Adsorption and isothermal models of atrazine by zeolite prepared from Egyptian kaolin Tarek S. Jamil a, * , Tarek A. Gad-Allah a , Hanan S. Ibrahim a , Tamer S. Saleh b a Water Pollution Research Department, National Research Centre, Cairo 12311, Egypt b Green Chemistry Department, National Research Centre, Cairo 12311, Egypt article info Article history: Received 14 September 2010 Accepted 9 November 2010 Available online 16 November 2010 Keywords: Zeolite Egyptian kaolin Atrazine Adsorption abstract The adsorption behavior of Atrazine on zeolites, prepared from Egyptian kaolin, has been studied in order to consider the application of these types of zeolites in water purification. The batch mode has been employed, using atrazine solution of concentration ranging from 2 to 10 mg/l. The adsorption capacity and distribution coefficients (K d ) were determined for the adsorption system as a function of sorbate concentration. It was found that, under the studies concentrations, the percent of adsorbed atrazine on both zeolites match to Langmuir and Freundlich adsorption models. The constants of each model were calculated to assess the adsorption behavior of atrazine on each type of zeolite. According to the equi- librium studies, adsorption of atrazine on zeolite X at lower concentrations is much better than that on zeolite A. The application of DublineKaganereRadushkevich model revealed physisorption endothermic adsorption process for both zeolites. These results show that natural zeolites hold great potential to remove hazardous materials such as atrazine from water. Ó 2010 Elsevier Masson SAS. All rights reserved. 1. Introduction Although banned for most uses in the European Union accord- ing to the Regulation of European Commission No. 775/2004 (04/247), atrazine [2-chloro-4-ethylamino-6-isopropylamino- s-triazine] is still worldwide used as herbicide [1,2]. Consequently, contamination of water and soil by atrazine is a major environ- mental issue and often requires extensive decontamination treat- ments. Atrazine has been widely used as a pre- and post-emergent herbicide to control broad leaf weeds in field crops, orchards and non-cropped areas [3]. Due to its widespread use, long-term persistence in soil, greater leaching potential and relatively high solubility in water, atrazine is frequently detected in ground, surface and drinking waters [4,5]. Atrazine contamination of surface and subsurface waters has heightened public concern over its environmental impact. Recently, atrazine is recognized as an endocrine disruptor for mammals [6] and aquatic life [7]. The sorption and desorption processes play an important role in determining the fate of atrazine in the environment. Natural zeolites are safe, environmentally friendly and naturally occurring minerals. The structures of zeolites consist of three- dimensional frameworks of SiO 4 and AlO 4 tetrahedra. The aluminum ion (Al) is small enough to occupy the position in the center of the tetrahedron of four oxygen atoms, and the isomor- phous replacement of Si 4þ by Al 3þ produces a negative charge in the lattice. The net negative charge is balanced by the exchangeable cation [sodium (Na), potassium (K), or calcium (Ca)]. These cations are exchangeable with certain cations in solutions [8]. The fact that zeolite exchangeable ions are relatively innocuous (Na, Ca, and K ions) makes them particularly suitable for removing undesirable materials from industrial or agriculture effluent waters [9]. In this study, the adsorption behavior of atrazine on two types of zeolites (X and A), prepared from Egyptian kaolin, was studied with the aim to use them as alternatives for activated carbon in water treatment processes. Langmuir and Freundlish adsorption models were applied to assess the adsorption process. 2. Material and methods 2.1. Preparation of zeolites Zeolite was prepared using an Egyptian Kaolin. The chemical composition and physical properties of natural Egyptian Kaolin are shown in Table 1 . Commercial sodium silicate solution (Na 2 Si 2 O 5 ) was used as the source of silicone and commercial sodium hydroxide was used as alkaline solution with different percentages according to the required type of zeolites. Preparation of the two * Corresponding author. National Research Center, El Buhouth Street, P.O. Box 12311, Dokki, Cairo, Egypt. Tel.: þ20 (12) 376 3699; fax: þ20 (2) 3337 1479. E-mail address: omaytarek73@yahoo.com (T.S. Jamil). Contents lists available at ScienceDirect Solid State Sciences journal homepage: www.elsevier.com/locate/ssscie 1293-2558/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.solidstatesciences.2010.11.014 Solid State Sciences 13 (2011) 198e203