Influence of selenium precursors on the formation of iron selenide nanostructures (FeSe2): Efficient Electro-Fenton catalysts for detoxification of harmful organic dyestuffs

FeSe2 and Its Composites for Pollutants Removal: Synthesis, Mechanisms, and Application Potential

In recent years, the research of FeSe2 and its composites in environmental remediation has been gradually carried out. And the FeSe2 materials show great catalytic performance in photocatalysis, electrocatalysis, and Fenton-like reactions for pollutants removal. Therefore, the studies and applications of FeSe2 materials are reviewed in this work, including the common synthesis methods, the role of Fe and Se species as well as the catalyst structure, and the potential for practical environmental applications. Hereinto, it is worth noting in particular that the lower-valent Se (Se2-), unsaturated Se (Se-), and Se vacancies (VSe) can play different roles in promoting pollutants removal. In addition, the FeSe2 material also demonstrates high stability, reusability, and adaptability over a wider pH range as well as universality to different pollutants. In view of the overall great properties and performance of FeSe2 materials compared with other typical Fe-based materials, it deserves and needs further research. And finally, this paper presents some challenges and perspectives in future development, looking forward to providing helpful guidance for the subsequent research of FeSe2 and its composites for environmental application.

Sulfate radical dominated rapid pollutants degradation leaded by selenium vacancies in core-shell N-doped carbon wrapped cobalt diselenide nanospheres

Herein, a new heterogeneous CoSe2-x@NC material with abundant selenium vacancies is synthesized via an in-situ carbonization-selenization process from cobaltic metal organic framework (Co-MOF). The obtained CoSe2-x@NC has a unique electronic structure and rich active sites, which can activate peroxymonosulfate (PMS) to degrade carbamazepine (CBZ) with superior catalytic performance and stability. The quenchingexperiments and EPR test show that SO4•- is the dominant reactive oxidation species (ROSs) for CBZ degradation. Significantly, systemic electrochemical tests and theoretical calculations illustrated that the dominant role of SO4•- is attributed to the existence of abundant selenium vacancies in CoSe2-x@NC, which can adjust the density of electron cloud of the Co atoms in CoSe2-x@NC to improve the PMS adsorption and promoting the conversion of transition metallic redox pairs (Co3+/Co2+). This work provides a facile way to improve the activity and stability of CoSe2 by defect engineering in the PMS based advanced oxidation process (AOPs).

Sensitive determination of polychlorinated biphenyls from beverages based on switchable solvent microextraction: A robust methodology

Polychlorinated biphenyls (PCBs) are a kind of hazardous persistent organic contaminants and widely present in nature due to large consumption in the past. Although PCBs have been banned in many countries of the world, they are still present at trace level in food and water samples. It is of significant value to establish reliable enrichment and detection method. Based on the conversion of the hydrophilicity and hydrophobicity from heptanoic acid under alkali and acid, increasing the contact area between heptanoic acid and PCBs, a new switchable solvent micro-extraction method for PCBs from beverages was developed with good extraction efficiency using heptanoic acid as the extractant prior to gas chromatography-tandem mass spectrometry (GC-MS/MS). The key parameters that had impact on enrichment of PCBs were investigated in detail. Under the optimal conditions, a good linearity can be achieved in a concentration range of 0.01-20 μg L^-1 with the correlation coefficients of 0.9978-0.9994. Limits of detection for PCB28, PCB53, PCB206 were 3 ng L^-1 and PCB118 was 5 ng L^-1 while other target PCBs were 2 ng L^-1. Intra-day and inter-day precisions were in the range of 1.9-4.2% and 2.1-4.2％(relative standard deviation, RSD, n = 6), respectively. The real sample spiked recoveries of the targets were in the range of 93.2-114.3％ (n = 3). The enrichment factors were in the range of 16.2-17.9. The results proved that this method was reliable for monitoring trace PCBs in beverage samples and will help for future assessments of impacts on human and animal health.

Structure, morphology and modelling studies of polyvinylalcohol nanocomposites reinforced with nickel oxide nanoparticles and graphene quantum dots

Nickel oxide (NiO) nanoparticles (NPs) and graphene quantum dots (GQDs) reinforced polyvinyl alcohol (PVA) nanocomposite films were prepared using a solution casting technique. The physicochemical characteristics of PVA/NiO/GQDs (PNG) nanocomposite films were studied using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM). The obtained PNG nanocomposite films showed good mechanical flexibility and improved tensile strength. The influence of nanofiller concentrations on PNG nanocomposite film. The obtained results demonstrate an increase in the activation energy (Ea) up to PNG3 upon increasing the GQDs concentration and thereafter, its decreases. The fundamental interactions of the constituents of PNG nanocomposite film were investigated using density functional theory (DFT). This study on electronic structure reveals that the PVA model indirectly interacts with GQDs through the NiO model. This configuration is favoured in terms of interaction energy (-78 kJ/mol) compared to the one in which PVA interacts directly with the GQDs model.

Bifunctional iron molybdate as highly effective heterogeneous electro-Fenton catalyst and Li-ion battery anode

Three-dimensional materials have attracted considerable interest in energy and environmental remediation fields. Iron molybdate (FMO) materials have prepared via a facile hydrothermal technique with glycerol assistance, and their structural and chemical composition confirmed using various physico-chemical techniques. The prepared bi-functional material is a strong candidate for energy storage and electrocatalytic degradation of Methylene blue and Congo red. Experimental results confirmed the synthesized FMO-10 catalyst was extremely efficient for methylene blue and Congo red breakdown, achieving 91 % and 96 % degradation in 36 h, respectively. This high catalytic activity was attributed to FMO significant visible light absorption, and reactive OH formation from H₂O₂ synergistically triggered by both Fe³⁺ and MoO₄^2-. Prepared FMO samples demonstrated excellent potential as negative electrode material for lithium ion batteries. Electrode specific capacity initially dropped then rebounded to 1265 mAh g^-1 after 100 cycles at 100 mA g^-1 change rate between 0.01 and 3.0 V.

Ternary Zn1-xNixSe nanostructures as efficient photocatalysts for detoxification of hazardous Congo red, methyl orange, and chrome yellow dyes in wastewater sources

Water contamination by hazardous organic pollutants poses an extreme threat to the environment and globally endangers aquatic life and human health. Hence, the removal of toxic organic effluents from water sources is necessary to ensure a healthy green environment. To this end, a new class of emerging, visible-light-driven Zn- and Ni-based ternary metal-selenide (Zn_1-xNi_xSe) nanophotocatalysts, with tunable nanostructures via regulation of the stoichiometric ratios of Zn and Ni, were synthesized for efficient water purification by a facile one-pot hydrothermal process. These catalysts exhibit outstanding porous properties, with large surface areas and average particle sizes of around 80 ± 10 nm. The as-prepared ternary Zn_1-xNi_xSe catalysts enable improved optical properties, intrinsic conductivity, bandgap reductions, and large numbers of active sites compared with pristine materials, thereby exhibiting outstanding degradation properties against various dye molecules, including Congo red, methyl orange, and chrome-IV upon visible light irradiation. The improved photodegradation capabilities of the Zn_1-xNi_xSe catalysts may be attributed to the synergistic combinations of Zn and Ni selenides, which in turn minimize the recombination rates of the photogenerated carriers compared to their individual constituents. These findings clearly demonstrate that the proposed ternary Zn_1-xNi_xSe catalysts could be potentially used to remove toxic organic contaminants from industrial wastewater.