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1.
Int J Mol Sci ; 23(3)2022 Feb 02.
Article in English | MEDLINE | ID: covidwho-1686814

ABSTRACT

A chabazite-type zeolite was prepared by the hydrothermal method. Before ion exchange, the chabazite was activated with ammonium chloride (NH4Cl). The ion exchange process was carried out at a controlled temperature and constant stirring to obtain ion-exchanged chabazites of Ti4+ chabazite (TiCHA), Zn2+ chabazite (ZnCHA), Cu2+ chabazite (CuCHA), Ag+ chabazite (AgCHA) and Au3+ chabazite (AuCHA). Modified chabazite samples were characterized by X-ray diffraction (XRD), scanning electron microscope equipped with energy-dispersive spectroscopy (SEM-EDS), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), N2 adsorption methods and UV-visible diffuse reflectance spectroscopy (DRS). XRD results revealed that the chabazite structure did not undergo any modification during the exchange treatments. The photocatalytic activity of chabazite samples was evaluated by the degradation of methylene blue (MB) in the presence of H2O2 under ultraviolet (UV) light illumination. The photodegradation results showed a higher degradation efficiency of modified chabazites, compared to the synthesized chabazite. CuCHA showed an efficiency of 98.92% in MB degradation, with a constant of k = 0.0266 min-1 following a first-order kinetic mechanism. Then, it was demonstrated that the modified chabazites could be used for the photodegradation of dyes.


Subject(s)
Methylene Blue/chemistry , Water Pollutants, Chemical/chemistry , Zeolites/chemistry , Photolysis , Zeolites/chemical synthesis
2.
J Hazard Mater ; 404(Pt B): 124082, 2021 02 15.
Article in English | MEDLINE | ID: covidwho-813688

ABSTRACT

Heterogeneous Fenton catalysts are emerging as excellent materials for applications related to water purification. In this review, recent trends in the synthesis and application of heterogeneous Fenton catalysts for the abatement of organic pollutants and disinfection of microorganisms are discussed. It is noted that as the complexity of cell wall increases, the resistance level towards various disinfectants increases and it requires either harsh conditions or longer exposure time for the complete disinfection. In case of viruses, enveloped viruses (e.g. SARS-CoV-2) are found to be more susceptible to disinfectants than the non-enveloped viruses. The introduction of plasmonic materials with the Fenton catalysts broadens the visible light absorption efficiency of the hybrid material, and incorporation of semiconductor material improves the rate of regeneration of Fe(II) from Fe(III). A special emphasis is given to the use of Fenton catalysts for antibacterial applications. Composite materials of magnetite and ferrites remain a champion in this area because of their easy separation and reuse, owing to their magnetic properties. Iron minerals supported on clay materials, perovskites, carbon materials, zeolites and metal-organic frameworks (MOFs) dramatically increase the catalytic degradation rate of contaminants by providing high surface area, good mechanical stability, and improved electron transfer. Moreover, insights to the zero-valent iron and its capacity to remove a wide range of organic pollutants, heavy metals and bacterial contamination are also discussed. Real world applications and the role of natural organic matter are summarised. Parameter optimisation (e.g. light source, dosage of catalyst, concentration of H2O2 etc.), sustainable models for the reusability or recyclability of the catalyst and the theoretical understanding and mechanistic aspects of the photo-Fenton process are also explained. Additionally, this review summarises the opportunities and future directions of research in the heterogeneous Fenton catalysis.


Subject(s)
Hydrogen Peroxide/chemistry , Iron/chemistry , Light , Waste Water , Water Pollutants, Chemical/analysis , Water Purification/methods , Catalysis , Disinfection , Humic Substances/analysis , Metal-Organic Frameworks/chemistry , Minerals/chemistry , Oxidation-Reduction , Photochemistry , Reactive Oxygen Species/chemistry , Waste Water/chemistry , Waste Water/microbiology , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/radiation effects
3.
Ecotoxicol Environ Saf ; 206: 111116, 2020 Dec 15.
Article in English | MEDLINE | ID: covidwho-741186

ABSTRACT

Disinfectant quaternary ammonium compounds (Quats) have diverse uses in a variety of consumer and commercial products, particularly cleaning products. With the emergence of the COVID-19 pandemic, they have become a primary tool to inactivate the SARS-CoV-2 virus on surfaces. Disinfectant Quats have very low vapor pressure, and following the use phase of the products in which they are found, disposal is typically "down-the-drain" to wastewater treatment systems. Consequently, the potential for the greatest environmental effect is to the aquatic environment, from treated effluent, and potentially to soils, which might be amended with wastewater biosolids. Among the earliest used and still common disinfectant Quats are the alkyl dimethyl benzyl ammonium chloride (ADBAC) compounds and the dialkyl dimethyl ammonium chloride (DDAC) compounds. They are cationic surfactants often found in consumer and commercial surface cleaners. Because of their biocidal properties, disinfectant Quats are heavily regulated for human and environmental safety around the world. Consequently, there is a robust database of information regarding the ecological hazards and environmental fate of ADBAC and DDAC; however, some of the data presented are from unpublished studies that have been submitted to and reviewed by regulatory agencies (i.e., EPA and European Chemicals Agency) to support antimicrobial product registration. We summarize the available environmental fate data and the acute and chronic aquatic ecotoxicity data for freshwater species, including algae, invertebrates, fish, and plants using peer-reviewed literature and unpublished data submitted to and summarized by regulatory agencies. The lower limit of the range of the ecotoxicity data for disinfectant Quats tends to be lower than that for other surface active agents, such as nonionic or anionic surfactants. However, ecotoxicity is mitigated by environmental fate characteristics, the data for which we also summarize, including high biodegradability and a strong tendency to sorb to wastewater biosolids, sediment, and soil. As a result, disinfectant Quats are largely removed during wastewater treatment, and those residues discharged in treated effluent are likely to rapidly bind to suspended solids or sediments, thus mitigating their toxicity.


Subject(s)
Disinfectants/toxicity , Quaternary Ammonium Compounds/toxicity , Water Pollutants, Chemical/toxicity , Animals , Aquatic Organisms/drug effects , Biodegradation, Environmental , COVID-19/epidemiology , COVID-19/prevention & control , Disinfectants/chemistry , Disinfectants/pharmacology , Ecotoxicology , Humans , Pandemics/prevention & control , Quaternary Ammonium Compounds/chemistry , Quaternary Ammonium Compounds/pharmacology , Risk Assessment , SARS-CoV-2/drug effects , Waste Water/chemistry , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/pharmacology , Water Purification/methods
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