APPLICATION OF ACTIVATED BENTONITE FOR THE REMOVAL OF DIRECT AND REACTIVE DYE FROM AQUEOUS SOLUTIONS

The aim of this study was to determine adsorptive properties of acid-activated bentonite clay for the removal of Direct Red 173 (DR 173) and Reactive Red 22 (RR 22) dyes from aqueous solutions. Raw and modified clay were characterized by the following methods: Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM). The efficiency of activated clay adsorption was investigated depending on process parameters: the adsorbent dose, pH, temperature, initial dye concentration, and contact time. Experimental data were analyzed by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms as well as kinetic models of pseudo-first order, pseudo-second order and intra-particle diffusion. The process of dye adsorption was best described by Langmuir, Temkin, and Dubinin-Radushkevich isotherms (R-2 > 0.97). Pseudo-second order model (R-2 > 0.99) had the highest correlation with the obtained kinetic results. The positive value of Delta H degrees indicated that adsorption of dyes by activated bentonite day is an endothermic . process. The activated bentonite exhibited good regenerative ability in the 0.1 M NaOH solution. Maximum adsorption capacities of acid-activated bentonite clay at 25 degrees C for DR 173 and RR 22 dyes were 356.65 and 109.58 mu mol g(-1), respectively.