Wavelength Dependence of the Transformation Mechanism of Sulfonamides Using Different LED Light Sources and TiO2 and ZnO Photocatalysts

Application of BiOX Photocatalyst to Activate Peroxydisulfate Ion-Investigation of a Combined Process for the Removal of Organic Pollutants from Water

The persulfate-based advanced oxidation processes employing heterogeneous photocatalysts to generate sulfate radicals (SO4•−) from peroxydisulfate ion (PDS, S2O82−) have been extensively investigated to remove organic pollutants. In this work, BiOX (X = Cl, Br, and I) photocatalysts were investigated to activate PDS and enhance the transformation rate of various organic substances under UV (398 nm) and Vis (400–700 nm) radiation. For BiOCl and BiOBr, in addition to excitability, the light-induced oxygen vacancies are decisive in the activity. Although without organic substances, the BiOI efficiency highly exceeds that of BiOBr and BiOCl for PDS activation (for BiOI, 15–20%, while for BiOBr and BiOCl, only 3–4% of the PDS transformed); each BiOX catalyst showed enhanced activity for 1,4-hydroquinone (HQ) transformation due to the semiquinone radical-initiated PDS activation. For sulfamethoxypyridazine (SMP), the transformation is driven by direct charge transfer, and the effect of PDS was less manifested. BiOI proved efficient for transforming various organic substances even under Vis radiation. The efficiency was enhanced by PDS addition (HQ is wholly transformed within 20 min, and SMP conversion increased from 40% to 90%) without damaging the catalyst; its activity did change over three consecutive cycles. Results related to the well-adsorbed trimethoprim (TRIM) and application of biologically treated domestic wastewater as a matrix highlighted the limiting factors of the method and visible light active photocatalyst, BiOI.

Acacia nilotica Pods’ Extract Assisted-Hydrothermal Synthesis and Characterization of ZnO-CuO Nanocomposites

This work represents a novel combination between Acacia nilotica pods’ extract and the hydrothermal method to prepare nanoparticles of pure zinc oxide and pure copper oxide and nanocomposites of both oxides in different ratios. Five samples were prepared with different ratios of zinc oxide and copper oxide; 100% ZnO (ZC0), 75% ZnO: 25% CuO (ZC25), 50% ZnO: 50% CuO (ZC50), 25% ZnO: 75% CuO (ZC75), and 100% CuO (ZC100). Several techniques have been applied to characterize the prepared powders as FTIR, XRD, SEM, and TEM. The XRD results confirm the formation of the hexagonal wurtzite phase of zinc oxide and the monoclinic tenorite phase of copper oxide. The microscopy results show the formation of a heterostructure of nanocomposites with an average particle size of 13–27 nm.