Investigation of adsorption characteristics of methyl violet 6B on kaolin

In this study, adsorption and adsorption kinetics of methyl violet dye from aqueous solutions onto kaolinite has been investigated. The effects of adsorbent dosage, pH, ionic strength, contact time, temperature and initial dye concentration have been studied. Kinetic and thermodynamic parameters were determined using experimental data. Adsorption capacity decreased with increasing ionic strength. Changes in initial pH of the dye solution in a range close to the dye?s natural pH values affected adsorption capacity slightly, indicating that adsorption studies could be carried out at dye?s natural pH. Adsorption process followed the Langmuir type adsorption isotherms and pseudo-second order type adsorption kinetics. However, intraparticle diffusion process was found to have effects in adsorption processes. Thermodynamic parameters were calculated from the experimental data and enthalphy of the adsorption was found to be ? 6,78 kJ/mol, indicating physisorption nature of the adsorption. Other thermodynamic parameters, entropy and Gibbs free energy were also calculated. Negative values of Gibbs free energy indicated that adsorption process for methyl violet on kaolinite is spontaneous.