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New materials with general formula Ba0.925Bi0.05□0.025(Ti0.65Zr0.30Sn0.05)O3 (symbolized BBiTZS) were prepared by high-temperature solid-state reaction. The room X-ray diffraction pattern suggests a cubic perovskite structure. The thermal variation of the permittivity at different frequencies showed a relaxor ferroelectric behavior. The Raman spectroscopy was in accordance of the dielectric measurements. The diffuse phase transition parameters were determined from the modified Curie–Weiss law, while the relaxor behavior was highlighted by a good fit to the Vogel–Filcher relationship. The capacitance-potential (Csc−2 − E) graph at pH ∼ 7 is characteristic of n-type behavior with a flat band potential (Efb) of −0.52 VSCE and an electron density (NA) of 2.7 × 1018 cm−3. The Electrochemical Impedance Spectroscopy, measured in the region (1 mHz - 105 Hz), showed a semicircle, assigned with the bulk property (27 kΩ cm2); a constant phase element (CPE) is responsible for the depletion angle (−9°). With an optical of 2.00 eV, the ferroelectric BBiTZS possesses appealing photocatalytic capability and was successfully experimented for the oxidation of Rhodamine B (Rh B) exposed to solar light. According to the band diagram, electrons from the conduction band of BBiTZS are injected into dissolved oxygen, resulting in O2· radicals, which are employed in the Rh B oxidation. UV–Visible spectrophotometry was used to follow the Rh B discoloration. On a solar irradiation of 97 mW cm−2, a conversion of 50% is achieved in Rh B solution (10 mg L−1) within 100 min., and the degradation follows a first order kinetic model with a half photocatalytic-life of 90 min.

Abstract The adsorption properties of activated carbon were successfully tested toward the elimination of hazardous HCrO4 − (30, 50, 70 and 100 mg L−1). The material was prepared from Algerian date pits by physical and chemical activations of ZnCl2/CO2 in the goal to develop the microporous volume. The characterization by N2 adsorption at 77 K, the mercury intrusion porosimetry and scanning electron microscopy showed important textural properties. CO2 increases the specific surface area (1192 m2 g−1) and pore volume (0.96 cm3 g). The HCrO4 − adsorption is described by a pseudo-first-order kinetic model, and the equilibrium data are fitted by the Langmuir model with a maximal adsorption capacity of 46.72 mg/g within 30 min and a constant K L (0.12 L g−1). The remaining HCrO4 − concentrations (8, 23, 32.5 and 43.5 mg L−1) were photocatalytically reduced on the hetero-system ZnCo2O4/TiO2 down to 5 mg L−1. The spinel ZnCo2O4, prepared by co-precipitation from the nitrates precursors and characterized by photoelectrochemistry, gives a conduction band of − 1.49 V SCE, more cathodic than the HCrO4 − level (0.53 V). Therefore, the photoelectrons transfer toward HCrO4 − species is achieved through TiO2 located midway between the spinel and chromate levels. The photocatalysis is investigated by varying the catalyst dose and HCrO4 − concentration. ZnCo2O4 has a gap of 1.82 eV and the best reduction efficiency (82%) was obtained under visible light (50 mW cm−2) and optimal conditions (HCrO4 − 23 mg L−1, pH ~ 7, ZnCo2O4/TiO2 50/50%) and follows a first-order kinetic with a rate constant of 3.86 × 10−3 min−1.