One-step construction of heterostructured metal-organics@Bi2O3 with improved photoinduced charge transfer and enhanced activity in photocatalytic degradation of sulfamethoxazole under solar light irradiation

An innovative triple interface reinforced photocatalytic system based on BiOCl/BaTiO3@Co-BDC-MOF composite for the simultaneous detoxification of Cr(VI) and sulfamethoxazole

The development of effective photocatalysts for the reduction of Cr(VI) and the degradation of antibiotics remains a challenge. The present work reports the development of a novel heterojunction composite material, BiOCl/BaTiO3@Co-BDC-MOF (BOC/BTO@Co-MOF), based on solvothermal techniques. To characterize the surface and bulk features of the material, techniques such as FE-SEM, HR-TEM, BET/BJH, XPS, FT-IR, p-XRD, and UV-Vis-DRS were used. Based on the results, the BiOCl/BaTiO3 nanocomposites are uniformly dispersed on the rod-shaped Co-BDC MOF, resulting in a layered texture on the surface. A further advantage of the composite structure is the strong interfacial enhancement facilitating the separation of photoexcited electron-hole pairs. Also, compared to its pristine counterparts, the heterostructure material exhibited excellent surface area and pore properties. The photocatalytic efficiency towards reduction and degradation of Cr(VI)/SMX pollutants were evaluated by optimizing various analytical parameters, such as pH, catalytic loading concentrations, analyte concentration, and scavenger role. The specially designed BOC/BTO@Co-MOF composite achieved a 96.5% Cr(VI) reduction and 98.2% SMX degradation under 60.0-90.0 min of visible light illumination at pH 3.0. This material is highly reusable and has a six-time recycling potential. The findings of this study contribute to a better understanding of the efficient decontamination of inorganic and organic pollutants in water purification systems.

Bismuth oxide modified V2C MXene as a Schottky catalyst with enhanced photocatalytic oxidation for photo-denitration activities

In this work, a new composite photocatalyst was synthesized by flower-like Bi2O3 and two-dimensional multilayer V2C using a facile hydrothermal method. Compared with the pristine sample, the specific surface area of Bi2O3/V2C MXene composite is significantly increased, which is favourable to improve the photocatalytic efficiency. The analysis of the UV-vis absorption spectrum and band gap energy shows that the construction of heterojunction broadens the light response range, improves the light absorption capacity, and obtains a narrower band gap than any of the single component, which is beneficial to the utilization of light. PL, TPC and EIS analysis revealed that Bi2O3/V2C MXene composite had stronger carrier mobility, which further confirmed that the photocatalytic oxidation performance of the system was the dominant reason in the photocatalytic NO pollutant removal process. This study provides a new idea for better understanding the two-dimensional MXene material-based photocatalyst and improving the NO removal efficiency.

Sunlight-driven intimately coupled photocatalysis and biodegradation (SDICPB): A sustainable approach for enhanced detoxification of triclosan

Triclosan is considered as recalcitrant contaminant difficult to degrade from the contaminated wastewater. Thus, promising, and sustainable treatment method is necessary to remove triclosan from the wastewater. Intimately coupled photocatalysis and biodegradation (ICPB) is an emerging, low-cost, efficient, and eco-friendly method for the removal of recalcitrant pollutants. In this study BiOI photocatalyst coated bacterial biofilm developed at carbon felt for efficient degradation and mineralization of triclosan was studied. Based on the characterization of BiOI prepared using methanol had lower band gap 1.85 eV which favors lower recombination of electron-hole pair and higher charge separation which ascribed to enhanced photocatalytic activity. ICPB exhibits 89% of triclosan degradation under direct sunlight exposure. The results showed that production of reactive oxygen species hydroxyl radical and superoxide radical anion played crucial role in the degradation of triclosan into biodegradable metabolites further the bacterial communities mineralized the biodegradable metabolites into water and carbon dioxide. The confocal laser scanning electron microscope results emphasized that interior of the biocarrier shows a large number of live bacterial cells existing in the photocatalyst-coated carrier, where the little toxic effect on bacterial biofilm occurred on the exterior of the carrier. The extracellular polymeric substances characterization result remarkable confirms that which could act as sacrificial agent of photoholes further helped by preventing the toxicity to the bacterial biofilm from the reactive oxygen species and triclosan. Hence, this promising approach can be a possible alternative method for the wastewater treatment polluted with triclosan.

Applications of Spent Lithium Battery Electrode Materials in Catalytic Decontamination: A Review

For a large amount of spent lithium battery electrode materials (SLBEMs), direct recycling by traditional hydrometallurgy or pyrometallurgy technologies suffers from high cost and low efficiency and even serious secondary pollution. Therefore, aiming to maximize the benefits of both environmental protection and e-waste resource recovery, the applications of SLBEM containing redox-active transition metals (e.g., Ni, Co, Mn, and Fe) for catalytic decontamination before disposal and recycling has attracted extensive attention. More importantly, the positive effects of innate structural advantages (defects, oxygen vacancies, and metal vacancies) in SLBEMs on catalytic decontamination have gradually been unveiled. This review summarizes the pretreatment and utilization methods to achieve excellent catalytic performance of SLBEMs, the key factors (pH, reaction temperature, coexisting anions, and catalyst dosage) affecting the catalytic activity of SLBEM, the potential application and the outstanding characteristics (detection, reinforcement approaches, and effects of innate structural advantages) of SLBEMs in pollution treatment, and possible reaction mechanisms. In addition, this review proposes the possible problems of SLBEMs in practical decontamination and the future outlook, which can help to provide a broader reference for researchers to better promote the implementation of “treating waste to waste” strategy.

Intimately coupled gC3N4 photocatalysis and mixed culture biofilm enhanced detoxification of sulfamethoxazole: Elucidating degradation mechanism and toxicity assessment

In recent years, wide spread of antibiotic-resistant microorganisms and genes emerging globally, an eco-friendly method for efficient degradation of antibiotics from the polluted environment is essential. Intimately coupled photocatalysis and biodegradation (ICPB) using gC₃N₄ for enhanced degradation of sulfamethoxazole (SMX) was investigated. The gC₃N₄ were prepared and coated on the carbon felt. The mixed culture biofilm was developed on the surface as a biocarrier. The photocatalytic degradation showed 74%, and ICPB exhibited 95% SMX degradation efficiency. ICPB showed superior visible light adsorption, photocatalytic activity, and reduced charge recombination. The electron paramagnetic resonance spectrum confirms that the generation of •OH and O₂• radicals actively participated in the degradation of SMX into biodegradable intermediated compounds, and then, the bacterial communities present in the biofilm mineralized the biodegradable compound into carbon dioxide and water. Moreover, the addition of NO₃^-, PO₄^-, and Cl^- significantly enhanced the degradation efficiency by trapping the surface electron. Stability experiments confirmed that gC₃N₄ biohybrid can maintain 85% SMX degradation efficiency after 5 consecutive recycling. Extracellular polymeric substances characterization results show that biohybrid contains 47 mg/L, 14 mg/L, and 13 mg/L protein, carbohydrate, and humic acid, respectively, which can protect the bacterial communities from the antibiotic toxicity and reactive oxygen species. Furthermore, biotoxicity was investigated using degradation products on E.coli and results revealed 83% detoxification efficiency. Overall, this study suggested that gC₃N₄ photocatalyst in an ICPB can be used as a promising eco-friendly method to degrade sulfamethoxazole efficiently.

Nanoengineered metal-organic framework for adsorptive and photocatalytic mitigation of pharmaceuticals and pesticide from wastewater

Rapidly expanding water pollution has transformed into significant dangers around the world. In recent years, the pharmaceutical and agriculture field attained enormous progress to meet the necessities of health and life; however, discharge of trace amounts of pharmaceuticals and pesticides into water significantly have a negative influence on human health and the environment. Contamination with these pollutants also constitutes a great threat to the aquatic ecosystem. To deal with the harmful impacts of such pollutants, their expulsion has attracted researchers' interest a lot, and it became essential to figure out techniques suitable for the removal of these pollutants. Thus, many researchers have devoted their efforts to improving the existing technology or providing an alternative strategy to solve this environmental problem. One of the attractive materials for this purpose is metal-organic frameworks (MOFs) due to their superior high surface area, high porosity, and the tunable features of their structures and function. Among various techniques of wastewater treatment, such as biological treatment, advanced oxidation process and membrane technologies, etc., metal-organic frameworks (MOFs) materials are tailorable porous architectures and are viably used as adsorbents or photocatalysts for wastewater treatment due to their porosity, tunable internal structure, and large surface area. MOFs are synthesized by various methods such as solvo/hydrothermal, sonochemical, microwave and mechanochemical methods. Most common method used for the synthesis of MOFs is solvothermal/hydrothermal methods. Herein, this review aims at providing a comprehensive overview of the latest advances in MOFs and their derivatives, focusing on the following aspects: synthesis and applications. This review comprehensively highlights the application of MOFs and nano-MOFs to remove pharmaceuticals and pesticides from wastewater. For the past years, transition metal-based MOFs have been concentrated as photocatalyst/adsorbents in treating contaminated water. However, work on main group metal-based MOFs is not so abundant. Hence, the foremost objective of this review is to present the latest material and references concerning main group element-based MOFs and nanoscale materials derived from them towards wastewater treatment. It summarizes the possible research challenges and directions for MOFs and their derivatives as catalysts applied to wastewater treatment in the future. With the context of recent pioneering studies on main group elements-based MOFs and their derivatives; we hope to stimulate some possibilities for further development, challenges and future perspectives in this field have been highlighted.

Metal oxide integrated metal organic frameworks (MO@MOF): rational design, fabrication strategy, characterization and emerging photocatalytic applications

This review focuses on the possible synthesis route, characterization techniques, and mechanistic pathways involved in the photocatalytic applications of MO@MOFs.

Superior antibacterial activity of Fe3O4@copper(ii) metal-organic framework core-shell magnetic microspheres

With the rapid evolution of antibiotic resistant bacteria, it has become more and more difficult to treat bacterial infection with traditional antibiotics. Therefore, new strategies with high antibacterial efficiency are urgently needed to combat bacteria effectively. Herein, Fe₃O₄@copper(ii) metal-organic framework Cu₃(BTC)₂ (Cu-BTC) core-shell structured magnetic microspheres were prepared via a layer by layer growth process. The as-prepared Fe₃O₄@Cu-BTC possessed a unique broad-spectrum antibacterial potency against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). The slowly released copper ions and enhanced reactive oxygen species (ROS) generation by facilitating the effective separation and transfer of photoexcited electron-hole pairs played a role in the antibacterial activity of Fe₃O₄@Cu-BTC. Copper ions released from Fe₃O₄@Cu-BTC adhered to the negatively charged bacterial cell, interacted with the bacterial membrane, destroyed the integrity of the membrane which resulted in leakage of bacterial content and then generated ROS to damage DNA, thus leading to cell death. Accordingly, this study provides a competitive strategy for preparing recyclable antibacterial materials that are endowed with targeted antibacterial therapy.

High-Performance Photocatalytic Hydrogen Production and Degradation of Levofloxacin by Wide Spectrum-Responsive Ag/Fe3O4 Bridged SrTiO3/g-C3N4 Plasmonic Nanojunctions: Joint Effect of Ag and Fe3O4

Highly photoresponsive semiconductor photocatalysis for energy and environmental applications require judicious choice and optimization of semiconductor interfaces for wide spectral capabilities. This work aims at rational designing of highly active SrTiO₃/g-C₃N₄ junctions bridged with Ag/Fe₃O₄ nanoparticles for utilizing Z-scheme transfer and surface plasmon resonance effect of Ag augmented by iron oxide. The SrTiO₃/(Ag/Fe₃O₄)/g-C₃N₄ (SFC) catalyst was employed for photocatalytic hydrogen production and photodegradation of levofloxacin (LFC; 20 mg/L) under UV, visible, near infra-red, and natural solar light exhibiting high performance. Under visible light (<780 nm), SFC-3 sample (30 wt % g-C₃N₄ and 3% Ag/Fe₃O₄) shows a H₂ evolution of 2008 μmol g^-1 h^-1 which is ∼14 times that of bare g-C₃N₄. In addition, 99.3% removal of LFC was degraded in 90 min under visible light with retention of activity under sun. The inherent topological properties, complete, higher charge separation, and reduced recombination allowed this catalyst for a high photocatalytic response which was proved by UV-diffuse reflectance spectroscopy, photoluminescence, electrochemical impedance spectroscopy, and photocurrent response measurements. Scavenging experiments and electron spin resonance analysis reveal that the mechanism shifts from a dual charge transfer in case of binary junction to essential Z-scheme with incorporation of Ag/Fe₃O₄. Both ^•O₂^- and ^•OH are main active radicals in visible light, whereas ^•O₂^- majorly participate under UV. The synergistic effect of SrTiO₃, g-C₃N₄, and plasmon resonance of Ag/Fe₃O₄ not only improves light response and reduce recombination but also enhances the redox-ability of charge carriers. A H₂ production mechanism and LFC degradation pathway (degradation, defluorination, and hydrolysis) has been predicted. This work paves a way for development of photocatalysts working in practical conditions for pollution and energy issues.

Utilizing recycled LiFePO4 from batteries in combination with B@C3N4 and CuFe2O4 as sustainable nano-junctions for high performance degradation of atenolol

In this report recycled LiFePO₄ (LFP) from exhaust batteries was utilized to form B@C₃N₄/LiFePO₄/CuFe₂O₄ (BLC) nano-junction as a visible active photocatalyst. The junction synthesized by two routes: Using as extracted LFP and forming LFP by extracted FePO₄ and Li₂CO₃ via in-situ deposition method. The two ternary junctions BLC and BLC (E) (utilizing as extracted LFP) were utilized for visible and solar powered degradation of beta-blocker drug Atenolol (ATL). Varying the loading of CuFe₂O₄ (CF) which possesses lowest band gap, BLC (10%), BLC-3 (30%), BLC-5 (50%) and BLC-E (30% CF and as extracted LFP) were produced with BLC-3 exhibiting remarkable activity. The optical band gaps of BLC-3 (2.40 eV) and BLC (E) (2.46 eV) and photocurrent responses reveal high visible absorption and highly diminished recombination. 99.5% and 85.3% of ATL (20 mg L^-1) could be degraded by BLC-3 and BLC (E) (0.3 g L^-1) respectively in 60 min of exposure to Xe lamp and retaining of high activity in natural sunlight. Band-junction analysis, effect of scavengers and effect on teraphthalic acid and nitroblue tetrazolium reveal O₂^- and OH radicals as active species and mineralization was confirmed by liquid chromatography-mass spectrometer (LC-MS). Cyto-toxicity studies on human peripheral blood cells and effect on growth of Pseudomonas aeruginosa confirm the complete mineralization. The BLC photocatalyst is a promising multi-functional catalyst utilizing LFP (rarely used as photocatalyst) for treatment of pharmaceutical waste water and other environmental applications.