Rabeea D. Abdel-Rahim

In this work, the Hierarchical Copper Molybdate Nanostructures (HCM) photocatalyst was synthesized via a hydrothermal method and characterized using XRD, FTIR, UV-vis spectroscopy, SEM, TEM, and EDX analyses, confirming the formation of hierarchical nanocrystalline structures with a direct band gap of ~ 2.4 eV. The photocatalytic performance of HCM was systematically evaluated for the degradation of crystal violet (CV) dye under UV irradiation. Experimental design and process optimization were conducted using response surface method (RSM) and ANOVA, which demonstrated that pH, irradiation time, and catalyst dosage were the most influential variables, whereas dye concentration exerted a minor effect. Under optimized conditions (pH 10, 60 min, 15 mg/L CV, and 20 mg catalyst dosage), more than 99% CV dye degradation was achieved. Kinetic analysis demonstrated that the degradation followed a pseudo-first-order model, while thermodynamic studies indicated that the process is spontaneous, endothermic, and entropy-driven. Mechanistic evaluation confirmed that reactive oxygen species (·OH, O _2· , HOO·) generated through electron–hole separation played a dominant role in CV mineralization. In addition, HCM exhibited significant antimicrobial activity against bacterial and fungal strains, supporting its multifunctional potential. Overall, the findings highlight HCM as a highly efficient, low-cost, and environmentally friendly photocatalyst with promising applications in wastewater treatment and environmental remediation.

Hydroquinone is a phenolic compound widely used in industry and cosmetics, yet its toxicity has raised global environmental and health concerns. It has been listed by both the US EPA and the European Union as a priority contaminant for monitoring in aquatic systems. In this proof-of-concept (PoC) study, silver nanowires (Ag-NWs) were synthesized via a modified one-pot polyol methodology and characterized by various techniques, including TEM, EDX, SEM, XRD, and UV–vis spectroscopy. The Ag-NWs exhibited peroxidase-like activity, catalyzing the oxidation of TMB/H₂O₂ to yield a blue product. This activity was effectively suppressed by hydroquinone, forming the basis of a simple colorimetric sensing approach. The PoC method showed linearity over 0.08–0.8 µg/mL with a LOD of 26 ng/mL. Furthermore, it was preliminarily applied to tap water, river water, and medicated cream samples, demonstrating acceptable recovery in preliminary applications. As a PoC, the study establishes the feasibility of the Ag-NWs–TMB–H₂O₂ system for hydroquinone detection, while recognizing that comprehensive reproducibility assessment and temporal stability evaluation are required in future work.

Recycling gold from electronic waste offers significant benefits for both environmental protection and resource sustainability. However, this process presents considerable challenges due to high costs, prolonged processing times, and interference from coexisting metals. In this study, we synthesized a hybrid mesoporous nanocomposite comprising platelets-like CoNi₂S₄ incorporated with g-C₃N₄ nanosheets (CoNi₂S₄@g-C₃N₄) for the selective recovery of gold (Au(III)) ions from spent computer motherboards. Comprehensive characterization of the CoNi₂S₄@g-C₃N₄ nanocomposite was conducted, including its physicochemical properties, textural and structural characteristics, morphology, and elemental composition. The CoNi₂S₄@g-C₃N₄ extractor demonstrated an exceptional adsorption capacity of 200.6 mg g⁻¹, with high selectivity at pH 2, rapid equilibrium time of 60 minutes, and satisfactory reusability for over ten cycles. Adsorption isotherm and kinetic studies revealed that the CoNi₂S₄@g-C₃N₄ nanocomposite adheres to the Langmuir adsorption model and the pseudo-second-order kinetic model for Au(III) ion adsorption. Overall, this study introduces a viable adsorbent that shows considerable promise for industrial-scale Au(III) extraction from e-waste.