Biosorption of toxic congo red dye from aqueous solution by eco-friendly biosorbentSaccharum bengalense: kinetics and thermodynamics

Abstract

Abstract In the present study, Saccharum bengalense (SB), a potential biosorbent, was investigated for the removal of toxic Congo red (CR) dye. The effect of various operating variables, viz. adsorbent dosage, pH, contact time, and temperature on the removal of dye has been studied. Almost 94% removal of dye is possible after 50 min at pH 2.0 under batch test conditions. It was found that a pseudo-second-order mechanism was predominant and the overall rate of the dye adsorption process appears to be controlled by more than one step. The intra-particle diffusion model was applied to investigate the rate determining step. Langmuir, Freundlich, and Dubinin–Radushkevich adsorption isotherm models were applied to describe the biosorption isotherm. The biosorption data were better represented by the Langmuir model and the biosorption capacity (q max) of SB for CR was achieved at 125 mg/g. Thermodynamic parameters such as standard free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy cha...