Sorption studies of methyl red dye removal using lemon grass (Cymbopogon citratus)

Abstract

Lemongrass leaf based activated carbon (LGLAC) was prepared using physico-chemical methods for methyl red (MR) dye removal from aqueous solutions. The surface chemistry of LGLAC before adsorption revealed the presence of different functional groups: O-H, C-H, C=O, CH 3 , C=C, N-O, C-O and C-N which were shifted after methyl red dye adsorption. Brunauer-Emmett-Teller surface and mesopore areas are 836.04 m 2 /g and 598.6 04 m 2 /g, whereas, the average pore diameter and total pore volume of LGLAC are 3.62 nm and 0.472 cm 3 /g respectively. Batch adsorption was studied using different parameters: initial dye concentrations (25–500 mg/L), contact time (0–24 h), solution temperature (30–60 °C) and solution pH (2–12). Adsorption of methyl red dye was observed to increase with increase in initial dye concentration, contact time and solution temperature. The methyl red dye adsorption uptake and percentage removal at equilibrium showed that the adsorption process is majorly dependent on the initial dye concentration. Optimum percentage of methyl red dye removed was observed at pH 2. The adsorption process of methyl red dye onto LGLAC was endothermic in nature. Thermodynamic parameters, including entropy change ( Δ S 0 ), enthalpy change ( Δ H 0 ), and Gibbs free energy change ( Δ G 0 ) were evaluated. The adsorption process was endothermic and the mechanism followed a physisorption process.