Journal of Hazardous Materials 168 (2009) 304–309 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Removal of Basic Red 46 dye from aqueous solution by adsorption onto Moroccan clay A. Bennani Karim a,b , B. Mounir a,∗ , M. Hachkar a , M. Bakasse c , A. Yaacoubi b a The Team of Research Analysis, Checks and Environment, High School of Technology, University Cadi Ayyad, Dar Si Aissa Road, BP 89, Safi, Morocco b The Team Environmental and Experimental Methodology, Laboratory of Organic Applied Chemistry, Faculty of the Sciences Semlalia, BP 2390, Marrakech, Morocco c The Team of Analysis of the Microphones Polluting Organic, Faculty of the Sciences, University Chouaib Doukkali, BP 20, El Jadida, Morocco article info Article history: Received 31 July 2008 Received in revised form 6 February 2009 Accepted 6 February 2009 Available online 20 February 2009 Keywords: Basic Red Moroccan clay Adsorption Isotherms Kinetics Thermodynamic parameters abstract In this study, Moroccan crude clay of Safi, which was characterized by X-ray diffraction, is used as adsor- bent for the investigation of the adsorption kinetics, isotherms and thermodynamic parameters of the Basic Red 46 (BR46) in aqueous solutions at various dye concentrations, adsorbent masses and pH val- ues. The results showed that the adsorption capacity of the dye increased by initial dye concentration and pH values. Two kinetic models (the pseudo-first-order and the pseudo-second-order) were used to calculate the adsorption rate constants. The adsorption kinetics of the basic dye followed pseudo- second-order model. The experimental data isotherms were analyzed using the Langmuir, Freundlich and Dubinin–Radushkevish equations. The monolayer adsorption capacity for BR46 dye is 54mg/g of crude clay. Nearly 20 min of contact time was found to be sufficient for the dye adsorption to reach equi- librium. Thermodynamical parameters were also evaluated for the dye–adsorbent system and revealed that the adsorption process is exothermic in nature. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Dyes are synthetic aromatic compounds which are embodied with various functional groups. They are widely used in textile, leather, paper, plastic, and other industries. Some of these dyes may degrade to produce carcinogens and toxic products [1]. Thus, the removal of dyes from effluents is important for risk assessment. Several physical or chemical processes are used to treat dye laden wastewaters. These processes include flocculation, pre- cipitation, ion exchange, membrane filtration, electrochemical destruction, irradiation and ozonation. However, these processes are costly and lead to generation of sludge or formation of by- products [2]. Among the physical methods available, adsorption process is one of the most efficient methods to remove dyes from wastewater, especially if the adsorbent is inexpensive and readily available [3]. Activated carbon is the most widely used adsorbent for dye removal, but it is too expensive [4], consequently, numer- ous low-cost alternative adsorbents have been proposed including: peat [5], sepiolite [6], montmorillonite, chitosan and nanocompos- ite [7], and pine sawdust [8]. Clays are mostly used as available adsorbent and catalyst [9]. ∗ Corresponding author at: Ecole Supérieure de Technologie, Université Cadi Ayyad, BP 89, Safi, Morocco. Tel.: +212 61 28 93 66; fax: +212 24 62 91 24. E-mail address: mounirbadia@yahoo.fr (B. Mounir). In the present work, adsorption of Basic Red 46 (BR46) dye onto Moroccan crude clay has been investigated and the obtained experimental data were analyzed using adsorption isotherm mod- els namely, Langmuir, Freundlich, and Dubinin–Radushkevich. The effect of pH, adsorbent mass and initial dye concentration has been studied. Kinetic experiments have been also conducted to deter- mine the rate of BR46 adsorption onto clay. 2. Materials and methods 2.1. Materials The basic dye used as adsorbate in the present study is C.I. Basic Red 46 (Mr = 357.5), which was purchased from SDI textile company (Safi, Morocco). The BR46 molecular structure is shown in Fig. 1. The clay used in this study was ground from the natural basin of Safi and sieved to 0.08–0.1 m size fraction. Then, it was dried at 105 ◦ C for 24 h and used for further experiments. The chemical composition of the adsorbent was determined by using Philips X’ Cem X-ray fluorescence spectrometer (XRF). The results are given in Table 1. XRD analyses of the powder sample were performed using Siemens D-5000 X-ray diffractometer. The physical properties (including BET, external surface area, total pore volume and micropore volume, as well as average pore size distri- bution) of crude clay were obtained by measuring their nitrogen adsorption–desorption isotherms at -196 ◦ C with the use of a sur- 0304-3894/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2009.02.028