Adsorptive potentials of lemongrass leaf for methylene blue dye removal

Abstract

Abstract Lemongrass leaf activated carbon (LLAC) was prepared using physicochemical process for MB dye removal from aqueous systems. The adsorbent was characterized by SEM and FTIR techniques respectively. Batch adsorption studies were investigated using four operational parameters: initial dye concentration (25 mg/L-500 mg/L), contact time (0 hr to 24 hr), temperatures (30 °C - 60 °C) and pH (2–12). The surface chemistry analysis shows that upon the interaction of MB dye with the adsorbent, the bands are significantly altered after MB dye adsorption e.g., band at 2125 cm−1, 1650.09–1514 cm−1, 1386.98–1 273.05 cm−1, 1088.60 cm−1, etc. disappeared upon the interaction of the LLAC with the MB dye. Whereas, the surface morphology shows that the activation process with NaOH has contributed to the widening and formation of pores on the LLAC surface which is required for efficient MB dye uptake. MB dye adsorption is strongly dependent on initial dye concentrations while the percentage MB dye removal by LLAC increases with increasing solution pH until it reached the optimum at pH 12 with maximum percentage removal of 64.36%. The equilibrium data were fitted into eight different isotherms. Koble-Corrigan model best fitted the adsorption data with a maximum sorption capacity of 342.9 mg/g and R2 = 0.999. The pseudo-first-order kinetic model best explained MB dye adsorption onto LLAC. Thermodynamic parameters (such as ∆G0, ∆H0, and ∆S0) were also determined. The sorption process for MB dye removal was endothermic while the reaction mechanism follows the physisorption process.