Removal of Methylene Blue from aqueous solutions by adsorption on Kaolin: Kinetic and equilibrium studies

Removal of Methylene Blue (MB) from aqueous solutions is studied using a raw Algerian kaolin sample as a low-cost adsorbent. The effects of pH, contact time, dye concentration and temperature are all taken into consideration. The adsorption kinetics results are adjusted to best fit the pseudo-second order model. The experimental data are analyzed by Langmuir isotherms, revealing that the maximum adsorption capacity of MB on this kaolin sample equals 52.76 mg/g at T = 25 °C and pH = 6.0. The calculated thermodynamic data demonstrates that adsorption is spontaneous and enhanced at higher temperatures. Desorption studies with water indicate that the adsorbent could successfully retain MB, even after four cycles. From these results, it can be considered that the raw Algerian kaolin sample tested herein is effective in the removal of MB from aqueous solutions and moreover may be used as an alternative to high-cost commercial adsorbents.