Effective Biosorption of Auramin O Dye with Sustainable Chickpea Pods Waste; Isotherms, Kinetics and Thermodynamic Analysis

This study investigated biosorbent properties in removing Auramin O (AO) dye from the aqueous solution of agricultural wastes released from chickpea (Cicer arietinum L.), which is widely produced in Turkey and the world. Biosorption studies were carried out using different values of parameters such as initial AO concentration, dye pH, contact time, temperature, and biosorbent amount. Characterization analyses of the biosorbent used before and after biosorption were carried out by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), and point of zero charge (PZC). Biosorption isotherms were evaluated using Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. As a result of experimental data, it has been shown that the Langmuir isotherm model (R2 = 0.930) is the most compatible model for biosorption, while the biosorption kinetic mechanism proceeds through the pseudo-second-order (PSO) kinetic model (R2 = 0.965) and the intra-particle diffusion model. As a result of thermodynamic studies, it has been reported that biosorption is endothermic (?H0>0), spontaneous (?S0>0), and entropy-increasing (?G0 <0).