Synthesis of flower-like Bi2O4/ZnO heterojunction and mechanism of enhanced photodegradation for organic contaminants under visible light

Boosted visible-light-induced photo-Fenton degradation of organic pollutants over a novel direct Z-scheme NH2-MIL-125(Ti)@FeOCl heterojunction catalyst

Improving the charge separation, charge transfer, and effective utilization is crucial in a photocatalysis system. Herein, we prepared a novel direct Z-scheme NH2-MIL-125(Ti)@FeOCl (Ti-MOF@FeOCl) composite photocatalyst through a simple method. The prepared composite catalyst was utilized in the photo-Fenton degradation of Rhodamine B (RhB) and ciprofloxacin (CIP). The Ti-MOF@FeOCl (10FeTi-MOF) catalyst exhibited the highest catalytic performance and degraded 99.1 and 66% of RhB and CIP, respectively. However, the pure NH2-MIL-125(Ti) (Ti-MOF) and FeOCl catalysts achieved only 50 and 92% of RhB and 50 and 37% of CIP, respectively. The higher catalytic activities of the Ti-MOF@FeOCl composite catalyst could be due to the electronic structure improvements, photoinduced charge separations, and charge transfer abilities in the catalyst system. The composite catalysts have also enhanced adsorption and visible light-responsive properties, allowing for efficient degradation. Furthermore, the electron paramagnetic resonance (EPR) signals, the reactive species trapping experiments, and Mott-Schottky (M - S) measurements revealed that the photogenerated superoxide radical (•O2-), hydroxyl radical (•OH), and holes (h+) played a vital role in the degradation process. The results also demonstrated that the Ti-MOF@FeOCl heterojunction composite catalysts could be a promising photo-Fenton catalyst system for the environmental remediation. Environmental implications The discharging of toxic contaminants such as organic dyes, antibiotics, and other emerging pollutants to the environment deteriorates the ecosystem. Specifically, the residues of organic pollutants recognized as a threat to ecosystem and a cause for carcinogenic effects. Among them, ciprofloxacin is one of antibiotics which has biological resistance, and metabolize partially in the human or animal bodies. It is also difficult to degrade ciprofloxacin completely with traditional treatment methods. Similarly, organic dyes are also toxic and a cause for carcinogenic effects. Therefore, effective degradation of organic pollutants such as RhB and ciprofloxacin with appropriate method is crucial.

Radiation synthesis and photocatalytic performance of floated graphene oxide decorated ZnO/ alginate-based beads for methylene blue degradation under visible light irradiation

Organic dye contamination, emanating from pharmaceutical, paper, and textile industries into water resources, severely threatens marine and human life even at low concentrations. Photocatalysis is one of the most important remediation techniques that decolorize water by employing the power of light. In this work, the development of floated beads of Sodium Alginate/hydroxyethyl methacrylate (Alg-g-HEMA) encompass graphene oxide (GO) decorated Zinc oxide (ZnO) utilizing ionizing radiation was designed to function as a photocatalyst when exposed to visible light. Floatability was induced using calcium carbonate. GO was sonochemically decorated with ZnO nanoparticles and the yield was characterized using XRD, FTIR, TEM, SEM, and EDX techniques. Optical characteristics of the developed nanostructure were performed using UV-Vis spectrophotometry. The photocatalytic activity of the floated (Alg-g-HEMA)-ZnO@GO beads was assessed for the photo decolorization of methylene blue dye (MB) under visible light. The upshot of operational factors such as photocatalyst dose, pH, initial dye concentration, and irradiation time on the decolorization of MB was examined. It was observed that 1 g of the developed (Alg-g-HEMA)-ZnO@GO photocatalyst was able to decolorize 1000 ml of 20 ppm of MB within 150 min at pH 9. In terms of kinetics, photo-decolorization follows Langmuir Hinshelwood pseudo-first order.

Review on Methylene Blue: Its Properties, Uses, Toxicity and Photodegradation

The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.

Construction of a flower-like S-scheme Bi2WO6/BiOCl nano-heterojunction with enhanced visible-light photocatalytic properties

A series of flower-like Bi2WO6/BiOCl photocatalyst were synthesized by a facile hydrothermal method. S-scheme Bi2WO6/BiOCl-3 nano-heterojunction exhibits the excellent photocatalytic activity for degradation of RhB under visible light irradiation.

One-pot microwave-hydrothermally synthesized carbon nanotube-cerium oxide nanocomposites for enhanced visible photodegradation of acid orange 7

Carbon nanotubes (CNT)-cerium oxide (CeO2) nanocomposites were fabricated successfully by one-pot microwave hydrothermal growth of regular CeO2 nanoparticles with a size of 8 nm on hydroxyl-functionalized multi-walled CNTs. These nanocomposite photocatalysts demonstrated an acid orange (AO7) photocatalytic degradation efficiency of above 90% under solar-simulated light irradiation for 3 h, which was much higher than that of the pure CeO2 nanoparticles. The enhanced photocatalytic activity was observed to mainly originate from the ˙O2- and hole traps, while the hydroxyl radical ˙OH played a secondary role.

Removal of Mercury (II) by EDTA-Functionalized Magnetic CoFe2O4@SiO2 Nanomaterial with Core-Shell Structure

In order to reduce the difficulty and risk of operation, decrease the preparation time and improve the adsorption performance of magnetic nano-silicon adsorbent with core-shell structure, a carboxylated CoFe₂O₄@SiO₂ was prepared by EDTA-functionalized method using a safe, mild and simple hydrothermal method. The results show that the prepared material of CoFe₂O₄@SiO₂-EDTA has a maximum adsorption capacity of 103.3 mg/g for mercury ions (Hg(II)) at pH = 7. The adsorption process of Hg(II) is a chemical reaction involving chelation and single-layer adsorption, and follows the pseudo-second-order kinetic and Langmuir adsorption isotherm models. Moreover, the removal of Hg(II) is a spontaneous and exothermic reaction. The material characterization, before and after adsorption, shows that CoFe₂O₄@SiO₂-EDTA has excellent recyclability, hydrothermal stability and fully biodegradable properties. To summarize, it is a potential adsorption material for removing heavy metals from aqueous solutions in practical applications.

The effective photocatalysis and antibacterial properties of AgBr/Ag2MoO4@ZnO composites under visible light irradiation

A novel Z-scheme AgBr/Ag₂MoO₄@ZnO photocatalyst was fabricated via a hydrothermal process and in situ growth method. X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy were used to determine the structure of the photocatalyst. The results showed that the composites were tightly connected by the (101) lattice plane of ZnO, the (222) plane of Ag₂MoO₄ and the (200) lattice plane of AgBr. Because of the strong redox activity and good separability of photoelectrons and holes induced by the Z-scheme structure, the photodegradation rate for ciprofloxacin (CIP) solution was 80.5% by the photocatalysis of 0.5 AgBr/Ag₂MoO₄@ZnO. In addition, more than 99.999% of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa cells were killed within 60 min. These results demonstrate that AgBr/Ag₂MoO₄@ZnO is a promising photocatalyst, which can be used in organic pollutant degradation and the photocatalytic antibacterial area.