded within 30 min. Mn1Fe0.5Al0.5-LDO@BC/PMS water purification system exhibited resistance to inorganic anions and humic acid. In addition, Mn1Fe0.5Al0.5-LDO@BC reflected better cycle stability and ecological environmental protection. Electron paramagnetic resonance (EPR) and quenching experiments verified the existence of a large number of dominant active species in the water purification system, especially the contribution of O2•– and 1O2 to the degradation of TBBPA. Finally, the catalytic mechanism and possible degradation pathway of TBBPA were elucidated, and the toxicity of the intermediates was predicted. This work provided novel insights into the efficient purification of TBBPA brominated flame retardants in wastewater.

Dual activation of peroxymonosulfate with FeS2@Co3O4-C catalyst and visible light for the efficient degradation of tetracycline

Antibiotics have garnered global attention as a pressing concern due to their wide spread discharge to the environment and resulting significant threats to both human health and the environment. The Sulfate Radical-based Advanced Oxidation Processes (SR-AOPs) technique has already been verified as an effective process for pollutant degradation. Herein, FeS2@Co3O4-C composites, utilizing ZIF-67-derived Co3O4-C as the substrate material, were fabricated using a single-step solvothermal technique for the degradation of tetracycline (TC) by activated peroxymonosulfate (PMS) in combination with visible light irradiation. In the FeS2@Co3O4-C/PMS/Vis system, the FeS2@Co3O4-C showed better activation performance than the single chemical activation system or photocatalytic system, with 97.2 % TC removed in 20 min. The FeS2@Co3O4-C composite material was thoroughly investigated employing X-ray diffraction (XRD) for analyzing its crystal structure, transmission electron microscopy (TEM) for detailed structural insights, scanning electron microscopy (SEM) for morphological examination, and X-ray photoelectron spectroscopy (XPS) for the elemental valence states. The quenching experiments, along with EPR test, revealed that the primary active oxygen species consisted of 1O2, O2·-, and h+. The results presented here suggest the impressive stability and recyclability of FeS2@Co3O4-C making it a potential candidate as an efficient catalyst for initiating the activation of PMS in degrading persistent organic pollutants present in water.

Insight into the sulfite activation by Fe-rich sludge-derived biochar for efficient organic contaminant degradation: The role of iron species

Sulfate radical-based advanced oxidation processes driven by sulfite [S(IV)] activation offer a sustainable and cost-effective approach for environmental remediation. The utilization of abundant iron oxide species in Fe-rich sludge for S(IV) activation presents a cost-effective and eco-friendly solution, making it an attractive option for Fe-rich sludge disposal and water treatment. Herein, an efficient S(IV) activation system was developed by using Fe-rich sludge-derived biochar (FBC) for the first time. The performance of S(IV) activation by different pyrolyzed FBCs was evaluated in terms of tetracycline (TC) degradation. The highest degradation efficiency of TC was achieved 95.0 % in the S(IV)/FBC700 under the optimum conditions. The reactive radical species responsible for TC degradation in the system were confirmed to be SO4•−. The present work opens up new possibilities for the development of novel advanced oxidation processes utilizing the waste Fe-rich sludge.

Study on high-efficiency sulfide removement using sulfate radical-based AOPs and its oxidation mechanism of refractory gold ore

Pyrite enclosure poses a significant challenge in refractory gold ore processing, inhibiting gold leaching. This study explores Sulfate Radical-based Advanced Oxidation Processes (SR-AOPs) as an effective alternative for pretreating such ores. The oxidation pretreatments were performed under heat and ultrasound activation methods, including heat and ultrasound, and the influences of pretreatment time, pH, ultrasound power, pretreatment temperature, and precursor (PDS) concentration were investigated. Both ultrasonic and heat activation effectively mitigate the negative impact of pyrite enclosure on gold leaching. Specifically, the gold leaching rate improved from 21.9 % to 46.1 % and 74.9 % with heat and ultrasound activation, respectively The and generated by PDS dominate the pyrite oxidation according to EPR and quenching tests. Meanwhile, the SR-AOPs treatment also promotes the interactions between pyrite enclosure and leaching agent, reducing the negative influences of pyrite. Kinetic studies indicated that the oxidation processes are different under heat and ultrasound activation. Heat activation is governed by an interfacial chemical reaction, with an activation energy of 25.57 kJ/mol. In contrast, ultrasound-induced cavitation and microjets remove the oxidation layer, disrupt the pyrite crystal structure, and expose encapsulated gold. These effects accelerate pyrite oxidation, shifting the kinetic control step from interfacial chemical reaction to internal diffusion, with a reduced activation energy of 35.06 kJ/mol.

Highly efficient activation of sulfite by oxygen vacancies-enriched ZnCe0.4Fe1.6O4 for methylparaben degradation

The exploitation of a novel catalyst was of great significance for sulfate radical-based advanced oxidation processes (AOPs) using sulfite as the precursor of sulfate radical. Herein, oxygen vacancies-enriched ZnCe0.4Fe1.6O4 was prepared and applied to activate sulfite for the degradation of methylparaben (MeP). ZnCe0.4Fe1.6O4 showed superior catalytic activity than that of ZnFe2O4, allowing an 85.2 % removal efficiency of MeP within 60 min. The initial pH showed a significant effect on the catalytic performance, and about 92.1 % of MeP could be removed at pH of 9.56 in ZnCe0.4Fe1.6O4/sulfite system. The quenching experiments and EPR tests verified SO4− and OH were the main reactive oxygen species (ROS) in ZnCe0.4Fe1.6O4/sulfite system. The catalytic mechanism was elucidated further by X-ray photoelectron spectroscopy (XPS) analysis of ZnCe0.4Fe1.6O4 before and after the reaction. The recycles of Zn2+/Zn3+, Fe2+/Fe3+ and Ce3+/Ce4+ were the key factor for the activation of sulfite, and oxygen vacancies on catalyst surface promoted the activation of sulfite. The degradation intermediates of MeP were determined by a liquid chromatography-mass spectrometer (LC-MS) and the degradation pathway was proposed. The reusability of ZnCe0.4Fe1.6O4 was evidenced by the recycling experiments. In addition, ZnCe0.4Fe1.6O4/sulfite system exhibited excellent applicability in treating other organic contaminants.

Wastewater Treatment: The Emergence of Cobalt Ferrite and Its Composites in Sulfate Radical-Based Advanced Oxidation Processes

Wastewater Treatment: The Emergence of Cobalt Ferrite and Its Composites in Sulfate Radical-Based Advanced Oxidation Processes

New insights into antifouling property and interfacial mechanism in photo-Fenton membrane distillation

Membrane distillation (MD), boasting high interception efficiency and low operational pressures, emerges as an innovative membrane technology. However, the occurrence of membrane fouling due to interaction between natural organic matter (NOM) and inorganic ions during the MD process curtails water purification efficiency, thereby constraining its potential applications. To address this quandary, this study integrates sulfate radical-based advanced oxidation processes (SR-AOPs) into MD technology to bolster membrane fouling control. A straightforward hydrothermal method coupled with vacuum filtration was employed to synthesize a Co3O4/Nitrogen-modified carbon quantum dots (NCDs)/PVDF (CN-PVDF) membrane for the first time, which was utilized in the MD treatment of simulated humic acid (HA) wastewater. Under visible light irradiation (1.9 kW/m2), CN-PVDF membrane activation of peroxymonosulfate (PMS) effectively altered the chemical attributes of the MD feed solution and reduced organic matter concentration. Moreover, it dismantled the carboxyl sites on HA that interact with Ca2+, consequently attenuating the formation of organic–inorganic complex pollutants. The XDLVO analysis showcased that photo-Fenton oxidation led to a diminishment in pollutant hydrophobicity, correlating with a 17.59 kT reduction in pollutant-membrane adsorption and a 7.47 kT amplification in adhesion barriers. This strategy transformed the initial two-stage fouling mode into a singular one, which significantly decreased the flux decline and the fouling layer thickness. Furthermore, the CN-PVDF membrane demonstrated self-cleaning capabilities via photo-Fenton. This study advances an innovative approach to bolster the fouling resistance of MD membranes and provides substantial theoretical support for the integration of SR-AOPs and MD technologies.