Selective removal of Cd2+ from aqueous solution using a novel Ranitidine functionalized three-dimensional graphene oxide (3D RN-GO) composite: Kinetics, isotherms, thermodynamics, and regeneration studies

A novel 3D RN-GO 1:3/160°C/8h composite with hetero-atomic functional groups (–O, –S, –N) was successfully fabricated using Ranitidine (RN) to functionalize GO by a facile hydrothermal assembly, which demonstrated excellent selectivity in removing Cd 2+ from aqueous solutions. The composite’s morphology, functional groups, elemental composition, and thermal stability were comprehensively characterized using SEM, EDS, FT-IR, XPS, and TGA techniques. Adsorption experiments revealed that pH, contact time, initial Cd 2+ concentration, and temperature significantly influenced the removal efficiency, and optimal conditions were identified for maximum Cd 2+ uptake. Kinetic studies indicated a complex adsorption mechanism best described by the pseudo-second-order model. Thermodynamic analysis confirmed the spontaneous and endothermic nature of the adsorption process. Furthermore, the adsorption isothermal data suggested the adsorption was monolayer over a homogeneous surface of the composite. To evaluate regeneration performance, 50.0 mg of the 3D RN-GO 1:3/160°C/8h composite was exposed to 20.0 mL of Cd 2+ aqueous solution. After five consecutive adsorption–desorption cycles, the composite maintained >95 % adsorption and desorption efficiency for Cd 2+ . The abundant hetero-atomic functional groups (–O, –S, –N) on 3D RN-GO 1:3/160°C/8h composite facilitated Cd 2+ ion adsorption through surface complexation. This study highlights the potential of the developed 3D RN-GO 1:3/160°C/8h composite as a promising adsorbent for water pollution remediation.