Application of acidic treated pumice as an adsorbent for the removal of azo dye from aqueous solutions: kinetic, equilibrium and thermodynamic studies
1 Department of Environmental Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran
2 Department of Environmental Health Engineering, Faculty of Health, Alborz University of Medical Sciences, Karaj, Iran
3 Ecole Nationale Supérieure de Chimie de Rennes, CNRS, Avenue du Général Leclerc, Rennes, France
4 Department of Environmental Health Engineering, Faculty of Health, Tehran University of Medical Sciences, Tehran, Iran
5 Young Researchers Club, Science and Research Branch, Islamic Azad University, Tehran, Iran
Iranian Journal of Environmental Health Science & Engineering 2012, 9:9 doi:10.1186/1735-2746-9-9Published: 5 November 2012
Colored effluents are one of the important environment pollution sources since they contain unused dye compounds which are toxic and less-biodegradable. In this work removal of Acid Red 14 and Acid Red 18 azo dyes was investigated by acidic treated pumice stone as an efficient adsorbent at various experimental conditions. Removal of dye increased with increase in contact time and initial dye concentration, while decreased for increment in solution temperature and pH. Results of the equilibrium study showed that the removal of AR14 and AR18 followed Freundlich (r2>0.99) and Langmuir (r2>0.99) isotherm models. Maximum sorption capacities were 3.1 and 29.7 mg/g for AR 14 and AR18, namely significantly higher than those reported in the literature, even for activated carbon. Fitting of experimental data onto kinetic models showed the relevance of the pseudo-second order (r2>0.99) and intra-particle diffusion (r2>0.98) models for AR14 and AR18, respectively. For both dyes, the values of external mass transfer coefficient decreased for increasing initial dye concentrations, showing increasing external mass transfer resistance at solid/liquid layer. Desorption experiments confirmed the relevance of pumice stone for dye removal, since the pH regeneration method showed 86% and 89% regeneration for AR14 and AR18, respectively.