ISSN 1 746-7233, England, UK World Journal of Modelling and Simulation Vol. 9 (2013) No. 4, pp. 243-254 A new adsorption isotherm model of aqueous solutions on granular activated carbon Hossein Shahbeig 1* , Nafiseh Bagheri 2 , Sohrab Ali Ghorbanian 1 , Ahmad Hallajisani 1 , Sara Poorkarimi 2 1 School of Chemical Engineering, University College of Engineering, University of Tehran, P.O. Box 11155/4563 Tehran, Iran 2 Department of Chemical Engineering, North Tehran Branch, Islamic Azad University, Tehran, Iran (Received January 01 2013, Revised May 18 2013, Accepted September 22 2013) Abstract. Equilibrium adsorption of aniline, benzaldehyde, and benzoic acid on granular activated carbon (GAC) has been investigated. Experiments were carried out on two sizes of activated carbon. The equilibrium data were analyzed using the ordinary least square approach. The results show that the adsorption process was more effectively described by Hill and Koble-Corrigan isotherm models based on the values of the least square parameter, Durbin-Watson Test, and mean relative percent error. Furthermore, the results show that benzoic acid has been adsorbed more in comparison with the other adsorbates and benzaldehyde has been adsorbed more than aniline. Moreover, a new isotherm model has been presented which is in good agreement with experimental data. The suggested model has a 7.41% smaller error than the Hill and Koble-Corrigan models. Keywords: adsorption, isotherm, aniline, benzaldehyde , benzoic acid, modelling, GAC 1 Introduction Over the past decades, the population and social civilization have grown. Due to changes in daily life and resource use, and continuing improvement of the industrial and technologies has been accompanied by a quick modernization and metropolitan development [11, 38] . The increasing of industrial activities intensified anthropogenic attacks on ecosystems, seriously threatening human health and the environment [12, 24] . Increas- ing concern for public health and environmental quality has led to the establishment of rigid limits on the acceptable environmental levels of specific pollutants [10, 41, 48] . Thus, the removal or destruction of aniline, benzaldehyde, and benzoic acid from process or waste streams becomes a major environmental problem. The presence of these compounds even at low concentrations can be an obstacle for the reuse of water. These compounds are present in the wastewaters from coking plants, fertilizer, pharmaceutical, plastics, organic chemical, steel, and petroleum industries, dye manufacturing, and paint-stripping operations. They are con- sidered as pollutants because of their toxic and carcinogenic characteristics [33, 40] . Thus, the removal of these pollutants from wastewater stream is one of the major environmental challenges. Several methods are avail- able for removal of this material such as photocatalytic degradation [4, 28] , combined photo-Fenton and bio- logical oxidation [31] , advanced oxidation processes [42] , aerobic degradation [34] , nanofiltration membranes [2] , ozonation [29] and adsorption. In this respect, adsorption on activated carbon is an effective and useful tech- nique in the treatment of organic components containing wastewater [33, 37] . Activated carbon adsorption has been cited by the US Environmental Protection Agency as one of the best available environmental control technologies [5, 46] . Despite its industrial importance, adsorption from liquid phase has been studied much less extensively than adsorption from the vapor phase [6, 47] . Adsorption equilibrium occurred when an adsorbate * Corresponding author. Tel.: +982166957781. E-mail address: shahbeig@ut.ac.ir Published by World Academic Press, World Academic Union