Adsorption of Direct Red 2 on bentonite modified by cetyltrimethylammonium bromide

Abstract

One kind of adsorbents with high adsorption capacity of direct dye was prepared by exchanging the organic cations as quaternary ammonium for sodium (Na+) on the layer surface of clay. In this study, the adsorption of Benzopurpurin 4B (Direct Red 2) by cetyltrimethylammonium bromide–bentonite (CTAB–bentonite) has been examined in order to measure the ability of this mineral to remove colored textile dyes from wastewater. XRD data showed that the interlayer spacing (d0 0 1) of bentonite was increased from 12 to 19 Å. The surface modification of CTAB–bentonite was examined using the FTIR technique. The batch sorption model, based on the assumption of a pseudo-second order mechanism, has been developed to predict the rate constant of sorption and the equilibrium capacity with the effect of initial dye concentration, and temperature. The equilibrium time was reached within 40 min. The rates of sorption were found to conform to pseudo-second order kinetics with good correlation with regard to intra-particle diffusion rate. The adsorption capacity increased largely with increasing initial dye concentration and temperature. The related apparent activation energy was also evaluated and discussed. The adsorption capacity has been increased from 109.89 to 153.84 mg/g with increasing temperature from 20 to 60 °C.