adsorption of methylene blue dye from aqueous solutions by modified pumice stone: kinetics and equilibrium studies

background dyes are one of the most important industrial pollutants, especially in textile industries. many methods have been proposed in order to remove color from wastewater among which, adsorption is more acceptable due to the ability for its use in the large scale. objectives the objective of this study was to investigate pumice as an inexpensive adsorbent for removal of methylene blue from aqueous solutions. materials and methods in this work the modified pumice stone has been applied for removal of the methylene blue dye from aqueous environments. the effect of ph, contact time, initial concentration and amount of adsorbent were considered. in order to investigate the mechanism of the adsorption process, several kinetic models including pseudo-first order, pseudo-second order and intra-particle diffusion were used. in addition, equilibrium data was fitted on to langmuir, freundlich, temkin and dubinin-radushkevich models. results results showed that the adsorption of the methylene blue was enhanced with increasing initial dye concentration, ph and contact time. the optimum ph was 10. the qmax for adsorption of methylene blue dye from the langmuir model was 15.87 mg/g. considering the values of r2 (0.999) and χ2, freundlich isotherm model and pseudo-second order kinetic model had the best fitness. conclusions this study has demonstrated that the modified pumice stone with hcl can be employed as effective and inexpensive adsorbent for the removal of methylene blue from aqueous environments.