Green synthesis of manganese-cobalt-tungsten composite oxides for degradation of doxycycline via efficient activation of peroxymonosulfate

Catalytic degradation of diclofenac by ZnO-Co3O4: identification of major intermediates and degradation pathway

ZnO-Co3O4 material was successfully synthesized by the co-precipitation method and used as a catalyst for the removal of diclofenac sodium (DCF). ZnO-Co3O4 exhibited higher catalytic activity in the catalytic process compared to the photocatalytic processes. Under optimum conditions, the activation of peroxymonosulfate (PMS) by ZnO-Co3O4 achieved approximately 99% removal of DCF, confirming the effective adsorption and activation of PMS. Quenching experiments indicated that the reactive oxygen species (ROS) responsible for the degradation of DCF by the ZnO-Co3O4/PMS system are singlet oxygen (1O2) and superoxide radicals (O2•-). The activation of PMS by ZnO-Co3O4 was associated with the coexistence and interaction between Co(II) and Co(III), as well as the formation of oxygen vacancies (V0) in ZnO. Cobalt leaching was negligible, and the degradation rate remained constant after four cycles, indicating the excellent stability and reusability of the ZnO-Co₃O₄ catalyst. Additionally, eight degradation products of DCF were identified by LC-ESI-MS, and their toxicity was evaluated using ECOSAR software (version 2.2). In conclusion, the ZnO-Co3O4/PMS system is a promising catalytic process for the degradation of organic molecules.

Development of tungsten-modified iron oxides to decompose an over-the-counter painkiller, Acetaminophen by activating peroxymonosulfate

Acetaminophen (APAP) is a well-known type of over-the-counter painkillers and is frequently found in surface waterbodies, causing hepatotoxicity and skin irritation. Due to its persistence and chronic effects on the environment, innovative solutions must be provided to decompose APAP, effectively. Innovative catalysts of tungsten-modified iron oxides (TF) were successfully developed via a combustion method and thoroughly characterized using SEM, TEM, XRD, XPS, a porosimetry analysis, Mössbauer spectroscopy, VSM magnetometry, and EPR. With the synthesis method, tungsten was successfully incorporated into iron oxides to form ferrites and other magnetic iron oxides with a high porosity of 19.7 % and a large surface area of 29.5 m2/g. Also, their catalytic activities for APAP degradation by activating peroxymonosulfate (PMS) were evaluated under various conditions. Under optimal conditions, TF 2.0 showed the highest APAP degradation of 95 % removal with a catalyst loading of 2.0 g/L, initial APAP concentration of 5 mg/L, PMS of 6.5 mM, and pH 2.15 at room temperature. No inhibition by solution pHs, alkalinity, and humic acid was observed for APAP degradation in this study. The catalysts also showed chemical and mechanical stability, achieving 100 % degradation of 1 mg/L APAP during reusability tests with three consecutive experiments. These results show that TFs can effectively degrade persistent contaminants of emerging concern in water, offering an impactful contribution to wastewater treatment to protect human health and the ecosystem.

Peroxymonosulfate activation by cobalt-doped ferromanganese magnetic oxides through singlet oxygen and radical pathways for efficient sulfadiazine degradation

In this paper, cobalt-doped MnFe2O4 (CMFO-0.4) with oxygen vacancies was successfully synthesised by the sol-gel method and applied as a high-performance catalyst for the activation of peroxomonosulfate (PMS). The catalyst showed an excellent catalytic effect for the degradation of sulfadiazine (SDZ) by activated PMS, and the degradation rate can reach 100% in 10 minutes. The effects of different conditions on the degradation of SDZ were investigated, and it was determined that the optimal concentrations of catalyst and PMS were 0.2 g L-1 and 1 mM, respectively, and had good degradation effects in the pH 5-11 range. Free radical quenching experiments, XPS, and electron paramagnetic resonance (EPR) analyses revealed the presence of hydroxyl radicals (˙OH), sulphate radicals (SO4˙-), singlet oxygen (1O2), and superoxide radicals (˙O2 -) in the CMFO-0.4/PMS system, with 1O2 being the main reactive oxygen species (ROS). In addition, CMFO-0.4 has good reusability and adaptability to the presence of other substances.

Elucidating doxycycline biotransformation mechanism by Chryseobacterium sp. WX1: Multi-omics insights

Doxycycline (DOX) represents a second-generation tetracycline antibiotic that persists as a challenging-to-degrade contaminant in environmental compartments. Despite its ubiquity, scant literature exists on bacteria proficient in DOX degradation. This study marked a substantial advancement in this field by isolating Chryseobacterium sp. WX1 from an activated sludge enrichment culture, showcasing its unprecedented ability to completely degrade 50 mg/L of DOX within 44 h. Throughout the degradation process, seven biotransformation products were identified, revealing a complex pathway that began with the hydroxylation of DOX, followed by a series of transformations. Employing an integrated multi-omics approach alongside in vitro heterologous expression assays, our study distinctly identified the tetX gene as a critical facilitator of DOX hydroxylation. Proteomic analyses further pinpointed the enzymes postulated to mediate the downstream modifications of DOX hydroxylation derivatives. The elucidated degradation pathway encompassed several key biological processes, such as the microbial transmembrane transport of DOX and its intermediates, the orchestration of enzyme synthesis for transformation, energy metabolism, and other gene-regulated biological directives. This study provides the first insight into the adaptive biotransformation strategies of Chryseobacterium under DOX-induced stress, highlighting the potential applications of this strain to augment DOX removal in wastewater treatment systems containing high concentrations of DOX.

Ball Milling of La2O3 Tailors the Crystal Structure, Reactive Oxygen Species, and Free Radical and Non-Free Radical Photocatalytic Pathways

Non-free radical photocatalysis with metal oxide catalysts is an important advanced oxidation process that enables the removal of various emerging environmental pollutants, such as tetracycline. Here, four hexagonal La2O3 photocatalysts with different densities of oxygen vacancy and crystalline features are synthesized and then further treated by ball milling. Ball milling of these La2O3 photocatalysts is found to increase the amount of oxygen vacancies on their surfaces and thereby the amount of 1O2 species produced by them. The photocatalytic degradation of TC by these La2O3 photocatalysts depends on the oxygen vacancies present on them. Furthermore, the ones with a strong (101) diffraction peak remove tetracycline from water systems largely with 1O2 and •OH species, whereas those with a weak (101) diffraction peak do so mainly via 1O2 and direct electron transfer (DET) process. Their overall catalytic properties are also studied by density functional theory calculations. Moreover, the organic products produced from tetracycline by La2O3 photocatalysts containing a strong (101) diffraction peak are found to be less toxic than those produced by La2O3 photocatalysts containing a weak (101) diffraction peak. This study also provides convincing evidence that the structures of La2O3 determine the species that is produced by it and that end up mediating photocatalytic reaction pathways (i.e., free radical versus non-free radical) to degrade an emerging environment pollutant.

An insight into the role of experimental parameters in advanced oxidation process applied for pharmaceutical degradation

The advanced oxidation process (AOP) is an efficient method to treat recalcitrance pollutants such as pharmaceutical compounds. The essential physicochemical factors in AOP experiments significantly influence the efficiency, speed, cost, and safety of byproducts of the treatment process. In this review, we collected recent articles that investigated the elimination of pharmaceutical compounds by various AOP systems in a water medium, and then we provide an overview of AOP systems, the formation mechanisms of active radicals or reactive oxygen species (ROS), and their detection methods. Then, we discussed the role of the main physicochemical parameters (pH, chemical interference, temperature, catalyst, pollutant concentration, and oxidant concentration) in a critical way. We gained insight into the most frequent scenarios for the proper and improper physicochemical parameters for the degradation of pharmaceutical compounds. Also, we mentioned the main factors that restrict the application of AOP systems in a commercial way. We demonstrated that a proper adjustment of AOP experimental parameters resulted in promoting the treatment performance, decreasing the treatment cost and the treatment operation time, increasing the safeness of the system products, and improving the reaction stoichiometric efficiency. The outcomes of this review will be beneficial for future AOP applicants to improve the pharmaceutical compound treatment by providing a deeper understanding of the role of the parameters. In addition, the proper application of physicochemical parameters in AOP systems acts to track the sustainable development goals (SDGs).

Peroxymonosulfate activation by walnut shell activated carbon supported nano zero-valent iron for the degradation of tetracycline: Performance, degradation pathway and mechanism

In this study, activated carbon (WS-AC) was prepared from walnut shell. Nano-zero-valent iron (nZVI) was loaded on walnut shell activated carbon by liquid phase reduction method and used as catalyst (WS-AC/nZVI) to activate peroxymonosulfate (PMS) to efficiently degrade tetracycline (TC) in solution. The composite material with a mass ratio of WS-AC to nZVI of 1:1 has the highest catalytic performance for activating PMS to degrade TC. The results showed that under the conditions of TC concentration of 100 ppm, PMS dosage of 0.2 mM and WS-AC/nZVI dosage of 0.1 g/L, the removal efficiency of TC could reach 81%. Based on quenching experiments and electron spin resonance (EPR), it was verified that •OH, SO4•- and 1O2 bound on the catalyst surface were the main reactive oxygen species during the reaction. The intermediate products of TC were identified by liquid chromatography-mass spectrometry (HPLC-MS) and DFT calculation, and the possible degradation pathway of TC was proposed. The catalyst still maintained high removal efficiency of TC after four cycles of experiments, and the minimal iron loss on the surface of the catalyst indicated that it had good stability. The efficient and stable WS-AC/nZVI activated PMS showed great potential in the degradation of antibiotics.

In situ generated iron oxide nanosheet on iron foam electrode for enhanced electro-Fenton performance toward pharmaceutical wastewater treatment

Electro-Fenton (EF) is considered to be an effective technology for the purification of organic wastewater containing antibiotics, but the construction of accessible and efficient heterogeneous EF catalytic materials still faces challenges. In this study, an iron foam-derived electrode (FeOx/if-400) was prepared by a simple method (chemical oxidation combined heat treatment). The fabricated electrode presented great EF degradation efficiency under wide pH range (almost completely removing 50 mg L-1 TNZ within 60 min) and maintained great stability after consecutive operation (>95% removal after six cycles). Also, the FeOx/if-400 electrode showed good purification ability for pharmaceutical wastewater as evaluated by the quadrupole time-of-flight mass spectrometry and the three-dimensional excitation-emission matrix fluorescence spectroscopy. Based on experimental results, characterization analysis, and density functional theory (DFT) calculations, the EF reaction mechanism of FeOx/if-400 electrode and the organics degradation pathways in simulated and real matrices were proposed. Significantly, the biotoxicity assessment of the degradation intermediate products was revealed by ECOSAR software and relative inhibition of E. coli, which fully proved the environmental friendliness of the EF process by the FeOx/if-400 cathode. This work provides a green and effective EF system, showing a promising application potential in the field of organic wastewater treatment containing antibiotic contaminants.

Antibiotic removal from synthetic and real aqueous matrices by peroxymonosulfate-based advanced oxidation processes. A review of recent development

The widespread use of antibiotics for the treatment of bacteriological diseases causes their accumulation at low concentrations in natural waters. This gives health risks to animals and humans since it can increase the damage of the beneficial bacteria, the control of infectious diseases, and the resistance to bacterial infection. Potent oxidation methods are required to remove these pollutants from water because of their inefficient abatement in municipal wastewater treatment plants. Over the last three years in the period 2021-September 2023, powerful peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) have been developed to guaranty the effective removal of antibiotics in synthetic and real waters and wastewater. This review presents a comprehensive analysis of the different procedures proposed to activate PMS-producing strong oxidizing agents like sulfate radical (SO4•-), hydroxyl radical (•OH, radical superoxide ion (O2•-), and non-radical singlet oxygen (1O2) at different proportions depending on the experimental conditions. Iron, non-iron transition metals, biochar, and carbonaceous materials catalytic, UVC, photocatalytic, thermal, electrochemical, and other processes for PMS activation are summarized. The fundamentals and characteristics of these procedures are detailed remarking on their oxidation power to remove antibiotics, the influence of operating variables, the production and detection of radical and non-radical oxidizing agents, the effect of added inorganic anions, natural organic matter, and aqueous matrix, and the identification of by-products formed. Finally, the theoretical and experimental analysis of the change of solution toxicity during the PMS-based AOPs are described.

Highly dispersed Fe7S8 anchored on sp2/sp3 hybridized carbon boosting peroxymonosulfate activation for enhanced EOCs elimination though singlet oxygen-dominated nonradical pathway

The synergistic effect of carbon materials with high sp2/sp3 hybridized carbon ratio and metal materials can enhance the efficiency of peroxymonosulfate (PMS) based advanced oxidation processes. In this study, a composite of highly dispersed Fe7S8 anchored on sp2/sp3 hybridized carbon (Fe7S8@HC) was developed by a facile synthesis for PMS activation. Within 10 min, the removal efficiency of the target pollutant doxycycline (DOX) could reach ca. 96 % in optimal Fe7S8@HC/PMS system through a 1O2-dominated non-radical pathway. Correlation mechanism analysis revealed that thiophene S, sp2/sp3 ratio and Fe(II) were critical factors for elongating of the O-O bond of PMS. Moreover, the Fe7S8@HC/PMS system exhibited favorable adaptability to interference such as common inorganic anions, humic acid and pH changes and could effectively remove various organic pollutants with low ionization potential. Moreover, the system maintained high DOX removal efficiency by running 30 cycles in a continuous flow reactor. Finally, susceptible sites of DOX and four degradation pathways were proposed by density functional theory calculation and LC-MS detection. This work not only offered new insights into the design of high-performance catalysts combining metal and biomass-based carbon materials, but also provided technical support for the remediation of water bodies containing emerging organic contaminants.

Structure of a novel Co-based heterogeneous catalyst via Mn3(PO4)2 as a carrier to efficiently activate peroxymonosulfate for improving degradation of sulfonamides

Effective degradation of sulfonamides (SAs) in water is of global importance for decreasing its pathogenicity and bioaccumulation. In this study, Mn₃(PO₄)₂ was used as a carrier to fabricate a novel and high-efficient catalyst with Co₃O₄ anchored (Co₃O₄@Mn₃(PO₄)₂) for the activation of peroxymonosulfate (PMS) to degrade SAs. Surprisingly, the catalyst exhibited superior performance, and nearly 100% of SAs (10 mg L^-1) including sulfamethazine (SMZ), sulfadimethoxine (SDM), sulfamethoxazole (SMX), and sulfisoxazole (SIZ) was degraded by Co₃O₄@Mn₃(PO₄)₂-activated PMS within 10 min. A series of characterization of the Co₃O₄@Mn₃(PO₄)₂ composite were conducted and the main operational parameters of SMZ degradation were investigated. SO₄^•-, •OH, and ¹O₂ were determined to be the dominating reactive oxygen species (ROS) responsible for the degradation of SMZ. Co₃O₄@Mn₃(PO₄)₂ also exhibited excellent stability and the removal rate of SMZ still maintained over 99% even in the fifth cycle. The plausible pathways and mechanisms of SMZ degradation in the system of Co₃O₄@Mn₃(PO₄)₂/PMS were deduced on the basis of the analyses of LCMS/MS and XPS. This is the first report on high-efficient heterogeneous activating PMS by mooring Co₃O₄ on Mn₃(PO₄)₂ to degrade SAs, which provides us with a strategy to structure novel bimetallic catalysts for PMS activation.

Fulvic acid enhanced peroxymonosulfate activation over Co-Fe binary metals for efficient degradation of emerging bisphenols

Bisphenol F (BPF) and bisphenol S (BPS) are emerging bisphenols, which have become the main substitutes for bisphenol A (BPA) in industrial production and are also considered as new environmental pollution challenges. Thus, the necessity for an effective approach to remove BPF and BPS is essential. In this study, fulvic acid (FA) was used to modify Co-Fe binary metals (CFO) for peroxymonosulfate (PMS) activation. The characterization results demonstrated that CFO changed significantly in morphology after compounding with FA, with smaller particle size and 5.6 times larger specific surface area, greatly increasing the active sites of catalyst; Moreover, humic acid-like compounds increased the surface functional groups of CFO, especially phenolic hydroxyl, which could effectively prolong the PMS activation. The concentration of all reactive species, such as SO₄•^-, •OH, O₂•^-, and ¹O₂ increased in FA@CFO/PMS system. As a result, the degradation efficiency of CFO for both BPF and BPS was significantly improved after compounding FA, which also had a wide range of pH applications. The degradation pathways of both BPF and BPS were proposed based on liquid chromatography-mass spectrometry (LC-MS) analysis and the density functional theory (DFT) calculations. Our findings are expected to provide new strategies and methods for remediation of environmental pollution caused by emerging bisphenols.

Novel construction of the catalyst from red mud by the pyrolysis reduction of glucose for the peroxymonosulfate-induced degradation of m-cresol

Red mud of low cost is regarded as a promising alternative to heterogeneous catalysts for activating peroxymonosulfate (PMS) to degrade m-cresol. Improper valence states of metal oxides and coated active substances in red mud greatly hampered its wide application. To solve this problem, the modified red mud (WRMG/700) was prepared by the pyrolysis reduction of glucose in N₂ atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectrum (XPS) analysis confirmed the production of Fe₃O₄, MnO and NiO in red mud and their gathering on the surface of particles. WRMG/700 exhibited the excellent performance toward PMS activation for the m-cresol degradation with 99.02% degradation efficiency and a pH-independent catalytic activity between initial pH 3-8. The removal efficiency of COD increased with the reaction time under the optimized degradation conditions. The free radical scavenging experiments and electron paramagnetic resonance (EPR) test confirmed ¹O₂ played a dominant role during m-cresol degradation in the WRMG/700/PMS system, implying m-cresol degradation was a non-radical oxidation process. Accordingly, the possible reaction mechanism was proposed. WRMG/700 retained its activation performance even after five recycles. This study showed a low cost and simple operation process for m-cresol elimination.

A review on the degradation of acetaminophen by advanced oxidation process: pathway, by-products, biotoxicity, and density functional theory calculation

Water scarcity and the accumulation of recalcitrance compounds into the environment are the main reasons behind the attraction of researchers to use advanced oxidation processes (AOPs). Many AOP systems have been used to treat acetaminophen (ACT) from an aqueous medium, which leads to generating different kinetics, mechanisms, and by-products. In this work, state-of-the-art studies on ACT by-products and their biotoxicity, as well as proposed degradation pathways, have been collected, organized, and summarized. In addition, the Fukui function was used for predicting the most reactive sites in the ACT molecule. The most frequently detected by-products in this review were hydroquinone, 1,4-benzoquinone, 4-aminophenol, acetamide, oxalic acid, formic acid, acetic acid, 1,2,4-trihydroxy benzene, and maleic acid. Both the experimental and prediction tests revealed that N-(3,4-dihydroxy phenyl) acetamide was mutagenic. Meanwhile, N-(2,4-dihydroxy phenyl) acetamide and malonic acid were only found to be mutagenic in the prediction test. The findings of the LC50 (96 h) test revealed that benzaldehyde is the most toxic ACT by-products and hydroquinone, N-(3,4-dihydroxyphenyl)formamide, 4-methylbenzene-1,2-diol, benzoquinone, 4-aminophenol, benzoic acid, 1,2,4-trihydroxybenzene, 4-nitrophenol, and 4-aminobenzene-1,2-diol considered harmful. The release of them into the environment without treatment may threaten the ecosystem. The degradation pathway based on the computational method was matched with the majority of ACT proposed pathways and with the most frequent ACT by-products. This study may contribute to enhance the degradation of ACT by AOP systems.

Sulfur vacancies on MoS2 enhanced the activation of peroxymonosulfate through the co-existence of radical and non-radical pathways to degrade organic pollutants in wastewater

The enhancement of vacancies in catalysts involving Fenton-like reactions is a promising way to remove organic pollutants in wastewater, but sulfur vacancies are rarely involved. In this work, MoS₂ containing defect sites were synthesized by a simple high-temperature treatment and then applied for activating peroxymonosulfate to eliminate organic pollutants in wastewater. The structure was characterized by several techniques such as XRD, BET, and XPS. Important influencing factors were systemically investigated. The results indicated that MoS₂ with sulfur vacancies possessed a higher catalytic activity than that of the parent MoS₂. The annealing temperature of the catalyst had a great effect on the removal of organic pollutants. Besides, the catalytic system had a wide pH range. Quenching and electron paramagnetic resonance (EPR) experiments indicated that the reaction system contained radical and non-radical species. The characterization results revealed that the defect sites in catalysts mainly strengthened the activity of catalysts. This study offers a new heterogeneous catalyst for the removal of organic pollutants via the peroxymonosulfate-based Fenton-like reactions.

Sulfur vacancies on MoS2 enhanced the activation of peroxymonosulfate to remove organic pollutants in wastewater.