Cadmium adsorptive removal from water using activated carbon derived from Tradescantia fluminensis: Isotherm, kinetic, and thermodynamic studies

ABSTRACT This study utilized activated carbon derived from Tradescantia flumenesis ( T. fluminensis ) for the removal of Cd 2+ ions from water. The surface morphology, elemental composition, functional groups, and surface charge of the activated carbon were investigated using SEM, EDX, FTIR, and pH pzc . The SEM-EDX analysis revealed a highly porous compound that comprises carbon and oxygen, while the FTIR spectrum revealed peaks at 1587.56, 1085.59, and 3200 to 3350 cm -1 that indicated the presence of C=C aromatic, C–O, and the weak presence of -OH group. The batch study demonstrated the effects of operational parameters on the adsorptive efficiency of the activated carbon by attaining 87.2% Cd 2+ ion removal from water at an optimum pH of 5 in contact time (120 min), dosage (1 g), and temperature (301 K). The isotherm was well fitted using the Freundlich model, indicating a multilayer adsorption of Cd 2+ ion, while the kinetics was best described by the pseudo-second-order model that predicted a maximum adsorption capacity (8.703 mg/g) in a closer range to the experimental outcome (8.8731 mg/g), compared to the pseudo-first order model. Furthermore, thermodynamic parameters such as ΔG (-2.343 to -3.029 KJ/mol), ΔH (2.338 to 10.549 KJ/mol), and ΔS (15.886 to 44.831 J/mol) were obtained in a temperature range of 301 to 338 K. This indicates a spontaneous and endothermic adsorption process for Cd 2+ ion removal governed by a physisorption mechanism.