Batch Adsorption Kinetics and Isotherm Modeling of Thiocyanate Using Reduced GO-Metal Oxide Nanocomposites

The elimination of thiocyanate (SCN^-), a persistent and hazardous pollutant in industrial effluents, constitutes a significant environmental issue. This study presents the synthesis and deployment of a new nanocomposite of reduced graphene oxide functionalized with metal oxides (rGO-Al₂O₃/MgO/K₂O) for effective SCN^- adsorption. The nanocomposite was synthesized by a hydrothermal process and evaluated using FTIR, XRD, XPS, SEM, TEM, EDX, BET, and TGA studies. FTIR and XPS validated effective functionalization and SCN^- adsorption via nucleophilic interactions and surface changes. XRD indicated structural modifications during adsorption, whereas SEM/TEM demonstrated morphological transformation from exfoliated rGO sheets to compact, irregular rGO-MOs-SCN structures. EDX and elemental mapping confirmed the inclusion of Al, Mg, K, and SCN^- ions. BET analysis revealed a substantial specific surface area of 36.7123 m²/g for rGO-Al₂O₃/MgO/K₂O, promoting improved adsorption. TGA exhibited enhanced thermal stability of the composite, with merely 54.6% weight loss at 600 °C. Batch adsorption tests demonstrated optimum SCN^- removal at pH 2.0 and 25 °C, with a maximum removal of 91.4%. The adsorption effectiveness diminished as temperature increased, signifying exothermic activity. The process adhered to Freundlich and Langmuir isotherms, exhibiting correlation coefficients (R ²) between 0.8901 and 0.9882, respectively. Thiocyanate quantification was accomplished by UV-visible spectrophotometry at 460 nm utilizing Fe³⁺ complexation. This rGO-metal oxide nanocomposite provides an economical, thermally stable, and highly successful solution for thiocyanate remediation in aqueous environments, with significant implications for industrial wastewater treatment and environmental protection.