Biosorption of cationic dye from aqueous solutions onto lignocellulosic biomass (Luffa cylindrica): characterization, equilibrium, kinetic and thermodynamic studies

摘要

In the present study, biomass fiber (Luffa cylindrica) has been successfully used as biosorbent for the removal of a cationic dye namely, methylene blue, from aqueous solution using a batch process. The characterization of the biosorbent was carried out by the infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The chemical composition has been established by the energy dispersive X-Ray spectroscopy (EDS). The effects of various parameters such as the contact time (0–160?min), solution pH (2–10), biosorbent dose (0.5–8?g?L?1), particle size, initial MB concentration (20–300?mg?L?1) and temperature (20–60?°C) were optimized. The biosorption isotherms were investigated by the Langmuir, Freundlich, Dubinin–Radushkevich and Tempkin models. The data were well fitted with the Langmuir model, with a maximum biosorption capacity of 49.46?mg?g?1 at 20?°C. The kinetics data were analyzed by the pseudo-first-order and pseudo-second-order models. The mass transfer model in terms of interlayer diffusion was applied to examine the mechanisms of the rate-controlling step (R2?=?0.9992–0.9999). The thermodynamic parameters: free energy (ΔG°?=??5.428 to ?3.364?kJ?mol?1), enthalpy (ΔH°?=??20.547?kJ?mol?1) and entropy (ΔS°?=??0.052?kJ?mol?1?K?1) were determined over the temperatures range (20–60?°C). The results indicate that Luffa cylindrica could be an interesting biomass of alternative material with respect to more costly adsorbents used nowadays for dye removal.