Studies on photocatalytic degradation of Rhodamine B using the valentinite Sb₂O₃

A facile hydrolysis-precipitation was used to elaborate antimony oxide Sb₂O₃ (valentinite) and to study its semiconducting and photo-electrochemical properties. The X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis diffuse reflectance, Raman and FTIR spectroscopies were used to characterize the oxide. The XRD analysis indicates an orthorhombic phase (SG: Pccn) with a crystallite size of 102 nm. The optical measurements gave a direct gap of 3.32 eV due to a charge transfer O²⁻: 2p–Sb³⁺: 6s while the capacity-potential (C ⁻²–E) plot provides a flat band potential of − 0.46 V_Ag/AgCl. The valence and the conduction bands are located at (− 7.29 eV/2.56 V) and (− 3.97 eV/− 0.76 V), and the energy band diagram of the junction Sb₂O₃/KOH shows the efficacy of Sb₂O₃ as photocatalyst. As application, 81% of Rhodamine B (Rh B), a recalcitrant dye with an initial concentration of 5 mg L⁻¹, were mineralized after 7 h under UV light by Sb₂O₃. According to the inhibitors study, the ^·OH radical is the first active specie in the Rh B photo-oxidation, followed by O₂^·−. The photodegradation follows a zero order kinetic with a photocatalytic half time of 3.8 h, smaller than the photolysis (10.5 h) under UV light (254 nm).