Synergetic adsorption-photocatalysis process for water treatment using TiO2 supported on waste stainless steel slag

Quantum and experimental investigation of the application of Crassostrea gasar (mangrove oyster) shell-based CaO nanoparticles as adsorbent and photocatalyst for the removal of procaine penicillin from aqueous solution

The present study was designed to synthesize and characterize calcium oxide nanoparticles (using mangrove oyster shell as a precursor) and apply the synthesized nanoparticles as a photocatalyst to degrade procaine penicillin in an aqueous solution. The photocatalyst exhibited an average band gap of 4.42 eV, showed a maximum wavelength of absorbance in the UV region (i.e., 280 nm), and is a microporous nanoparticle with a particle diameter of 50 nm. The photocatalyzed degradation of the drug was conducted under natural sunlight, and the influence of parameters such as the period of contact, catalyst load, pH, initial drug concentration, and ionic strength was investigated concerning the degradation profile. The results obtained from response surface analysis indicated that an optimum degradation efficiency of about 93% can be obtained at a concentration, pH, and catalyst dosage of 0.125 M, 2, and 0.20 g respectively, at 0.902 desirabilities. The Langmuir-Hinshelwood, modified Freundlich, parabolic diffusion, pseudo-first-/second-order, and zero-, first-, and second-order kinetic parameters were tested to ascertain the best model that best described the experimental data. Consequently, the Langmuir-Hinshelwood, modified Freundlich, and pseudo-second-order models were accepted based on the minimum error and higher R² values. Based on the Langmuir-Hinshelwood rate constants for adsorption and photodegradation as well as the evaluated valence bond potential, the degradation of the drug first proceeded through the mechanism of adsorption and followed by the oxidation of the drug by superoxide (generated from the interaction of electrons that generated by through the absorption of UV radiation). The quantum chemical calculation gave evidence that pointed towards the establishment of strong agreement with experimental data and also showed that the carboxyl functional group in the drug is the target site for adsorption and subsequent degradation.

Br vacancy engineering in Cs3Bi2Br9 for photocatalytic NO oxidation under visible light

Photocatalysis using the visible light of the sun is an environmentally friendly method of eliminating the NOx pollutant from the ambient air. Although Cs₃Bi₂Br₉, a semiconductor with a band gap of 2.54 eV, may be a strong absorber of visible light, its photocatalysis towards the abatement of NOx is unknown. In this study, Cs₃Bi_2-xPb_xBr_9-x (0 ≤ x ≤ 0.0789) are used for the photocatalytic oxidation of NOx. A significant NO oxidation efficiency (80%) is observed over Cs₃Bi_2-xPb_xBr_9-x (x = 0.0443) under visible light, which is attributable to the Br vacancy (V_Br) brought about by Pb²⁺ doping. The presence of V_Br increased the ionic selectivity of in the oxidized NO. At higher Pb doping level, two HONOs adsorbed on the V_Br, linked, and then reduced by hot electrons to produce N₂O₂^2-. The di-azo coupling could passivate the activation of NO on the V_Br. This work advances the defect engineering of halide for the photo-driving solid-gas reaction in air.