Tobacco Stalk Waste Biomass Holds Multilayer and Spontaneous Adsorption Capabilities for Reactive Black 5 Dye: Equilibrium Modelling and Error Function Analysis

Abstract

Tobacco stalk biomass (TSB) is explored for reactive black 5 (RB5) dye treatment in batch reactor. TSB displayed RB5 adsorption efficiency of 93.5% at 120 min. The RB5 data were fitted to linear and non-linear isotherms and kinetic models. Error functions were determined to have a holistic view on optimum parameters and to validate prediction of models. Harkin-Jura exhibited better fit than that of Freundlich and Langmuir isotherms suggesting multilayer adsorption of RB5 onto TSB on the basis of R 2 and chi-square (χ 2 ) error values. Adsorption kinetics was best explained by intraparticle diffusion model (IPD) at increasing initial concentration of RB5. Among the error functions evaluated, the χ 2 values for the IPD model were found to be smaller than those for PSO. This suggests that kinetics of RB5 dye is better controlled by IPD phenomenon. Fourier transform infrared spectroscopy confirms the physical adherence of dye to the adsorbent. Values of Gibbs free energy were found to be -19.55 -21.41, -23.40 and -25.33 kJ/mol which shows spontaneous adsorption. Moreover, it is found that TSB adsorbent could be utilized as the effective and economically viable adsorbent for RB5 dye from aqueous solution.