Studies on Chromium (VI) adsorption on sulfonated lignite

Sulfonated lignite was prepared in order to study the adsorption behavior and the removal of Cr (VI) ions from aqueous solutions as a function of contact time, initial pH, using batch technique. Adsorption data of Cr (VI) on the sulfonated lignite were analyzed according to Langmuir Freundlich and Temkin adsorption models. Thermodynamic parameters for the adsorption system were determinated at 293 K, 303 K and 313K. (Delta H degrees = 14.16 kJ mol(-1); Delta G degrees = 4.43 to -5.71 kJ mol(-1) and Delta S = 63.42 J K-1 mol(-1)). The numerical values obtained showed that Cr (VI) adsorption is a spontaneous, entropy-driven and endothermic process. The process kinetics was evaluated by pseudo-first, pseudo-second order and Elovich kinetic models. Elovich kinetic model exhibited the highest correlation with data. These results show that the sulfonated lignite could be considered as a potential adsorbent for chromium ions in aqueous solutions. (C) 2010 Elsevier B.V. All rights reserved.