A novel Z-Scheme CdS/Bi3O4Cl heterostructure for photocatalytic degradation of antibiotics: Mineralization activity, degradation pathways and mechanism insight

Direct evolution of an alkaline fungal laccase to degrade tetracyclines

A fungal laccase-mediator system capable of high effectively oxidizing tetracyclines under a wide pH range will benefit environmental protection. This study reported a directed evolution of a laccase PIE5 to improve its performance on tetracyclines oxidization at alkaline conditions. Two mutants, namely MutA (D229N/A244V) and MutB (N123A/D229N/A244V) were obtained. Although they shared a similar optimum pH and temperature as PIE5, the two mutants displayed approximately 2- and 5-fold higher specific activity toward the mediators ABTS and guaiacol at pHs 4.0 to 6.5, respectively. Simultaneously, their catalytic efficiency increased by 8.0- and 6.4-fold compared to PIE5. At a pH range of 5-8 and 28 °C, MutA or MutB at a final concentration of 2.5 U·mL-1 degraded 77 % and 81 % of 100 mg·L-1 tetracycline within 10 min, higher than PIE5 (45 %). Furthermore, 0.1 U·mL-1 MutA or MutB completely degraded 100 mg·L-1 chlortetracycline within 6 min in the presence of 0.1 mM ABTS. At pH 8.0, MutA degraded tetracycline and chlortetracycline following the routine pathways were reported previously based on LC-MS analysis.

Engineering Mn-Doped CdS Thin Films Through Chemical Bath Deposition for High-Performance Photoelectrochemical Water Splitting

Doping conventional materials with a second element is an exciting strategy for enhancing catalytic performance via electronic structure modifications. Herein, Mn-doped CdS thin films were successfully synthesized with the aid of the chemical bath deposition (CBD) by varying the pH value (8, 10, and 12) and the surfactant amount (20, 40, 60 mg). Different morphologies like nano-cubes, nanoflakes, nano-worms, and nanosheets were obtained under different deposition conditions. The optimized Mn-doped CdS synthesized at pH=8 exhibited better photoelectrochemical (PEC) performance for oxygen evolution reaction (OER) than pure CdS films, with a maximum photocurrent density of 300 μA/cm2 at an external potential of 0.5 V, under sunlight illumination. The observed performance is attributed to the successful Mn doping, porosity, high surface area, and nanosphere morphology.

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.

Visible-light-driven photo-peroxidase catalysis: high-efficiency degradation of indole in water

The demand for H2O2 restricts the wider application of horseradish peroxidase (HRP) in degradation. In this work, a novel photoenzyme synergistic catalytic system was developed for high-efficiency degrading of indole in water by HRP without extra H2O2. The HRP was immobilized on CN-ZIF prepared by the combination of g-C3N4 and ZIF-8 to achieve photo-peroxidase catalyst HRP/Zn-CN-ZIF. Under visible light, photogenerated electrons and H2O2 from HRP/Zn-CN-ZIF participated in the biocatalytic cycle of HRP directly. As a result, the indole at 20 mg L-1 in water was degraded completely in 2 h by the HRP/Zn-CN-ZIF photoenzyme synergistic catalytic system without the addition of H2O2. Furthermore, HRP/Zn-CN-ZIF exhibited superior visible light absorption and charge transfer ability compared to g-C3N4. The results of the mechanism studies suggest that ·OH would play the most significant role from the HRP/Zn-CN-ZIF in indole degradation. This research provides an efficient approach for the removal of indole from water environments.

A novel Z-type heterojunction Bi3O4Cl/Bi4O5I2 photocatalytic composite with broad-spectrum antibacterial activity and degradation properties

At present, the sustainable development of humans is facing health problems and ecological imbalance caused by environmental pollution. To solve the bacteria, antibiotics and other pollutants in wastewater, Bi3O4Cl and Bi4O5I2 with appropriate bandgap width were selected to prepare Z-type heterojunction Bi3O4Cl/Bi4O5I2 photocatalytic materials by calcination method. Under LED light, the best sample Bi3O4Cl/Bi4O5I2-4 could completely inactivate Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in 30 min, Bacillus subtilis (B. subtilis) and Pseudomonas aeruginosa (P. aeruginosa) in 20 min, and degrade 70.6% of tetracycline (TC) and 97.4% of Rhodamine B (RhB). Photocurrent and electrochemical impedance tests (EIS) confirmed the high photocurrent response and low charge transfer resistance in the Bi3O4Cl/Bi4O5I2. The photocatalytic antibacterial and degradation mechanism of Z-type Bi3O4Cl/Bi4O5I2 heterojunction was verified by capture experiments. Thus, this study provides a compact and efficient photocatalyst with broad-spectrum antibacterial activity and degradation properties.

A Novel Strategy of Combined Pulsed Electro-Oxidation and Electrolysis for Degradation of Sulfadiazine

A combination of the peroxymonosulfate (PMS) electro-activation process and the electro-oxidation process driven by a pulsed electric field (PEF) was used to degrade sulfadiazine (SND) wastewater. Mass transfer is the limiting step of electrochemical processes. The PEF could enhance mass transfer efficiency by reducing the polarization effect and increasing the instantaneous limiting current compared with the constant electric field (CEF), which could benefit the electro-generation of active radicals. The degradation rate of SND after 2 h was 73.08%. The experiments investigated the effects of operating parameters of pulsed power supply, PMS dosage, pH value and electrode inter distance on the degradation rate of SND. The predicted response value of single-factor performance experiments was obtained as 72.26% after 2 h, which was basically consistent with the experimental value. According to the quenching experiments and EPR tests, both SO₄^•- and •OH were present in the electrochemical processes. The generation of active species were significantly greater in the PEF system than that in the CEF system. Moreover, four kinds of intermediate products were detected during the degradation by LC-MS. This paper presents a new aspect for electrochemical degradation of sulfonamide antibiotics.

Cefotaxime degradation by the coupled binary CdS-PbS: characterization and the photocatalytic process kinetics

Increased water pollution due to discharging industrial/urban/hospital wastewater has been adopted to introduce/develop novel removal techniques/catalyst/adsorbent. The hexagonal (wurtzite) CdS and the cubic PbS nanoparticles (NPs) were synthesized, coupled, and supported onto clinoptilolite NPs (CNP). Then, the sample was characterized by X-ray powder diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FTIR), and a scanning electron microscope equipped with an energy dispersive X-ray analyzer (SEM-EDX) techniques. The average crystallite size for CdS NPs, PbS NPs, CNP, and CdS-PbS/CNP samples was obtained at about 24, 36, 27, and 14 nm using the Scherrer formula value of nanometer, by the W-H formula, 31, 17, 39, and 51, respectively. Only a detectable slope can be observed from the DRS spectra for CdS NPs at 591 nm corresponding to an Eg value of 2.1 eV. PbS NPs have a broad abruption peak that begins from the visible region and extends to the IR region of the light. A boosted photocatalytic activity of the supported binary catalysts towards cefotaxime (CT) was reached. An apparent first kinetic model was reached with a k-value of 0.021 min^-1 corresponding to the t_1/2 value of 33 min. A decreased COD trend for the photodegraded CT solutions was reached, and the chemical oxygen demand (COD) results in the Hinshelwood model showed a k-value of 0.016 min^-1, corresponding to a t_1/2 value of 43 min.

Synthesis of MnSe-Based GO Composites as Effective Photocatalyst for Environmental Remediations

In this work, a manganese selenide/graphene oxide (MnSe/GO)-based composite was prepared for wet-chemical assisted method against organic dye; herein, methylene blue (MB) dye removal from the water was employed as a metal selenide-based photocatalyst. The synthesized MnSe/GO composite was systematically characterized by X-ray diffraction (XRD), Fourier transform electron microscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and UV-visible diffuse reflectance spectroscopy (UV-vis. DRS). The structural characteristic revealed the adequate synthesis of the sample with good crystallinity and purity of the obtained products. The morphological analysis indicates the formation of MnSe nanoflakes composed of tiny particles on their surface. At the same time, the GO nanosheets with high aggregation were formed, which may be due to the van der Waals forces. The bond interaction and compositional analysis studies confirmed and supported the structural findings with high purity. The optical analysis showed the bandgap energies of MnSe and their composites MnSe (1.7 eV), 7% GO-MnSe (2.42 eV), 14% GO-MnSe (2.6 eV), 21% GO-MnSe (3.02 eV), and 28% GO-MnSe (3.24 eV) respectively, which increase the bandgap energy after GO and MnSe recombination. Among different contents, the optimized 21% GO-MnSe composite displayed enhanced photocatalytic properties. For instance, a short time of 90 min was taken compared with other concentrations due to the narrow bandgap of MnSe and the highly conductive charge carrier's support, making the process to remove MB from water faster. These results show that the selenide-based photocatalyst can be an attractive candidate for future advanced photocatalysis applications.

Highly efficient solar light-driven BiOX (X=Br/Cl/I) and BiOY heterojunction (Y=Br/Cl) nano photocatalysts in suspended and immobilised forms for malachite green dye wastewater treatment

A novel BiOY (Y = Br/Cl) heterojunction nanocatalyst was synthesised chemically and compared with three different BiOX (X = Br/Cl/I) nanocatalysts as well as a physical admixture of BiOBr/BiOCl catalysts in the photocatalytic degradation of malachite green dye wastewater under solar irradiation in both suspended and immobilised forms using polysulfone as the substrate. Catalyst characterisation was done by a particle size analyser, SEM/EDX, XRD, FTIR, and DRS. In the suspended form, BiOBr showed 100% degradation within 70 min, BiOCl showed 99.3%, and BiOI showed 11.2% degradation within 120 min, and it is found to follow pseudo-first-order kinetics. In the immobilised form, BiOBr showed 89.1%, and BiOCl showed 83.4% degradation within 180 min under sunlight. The degradation measured by TOC reduction for these catalysts in suspended form was 67.4%, 57%, and 40%, affirming BiOBr as the best among these catalysts. The performance of the immobilised chemically synthesised BiOY and physical admixture catalysts were 88% and 14%, respectively. The enhanced activity in the chemically synthesised immobilised BiOBr/Cl catalyst can be attributed to the effective charge separation at the heterojunction interface. These photocatalysts are very active under solar light and hence suitable for the efficient degradation of other recalcitrant organic contaminants.

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.

The boosted photocatalytic effects of a zeolite supported CdS towards an antibiotic model pollutant: a brief kinetics study

In recent decades, increased world population and industrial activities explosively polluted our environment, especially the aquatic resources. This requires introducing/developing novel methods to decrease the pollution extent of such resources. Here, the hexagonal (wurtzite) CdS nanoparticles (NPs) were synthesized and supported onto ball-mill prepared clinoptilolite NPs (CNP). Samples were briefly characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscope equipped with an energy dispersive X-ray analyzer (SEM-EDX), and diffuse reflectance spectroscopy (DRS) techniques. The average crystallite size for CdS NPs and CdS-CNP samples was estimated to be about 9.0 nm and 12.3 nm (from the Scherrer formula) and about 19.7 and 17.5 nm (from the Williamson-Hall model), respectively. From the DRS spectra, the absorption wavelengths of 595 and 546 nm correspond to band gap energies of 2.08, and 2.27 eV was obtained for CdS NPs and CdS-CNP samples. The samples were then used in the photodegradation of cefotaxime (CT), and the results showed a boosted photocatalytic activity for CdS-CNP rather than CdS NPs. The photodegradation process obeyed the pseudo-first-order kinetic model, and the CdS and CdS-CNP catalysts obtained the k-values of 0.013 min^-1 and 0.023 min^-1. When the photodegraded CT solutions were used in COD experiments, the k-values changed to 0.011 min^-1 and 0.029 min^-1, respectively. The zeolite support is an eco-friendly natural zeolite with abundant deposits in Iran that yields a cost-effective method.

Checking the Efficiency of a Magnetic Graphene Oxide–Titania Material for Catalytic and Photocatalytic Ozonation Reactions in Water

An easily recoverable photo-catalyst in solid form has been synthesized and applied in catalytic ozonation in the presence of primidone. Maghemite, graphene oxide and titania (FeGOTi) constituted the solid. Additionally, titania (TiO2) and graphene oxide–titania (GOTi) catalysts were also tested for comparative reasons. The main characteristics of FeGOTi were 144 m2/g of surface area; a 1.29 Raman D and G band intensity ratio; a 26-emu g−1 magnetic moment; maghemite, anatase and brookite main crystalline forms; and a 1.83 eV band gap so the catalyst can absorb up to the visible red region (677 nm). Single ozonation, photolysis, photolytic ozonation (PhOz), catalytic ozonation (CatOz) and photocatalytic ozonation (PhCatOz) were applied to remove primidone. In the presence of ozone, the complete removal of primidone was experienced in less than 15 min. In terms of mineralization, the best catalyst was GOTi in the PhCatOz processes (100% mineralization in 2 h). Meanwhile, the FeGOTi catalyst was the most efficient in CatOz. FeGOTi led, in all cases, to the highest formation of HO radicals and the lowest ozone demand. The reuse of the FeGOTi catalyst led to some loss of mineralization efficacy after four runs, likely due to C deposition, the small lixiviation of graphene oxide and Fe oxidation.

Heterogeneous Cu2O-Au nanocatalyst anchored on wood and its insight for synergistic photodegradation of organic pollutants

In this study, a Cu₂O-Au nanoparticles (NPs) heterojunction catalyst anchored on wood was developed by in situ reduction and hydrothermal treatment, and the properties of the catalyst were systematically characterized. The catalyst exhibited prominent photocatalysis of methyl orange (MO, 0.169 min^{- 1}), and tetracycline (TC, 0.122 min^-1) which were degraded completely within 20 min. Even after four recyclings, the efficiency of MO degradation by the catalyst remained at 80%. The natural wood with three-dimensional porous structures acted as a reducing agent and a stabilizer for Au NPs and Cu₂O, which helped to maintain high performance and reusability. The presence of Au NPs mediated the light-induced electron transfer and enhanced the absorption of visible light for promoting photocatalytic activity. The intermediates of contaminants within the degradation process were characterized by liquid chromatography-mass spectrometry. Additionally, the photogenerated superoxide radicals and holes were identified by electron spin resonance. Thus, the potential degradation mechanism catalyzed by the Cu₂O-Au NPs-wood was proposed. This findings of this study valorizes biomass as a photocatalyst for wastewater remediation.

Impact of Antibiotics as Waste, Physical, Chemical, and Enzymatical Degradation: Use of Laccases

The first traces of Tetracycline (TE) were detected in human skeletons from Sudan and Egypt, finding that it may be related to the diet of the time, the use of some dyes, and the use of soils loaded with microorganisms, such as Streptomyces spp., among other microorganisms capable of producing antibiotics. However, most people only recognise authors dating between 1904 and 1940, such as Ehrlich, Domagk, and Fleming. Antibiotics are the therapeutic option for countless infections treatment; unfortunately, they are the second most common group of drugs in wastewaters worldwide due to failures in industrial waste treatments (pharmaceutics, hospitals, senior residences) and their irrational use in humans and animals. The main antibiotics problem lies in delivered and non-prescribed human use, use in livestock as growth promoters, and crop cultivation as biocides (regulated activities that have not complied in some places). This practice has led to the toxicity of the environment as antibiotics generate eutrophication, water pollution, nutrient imbalance, and press antibiotic resistance. In addition, the removal of antibiotics is not a required process in global wastewater treatment standards. This review aims to raise awareness of the negative impact of antibiotics as residues and physical, chemical, and biological treatments for their degradation. We discuss the high cost of physical and chemical treatments, the risk of using chemicals that worsen the situation, and the fact that each antibiotic class can be transformed differently with each of these treatments and generate new compounds that could be more toxic than the original ones; also, we discuss the use of enzymes for antibiotic degradation, with emphasis on laccases.

Emerging bismuth-based direct Z-scheme photocatalyst for the degradation of organic dye and antibiotic residues

Organic dye and antibiotic residues are some of the key substances that can contaminate the environment due to their wide usage in various industries and modern medicine. The degradation of these substances present in waterbodies is essential while contemplating human health. Photocatalysts (PSs) are promising materials that develop highly reactive species instantly by simple solar energy conversion for degrading the organic dye and antibiotic residues and converting them into nontoxic products. Among numerous semiconductors, the bismuth (Bi)-containing PS has received great attention due to its strong sunlight absorption, facile preparation, and high photostability. Owing to the technology advancement and demerits of the traditional methods, a Bi-containing direct Z-scheme PS has been developed for efficient photogenerated charge carrier separation and strong redox proficiency. In this review, a synthetic Bi-based Z-scheme heterojunction that mimics natural photosynthesis is described, and its design, fabrication methods, and applications are comprehensively reviewed. Specifically, the first section briefly explains the role of various semiconductors in the environmental applications and the importance of the Bi-based materials for constructing the Z-scheme photocatalytic systems. In the successive section, overview of Z-scheme PS are concisely discussed. The fourth and fifth sections extensively explain the degradation of the organic dyes and antibiotics utilizing the Bi-based direct Z-scheme heterojunction. Eventually, the conclusions and future perspectives of this emerging research field are addressed. Overall, this review is potentially useful for the researchers involved in the environmental remediation field as a collection of up-to-date research articles for the fabrication of the Bi-containing direct Z-scheme PS.

ZnO/γ-Fe2O3/Bentonite: An Efficient Solar-Light Active Magnetic Photocatalyst for the Degradation of Pharmaceutical Active Compounds

For applications related to the photocatalytic degradation of environmental contaminants, engineered nanomaterials (ENMs) must demonstrate not only a high photocatalytic potential, but also a low tendency to agglomeration, along with the ability to be easily collected after use. In this manuscript, a two-step process was implemented for the synthesis of ZnO, ZnO/Bentonite and the magnetic ZnO/γ-Fe₂O₃/Bentonite nanocomposite. The synthesized materials were characterized using various techniques, and their performance in the degradation of pharmaceutical active compounds (PhACs), including ciprofloxacin (CIP), sulfamethoxazole (SMX), and carbamazepine (CBZ) was evaluated under various operating conditions, namely the type and dosage of the applied materials, pH, concentration of pollutants, and their appearance form in the medium (i.e., as a single pollutant or as a mixture of PhACs). Among the materials studied, ZnO/Bentonite presented the best performance and resulted in the removal of ~95% of CIP (5 mg/L) in 30 min, at room temperature, near-neutral pH (6.5), ZnO/Bentonite dosage of 0.5 g/L, and under solar light irradiation. The composite also showed a high degree of efficiency for the simultaneous removal of CIP (~98%, 5 mg/L) and SMX (~97%, 5 mg/L) within 30 min, while a low degradation of ~5% was observed for CBZ (5 mg/L) in a mixture of the three PhACs. Furthermore, mechanistic studies using different types of scavengers revealed the formation of active oxidative species responsible for the degradation of CIP in the photocatalytic system studied with the contribution of h⁺ (67%), OH (18%), and ·O₂⁻ (10%), and in which holes (h⁺) were found to be the dominant oxidative species.

Controllable synthesis of a sponge-like Z-scheme N,S-CQDs/Bi2MoO6@TiO2 film with enhanced photocatalytic and antimicrobial activity under visible/NIR light irradiation

Multifunctional photocatalytic surfaces for pollutant degradation and antimicrobial application are often in high demand, however they confront many challenges in charge transfer and light capture ability. In this work, a sponge-like N,S-CQDs/Bi₂MoO₆@TiO₂ film was constructed via hydrothermal technique aiming to solve above problems. As a result, the ternary film showed enhanced photocatalytic efficiency under visible and near-infrared (NIR) light, in which 85.8% and 44.6% of ciprofloxacin (CIP) were degraded after 240 min irradiation with visible and NIR light, respectively. Moreover, the composite film effectively realized photocatalytic sterilization of gram-positive B. subtilis and gram-negative E. coli under visible light irradiation. The bacterial colony decreased significantly from 7.56-log to 1-log cfu/mL after adding the ternary film within 1.5 h. The enhanced photocatalytic efficiency was closely related to both introduction of surface-functional N,S-CQDs and the construction of N,S-CQDs/Bi₂MoO₆@TiO₂ Z-scheme system, in which the transfer efficiency of photoinduced carriers and the light absorption property were significantly improved. We consider that the N,S-CQDs/Bi₂MoO₆@TiO₂ film is promising for the degradation of refractory pollutants and antimicrobial application under visible/NIR light irradiation. The relatively convenient recycling property and excellent photocatalytic performance of the N,S-CQDs/Bi₂MoO₆@TiO₂ film are beneficial for industrial applications.

UV/TiO2 Photocatalysis as an Efficient Livestock Wastewater Quaternary Treatment for Antibiotics Removal

Antibiotics are among the most common pharmaceutical compounds, and they have been extensively used for the prevention and treatment of bacterial diseases for more than 50 years. However, merely a small fraction of antibiotics is metabolized in the body, while the rest is discharged into the environment through excretion, which can cause potential ecological problems and human health risks. In this study, the elimination of seventeen antibiotics from real livestock wastewater effluents was investigated by UV/TiO2 advanced oxidation process. The effect of process parameters, such as TiO2 loadings, solution pHs, and antibiotic concentrations, on the efficiency of the UV/TiO2 process was assessed. The degradation efficiency was affected by the solution pH, and higher removal efficiency was observed at pH 5.8 and 9.9, while the catalyst loading had no significant effect on the degradation efficiency. UV photolysis showed a good removal efficiency of the antibiotics. However, the highest removal efficiency was shown by the UV/photocatalyst system due to their synergistic effects. The results showed that more than 90% of antibiotics were removed by UV/TiO2 system during the 60 min illumination, while the corresponding TOC and COD removal was only 10 and 13%, respectively. The results of the current study indicated that UV/TiO2 advanced oxidation processes is a promising method for the elimination of various types of antibiotics from real livestock wastewater effluents.

0D boron carbon nitride quantum dots decorated 2D Bi4O5I2 as 0D/2D efficient visible-light-driven photocatalysts for tetracyclines photodegradation

A series of 0D boron carbon nitride quantum dots (BCNQDs) modified 2D Bi₄O₅I₂ (0D/2D Bi₄O₅I₂/BCNQDs) composites were synthesized and applied to photodegradation of tetracyclines (TCs), including tetracycline (TC) and oxytetracycline (OTC). The Bi₄O₅I₂/BCNQDs (1) (1 mL BCNQDs) composite exhibits the highest photocatalytic performance for TCs degradation. The degradation rate constants of TC and OTC by the optimal sample were 4.95 and 2.17 times that of Bi₄O₅I₂, respectively. This can be attributed to the fact that the narrow bandgap Bi₄O₅I₂ is the electron acceptor, and the oxygen-containing functional group with the negative charge on BCNQDs can promote the formation of photoexcited holes, which makes the effective separation of photoexcited carriers easier. Furthermore, the active substance (h⁺ and ·O₂^-) is the major active substance for TCs photodegradation. On this basis, the possible photocatalytic reaction mechanism of Bi₄O₅I₂/BCNQDs (1) composite is proposed. This study provides a new idea for 0D/2D interface engineering of BCNQDs heterojunction.

Biomass porous carbon as the active site to enhance photodegradation of oxytetracycline on mesoporous g-C3N4

Graphitic carbon nitride (g-C3N4) is widely used in photocatalytic adsorption and degradation of pollutants, but there are still some problems such as low adsorption performance and high electron-hole recombination efficiency. Herein, we propose a new molten salt assisted thermal polycondensation strategy to synthesize biomass porous carbon (BPC) loaded on g-C3N4 composites (designated as BPC/g-C3N4) with a hollow tubular structure, which had a high surface area and low electron-hole recombination rate. The study shows that the morphology of g-C3N4 changes dramatically from massive to hollow tubular by molten salt assisted thermal polycondensation, which provides a base for the loading of BPC, to construct a highly effective composite photocatalyst. BPC loaded on g-C3N4 could be used as the active site to enhance Oxytetracycline (OTC) removal efficiency by adsorption and with higher electron-hole separation efficiency. As a result, the BPC(5%)/g-C3N4 sample presented the highest photocatalytic degradation efficiency (84%) for OTC degradation under visible light irradiation. The adsorption capacity and photocatalytic reaction rate were 3.67 and 5.63 times higher than that of the g-C3N4, respectively. This work provided a new insight for the design of novel composite photocatalysts with high adsorption and photocatalytic performance for the removal of antibiotic pollutants from wastewater.

Azobenzene-modified Ag/Ag2O/CN photocatalysts with photoresponsive performance for controllable photodegradation of tetracyclines

In this work, an Azo@Ag/Ag₂O/CN composite photocatalyst with light-responsive performance was successfully prepared by precipitation and emulsion polymerization. Azo@Ag/Ag₂O/CN exhibits cis-trans isomerism under different light exposures.

A Z-scheme heterostructure constructed from ZnS nanospheres and Ni(OH)2 nanosheets to enhance the photocatalytic hydrogen evolution

ZnS and Ni(OH)₂ form a Z-scheme heterostructure, and the synergy between them provides a new hydrogen-producing active center for each material.

Mechanism insight into efficient peroxydisulfate activation by novel nano zero-valent iron anchored yCo3O4 (nZVI/yCo3O4) composites

Novel nano zero-valent iron anchored bio-matrix supported Co₃O₄ (nZVI/yCo₃O₄) composites were fabricated for tetracycline (TC) efficient degradation by activating peroxydisulfate (PS). The systematical characterizations verified that the nZVI/yCo₃O₄ composites with magnetism have higher surface area than yCo₃O₄ and pure Co₃O₄, contributing to more accessible active sites. Various catalytic parameters (nZVI mass ratio, leached ions, initial pH, catalyst dosage, PS concentration and coexisting anions) were thoroughly investigated. In nZVI/yCo₃O₄/PS system, 97.6 %, 93.4 % and 77.3 % TC were degraded within 15 min at pH 3.0, 6.0 and 9.0, respectively. Based on four successive degradation runs, the excellent mineralization rate and reusability of nZVI/yCo₃O₄ composites were mainly benefited from the suppressed metals leaching. The PS activated mechanisms were proposed as non-radicals (¹O₂) dominated pattern at acidic conditions and radicals (SO₄-) predominant pattern at alkaline environment, which may be highly related to the electron donating capacity of nZVI at different pH and the M^(n + 1)+/Mⁿ⁺ redox cycling between Fe or Co metal. The plausible degradation routes of TC were presented based on the detected intermediates. Overall, the synthesized heterogeneous nZVI/yCo₃O₄ composites can efficiently active PS at a wide pH range, and further broaden the application of Co-based catalysts in PS activation.

A Mini Review on Bismuth-Based Z-Scheme Photocatalysts

Recently, the bismuth-based (Bi-based) Z-scheme photocatalysts have been paid great attention due to their good solar energy utilization capacity, the high separation rate of their photogenerated hole-electron pairs, and strong redox ability. They are considerably more promising materials than single semiconductors for alleviating the energy crisis and environmental deterioration by efficiently utilizing sunlight to motivate various photocatalytic reactions for energy production and pollutant removal. In this review, the traits and recent research progress of Bi-based semiconductors and recent achievements in the synthesis methods of Bi-based direct Z-scheme heterojunction photocatalysts are explored. The recent photocatalytic applications development of Bi-based Z-scheme heterojunction photocatalysts in environmental pollutants removal and detection, water splitting, CO₂ reduction, and air (NO_x) purification are also described concisely. The challenges and future perspective in the studies of Bi-based Z-scheme heterojunction photocatalysts are discussed and summarized in the conclusion of this mini review.

Dual plasmons-promoted electron-hole separation for direct Z-scheme Bi3O4Cl/AgCl heterojunction ultrathin nanosheets and enhanced photocatalytic-photothermal performance

The dual plasmons (Bi, Ag)-based direct Z-scheme Bi₃O₄Cl/AgCl heterojunction ultrathin nanosheets are successfully synthesized by hydrothermal combined with solid-state reduction strategy. The plasmons Ag and Bi are formed during solid-state reduction process, which are firmly anchored on surface of Bi₃O₄Cl and AgCl, respectively, and favors the charge transfer obviously. Experiments results confirm the formation of heterojunction ultrathin nanosheets with the main size of 200∼300 nm and the thickness of <10 nm. The obtained dual plasmons-based direct Z-scheme Bi₃O₄Cl/AgCl heterojunction ultrathin nanosheets with the band gap of ∼1.66 eV exhibit excellent photothermal performance. 98.3% of Cr (VI) can be photocatalytic reduced and TOC removal rate of ceftriatone sodium reached 98.9% within 210 min, respectively. Due to the surface plasma resonance, the catalyst temperature increases obviously, indicating the enhanced photothermal performance, which is favorable for promoting the photocatalytic performance. Moreover, the cyclic stability experiment also proves the high stability and has advantages in practical applications. The excellent property can be ascribed to the direct Z-scheme accelerating charge transfer and prolonging the lifetimes, the dual plasmons enhancing photothermal performance and the spatial separation of photogenerated charge carriers.

Preparation of a novel Z-scheme KTaO3/FeVO4/Bi2O3 nanocomposite for efficient sonocatalytic degradation of ceftriaxone sodium

In this work, a novel Z-scheme sonocatalyst, KTaO₃/FeVO₄/Bi₂O₃, is prepared via ultrasonic-assisted isoelectric point method. The prepared samples are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. The catalytic activity of Z-scheme KTaO₃/FeVO₄/Bi₂O₃ sonocatalyst is studied in degradation of ceftriaxone sodium under ultrasonic irradiation. In addition, the influences of ultrasonic irradiation time, scavengers and sonocatalyst used times on sonocatalytic degradation of ceftriaxone sodium are examined. Under the experimental conditions of 150 min ultrasonic irradiation time, 1.00 g/L KTaO₃/FeVO₄/Bi₂O₃ addition amount and 10.00 mg/L ceftriaxone sodium concentration, the sonocatalytic degradation ratio of ceftriaxone sodium achieves 81.30%. Finally, the possible sonocatalytic degradation mechanism of ceftriaxone sodium caused by Z-scheme KTaO₃/FeVO₄/Bi₂O₃ sonocatalyst is proposed. The enhanced sonocatalytic activity may be attributed to the fact that the FeVO₄ as a special conductive channel provides a strong driving force to transfer electrons through valence state changes of iron and vanadium, which accelerates electron transfer from conduction band (CB) of Bi₂O₃ to valence band (VB) of KTaO₃. Perhaps, the KTaO₃/FeVO₄/Bi₂O₃ composite is an excellent Z-scheme sonocatalyst which can be used to effectively degrade the organic pollutants in wastewater under ultrasonic irradiation.

Iodine ion doped bromo bismuth oxide modified bismuth germanate: A direct Z-scheme photocatalyst with enhanced visible-light photocatalytic performance

A series of Z-scheme I-BiOBr/Bi₁₂GeO₂₀ heterostructures were successfully obtained by a simple method. The Z-scheme I-BiOBr/Bi₁₂GeO₂₀ heterostructures show outstanding photocatalytic performance for degrading the various organic pollutants of the waste water. For degradation of Tetracycline (TC), the Z-scheme 30I-BiOBr/Bi₁₂GeO₂₀ heterostructure exhibits the superior rate constant, which is about 7.73 times, 3.52 times and 1.66 times higher than that of the pure Bi₁₂GeO₂₀, BiOBr and I-BiOBr, respectively. Meanwhile, as we expected, the Z-scheme 30I-BiOBr/Bi₁₂GeO₂₀ heterostructure also displays the enhanced photocatalytic perfomance for degradation of Ciprofloxacin (CIP), 2-Mercaptobenzothiazole (MBT) and reduction of aqueous Cr(VI). The enhancement of photocatalytic performance is attributed to the high redox capacity and the strong interfacial interaction between I-BiOBr and Bi₁₂GeO₂₀, which can effectively improve the separation of photo-induced electron-hole pairs. Additionally, the photocatalytic mechanism over the Z-scheme I-BiOBr/Bi₁₂GeO₂₀ heterostructure is provided. The research work may provide a promising approach to fabricate other Z-scheme heterostructures with efficient photocatalytic performance.