Elimination of Cd2+ from synthetic and real polluted water by optimized Acacia nilotica biographene

Abstract Biographene was prepared through the pyrolysis of Acacia nilotica waste using diverse temperatures and time spans. The obtained materials were characterized using scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), X-ray diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FTIR) methods. The data obtained indicated that when the temperature and time increased, the texture of the biographene became more porous with greater carbon content. The effect of various variables on Cd(II) adsorption, using the optimized biographene product, was investigated, and the results revealed that the optimum pH was 4 and the maximum adsorption capacity was 118.9 mg/g. The Langmuir isotherm model and pseudo-second-order kinetic model best fit the equilibrium data, indicating the adsorptive behavior of the as-prepared biographene implying a homogenous monolayer surface. The recyclability investigation elucidates the remarkable potentiality of up to five consecutive cycles. As such, the biographene-based Acacia nilotica could be considered a sustainable candidate for cadmium removal from polluted water.