Adsorption–Desorption of Methylene Blue by Bentonite from Aqueous Solution

This work has two very important axes that are directly involved in the preservation of our environment: First, the treatment of surface water contaminated by toxic pollutants such as dyes using abundant and low-cost mineral materials; and second, the fate of these materials that can be regenerated and reused afterward by removing the pollutant. In this study, we reported the adsorption of Methylene Blue (MB) by bentonite from aqueous solution and its desorption under different operating conditions. The regeneration of the bentonite was carried out as a function of pH, initial dye concentrations, contact time, and temperature. Bentonite is a local clay that contains montmorillonite mineral provided from M’Zila deposit (Mostaganem) in the west of Algeria. Different characterization methods were used such as chemical composition, X-ray diffraction, and specific surface area. The removal efficiency of dye by the bentonite reached 90%. The results showed that the maximum adsorption of bentonite was obtained at pH 8. The maximum adsorption capacity was estimated to be 81.84 mg/g at room temperature. The kinetics study results of methylene blue removal with our solid fit a pseudo-second-order model. The adsorption isotherm data follow the Freundlich equation compared to the Langmuir model tested. The desorption of MB is affected by the pH effect of the medium even at low concentrations, whereas the temperature influences the choice when it exceeds 30 °C.