Removal of Fluoride from Aqueous Solution by Using Low-Cost Sugarcane Bagasse: Kinetic Study and Equilibrium Isotherm Analyses

Abstract

In the present study, sugarcane bagasse (Saccharum officinarum) was utilized to assess its capacity for the adsorption of fluoride from aqueous solutions. The batch adsorption experiments were carried out to calculate the adsorption capacity of sugarcane bagasse for the adsorption of fluoride from aqueous solution. The effects of various parameters like initial pH (pH0), adsorbent dose (m), contact time (t), initial concentration (C0), and temperature (T) on the adsorption of fluoride from the aqueous solution were studied. The adsorption rate is found to be very fast. For C0=4 mg/L, about 45% fluoride removal was found in t=60 min contact time at m=1 g/L adsorbent dose. The sorption kinetics could be well represented by a pseudosecond-order kinetic model. The minimum uptake of fluoride was found to be 1.20 mg/g, maximum uptake was observed to be 1.82 mg/g at lower concentration (4 mg/L). At higher concentration (8 mg/L), the minimum uptake of fluoride was found to be 2.50 mg/g and maximum uptake of fluoride was found to be 4.12 mg/g. Pseudo first-order, pseudo second-order, Elovich and modified Freundlich equations were used to describe the adsorption rate of fluoride. Adsorption isotherms have been studied by Langmuir, Freundlich, Temkin, Redlich-Peterson, and Toth, and Radke-Prausnitz equations and their constants were determined. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated in order to understand the nature of sorption. A thermodynamic study revealed that the adsorption of fluoride onto bagasse is an endothermic process.