In this study, we prepared spheroid microstructures of monoclinic bismuth phosphate BiPO₄ by a facile solid-state reaction at 500 °C. The crystal structure was refined using the Rietveld method, where the crystal cell was resolved using a monoclinic system (parameters a, b, c, β) with space group P2₁/n. SEM images showed that the solid catalyst presented homogeneous morphologies. These BiPO₄ microparticles (BiP-500) have been used as photocatalysts to photodegrade, under UV light irradiation, three cationic dyes (Rhodamine B, RhB; Methylene Blue, MB; and Toluidine Blue, TB), three anionic dyes (Congo Red, CR; Orange G, OG; and Methyl Orange, MO) and mixtures of RhB-MB, RhB-OG and MO-OG organic dyes. The photodegradation efficiency of these BiP-500 microparticles is found to be optimal in the case of RhB solutions, RhB-MB and RhB-OG binary mixtures. The BiP-500 catalyst shows a high selectivity for the conversion of the mixture of dyes into CO₂ and H₂O. Total organic carbon analysis of an anionic dye and a cationic dye (RhB, OG and RhB-MB) confirms the mineralization of the pollutants in the presence of BiP-500 particles. The photocatalytic efficiency of our BiP-500 photocatalyst has been confirmed, with a view to facilitate applications in the field of the depollution of wastewater in the agricultural environment by the degradation of parathion-methyl (PM) as a pollutant.

This paper presents a new study on imidazole derivatives namely 1H-imidazole (IM), N-methylimidazole (MIM) and 1H-benzimidazole (BIM) as a corrosion inhibitor for brass in nitric acid medium. Electrochemical results demonstrate that the inhibition increases with a high concentration of imidazole derivatives; the inhibitory efficiency reaches a maximum of 94% at 10–2 mol L⁻¹ for BIM. SEM morphology and EDS analysis show that these derivatives are adsorbed onto the brass interface, the brass sample is effectively protected and the surface becomes relatively flat, which is more significant in the presence of 1H-benzimidazole. FTIR results confirm the retention of BIM on the interface of Cu-Zn alloys. In addition, quantum chemistry calculation manifests that the three derivatives can reveal high anticorrosion properties. Molecular dynamics simulation data manifest that the three imidazole derivatives can be adsorbed at the brass surface in a paralleled way, and have large binding energy. GRAPHICAL ABSTRACT

Polycrystalline bismuth phosphate BiPO₄ was synthesized by solid-state reaction at different temperatures varying from 500 to 900 °C. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and Raman spectroscopy. The low-temperature phase of BiPO₄ has monoclinic structure with a space group P2₁/n, and was transformed into the monoclinic phase P2₁/m with a slight distortion of monoclinic lattice when it was heated above 500 °C. The effect of the transformation on the structure, morphology and photocatalytic properties was examined. The photocatalytic activity of each sample, in presence of Rhodamine B (RhB) in aqueous solution, was carried out and analyzed under UV light irradiation. Photoexperiments showed that the material prepared at 500 °C is the best catalyst with degradation efficiency of the order of 96% after 12 min of reaction time under UV light irradiation. This high photocatalytic efficiency could be due to their structural and morphological changes. The photocatalytic degradation mechanism of RhB in the presence of the best photocatalyst BiP-500 °C is proposed. The stability of the catalyst was also examined by carrying out four successive tests of the degradation in the presence of BiP-500 °C. Total organic carbon (TOC) was used to further estimate the rate of mineralization in the presence of BiP-500 °C (83% TOC removal). Photoluminescence experiments performed under UV-laser light irradiation revealed emissions in the green-orange range, with optimal intensities for the mix systems observed at 550 °C.