Photocatalytic degradation of an anionic dye in aqueous solution by visible light responsive zinc oxide-termite hill composite

Adsorption-photocatalysis synergy of reusable mesoporous TiO2-ZnO for photocatalytic degradation of doxycycline antibiotic

The potentials of mesoporous TiO2-ZnO (3TiZn) were explored on photocatalytic degradation of doxycycline (DOX) antibiotic, likewise the influence of adsorption on the photocatalytic process. The 3TiZn was characterized for physical and chemical properties. Stability, reusability, kinetic and the ability of 3TiZn to degrade high concentration of pollutant under different operating conditions were investigated. Photocatalytic degradation of DOX was conducted at varied operating conditions, and the best was obtained at 1 g/L catalyst dosage, solution inherent pH (4.4) and 50 ppm of DOX. Complete degradation of 50 ppm and 100 ppm of DOX were attained within 30 and 100 min of the reaction time, respectively. The stability and reusability study of the photocatalyst proved that at the tenth (10th) cycle, the 3TiZn is as effective in the degradation of DOX as in the first cycle. This may be attributed to the fusion of the mixed oxides during calcination. The 3TiZn is mesoporous with a pore diameter of 17 nm, and this boosts it potential to degrade high concentration of DOX. It was observed that the adsorption capacity of 3TiZn enhance the photocatalytic process. It can be emphasized that 3TiZn portrayed a remarkable catalyst stability and good potentials for industrial application.

ZnO QDs/GO/g-C3N4 Preparation and Photocatalytic Properties of Composites

Using an ultrasound-assisted chemical technique, ZnO quantum dot and ZnO composites were created. The optical characteristics and structural details of these composites were examined using TEM, XRD, XPS, FT-IR, UV-vis, and BET. The results revealed that both the ZnO quantum dot composite and ZnO composite exhibited outstanding optical properties, making them suitable for photocatalytic reactions. In order to analyze the photocatalytic performance, a degradation experiment was conducted using Rhodamine B solution as the simulation dye wastewater. The experiment demonstrated that the degradation of Rhodamine B followed the first-order reaction kinetics equation when combined with the photocatalytic reaction kinetics. Moreover, through cyclic stability testing, it was determined that the ZnO QDs-GO-g-C3N4 composite sample showed good stability and could be reused. The degradation rates of Rhodamine B solution using ZnO-GO-g-C3N4 and ZnO QDs-GO-g-C3N4 reached 95.25% and 97.16%, respectively. Furthermore, free-radical-trapping experiments confirmed that ·O2- was the main active species in the catalytic system and its photocatalytic mechanism was elucidated. The photocatalytic oxidation of ZnO quantum dots in this study has important reference value and provides a new idea for the subsequent research.

Studies on Synthesis, Characterization, and Photocatalytic Activity of TiO2 and Cr-Doped TiO2 for the Degradation of p-Chlorophenol

TiO₂ and Cr-TiO₂ nanoparticles (NPs) have been synthesized by the sol-gel method using titanium isopropoxide as the precursor of Titania. The prepared samples were analyzed by employing scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared analyses. Under UV irradiation, the photocatalytic activities of TiO₂ and Cr-TiO₂ were observed by estimating the % degradation of p-chlorophenol (PCP) as a sample pollutant. The extent of degradation was investigated, varying the catalyst dosage, initial PCP concentration, irradiation time, and solution pH. The experimental results show that efficiency of catalysts initially increases but decreases later on, whereas the % degradation of PCP is the highest at its lowest initial concentration. For TiO₂ and Cr-TiO₂ NPs at their optimal catalyst dosage of 2.0 g/L, acidic pH, and with UV irradiation for 90 min, the observed % degradation of PCP is 50.23 ± 3.12 and 66.51 ± 2.14%, respectively. Thus, the prepared Cr-TiO₂ NPs have enhanced the degradation efficiency of PCP with an irradiation time which is four time less than those reported earlier. From the kinetics analysis, the degradation reaction of PCP is found to follow a pseudo-first-order model and the rate constants are 0.0075 and 0.0122 min^-1 for pure TiO₂ and Cr-TiO₂ NPs, respectively. The present study has further revealed that owing to the lower rate of electron-hole pair recombination, the photocatalytic activity of Cr-TiO₂ NPs becomes higher than that of TiO₂. Therefore, as viable photocatalytic agents, Cr-TiO₂ NPs are suggested to be used also for efficient degradation of other organic pollutants.

Kinetic and thermodynamic study on the esterification of oleic acid over SO3H-functionalized eucalyptus tree bark biochar catalyst

Herein, esterification of oleic acid (OA) over tosylic acid functionalized eucalyptus bark biochar (TsOH-MBC) to synthesize fatty acid methyl ester (FAME) was investigated. The TsOH-MBC catalyst was prepared via pyrolysis-activation-sulfonation process at various impregnation ratios and was characterized by SEM, FTIR, EDX, XRD, BET, TGA and acid site density techniques. The catalytic performance of the sulfonated biochar catalyst was described in terms of acidity and FAME yield. 6 g of sulfonic acid loaded on 10 g of MBC (6TsOH-MBC) appeared to be most appropriate combination to achieve a highly active catalyst for the esterification of OA with 96.28% conversion to FAME at 80 °C for 5 h with catalyst loading of 4.0 wt% and 8:1 methanol/OA molar ratio. The catalytic reaction kinetic data were very well described by the second-order model, with a rate coefficient of 0.223 mL mol⁻¹ h⁻¹ at 80 °C and activation energy of 81.77 kJ mol⁻¹. The thermodynamic parameters such as \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Delta H$$\end{document}ΔH, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Delta S$$\end{document}ΔS and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Delta G$$\end{document}ΔG were determined to be 78.94 kJ mol⁻¹, 135.3 J mol⁻¹ K⁻¹ and 33.03 kJ mol⁻¹, respectively. This research provided an environmentally friendly procedure for FAME production that could be replicated on a commercial scale.

Pumice-supported ZnO-photocatalyzed degradation of organic pollutant in textile effluent: optimization by response surface methodology, artificial neural network, and adaptive neural-fuzzy inference system

A heterogeneous photocatalysis was adopted to treat textile industry effluent using a combination of pumice-supported ZnO (PUM-ZnO) photocatalyst and solar irradiation. The visible light-responsive PUM-ZnO photocatalyst was prepared via the impregnation method and characterized using various spectroscopic techniques. The photocatalytic degradation process was modeled via response surface methodology (RSM), artificial neural network (ANN), and adaptive neuro-fuzzy inference system (ANFIS), while the optimization of the three independent parameters significant to the photocatalytic process was carried out by a genetic algorithm (GA) and RSM methods. The low standard error of prediction (SEP) of 0.56-1.75% and high coefficient of determination (R²) greater than 0.96 for the models developed indicated that they adequately predicted the photodegradation process with high accuracy in the order of ANFIS > ANN > RSM. The process optimization results from the developed models showed that GA performed better than RSM. The best optimal condition (3.29 g/L catalyst dosage, 45.85 min irradiation time, and 3.13 effluent pH) that resulted in maximum degradation efficiency of 99.46% was achieved by the ANFIS model coupled with GA (ANFIS-GA).