Luffa acutangula peel as an effective natural biosorbent for malachite green removal in aqueous media: equilibrium, kinetic and thermodynamic investigations

Luffa acutangula peel (LAP) was evaluated as an inexpensive natural biosorbent for the removal of malachite green (MG), a cationic dye, in batch mode. The effects of process parameters including initial pH, dosage, initial concentration, temperature and contact time on MG biosorption were assessed. Experimental data were analysed by the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. The results showed that MG biosorption was well represented by the Langmuir model with a maximum sorption capacity of 69.64 mg/g. The pseudo-first-order and pseudo-second-order kinetic models were used to establish the biosorption kinetic. A good correlation of data with the pseudo-second-order model suggested the involvement of chemisorption in the process. Further kinetic analysis indicated intraparticle diffusion as one of the rate limiting steps. The biosorption process was endothermic (Delta H degrees = 0.332-12.64 kJ/mol) and spontaneous (Delta G degrees = -20.81 to -14.28 kJ/mol). Overall, the findings suggested that LAP can be an effective biosorbent for the removal of MG in aqueous solution.