Activated ailanthus altissima sawdust as adsorbent for removal of acid yellow 29 from wastewater: Kinetics approach

In this study, Ailanthus altissima sawdust was chemically activated and characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR), Energy Dispersive X rays (EDX), and surface area analyzer. The sawdust was used as an adsorbent for the removal of azo dye; Acid Yellow 29 (AY 29) from wastewater. Different kinetic and equilibrium models were used to calculate the adsorption parameters. Among the applied models, the more suitable model was Freundlich with maximum adsorption capacities of 9.464, 12.798, and 11.46 mg/g at 20^◦C, 30^◦C, and 40^◦C respectively while R² values close to 1. Moreover, the kinetic data was best fitted in pseudo second order kinetic model with high R² values approaching to 1. Furthermore, adsorption thermodynamics parameters such as free energy, enthalpy, and entropy were calculated and the adsorption process was found to be exothermic with a value of ∆H^◦ = −9.981 KJ mol⁻¹, spontaneous that was concluded from ∆G^◦ values which were negative (−0.275, −3.422, and −6.171 KJ mol⁻¹ at 20, 30, and 40^◦C respectively). A positive entropy change ∆S^◦ with a value of 0.0363 KJ mol⁻¹ indicated the increase disorder during adsorption process. It was concluded that the activated sawdust could be used as a suitable adsorbent for the removal of waste material, especially dyes from polluted waters.