Biosorption potential of Sapindus mukorossi dead leaves as a novel biosorbent for the treatment of reactive red 241 in aqueous solution

Abstract

The research work focuses on the assessment of biosorption potential of Sapindus mukorossi dead leaves (SMDL) as a novel, cheaper, and abundantly available biosorbent for the treatment of C.I. Reactive red 241 (RR-241) in aqueous solution. The biosorbent characterization was performed by using scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray, and Brunauer–Emmett–Teller surface area analysis techniques. The dye biosorption was studied as a function of various operating parameters including initial pH, adsorbent dose, dye concentration, adsorption time, and temperature. Moreover, kinetic modeling was conducted by implying pseudo-first-order kinetic model, pseudo-second-order kinetic model, Elovich, and intraparticle diffusion models. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models were applied for adsorption isotherm modeling. Finally, the thermodynamic parameters like the difference in free energy (∆G°) was evaluated by Gibb’s equation while the difference in enthalpy (∆H°) and entropy (∆S°) was evaluated by Van’t Hoff equation. The results show that more than 95% dye removal efficiency was achieved on SMDL with an equilibrium capacity of 8.18 mg/g. The results further exposed that the biosorption of RR-241 on SMDL pursued pseudo-second-order kinetics (R 2 = 0.99). The adsorption isotherms gave the best fit with the Freundlich model (R 2 = 0.99). The negative free energy change (∆H°) values confirmed spontaneous and feasible adsorption. The positive values of enthalpy change (∆H° = 14.39 kJ/mol) indicated the endothermic adsorption nature and entropy change (∆S° = 0.055 kJ/mol/K) indicated the increased randomness at the solid–liquid interface. It is concluded that the SMDL has a good biosorption potential as low-cost biosorbent for the abatement of RR-241 in aqueous solutions.