Highly efficient Cd(II) removal from groundwater utilizing layered mixed metal oxides-graphitic carbon nitride composite with improved cycling stability

Graphitic carbon nitride (GCN) and its mixed metal oxide (MMO) composites are synthesized via co-precipitation followed by the pyrolysis method using various ratios of calcium aluminium (Ca:Al) with GCN, to enhance the adsorption ability towards Cd(ii) present in wastewater. Synthesized composite materials were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface analysis, Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. Due to its higher specific surface area (218.65 m²/g), the produced GCN and CaAl mixed metal oxide composite (GCN-MMO) exhibits improved adsorption ability towards Cd(II) ions. Approximately >99 % were adsorbed with Langmuir q_max of 131.57 mg/g. An overall pseudo-second-order (PSO) model fitted the kinetics data well. The possible mechanisms were surface complexation and precipitation, outer-sphere complexation, and acid-base mechanism. Further, the groundwater application was studied, and it achieved adsorption below the maximum permissible limit of USEPA with excellent cycling stability. The findings of this study showed that GCN-MMO composite material may be useful for the adsorption of Cd(II) heavy metal from an aqueous solution.