Plasmon-assisted degradation of methylene blue with Ag/AgCl/montmorillonite nanocomposite under visible light

Mineral-Supported Photocatalysts: A Review of Materials, Mechanisms and Environmental Applications

Although they are of significant importance for environmental applications, the industrialization of photocatalytic techniques still faces many difficulties, and the most urgent concern is cost control. Natural minerals possess abundant chemical inertia and cost-efficiency, which is suitable for hybridizing with various effective photocatalysts. The use of natural minerals in photocatalytic systems can not only significantly decrease the pure photocatalyst dosage but can also produce a favorable synergistic effect between photocatalyst and mineral substrate. This review article discusses the current progress regarding the use of various mineral classes in photocatalytic applications. Owing to their unique structures, large surface area, and negatively charged surface, silicate minerals could enhance the adsorption capacity, reduce particle aggregation, and promote photogenerated electron-hole pair separation for hybrid photocatalysts. Moreover, controlling the morphology and structure properties of these materials could have a great influence on their light-harvesting ability and photocatalytic activity. Composed of silica and alumina or magnesia, some silicate minerals possess unique orderly organized porous or layered structures, which are proper templates to modify the photocatalyst framework. The non-silicate minerals (referred to carbonate and carbon-based minerals, sulfate, and sulfide minerals and other special minerals) can function not only as catalyst supports but also as photocatalysts after special modification due to their unique chemical formula and impurities. The dye-sensitized minerals, as another natural mineral application in photocatalysis, are proved to be superior photocatalysts for hydrogen evolution and wastewater treatment. This work aims to provide a complete research overview of the mineral-supported photocatalysts and summarizes the common synergistic effects between different mineral substrates and photocatalysts as well as to inspire more possibilities for natural mineral application in photocatalysis.

Rapid photodegradation of methylene blue by laser-induced plasma

A new strategy was established for the degradation of wastewater-based organic pollutants. Laser-induced plasma (LIP) was used as an alternative UV light source to realise rapid photodegradation of methylene blue (MB), an organic pollutant. A conventional 1064 nm Nd:YAG laser was used for plasma excitation to degrade MB solutions. The results show that the LIP effectively degraded the organic matter, and the degradation efficiency was related to the UV component with wavelength less than 400 nm. The compositions of the plasma excited by different dielectric substrates are different owing to various mechanisms involving moderate heat dissipation and sonoluminescence. However, metallic substrates, especially Fe, can enhance the proportion of UV light and accelerate the degradation efficiency. In the process of methylene blue degradation, solution parameters, such as initial dye concentration, pH, irradiation time and hydrogen peroxide concentration, will affect the degradation efficiency. The conditions of effective degradation of methylene blue (10 mg L⁻¹ MB⁻¹ concentration, 50 mL L⁻¹ H₂O₂ concentration, pH = 3 and P = 60 mW) were obtained in this study, which can provide reference for practical application.

A new strategy was established for the degradation of wastewater-based organic pollutants.

Green synthesis of Ag@AgCl/Elaeagnus angustifolia seed nanocomposite using Elaeagnus angustifolia leaves: an amazing nanophotocatalyst with highly photocatalytic activity under sunlight irradiation

In this investigation, Ag@AgCl nanoparticles were synthesized by a green and inexpensive method using Elaeagnus angustifolia leaves, as a reducing and stabilizing agent without using any toxic solvent, external halide source, harsh chemicals, or capping agents. In this protocol, the nanophotocatalyst was synthesized via immobilization of Ag@AgCl NPs on the surface of biowaste Elaeagnus angustifolia seed (EAS) as a green support, which prevents the agglomeration Ag@AgCl NPs and improves the catalytic activity. The biosynthesized nanophotocatalyst were characterized by UV-Vis spectroscopy, Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE SEM), energy dispersive X-ray spectroscopy (EDS), and transform electron microscopy (TEM) and inductively couple plasma mass spectrometry (ICP). In order to investigate the photocatalytic activity of the biosynthesized nanophotocatalyst, it was used in the degradation of methylene blue (MB) under sunlight. The results showed that nanophotocatalyst had an excellent photo activity without any agglomeration. In addition, the nanophotocatalyst can be easily be recycled and reused several times without losing its activity. Graphical abstract.

Photocatalytic degradation of methyl orange, methylene blue and rhodamine B with AgCl nanocatalyst synthesised from its bulk material in the ionic liquid [P6 6 6 14]Cl

The photocatalytic degradation of wastewater containing three industrial dyes belonging to different families, methyl orange (MO), methylene blue (MB) and Rhodamine B (RhB), was studied under UV-Vis irradiation using synthesised silver chloride nanoparticles. The nanocatalyst was prepared by a dissolution/reprecipitation method starting from the bulk powder and the ionic liquid trihexyl(tetradecyl)phosphonium chloride, [P_{6 6 6 14}]Cl, without addition of other solvents. The obtained catalyst was characterised by UV-Vis absorbance, X-ray powder diffraction, transmission electron microscopy and scanning electron microscopy. The decolourisation of the samples was studied by UV-Vis absorbance at the corresponding wavelength. Starting from 10 ppm dye solutions and 1 g L^-1 of the synthesised AgCl nanoparticles, degradation efficiencies of 98.4% for MO, 98.6% for MB and 99.9% for RhB, were achieved in 1 h. The degradation mechanisms for the different dyes were studied. Comparison with other frequently used nanocatalysts, namely P-25 Degussa, TiO₂ anatase, Ag and ZnO, highlights the strong catalytic activity of AgCl nanoparticles. Under the same experimental conditions, these nanoparticles led to higher (more than 10%) and faster degradations.

Study of antibacterial activity of Ag and Ag2CO3 nanoparticles stabilized over montmorillonite

Silver carbonate and silver nanoparticles (NPs) over of stabilizer montmorillonite (MMT) have been synthesized in aqueous and polyol solvent, respectively. Dispersions of silver nanoparticles have been prepared by the reduction of silver nitrate over of MMT in presence and absence of Na2CO3 compound in ethylene glycol. It was observed that montmorillonite was capable of stabilizing formed Ag nanoparticles through the reduction of Ag(+) ions in ethylene glycol. Na2CO3 was used as carbonate source in synthesis of Ag2CO3 NPs in water solvent and also for controlling of Ag nanoparticles size in ethylene glycol medium. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and ultraviolet-visible diffuse reflectance spectroscopy (DRS). The TEM images showed that Ag NPs size in presence Na2CO3 salts was smaller than without that. The results indicated intercalation of Ag and Ag2CO3 nanoparticles into the montmorillonite clay layers. The diffuse reflectance spectra exhibited a strong surface plasmon resonance (SPR) adsorption peak in the visible region, resulting from Ag nanoparticles. The antibacterial testing results showed that the Ag2CO3-MMT nanocomposite exhibited an antibacterial activity higher than Ag-MMT sample against Escherichia coli.

Fast photocatalytic degradation of methylene blue dye using a low-power diode laser

This study focused on the application of diode lasers as alternative light sources for the fast photocatalytic degradation of methylene blue. The photocatalytic decomposition of methylene blue in aqueous solution under 443 nm laser light irradiation was found to be technically feasible using Ag/AgCl nanoparticles as photocatalysts. The effects of various experimental parameters, such as irradiation time, light source, catalyst loading, initial dye concentration, pH, and laser energy on decolorization and degradation were investigated. The mineralization of methylene blue was confirmed by chemical oxygen demand analysis. The results demonstrate that the laser-induced photocatalytic process can effectively degrade methylene blue under the optimum conditions (pH 9.63, 4 mg/L MB concentration, and 1.4 g/L Ag/AgCl nanoparticles).