Isotherm and kinetic modeling of the adsorption of methylene blue, a cationic dye, on pumice

The removal of dyes from aqueous solution with cheap and abundant adsorbents is becoming increasingly important for the solution of a serious environmental problem such as wastewater treatment. In this study, isotherm and kinetic modeling of the adsorption of methylene blue on pumice, a porous and glassy volcanic rock resistant to physical and chemical factors, was aimed. For this, the compatibility of the experimental data with the isotherm and kinetic models was examined, and information about the efficiency, effectiveness and rate of adsorption was tried to be obtained. Experimental data have been applied to isotherm models such as Langmuir, Freundlich, Temkin, Brenuer-Emmet-Teller (BET), Dubinin- Radushkevich, and Harkins-Jura, and kinetic models such as pseudo-first order, pseudo-second order, and intraparticle diffusion. While the order of fit for the isotherm models was determined as Freundlich > Harkins-Jura > Dubinin- Radushkevich based on the results of the regression analysis, the highest fit was obtained with the Freundlich equation (R2:0.993). Thus, the adsorption intensity (n) of methylene blue on pumice was calculated as 1.14 and the adsorption capacity (k) of pumice was calculated as 6.43. On the other hand, the order of fit of the experimental data to the kinetic models was determined as pseudo-second order > pseudo-first order > intra particle diffusion according to the regression coefficients. However, the highest consistency among the kinetic models was obtained with the pseudo-second order kinetic model(R2:1.000).