Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres A clay–vesicle system for water purification from organic pollutants Tomas Undabeytia a,Ã , Shlomo Nir b , Trinidad Sa ´ nchez-Verdejo a , Jaime Villaverde a , Celia Maqueda a , Esmeralda Morillo a a Institute of Natural Resources and Agrobiology, CSIC, Apdo 1052, 41080 Sevilla, Spain b Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot 76100, Israel article info Article history: Received 1 February 2007 Received in revised form 3 September 2007 Accepted 13 September 2007 Available online 20 September 2007 Keywords: Clay Vesicle Water purification Sedimentation Sand filter Organic pollutants abstract Vesicle–clay complexes in which positively charged vesicles composed of didodecyldi- methylammonium bromide (DDAB) were adsorbed on montmorillonite removed efficiently anionic (sulfentrazone, imazaquin) and neutral (alachlor, atrazine) pollutants from water. These complexes (0.5% w:w) removed 92–100% of sulfentrazone, imazaquin and alachlor and 60% of atrazine from a solution containing 10 mg/L of it. A synergistic effect on the adsorption of atrazine was observed when all pollutants were present simultaneously (30 mg/L each), its percentage of removal being 85.5. Column filters (18 cm) filled with a mixture of quartz sand and vesicle–clay (100:1, w:w) were tested. For the passage of 1 L (25 pore volumes) of a solution including all the pollutants at 10 mg/L each, removal was complete for sulfentrazone and imazaquin, 94% for alachlor and 53.1% for atrazine, whereas removal was significantly less efficient when using activated carbon. A similar advantage of the vesicle–clay filter was observed for the capacities of removal. & 2007 Elsevier Ltd. All rights reserved. 1. Introduction Water purification procedures have employed flocculation, ion exchange, oxidation/reduction, aeration, chlorination, media filters and activated carbon (AC) (Beall, 2003). AC has usually been employed in fixed bed columns for wastewater treatment and environmental remediation, which has been efficient in the removal of certain pesticides, surfactants and chlorine (Paune et al., 1998). However, the presence of large molecules, such as humic acids, emulsified oil or grease, will reduce the adsorbed amounts because of pore constriction; blockage of the primary micropores and direct competition for adsorption sites (Pelekani and Snoeyink, 2001). Natural and modified clay minerals and zeolites are good candidates for improving AC performance, because they have large surface areas for retention of pollutants (Ruzinski et al., 1994; Li et al., 2000; Watanabe et al., 2004). Calcined hydrotalcites can remove very efficiently organic molecules, such as anionic pesticides (Li et al., 2005), or phenols (San Miguel et al., 2003). The hydrophilic surface of montmorillo- nite can be partiallly or fully modified to hydrophobic by adsorption of cationic surfactants (Zhang et al., 1993; Smith and Galan, 1995; Xu et al., 1997; Borisover et al., 2001). Organoclays were shown to compete with AC for retention of a variety of organic contaminants (Beall, 2003; Ake et al., 2003). The use of organoclays to enhance carbon filtration in industrial processes is starting to be implemented (Alther, 2002). The objective of the current work is to design an efficient technology for water purification from organic pollutants by using a vesicle–clay system. Pollutants will bind to vesicles formed by the cationic double-chain surfactant ARTICLE IN PRESS 0043-1354/$ - see front matter & 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2007.09.004 Ã Corresponding author. Tel.: +34 954624711; fax: +34 954624002. E-mail address: undabeyt@irnase.csic.es (T. Undabeytia). WATER RESEARCH 42 (2008) 1211– 1219