Kelp-derived N-doped biochar activated peroxymonosulfate for ofloxacin degradation

Efficient degradation of tetracycline via peroxymonosulfate activation by phosphorus-doped biochar loaded with cobalt nanoparticles

The accumulation of tetracycline hydrochloride (TCH) threatens human health because of its potential biological toxicity. Carbon -based materials with easy isolation and excellent performance that can activate peroxymonosulfate (PMS) to generate reactive oxygen species for TCH degradation are essential, but the development of such materials remains a significant challenge. In this study, based on the idea of treating waste, tricobalt tetraoxide loaded P-doped biochar (Co NP-PBC) was synthesised to activate PMS for the degradation of TCH. Possible degradation pathways and intermediate products of TCH were identified using High performance liquid chromatography tandem mass spectrometry (HPLC-MS) detection and density functional theory analysis. Toxicity analysis software was used to predict the toxicity of the intermediate products. Compared to catalysts loaded with Fe and Mn and other Co-based catalysts, Co NP-PBC exhibited an optimal performance (with a kinetic constant of 0.157 min-1 for TCH degradation), and over 99.0% of TCH can be degraded within 20 min. This mechanism demonstrates that the non-free radical oxidation of 1O2 plays a major role in the degradation of TCH. This study provides insights into the purification of wastewater using BC-based catalysts.

Research advances on production and application of algal biochar in environmental remediation

Algae, comprising microalgae and macroalgae, have emerged as a promising feedstock for the production of functional biochar. Recently, the application of algal biochar in environmental remediation gains increasing attention. This review summarizes research advancements in the synthesis and application of algal biochar, a versatile and sustainable material for environmental remediation ranging from wastewater treatment to soil improvement. Algal biochar can be prepared by pyrolysis, microwave-assisted pyrolysis, and hydrothermal carbonization. Physical and chemical modifications have proven to be effective for improving biochar properties. Algal biochar is promising for removing diverse pollutants including heavy metals, organic pollutants, and microplastics. The role in soil improvement signifies a sustainable approach to enhancing soil structure, nutrient retention, and microbial activity. Research gaps are identified based on current understanding, necessitating further exploration into variations in biochar characteristics, the performance improvement, large-scale applications, and the long-term evaluation for environmental application. This review provides a better understanding of algal biochar as a sustainable and effective tool in environmental remediation.

Enhanced activation of peroxymonosulfate for advanced oxidation processes using solid waste: A novel and easy implement high-value utilization process of slag

A simple, efficient and low energy-consuming process available to generate resultful radicals from PMS for organic pollutants removal had been employed in this study. Slag had been used as the activator for organic pollutants degradation under slag/PMS advanced oxidation process. In this work, effects of slag with or without pretreatment on pollutant removal were studied and radical species generated by slag were measured. Calcination pretreatment is one efficient method to enhance the degradation efficiency significantly. Due to Fe3O4 and Fe2O3 became the dominant phases after calcination, it was about 8.6-flods increasing after comparing the pollutant removal efficiency for different slag/PMS system with calcination pretreatment or not. Organic pollutant neither degraded in PMS system at 25 °C nor being absorbed by slag system for 60 min. On the contrary, up to 90% pollutant concentration reduction achieved in the slag/PMS process. During this process, both •OH and SO4•- had been detected once slag and PMS interaction in wastewater. Through the free radicals quenching tests,•OH should be the key free radical in this advanced oxidation process for the organic pollutant removal under this alkaline condition. In general, organic degradation rate was determined by the slag dosage, and the maximum degradation efficiency was mainly controlled by the PMS usage. This work is expected to broaden the high-value reutilization way for industrial solid waste.

A critical review of sustainable application of biochar for green remediation: Research uncertainty and future directions

Biochar, a carbon-rich material produced from the pyrolysis of organic biomass, has gained significant attention as a potential solution for sustainable green remediation practices. Several studies analyze biomass-derived biochar techniques and environmental applications, but comprehensive assessments of biochar limitations, uncertainty, and future research directions still need to be improved. This critical review aims to present a comprehensive analysis of biochar's efficacy in environmental applications, including soil, water, and air, by sequentially addressing its preparation, application, and associated challenges. The review begins by delving into the diverse methods of biochar production, highlighting their influence on physical and chemical properties. This review explores the diverse applications of biochar in remediating contaminated soil, water, and air while emphasizing its sustainability and eco-friendly characteristics. The focus is on incorporating biochar as a remediation technique for pollutant removal, sequestration, and soil improvement. The review highlights the promising results obtained from laboratory-scale experiments, field trials, and case studies, showcasing the effectiveness of biochar in mitigating contaminants and restoring ecosystems. The environmental benefits and challenges of biochar production, characterization, and application techniques are critically discussed. The potential synergistic effects of combining biochar with other remediation methods are also explored to enhance its efficacy. A rigorous analysis of the benefits and drawbacks of biochar for diverse environmental applications in terms of technical, environmental, economic, and social issues is required to support the commercialization of biochar for large-scale uses. Finally, future research directions and recommendations are presented to facilitate the development and implementation of biochar-based, sustainable green remediation strategies.

Iron/nitrogen co-doped biochar derived from salvaged cyanobacterial for efficient peroxymonosulfate activation and ofloxacin degradation: Synergistic effect of Fe/N in non-radical path

A green, low-cost, high-performance Fe/N co-doped biochar material (Fe-N@C) was synthesized using salvaged cyanobacteria without other extra precursors for peroxymonosulfate (PMS) activation and ofloxacin (OFX) degradation. With the increased pyrolysis temperature, the graphitization degree, the specific surface area and the corresponding groups like OH, COO etc. for Fe-N@C tended to increase, resulting in a greater OFX adsorption. However, the total amount of Fe-NX and graphitic nitrogen groups in the Fe-N@C composites was firstly increased and then decreased, which reached the highest at 800 °C (Fe-N@C-800). All these changes of functional species ascribed to the strong interaction between Fe, N and C led to the highest defect degree of Fe-N@C-800, resulting the highest OFX removal efficiency of 95.0 %. OFX removal experiments indicated the adsorption process promoted the total OFX degradation for different functional groups on Fe-N@C composites separately dominated the process of OFX adsorption and PMS catalysis. Radical quenching and electron paramagnetic resonance (EPR) measurements proved free radical and non-free radical pathways participated in Fe-N@C/PMS system. The non-free radicals based on 1O2 and high-valent iron-oxo species played a more important role in OFX degradation, leading to the minimal effect of co-existing anions and the high universality for other antibiotic pollutants. Fe-NX was utilized as the main catalytic sites and graphitic nitrogen contributed more to the electron transfer for PMS activation, whose synergistic effect efficiently facilitated OFX degradation. Finally, the possible degradation route of OFX in the Fe-N@C-800/PMS system was proposed. All these results will provide the new insights into the intrinsic mechanism of Fe/N species in carbon-based materials for PMS activation.

The magic of algae-based biochar: advantages, preparation, and applications

Compared with other biomass sources, the use of algae as a raw material to prepare biochar (BC) has important advantages including safety, high yield and economy. The protein content of algae cells is as high as 3.2 mg DCW/L, and the graphitic-N and N-O functional groups generated by the pyrolysis of proteins could effectively activate free radicals. Combined with the generated pore structure, the electron transfer/exchange capability was enhanced, which is conducive to improving its catalytic performance. Algae as a natural N source, the manuscript analyzed the surface properties and physicochemical properties of algae-based BC, and investigated its degradation effect on organic/inorganic pollutants in wastewater. Subsequently, the effect of nitrogen-doped BC on the adsorption/catalysis capacity was discussed. Finally, the directed preparation of algae-based BC applied in different scenarios was summarized. Algae-based BC has the property of N doping, which broadens its application efficiency in the environmental field. Overall, this manuscript reviews how to achieve efficient utilization of algae-based BC in wastewater.

Highly-efficient degradation of organic pollutants by oxalic acid modified sludge biochar: Mechanism and pathways

The application of sludge biochar (SC) materials as efficient catalysts for organic pollutants mineralization via advanced oxidation process meets the good strategy of "make waste profitable". The catalytic oxidations of methyl orange (MO) and pyrene by oxalic acid modified sludge biochar (SC-OA) with and without H₂O₂ were carried out. The analysis of Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), electronic paramagnetic resonance spectrometer (EPR) and free radical quenching experiment were performed and the definite relationships between persistent free radicals (PFRs) type and specific reactive oxygen species (ROS) were made clear. It is suggested for the first time that carbon-centered type PFRs in SC-OA without H₂O₂ could form O₂•^- and •OH from COOH groups, while oxygen-centered type PFRs induced H₂O₂ to produce •OH. The degradation intermediates of MO and pyrene were identified and the transformation pathways were proposed. SC-OA, possessing good sustainable utilization and clean catalytic property, is expected to be popularized and applied in the mineralization of organic pollutants, especially in the in-situ remediation of contaminated soil where is no continuous supply of H₂O₂.

Dual redox cycles of Mn(Ⅱ)/Mn(III) and Mn(III)/Mn(IV) on porous Mn/N co-doped biochar surfaces for promoting peroxymonosulfate activation and ciprofloxacin degradation

Mn and N co-doped biochar (Mn-N-TS) was prepared as an effective catalyst to activate peroxymonosulfate (PMS) for ciprofloxacin (CIP) degradation. As opposed to Mn-TS and N-TS, Mn-N-TS had more active sites containing N and Mn, as well as a greater specific surface area (923.733 m² g^-1). The Mn-N-TS exhibited excellent PMS activation ability. In the Mn-N-TS/PMS system, the CIP removal efficiency was 91.9% in 120 min. Mn and N co-doping could accelerate electron transfer between CIP and PMS molecules. Simultaneously, defect sites, graphitic N, pyridinic N, C═O groups, and Mn(II)/Mn(III)/Mn(IV) redox cycles acted as active sites to activate PMS and generate free radicals (OH, SO₄^- and ¹O₂). Furthermore, the Mn-N-TS/PMS system could effectively degrade CIP in a wide pH range, background substances, and actual water. Finally, a probable mechanism of PMS activation by Mn-N-TS was proposed. In conclusion, this work gave a novel direction for the rational design of Mn and N co-doped biochar.

Enhanced persulfate activation by nitrogen-doped mesoporous carbon for efficiently degrading organic matters

Nitrogen-doped carbon materials (NMC) are widely used in peroxymonosulfate-based advanced oxidation processes (PMS-AOPs). Despite great efforts to improve the specific surface area of and the content of N atoms in catalysts for enhancing catalytic performance, this does not mean that the catalytic performance will improve with the increasing specific surface area and nitrogen content. Therefore, it is the key to optimize pore structure of NMC for maximizing the catalytic performance of nitrogen active sites. Herein, we synthesized the NMC as an efficient catalyst to activate PMS for the phenol removal. It can be found that the mesopore structure significantly accelerated the diffusion of reactants and might build the spatial confinement effect to improve the utilization of short life free radicals for further improving the removal efficiency. The removal efficiency of 1NMC750 (95%) with abundant mesopore channels was much higher than that of 1NMC750-0F127 (20%) with abundant micropore channels. Furthermore, the mechanism was confirmed to be radical (SO₄^•-, •OH) and non-radical (¹O₂, electron transfer) pathways. This study proposed a new insight for improving the catalytic performance of carbon materials by coordinating the pore structure.

Catalytic ozonation for imazapic degradation over kelp-derived biochar: Promotional role of N- and S-based active sites

It is a feasible strategy to prepare reliable biochar catalysts for heterogeneous catalytic ozonation (HCO) processes by using inexpensive, high quality, and easily available raw materials. Here, an environmentally friendly, simple, and green biochar catalyst rich in nitrogen (N) and sulfur (S) has been prepared by the pyrolysis of kelp. Compared with directly carbonized kelp biomass (KB), acid-activated KB (KBA) and base-activated KB (KBB) have higher specific surface areas and more extensive porous structures, although only KBB displays effective ozone activation. Imazapic (IMZC), a refractory organic herbicide, was chosen as the target pollutant, which has apparently not hitherto been investigated in the HCO process. Second-order rate constants (k) for the reactions of IMZC with three different reactive oxygen species (ROS), specifically kO3, IMZC, kOH, IMZC, and k1O2, IMZC, have been determined as 0.974, 2.48 × 109, and 6.23 × 105 M-1 s-1, respectively. The amounts of graphitic N and thiophene S derived from the intrinsic N and S showed good correlations with the IMZC degradation rate, implicating them as the main active sites. OH and O2- and 1O2 were identified as main ROS in heterogeneous catalytic ozonation system for IMZC degradation. This study exemplified the utilization of endogenous N and S in biological carbon, and provided more options for the application of advanced oxidation processes and the development of marine resources.

Efficient degradation of sulfamethoxazole in various waters with peroxymonosulfate activated by magnetic-modified sludge biochar: Surface-bound radical mechanism

First time, this study synthesized a magnetic-modified sludge biochar (MSBC) as an activator of peroxymonosulfate (PMS) to eliminate sulfamethoxazole (SMX). The removal efficiency of SMX reached 96.1% at t = 60 min by PMS/MSBC system. The larger surface area and magnetic Fe₃O₄ of MSBC surface enhanced its activation performance for PMS. The PMS decomposition, premixing and reactive oxygen species (ROS) identification experiments combined with Raman spectra analysis demonstrated that the degradation process was dominated by surface-bound radicals. The transformed products (TPs) of SMX and the main degradation pathways were identified and proposed. The ecotoxicity of all TPs was lower than that of SMX. The magnetic performance was beneficial for its reuse and the removal efficiency of SMX was 83.3% even after five reuse cycles. Solution pH, HCO₃^- and CO₃^2- were the critical environmental factors affecting the degradation process. MSBC exhibited environmental safety for its low heavy metal leaching. PMS/MSBC system also performed excellent removal performance for SMX in real waters including drinking water (88.1%), lake water (84.3%), Yangtze River water (83.0%) and sewage effluent (70.2%). This study developed an efficient PMS activator for SMX degradation in various waters and provided a workable way to reuse and recycle municipal sludge.

In situ preparation of highly graphitized N-doped biochar geopolymer composites for efficient catalytic degradation of tetracycline in water by H2O2

Advanced oxidation processes (AOPs) hold great prospects for the treatment of antibiotic wastewater. N-doped biochar (NB) has received increasing attention as a catalyst for AOPs because of its green nature, abundant biomass resources, and low cost. However, NB catalysts are complicated to prepare and difficult to recover, limiting their practical application. In this study, an N-doped biochar geopolymer composite (NBGC) was synthesized via in situ doping, simultaneous carbonization, and activation (ISCA) of lignin and urea in the porous geopolymer flake, without additional activators. The ISCA process used a low-cost geopolymer flake that not only served as a carrier to immobilize NB and facilitate the recovery, but also applied its inherent strong alkalinity to activate NB. The composite catalyst obtained at 600 °C (NBGC-600) exhibited excellent activity in activating H₂O₂ to degrade tetracycline (∼100%, 50 mg/L). The EPR results indicated that NBGC-600 had a strong ability to activate and decompose H₂O₂ to •OH, which could be attributed to its rich persistent radicals, graphitized N and CO groups, as well as the high degree of graphitization of biochar. The degradation pathway and intermediates of tetracycline in the NBGC-600-H₂O₂ system were also discussed according to the HPLC-MS results. Moreover, NBGC-600 had excellent reusability and showed great potential for continuous treatment of tetracycline in water. This work paves a new way for the synthesis of cost-effective N-doped biochar composite catalysts for AOPs.

Ofloxacin Degradation over Nanosized Fe3O4 Catalyst viaThermal Activation of Persulfate Ions

In this work, an Fe3O4 catalyst was synthetized in a single step via electrochemical synthesis. The Fe3O4 catalyst was used to evaluate the degradation of Ofloxacin (OFX) using a heterogeneous advanced oxidation process with sodium persulfate (PS). PS activation was successfully achieved via thermal conventional heating directly and subsequently applied for the degradation of OFX. The degradation kinetics were studied under different conditions, such as catalyst and oxidant concentration and temperature. The results show that a higher reaction temperature, catalyst and initial PS dose strongly influence the degradation efficiency. Thermal activation of persulfate was tested at 20, 40 and 60 °C. At 60 °C, the half-time of OFX was 23 times greater than at 20 °C, confirming the activation of persulfate. Mineralization studies also showed that under optimized conditions (20 mM of persulfate, 1 g/L catalyst and 100 mg/L OFX), a 66% reduction in organic matter was observed, in contrast to that obtained at 40 °C and 20 °C, which was null. The reusability, as tested through the fourth reuse cycle, resulted in a 38% reduced degradation efficiency when comparing the first and last cycle. Furthermore, the electrosynthesized catalyst presented similar degradation efficiencies in both real water and MilliQ, mainly because of the Cl2− generation at high Cl− concentrations that takes place in Cl− contaminated water.

A Review of Persulfate Activation by Magnetic Catalysts to Degrade Organic Contaminants: Mechanisms and Applications

All kinds of refractory organic pollutants in environmental water pose a serious threat to human health and ecosystems. In recent decades, sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted extensive attention in the removal of these organic pollutants due to their high redox potential and unique selectivity. This review first introduces persulfate activation by magnetic catalysts to degrade organic contaminants. We present the advances and classifications in the generation of sulfate radicals using magnetic catalysts. Subsequently, the degradation mechanisms in magnetic catalysts activated persulfate system are summarized and discussed. After an integrated presentation of magnetic catalysts in SR-AOPs, we discuss the application of persulfate activation by magnetic catalysts in the treatment of wastewater, landfill leachate, biological waste sludge, and soil containing organic pollutants. Finally, the current challenges and perspectives of magnetic catalysts that activated persulfate systems are summarized and put forward.

Biochar raw material selection and application in the food chain: A review

As one of the largest carbon emitters, China promises to achieve carbon emissions neutrality by 2060. Various industries are developing businesses to reduce carbon emissions. As an important greenhouse gas emissions scenario, the reduction of carbon emissions in the food chain can be achieved by preparing the wastes into biochar. The food chain, as one of the sources of biochar, consists of production, processing and consumption, in which many wastes can be transferred into biochar. However, few studies use the food chain as the system to sort out the raw materials of biochar. A systematic review of the food chain application in serving as raw materials for biochar is helpful for further application of such technique, providing supportive information for the development of biochar preparation and wastes treating. In addition, there are many pollution sources in the food production process, such as agricultural contaminated soil and wastewater from livestock and aquatic, that can be treated on-site to achieve the goal of treating wastes with wastes within the food chain. This study focuses on waste resource utilization and pollution remediation in the food chain, summarizing the sources of biochar in the food chain and analyzing the feasibility of using waste in food chain to treat contaminated sites in the food chain and discussing the impacts of the greenhouse gas emissions. This review provides a reference for the resource utilization of waste and pollution reduction in the food chain.

Efficacy and Safety of Endoscopic Tympanic Membrane Catheterization Plus Ofloxacin Ear Drops in the Treatment of Secretory Otitis Media in Infants and Toddlers

Objective

To investigate the efficacy and safety of endoscopic tympanic membrane catheterization and ofloxacin ear drops in the treatment of secretory otitis media in infants and toddlers.

Methods

A total of 80 children suffering from secretory otitis media who underwent treatment in our hospital from July 2018 to April 2020 were divided into the control group (n = 40) and experimental group (n = 40) by randomization. The control group was treated with endoscopic tympanic membrane catheterization alone, while the experimental group was treated with ofloxacin ear drops based on the same treatment as the control group. The treatment effect, air conduction hearing level, clearance rate of pathogenic bacteria secreted by the ear canal, recurrence rate, and adverse reactions were compared between the two groups.

Results

The treatment in the experimental group led to a significantly better outcome than that in the control group (P < 0.05). After treatment, a substantially improved air conduction hearing level in the experimental group was observed (P < 0.001). A chi-square test showed a significantly higher clearance rate of pathogenic bacteria secreted from the ear canal of the children in the experimental group compared to that of the control group (P < 0.05). The treatment in the experimental group resulted in a lower recurrence rate and adverse reaction rate as compared to the control group (P < 0.05).

Conclusion

Concurrent endoscopic tympanic membrane catheterization and ofloxacin ear drops showed excellent efficacy in the treatment of secretory otitis media in infants and toddlers. The therapy offers promising solutions for the improvement of hearing level, increase of clearance rate of pathogenic bacteria secreted from the ear canal, and decrease of disease recurrence and adverse reactions during treatment.

Synthetic organic antibiotics residues as emerging contaminants waste-to-resources processing for a circular economy in China: Challenges and perspective

Synthetic antibiotics have been known for years to combat bacterial antibiotics. But their overuse and resistance have become a concern recently. The antibiotics reach the environment, including soil from the manufacturing process and undigested excretion by cattle and humans. It leads to overburden and contamination of the environment. These organic antibiotics remain in the environment for a very long period. During this period, antibiotics come in contact with various flora and fauna. The ill manufacturing practices and inadequate wastewater treatment cause a severe problem to the water bodies. After pretreatment from pharmaceutical industries, the effluents are released to the water bodies such as rivers. Even after pretreatment, effluents contain a significant number of antibiotic residues, which affect the living organisms living in the water bodies. Ultimately, river contaminated water reaches the ocean, spreading the contamination to a vast environment. This review paper discusses the impact of synthetic organic contamination on the environment and its hazardous effect on health. In addition, it analyzes and suggests the biotechnological strategies to tackle organic antibiotic residue proliferation. Moreover, the degradation of organic antibiotic residues by biocatalyst and biochar is analyzed. The circular economy approach for waste-to-resource technology for organic antibiotic residue in China is analyzed for a sustainable solution. Overall, the significant challenges related to synthetic antibiotic residues and future aspects are analyzed in this review paper.

Effect of pyrolysis temperature on the activated permonosulfate degradation of antibiotics in nitrogen and sulfur-doping biochar: Key role of environmentally persistent free radicals

Because of the increasingly widespread contamination of antibiotics, the preparation of biochar by heteroatom doping to further improve the catalytic degradation efficiency of antibiotics has become a major focus of research. In this study, N-doped (NBC), S-doped (SBC), and NS-doped (NSBC) moso bamboo biochar were obtained at preparation temperatures of 300-700 °C. The concentration of environmentally persistent free radicals (EPFRs) in all biochars peaked when the preparation temperature was 500 °C: 2.45 × 10¹⁹ spins·g^-1 (BC), 9.23 × 10¹⁹ spins·g^-1 (NBC), 6.10 × 10¹⁹ spins·g^-1 (SBC), and 4.36 × 10¹⁹ spins·g^-1 (NSBC). After heteroatom doping, EPFR species were more abundant, and the distribution of three types of EPFRs (oxygen-centered (g > 2.0040), carbon-centered (g < 2.0030), and carbon-centered radicals with oxygen atom free radicals (2.0030 < g < 2.0040) varied with the preparation temperature. In the process of antibiotic degradation, both NBC and SBC increased the degradation rate of antibiotics, whereas NSBC reduced the degradation rate. Compared with the degradation rate of antibiotics of biochar (79.86%), the degradation rate of antibiotics by NBC, SBC, and NSBC via PMS activation was 92.23%, 88.86%, and 70.97% on average in 30 min, respectively. The greatest contributors to the catalytic degradation were SO₄^•-, followed by ¹O₂, •OH, and O₂^•-. EPFRs and ¹O₂ might be the main contributors to the free radical and non-free radical pathways. The enhancement of EPFRs following the N doping or S doping of biochar is the key factor underlying PMS activation. Therefore, changes in the structure of biochar can better activate PMS to produce reactive oxygen species-degrading antibiotics. The mineralization rate of antibiotics by BC, NBC, SBC, and NSBC was 42.12%, 47.06%, 44.99%, and 39.01%, respectively. This means that a small portion of the antibiotics was completely decomposed into CO₂, H₂O, and inorganic substances after degradation. Cyclic experiments showed that heteroatom-doped biochar had higher reusability, and the degradation rate decreased less than 15%.

Application fields of kitchen waste biochar and its prospects as catalytic material: A review

In China, a large amount of kitchen waste (KW) is generated each year, and the resource utilisation of the KW has become a problem. KW has a high carbon content and can be used as a raw material for biochar. Kitchen waste biochar (KWB) can be used to prepare adsorption materials, soil amendments, energy materials, carbon quantum dots, and electrode materials. However, few studies have used KWB as a raw material for catalytic materials. The application of sulfur (S) and nitrogen (N) doped biochar in the field of catalysis has proved effective and feasible. KWB contained a certain mass percentage of N and S elements, which has good application potential for use in the field of catalysis by KWB. In the process of preparing KWB by KW, keeping S and N as much as possible and converting them into pyridine N and thiophene S benefit the application of catalysis. This review provides a reference for the future application of KWB in China.

Identification and manipulation of active centers on perovskites to enhance catalysis of peroxymonosulfate for degradation of emerging pollutants in water

Perovskites (the general formula of ABO₃) with versatile substrates can serve as desirable catalysts to initiate advanced oxidation processes (AOPs) for environmental remediation. However, the knowledge regarding the active centers remains piecemeal and unclear, such as how the redox metal centers of B site, inert metals of A site, oxygen vacancies, and direct oxidation of catalysts govern the chemical degradation of aqueous pollutants. This study aimed to identify principal alternations in physicochemical and electrical properties of ABO₃-based perovskites modified with partial/overall substitution at A/B sites and synthesized at different conditions. In order to probe varied catalytic activity of these catalysts, ofloxacin (OFX) was used as a model micro-pollutant. Results showed that the OFX degradation by activation of peroxymonosulfate (PMS) with LaFeO₃ perovskite was favored by the Sr substitution at A site, Cu substitution at B site, and increasing calcination temperature. Evolution of ¹O₂, ^•OH and SO₄^•- have proven for efficient OFX oxidation, as evidenced by results from in-situ electron paramagnetic resonance (EPR) analyses and quenching tests. Specifically, the introduction of Sr at A site can facilitate PMS self-decomposition to produce more ¹O₂ due to the increased abundance of surface oxygen vacancies. In contrast, the Cu substitution at B site improved the surface oxygen vacancies, as well as the electrical conductivity, which can further accelerate ^•OH and SO₄^•- generation for the OFX degradation. This study provides deeper insights into the underlying mechanisms governing the catalytic activity of perovskites. These findings build a basis for better decontamination of hazardous environmental organic pollutants.

Resolving the Tribo-catalytic reaction mechanism for biochar regulated Zinc Oxide and its application in protein transformation

The utilization of mechanical energy to control water pollutants under dark conditions is currently a point of study focus. Herein, biochar -zinc oxide (BC-ZnO) composites with various structures were synthesized by co-pyrolysis of cotton and ZnO at different temperature and used for tribo-catalytic reaction. The introduction of BC can improve charge transmission and separation efficiency. Ultraviolet photoelectron spectra (UPS) and density functional theory (DFT) calculation prove the addition of BC can reduce work function of ZnO, and enhance its electron-donating ability. Specially, suitable adsorption amount is the key factor to improve the tribo-catalytic performance. When the pyrolysis temperature is 600 °C, BC-ZnO has the best degradation efficiency, which can degrade 90% Rhodamine B (RhB) in 75 min, while ZnO can degrade only 38%. On this basis, using bovine serum albumin (BSA) as a model, the effect of tribo-catalytic reaction on controlling proteins in water was studied by fluorescence excitation-emission matrix spectroscopy (3D EEM) and infrared microscope, and the transformation of proteins was further analyzed. This study provides a new strategy to improve the tribo-catalytic performance of ZnO, and explores its application prospects of biological wastewater control.

Singlet oxygen-dominated activation of peroxymonosulfate by passion fruit shell derived biochar for catalytic degradation of tetracycline through a non-radical oxidation pathway

Waste-derived biochar has been emerged as promising catalysts to activate peroxymonosulfate (PMS) for the degradation of organic contaminants. Herein, passion fruit shell derived biochar (PFSC) was prepared by a one-pot pyrolysis method and used as a metal-free catalyst to activate PMS for the degradation of tetracycline hydrochloride (TC). The batch experiments indicated that the pyrolysis temperature could influence the efficiency of PFSC for the activation of PMS. In the PFSC-900 (prepared at 900 °C)/PMS system, the degradation rate of TC can reach 90.91%. The quenching test and electron paramagnetic resonance spectra revealed that the high catalytic performance of PFSC-900/PMS system was mainly attributed to the non-free radical reaction pathway containing a carbon bridge, and the TC degradation was controlled primarily by singlet oxygen-mediated oxidation. Moreover, the carboxyl group of ketones and the graphite-N atoms on PFSC-900 are the possible active sites of the non-free radical pathway including direct electron transfer or the formation of O₂^•-/¹O₂. This study not only shows a new type of biochar as an efficient catalyst for PMS activation but also provides a way of value-added reuse of passion fruit shell.

Insights into the mechanism of hydrogen peroxide activation with biochar produced from anaerobically digested residues at different pyrolysis temperatures for the degradation of BTEXS

The disposal of large amounts of biogas residue from anaerobically digested waste is a burden on environment protection. Porous biochars (BCs) were synthesized from biogas residue at three pyrolysis temperatures (300 °C, 550 °C, and 800 °C) and used to catalyze H₂O₂ for the degradation of benzene, toluene, ethylbenzene, xylene isomers (ortho, para, and meta), and styrene (BTEXS) to develop a new use for biogas residues. The prepared BCs were characterized through scanning electron microscopy, Brunauer-Emmett-Teller method, Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy. Results showed that BC800/H₂O₂ had the highest BTEXS degradation performance over 6 h. The degradation kinetic data were most consistent with the pseudo-second-order model. The different catalytic effect of the three BCs pyrolyzed at different temperatures were attributed to the dominant active sites (C-O/C-OH/C=C/C=O groups, pyridinic N, and graphitic N) that induced the production of reactive oxygen species (ROS). ROS-quenching experiments indicated that the degradation of BTEXS by BC300/H₂O₂, BC550/H₂O₂, and BC800/H₂O₂ involved ∙OH, ∙O₂^-, and ¹O₂. ∙OH was the dominant ROS in BC300/H₂O₂ and BC550/H₂O₂, and ¹O₂ was the dominant ROS in BC800/H₂O₂. Our findings provided new insight into the different catalytic mechanisms for BC production at different pyrolysis temperatures and demonstrated that a porous BC catalyst with high utilization value could be prepared from biogas residue and could hold considerable potential for application in BTEXS treatment in the future.

Thiourea-assisted one-step fabrication of a novel nitrogen and sulfur co-doped biochar from nanocellulose as metal-free catalyst for efficient activation of peroxymonosulfate

The N, S co-doped biochar (N, S-BC) with multistage pore structure was successfully synthesized from nanocellulose and thiourea by one-step pyrolysis, which could effectively activate peroxymonosulfate (PMS) to degrade sulfamethoxazole (SMX) in water. Moreover, the removal efficiency of SMX by this oxidation system was 2.3-3.1 times than that of other systems activated by common metal oxides (such as Fe₃O₄、Fe₂O₃, and MnO₂). More importantly, the mechanism of the N, S-BC/PMS process was deduced by reactive oxygen species (ROS) quenching experiment and electron paramagnetic resonance (EPR) test, which exhibited that surface-bound free radicals and singlet oxygen (¹O₂) played an essential role in the SMX degradation. Surprisingly, the sulfate radical (SO₄^•-) and hydroxyl radical (^•OH) produced in this system existed in a bound state on the surface of the carbon catalyst to react with SMX, rather than dispersed in the aqueous solution. This particular form of free radicals could resist the influence of background substances and pH changes in water, and maintain excellent SMX degradation efficiency under different water matrices and pH. This study provides a new insight into the application of carbon catalyst in actual water pollution control.