Analysis of the photocatalytic activity of La0.9Sr0.1Fe0.8Co0.2O3±Î´ perovskite as a catalyst in the degradation of RB-5 dye.

The photocatalytic efficiency of some semiconductors depends mainly on their morphological, optical, and structural properties, which can be modified by varying the calcination temperature. In order to evaluate how these properties change, as a function of temperature in a AA'BB'O3 perovskite material, La0.9Sr0.1Fe0.8Co0.2O3±Î´ (LSFC) was synthesized by the Pechini method and calcined at different temperatures (600 °C, 700 °C, 800 °C, and 900 °C). All the samples were characterized structurally, morphologically, and optically by XRD, SEM, and UV-Vis spectroscopy. Additionally, specific surface area and pore size distribution were calculated by BET and BHJ methods. LSFC was evaluated as photocatalyst material, estimating the degradation of reactive black 5 (RB5), employing as irradiation source UV light and sunlight. The obtained results display a clear tendency between the photoactivity and the heat treatment: degradation percentage decreases as the calcination temperature increases mainly due to the crystal and grain size and, furthermore, loss of porosity and the decrease in surface area, affecting the photocatalytic activity (98%, 95%, 74%, and 50% degradation, respectively). All the ceramic samples follow a pseudo-first-order reaction.

Degradation of diclofenac by H2O2 activated with pre-magnetization Fe0: Influencing factors and degradation pathways.

Diclofenac sodium (DCF) is frequently detected as a non-steroidal pharmaceutical in the aquatic environment. In this study, the degradation of DCF in two heterogeneous systems, pre-magnetization Fe0/H2O2 (Pre-Fe0/H2O2) and Fe0/H2O2 system, was comparably studied. Our findings proved that Pre-Fe0 could significantly improve the degradation and dechlorination of DCF due to the change of Fe0 characteristics after pre-magnetization. Compared with Fe0/H2O2 process, Pre-Fe0/H2O2 process has 2.1-7.0 times higher rate constant for DCF degradation at different H2O2 dosages (0.25-2.0 mM), initial pH (3.0-6.0) and Fe0 dosages (0.25-1.5 mM). The characterizations by X-ray Photoelectron Spectroscopy and Electron Paramagnetic Resonance confirmed that the enhancement attributed to the increase of Fe0 corrosion and fast generation of OH. In addition, preliminary degradation mechanism was elucidated by major products identification using UPLC-MS, through which the degradation intermediates, such as 4-hydroxy-diclofenac or 5-hydroxydiclofenac, 2,6-dichloroaniline, phenylacetic acid, 1,3-dichlorobenzene and 2-aminophenylacetic acid were identified. Hydroxylation, decarboxylation, CN bond cleavage and ring-opening involving the attack of OH or other substances, were the main degradation mechanism. Therefore, Pre-Fe0/H2O2 process, which does not need extra energy and costly reagents, is an efficient and environmental-friendly process to degrade DCF.

Comparative study of the direct black removal by Fe, Cu, and Fe/Cu nanoparticles.

In this study, direct black dye removal was investigated using iron nanoparticles (Fe NPs), copper (Cu NPs), and Fe/Cu (Fe/Cu NPs). NPs were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Using a dose of 0.25 g L-1 of Fe, Cu, and Fe/Cu NPs, a degradation efficiency of 13, 26, and 43% respectively was obtained. For the 1.00 g L-1 dose, the efficiency increased to 100, 43, and 100%, respectively. Studies in anoxic and oxic conditions presented degradation rates, respectively, of 100 and 30% for Fe NPs, 90 and 50% for Fe/Cu NPs, and 40% in both reactions for Cu NPs, indicating that the mechanism of dye degradation by NPs is predominantly reducing under the conditions studied. The addition of EDTA decreased the dye removal rate for Fe, Cu, and Fe/Cu NPs at 27, 10, and 35%, respectively. In addition to the degradation, the adsorption phenomena of the by-products formed during the reaction were confirmed by the Fourier transform infrared (FTIR) analysis and verified by the desorption tests. Fe and Fe/Cu NPs showed the highest efficiency in direct black dye reductive degradation and adsorption of by-products, removing 100% of the dye at a dose of 1 g L-1 within 10 min of reaction. Graphical abstracts ᅟ.