Adsorption of Pb(II) on raw and organically modified Jordanian bentonite I. HAMADNEH 1 , R. ABU-ZURAYK 2 , B. ABU-IRMAILEH 2 , A. BOZEYA 2 AND A. H. AL-DUJAILI 1,* 1 Department of Chemistry, Facultyof Science, The University of Jordan, P.O. Box 11942, Amman, Jordan 2 Hamdi Mango Center for Scientific Research, The Universityof Jordan, P.O. Box 11942, Amman, Jordan (Received 7 January 2015; revised 22 June 2015; Associate Editor: George Christidis) A B S T R AC T : A comparative study using bentonite (BT), hexadecyltrimethylammonium-modified bentonite (BT-HDTMA) and phenyl fatty hydroxamic acid-modified bentonite (BT-PFHA) as adsorbents for the removal of Pb(II) has been proposed. These adsorbents were characterized by X-ray diffraction, X-ray fluorescence, Fourier-transform infrared spectroscopy and surface area measurement. Cation exchange capacity was also determined in this study. The adsorbent capabilities for Pb(II) from aqueous solution were investigated, and the optimal experimental conditions including adsorption time, adsorbent dosage, the initial concentration of Pb(II), pH and temperature that might influence the adsorption performance were also investigated. The experimental equilibrium adsorption data were tested by four widely used two-parameter equations, the Langmuir, Freundlich, Dubinin- Radushkevich (D-R) and Temkin isotherms. The monolayeradsorption capacities of BT, BT-HDTMA and BT-PFHA for Pb(II) were 149.3, 227.3 and 256.4 mg/g, respectively. The experimental kinetic data were analysed by pseudo-first order, pseudo-second order and intraparticle diffusion kinetics models. The experimental data fitted very well with the pseudo-second order kinetic model. Determination of the thermodynamic parameters, ΔG, ΔH and ΔS showed the adsorption to be feasible, spontaneous and exothermic. KEYWORDS: adsorption, bentonite, fatty hydroxamic acid, Pb(II), surfactant. Heavy metals can be toxic to humans and other forms of life even at low concentrations (Shotyk & LeRoux, 2005; Jiang et al., 2009). Lead is a potential neurotoxic metal which may be transported into water bodies by natural circulation and therefore threaten human life due to its well known toxicity, accumulation in food chains and persistence in nature. Unlike organic compounds, Pb is non-biodegradable, and, therefore, must be removed from wastewater (Unuabonah et al., 2008). The ‘limit values’ of lead in drinking water and surface water intended for drinking, as set by the European Union, United States Environmental Protection Agency and the World Health Organization are 10, 50 and 10 μg/L, respectively (Al-Haidary et al., 2011). However, a more recent USEPA document prescribes a zero lead value in the national primary drinking water standard (Abdulla et al., 2012). Lead removal by low- cost adsorbent materials may be better than traditional processes such as chemical precipitation, electrode deposition, filtration, reverse osmosis, evaporation recovery and solvent extraction (Bhattacharjee et al., 2003). Bentonite (BT) is a natural adsorbent material and its selectivity and capacity to adsorb pollutants can be improved significantly through modification (Rawajfih & Nsour, 2006; Alkaram et al., 2009; Jović -Jovičić et al., 2013). Organic modification of BT increases significantly the attenuation of some organic and inorganic pollutants (Mello et al., 2009; Li et al., 2013; Wang et al., 2013, 2014; Kooli, 2014; Simsek et al., 2014). * E-mail: ah.aldujaili1946@gmail.com DOI: 10.1180/claymin.2015.050.4.05 © 2016 The Mineralogical Society Clay Minerals, (2015) 50, 485–496