Removal of Cd(II) from aqueous solution using biosorbent based on agricultural waste sorgum bagasse (Sorghum bicolor (L.) Moench) activated NaOH

Cadmium (Cd(II)) contamination is very harmful to the aquatic environment. Currently, the removal of Cd(II) from water is widely studied to reduce its toxicity. In this study, agricultural waste sorghum bagasse (SB) was activated with NaOH and used to adsorb Cd(II) in aqueous solution. NaOH-activated sorghum bagasse (SB-NaOH) was characterised using Fourier transform infrared spectroscopy (FTIR) to investigate the functional groups, scanning electron microscopy (SEM-EDX) to observe surface morphology, X-ray diffraction (XRD) to analyzed the structure and chemical composition, and Brunauer–Emmett–Teller (BET) method to evaluate pore size. The batch system was used to investigate the adsorption parameters such as adsorbent mass, contact time, initial concentration, pH, and temperature. The optimum conditions of Cd(II) adsorption were at pH 5, 70 min, 600, 100 mg/L, and 30°C. The maximum adsorption percentage was 96.48%. The pseudo-second-order is suitable for kinetic models of Cd(II) adsorption and the isotherm model was Langmuir model. The Gibbs free energy obtained a positive value and the enthalpy had a negative value, indicating that the adsorption of Cd(II) is an exothermic process. Therefore, SB-NaOH adsorbent can be used as a potential adsorbent with easy and economical treatment to reduce Cd(II) in the aquatic environment.