Adsorption of Acid Blue 193 from aqueous solutions onto Na–bentonite and DTMA–bentonite

Dodecyltrimethylammonium bromide-modified bentonite (DTMA–bentonite) was prepared and tested as an adsorbent for an acid dye (Acid Blue 193, AB193) removal from aqueous solution in comparison with Na–bentonite. The effect of various experimental parameters was investigated using a batch adsorption technique. In this manner, the adsorption isotherms, adsorption kinetics, and temperature and pH effects upon Acid Blue 193 adsorption on Na–bentonite and DTMA–bentonite were thoroughly examined. Results show that a pH value of 1.5 is favorable for the adsorption of Acid Blue 193. The isothermal data could be well described by the Freundlich equation. The dynamical data fit well with the pseudo-second-order kinetic model. The adsorption capacity of DTMA–bentonite (740.5 mg g −1) was found to be around 11 times higher than that of Na–bentonite (67.1 mg g −1) at 20 °C. Thermodynamic parameters such as activation energy ( E a ) and change in the free energy ( Δ G 0 ), the enthalpy ( Δ H 0 ), and the entropy ( Δ S 0 ) were also evaluated. The overall adsorption process was exothermic but it is only spontaneous at 20 °C. The results indicate that Na–bentonite and DTMA–bentonite could be employed as low-cost alternatives to activated carbon in wastewater treatment for the removal of color which comes from textile dyes.