Adsorption of acid dyes from aqueous solution by CTMAB modified bentonite: Kinetic and isotherm modeling

Adsorption of four acid dyes onto cetyltrimethyl ammonium bromide (CTMAB) modified organobentonite from aqueous solution was studied, and effects of the parameters like adsorbent dosage, solution pH, contact time and dye concentration were investigated. The adsorption onto CTMAB-Bent attained equilibrium quickly within 10 min for Acid Blue 93 (AB93), Acid Turquoise Blue A (ATBA), Acid Golden Yellow G (AGYG) and 50 min for Acid Blue 25 (AB25). The adsorption capacity decreased slightly along with the increasing solution pH of 7.0. Four adsorption kinetics equations (pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich) were employed to evaluate experimental kinetics data. The rates of the acid dyes adsorption conformed to the pseudo-second-order equation well. The adsorption equilibrium data were analyzed with six models. Both linear and nonlinear regression methods were implemented to calculate isotherm parameters, and the nonlinear regression was more favorable. Regarding to the results of nonlinear analysis, the most applicable adsorption isotherm models were found to be Freundlich, Langmuir, Radlce-Prausnitz, Fritz-Schlunder, and Sips equations. The removal ratios of the acid dyes by CTMAB-Bent were all above 88% at the experimental conditions, suggesting that CTMAB-Bent was an excellent adsorbent for acid dyes removal from aqueous solution. (C) 2015 Elsevier B.V. All rights reserved.