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The waste management of polyethylene terephthalate (PET)-derived polyester (PES) textile is a global issue, and material recovery through chemical recycling can restore a circular economy. In our investigation, microwave-induced catalytic aminolysis and glycolysis of PES textile wastes using Ag-doped ZnO nanoparticles have been proposed. Ag-doped ZnO is prepared by the sol-gel method and characterised by XRD, FT-IR, UV-Vis, SEM-EDX and TEM. The reaction parameters such as PET-to-catalyst ratio, microwave power and irradiation time, temperature and catalyst recycling have been optimised. The catalyst was found to be more stable and could be recycled up to six times without losing its activity. Both the aminolysis and glycolysis of PES showed 100% conversion and afforded of bis (2-hydroxy ethylene) terephthalamide (BHETA) and bis (2-hydroxy ethylene) terephthalate (BHET), respectively. The depolymerisation of PES wastes using Ag-doped ZnO afforded BHETA and BHET for about 95 and 90%, respectively. The monomers BHET and BHETA confirmed by FT-IR, 1 H NMR and mass spectroscopy. According to the findings, 2 mol% Ag-doped ZnO has higher catalytic activity., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Nano-size TiO2 photocatalysts were prepared by sol-gel and ultrasonic-assisted sol-gel methods using two different sources of ultrasonicator, i.e., a bath type and tip type. The physicochemical characteristics of the catalysts were investigated by BET, XRD and TEM analyses and the photocatalytic properties of the TiO2 catalysts prepared by three different methods were compared. The intrinsic and extrinsic properties of TiO2, such as the particle size, surface area, pore-volume, pore-diameter, crystallinity as well as anatase, rutile and brookite phase ratios, could be controlled by the ultrasonic-assisted sol-gel method. During this preparation method, the effect of such important operating variables as the ultrasonic irradiation time, power density, the ultrasonic sources (bath-type and tip-type), magnetic stirring during synthesis, initial temperatures and size of the reactors are discussed here. It was found that each of the parameters played a significant role in controlling the properties of the TiO2 nano-particles. Among the three different methods, TiO2 photocatalysts prepared by ultrasonic (tip-US) assisted sol-gel possessed the smallest particle size, highest surface area and highest pore-volume than the catalysts prepared by the other two methods. 4-Chlorophenol was used as a pollutant to observe the photocatalytic degradation ability of the prepared photocatalysts and the TiO2 catalysts prepared by the bath-US ultrasonic-assisted sol-gel method were shown to be the most highly active. This is due to their high surface area and high pore-diameter. This study clearly demonstrates the importance and advantages of ultrasonication in the modification and improvement of the photocatalytic properties of mesoporous nano-size TiO2 particles.

Super paramagnetic ZnFeO nanoparticles were prepared by a surfactant assisted (ethylamine) hydrothermal method along with heat treatment. The nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, high resolution scanning electron microscopy, Transmission electron microscopy, vibrating sample magnetometer and diffuse reflectance spectra technique. From the analyses, influence of calcination temperature on the structural, vibrational, morphological, magnetic and optical properties of ZnFeO nanoparticles were investigated. The ZnFeO nanoparticles with an average particle size of 17 nm showed high photocatalytic activity in the degradation of methylene blue (90 %). This work demonstrates that ZnFeO4 can be used as a potential monocomponent in visible-light photocatalysis for the degradation of organic pollutants. Furthermore, the products were super paramagnetic and could be conveniently separated within 15 min and recycled by using simple magnet, which is very beneficial for the degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

Abstract: Nano-size TiO2 photocatalysts were prepared by sol-gel and ultrasonic-assisted sol-gel methods using two different sources of ultrasonicator, i.e., a bath type and tip type. The physicochemical characteristics of the catalysts were investigated by BET, XRD and TEM analyses and the photocatalytic properties of the TiO2 catalysts prepared by three different methods were compared. The intrinsic and extrinsic properties of TiO2, such as the particle size, surface area, pore-volume, pore-diameter, crystallinity as well as anatase, rutile and brookite phase ratios, could be controlled by the ultrasonic-assisted sol-gel method. During this preparation method, the effect of such important operating variables as the ultrasonic irradiation time, power density, the ultrasonic sources (bath-type and tip-type), magnetic stirring during synthesis, initial temperatures and size of the reactors are discussed here. It was found that each of the parameters played a significant role in controlling the properties of the TiO2 nano-particles. Among the three different methods, TiO2 photocatalysts prepared by ultrasonic (tip-US) assisted sol-gel possessed the smallest particle size, highest surface area and highest pore-volume than the catalysts prepared by the other two methods. 4-Chlorophenol was used as a pollutant to observe the photocatalytic degradation ability of the prepared photocatalysts and the TiO2 catalysts prepared by the bath-US ultrasonic-assisted sol-gel method were shown to be the most highly active. This is due to their high surface area and high pore-diameter. This study clearly demonstrates the importance and advantages of ultrasonication in the modification and improvement of the photocatalytic properties of mesoporous nano-size TiO2 particles. [Copyright &y& Elsevier]

A flame aerosol method has been employed to prepare spherical TiO2 nano-particle photocatalysts with controlled anatase/rutile phase ratios without calcination at higher temperatures. This method was found to have important advantages since the main factors in achieving high photocatalytic activity such as the particle size, crystallinity and the anatase/rutile phase ratios could be easily controlled. In particular, the incorporation of small amounts of bimetals, such as Fe and Zn, were found to initiate the formation of well-crystalline, small and uniform spherical nano-size particles with a well-defined anatase/rutile phase ratio of around 60/40, similar to P-25 TiO2. This suppressed the recombination of the photoformed charge carriers leading to a significant increase in the photocatalytic reactivity of the TiO2 nano-particles. The incorporation of very small amounts of mono-metals, such as Fe, Cr and Zn (around 1 at.%), within the TiO2 nano-particles led to a slight increase in the photocatalytic activity of the TiO2 nano-particle photocatalysts for the complete oxidation of 2-propanol dissolved in water into CO2 and H2O as compared with the unincorporated pure TiO2. The incorporation of bimetals of Fe and Zn within TiO2 (Fe/Zn–TiO2) nano-particles, on the other hand, led to a remarkable enhancement in the photocatalytic activity as compared with the unincorporated and mono-metal incorporated TiO2. [ABSTRACT FROM AUTHOR]

Copper doped TiO 2 nanoparticles with reduced graphene oxide as a solid support were introduced as new ambient light antimicrobial agents. The doping with copper extended the activity to the visible light and the reduced graphene oxide helped to enhance charge transport during photocatalytic degradation of microorganisms. The antimicrobial activity of the bare as well as the modified TiO 2 particles was tested with four different microorganisms, namely two Gram positive and two Gram negative types. Zone of inhibition and minimum inhibitory concentration (MIC) tests were carried out under visible light conditions. The results suggest that Cu 2 O-TiO 2 /rGO exhibits better visible light antibacterial property with higher zone of inhibition area and lower value of minimum inhibitory concentration for both Gram positive and Gram negative microorganisms compared to the bare TiO 2 . Polymer nanocomposite films were prepared using these nanoparticles with PVA and the antimicrobial activity was tested again for possible packaging applications. [ABSTRACT FROM AUTHOR]