Efficient photocatalytic degradation of emerging ciprofloxacin under visible light irradiation using BiOBr/carbon quantum dot/saponite composite

Ag-loaded BiFeO3/CuS heterostructured based composite: an efficient photocatalyst for removal of antibiotics and antibacterial activities

The performance of advanced materials in environmental applications using green energy is the tremendous interest among researchers. The visible light responsive BiFeO3 (BFO), BiFeO3/CuS (BFOC), and Ag-loaded BiFeO3/CuS (Ag-BFOC) heterostructures have been synthesized by reflux method followed by hydrothermal and wetness impregnation method. These synthesized composites are well characterized through X-ray diffraction, UV diffuse reflectance spectroscopy, scanning electron microscope, and Fourier transfer infrared spectroscopy techniques. Compared with BFO and BFOC, Ag-BFOC exhibits the highest photocatalytic performance towards the degradation of antibiotics ciprofloxacin (76%) within 120-min time and also showed better antibacterial performance towards gram-negative (Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii) bacteria. Moreover, the novelty of the present work is the addition of CuS on the surface of BiFeO3 from heterojunction type II and facilitates the electron-hole channelization at the interfaces between BiFeO3 and CuS. Again, the loading of Ag on BiFeO3/CuS helps in shifting the absorption band towards the red end, is eligible to absorb more sunlight due to surface plasmon resonance effect, improves the separation efficiency of photo-generated charge carriers, and enhances the photocatalytic degradation of ciprofloxacin. The antibacterial property of Ag gives a best result towards antimicrobial activity. The prepared composites have proved their durability and stability by four successive cycles and prove the versatility of the composite.

Enhanced generation of oxysulfur radicals by the BiOBr/Montmorillonite activated sulfite system: Performance and mechanism

The easily synthesized, cost-effective, and stable photocatalysts for sulfite activation are always required for the enhancement of organic contaminants degradation. Herein, the facile coprecipitation synthesis of Bismuth oxybromide (BiOBr)/Montmorillonite (MMT) was reported, which could activate sulfite (SO32-/HSO3-) under sunlight and accelerate the catalytic performance more effectively than pristine BiOBr. After adding sulfite to the photocatalysis system, the photodegradation efficiency of atrazine (ATZ) achieved 73.7% ± 1.5% after 5 min and 94.4% ± 1.6% after 30 min of sunlight irradiation with BiOBr/MMT. The BiOBr/MMT-sulfite system also presented remarkable photocatalytic performance to eliminate various contaminants, including ciprofloxacin, sulfadiazine, tetracycline, and carbamazepine. The various features of the photocatalyst materials were studied, including their surface morphology, structure, optical properties, and composition. The results illustrated that by adding MMT, the bandgap of the pristine BiOBr was reduced and the surface area was increased, which led to an increased ability to adsorb materials. Results of various influence factors showed this enhanced system had satisfactory and stable removal performance of ATZ in the pH range of 3.0-6.5, but HPO42- had a strong negative effect on the system performance. Oxysulfur radicals (SO5·- and SO4·-), h+, and 1O2 were discovered as the prevailing active species in the BiOBr/MMT-sulfite system. The proposed degradation mechanism of this photocatalyst-enhanced system revealed that sulfite adsorption on the surface of the photocatalyst played a vital role during the initial phase, and the degradation pathway of ATZ was discussed. This study provides a new synthesis strategy of a photocatalyst for sulfite activation and expands the potential uses of Bi-based photocatalysts in degrading difficult-to-remove organic pollutants.

Construction of floatable flower-like plasmonic Bi/BiOCl-loaded hollow kapok fiber photocatalyst for efficient degradation of RhB and antibiotics

The development of low-cost and high-efficiency photocatalysts for the degradation of organic pollutants has been an essential and feasible approach to environmental remediation. However, conventional powder photocatalysts suffer from agglomeration, limited light utilization, and reuse difficulties, which hinder their large-scale practical application. Herein, a floatable flower-like plasmonic Bi/BiOCl-loaded hollow kapok fiber (KF/Bi/BC) photocatalyst was synthesized by a facile solvothermal method. It exhibited excellent photocatalytic degradation of Rhodamine B (RhB), ofloxacin (OFX), and tetracycline (TC) under UV-vis irradiation. The incorporation of metallic Bi not only greatly enhanced the light absorption of BiOCl in the visible region but also served as an effective "electron trap", facilitating the efficient separation and transfer of photogenerated electrons and holes. Furthermore, the remarkable floatability of the catalyst contributed to increased light utilization and facilitated the recycling of the catalyst. This work provided a convenient, effective, and feasible method for the fabrication of floatable photocatalysts with excellent catalytic properties, and has great potential for practical applications.

Bi/BiOI/carbon quantum dots nano-sheets with superior photocatalysis

A new photocatalyst of Bi/BiOI/Carbon quantum dots (CQDs) was synthesized via a simple method. Photocatalytic performance of Bi/BiOI/CQDs was evaluated by photodegradation of RhB. Experiment indicated that the introduction of CQDs could improve the photocatalysis activity of BiOI obviously. Moreover, there is a optimum percentage of CQDs. In this photocatalytic system, the enhanced photoactivity was mainly attributed to the heterojunction interface between CQDs and BiOI, as well as the enhanced light harvesting for the appropriate CQDs introduction. The radicals trapping experiments revealed that O2˙-, ˙OH and h+ were the main active species during the photocatalysis process.

Fabrication of 2D/1D Bi2WO6/halloysite nanotubes photocatalyst towards water purification: a support effect onin situconstruction and electron-hole separation

In this research work, a reusable and efficient 2D/1D heterogeneous structured photocatalyst based on amine-functionalized halloysite nanotubes (MHNTs) and Bi2WO6nanosheet (BWO) was prepared using a facile hydrothermal method for decomposing PPCPs under simulated sunlight. On the degradation of tetracycline hydrochloride (TCH), the effects of composite catalysts prepared under various conditions were discussed. The results showed that over BWO/MHNTs with a mass ratio was 3:1, the synthesizing temperature was 120 °C and the precursor pH value was 1, the TCH (10 mg l-1) degradation efficiency reached 100% after 1 h irradiation of simulated sunlight. Moreover, BWO/MHNTs composites kept good recovery and stable photocatalytic activity after 5 cycles. The excellent dispersion of Bi2WO6on the surface of clay minerals and the oxygen vacancy enhanced electron-hole separation may be responsible for the its high activity and stability. Futhermore, the radical capture test demonstrated that ·O-2was primarily responsible for the photodegradation of TCH. Thus, BWO/MHNTs composites exhibit a good application prospect in the field of sunlight-driven photocatalytic degradation towards PPCPs pollutants in water.

Design and Synthesis of NTU-9/C3N4 Photocatalysts: Effects of NTU-9 Content and Composite Preparation Method

Hybrid materials based on graphitic carbon nitride (g-C₃N₄) and NTU-9 metal-organic frameworks (MOF) were designed and prepared via solvothermal synthesis and calcination in air. The as-prepared photocatalysts were subsequently characterized using Brunauer-Emmett-Teller (BET) analysis, UV-Vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) emission spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The obtained NTU-9/C₃N₄ composites showed a greatly improved photocatalytic performance for the degradation of toluene in the gas phase under LED visible-light irradiation (λ_max = 415 nm). The physicochemical properties and photocatalytic activities of the obtained NTU-9/C₃N₄ materials were tuned by varying the NTU-9 content (5-15 wt%) and preparation method of the composite materials. For composites prepared by calcination, the photocatalytic activity increased with decreasing NTU-9 content as a result of the formation of TiO₂ from the MOFs. The best photocatalytic performance (65% of toluene was photodegraded after 60 min) was achieved by the NTU-9/C₃N₄ sample prepared via the solvothermal method and containing 15 wt% MOF, which can be attributed to the appropriate amount and stable combination of composite components, efficient charge separation, and enhanced visible-light absorption ability. The photocatalytic mechanisms of the prepared hybrid materials depending on the preparation method are also discussed.

Mechanistic insight into the degradation of ciprofloxacin in water by hydroxyl radicals

Ciprofloxacin (CIP), an effective antibacterial drug, is widely used to treat bacterial infections in humans and animals. However, drug pollution from residues and the development of resistant genes may pose serious ecological risks. Among the known methods of CIP degradation, advanced oxidation technology initiated by hydroxyl radicals exhibits great potential. However, an in-depth study of the degradation mechanism is difficult because of the limitations of the testing methods. In this study, CIP oxidation by hydroxyl radicals was evaluated using density functional theory (DFT), and the thermodynamics, kinetics, and toxicity were investigated. The results show that CIP oxidation occurs mainly through the piperazine ring, benzene ring, and CC. High reactivity is achieved in the initial reactions, where only five reactions are not thermodynamically spontaneous. Reactions involving direct hydrogen abstraction by oxygen in this system are superior to the indirect reactions. Some theoretically predicted products, such as P6 and P11, are consistent with those reported in previous experiments, indicating that the theoretical study can provide supplementary information about the oxidation paths. The branching ratios for the hydrogen atom abstraction and addition reactions were 37. 45% and 62.55%, respectively. Finally, this reaction system is completely nontoxic based on toxicity assessment.

Efficient Activation of Peroxymonosulfate by V-Doped Graphitic Carbon Nitride for Organic Contamination Remediation

Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) activation have been developed as an ideal pathway for completely eradication of recalcitrant organic pollutants from water environment. Herein, the V-doped graphitic carbon nitride (g-C₃N₄) is rationally fabricated by one-step thermal polymerization method to activate PMS for contamination decontamination. The results demonstrate the V atoms are successfully integrated into the framework of g-C₃N₄, which can effectively improve light absorption intensity and enhance charge separation. The V-doped g-C₃N₄ displays superior catalytic performance for PMS activation. Moreover, the doping content has a great influence on the activation performances. The radical quenching experiments confirm •O₂^-, SO₄^•-, and h⁺ are the significant species in the catalytic reaction. This work would provide a feasible strategy to exploit efficient g-C₃N₄-based material for PMS activation.