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Environmental problems on a global scale have become more prominent with the population growth. For the removal of organic contaminants, the solar energy and environmentally friendly photocatalysis are needed to substitute the fossil fuels. In this contribution, we report the synthesis, characterization and photocatalytic capability of CuAl2O4 nanoparticles. The spinel was elaborated by nitrate route and characterized physically and electrochemically for their correlations and application in photocatalysis through the degradation of Basic Red 46 (BR 46), a hazardous dye under visible illumination. The effects of several operational factors like the pH, catalyst dose and initial dye BR 46 concentration were optimized. The results revealed that the photocatalytic performance reached 93% at pH 10, 1 g/L of catalyst dose at a concentration of 10 mg/L of BR 46 within 120 min of irradiation. The quasi-total mineralization was confirmed by the total organic carbon (TOC) and dissolved organic carbon (DOC). Additionally, the prepared photocatalyst possesses a good cyclability with no significant change after five successive photocatalytic cycles. Furthermore, the radical scavenger tests revealed that the specie O2·− and the holes h+ have the significant effects on the removal of BR 46. Based on the latest results, a photocatalytic mechanism was proposed. [ABSTRACT FROM AUTHOR]

Nickel is a hazardous metal with a harmful effect on the health and environment. In this work, the photocatalytic reduction of Ni2+ was examined onto the hetero-system CoMn2O4/TiO2 under visible light irradiation. The spinel CoMn2O4 is prepared by co-precipitation and characterized in detail to correlate its structural, textural, morphological, compositional, optical and photoelectrochemical features. The effects of pH, catalyst dose and Ni2+ concentration were optimized. The Ni2+ reduction increased with decreasing both the catalyst dose and pH. The highest performance was obtained at pH 7.4, a catalyst dose of 1 g/L and Ni2+ concentration of 10 mg L−1 with a removal abatement of 88% after 180 min irradiation. The data were suitably fitted by the pseudo-first-order kinetic reaction with an apparent constant of 0.027 min−1. Besides, the durability and the stability of the hetero-system CoMn2O4/TiO2 were evaluated by four consecutive catalytic cycles. [ABSTRACT FROM AUTHOR]

The spinel MgFe 2 O 4 was synthesized by the sol-gel procedure, which exhibits a distinct single-phase X-ray diffraction pattern. Thermal analysis (TG) revealed that crystallization occurs above 700 °C yielding a cubic symmetry (Space Group: Fd−3 m). Scanning electron microscopy revealed nano-spherical structures with an average length of ∼0.6 μm. A direct transition of 2.16 eV determined from the diffuse reflectance is associated with the internal electron transfer Fe3+: d−d, in conformity with the red colour of the oxide. The activation energy (E a = 0.14 eV), derived through the thermal variation of the conductivity, caused by the low polaron hopping among mixed valences Fe3+/2+ with weak electron mobility (μ e = 2 × 10−6 m2V−1s−1). The capacitance versus polarization potential indicated n -type semi-conductivity, supported by chrono-amperometry, with a flat band potential (E fb) of 0.27 V SCE. The effectiveness of MgFe 2 O 4 as a photocatalyst for the oxidation of Bromothymol Blue (BB) under solar light was assessed, while the outcomes showed a 65% decrease at pH 3 within 180 min. The BB oxidation follows a first-order kinetic model with a rate constant K app of 0.0053 min−1 (t 1/2 = 110 min). A BB degradation mechanism was proposed per the results gathered through Mott-Schottky and UV–vis analyses. In summary, this current study has demonstrated that MgFe 2 O 4 has promising potential as an alternative photocatalyst for environmental cleansing. [Display omitted] • Successful synthesis of MgFe 2 O 4 through sol gel method. • The physicochemical characteristics of the photocatalyst were thoroughly examined. • The photocatalytic capability of MgFe 2 O 4 was evaluated by the breakdown of Bromothymol Blue under sunlight. • A feasible sequence of chemical reactions was proposed to explain the degradation mechanism. [ABSTRACT FROM AUTHOR]