Adsorption of BR46 dye using raw and purified clay

The adsorption behaviour of Basic Red 46 (BR46) from aqueous solution onto raw (RA) and Purified (PA) natural adsorbent samples was investigated as a function of parameters such as initial dye concentration, contact time and temperature. The Langmuir, Freundlich and Dubinin– Radushkevich (D–R) adsorption models were applied to describe the equilibrium isotherms. The Langmuir monolayer adsorption capacities of RA and PA were estimated at 54 mg/g and 72 mg/g, respectively. The mean adsorption energy derived from D–R isotherm for the PA and the RA showed that the type of adsorption of dye molecules on these materials may be defined as physical adsorption for the PA and ion-exchange processes for the RA. The adsorption rate was fast and the equilibrium was achieved within 20 min at the room temperature. The pseudo-first-order and pseudo-second-order kinetic were used to describe the kinetic data and rate constants were evaluated. The trend of the correlation coefficients values (r²) were pseudo-second-order > pseudo-first-order. Thermodynamic parameters were also evaluated and revealed that the adsorption process is exothermic in nature. The quite high adsorption capacity of PA will provide an important advantage for using of this material in basic dye solution.