Use of HCl-modified bentonite clay for the adsorption of Acid Blue 129 from aqueous solutions

AbstractThe adsorption of Acid Blue 129 (AB129) from aqueous solution onto hydrochloric acid-activated montmorillonite clay (HCl-bentonite) was investigated. The activated clay was characterized by scanning electron microscopy, energy dispersive spectroscopy, and Brunauer–Emmett–Teller surface area. Batch adsorption experiments were performed to investigate the effects of pH, contact time, initial dye concentration, and temperature (10, 20, 30, and 40°C). Acidic conditions was suitable for higher adsorption of AB129, and kinetic studies demonstrate that the process followed a pseudo-second-order model. An activation energy of 23.858 kJ mol−1 was obtained for adsorption process. Adsorption data were fitted to Freundlich and Langmuir isotherms and various adsorption parameters have been calculated. Standard enthalpy (ΔH°) and standard entropy (ΔS°) were −44.90 kJ mol−1 and −68.44 kJ mol−1 K−1, respectively, showing that overall adsorption process was exothermic and is spontaneous in nature with a decrease i...