Superior fenton-like degradation of tetracycline by iron loaded graphitic carbon derived from microplastics: Synthesis, catalytic performance, and mechanism

The construction of Z-scheme heterojunction ZnIn2S4@CuO with enhanced charge transfer capability and its mechanism study for the visible light degradation of tetracycline

In this study, copper oxide (CuO) was prepared by the microwave-assisted hydrothermal technique subsequently, CuO was grown in situ onto different rare metal compounds to prepare Z-scheme heterojunctions to improve the degradation efficiency of tetracycline (TC) in water environments. Various characterization proved the successful synthesis of all composite materials, and the formation of tight heterojunction interfaces, among which, the core-shell structure ZnIn2S4@CuO exhibited excellent photocatalytic degradation capability. Research results indicated that the degradation efficiency of ZnIn2S4@CuO for TC (50 mg/L) in the water environment reached 95.8 %, and the degradation rate is 2.41 times and 12.93 times that of CuO and ZnIn2S4 alone, respectively, the reason is because of the introduction of ZnIn2S4, Z-scheme heterojunction structures and internal electric field (IEF) is constructed and formed to extend the visible light response range of photocatalysts to improve electron-hole separation efficiency, and enhance charge transfer. In addition, ZnIn2S4@CuO-2 exhibited good stability and reproducibility, with no significant loss of activity after five cycles. Finally, the precise locations of free radical attack on TC were investigated by the combined use of high-resolution mass spectrometry (HR-MC) and frontier electron densities (FEDs), and a reasonable degradation pathway was provided. The results of this research provide a new and viable approach to overcome the limitations of conventional photocatalytic materials in terms of limited visible light absorption range and fast carrier recombination rates, which offers promising prospects for a wide range of applications in the field of wastewater purification.

Effective degradation of tetracycline in aqueous solution by an electro-Fenton process using chemically modified carbon/α-FeOOH as catalyst

This study applied an electro-Fenton process using chemically modified activated carbon derived from rubber seed shells loaded with α-FeOOH (RSCF) as catalyst to remove tetracycline residues from aquatic environment. Catalyst characteristics were evaluated using SEM, EDS, XRD, and XPS, showing successful insertion of iron onto the activated carbon. The effects of the parameters were investigated, and the highest treatment efficiency was achieved at pH of 3, Fe: H2O2 ratio (w/w) of 500:1, catalyst dose of 1 g/L, initial TCH concentration of 100 mg/L, and electric current of 150 mA, with more than 90% of TCH being eliminated within 30 min. Furthermore, even after five cycles of use, the treatment efficiency remains above 90%. The rate constant is calculated to be 0.218 min-1, with high regression coefficients (R 2 = 0.93). The activation energy (Ea) was found to be 32.2 kJ/mol, indicating that the degradation of TCH was a simple reaction with a low activation energy. These findings showed that the RSCF is a highly efficient and cost-effective catalyst for TCH degradation. Moreover, the use of e-Fenton process has the advantage of high efficiency, low cost thanks to the recyclability of the catalyst, and environmental friendliness thanks to less use of H2O2.

Recent updates on remediation approaches of environmentally occurring pollutants using visible light-active nano-photocatalysts

Photocatalysis emerges as a potential remedy for the issue of an unreliable light source. Recognized as the most dependable and potent energy source sustaining life on Earth, sunlight offers a promising solution. Sunlight is abundant and free, operational costs associated with running photocatalytic system using nanoparticles are often lower compared to system relying on artificial light source. The escalating problem of water pollution, particularly in highly industrialized nations, necessitates effective wastewater treatment methods. These methods aim to combat elevated pollution levels, encompassing pharmaceuticals, dyes, flame retardants, and pesticide components. Advanced oxidation processes within photocatalytic wastewater treatment exhibit substantial promise for removing complex organic pollutants. Doped nanomaterials, with their enhanced properties, enable efficient utilization of light. Coupled nanomaterials present significant potential in addressing both water and energy challenges by proficiently eliminating persistent pollutants from environment. Photocatalysis when exposed to sunlight can absorb photons and generate e- h + pairs. This discussion briefly outlines the wastewater treatment facilitated by interconnected nanomaterials, emphasizing their role in water-energy nexus. In exploring the capabilities of components within a functional photocatalyst, a comprehensive analysis of both simple photocatalysts and integrated photocatalytic systems is undertaken. Review aims to provide detailed explanation of the impact of light source on photon generation and significance of solar light on reaction kinetics, considering various parameters such as catalyst dosage, pH, temperature, and types of oxidants. By shedding light on these aspects, this review seeks to enhance our understanding of intricate processes involved in photocatalysis and its potential applications in addressing contemporary environmental challenges.

Straw-derived biochar for the removal of antibiotics from water: Adsorption and degradation mechanisms, recent advancements and challenges

Antibiotics, a kind of containments with the properties of widely distributed and difficult to degrade, has aroused extensive attention in the world. As a prevalent agricultural waste, straws can be utilized to prepare biochar (straw-derived biochar, SBC) to remove antibiotics from aquatic environment. To date, although a number of review papers have summarized and discussed research on biochar application in wastewater treatment and soil remediation, there are few reviews on SBC for antibiotic removal. Due to the limitations of poor adsorption and degradation performance of the pristine SBC, it is necessary to modify SBC to improve its applications for antibiotics removal. The maximum antibiotic removal capacity of modified SBC could reach 1346.55 mg/g. Moreover, the adsorption mechanisms between modified SBC and antibiotics mainly involve π-π interactions, electrostatic interactions, hydrophobic interactions, and charge dipole interactions. In addition, the modified SBC could completely degrade antibiotics within 6 min by activating oxidants, such as PS, PDS, H2O2, and O3. The mechanisms of antibiotic degradation by SBC activated oxidants mainly include free radicals (including SO4•-, •OH, and O2•-) and non-free radical pathway (such as, 1O2, electrons transfer, and surface-confined reaction). Although SBC and modified SBC have demonstrated excellent performance in removing antibiotics, they still face some challenges in practical applications, such as poor stability, high cost, and difficulties in recycling. Therefore, the further research directions and trends for the development of SBC and biochar-based materials should be taken into consideration.

Efficient Photocatalytic H2 O2 Production Ability of a Novel Graphitic Carbon Nitride/Carbon Composites under Visible Light

In the present work, using one-step calcination of a mixture made of potassium hydroxide (KOH), melamine, and microplastics, this work prepares a novel graphitic carbon nitride/carbon (g-C3 N4 /C) composite, which can be employed to photo-catalytically produce hydrogen peroxide (H2 O2 ) at a high rate up to 6.146 mmol g-1 h-1 under visible light irradiation. By analyzing the energy band structure of the catalyst, the production of H2 O2 in this system consists of two single-electron reactions. The modification of KOH makes abundant N-vacancies caused by cyano-groups in g-C3 N4 , enhancing the electron absorption ability. Moreover, the introduction of graphitic carbon increases its specific surface area and porosity and improves the adsorption ability of O2 . Simultaneously, their synergism reduces the g-C3 N4 band gap, making both the conduction-band and valence-band positions more negative, showing enhanced reduction ability, lowering the energy barrier for oxygen reduction, and greatly improving the photogeneration performance of H2 O2 .

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.

Biochar/layered double hydroxides composites as catalysts for treatment of organic wastewater by advanced oxidation processes: A review

Heterogeneous advanced oxidation process has been widely studied as an effective method for removing organic pollutants in wastewater, but the development of efficient catalysts is still challenging. This review summaries the present status of researches on biochar/layered double hydroxides composites (BLDHCs) as catalysts for treatment of organic wastewater. The synthesis methods of layered double hydroxides, the characterizations of BLDHCs, the impacts of process factors influencing catalytic performance, and research advances in various advanced oxidation processes are discussed in this work. The integration of layered double hydroxides and biochar provides synthetic effects for improving pollutant removal. The enhanced pollutant degradation in heterogeneous Fenton, sulfate radical-based, sono-assisted, and photo-assisted processes using BLDHCs have been verified. Pollutant degradation in heterogeneous advanced oxidation processes using BLDHCs is influenced by process factors such as catalyst dosage, oxidant addition, solution pH, reaction time, temperature, and co-existing substances. BLDHCs are promising catalysts due to the unique features including easy preparation, distinct structure, adjustable metal ions, and high stability. Currently, catalytic degradation of organic pollutants using BLDHCs is still in its infancy. More researches should be conducted on the controllable synthesis of BLDHCs, the in-depth understanding of catalytic mechanism, the improvement of catalytic performance, and large-scale application of treating real wastewater.

Removal of Antibiotics Using an Algae-Algae Consortium (Chlorella protothecoides and Chlorella vulgaris)

The intensive use of antibiotics (for human, veterinary, and agricultural purposes) has steadily increased over the last 30 years. Large amounts of antibiotic residues are released into aquatic systems, mostly due to inefficient wastewater treatment. Conventional wastewater treatments are not designed to remove emerging contaminants (such as antibiotics) from wastewater. Therefore, algae treatment (phycoremediation) has emerged as a promising choice for cost-effective, eco-friendly, and sustainable wastewater treatment. For this reason, we investigated the removal performance of a well-established algal consortia (Chlorella protothecoides and Chlorella vulgaris) used in passive wastewater treatment ponds (Mosselbay, South Africa). Five antibiotics (sulfamethoxazole, amoxicillin, trimethoprim, ofloxacin, and clarithromycin) were selected for their ubiquity and/or low removal efficiency in conventional wastewater treatment plants (WWTPs). For each antibiotic, two concentrations were used: one environmentally relevant (10 ppb) and another 10 times higher (100 ppb), tested in triplicate and collected at two-time points (7 and 10 days). The algae remained viable over the exposure period (which is similar to the retention time within maturation ponds) and exhibited the capacity to remove sulfamethoxazole (77.3% ± 3.0 and 46.5% ± 5.3) and ofloxacin (43.5% ± 18.9 and 55.1% ± 12.0) from samples spiked with 10 and 100 ppb, respectively. This study demonstrates the potential and innovation of algal remediation for contaminants in a developing country context, where minimal infrastructure is available.

Ultrasonic-assisted photocatalytic degradation of various organic contaminants using ZnO supported on a natural polymer of sporopollenin

Water resource pollution by organic contaminants is an environmental issue of increasing concern. Here, sporopollenin/zinc oxide (SP/ZnO) was used as an environmentally friendly and durable catalyst for sonophotocatalytic treatment of three organic compounds: direct blue 25 (DB 25), levofloxacin (LEV), and dimethylphtalate (DMPh). The resulting catalyst had a 2.65 eV bandgap value and 9.81 m²/g surface area. The crystalline structure and functional groups of SP/ZnO were confirmed by X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FTIR) analyses. After 120 min of the sonophotocatalysis, the degradation efficiencies of DB 25, LEV, and DMPh by SP/ZnO were 86.41, 75.88, and 62.54%, respectively, which were higher than that of the other investigated processes. The role of reactive oxygen species were investigated using various scavengers, enhancers, photoluminescence, and o-phenylenediamine. Owing to its stability, the catalyst exhibited good reusability after four consecutive cycles. In addition, the high integrity of the catalyst was confirmed by scanning electron microscopy (SEM), XRD, and FTIR analyses. After four consecutive examinations, the leaching of zinc in the aqueous phase was < 3 mg/L. Moreover, gas chromatography-mass spectrometry (GC-MS) analyses indicated that the contaminants were initially converted into cyclic compounds and then into aliphatic compounds, including carboxylic acids and animated products. Thus, this study synthesized an environmentally friendly and reusable SP/ZnO composite for the degradation of various organic pollutants using a sonophotocatalytic process.

From Fenton and ORR 2e−-Type Catalysts to Bifunctional Electrodes for Environmental Remediation Using the Electro-Fenton Process

Currently, the presence of emerging contaminants in water sources has raised concerns worldwide due to low rates of mineralization, and in some cases, zero levels of degradation through conventional treatment methods. For these reasons, researchers in the field are focused on the use of advanced oxidation processes (AOPs) as a powerful tool for the degradation of persistent pollutants. These AOPs are based mainly on the in-situ production of hydroxyl radicals (OH•) generated from an oxidizing agent (H2O2 or O2) in the presence of a catalyst. Among the most studied AOPs, the Fenton reaction stands out due to its operational simplicity and good levels of degradation for a wide range of emerging contaminants. However, it has some limitations such as the storage and handling of H2O2. Therefore, the use of the electro-Fenton (EF) process has been proposed in which H2O2 is generated in situ by the action of the oxygen reduction reaction (ORR). However, it is important to mention that the ORR is given by two routes, by two or four electrons, which results in the products of H2O2 and H2O, respectively. For this reason, current efforts seek to increase the selectivity of ORR catalysts toward the 2e− route and thus improve the performance of the EF process. This work reviews catalysts for the Fenton reaction, ORR 2e− catalysts, and presents a short review of some proposed catalysts with bifunctional activity for ORR 2e− and Fenton processes. Finally, the most important factors for electro-Fenton dual catalysts to obtain high catalytic activity in both Fenton and ORR 2e− processes are summarized.

Degradation of organic pollutants from water by biochar-assisted advanced oxidation processes: Mechanisms and applications

Biochar has shown large potential in environmental remediation because of its low cost, large specific surface area, porosity, and high conductivity. Biochar-assisted advanced oxidation processes (BC-AOPs) have recently attracted increasing attention to the remediation of organic pollutants from water. However, the effects of biochar properties on catalytic performance need to be further explored. There are still controversial and knowledge gaps in the reaction mechanisms of BC-AOPs, and regeneration methods of biochar catalysts are lacking. Therefore, it is necessary to systematically review the latest research progress of BC-AOPs in the treatment of organic pollutants in water. In this review, first of all, the effects of biochar properties on catalytic activity are summarized. The biochar properties can be optimized by changing the feedstocks, preparation conditions, and modification methods. Secondly, the catalytic active sites and degradation mechanisms are explored in different BC-AOPs. Different influencing factors on the degradation process are analyzed. Then, the applications of BC-AOPs in environmental remediation and regeneration methods of different biochar catalysts are summarized. Finally, the development prospects and challenges of biochar catalysts in environmental remediation are put forward, and some suggestions for future development are proposed.

Titanium-based MAX-phase with sonocatalytic activity for degradation of oxytetracycline antibiotic

In light of growing environmental concerns over emerging contaminants in aquatic environments, antibiotics in particular, have prompted the development of a new generation of effective sonocatalytic systems. In this study, a new type of nano-laminated material, Ti₂SnC MAX phase, is prepared, characterized, and evaluated for the sonocatalytic degradation of oxytetracycline (OTC) antibiotic. A variety of identification analyses, including X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, Brunauer-Emmett-Teller, and diffuse reflectance spectroscopy, were conducted to determine the physicochemical properties of the synthesized catalyst. By optimizing the operating factors, total degradation of OTC occurs within 120 min with 1 g L^-1 catalyst, 10 mg L^-1 OTC, at natural pH of 7.1 and 150 W ultrasonic power. The scavenger studies conclude that the singlet oxygen and superoxide ions are the most active species during the sonocatalytic reaction. Based on the obtained data and GC-MS analysis, a possible sonocatalytic mechanism for the OTC degradation in the presence of Ti₂SnC is proposed. The catalyst reusability within eight consecutive runs reveals the proper stability of Ti₂SnC MAX phase. The results indicate the prospect for MAX phase-based materials to be developed as efficient sonocatalysts in the treatment of antibiotics, suggesting a bright future for the field.

A review of disposable facemasks during the COVID-19 pandemic: A focus on microplastics release

The COVID-19 epidemic seriously threats the human society and provokes the panic of the public. Personal Protective Equipment (PPE) are widely utilized for frontline health workers to face the ongoing epidemic, especially disposable face masks (DFMs) to prevent airborne transmission of coronavirus. The overproduction and massive utilization of DFMs seriously challenge the management of plastic wastes. A huge amount of DFMs are discharged into environment, potentially induced the generation of microplastics (MPs) owing to physicochemical destruction. The MPs release will pose severe contamination burden on environment and human. In this review, environmental threats of DFMs regarding to DFMs fate in environment and DFMs threats to aquatic and terrestrial species were surveyed. A full summary of recent studies on MPs release from DFMs was provided. The knowledge of extraction and characterizations of MPs, the release behavior, and potential threats of MPs derived from DFMs was discussed. To confront the problem, feasible strategies for control DFMs pollution were analyzed from the perspective of source control and waste management. This review provides a better understanding the threats, fate, and management of DFMs linked to COVID-19 pandemic.

Wastewater treatment with nanomaterials for the future: A state-of-the-art review

Aquatic and terrestrial ecosystems are both threatened by toxic wastewater. The unique properties of nanomaterials are currently being studied thoroughly for treating sewage. Nanomaterials also have the advantage of being capable of removing organic matter, fungi, and viruses from wastewater. Advanced oxidation processes are used in nanomaterials to treat wastewater. Additionally, nanomaterials have a large effective area of contact due to their tiny dimensions. The adsorption and reactivity of nanomaterials are strong. Wastewater treatment would benefit from the development of nanomaterial technology. Second, the paper provides a comprehensive analysis of the unique characteristics of nanomaterials in wastewater treatment, their proper use, and their prospects. In addition to focusing on their economic feasibility, since limited forms of nanomaterials have been manufactured, it is also necessary to consider their feasibility in terms of their technical results. According to this study, the significant adsorption area, excellent chemical reaction, and electrical conductivity of nanoparticles (NPs) contribute to the successful treatment of wastewater.

Response surface modeling of ceftriaxone removal from hospital wastewater

In recent decades, an emerging concern of widespread antimicrobial resistance has been raised due to the existence of pharmaceutical samples such as antibiotics in an aqueous medium. Herein, antibiotic ceftriaxone (CTX) removal from hospital wastewater employing a hybrid process of electrocoagulation (EC) and adsorption (AD) was investigated. The response surface methodology (RSM) was employed to study the influences of main operating variables, including initial CTX concentration, pH, current density, reaction time, and chitosan dosage, on the removal efficiency of the treatment process. Under the optimum condition of the employed EC/AD hybrid treatment process, where initial CTX concentration, pH solution, the current density, adsorbent dosage, and reaction time were set at 20.0 mg L^-1, 7.5, 6.0 mA cm^-2, 0.75 g L^-1, and 12.5 min, respectively, the removal efficiency of 100% was achieved. Analysis of variance (ANOVA) confirmed that the developed quadratic treatment model is highly significant. The applied EC/AD hybrid treatment process revealed the electrical energy consumption of 0.84 kWh m^-3 and 0.2168 kWh (g Al)^-1 per cubic meter of hospital wastewater and gram of consumed aluminum electrode, respectively. The second-order kinetic model with R² of 0.9514 and the Langmuir isotherm model with R² of 0.973 best fit the developed EC/AD hybrid treatment process, and q_m was found to be 111.1 mg g^-1. The obtained experimental results confirmed that the CTX concentration of the hospital wastewater was reduced to zero after applying the EC/AD hybrid process.

An approach to removing COD and BOD based on polycarbonate mixed matrix membranes that contain hydrous manganese oxide and silver nanoparticles: A novel application of artificial neural network based simulation in MATLAB

This study aimed to determine the efficacy of novel ultrafiltration and mixed matrix membrane (MMM) composed of hydrous manganese oxide (HMO) and silver nanoparticles (Ag-NPs) for the removal of biological oxygen demand (BOD) and chemical oxygen demand (COD). In the polycarbonate (PC) MMM, the weight percent of HMO and Ag-NP has been increased from 5% to 10%. A neural network (ANN) was used in this study to compare PC-HMO and Ag-NP. MMM was evaluated in combination with HMO and Ag-NP loadings in order to assess their effects on pure water flux, mean pore size, porosity, and efficacy in removing BOD and COD. HMO and Ag-NPs can decrease membrane porosity in the casting solution while increasing mean pore size. According to the study's findings, the artificial neural network model appears to be highly appropriate for predicting the removal of BOD and COD. To develop a successful model, a suitable input dataset was selected, which consisted of BOD and COD. An ideal model architecture for MMM was proposed based on an optimal number of hidden layers (2 layers) and neurons (5-8 neurons). Experiments and predicted data show a strong correlation between the developed models. BOD was predicted with an excellent R2 and a low root mean square error (RMSE) of 0.99 and 0.05%, respectively, while COD was predicted with an excellent R2 and a low RMSE of 0.99 and 0.09%, respectively. Based on the results, Ag-NP was found to be an excellent candidate for the preparation of MMMs as well as convenient for the removal of BOD and COD from polluted water sources.

Ultrasound-enhanced catalytic degradation of simulated dye wastewater using waste printed circuit boards: catalytic performance and artificial neuron network-based simulation

Recent developments of heterogeneous advanced oxidation for refractory organic contaminants and catalysts made of solid waste have attracted much attention. In this work, waste printed circuit board (wPCB) was used for catalytic degradation of simulated textile wastewater enhanced by ultrasound. Catalytic degradation of rhodamine B (RhB) and methylene blue (MB) was conducted in the presence of H₂O₂. Effect of ultrasound, wPCB, H₂O₂, pH, and dye concentration was investigated by single factor experiments. The growing catalytic efficiency was determined by ultrasound. The removal efficiency of MB and RhB are influenced by wPCB, H₂O₂, pH, and dye concentration. Degradation efficiency is accelerated with increasing wPCB dosage and H₂O₂ and decreasing dye concentration. Effective degradation of MB and RhB is obtained under broader pH region, attractively at neutral pH. Under optimal conditions, MB removal reaches 98.83% at 90 min while RhB removal reaches 99.57% at 80 min. Hydroxyl radicals play an important role in catalytic process. Tentative mechanism for catalytic degradation of MB and RhB are discussed based on multiple characterizations. Superior reusability of wPCB proves that wPCB is highly durable catalyst. Due to low cost and high efficiency, wPCB is attractive as effective catalyst for treatment of organic wastewater. Artificial neuron network-based (ANN) simulation, as a widely used artificial intelligence algorithm, was one of preferred methods for the wastewater treatment due to its unique properties in solving complex processes. An ANN model was designed for the prediction of the performance of ultrasound-enhanced catalytic degradation with a high R value (0.99).

A facile synthesis of PEGylated Cu2O@SiO2/MnO2 nanocomposite as efficient photo−Fenton−like catalysts for methylene blue treatment

The removal of toxic organic dyes from wastewater has received much attention from the perspective of environmental protection. Metal oxides see wide use in pollutant degradation due to their chemical stability, low cost, and broader light absorption spectrum. In this work, a Cu2O−centered nanocomposite Cu2O@SiO2/MnO2−PEG with an average diameter of 52 nm was prepared for the first time via a wet chemical route. In addition, highly dispersed MnO2 particles and PEG modification were realized simultaneously in one step, meanwhile, Cu2O was successfully protected under a dense SiO2 shell against oxidation. The obtained Cu2O@SiO2/MnO2−PEG showed excellent and stable photo−Fenton−like catalytic activity, attributed to integration of visible light−responsive Cu2O and H2O2−responsive MnO2. A degradation rate of 92.5% and a rate constant of 0.086 min−1 were obtained for methylene blue (MB) degradation in the presence of H2O2 under visible light for 30 min. Additionally, large amounts of •OH and 1O2 species played active roles in MB degradation. Considering the enhanced degradation of MB, this stable composite provides an efficient catalytic system for the selective removal of organic contaminants in wastewater.

BCOFGs loaded with nano-FexSy for the catalytic degradation of QNC: Contribution and mechanism of OFGs for reductive iron regeneration

Biochar currently served as the support for dispersed metal nanoparticles and cooperated with pyrite to generate more reactive radicals in organic pollution degradation system. But the mechanism of interaction between biochar and pyrite has not been elucidated. In this paper, biochar with oxygen-containing functional groups (OFGs) served as a stable dispersant to prepare nano-Fe_xS_y loaded biochar materials (BC_OFGs@nano-Fe_xS_y). BC_OFGs coordinated with nano-Fe_xS_y to overcome its drawbacks, boosting QNC removal efficiency from 28.64% to 100%. The XPS and the linear sweep voltammetry (LSV) results revealed higher Fe(II) content and higher electron transfer rate on used BC_OFGs@nano-Fe_xS_y, further validating that hydroxyl functional groups on biochar surface provided electrons to Fe(III) to achieve efficient Fe(II)/Fe(III) cycling. Based on comparative experiments and studies on the roles of iron, S(II) species and OFGs, we clearly revealed that OFGs on biochar materials surface coordinated with nano-Fe_xS_y to catalyze the degradation of QNC. The degradation efficiency of BC_OFGs@nano-Fe_xS_y for QNC was still as high as 91.39% after five cycles, providing full demonstrations that OFGs and S(II) as the abundant electron donor coordinated with Fe species for QNC catalytic degradation and further enhanced the catalytic performance and stability of nano-Fe_xS_y.

Heterogeneous Fenton degradation of persistent organic pollutants using natural chalcopyrite: effect of water matrix and catalytic mechanism

Natural chalcopyrite was evaluated as heterogeneous Fenton catalyst. Catalytic performance was evaluated considering different systems, catalyst dosage, H2O2 concentration, and reaction temperature, and increasing the parameters favors rhodamine B degradation. Effect of aqueous matrix was systematically examined, involving solution pH, anions, cations, dissolved organic matter, and initial pollutant concentration. The degradation performance is slightly influenced by these parameters. Rhodamine B removal is 96.5% within 120 min, the rate constant ranges from 0.0086 min-1 to 0.0415 min-1 depending on temperature, and the activation energy is 79 kJ/mol. Effective degradation of different persistent organic pollutants including methylene blue, malachite green, sodium butyl xanthate, tetracycline, and p-nitrophenol is verified by UV-vis spectra. Natural chalcopyrite was characterized by advanced techniques including scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Reactions between chalcopyrite and H2O2 cause copper leaching and iron oxidation. Quenching experiments and electron paramagnetic resonance reveal the dominant role of hydroxyl radical in catalytic process. The catalytic mechanism induced by surface iron and leached copper derived from chalcopyrite is proposed.

Efficient visible-light-driven degradation of tetracycline by a 2D/2D rGO-Bi2WO6 heterostructure

Constructing heterostructures has been a simple yet effective strategy for improving the photocatalytic performance of individual semiconductor photocatalysts. However, the poor quality of the contacted interface coupled with the narrow and overlapping light absorption scope between heterocomponents limits potential improvement. Herein, a 2D/2D rGO-Bi₂WO₆ heterostructure with face-to-face compact contact interface and UV to NIR light absorption ability was synthesized to overcome the aforementioned limitations. The as-prepared 2 wt%-rGO-Bi₂WO₆ with a high contact interface quality exhibits the highest kinetic rate of (5.53 ± 0.75) × 10^-2 L mg^-1 min^-1 toward tetracycline (TC) degradation, which is 2.4 times higher than that of pristine Bi₂WO₆ and 2.1 times higher than that of the 2 wt%-rGO-Bi₂WO₆ composite with a poor interface quality. Moreover, approximately 30% of TC can be mineralized with a 2 wt%-rGO-Bi₂WO₆ presented system after 120 min. The subsequent Escherichia coli culture and liquid chromatography-mass spectrometry were employed to detect the biotoxicity variation of degradation intermediates and the possible transformation pathways of TC, respectively. Finally, the reactive species trapping results indicate that photogenerated holes and superoxide radical anions play dominant roles during the TC degradation process. This work provides a facile and effective method to fabricate an efficient heterojunction photocatalyst for pollutant degradation.

Controlled carbonization of microplastics loaded nano zero-valent iron for catalytic degradation of tetracycline

Nano zero-valent iron loaded porous carbon derived from microplastics was designed as heterogeneous catalyst for degradation of persistent organic pollutants. Controlled carbonization of microplastics with molten salt was conducted to tune the morphology of carbon product. Controlled carbonization induces higher carbon yield (from 17.73% to 52.24%) and larger surface area (from 403.72 m²/g to 601.82 m²/g). The catalyst (Fe/MMPC) was characterized by Raman, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscope. Loading nano zero-valent iron onto porous carbon are verified in the catalyst. The process factors including Fe/MMPC dosage, H₂O₂, pH, anions, and temperature were studied to estimate the catalytic performance. Tetracycline degradation (81.8% within 10 min) is effectively obtained in the Fe/MMPC and H₂O₂ system. The apparent rate constant is 0.1311-0.2999 min^-1 under different temperature, and the activation energy of catalytic process is 22 kJ/mol. Pollutants including rhodamine B, p-nitrophenol, and butylxanthate are efficiently degraded in the catalytic system. The predominant species of catalytic reactions are hydroxyl radicals, which are mainly produced from H₂O₂ activation enhanced by zero-valent iron in Fe/MMPC. This work offers an innovative strategy for microplastic management and wastewater treatment.

Role of Reverse Logistics Activities in the Recycling of Used Plastic Bottled Water Waste Management

The purpose of this study is to investigate the role of reverse logistics in the recycling of used plastic bottles and waste management in Ethiopia. To achieve the study’s goal, the authors used a descriptive research design where a combination of primary and secondary data sources was employed. Primary data was collected from 258 respondents, while secondary data was taken from office manuals, yearly reports, and brochures. The findings of our analysis show that incineration, landfilling, and dumping of used plastic bottles on the side of the road are all apparent in the environment, making the city and its environs filthy and unpleasant to live in. This study also discovered that reuse and remanufacturing have become less common and are rarely practiced. Even though plastic waste disposal guidelines have been created, our investigation revealed that there is a lack of community understanding regarding solid waste management, and some stakeholders actively disregard waste management proclamations. Thus, it is recommended that all stakeholders, including the government, business owners, plastic bottled water makers, and the public, pay close attention to waste disposal, particularly of non-biodegradable pollutants in Ethiopia’s urban and rural areas.

Recent advances in waste-derived functional materials for wastewater remediation

Water pollution is a major concern for public health and a sustainable future. It is urgent to purify wastewater with effective methods to ensure a clean water supply. Most wastewater remediation techniques rely heavily on functional materials, and cost-effective materials are thus highly favorable. Of great environmental and economic significance, developing waste-derived materials for wastewater remediation has undergone explosive growth recently. Herein, the applications of waste (e.g., biowastes, electronic wastes, and industrial wastes)-derived materials for wastewater purification are comprehensively reviewed. Sophisticated strategies for turning wastes into functional materials are firstly summarized, including pyrolysis and combustion, hydrothermal synthesis, sol-gel method, co-precipitation, and ball milling. Moreover, critical experimental parameters within different design strategies are discussed. Afterward, recent applications of waste-derived functional materials in adsorption, photocatalytic degradation, electrochemical treatment, and advanced oxidation processes (AOPs) are analyzed. We mainly focus on the development of efficient functional materials via regulating the internal and external characteristics of waste-derived materials, and the material's property-performance correlation is also emphasized. Finally, the key future perspectives in the field of waste-derived materials-driven water remediation are highlighted.

Construction of Au and C60 quantum dots modified materials of Institute Lavoisier-125(Ti) architectures for antibiotic degradation: Performance, toxicity assessment, and mechanistic insight

High-performance and stabilized photocatalytic degradation of antibiotic contaminants still remains a challenge in environmental photocatalysis and has been studied worldwide. In this work, hybrid Au and C60 quantum dots decorated Materials of Institute Lavoisier-125(Ti) (MIL-125(Ti)) composites were successfully fabricated for visible-light photocatalytic tetracycline degradation with pristine MIL-125(Ti) as a comparison. The experimental results revealed that the introduction of C60 quantum dots and Au nanoparticles resulted in highly enhanced visible-light harvesting and charge separation for efficient tetracycline degradation. The optimal Au/C60-MIL-125(Ti)-1.0% sample exhibited the highest visible-light photocatalytic performance, and the corresponding rate constant was approximately 9.19 times of MIL-125(Ti), indicating the significant roles of Au and C60 quantum dots in boosting visible-light absorption and charge separation. Furthermore, the radical species, possible degradation pathways and toxicity assessment, and photocatalytic mechanism were also investigated. Current work indicates a synergistic strategy for enhancing visible-light harvesting and charge separation to fabricate high-performance composite photocatalysts.

Preparation, characterization, and applications of Fe-based catalysts in advanced oxidation processes for organics removal: A review

Fe-based catalysts as low-cost, high-efficiency, and non-toxic materials display superior catalytic performances in activating hydrogen peroxide, persulfate (PS), peracetic acid (PAA), percarbonate (PC), and ozone to degrade organic contaminants in aqueous solutions. They mainly include ferrous salts, zero-valent iron, iron-metal composites, iron sulfides, iron oxyhydroxides, iron oxides, and supported iron-based catalysts, which have been widely applied in advanced oxidation processes (AOPs). However, there is lack of a comprehensive review systematically reporting their synthesis, characterization, and applications. It is imperative to evaluate the catalytic performances of various Fe-based catalysts in diverse AOPs systems and reveal the activation mechanisms of different oxidants by Fe-based catalysts. This work detailedly summarizes the synthesis methods and characterization technologies of Fe-based catalysts. This paper critically evaluates the catalytic performances of Fe-based catalysts in diverse AOPs systems. The effects of solution pH, reaction temperature, coexisting ions, oxidant concentration, catalyst dosage, and external energy on the degradation of organic contaminants in the Fe-based catalyst/oxidant systems and the stability of Fe-based catalysts are also discussed. The activation mechanisms of various oxidants and the degradation pathways of organic contaminants in the Fe-based catalyst/oxidant systems are revealed by a series of novel detection methods and characterization technologies. Future research prospects on the potential preparation means of Fe-based catalysts, practical applications, assistive technologies, and impact in AOPs are proposed.

Magnetic copper smelter slag as heterogeneous catalyst for tetracycline degradation: Process variables, kinetics, and characterizations

The treatment of solid wastes and wastewater for sustainable development has been a hot topic. This work proposes a novel process of "waste treating waste" using magnetic copper smelter slag (CSS) as heterogeneous catalyst. The effect of process variables and water matrix was studied on catalytic performance. Under conditions of CSS 10 g/L, H₂O₂ 100 mM, pH 4.4, and temperature 25 °C, tetracycline can be effectively degraded within 30 min. The apparent rate constant is comparable to or higher than previous reports, and the activation energy is 37 kJ/mol. The broad operation pH, slight effect of water matrix, and magnetic property of CSS are favorable for potential application. CSS was characterized by N₂ adsorption-desorption isotherm, SEM-EDS, XRD, XPS, ICP and zeta potential. The dominant components of CSS are fayalite and magnetite, and the major metals of Fe and Cu provide active sites for H₂O₂ activation. Hydroxyl radical generated by H₂O₂ activation is dominant oxidative specie for tetracycline degradation. The plausible mechanism of tetracycline degradation in the solution and on catalyst surface is proposed.

Preparation of Sepiolite Nanofibers Supported Zero Valent Iron Composite Material for Catalytic Removal of Tetracycline in Aqueous Solution

The heavy use of antibiotics in medicine, stock farming and agriculture production has led to their gradual accumulation in environmental media, which poses a serious threat to ecological environment and human safety. As an efficient and promising catalyst for the degradation of antibiotics, nanoscale zero valent iron (nZVI) has attracted increasing attention in recent years. In this study, sepiolite nanofiber supported zero valent iron (nZVI/SEP) composite was prepared via a facile and environmentally friendly method. The nZVI particles (with size of 20–60 nm) were dispersed evenly on the surface of sepiolite nanofibers, and the catalytic performance for the removal of tetracycline hydrochloride (TC-HCl) in aqueous system was investigated. The effect of nZVI loading amount, catalyst dosage, H₂O₂ concentration and pH on the removal efficiency of TC-HCl were studied. It was revealed that the sepiolite supporter effectively inhibited the agglomeration of nZVI particles and increased the contact area between contaminant and the active sites, resulting in the higher catalytic performance than pure nZVI material. The TC-HCl removal efficiency of nZVI/SEP composite was up to 92.67% when TC-HCl concentration of 20 mg/L, catalyst dosage of 1.0 g/L, H₂O₂ concentration of 1.0 mM, pH value of 7. Therefore, the nZVI/SEP composites possess high catalytic activity for TC-HCl removal and have great application prospects in antibiotic wastewater treatment.

Ultrasound assisted Fenton-like degradation of dyes using copper doped graphitic carbon nitride

A novel copper doped graphitic carbon nitride (Cu-C₃N₄) was successfully synthesized and used as an effective Fenton-like catalyst. Cu-C₃N₄ was characterized by scanning electron microscopy, surface area analyzer, Fourier transform infrared spectroscopy, X-ray diffractometer, and X-ray photoelectron spectroscopy. Effect of process parameters including catalyst dosage, hydrogen peroxide (H₂O₂) concentration, solution pH, and initial methylene blue (MB) concentration was investigated to evaluate catalytic performance. The pseudo first-order kinetic model was used to describe the catalytic process. The enhancement of MB degradation is observed assisted by ultrasound. MB degradation of 96% is obtained within 30 min in Cu-C₃N₄/H₂O₂/ultrasound system, and the corresponding rate constant is 0.099 min^-1. Effective MB degradation is obtained over a broad pH range (3.3-9.9). The catalytic mechanism is examined by ultraviolet-visible spectra, quenching test, and electron spin resonance determination. The dominant mechanism of MB degradation is ascribed to the ultrasonic H₂O₂ activation by Cu-C₃N₄ for hydroxyl radical generation. Cu-C₃N₄ has good reusability and is effective to degrade rhodamine B and acid orange 7. This work not only contributes to the field of wastewater treatment, but also provides insights into the synthesis of Fenton-like catalysts. The results manifest that Cu-C₃N₄ is a promising Fenton-like catalyst for dye degradation in the field of environmental pollution remediation.