Microwave- and acid-treated bentonite as adsorbents of methylene blue from a simulated dye wastewater

Batch adsorption tests for removal of methylene blue dye (MBD) from aqueous solutions onto bentonite was investigated using natural chemically treated (sulphuric acid) and physically treated (microwaved) bentonite. In batch sorption tests for MBD removal by the developed sorbents, the time needed to reach equilibrium was less than 30 min. The uptake of MBD by the microwave-treated bentonite was the highest, followed by the acid-treated and finally the untreated bentonite. The uptake of MBD increased with an increase in the dye concentration or the solution temperature. Three kinetic models were used for elucidation of the probable mechanisms of MBD uptake by the three sorbents. The rates of MBD uptake followed the pseudo second-order model with a high correlation. Intraparticle diffusion was involved in the sorption process but was not the rate-controlling factor. The Freundlich and Langmuir isotherm models were employed and well represented the experimental data.