Adsorption of acid orange 33 dye by bentonite and surfactant modified bentonite

Abstract

The batch adsorption of acid orange 33 from water onto Na-bentonite and CTAB-modified bentonite (CTAB-Ben) was studied. The effects of varying factors, such as initial dye concentration, adsorbent dosage, pH, contact time and temperature, which influence the adsorption capacities of Na-bentonite and CTAB-modified bentonite were investigated and discussed. The results revealed that the adsorption capacities of CTAB-modified bentonite toward acid orange 33 were higher than those of Na-bentonite. The maximum adsorption efficiency of CTAB-modified bentonite was 50 mg/g when acid orange 33 concentration, adsorbent dosage, reaction time and equilibrium pH were 50 mg/L, 80 mg, 90 min and 2, respectively. The isotherm study results for CTAB-Ben satisfactorily fit the Langmuir (R2 > 0.959) and Freundlich (R2 > 0.957) models. The calculated values of the thermodynamic parameters ∆G, ∆H and ∆S showed that the adsorption was a spontaneous and endothermic reaction.