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Introduction: Azo groups of dyes used widely for coloring yarn. Methylene blue is one of this group's dyes therefore with benzene rings in its structure caused the toxicity and its persistence in the environment. So that the its deficiency of proper treatment can cause the irreparable damage to the environment. One of the ways to removal these dyes from natural sources are absorbed by the absorbent. So the aim of this study is Kinetic and isotherm study of methylene blue adsorption by powdered pumice from the aquatic environment.

Methods: Adsorption process was investigated in vitro at neutral pH, a constant concentration of dye and adsorbent dosage. The residual concentration of the dye solution through adsorption was measured at a wavelength nm 665 by using a spectrophotometer (Cary 50 manufacturers of Perkin Elmer). In order to understand how to adsorption, obtained data were fitted with Langmuir, Freundlich, Temkin, Harikens-jura and Dubinin-Radushkevich isotherms and Pseudo –first –order, Pesedo – second – order, Intraparticle diffusion and Elovich Kinetics.

Results: Results showed that in the between of five isotherm models, the adsorption process is most obeyed of Harikens-jura isotherm (R²=0.9914). Also the adsorption process has appropriate obeyed of both Langmuir and Freundlich isotherms (R²=0.9633 and R²=0.9365) and it is means that the adsorption process occurs in a mono- layer and multi-layer. The low of mean free energy (E= 0.323 KJ/mol) in Dubinin-Radushkevich showed that the physical absorption process is dominant adsorption. Also adsorption process is obeyed of pseudo – second – order model.

Conclusion: According to the results, can say Methylene blue adsorption multi -layer is most occurs than mono- layer and the pumice is the effectiveness adsorbent for removal methylene blue dye (RL=0.2).