Removal of cationic dyes by kaolinite

The removal of cationic dyes such as maxilon yellow 4GL (MY 4GL) and maxilon red GRL (MR GRL) on kaolinite from aqueous solutions has been studied according to the adsorption method. The adsorbed amount of dyes on kaolinite surface was investigated as a function of pH, ionic strength, temperature, acid activation, and calcination temperature. It was found that: (i) the adsorbed amount of cationic dyes increased with increase in pH and decreased with increase in temperature, ionic strength, acid activation, and calcination temperature; (ii) the adsorption process was an exothermic process; (iii) the experimental data were correlated reasonably well by the adsorption isotherm of the Langmuir; and (iv) the interactions between adsorbate and adsorbent from adsorption heat data were physical in nature.