Photocatalytic degradation of sulfamethazine using a direct Z-Scheme AgI/Bi4V2O11 photocatalyst: Mineralization activity, degradation pathways and promoted charge separation 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.

Insights into copper(I) phenylacetylide with in-situ transformation of oxygen and enhanced visible-light response for water decontamination: Cu-O bond promotes exciton dissociation and charge transfer

The widespread contamination of hexavalent chromium (Cr(VI)), pharmaceuticals and personal care products (PPCPs), and dyes is a growing concern. necessitating the development of convenient and effective technologies for their removal. Copper(I) phenylacetylide (PhC2Cu) has emerged as a promising photocatalyst for environmental remediation. In this study, we introduced a functional Cu-O bond into PhC2Cu (referred to as OrPhC2Cu) by creatively converting the adsorbed oxygen on the surface of PhC2Cu into a Cu-O bond to enhance the efficiency of Cr(VI) photoreduction, PPCPs photodegradation, and dyes photodegradation through a facile vacuum activating method. The incorporation of the Cu-O bond optimized the electron structure of OrPhC2Cu, facilitating exciton dissociation and charge transfer. The exciton dissociation behavior and charge transfer mechanism were systematically investigated for the first time in the OrPhC2Cu system by photoelectrochemical tests, fluorescence and phosphorescence (PH) techniques, and density functional theory (DFT) calculations. Remarkably, the enhanced visible-light response of OrPhC2Cu improved photon utilization and significantly promoted the generation of reactive species (RSs), leading to the highly efficient Cr(VI) photoreduction (98.52% within 25 min) and sulfamethazine photodegradation (94.65% within 60 min), with 3.91 and 5.23 times higher activity compared to PhC2Cu. Additionally, the photocatalytic efficiency of OrPhC2Cu in degrading anionic dyes surpassed that of cationic dyes. The performance of the OrPhC2Cu system in treating electroplating effluent or natural water bodies suggests its potential for practical applications.

Isolation, identification, and optimization of conditions for the degradation of four sulfonamide antibiotics and their metabolic pathways in Pseudomonas stutzeri strain DLY-21

Overuse of sulfonamides in aquaculture and agriculture leads to residual drugs that cause serious pollution of the environment. However, the residues of sulfonamides in the environment are not unique, and the existing microbial degradation technology has a relatively low degradation rate of sulfonamides. Therefore, in this study, a Pseudomonas stutzeri strain (DLY-21) with the ability to degrade four common SAs was screened and isolated from aerobic compost. Under optimal conditions, the DLY-21 strain degraded four sulfonamides simultaneously within 48 h, and the degradation rates were all over 90%, with the average degradation rates of SAs being sulfoxide (SDM) ≈ sulfachloropyridazine (SCP) > sulfa quinoxaline (SQ) > sulfadiazine (SQ). In addition, the main compounds of the strain DLY-21-degrading SAs were identified by LC-MS analysis. On this basis, four detailed reaction pathways for SA degradation were deduced. This is the first report of the use of a P. stutzeri strain to degrade four sulfonamide antibiotics (SQ, SDM, SCP, and SM1), which can improve the removal efficiency of sulfonamide antibiotic pollutants and thus ameliorate environmental pollution. The results showed that DLY-21 had a good degradation effect on four SAs (SQ, SDM, SCP, and SM1).

Promoting the suitability of graphitic carbon nitride and metal oxide nanoparticles: A review of sulfonamides photocatalytic degradation

The widespread consumption of pharmaceutical drugs and their incomplete breakdown in organisms has led to their extensive presence in aquatic environments. The indiscriminate use of antibiotics, such as sulfonamides, has contributed to the development of drug-resistant bacteria and the persistent pollution of water bodies, posing a threat to human health and the safety of the environment. Thus, it is paramount to explore remediation technologies aimed at decomposing and complete elimination of the toxic contaminants from pharmaceutical wastewater. The review aims to explore the utilization of metal-oxide nanoparticles (MONPs) and graphitic carbon nitrides (g-C3N4) in photocatalytic degradation of sulfonamides from wastewater. Recent advances in oxidation techniques such as photocatalytic degradation are being exploited in the elimination of the sulfonamides from wastewater. MONP and g-C3N4 are commonly evolved nano substances with intrinsic properties. They possessed nano-scale structure, considerable porosity semi-conducting properties, responsible for decomposing wide range of water pollutants. They are widely applied for photocatalytic degradation of organic and inorganic substances which continue to evolve due to the low-cost, efficiency, less toxicity, and more environmentally friendliness of the materials. The review focuses on the current advances in the application of these materials, their efficiencies, degradation mechanisms, and recyclability in the context of sulfonamides photocatalytic degradation.

Synergistic effect of Fe doping and oxygen vacancy in AgIO3 for effectively degrading organic pollutants under natural sunlight

In this work, a series of hydrogenated Fe-doped AgIO3 (FAI-x) catalysts are synthesized for photodegrading diverse azo dyes and antibiotics. Under the irradiation of natural sunlight with a light intensity of ∼60 mW/cm2, the optimum FAI-10 exhibits a considerable rate constant for decomposing methyl orange (MO) of 0.067 min-1, about 7.4 times higher than that of AgIO3 (0.009 min-1), and 24.6% and 83.8% of MO can be decomposed over AgIO3 and FAI-10 after irradiation for 40 min. In the amplification photodegradation experiments with using 0.5 g catalyst and 400 mL MO dye solution (10 mg/L), FAI-10 possesses greatly higher photoreactivity to common semiconductors (ZnO, TiO2, In2O3 and Bi2MoO6), and the photodegradation rates over FAI-10 are 92%. Particularly, the FAI-10 shows superior stability, the activity of which remains unaltered after 8 continuous cycles. Foreign ions and water bodies have slight effect on the activity of FAI-10, but the MO degradation rates are decreased by adjusting pH values, especially when pH = 11 because of the strong electrostatic repulsion between MO and FAI-10. FAI-10 can also effectively decompose another azo dye (rhodamine B (RhB)) and diverse antibiotics (sulflsoxazole (SOX), chlortetracycline hydrochloride (CTC), tetracycline hydrochloride (TC) and ofloxacin (OFX)). The activity enhancement mechanism of FAI-10 has been systemically investigated and is ascribed to the promoted photo-absorption, charge separation and transfer efficiency, and affinity of organic pollutants, owing to the synergistic effect of Fe doping and oxygen vacancy (Ov). The photocatalytic mechanisms and process for decomposing MO are verified and proposed based on radical trapping experiments and liquid chromatography-mass spectrometry (LC-MS). This work opens an avenue for the fabrication of effective photocatalysts toward water purification.

Bismuth-Based Z-Scheme Heterojunction Photocatalysts for Remediation of Contaminated Water

Agricultural runoff, fuel spillages, urbanization, hospitalization, and industrialization are some of the serious problems currently facing the world. In particular, byproducts that are hazardous to the ecosystem have the potential to mix with water used for drinking. Over the last three decades, various techniques, including biodegradation, advanced oxidation processes (AOPs), (e.g., photocatalysis, photo-Fenton oxidation, Fenton-like oxidation, and electrochemical oxidation process adsorption), filtration, and adsorption techniques, have been developed to remove hazardous byproducts. Among those, AOPs, photocatalysis has received special attention from the scientific community because of its unusual properties at the nanoscale and its layered structure. Recently, bismuth based semiconductor (BBSc) photocatalysts have played an important role in solving global energy demand and environmental pollution problems. In particular, bismuth-based Z-scheme heterojunction (BBZSH) is considered the best alternative route to overhaul the limitations of single-component BBSc photocatalysts. This work aims to review recent studies on a new type of BBZSH photocatalysts for the treatment of contaminated water. The general overview of the synthesis methods, efficiency-enhancing strategies, classifications of BBSc and Z-scheme heterojunctions, the degradation mechanisms of Z- and S-schemes, and the application of BBZSH photocatalysts for the degradation of organic dyes, antibiotics, aromatics compounds, endocrine-disrupting compounds, and volatile organic compounds are reviewed. Finally, challenges and the future perspective of BBZSH photocatalysts are discussed.

Facilitated Visible-Light-Driven Peroxymonosulfate Activation by a Co-Fe Layered Double Hydroxide Derived p-n Heterostructure for Sulfadiazine Degradation: Affecting Parameters, Kinetics, and Mechanistic Insights

The utilization of multivalence ionic metal species generated through a peroxymonosulfate (PMS)-assisted photocatalytic system is a promising platform for the selective degradation of water contaminants. However, achieving an effective electron transport and enhanced separation efficiency for these metal species is a daunting challenge. Thus, our current study addresses this challenge by using a Co-Fe-based layered-double-hydroxide template to synthesize a Co3O4/FeCo2O4 p-n heterojunction composite via a simple monosynthetic route. The resultant composite is thoroughly validated through advanced characterization techniques that efficiently activate PMS for sulfadiazine (SDZ) degradation under visible light, achieving a remarkable degradation efficiency of up to 90%. This accomplishment is attributed to factors including intimate interfacial contact, excellent light harvesting, mesoporosity, and oxygen vacancies within the composite. The formation of a distinct p-n heterojunction following the S-scheme charge dynamic significantly enhances photogenerated carrier separation and reduces charge recombination. The research delves into comprehensive investigations including degradation studies, active species trapping experiments, parameter exploration, and in-depth liquid chromatography-mass spectrometry for analysis of the degradation byproducts and pathway. Induced oxygen vacancies, strategically placed active surface sites, and mesoporosity in the Co3O4/FeCo2O4 composite synergistically boosted the sluggish PMS activation, leading to enhanced SDZ degradation. This study introduces a new perspective by demonstrating the potential of a single-material, mixed-metal oxide-based p-n heterojunction photocatalytic system following the S-scheme charge-transfer route for SDZ degradation. The findings contribute toward emphasizing the importance of tailored composite materials in tackling persistent contaminants.

Full-Spectrum Utilization of ZIF-67/Ag NPs/NaYF4 :Yb,Er Photocatalysts for Efficient Degradation of Sulfadiazine: Upconversion Mechanism and DFT Calculation

In this work, novel ternary composite ZIF-67/Ag NPs/NaYF4 :Yb,Er is synthesized by solvothermal method. The photocatalytic activity of the composite is evaluated by sulfadiazine (SDZ) degradation under simulated sunlight. High elimination efficiency of the composite is 95.4% in 180 min with good reusability and stability. The active species (h+ , ·O2 - and ·OH) are identified. The attack sites and degradation process of SDZ are deeply investigated based on theoretical calculation and liquid chromatography-mass spectrometry analysis. The upconversion mechanism study shows that favorable photocatalytic effectiveness is attributed to the full utilization of sunlight through the energy transfer upconversion process and fluorescence resonance energy transfer. Additionally, the composite is endowed with outstanding light-absorbing qualities and effective photogenerated electron-hole pair separation thanks to the localized surface plasmon resonance effect of Ag nanoparticles. This work can motivate further design of novel photocatalysts with upconversion luminescence performance, which are applied to the removal of sulphonamide antibiotics in the environment.

Efficient degradation of ciprofloxacin in wastewater by CuFe2O4/CuS photocatalyst activated peroxynomosulfate

In this study, CuFe2O4/CuS composite photocatalysts were successfully synthesized for the activation of peroxynomosulfate to remove ciprofloxacin from wastewater. The structural composition and morphology of the materials were analyzed by XRD, SEM, TEM, and Raman spectroscopy. The electrochemical properties of the samples were tested by an electrochemical workstation. The band gap of the samples was calculated by DFT and compared with the experimental values. The effects of different catalysts, oxidant PMS concentrations, and coexisting ions on the experiments were investigated. The reusability and stability of the photocatalysts were also investigated. The mechanism of the photocatalytic degradation process was proposed based on the free radical trapping experiment. The results show that the p-p heterojunction formed between the two contact surfaces of the CuFe2O4 nanoparticle and CuS promoted the charge transfer between the interfaces and inhibited the recombination of electrons and holes. CuFe2O4-5/CuS photocatalyst has the best catalytic activity, and the removal rate of ciprofloxacin is 93.7%. The intermediates in the degradation process were tested by liquid chromatography-mass spectrometry (LC-MS), and the molecular structure characteristics of ciprofloxacin were analyzed by combining with DFT calculations. The possible degradation pathways of pollutants were proposed. This study reveals the great potential of the photocatalyst CuFe2O4/CuS in the activation of PMS for the degradation of ciprofloxacin wastewater.

A floating photocatalytic fabric integrated with a AgI/UiO-66-NH2 heterojunction as a facile strategy for wastewater treatment

With an increased need of wastewater treatment, application of photocatalysts has drawn growing research attention as an advanced water remediation strategy. Herein, a floating photocatalytic fabric in a woven construction was developed for removal of Rhodamine B (RhB) in water. For an efficient photocatalytic reaction, AgI nanoparticles were grown on the surface of UiO-66-NH2 crystals in a layered structure, forming a heterojunction system on a cotton yarn, and this was woven with polypropylene yarn. The floating photocatalyst demonstrated the maximized light utilization and adequate contact with contaminated water. Through the heterojunction system, the electrons and holes were effectively separated to generate reactive chemical species, and this eventually led to an enhanced photocatalytic performance of AgI/UiO@fabric reaching 98% removal efficiency after 2 hours of irradiation. Photodegradation of RhB occurred mainly by superoxide radicals and holes, which were responsible for de-ethylation and decomposition of an aromatic ring, respectively. The kinetics of the photocatalytic reaction suggested that circulation of solution by stirring affected the photocatalytic removal rate. The recycle test demonstrated the potential long-term applicability of the developed material with structural integrity and catalytic stability. This study highlights the proof-of-concept of a floating photocatalytic material for facile and effective water remediation with repeated usability.

Reasonable decoration of CuO/Cd0.5Zn0.5S nanoparticles onto flower-like Bi5O7I as boosted step-scheme photocatalyst for reinforced photodecomposition of bisphenol A and Cr(VI) reduction in wastewater

Building S-scheme heterostructures is a sophisticated approach to receiving outstanding catalysts for environmental detoxification. Herein, ternary CuO/Cd0.5Zn0.5S/Bi5O7I (CO/CZS/BOI) nanocomposites were constructed by in-situ decorating of CuO and Cd0.5Zn0.5S nanoparticles onto Bi5O7I micro-sphere in a facile route. The optimal CO/CZS/BOI reflected reinforced bisphenol A (BPA) photo-oxidation (95% in 70 min) and Cr(VI) photo-reduction (96.6 in 60 min) under visible light. Besides, CO/CZS/BOI afforded 5.10 (4.44), 4.42 (3.71), and 6.60 (5.27) fold reinforcement in the BPA (Cr(VI)) photo-reaction rate compared to BOI, CZS, and CO, respectively. This behavior was linked to the development of S-scheme mechanisms resulting from the co-effects of BOI, CZS, and CO in retaining the optimum redox capacity, facilitating the dissolution of photo-carriers, increasing reactive sites, and strengthening the visible-light response. The parameters influencing the catalytic reaction of CO/CZS/BOI, such as light intensity, catalyst dosage, and pH, were deeply studied. The quenching tests declared the prominent roles •O2- and •OH in the breaking down of BPA and the participation of electrons and •O2- in the photocatalytic conversion of Cr(VI). The cyclic tests verified the robust photostability of CO/CZS/BOI, which is associated with the reintegration process between the free h+ coming from CZS and the photo-induced e- of CO and BOI in the S-scheme system. In conclusion, the present study provides a profound understanding of the photo-reaction mechanism of CO/CZS/BOI and introduces a novel concept for constructing a superior dual-Scheme system for efficient wastewater detoxification.

Oxygen Vacancy-Mediated CuWO4/CuBi2O4 Samples with Efficient Charge Transfer for Enhanced Catalytic Activity toward Photodegradation of Pharmacologically Active Compounds

Photocatalytic degradation is a promising method for controlling the increasing contamination of the water environment due to pharmacologically active compounds (PHACs). Herein, oxygen vacancy (OV)-modulated Z-scheme CuWO4/CuBi2O4 hybrid systems were fabricated via thermal treatment by loading of CuWO4 nanoparticles with OVs on CuBi2O4 surfaces. The synthesized CuWO4/CuBi2O4 hybrid samples exhibited an enhanced photodegradation ability to remove PHACs under visible-light irradiation. More importantly, an optimized sample (10 wt % CuWO4/CuBi2O4) exhibited superior catalytic activity and excellent recycling stability for PHAC photodegradation. In addition, possible degradation paths for PHAC removal over the CuWO4/CuBi2O4 hybrid systems were proposed. The enhanced photocatalytic performance could be attributed to the efficient separation and transfer of photoformed charge pairs via the Z-scheme mechanism. This Z-scheme mechanism was systematically analyzed using trapping experiments of active species, ultraviolet photoelectron spectroscopy, electron spin resonance, and the photodepositions of noble metals. The findings of this study can pave the way for developing highly efficient Z-scheme photocatalytic systems for PHAC photodegradation.

Boosting Exciton Dissociation and Charge Transfer in Triazole-Based Covalent Organic Frameworks by Increasing the Donor Unit from One to Two for the Efficient Photocatalytic Elimination of Emerging Contaminants

As novel photocatalysts, covalent organic frameworks (COFs) have potential for water purification. Insufficient exciton dissociation and low charge mobility in COFs yet restricted their photocatalytic activity. Excitonic dissociation and charge transfer in COFs could be optimized via regulating the donor-acceptor (D-A) interactions through adjusting the number of donor units within COFs, yet relevant research is lacking. By integrating the 1,2,4-triazole or bis-1,2,4-triazole unit with quinone, we fabricated COF-DT (with a single donor unit) and COF-DBT (with double donor units) via a facile sonochemical method and used to decontaminate emerging contaminants. Due to the stronger D-A interactions than COF-DT, the exciton binding energy was lower for COF-DBT, facilitating the intermolecular charge transfer process. The degradation kinetics of tetracycline (model contaminant) by COF-DBT (k = (12.21 ± 1.29) × 10-2 min-1) was higher than that by COF-DT (k = (5.11 ± 0.59) × 10-2 min-1) under visible-light irradiation. COF-DBT could efficiently photodegrade tetracycline under complex water chemistry conditions and four real water samples. Moreover, six other emerging contaminants, both Gram-negative and Gram-positive strains, could also be effectively eliminated by COF-DBT. High tetracycline degradation performance achieved in a continuous-flow system and in five reused cycles in both laboratory and outdoor experiments with sunlight irradiation showed the stability and the potential for the practical application of COF-DBT.

Key role of Fe(VI)-activated Bi2WO6 in the photocatalytic oxidation of sulfonamides: Mediated electron transfer mechanism

The widespread use of sulfonamides (SAs) in animals and human infections has raised significant concerns regarding their presence in ambient waterways and potential for inducing antimicrobial resistance. Herein, we report on the capacity of ferrate (VI) (Fe^VIO₄^2-, Fe(VI)) to facilitate the photocatalytic degradation of sulfamethazine (SMT) via bismuth tungstate (Bi₂WO₆, BWO) under blue LED light (Vis/BWO/Fe(VI)) exposure, at rates that were 45-fold faster than BWO photocatalysis. Both the stepwise and time-series addition of Fe(VI) contributed to the degradation. Multiple lines of evidence confirmed that the common reactive species (RSs) in BWO-based photocatalytic systems and Fe(VI)-involved systems (e.g., •OH/h⁺, O₂^•-, ¹O₂ and Fe(V)/Fe(IV)) played subtle roles in our study system. Herein, for the first time, it was discovered that the precursor complex (BWO-Fe(V)/Fe(IV)* )) was the main contributor to induce electron transfer of SAs through the "conductive bridge" effect of BWO. The studied system was able to effectively degrade SMT in synthetic hydrolyzed urine (SHU) with low interference from background substances in water. This work not only offers a novel facilitation strategy for BWO, but also holds a great application prospect for contamination remediation in urine.

Direction regulation of interface carrier transfer and enhanced photocatalytic oxygen activation over Z-scheme Bi4V2O11/Ag/AgCl for water purification

Molecular oxygen activation is essential to the photocatalytic oxidation reaction, which is highly dependent on the construction of active sites and efficient charge transfer of photocatalysts. In this study, we constructed Bi₄V₂O₁₁/Ag/AgCl Z-type heterojunction photocatalysts with significantly enhanced molecular oxygen activation capacity. The systematic characterization and analysis including X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations confirmed that the formation of efficient Z-type heterostructure could be attributed to the introduction of Ag nanoparticles (NPs), which regulated the electron transfer direction from Bi₄V₂O₁₁ to AgCl. Owing to the advantage of enhanced charge transfer efficiency, the O₂^- generation capacity of Bi₄V₂O11/Ag/AgCl Z-scheme heterojunction was as high as 4.6 times that of pure Bi₄V₂O₁₁. Consequently, Bi₄V₂O₁₁/Ag/AgCl showed good degradation performance against tetracycline (TC), ciprofloxacin (CIP), ranitidine hydrochloride (RAN) and 2,4-dichlorophenoxyacetic acid (2,4-D) under visible light, and their degradation rates were 8.2 times, 5.9 times, 3.8 times and 11.9 times higher than those of Bi₄V₂O₁₁, respectively. This study provides an effective and feasible strategy to design photocatalyst with improved molecular oxygen activation efficiency.

Bismuth-based nanostructured photocatalysts for the remediation of antibiotics and organic dyes

A serious threat to human health and the environment worldwide, in addition to the global energy crisis, is the increasing water pollution caused by micropollutants such as antibiotics and persistent organic dyes. Nanostructured semiconductors in advanced oxidation processes using photocatalysis have recently attracted a lot of interest as a promising green and sustainable wastewater treatment method for a cleaner environment. Due to their narrow bandgaps, distinctive layered structures, plasmonic, piezoelectric and ferroelectric properties, and desirable physicochemical features, bismuth-based nanostructure photocatalysts have emerged as one of the most prominent study topics compared to the commonly used semiconductors (TiO₂ and ZnO). In this review, the most recent developments in the use of photocatalysts based on bismuth (e.g., BiFeO₃, Bi₂MoO₆, BiVO₄, Bi₂WO₆, Bi₂S₃) to remove dyes and antibiotics from wastewater are thoroughly covered. The creation of Z-schemes, Schottky junctions, and heterojunctions, as well as morphological modifications, doping, and other processes are highlighted regarding the fabrication of bismuth-based photocatalysts with improved photocatalytic capabilities. A discussion of general photocatalytic mechanisms is included, along with potential antibiotic and dye degradation pathways in wastewater. Finally, areas that require additional study and attention regarding the usage of photocatalysts based on bismuth for removing pharmaceuticals and textile dyes from wastewater, particularly for real-world applications, are addressed.

Anchoring black phosphorous quantum dots on Bi2WO6 porous hollow spheres: A novel 0D/3D S-scheme photocatalyst for efficient degradation of amoxicillin under visible light

Reasonable regulation of the micro-morphology of material can significantly enhance the related performance. Herein, bismuth tungstate (Bi₂WO₆, simplified as BWO) porous hollow spheres with flower-like surface were prepared successfully, and this unique morphology endowed BWO with improved photocatalytic performance by reflecting and absorbing the light multiple times inside the cavity. To inhibit the rapid recombination of photogenerated e^--h⁺ pairs within BWO itself, black phosphorous quantum dots (BPQDs) were anchored onto the nanosheets of BWO sphere closely by a facile self-assembly process, which will not shade the pores of BWO owing to the small size of BPQDs, but the BP nanosheets have the chance to do that. The band gap of BPQDs expanded much after exfoliation due to the quantum confinement effects, which matched the energy band of BWO well to form S-scheme heterojunction, achieving more efficient separation of photogenerated charges. As a result, the BPQDs/BWO exhibited attractive photocatalytic performance in the degradation of amoxicillin (AMX) and other antibiotics. Besides, the operation conditions were optimized, specifically, 94.5 % of AMX (20 mg/L, 200 mL) can be removed in 60 min when 50 mg of 2BPQDs/BWO was used as catalyst with solution pH = 11. Moreover, a possible degradation pathway of AMX was proposed based on the detected intermediates.

Modulation of Z-scheme photocatalysts for pharmaceuticals remediation and pathogen inactivation: Design devotion, concept examination, and developments

The recent outbreak of Covid-19 guarantees overconsumption of different drugs as a necessity to reduce the symptoms caused by this pandemic. This triggers the proliferation of pharmaceuticals into drinking water systems. Is there any hope for access to safe drinking water? Photocatalytic degradation using artificial Z-scheme photocatalysts that has been employed for over a decade conveys a prospect for sustainable clean water supply. It is compelling to comprehensively summarise the state-of-the-art effects of Z-scheme photocatalytic systems towards the removal of pharmaceuticals in water. The principle of Z-scheme and the techniques used to validate the Z-scheme interfacial charge transfer are explored in detail. The application of the Z-scheme photocatalysts towards the degradation of antibiotics, NSAIDs, and bacterial/viral inactivation is deliberated. Conclusions and stimulating standpoints on the challenges of this emergent research direction are presented. The insights and up-to-date information will prompt the up-scaling of Z- scheme photocatalytic systems for commercialization.

Graphene shell-encapsulated copper-based nanoparticles (G@Cu-NPs) effectively activate peracetic acid for elimination of sulfamethazine in water under neutral condition

In this study, a graphene shell-encapsulated copper-based nanoparticles (G@Cu-NPs) was prepared and employed for peracetic acid (PAA) activation. The characterization of G@Cu-NPs confirmed that the as-prepared material was composed of Cu⁰ and Cu₂O inside and encapsulated by a graphene shell. Experimental results suggested that the synthesized G@Cu-NPs could activate PAA to generate free radicals for efficiently removing sulfamethazine (SMT) under neutral condition. The formation of graphene shells could strongly facilitated electron transfer from the core to the surface. Radical quenching experiments and electron spin resonance (ESR) analysis confirmed that organic radicals (R-O•) and hydroxyl radicals (•OH) were generated in the G@Cu-NPs/PAA system, and R-O• (including CH₃CO₃• and CH₃CO₂•) was the main contributor to the elimination of SMT. The possible SMT degradation pathways and mechanisms were proposed, and the toxicity of SMT and its intermediates was predicted with the quantitative structure-activity relationship (QSAR) analysis. Besides, the effects of some key parameters, common anions, and humic acid (HA) on the removal of SMT in the G@Cu-NPs/PAA system were also investigated. Finally, the applicability of G@Cu-NPs/PAA system was explored, showing that the G@Cu-NPs/PAA system possessed satisfactory adaptability to treat different water bodies with admirable reusability and stability.

A mechanistic study of the photocatalytic activity of AgI–WO3 in an experimentally designed approach toward methylene blue photodegradation

The visible light-active AgI/WO3 binary photocatalyst has been characterized using XRD, FTIR spectroscopy, SEM-EDX, cyclic voltammetry (CV), photoluminescence (PL), and UV–vis DRS techniques.

Calcination-Induced Oxygen Vacancies Enhancing the Photocatalytic Performance of a Recycled Bi2O3/BiOCl Heterojunction Nanosheet

With the rapid development of industry, bismuth-based semiconductors have been widely used for the photocatalytic degradation of organic contaminants discharged into wastewater. Herein, a Bi₂O₃/BiOCl (BBOC) heterojunction was constructed with high photocatalytic activity toward Rhodamine B (RhB) in the first cycle of the photocatalysis test, while the photocatalytic performance was drastically reduced after repeated testing. The adsorbed RhB molecules occupying the facial active sites of BBOC contributed to the decline of photocatalytic activity. The spent BBOC can be reactivated by the decomposition of the adsorbed RhB and the introduction of oxygen vacancies during calcination under an air atmosphere. The BBOC thus recovered exhibited a superior apparent rate constant of 0.08087 min^-1 compared with 0.05228 min^-1 of pristine BBOC. This study provided an effective strategy to investigate the deactivation/activation mechanism of bismuth-based heterojunction photocatalysts.

Antibacterial Z-scheme ZnIn2S4/Ag2MoO4 composite photocatalytic nanofibers with enhanced photocatalytic performance under visible light

Considering the biocompatibility of natural proteins and the strong photo-redox capability of Z-scheme heterojunctions, we fabricated Z-scheme ZnIn₂S₄/Ag₂MoO₄@Zein (Z ZA) photocatalytic membranes via electrospinning and in-situ precipitation for enrofloxacin (ENR) degradation. Z ZA exhibit a fiber structure wrapped with ZnIn₂S₄/Ag₂MoO₄ heterojunctions. Photocatalytic studies and various characterization results certified that the Z-scheme structure between ZnIn₂S₄ and Ag₂MoO₄ significantly increases the lifetime and separation efficiency of photogenerated carriers, which in turn enhances the photodegradation of ENR. The degradation rate of Z ZA-10 (ZnIn₂S₄/10 wt% Ag₂MoO₄@Zein) with the highest catalytic activity could reach 100% within 120 min compared with other samples. For ENR degradation, •O₂^- radicals were certified to be the primary active species by trapping experiments, and several possible conversion pathways of ENR in photocatalytic reactions were proposed. Furthermore, the antibacterial rates of Z ZA-20 (ZnIn₂S₄/20 wt% Ag₂MoO₄@Zein) against B. subtilis, P. aeruginosa, S. aureus, and E. coli could reach 90.09%, 89.78%, 84.34%, and 95.31%, respectively. Antibacterial evaluations and cytotoxicity assays demonstrated that Z ZA photocatalytic films had desirable antibacterial properties and low cytotoxicity, rendering them safe and effective for use in the treatment of antibiotic wastewater.

Synthesis characterization of Zn-based MOF and their application in degradation of water contaminants

Metal-organic frameworks (MOFs) are currently popular porous materials with research and application value in various fields such as medicine and engineering. Aiming at the application of MOFs in photocatalysis, this paper mainly reviews the main synthesis methods of ZnMOFs and the latest research progress of Zn MOF-based photocatalysts to degrade organic pollutants in water, such as organic dyes. This nanomaterial is being used to treat wastewater and has proven to be very efficient because of its exceptionally large surface area and porous nature. The results show that Zn-MOFs are capable of high degradation of the above pollutants and over 90% of degradation was observed in publications. In addition, the reusability percentage was examined and studies showed that the Zn-MOF nanostructure has very good stability and can continue to degrade a high percentage of pollutants after several cycles. This review focuses on Zn-MOFs and their composites. First, the methods of synthesis and characterization of these compounds are given. Finally, the application of these composites in the process of photocatalytic degradation of dye pollutants such as methylene blue, methyl orange, crystal violet, rhodamine B, etc. is explained.

Immobilized BiOCl0.75I0.25/g-C3N4 nanocomposites for photocatalytic degradation of bisphenol A in the presence of effluent organic matter

The BiOCl_0.75I_0.25/g-C₃N₄ nanosheet (BCI-CN) was successfully immobilized on polyolefin polyester fiber (PPF) through the hydrothermal method. The novel immobilized BiOCl_0.75I_0.25/g-C₃N₄ nanocomposites (BCI-CN-PPF) were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy EDS, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS) to confirm that BCI-CN was successfully immobilized on PPF with abundant oxygen vacancies reserved. Under simulated solar light irradiation, 100 % of bisphenol A (BPA) with an initial concentration of 10 mg·L^-1 was degraded by BCI-CN-PPF (0.2 g·L^-1 of BCI-CN immobilized) after 60 min. A similar photocatalytic efficiency of BPA was obtained in the presence of effluent organic matter (EfOM). The photocatalytic degradation of BPA was not affected by EfOM <5 mg-C/L. In comparison, the photocatalytic performance was considerably inhibited by EfOM with a concentration of 10 mg-C/L. Furthermore, photogenerated holes and superoxide radicals predominated in the photocatalytic degradation processes of BPA. The total organic carbon (TOC) removal efficiencies of BPA and EfOM were 75.2 % and 50 % in the BCI-CN-PPF catalytic system. The BPA removal efficiency of 94.9 % was still achieved in the eighth cycle of repeated use. This study provides a promising immobilized nanocomposite with high photocatalytic activity and excellent recyclability and reusability for practical application in wastewater treatment.

An innovative S-scheme AgCl/MIL-100(Fe) heterojunction for visible-light-driven degradation of sulfamethazine and mechanism insight

The development of high efficient photocatalysts for antibiotics contamination in water remains a severe challenge. In this study, a novel step-scheme (S-scheme) photocatalytic heterojunction nanocomposites were fabricated from integrating AgCl nanoparticles on the MIL-100(Fe) octahedron surface through facile multi-stage stirring strategy. The S-scheme heterojunction structure in AgCl/MIL-100(Fe) (AM) nanocomposite provided a more rational utilization of electrons (e^-) and holes (h⁺), accelerated the carrier transport at the junction interface, and enhanced the overall photocatalytic performance of nanomaterials. The visible-light-driven photocatalysts were used to degrade sulfamethazine (SMZ) which attained a high removal efficiency (99.9%). The reaction mechanisms of SMZ degradation in the AM photocatalytic system were explored by electron spin resonance (ESR) and active species capture experiments, which superoxide radical (•O₂^-), hydroxyl radical (•OH), and h⁺ performed as major roles. More importantly, the SMZ degradation pathway and toxicity assessment were proposed. There were four main pathways of SMZ degradation, including the processes of oxidation, hydroxylation, denitrification, and desulfonation. The toxicity of the final products in each pathway was lower than that of the parent according to the toxicity evaluation results. Therefore, this work might provide new insights into the environmentally-friendly photocatalytic processes of S-scheme AM nanocomposites for the efficient degradation of antibiotics pollutants.

Novel sphere-like copper bismuth oxide fabricated via ethylene glycol-introduced solvothermal method with improved adsorptive and photocatalytic performance in sulfamethazine removal

In this research, ethylene glycol-introduced solvothermal method was employed to fabricate a novel sphere-like CuBi₂O₄ material to improve the adsorptive and photocatalytic performance of conventional CuBi₂O₄. A series of characterization has been applied to investigate properties of the obtained CuBi₂O₄ (CBO-EG3). Compared with conventional rod-like CuBi₂O₄ (CBO), the synthesized sphere-like CBO-EG3 exhibited rough surface, larger specific surface area, and more effective separation of photo-generated carriers, which overcome main shortcomings of CuBi₂O₄. The removal efficiency of typical antibiotic sulfamethazine (SMZ) reached almost 100% under the optimal experimental conditions. About 70% of SMZ could be adsorbed in 180-min dark reaction, with residual being photodegraded in 30 min. CBO-EG3 showed much higher photocatalytic efficiency than pure CBO, attributing to its highly effective photo-induced electron and hole separation. Meanwhile, substantial adsorption of pollutant on CBO-EG3 contributed vastly to removal of SMZ, photo-generated electrons and holes inclined to react with adsorbed SMZ directly, and photocatalytic process was mainly led by non-radical reaction. Elimination of SMZ in actual water samples and recycling experiment were also performed to evaluate CBO-EG3's practical application potential. This study delivered a method to promote CuBi₂O₄'s adsorptive and photocatalytic ability, which could expand the application of CuBi₂O₄ in wastewater treatment.

Synergistic introduction of oxygen vacancy and silver/silver iodide: Realizing deep structure regulation on bismuth oxybromide for robust carbon dioxide reduction and pollutant oxidation

To efficiently solve severe energy shortage and environmental pollution issues, step-scheme (S-scheme) photocatalytic system, as perfect photocatalyst with strong redox ability and swift separation efficiency of carriers, has been considered a feasible tactic. Herein, a novel S-scheme silver/silver iodide/bismuth oxybromide heterojunction with rich oxygen vacancies (OVs) (labeled as Ag/AgI/BiO_1-xBr) was in situ fabricated via a simple photodeposition-precipitation method. It was discovered that the obtained Ag/AgI/BiO_1-xBr heterojunction with the optimized molar ratio of silver/bismuth (Ag/Bi) at 0.4 presented excellent photocatalytic properties for carbon dioxide (CO₂) reduction (2.46 μmol g^-1h^-1 carbon monoxide (CO) and 1.25 μmol g^-1h^-1 methane (CH₄) generation) and antibiotic tetracycline (TC) removal (96.7%) even in actual waste water or in the presence of electrolytes. The enhanced performance of S-scheme Ag/AgI/BiO_1-xBr composite may be ascribed to the collaborative effect of OVs and silver/silver iodide (Ag/AgI), in which OVs acted as the charge transmission bridge for reducing the interface migration resistance of the charge and Ag/AgI served as a cocatalyst for enhancing the separation efficiency of carriers. Furthermore, a feasible photocatalytic mechanism was discussed via density functional theory calculation and in-situ X-ray photoelectron spectroscopy. This work not only demonstrated the synergistic application of OVs transmission bridge and Ag/AgI cocatalyst, but also provided a facile way to design high-efficiency and stable photocatalysts for energy production and environmental remediation.

Mechanism for biodegradation of sulfamethazine by Bacillus cereus H38

Degradation of sulfonamides (SAs) by microorganisms has become a focus of current research. Sulfamethazine (SMZ) is a type of SA widely used in the livestock and poultry industry. However, understanding the intermediate products, degradation pathways and mechanism of SMZ biodegradation is limited at present. In this study, a SMZ degrading bacterium Bacillus cereus H38, which can use SMZ as its only carbon source, was isolated from farmland soil. The bacterium was gram-positive with rod-shaped cells. The effects of initial SMZ concentration, pH, temperature and amount of inoculation on the biodegradation of SMZ were investigated by a single factor experiment. The results showed that the maximum degradation rate of SMZ was achieved in the environmental conditions at an initial SMZ concentration of 5 mg/L, pH of 7.0, temperature of 25 °C and inoculation amount of 5%. Under these optimum degradation conditions, strain H38 can completely degrade SMZ within 3 days. The effects of intracellular enzymes, extracellular enzymes and periplasmic enzymes on the SMZ degradation process were compared. It was found that intracellular enzymes contributed the most to the biodegradation of SMZ, and the degradation rate approached 70%. Three possible intermediates were identified by LC-MS/MS, and two degradation pathways were proposed. Whole genome sequencing results showed that the genome size of strain H38 was 5,477,631 bp, including 5599 coding sequences (CDSs), and the GC content was 35.21%. In addition, functional annotation of CDSs was performed to analyze the metabolic pathways of nitrogen and sulfur in strain H38 combining genomics and bioinformatics. This study proposes new insights into the mechanism for biodegradation of SAs and will inform future research.

Biomimetic nitrogen-rich photocatalyst based on cadmium sulfide for photocatalytic hydrogen evolution

A novel N-rich sugarcane-like photocatalyst CdS/C₃N₅ (CCN) was prepared by a thermal polymerization method and tested for generating H₂ and realizing antiphotocorrosive performance. The best photocatalytic H₂ evolution is obtained for a CdS to C₃N₅ mass ratio of 1:1 (CCN3), which is nearly 33 and 3 times higher than that of pure C₃N₅ and CdS, respectively. CCN3 can be used to effectively reduce CdS photocorrosion and increase stability because of its N-rich performance and sugarcane-like structure, which can affect electron transport and enhance the internal binding force, respectively. CCN3 can maintain a high H₂ evolution ability after 5 cycles, while still maintaining the original sugarcane-like shape, which has an anti-photocorrosive ability.