In this study, nanocrystalline ZnNd_xFe_2−xO₄ ferrites with x = 0.0, 0.01, 0.03 and 0.05 were fabricated and used as a catalyst for dye removal potential. The effect of Nd³⁺ ions substitution on the structural, optical and photo-Fenton activity of ZnNd_xFe_2−xO₄ has been investigated. The addition of Nd³⁺ ions caused a decrease in the grain size of ferrites, the reduction of the optical bandgap energies and thus could be well exploited for the catalytic study. The photocatalytic activity of the ferrite samples was evaluated by the degradation of Rhodamine B (RhB) in the presence of H₂O₂ under visible light radiation. The results indicated that the ZnNd_xFe_2−xO₄ samples exhibited higher removal efficiencies than the pure ZnFe₂O₄ ferrites. The highest degradation efficiency was 98.00%, attained after 210 min using the ZnNd_0.03Fe_1.97O₄ sample. The enhanced photocatalytic activity of the ZnFe₂O₄ doped with Nd³⁺ is explained due to the efficient separation mechanism of photoinduced electron and holes. The effect of various factors (H₂O₂ oxidant concentration and catalyst loading) on the degradation of RhB dye was clarified.

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).

The coal gasification wastewater figures prominently among types of industrial effluents due to its complex and phenolic composition, posing great difficulty for conventional water treatment processes. Since the coking wastewater is toxic and mutagenic to humans and animals, treatment of coal gasification wastewater is genuinely necessary. In this study, we established a lab-scale A2O (Anaerobic-Anoxic—Oxic) with moving bed biological reactor (MBBR) system and evaluated some water indicators of wastewater pretreated with internal electrolysis, of wastewater output of the established A2O-MBBR system, and of the wastewater treated by the combination thereof. The wastewater was taken from a coking plant at Thai Nguyen Iron and Steel Joint Stock Company in Vietnam. COD, BOD₅, NH₄⁺-N, phenol, and pH of the input coal gasification wastewater were 2359, 1105, 319, 172 mg/L, and 8 ± 0.1, respectively. The conditions of internal electrolysis were as follows: 720 min of reaction time, pH = 4, 25 g/L Fe-C dosage, and 100 mg/L PAM dosage. After internal electrolysis process, the removal of COD, BOD₅, NH₄⁺-N, and phenol were 53.7%, 56.7% 60.5%, and 73.3%, respectively. After 24 h of treatment, the treatment efficiencies of the combined treatment process are as follows: 100% phenol removal, 71.3% of TSS removal; 97.7% reduction of BOD₅, and 97.1% reduction of COD; total N content reduced by 97.6%; total P content decreased by 81.6%; and NH₄⁺-N content decreased by 97.5%. All above indicators after treatment have met QCVN 52: 2017/BTNMT (column A) Vietnamese standard for steel industry wastewater.

The co-precipitation method was employed to synthesize a set of ZnAl hydrotalcite materials modified by Cu²⁺. The synthesized materials have a similar lamellar structure to that of hydrotalcite. The distance between layers is in the range of 7.73–8.56 Å. The network parameters a and c ranged from 3.058 to 3.074 Å and from 23.01 to 24.44, respectively. According to the IUPAC classification, the composites possess a mesoporous structure which belongs to class IV, type H 3. Particularly, the absorption edge shifts strongly to the visible light region when increasing the molar ratio of Cu²⁺ in the samples from 0 to 3.5. The photocatalytic activity of the synthetic materials was evaluated through the degradation efficiency of rhodamine-B (Rh-B) in the water and colorants in textile wastewater. The present study was the first to synthesize a material sample that contains a molar ratio of Cu²⁺ in the range of 2.5–3.5 and has high catalytic activities. They were able to degrade Rh-B at a high concentration (100 ppm) with a conversion rate of approximately 90% after 240 min of irradiation using a 30 W LED light. The catalytic activity of the composites depends on the molar ratio of modified Cu²⁺, the value of environmental pH, the H₂O₂ concentration and the irradiation time.

Rare earth elements (Ln: Sm, Eu, Tb, Dy) were complexed with caffeic acid (Caf), a natural phenolic compound, to synthesize novel luminescent complexes with enhanced biological activities. The complexes, formulated as Ln(Caf)₃·4H₂O, were characterized using infrared spectroscopy (IR), thermogravimetric analysis (TGA/DTA), mass spectrometry (MS), and fluorescence spectroscopy. Structural studies confirmed the coordination of caffeic acid via carboxylate and hydroxyl groups, forming stable hexacoordinate complexes. Luminescence analysis revealed intense emission bands in the visible spectrum (480–700 nm), attributed to f-f transitions of Ln³⁺ ions, with decay lifetimes ranging from 0.054 to 0.064 ms. Biological assays demonstrated significant antibacterial activity against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, with inhibition zones up to 44 mm at 200 µg/mL. The complexes also exhibited potent anticancer activity against MCF7 breast cancer cells, with Sm(Caf)₃·4H₃O showing the lowest IC₅₀ value (15.5 µM). This study highlights the dual functionality of rare earth metal-caffeic acid complexes as promising candidates for biomedical imaging and therapeutic applications.