A CuO-loaded SrTiO₃ catalyst showed highly photocatalytic activity for H₂ evolution. This catalyst was prepared by an impregnation method and characterized by XRD, TEM, BET, XPS, Uv-vis DRS and PL techniques. Under optimum conditions, the best rate of H₂ evolution of the CuO-loaded SrTiO₃ catalyst is 5811 µmol h⁻¹g⁻¹, whereas it is a mere 34 µmol h⁻¹g⁻¹ for the pure SrTiO₃. High efficiency, low cost and good stability are some of the merits that underline the promising potential of CuO-loaded SrTiO₃ in the photocatalytic hydrogen.

In recent years, photocatalysis has been used as an environmentally friendly method for the degradation of organic pigments in water. In this study, Ce³⁺/Ce⁴⁺-doped ZrO₂/CuO as a mixed semiconductor oxide was successfully prepared by a one-step hydrothermal method. The Ce³⁺/Ce⁴⁺-doped ZrO₂/CuO has shown high degradation efficiency of methylene blue (MB), and the maximum degradation percentage was observed to be 94.5% at 180 min under irradiation visible light. The photocatalytic activity increases significantly by doping Ce³⁺/Ce⁴⁺ in ZrO₂/CuO for MB degradation. Ce³⁺/Ce⁴⁺ doping is shown to reduce the (e^-/h⁺) recombination rate and improve the charge transfer, leading to enhanced photocatalytic activity of materials. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), FTIR, EDS, BET and diffuse reflectance spectroscopy (DRS).

In this study, we report on the preparation of copper oxide/strontium titanate/multi-walled carbon nanotube (CuO/STO/MWCNTs) nanocomposites and their photocatalytic activity for degradation of dye under visible light. The crystalline structures of the nanocomposites were investigated by an X-ray diffraction (XRD) technique, which explored the successful fabrication of CuO/STO/MWCNTs nanocomposites, and the cubic STO phase was formed in all samples. For the morphological study, the transmission electron microscope (TEM) technique was used, which had proved the successful preparation of CuO and STO nanoparticles. The energy dispersive X-ray spectroscopy (EDX), dark field scanning transmission electron microscope (DF-STEM-EDX mapping), and X-ray photoelectron spectra (XPS) analysis were performed to evidence the elemental composition of CuO/STO/MWCNTs nanocomposites. The optical characteristics were explored via UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) techniques. These studies clearly indicate the effect of the presence of CuO and MWCNTs on the visible absorption of the CuO/STO/MWCNTs nanocomposites. The photocatalytic activity of CuO/STO/MWCNTs nanocomposites was evaluated by the degradation of methylene blue (MB) dye under visible light irradiation, following first-order kinetics. Among the different x% CuO/STO/MWCNTs nanocomposites, the 5 wt.% CuO/STO/MWCNTs nanocomposites showed the highest photocatalytic efficiency for the degradation of MB dye. Moreover, the 5% CuO/STO/MWCNTs showed good stability and recyclability after three consecutive photocatalytic cycles. These results verified that the optimized nanocomposites can be used for photocatalytic applications, especially for dye degradation under visible light.

In this paper, Zr(IV) nitrate solution decomposed from Viet Nam zircon concentrate was the source of zirconium extraction by liquid-liquid extraction (L.L.E). The FT-IR and UV-Vis spectra confirmed the extraction of Zr(IV) by D2EHPA/p-xylenes. There were four stages for the purification of impurities from the Zr matrix. First, the extraction of elements in 3.0 M HNO₃ by 50% D2EHPA/p-xylenes was conducted. Second, two scrubbing cycles of impurities using 6.0 M HNO₃, 76.5% of the total amount of Zr(IV) were retained in the organic phase, and 23.5% remained in the aqueous phase. Third, the stripping of a macro amount of zirconium from loaded D2EHPA has been effectively carried out using 1.5 M H₂SO₄ with a stripping efficiency of 99.6%. Fourth, concentrated ammonia was added to the solution Zr(IV) after stripping extraction to form precipitate for calcination at 550 °C for the final products. The refined products were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), EDS, XRF, and diffuse reflectance spectroscopy. The ZrO₂ has high purity, is nanospherical, and has a uniform sphere-like morphology with small grain size of less than 30 nm and a bandgap value of about 3.30 eV.