Activated kaolin’s potential adsorbents for the removal of Derma Blue R67 acid dye: kinetic and thermodynamic studies

In the present work, two Algerian clay samples, Djebel Debagh (DD3) and Tamazert (KT2), were used as adsorbents for the removal from the water of Derma Blue R67, which is an acid dye commonly used in the tanning industry. The two clay samples used were first treated by acid in order to enhance their retention capacities, and then characterized using X-ray diffraction, scanning electron microscopy, surface area measurements (Brunauer, Emmett et Teller method (BET)), surface charge (points of zero net proton charge), and electrophoretic mobility (Zetaphoremeter). Further, the adsorption experiments of the acid dye from water onto the clay surface were carried out by investigating various parameters such as, the contact time, the initial dye concentration, the aqueous phase pH, the clay amount and the temperature. The results indicate that the two adsorbents are efficient and that the anionic dye removal from water is mainly feasible at ambient temperature. Further, the comparison of the experimental adsorption data to the prediction models has shown that the Langmuir model gives the best fit, indicating the formation of a monolayer by the acid dye molecules on the clay surface. Finally, the adsorption kinetics follows a two-type process onto KT2 kaolinite, whereas onto DD3, it only follows the pseudo-second order model. From the overall data, it is concluded that the Algerian local kaolin clays are good adsorbent candidates for wastewater treatments.