Synergistic adsorption and oxidative degradation of polyvinyl alcohol by acidified OMS-2: Catalytic mechanism, degradation pathway and toxicity evaluation

Insight into the role of reactive species on catalyst surface underlying peroxymonosulfate activation by P-Fe2MnO4 loaded on bentonite for trichloroethylene degradation

In this study, bentonite supporting phosphorus-doped Fe2MnO4 (BPF) was synthesized and applied for PMS activation to degrade TCE. Morphology and structure characterization results indicated the successfully synthesized of BPF, and the BPF/PMS system not only featured high TCE removal (97.4%) but also high reaction rate constant (kobs = 0.0554 min-1) and PMS utilization (70.4%, kobs = 0.0228 min-1). According to the results of various experiments, massive oxygen vacancies on P-Fe2MnO4 alter its charge balance and facilitate the electron transfer process named adjacent transfer (direct electron capture by adsorbed PMS from adjacent TCE). Mn(III) is the main adsorption site for PMS, and the hydroxyl groups on the catalyst (Fe sites of P-Fe2MnO4, Si and Al sites of bentonite) can also offer binding sites for PMS. The hydrogen-bonded PMS on Fe(III) and Mn(III) sites will subsequently accept the discharged electrons to generate free radicals and high-valent metal species. Meanwhile, electron loss of HSO5- that chemically bonded to hydroxyl groups on bentonite will generate SO5•-, which will further produce 1O2 through self-bonding. the active species on the catalyst surface contribute 65% of TCE degradation in the heterogeneous catalytic oxidation system.

Cu/N co-doped biochar activating PMS for selective degrading paracetamol via a non-radical pathway dominated by singlet oxygen and electron transfer

The non-free radical oxidation pathway (PMS-NOPs) of peroxymonosulfate (PMS) holds significant promise for practical wastewater treatment applications, owing to its low oxidation potential, high PMS utilization rate, and robust anti-interference capability in the degradation of pollutants. A novel activator copper nitrogen co-doped porous biochar (Cu-N-BC) with rich defect edges and functional groups was obtained by adding Cu and N to the biochar matrix generated by sodium alginate through pyrolysis in this study. Under the condition of 1 mM PMS, 30 mg/L activator was used to activate PMS and achieve efficient degradation of 10 mg/L paracetamol (PCT) within 15 min, with a high reaction rate constants (kobs) of 0.391 min-1. The activation mechanism of the Cu-N-BC/PMS/PCT system was a non-radical activation pathway with the dominance of singlet oxygen (1O2) and the presence of catalyst-mediated electron transfer. The graphite nitrogen, pyridine nitrogen, and Cu-N coordination introduced by Cu/N co-doping, as well as the carbon skeleton and CO functional group of biochar, were considered active sites that promote the 1O2 generation. The Cu-N-BC/PMS system exhibits strong stability, eco-friendliness, effective mineralization, and interference resistance across diverse pH levels (3-11) and interfering ions, including Cl-, H2PO4-, NO3-, SO42-, and humic acid. Remarkably, it efficiently degrades PCT in tap and lake water, achieving a notable 63.73% TOC mineralization rate, with leached copper ions below 0.02 mg/L. This research introduces a novel method for obtaining metal nitrogen carbon activators and enhances understanding of PMS non-radical activation pathways and active sites.

Bimetallic iron-nickel phosphide as efficient peroxymonosulfate activator for tetracycline hydrochloride degradation: Performance and mechanism

Sulfate radical-based advanced oxidation processes with (SR-AOPs) are widely employed to degrade organic pollutants due to their high efficiency, cost-effectiveness and safety. In this study, a highly active and stable FeNiP was successfully prepared by reduction and heat treatment. FeNiP exhibited high performance of peroxymonosulfate (PMS) activation for tetracycline hydrochloride (TC) removal. Over a wide pH range, an impressive TC degaradation efficiency 97.86% was achieved within 60 min employing 0.1 g/L FeNiP and 0.2 g/L PMS at room temperature. Both free radicals of SO4·-, ·OH, ·O2- and non-free radicals of 1O2 participated the TC degradation in the FeNiP/PMS system. The PMS activation ability was greatly enhanced by the cycling between Ni and Fe bimetal, and the active site regeneration was achieved due to the existence of the negatively charged Pn-. Moreover, the FeNiP/PMS system exhibited substantial TC degradation levels in both simulated real-world disturbance scenarios and practical water tests. Cycling experiments further affirmed the robust stability of FeNiP catalyst, demonstrating sustained degradation efficiency of approximately 80% even after four cycles. These findings illuminate its promising potential across natural water bodies, presenting an innovative catalyst construction approach for PMS activation in the degradation of antibiotic pollutants.

The inherent nature of N/P heteroatoms in Sargassum fusiforme seaweed biochar enhanced the nonradical activation of peroxymonosulfate for acetaminophen degradation in aquatic environments

This study investigated the catalytic activity of biochar materials derived from algal biomass Sargassum fusiforme (S. fusiforme) for groundwater remediation. A facile single-step pyrolysis process was used to prepare S. fusiforme biochar (SFBCX), where x denotes pyrolysis temperatures (600 °C-900 °C). The surface characterization revealed that SFBC800 possesses intrinsic N and P heteroatoms. The optimum experimental condition for acetaminophen (AAP) degradation (>98.70%) was achieved in 60 min using 1.0 mM peroxymonosulfate (PMS), 100 mg L-1 SFBC800, and pH 5.8 (unadjusted). Moreover, the degradation rate constant (k) was evaluated by the pseudo-first-order kinetic model. The maximum degradation (>98.70%) of AAP was achieved within 60 min of oxidation. Subsequently, the k value was calculated to be 6.7 × 10-2 min-1. The scavenger tests showed that radical and nonradical processes are involved in the SFBC800/PMS system. Moreover, the formation of reactive oxygen species (ROS) in the SFBC800/PMS system was confirmed using electron spin resonance (ESR) spectroscopy. Intriguingly, both radical (O2•-, •OH, and SO4•-) and nonradical (1O2) ROS were formed in the SFBC800/PMS system. In addition, electrochemical studies were conducted to verify the electron transfer process of the nonradical mechanism in the SFBC800/PMS system. The scavenger and electron spin resonance (ESR) spectroscopy showed that singlet oxygen (1O2) is the predominant component in AAP degradation. Under optimal condition, the SFBC800/PMS system reached ∼81% mineralization of AAP within 5 min and continued to ∼85% achieved over 60 min of oxidation. Coexisting ions and different aqueous matrices were investigated to examine the feasibility of the catalyst system, and the SFBC800/PMS system was found to be effective in the remediation of AAP-contaminated groundwater, river water, and effluent water obtained from wastewater treatment plants. Moreover, the SFBC800-activated PMS system demonstrated reusability. Our findings indicate that the SFBC800 catalyst has excellent catalytic activity for AAP degradation in aquatic environments.

Novel calcium oxide activated peroxymonosulfate system for methylene blue removal: Identification of key influencing factors, transformation pathway and toxicity assessment

The activation of peroxymonosulfate (PMS) has gained significant interest in the removal of organic pollutants. However, traditional methods usually suffer from drawbacks such as secondary contamination and high energy requirements. In this study, we propose a green and cost-effective approach utilizing calcium oxide (CaO) to activate PMS, aiming to construct a simple and reliable PMS based advanced oxidation processes (AOPs). The proposed CaO/PMS system achieved fast degradation of methylene blue (MB), where the degradation rate of CaO/PMS system (0.24 min-1) was nearly 2.67 times that of PMS alone (0.09 min-1). Under the optimized condition, CaO/PMS system exhibited remarkable durability against pH changes, co-exists ions or organic matters. Furthermore, singlet oxygen (1O2) was identified as the dominant reactive oxygen species by electron paramagnetic resonance (EPR) and quenching tests. Accordingly, the degradation pathways of MB are proposed by combing the results of LC/MS analysis and density functional theory (DFT) calculations, and the predicted ecotoxicity of the generated byproducts evaluated by EOCSAR could provide systematic insights into the fates and environmental risks of MB. Overall, the study provides an eco-friendly and effective strategy for treating dyeing wastewater, which should shed light on the application of PMS based AOPs.

Polydopamine-modified MOF-5-derived carbon as persulfate activator for aniline aerofloat degradation

Residual flotation chemicals in beneficiation wastewater seriously threaten local ecosystems, such as groundwater or soil, and must be treated effectively. Currently, the degradation of organic pollutants using nitrided MOFs-derived carbon to activate persulfate (PDS) has attracted considerable attention. Hence, we developed a new synthetic strategy to load dopamine hydrochloride (PDA) onto MOF-5-derived porous carbon (PC) to form NPC, and the degradation of a typical flotation Aniline aerofloat (AAF) at high salinity by a low dose of the NPC/PDS system was investigated. Several characterization analyses such as TEM, XRD, Raman, FT-IR and XPS demonstrated that the nitrogen-rich indolequinone unit in PDA provided nitrogen to PC during the pyrolysis process. This enabled the core-shell structure of NPC and the synergy among the multiple components to induce the AAF degradation by PDS over a wide pH scale in a short period of time. It was deduced that the degradation of AAF by the NPC-8/PDS system was a non-radical pathway dominated by 1O2, which relied mainly on the conversion of superoxide radicals (O2•-) and surface-bound radicals. Among them, the pyridine N in the sp2 hybrid carbon was considered as a possible active site. This non-radical pathway was resistant to pH changes and background substances in the water, and well overcame the inhibition of the reaction by natural organic substances and inorganic anions in natural water. In this study, A novel approach to the synthesis of homogeneous MOFs nuclear-derived porous carbon was proposed and the application of MOFs-derived porous carbon for AAF remediation of mineral processing wastewater was broadened.

Magnetized algae catalyst by endogenous N to effectively trigger peroxodisulfate activation for ultrafast degraded sulfathiazole: Radical evolution and electron transfer

An innovative Fe-N co-coupled catalyst MN-2 was prepared from waste spirulina by co-pyrolysis as a highly active carbon-based catalyst for the activation of peroxydisulfate (PDS) for the degradation of sulfathiazole (ST). The protein-rich raw material Spirulina provided sufficient N during the pyrolysis process, thus achieving N doping without an additional nitrogen source, optimizing the interlayer structure of the biochar material and effectively inhibiting the leaching of the ligand metal Fe. MN-2 showed highly efficient catalytic activity for peroxydisulfate (PDS), with a degradation efficiency of 100% for ST within 30 min and a kinetic constant (kobs) reached 0.306 min-1, benefiting from the excellent adsorption ability of MN-2 forming MN-2-PDS* complexes and the electron transfer process generated by Fe3+ and Fe2+ cycling, oxygen-containing functional groups. The effects of PDS dosage, initial pH and coexisting anions on the oxidation process were also investigated. Free radical quenching, electron paramagnetic resonance and electrochemical measurements were employed to explain the hydroxyl (·OH) and sulfate (SO4·-) as the dominant active species and the electron transfer effect on the removal of ST. MN-2 maintained a ST removal rate of 84% after four recycling experiments, showing a high reusability performance. This work provides a simple way to prepare magnetized N-doped biochar, a novel catalyst (MN-2) for efficient activation of PDS for ST degradation, and a feasible method for removing sulfanilamide antibiotics in water environment.

Harnessing the power of natural minerals: A comprehensive review of their application as heterogeneous catalysts in advanced oxidation processes for organic pollutant degradation

The release of untreated wastewater into water bodies has become a significant environmental concern, resulting in the accumulation of refractory organic pollutants that pose risks to human health and ecosystems. Wastewater treatment methods, including biological, physical, and chemical techniques, have limitations in achieving complete removal of the refractory pollutants. Chemical methods, particularly advanced oxidation processes (AOPs), have gained special attention for their strong oxidation capacity and minimal secondary pollution. Among the various catalysts used in AOPs, natural minerals offer distinct advantages, such as low cost, abundant resources, and environmental friendliness. Currently, the utilization of natural minerals as catalysts in AOPs lacks thorough investigation and review. This work addresses the need for a comprehensive review of natural minerals as catalysts in AOPs. The structural characteristics and catalytic performance of different natural minerals are discussed, emphasizing their specific roles in AOPs. Furthermore, the review analyzes the influence of process factors, including catalyst dosage, oxidant addition, pH value, and temperature, on the catalytic performance of natural minerals. Strategies for enhancing the catalytic efficiency of AOPs mediated by natural minerals are explored, mainly including physical fields, reductant addition, and cocatalyst utilization. The review also examines the practical application prospects and main challenges associated with the use of natural minerals as heterogeneous catalysts in AOPs. This work contributes to the development of sustainable and efficient approaches for organic pollutant degradation in wastewater.

Efficient degradation of phenol by MnOOH-rGO composite with high peroxymonosulfate utilization efficiency

A high-performance, durable, low-cost, and environmentally friendly catalyst is highly desired in advanced oxidation processes (AOPs) for water treatment. Considering the activity of Mn(Ⅲ) and the superior catalytic properties of reduced graphene oxide (rGO) in peroxymonosulfate (PMS) activation, rGO-modified MnOOH nanowires (MnOOH-rGO) were fabricated by a hydrothermal method for phenol degradation. The results showed that the composite synthesized at 120 °C with 1 wt% rGO dopant exhibited the best performance for phenol degradation. Nearly 100% of the phenol was removed by MnOOH-rGO within 30 min, which is higher than the removal rate of pure MnOOH (70%). The effects of catalyst dosages, PMS concentration, pH, temperature, and anions (Cl-, NO3-, HPO42-and HCO3-) on phenol degradation were investigated. The removal rate of chemical oxygen demand (COD) reached 26.4%, with a low molar ratio of PMS to phenol at 5:1 and a high PMS utilization efficiency (PUE) of 88.8%. The phenol removal rate remained more than 90% after five recycle with less than 0.1 mg L-1 leakage of manganese ions. Together with the results of radical quenching experiments, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectroscopy (EPR), electron transfer and 1O2 were proved to dominate the activation process. During the direct electrons transfer process, the electrons transfer from the phenol to PMS by using the Mn(Ⅲ) as the mediate with a stoichiometric ratio between PMS and phenol at 1:2, which mainly contributed to the high PUE. This work provides new insight into a high-performance Mn(Ⅲ) based catalyst on PMS activation with high PUE, good reusability, and environmentally friendly for removing organic pollutants.

Visible-light photocatalytic degradation of water-soluble polyvinyl alcohol in aqueous solution by Cu2O@TiO2: Optimization of conditions, mechanisms and toxicity analysis

Polyvinyl alcohol (PVA), a water-soluble synthetic polymer, is one of the most prevalent non-native polyvinyl alcohols found in the environment. Due to its inherent invisibility, its potential for causing severe environmental pollution is often underestimated. To achieve efficient degradation of PVA in wastewater, a Cu2O@TiO2 composite was synthesized through the modification of titanium dioxide with cuprous oxide, and its photocatalytic degradation of PVA was investigated. The Cu2O@TiO2 composite, supported by titanium dioxide, facilitated photocarrier separation and demonstrated high photocatalytic efficiency. Under alkaline conditions, the composite exhibited a 98% degradation efficiency for PVA solutions and a 58.7% PVA mineralization efficiency. Radical capture experiments and electron paramagnetic resonance (EPR) analyses revealed that superoxide radicals primarily drive the degradation process within the reaction system. Throughout the degradation process, PVA macromolecules are broken down into smaller molecules, including ethanol, and compounds containing aldehyde, ketone, and carboxylic acid functional groups. Although the intermediate products exhibit reduced toxicity compared to PVA, they still pose certain toxic hazards. Consequently, further research is necessary to minimize the environmental impact of these degradation products.

Characterization of solid and liquid carbonization products of polyvinyl chloride (PVC) and investigation of the PVC-derived adsorbent for the removal of organic compounds from water

The transformation of plastic wastes into value-added carbon materials is a promising strategy for the recycling of plastics. Commonly used polyvinyl chloride (PVC) plastics are converted into microporous carbonaceous materials using KOH as an activator via simultaneous carbonization and activation for the first time. The optimized spongy microporous carbon material has a surface area of 2093 m² g^-1 and a total pore volume of 1.12 cm³ g^-1, and aliphatic hydrocarbons and alcohols are yielded as the carbonization by-products. The PVC-derived carbon materials exhibit outstanding adsorption performance for removing tetracycline from water, and the maximum adsorption capacity reaches 1480 mg g^-1. The kinetic and isotherm patterns for tetracycline adsorption follow the pseudo-second-order and Freundlich models, respectively. Adsorption mechanism investigation indicates that pore filling and hydrogen bond interaction are mainly responsible for the adsorption. This study provides a facile and environmentally friendly approach for valorizing PVC into adsorbents for wastewater treatment.