Activated Carbon/Polyaniline Composite for Azo Dye Adsorption: Kinetics, Equilibrium, Thermodynamics, and Statistical Physics Interpretations

Abstract

Activated carbon (Ac) prepared from Thapsia transtagana was combined with a different ratio of aniline to synthesize Ac/PAni composites. Various characterization techniques, such as XRD, FESEM-EDX, TEM, and ATR-FTIR, were conducted to confirm the structure, surface morphology, and chemical characteristics of the composites. The materials were tested for eriochrome black T (EBT) adsorption. Batch results exposed that the Ac/PAni6 with the highest ratio of aniline displays the highest EBT removal efficiency. The kinetics of EBT adsorption over the Ac/PAni6 composite followed the Elovich model, and the equilibrium data suited the Redlich–Peterson and Toth isotherm models. The adsorption was spontaneous, feasible, and endothermic. The statistical physics equations have also been investigated. Four models have been proposed as one layer and two layers with one and two energies. The adsorption of EBT on the Ac/PAni6 composite correlated to the one layer two energies model. The statistical physical parameters, including the number of adsorbed molecules per site (\({n}_{1}\), \({n}_{2}\)), the receptor sites density (\({N}_{1M}\), \({N}_{2M}\)), the adsorption capacity at saturation (\({Q}_{1}\), \({Q}_{2}\)), and the energy of adsorption (\({E}_{1}\), \({E}_{2}\)) have all been considered. The total capacity at saturation is enhanced with temperature, which approves the endothermic nature of the process. The interpretation of the calculated energies \({E}_{1}\) and \({E}_{2}\) (< 40 kJ/mol) suggested that the EBT interaction with the Ac/PAni6 surface was mainly a physisorption process.