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In this work, TiO2 and Anderson-type polyoxometalates (Ni, Co, and Fe) thin-film composites were fabricated. The composites were characterized by FTIR and Raman spectroscopy, diffuse reflectance, and scanning electronic microscopy. The methylene blue (MB) photocatalytic degradation on the composites under UV irradiation was studied. Spectroscopic results verified the modification of TiO2 thin films. Optical and morphological properties changed after TiO2 modification. The largest change in the optical band gap was observed for the FePOM/TiO2 system, which reported a value of 3.05 eV. The POM/TiO2 systems were more efficient in methylene blue (MB) adsorption than bare TiO2. Furthermore, the modified films were more efficient than bare TiO2 during MB photodegradation tests. The NiPOM/TiO2 and the CoPOM/TiO2 were the most efficient in the MB adsorption, reaching ~20%. The NiPOM/TiO2 and the CoPOM/TiO2 composites were the most efficient in the photodegradation process, reaching ~50% of MB removal. The stability tests indicated that composite films were moderately stable after the three performed reusability cycles. Thus, these results suggest that POM modification of TiO2 can improve the adsorption and photodegradation capacity of semiconductors. [ABSTRACT FROM AUTHOR]

In the information contained herein, we fabricated biochar by means of a pyrolysis process; it used Prosopis juliflora waste (PJW) as a biomass source. The physical and chemical material characterization was carried out through FTIR, thermogravimetric, BET-N2 isotherm, and SEM-EDX assays. We studied the methylene orange (MO) adsorption onto PWJ biochar. The PJW biochar displayed a maximum percentage of MO removal of 64%. The results of the adsorption study indicated that Temkin isotherm was suitable to describe the MO adsorption process on PJW biochar; it suggests that the MO adsorption on PJW biochar could be a multi-layer adsorption process. Results showed that the pseudo-second-order model was accurate in demonstrating the MO adsorption on PJW (k2 = 0.295 g mg−1min−1; qe = 8.31 mg g−1). Furthermore, the results made known that the MO removal by PJW biochar was endothermic (ΔH = 12.7 kJ/mol) and a spontaneous process (ΔG = −0.954 kJ/mol). The reusability test disclosed that after four consecutive adsorption/desorption cycles, the PWJ biochar reduced its MO removal by only 4.3%. [ABSTRACT FROM AUTHOR]

In this work, we fabricated and characterized ZnO and TiO2 thin films, determining their structural, optical, and morphological properties. Furthermore, we studied the thermodynamics and kinetics of methylene blue (MB) adsorption onto both semiconductors. Characterization techniques were used to verify thin film deposition. The semiconductor oxides reached different removal values, 6.5 mg/g (ZnO) and 10.5 mg/g (TiO2), after 50 min of contact. The pseudo-second-order model was suitable for fitting the adsorption data. ZnO had a greater rate constant (45.4 × 10−3) than that of TiO2 (16.8 × 10−3). The removal of MB by adsorption onto both semiconductors was an endothermic and spontaneous process. Finally, the stability of the thin films showed that both semiconductors maintained their adsorption capacity after five consecutive removal tests. [ABSTRACT FROM AUTHOR]

Currently, many investigations have focused on the analysis of the antioxidant capacity of extracts from agro-industry wastes, thanks to their content in secondary metabolites such as phenols, flavonoids, anthocyanins, and carotenes, and their ability to react with free radicals and various oxygen reactive species. In this work, extracts of the Vaccinium meridionale fruit-shell was used to determine the antioxidant activity against singlet oxygen and free radicals 2,2-diphenyl-1-picrylhydracil (DPPH) and 2,2'-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS). The analysis of the total phenolic content (TPC) of the extract showed a significant content of phenolic groups (around 99.30 ± 3.15 mg of gallic acid/100 g of fresh fruit). On the other hand, the characterization by liquid chromatography (HPLC-DAD) showed the presence in the extract of six anthocyanins with the larger relative abundance (delphinidine-3-glucoside, delphinidine-3-arabinoside, cyanidine-3-glucoside, cyanidine-3- arabinoside, cyanidine-3-galactoside, and an unidentified anthocyanin). The percentage of deactivation of singlet oxygen was determined at different concentrations of the ethanolic extract, with a value of 51% at a concentration of 0.4 mg/mL, while the IC50 by the ABTS method was 311.5 µg/mL and by the DPPH method of 65.96 µg/mL. [ABSTRACT FROM AUTHOR]

In this work, tetra(4-carboxyphenyl)porphyrin (TCPP) and two Anderson-type polyoxomolybdates (containing Cu and Zn, respectively; CuPOM, ZnPOM) were synthesized and deposited on TiO2 thin films. The properties of the obtained materials were characterized through UV–vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), diffuse reflection spectroscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The adsorption and photodegradation under the visible light irradiation of methylene blue (MB) were studied for TiO2, TCPP/TiO2, TCPP/CuPOM/TiO2 and TCPP/ZnPOM/TiO2 thin films in aqueous solution. The results of the diffuse reflectance showed two bands in the visible light spectrum for the TCPP/POM/TiO2 systems compared to unmodified TiO2 that does not show any bands in the same region of the spectrum. The TCPP/POM/TiO2 systems showed a higher removal of MB, with an adsorption rate near to 31% for the TCPP/CuPOM/TiO2 film compared to 9% adsorption on the TiO2 film. The kinetic results show that the pseudo-second order model was the best fitting model for the MB adsorption process onto fabricated materials. The photodegradation studies under visible light showed a better performance on TCPP/POM/TiO2 thin films, with an efficiency in the MB photodegradation of near 49% and 44% in aqueous solution for TCPP/CuPOM/TiO2 and TCPP/ZnPOM/TiO2, respectively. The reusability test indicated that the porphyrin films are moderately stable after the performed cycles. [ABSTRACT FROM AUTHOR]

Currently, many investigations have focused on the analysis of the antioxidant capacity of extracts from agro-industry wastes, thanks to their content in secondary metabolites such as phenols, flavonoids, anthocyanins, and carotenes, and their ability to react with free radicals and various oxygen reactive species. In this work, extracts of the Vaccinium meridionale fruit-shell was used to determine the antioxidant activity against singlet oxygen and free radicals 2,2-diphenyl-1-picrylhydracil (DPPH) and 2,2'-azino--bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS). The analysis of the total phenolic content (TPC) of the extract showed a significant content of phenolic groups (around 99.30 ± 3.15 mg of gallic acid/100 g of fresh fruit). On the other hand, the characterization by liquid chromatography (HPLC-DAD) showed the presence in the extract of six anthocyanins with the larger relative abundance (delphinidine-3-glucoside, delphinidine-3-arabinoside, cyanidine-3-glucoside, cyanidine-3- arabinoside, cyanidine-3-galactoside, and an unidentified anthocyanin). The percentage of deactivation of singlet oxygen was determined at different concentrations of the ethanolic extract, with a value of 51% at a concentration of 0.4 mg/mL, while the IC50 by the ABTS method was 311.5 µg/mL and by the DPPH method of 65.96 µg/mL. [ABSTRACT FROM AUTHOR]

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