Enhanced photocatalytic capacity of ZnS–ZnO–Sm2O3 composites for the removal of dyes and antibiotics in visible light region

Study of Photodegradation of Bentazon Herbicide by Using ZnO-Sm2O3 Nanocomposite Under UV Light

The removal of organic pollutants from water is significantly important as they have harmful effects on the ecosystem. Heterogeneous photocatalysis is a potential technique for the removal of organic pollutants from the wastewater. In this article, zinc oxide (ZnO) and samarium oxide (Sm2O3) nanoparticles and ZnO-Sm2O3 nanocomposite (ZS) were synthesized by the co-precipitation method. We report the bandgap engineering of zinc oxide (ZnO) by making a composite with samarium oxide (Sm2O3) to enhance the photocatalytic activity. The smaller optical energy bandgap of the ZS nanocomposite as compared to the individual oxide nanoparticles shows that it has a light absorption range from UV to natural light. The photodegradation of bentazon herbicide as a model pollutant has been investigated by using the prepared samples. The photocatalytic activity of the prepared sample against bentazon herbicide was carried out under UV light for 140 min. The degradation efficiency against bentazon of the prepared samples was ZS > ZnO > Sm2O3, respectively. The ZnO-Sm2O3 nanocomposite showed a higher photocatalytic performance against bentazon and achieved a 90% degradation efficiency under a UV light source in 140 min. The pseudo-first-order degradation kinetic was studied under different operational conditions, such as catalyst loading, initial pH and bentazon concentration, showing that the degradation rate of bentazon was strongly influenced by these operational parameters. The obtained optimization conditions for practical application were a catalyst loading of 20 mg, pH of solution equal to 7 and bentazon concentration of 5 ppm for ZS nanocomposite in 60 mL of contaminated water. Furthermore, based on the scavenger study, hydroxyl and superoxide radicals play major role in the degradation experiment. The obtained results show that ZS nanocomposite can be a good potential candidate for wastewater treatment.

Photocatalysis oxidative desulfurization of dibenzothiophene in extremely deep liquid fuels on the Z-scheme catalyst ZnO-CuInS2-ZnS intelligently integrated with carbon quantum dots: performance, mechanism, and stability

In this study, we improved the electrochemical and photocatalytic properties of the ZnO-CuInS2-ZnS (ZCZ) material by integrating with carbon quantum dots (CQD) with particle sizes from 2 to 5 nm. The integration of ZnO-CuInS2-ZnS with carbon quantum dots (ZnO-CuInS2-ZnS/CQD:ZCZ-CQD) enhanced the visible light absorption, significantly reduced the electron-hole recombination rate, and facilitated the electron transfer and separation processes as confirmed by UV-visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL), and electrochemical impedance spectroscopy (EIS). The successful integration of ZCZ with carbon quantum dots was confirmed using X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) methods. The ZCZ/CQD photocatalyst removed up to 98.32% of DBT after 120 minutes of reaction, maintained over 90% durability after 10 cycles, and retained its structure without any changes. The ZCZ photocatalyst integrated with CQD enhances faster dibenzothiophene (DBT) removal by 4.46, 3.24, 2.53, and 1.72 times compared to ZnO, CuInS2, ZnS, and ZnO-CuInS2-ZnS, respectively. Factors influencing the oxidation process of DBT including the mass of the photocatalyst, initial DBT concentration, stability, and reaction kinetics were studied. Through active species trapping experiments, this study demonstrated that the formation of ˙O2 - and ˙OH radicals determines the reaction rate. The mechanism of photocatalysis on ZCZ-CQD materials and the intermediate products formed in the process of photocatalytic oxidative desulfurization of dibenzothiophene is proposed based on electrochemical measurements and GC-MS results.

Phytosynthesis via wasted onion peel extract of samarium oxide/silver core/shell nanoparticles for excellent inhibition of microbes

The aqueous onion peel extract (OPE) was used to synthesize silver nanoparticles (Ag-onion), samarium oxide nanoparticles (Sm2O3-onion), and silver/samarium oxide core/shell nanoparticles (Ag@Sm2O3-onion). The produced nanoparticles were characterized by thermal gravimetric analysis (TGA), infrared spectra (FT-IR), absorption spectra (UV-Vis), energy band gap, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), zeta potential, and transmission electron microscopy (TEM). OPE and NPs were tested for the disinfection of some water microbes. XRD analysis exhibited an amorphous structure of samarium oxide in both Sm2O3-onion and Ag@ Sm2O3-onion. The isolated bacteria from the water sample were Bacillus subtilis (OQ073500) and Escherichia coli (MW534699), while the isolated fungi were Alternaria brassicae (MZ266540), Aspergillus flavus (MT550030), Aspergillus penicillioides (MW957971), Pythium ultimum (MW830915), Verticillium dahlia (MW830379), Fusarium acuminatum (MZ266538), Candida albicans (MW534712), and Candida parapsilosis (MW960416). High levels of antimicrobial activity were seen in both the nanoparticles and the aqueous onion peel extract. Based on experimental results, Ag@Sm2O3 demonstrated the highest activity as an effective disinfectant, indicating the effectiveness of the modification process.

Fe3O4@BNPs@ZnO-ZnS as a novel, reusable and efficient photocatalyst for dye removal from synthetic and textile wastewaters

In this study, new magnetic nanocomposites with different molar ratios of zinc oxide-zinc sulfide were synthesized together with photocatalysts MNPs@BNPs@ZnO and MNPs@ BNPs@ ZnS. The photocatalytic behavior of these hybrid nanocomposites under visible light and ultraviolet light was investigated to remove methylene blue (MB), methyl orange (MO) dyes, real textile and carton effluents. After studies, the best active photocatalyst in both visible light and ultraviolet light is MNPs@BNPs@ZnO-ZnS (ZnO/ZnS: 0.75:0.25), which displayed the best performance in the ultraviolet region. According to the TEM, the average particle size for MNPs@BNPs@ZnO-ZnS (ZnO/ZnS: 0.75:0.25) is between 10 and 30 nm. Zeta potential (DLS) showed that the charge on the photocatalyst surface is negative at most pHs. PL analysis confirmed that the amount of hole-electron recombination in the optimal photocatalyst is less than MNPs@BNPs@ZnO and MNPs@BNPs@ZnS. Also, based on kinetic studies, the rate constant for removing azo dyes such as MO and MB was 0.0186 and 0.0171 min^-1, respectively. It is worth noting that in addition to the novelty of the synthesized photocatalysts, the UV and visible lamps used in this research are inexpensive, durable, and highly efficient.

Flower-like Bi2S3-In2S3 heterojunction for efficient solar light induced photoreduction of Cr(VI)

To develop Bi₂S₃-based heterojunction for efficient solar light induced photoreduction of Cr(VI), flower-like Bi₂S₃-In₂S₃ composites consisted of nanorods were prepared via a microwave-assisted hydrothermal route. In contrast with pure Bi₂S₃, Bi₂S₃-In₂S₃ composites exhibited the enhanced photoreduction activity while the decreased adsorption capacity for Cr(VI) removal. The best removal efficiency of 70 mg L^-1 Cr(VI) solution (99.86%) was achieved by the optimal 3-Bi₂S₃-In₂S₃ with a Bi/In molar ratio of 4:1 within 140 min. It's ascribed to the narrow band gap for strengthened visible-light response, the tight interface between Bi₂S₃ and In₂S₃ for rapid transfer and separation of charge carriers, and the enough S vacancies for highly-efficient active sites of adsorption-photoreduction. However, the long-term photo-corrosion resulted in the slightly inferior reusability of 3-Bi₂S₃-In₂S₃ under solar light irradiation after five cycles.