Kinetic and equilibrium studies of methylene blue removal from aqueous solution by adsorption on treated sawdust

The aim of this study is to use treated sawdust as an adsorbent for the removal of methylene blue (MB) dye. The adsorption equilibrium and kinetics of methylene blue dye on this adsorbent were then examined at 25 ºC. The adsorption isotherm of the methylene blue on the treated adsorbent was determined and correlated with common isotherm equations. The sorption data were then correlated with the Langmuir and the Freundlich adsorption isotherm models. The Langmuir isotherm exhibited a better fit for the adsorption data than the Freundlich isotherm with maximum monolayer adsorption capacity of 236.16 mg g–1. The kinetics of methylene blue adsorption on the treated adsorbent has also been studied by fitting the data in the Lagergren’s first order, the Ho-McKay’s pseudo second order, the Elovich and the Intraparticulate kinetic models. It was observed that the removal of methylene blue over the treated adsorbent undergoes the second order processes at all the concentrations of the dye. The kinetic parameters of this best-fit model were calculated and discussed.