Electrospun BiOCl/Bi2 Ti2 O7 Nanorod Heterostructures with Enhanced Solar Light Efficiency in the Photocatalytic Degradation of Tetracycline Hydrochloride

Highly efficient recovery of Zn (II) from zinc-containing wastewater by tourmaline tailings geopolymers to in-situ construct nanoscale ZnS for the photodegradation of tetracycline hydrochloride

While treating zinc-containing wastewater, recovering zinc for reuse as a secondary resource has significant environmental and economic benefits. Herein, based on the alkali-activated tourmaline tailings geopolymers (TTG) after adsorption of zinc ions (Zn (II)), a series of new composites with in-situ construction ZnS nanoparticles on TTG (ZnS/TTG) were synthesized, and used as photocatalysts for the photodegradation of tetracycline hydrochloride (TCH) in solution. Specifically, ZnS nanoparticles were uniformly and stably distributed in the layered structure of TTG, interweaving with each other to generate an interfacial electric field, which could induce more photocarrier generation. Meanwhile, TTG acted as an electron acceptor to accelerate the electron transfer at the interface, thus enhancing the photodegradation activity for TCH. The active radical quenching experiments combined with the ESR indicated that the active species produced during the photocatalytic degradation of TCH by ZnS/TTG composites were •O2- and photogenerated h+. When the initial concentration of Zn (II) was 60 mg/L, the synthesized 60-ZnS/TTG composites (0.5 g/L) reached 91.53% degradation efficiency of TCH (10 mg/L) at pH = 6. Furthermore, the possible pathways and mechanism of 60-ZnS/TTG composites photodegraded TCH were revealed with the aid of degraded intermediates. This report not only proposed valuable references for reusing heavy metal ions and removing TCH from wastewater, but also provided promising ideas for realizing the conversion of used adsorbents into high-efficiency photocatalysts.

S-scheme heterojunction of hollow corncob-like ZnIn2S4/LaFeO3 for water splitting and tetracycline degradation

Reasonable design of heterojunction photocatalysts with high-quality interfacial coupling is an effective way to improve the photocatalytic activity of semiconductors. Herein, we successfully decorated Zinc indium sulfide (ZnIn2S4, ZIS) on perovskite Lanthanum ferrite (LaFeO3, LFO) with more active sites by a pre-hydrothermal combined post-calcination method, and constructed S-scheme heterojunction photocatalyst with a unique hollow corncob-like morphology for efficient photocatalytic hydrogen production and tetracycline (TC) degradation. When the mass ratio of LFO is 35% and 15%, the ZIS/LFO photocatalyst exhibits the best hydrogen evolution rate and TC photodegradation performance, respectively. Notably, the optimum hydrogen production rate is 6 times that of pure ZIS with excellent cycling stability. The enhanced photoactivity can be explained by the hollow corncob-like morphology and the formed S-scheme heterojunction with close interface contact between ZIS and LFO, which significantly improves the spatial separation and migration efficiency of photoexcited carriers, while maintaining a high redox potential. Finally, it provides an effective support for the photocatalytic mechanism through calculation results of density functional theory. This work not only provides a novel construction strategy of photocatalysts for efficient photocatalytic hydrogen evolution and organic pollutant degradation, but also opens up a new insight for perovskite-modified S-scheme heterojunction.

Direct Z-scheme mediated SmVO4/UiO-66-NH2 heterojunction nanocomposite for the degradation of antibiotic tetracycline hydrochloride molecules under sunlight

The use of tetracycline hydrochloride (TCH) for veterinary, human therapy, and agriculture has risen in the past few decades, making it to become one of the most exploited antibiotics. However, TCH residue in the environment is causing issues related to the evolution of antibiotic-resistant bacteria. To address such a problem, photodegradation offers a potential solution to decompose these pollutants in wastewater and thereby mitigates negative environmental impacts. In this context, the research focuses on the use of the rare-earth metal oxide samarium orthovanadate (SmVO₄) with nanorod structure, coupled with UiO-66-NH₂ for the photocatalytic degradation. Their photocatalytic activity to degrade antibiotic TCH molecules is explored under simulated solar light irradiation. The integration of UiO-66-NH₂ with SmVO₄ enhanced the light absorption, recombination resistance, carrier lifetime (from 0.382 to 0.411 ns) and specific surface area (from 67.17 to 246 m²/g) of the composite system as confirmed from multiple analyses. The obtained results further indicated that SmVO₄/UiO-66-NH₂ nanocomposites could form a direct Z-scheme based heterojunction. Such mechanism of charge transfer leads to the effective degradation of TCH molecules up to 50% in 90 min under solar light, while it is degraded only 30% in the case of bare-SmVO₄ nanorods. In this work, the incorporation of UiO-66-NH₂ positively influences photoelectrochemical properties and improves the overall photoredox properties of SmVO₄ for the degradation of complex compounds like antibiotic TCH molecules. Therefore, UiO-66-NH₂ can be proposed as an effective material to sensitize the rare-earth based photocatalytic material.

Construction of Hexagonal Prism-like Defective BiOCL Hierarchitecture for Photocatalytic Degradation of Tetracycline Hydrochloride

Oxygen vacancy manipulation and hierarchical morphology construction in oxygen-containing semiconductors have been demonstrated to be effective strategies for developing high efficiency photocatalysts. In most studies of bismuth-based photocatalysts, hierarchical morphology and crystal defects are achieved separately, so the catalysts are not able to benefit from both features. Herein, using boiling ethylene glycol as the treatment solution, we developed an etching-recrystallization method for the fabrication of 3D hierarchical defective BiOCl at ambient pressure. The target hierarchical 3D-BiOCl is composed of self-assembled BiOCl nanosheets, which exhibit a hexagonal prism-like morphology on a micron scale, while simultaneously containing numerous oxygen vacancies within the crystal structure. Consequently, the target catalyst was endowed with a higher specific surface area, greater light harvesting capability, as well as more efficient separation and transfer of photo-excited charges than pristine BiOCl. As a result, 3D-BiOCl presented an impressive photocatalytic activity for the degradation of tetracycline hydrochloride in both visible light and natural white light emitting diode (LED) irradiation. Moreover, an extraordinary recycling property was demonstrated for the target photocatalyst thanks to its hierarchical structure. This study outlines a simple and energy-efficient approach for producing high-performance hierarchically defective BiOCl, which may also open up new possibilities for the morphological and crystal structural defect regulation of other Bi-based photocatalysts.

Persulfate assisted photocatalytic degradation of tetracycline by bismuth titanate under visible light irradiation

Tetracycline is a commonly used broad-spectrum antibiotic to prevent and cure the bacterial infections. However, the incompletely metabolic tetracycline molecules by organisms discharged into aquatic environment increase the ecological toxicity....

Investigation of the Kinetics and Reaction Mechanism for Photodegradation Tetracycline Antibiotics over Sulfur-Doped Bi2WO6-x/ZnIn2S4 Direct Z-Scheme Heterojunction

The rational design of direct Z-scheme heterostructural photocatalysts using solar energy is promising for energy conversion and environmental remediation, which depends on the precise regulation of redox active sites, rapid spatial separation and transport of photoexcited charge and a broad visible light response. The Bi₂WO₆ materials have been paid more and more attention because of their unique photochemical properties. In this study, S²⁻ doped Bi₂WO_6-x coupled with twin crystal ZnIn₂S₄ nanosheets (Sov−BWO/T−ZIS) were prepared as an efficient photocatalyst by a simple hydrothermal method for the removal of tetracycline hydrochloride (TCH). Multiple methods (XRD, TEM, XPS, EPR, UV vis DRS, PL etc.) were employed to systematically investigate the morphology, structure, composition and photochemical properties of the as-prepared samples. The XRD spectrum indicated that the S²⁻ ions were successfully doped into the Sov−BWO component. XPS spectra and photoelectrochemical analysis proved that S²⁻ served as electronic bridge and promoted captured electrons of surface oxygen vacancies transfer to the valence band of T−ZIS. Through both experimental and in situ electron paramagnetic resonance (in situ EPR) characterizations, a defined direct Z-scheme heterojunction in S-BWO/T−ZIS was confirmed. The improved photocatalytic capability of S-BWO/T−ZIS results ascribed that broadened wavelength range of light absorption, rapid separation and interfacial transport of photoexcited charge, precisely regulated redox centers by optimizing the interfacial transport mode. Particularly, the Sov−50BWO/T−ZIS Z-scheme heterojunction exhibited the highest photodegradation rate was 95% under visible light irradiation. Moreover, this heterojunction exhibited a robust adsorption and degradation capacity, providing a promising photocatalyst for an organic pollutant synergistic removal strategy.

Study on the mechanism of degradation of tetracycline hydrochloride by microwave-activated sodium persulfate

Among the different antibiotics, tetracycline hydrochloride (TCH) is one of the most commonly used. In this study, the activated sodium persulfate (SPS) process induced by microwave (MW) energy was used to treat TCH. The effect of different operational parameters of MW/SPS-treated TCH, such as SPS concentration, TCH concentration, initial pH, and MW power, was investigated. The concentration changes of TCH were determined using a spectrophotometer. The results of radical scavenger experiments indicated that the sulfate radical (SO₄ ^·-) was stronger than the hydroxyl radical (·OH). On the basis of high performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, a possible degradation pathway of TCH was proposed. This research indicates that the MW/SPS system is a promising prospect for the treatment of TCH.

Anionic polyacrylamide-assisted construction of thin 2D-2D WO3/g-C3N4 Step-scheme heterojunction for enhanced tetracycline degradation under visible light irradiation

Thin 2D/2D WO₃/g-C₃N₄ Step-scheme (S-scheme) heterojunction with carbon doping and bridge (C-W/N) was constructed with anionic polyacrylamide (APAM), in which APAM functioned as an assistant templet and a carbon source. APAM and WO₃ were inserted into g-C₃N₄ nanosheet. The carbon, thin planar structure and WO₃ with oxygen vacancies result in fast charge transfer, high quantum efficiency and strong driving force for photocatalytic reaction. Consequently, as-prepared C-W/N ternary composite photocatalyst exhibited significantly enhanced photocatalytic performance for tetracycline (TC) degradation under visible light compared to pure g-C₃N₄, WO₃ and other binary composites. Moreover, the material showed high stability and reusability in cyclic TC degradation. The principal intermediate products over C-W/N photocatalyst were revealed by HPLC-MS analysis. Corresponding degradation pathway of TC was also presented in this work. According to the trapping experiments, analysis of electron spin resource (ESR) and band gap, possible charge transfer pathways of C-W/N are proposed and discussed in detail. Based on the results, carbon derived from APAM works not only as electron mediator but also as acceptor for photocatalytic degradation reaction. It is a promising way to further modulate heterojunction for varies applications.

Insights into degradation pathways and toxicity changes during electro-catalytic degradation of tetracycline hydrochloride

The removal of antibiotics has attracted much attention due to their extremely high adverse impacts on the environment. However, the potential risks of degradation intermediates are seldom reported. In this work, the influence of different factors on the electro-catalytic degradation efficiency of tetracycline hydrochloride (TCH) by the prepared carbon nanotubes/agarose/indium tin oxide (CNTs/AG/ITO) electrode was investigated. Under optimal conditions (10 wt% CNTs dosage, pH = 7), the maximum degradation efficiency for TCH (10 mg L^-1) reached up to 96% within 30 min treatment with 4 V potential. Superoxide anions (•O₂^-) played an important role in the electro-catalytic degradation. Totally 10 degradation intermediates were identified using HPLC-MS/MS, and the degradation pathway was proposed. Toxicities of the parent antibiotic and the identified intermediates were calculated using the ECOSAR (Ecological Structure Activity Relationship) program in EPISuite, and results showed that more toxic intermediates were generated. The maximal chronic toxicity for green algae of the intermediate increased 1439.92 times. Furthermore, antimicrobial activity was further verified by disk agar biocidal tests with Escherichia coli ATCC25922 and higher biotoxicity intermediates compared with parent compounds were confirmed to be formed. Therefore, more attention should be paid on the potential risk of degradation intermediates in the treatment of wastewater containing antibiotics.

One-step synthesis of ZnS@MoS2 core–shell nanostructure for high efficiency photocatalytic degradation of tetracycline

Four kinds of ZnS@MoS₂ nanocomposite photocatalysts were successfully prepared via a facile hydrothermal method.

Facile Fabrication of C-TiO2 Nanocomposites with Enhanced Photocatalytic Activity for Degradation of Tetracycline

Visible-lightdriven C-TiO₂ nanocomposites were prepared via a simple calcination and acid etching process. The C-TiO₂ nanocomposites were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and high-resolution TEM. The results showed that TiO₂ nanoparticles were combined with a porous carbon layer through surface C-O groups, which facilitates the strong interface interaction. The interface combination of nano-TiO₂ and carbon material increases the specific surface area of nano-TiO₂, widens the range of light response, and improves the efficiency of light-induced electron migration. The visible-light photocatalytic activity of the prepared photocatalyst was evaluated by the decomposition of tetracycline aqueous solution. Compared with that of pure TiO₂, the photocatalytic activity of C-TiO₂ nanocomposites was significantly improved. Furthermore, a possible photocatalytic mechanism was also tentatively proposed. This work can promote the development of active photocatalysts under solar light for the photodegradation of environmental pollutants.

In situ construction of the BiOCl/Bi2Ti2O7 heterojunction with enhanced visible-light photocatalytic activity

Herein, a BiOCl/Bi₂Ti₂O₇ heterojunction was prepared as an efficient visible light-driven photocatalyst through an in situ hydrothermal method, and its photocatalytic properties were investigated via a comparable method.

Microscale flower-like magnesium oxide for highly efficient photocatalytic degradation of organic dyes in aqueous solution

Flower-like MgO microparticles with excellent photocatalytic performance in degradation of various organic dyes were synthesized by a facile precipitation method via the reaction between Mg²⁺ and CO₃²⁻ at 70 °C.

Polyethylene glycol-doped BiZn2VO6 as a high-efficiency solar-light-activated photocatalyst with substantial durability toward photodegradation of organic contaminations

In this study, we focus on a simple, low-priced, and mild condition hydrothermal route to construct BiZn₂VO₆ nanocompounds (NCs) as a novel photocatalyst with strong solar light absorption ability for environmental purification using solar energy. NCs were further doped with polyethylene glycol (PEG) to improve their photocatalytic efficiency for photodegradation processes through inhibition of fast charge carrier recombination rates and higher charge separation efficiency. Surface morphology, phase structure, optical characteristics, and band structure of the as-prepared samples were analyzed using XRD, EDX, XPS, SEM, UV-vis spectroscopy, CL, and BET techniques. PEG-doped BiZn₂VO₆ NCs were applied as effective materials to degrade various kinds of organic pollutants including cationic and anionic types, and these NCs exhibited excellent photocatalytic efficiency as compared to traditional photocatalysts. In particular, the PEG-doped BiZn₂VO₆ (0.10% w/v) photocatalyst exhibited highly enhanced photocatalytic performance with improvements of about 46.4, 28.3, and 7.23 folds compared with PEG-doped ZnO nanorods (NRs), pristine BiVO₄, and BiZn₂VO₆ samples, respectively, for the decomposition of congo red (CR) dye. After 40 minutes of sunlight irradiation, 97.4% of CR was decomposed. In this study, scavenging experiments indicated that both hydroxyl radicals and holes play dominant roles in CR photodegradation under simulated solar light irradiation. Meanwhile, the optimal photocatalyst demonstrated good reproducibility and stability for successive cycles of photocatalysis.