Steam-activated carbon prepared from Chrysophyllum albidum seed shell for the adsorption of cadmium in wastewater: kinetics, equilibrium and thermodynamic studies

Steam-Activated Carbon (SAC) prepared from shell of the seed of Chrysophyllum albidum was used to adsorb cadmium (Cd) ion from aqueous solution. The sorption process with respect to its equilibria, kinetics and thermodynamics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration and particle size on adsorption was also studied. The kinetic data and the adsorption process followed first-order rate kinetics; equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 150.33 mg Cd g–1 at initial pH of 5.0 at 30°C for the particle size of 1.25 mm with the use of 2.0 g/100 mL adsorbent mass. Fourier Transform Infra-Red (FTIR) spectrometry reveals the presence of hydroxyl, carbonyl, amide and phosphate groups that confi rm the potential mechanisms of adsorption of the adsorbent. Alkali regeneration of the adsorbent recovered the adsorbed metal ions and restored the adsorbent to its original state.