Biosorption of crystal violet onto cyperus rotundus in batch system: kinetic and equilibrium modeling

Abstract

In this study, biosorption potential of Cyperus rotundus (CR) was investigated for decolorization of crystal violet (CV), a cationic dye, from its aqueous solution employing batch experimental set-up. Experiments were carried out as a function of contact time, biosorbent dosage (0.1–2.0 g), initial solution pH (2–12), temperature (20–40°C), initial dye concentration (10–30 mg/l), and agitation speed (50–200 rpm). The biosorbent (before and after dye biosorption) was characterized by Fourier transform infra red spectroscopy and scanning electron microscopy. The Langmuir, Freundlich, and Temkin adsorption isotherm models were used for the mathematical description of biosorption equilibrium. The biosorption process followed the Freundlich isotherm model with high correlation coefficient at different temperatures. The pseudo-second-order kinetic model fitted well in correlation to the experimental results. The mass transfer model based on intraparticle diffusion was applied to the experimental data to examine the mechanisms of the rate controlling step. It was found that intraparticle diffusion was not the sole rate controlling step. Thermodynamic parameters, such as ΔG, ΔH, and ΔS were also calculated for the biosorption process and found that the biosorption process is spontaneous and exothermic in nature. It can be concluded that CR is a promising biosorbent for the removal of CV from aqueous solution.