In this study, gold-reduced graphene oxide (Au@rGO) nanocomposite has been synthesized by repurposing electronic waste and dry batteries. This innovative approach involved utilizing the graphite rod from dry batteries to produce reduced graphene oxide (rGO), which was subsequently modified through the incorporation of gold nanoparticles obtained from recycled electronic waste. This methodology marks a significant breakthrough in electronic waste recycling, presenting a cost-effective and sustainable means of creating novel nanocomposites for applications in photocatalysis and adsorption, particularly in the removal of crystal violet (CV) from aqueous media. The synthesized Au@rGO nanocomposite was characterized using X-ray diffraction, scanning electron microscopy, energy dispersed X-ray, and N₂ adsorption/desorption. Parameters that affect the adsorption and photocatalytic degradation of CV dye have been studied in detail. The optimal conditions for CV adsorption and photocatalytic degradation were pH of 10, equilibrium time of 30 min, CV concentration of 10 mg/L and adsorbent dosage of 40 mg. Furthermore, the isotherm and kinetics of CV removal were also studied. The removal of CV dye using adsorption and photocatalytic degradation techniques reached 95% and 99%, respectively. Consequently, the results showed that photocatalytic degradation of CV dye onto the mesoporous Au@rGO nanocomposite is more proper way than the adsorption technique for removing the CV dye from aqueous media. The designed photocatalyst has high efficiency and it can be reused and activated several times so it can be used in real water treatment applications.

The design of potential nanosensors based on nanometric metals have been widely used for screening of various biomolecules and agents. One‐dimension (1D) silver nanowires (AgNWs) construction were synthesized by the polyol method and employed to detect of H₂O₂. The addition of various Ag‐source (AgNO₃) concentrations of 0.15, 0.3, and 0.6 M lead to form of different AgNWs diameter of 0.05, 0.137, and 0.27 μm, respectively. The sensing property and electrochemical activity were enhanced with the decreasing of the AgNWs diameter, and followed the order of AgNWs0.05> AgNWs0.137> AgNWs0.27. Moreover, the morphological structure of good desperation, long wire length, and 1D orientation play a key role in the electrocatalytic efficiency of the designed electrodes. The facile diffusion of electron/molecules inner/outer the surface, the high volume to mass ratio ascertain the highly efficient electrocatalyst with high stability. AgNWs0.05, as an electrode surface, ascertains nonenzymatic sensors to detect H₂O₂ with high stability, high sensitivity, good selectivity, and reasonable reproducibility. The detection limit was low as 0.05 μM with a wide linear range of up to 1075 μM. Also, AgNWs0.05 shows a highly selective sensor for detecting H₂O₂ in complex mediums such as milk samples with a high recovery of 99.5‐100%. Therefore, the AgNWs0.05 can be used to detect H₂O₂ in various complex samples such as milk.

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.

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.