Evaluation of performance of chemically treated date stones: Application for the removal of cationic dyes from aqueous solutions

Chemically treated date stones (CTDS) used in this study as adsorbent for the removal of methylene blue (MB) and crystal violet (CV) from aqueous solutions in batch system. The effect of contact time, initial dye pH, temperature and initial dye concentration on the adsorptive removal process was studied. The results show that the removal of MB and CV is rapid and superior adsorption efficiency of MB and CV onto CTDS. In this study Langmuir and Freundlich isotherms were investigated for adsorption of MB and CV onto CTDS. The Langmuir isotherm has the highest correlations coefficients, with maximums monolayers capacities of MB and CV were 515.46 mg/g and 543.47 mg/g, at 50 degrees C, respectively. Pseudo-first-order and pseudo-second-order models were studied to analyze adsorption kinetics. The result shows the adsorption kinetic is the best with pseudo-second-order model. Desorption and regeneration experiments using HNO3 (0.1 N) eluent were only possible with CTDS, which performed well in four repeated cycles with high MB and CV removal efficiencies. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.