Biosorption of methylene blue from aqueous solution by softstem bulrush (Scirpus tabernaemontani Gmel.)

BACKGROUND: The removal of methylene blue from aqueous solution was studied using softstem bulrush (Scirpus tabernaemontani Gmel.) as the biosorbent. The effects of various parameters including contact time, biosorbent dosage, ionic strength and solution pH on the biosorption were investigated. RESULTS: The sorption capacity increased with an increase in biosorbent dosage and a decrease in ionic strength. The equilibrium time was found to be 240min for full equilibration. Pseudo-first-order, pseudo-second-order, Bangham equation and intraparticle diffusion models were applied to fit the kinetic data, and the results showed that the sorption process followed the pseudo-second-order model. Equilibrium data conformed to Langmuir and Redlich-Peterson isotherm models, with a maximum monolayer biosorption capacity of 53.8mg g(-1) for the Langmuir isotherm at 18 degrees C. The value of Delta G was estimated to be -29.24 kJ mol(-1) indicating the spontaneous nature of the biosorption. The biosorption process was strongly pH-dependent and favourable at alkaline pH. CONCLUSION: Softstem bulrush, which is readily available and inexpensive, could be employed as a promising biosorbent for the removal of dye. (C) 2008 Society of Chemical Industry