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The degradation performance of Cu-TiO2 nanomaterials towards levofloxacin (LFX) antibiotic was investigated under an environmentally benign visible LED light source. Cu-TiO2 nanomaterials were prepared using the reverse micelle sol–gel method with different copper content ranging from 0.25 to 1.0 wt% concerning titania. Characterization of Cu-TiO2 samples was performed by XRD, TEM, UV–Vis, BET, ICP-MS, FTIR and XPS techniques. 0.5 wt% Cu-TiO2 showed crystallite size below 6 nm, surface area (69.85 m2/g) and significant visible light absorption capacity. Both Cu1+ and Cu2+ are formed in lower Cu-doped TiO2 samples, whereas only Cu2+ is present in higher Cu-doped TiO2 samples as evident in XPS analysis. 0.5 wt% Cu-TiO2 has shown the optimum photocatalytic degradation of 75.5% under 6 h. of a visible light source. FTIR analysis of LFX adsorbed Cu-TiO2 materials indicated the pollutant–catalyst interaction, where the declining trend was observed in photocatalytic degradation efficiency for higher Cu-doped TiO2 samples due to copper-LFX complex formation. Copper-LFX complexes are formed due to the presence of Cu2+ in higher Cu-doped TiO2 nanomaterials, which might have hindered the photocatalytic activity under visible light. Effects of initial pollutant concentration, catalyst loading and visible light intensity on the degradation of LFX are studied. Photocatalytic degradation pathways of LFX using best performing Cu-TiO2 material were also proposed based on the LC–MS analysis. [ABSTRACT FROM AUTHOR]

A visible light-responsive redox-mediator-free calcium indium sulfide (CaIn2S4) and bismuth tungstate (Bi2WO6)–based direct dual semiconductor nanocomposites were prepared by combination of hydrothermal and wetness impregnation methods. The results substantiated the formation of CaIn2S4 marigold flowers, the flower-like structure of the Bi2WO6, and CaIn2S4/Bi2WO6 nanocomposites. UV–Vis-DRS analysis confirmed that visible light response of Bi2WO6 was considerably enhanced after combining with CaIn2S4. The inter-cross-sectional charge carrier transfer during photocatalysis using synthesized catalysts was studied by determining the band position of Bi2WO6 and CaIn2S4, and photoluminescence analysis. The adsorption of rhodamine B (RhB) dye study revealed that after coupling with CaIn2S4, the adsorption capacity of Bi2WO6 was significantly improved. For 15%-CaIn2S4/Bi2WO6, 38% of RhB dye was adsorbed, whereas it was 27% for bare Bi2WO6. The 15%-CaIn2S4/Bi2WO6 nanocomposite showed higher percentage degradation for RhB (82%) dye as compared to the other percentage loaded composites, bare Bi2WO6 (59%) and CaIn2S4 (72%). Photoluminescence results revealed that photo-generated electron–hole pair recombination rate was drastically suppressed after coupling with CaIn2S4 which may be presumed to inter-cross-sectional transfer of photo-generated charge carriers. The synergic effect of enhanced adsorption capacity and efficient separation of electron–hole pairs were accountable for the enhanced photodegradation efficiency under visible light. [ABSTRACT FROM AUTHOR]

A facile way of recovering 3d transition metals of industrial importance from spent lithium-ion batteries (LIBs) without using any surfactants has been developed. Mn- and Co-rich spent LIBs were chosen as sustainable sources for recovering the oxides of the respective elements. The physical dismantling of Li-ion batteries, chemical leaching with 2 M acetic acid, precipitation with ammonium carbonate, hydrothermal conditioning and calcination at 650 °C led to the facile formation of spherical spinel MnCo2O4 with very high morphological selectivity. The obtained spherical MnCo2O4 was identified by various advanced characterization techniques. Detailed electrochemical characterization revealed that the recovered spheres of spinel MnCo2O4 were effective in catalyzing the oxygen evolution reaction (OER) in 1 M KOH and required an overpotential of 358 and 400 mV to generate a current density of 5 and 10 mA cm−2, respectively, with a relatively low catalyst loading (0.001025 g cm−2). Comparative electrocatalytic studies carried out with recovered LiCoO2, recovered LiXMnOX+1 and commercially available catalysts such as RuO2 (c-RuO2), Co3O4 (c-Co3O4) and MnO2 (c-MnO2) revealed that the recovered spheres of spinel MnCo2O4 were more effective OER catalysts than the recovered LiCoO2, recovered LiXMnOX+1, c-Co3O4 and c-MnO2 and exhibited comparable activity to that of c-RuO2 with very little difference in overpotential (∼50 mV) at current densities of 5 and 10 mA cm−2. With such a low catalyst loading, the observed electrocatalytic performance in water oxidation of a material recovered from waste is highly significant and will surely attain greater industrial importance when the recycling of spent LIBs from electronic wastes is considered. [ABSTRACT FROM AUTHOR]