Solid State Phenomena Vol. 385

Abstract: Perfluorooctane sulfonate (PFOS), a toxic and persistent pollutant, poses significant environmental and health risks, making its detection crucial. This study developed silver nanoparticle (AgNP)-modified screen-printed carbon electrodes (SPCEs) for on-site PFOS detection and compared them with glassy carbon electrodes (GCEs). AgNPs were electrodeposited at various concentrations (1–9 mM) using amperometry. SEM-EDS confirmed increasing silver deposition with higher AgNO₃ concentrations, and cyclic voltammetry showed enhanced current responses with increased silver content. Differential pulse voltammetry revealed that 5 mM Ag/SPCE achieved the highest PFOS detection signal (Δi = 11.218 µA), demonstrating the effectiveness of AgNP-modified SPCEs for PFOS detection.

Abstract: This study examines the effect of hydrazine hydrate levels on chemically reduced graphene oxide (GO) to synthesize reduced graphene oxide (rGO) for Pb (II) electrochemical detection. GO was prepared by the modified Hummers’ method and reduced with 1-5 mL hydrazine hydrate. FTIR analyzed changes in oxygen-containing groups. rGO samples were drop-cast onto screen-printed carbon electrodes (SPCEs) and characterized by SEM-EDX. Electrochemical behavior was evaluated by cyclic voltammetry (CV) in 5 mM [Fe (CN)₆]³⁻/⁴⁻ with 0.1 M KCl. rGO reduced with 3 mL hydrazine hydrate showed the highest current (52.45 ± 1.98 µA), a 196.6% increase over bare electrodes. This condition also gave the best detection of 1 ppm Pb (II) in 0.1 M acetate buffer (pH 5) via square wave anodic stripping voltammetry (SWASV), with a 135.0% signal enhancement. These results highlight the importance of hydrazine hydrate level on optimizing rGO for improved electrochemical properties, sensitivity, and reproducibility for Pb (II) detection.

Abstract: This research investigated the impact of Ag content supported on ZnO catalysts regarding the oxidation activity of DPM. The catalyst was synthesised through the doping of varying Ag concentrations on ZnO (e.g., 2, 4, 8, and 16 wt%) employing the incipient wetness impregnation technique. Characterisation of the synthesised catalyst was conducted utilising XRD, SEM, TEM, and H₂-TPR. The evaluation of oxidation activity and stability was performed through TGA. The characterisation findings substantiated the successful integration of Ag onto ZnO across all experimental conditions investigated. H₂-TPR profiles revealed two distinct regions of H₂ consumption: 1) at 200-400 °C, and 2) at 400-700 °C. These regions were attributed to the reduction of Ag₂O to Ag⁰ and the liberation of lattice oxygen from ZnO, respectively. An increase in Ag concentrations resulted in enhanced reduction reactions within the temperature spectrum of 400 to 700 °C, demonstrating a favourable trend towards improved reaction efficiency. The oxidation performance of DPM was markedly augmented by the Ag content, particularly at 16 wt%. Stability assessments indicated a consistent capability in facilitating DPM oxidation across five cycles. The concentration of oxygen exhibited a significant influence on the oxidation activity of DPM.

Abstract: Layered double hydroxides (LDHs) have achieved remarkable attention these days for their promising applications ins water remediation, owing to their excellent anion exchange capacity and robust structured modification possibility. In this study, Mg-Al LDH of different metal ion ratio (2:1, 3:1 and 4:1) were synthesized by co-precipitation and urea hydrolysis method. The as synthesized LDHs were characterized by Fourier Transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDX). A series of Cr (VI) removal efficacy were studied by batch adsorption method. The results indicated that removal of Cr (VI) from aqueous solution is pH dependent and a maximum Cr (VI) removal was achieved at pH 5. The Mg-Al LDH containing 2:1 metal ion ratio showed highest adsorption capacity irrespective of method of preparation. The equilibrium adsorption data are well supported by Langmuir isotherm (LI) and maximum loading capacities for Cr (VI) removal were 37.26 and 55.26 mg g⁻¹ for LDH MAC-21 and MAU-21, respectively suggesting that LDH obtained by urea hydrolysis method have shown better performance. The equilibrium kinetics data are well supported by pseudo-second order model for all LDH tested samples.