Filtration of triazine herbicides by polymer-clay sorbents: Coupling an experimental mechanistic approach with empirical modeling Ido Gardi, Shlomo Nir, Yael G. Mishael * Dept. Soil and Water Sci., The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel article info Article history: Received 21 September 2014 Received in revised form 17 November 2014 Accepted 18 November 2014 Available online 29 November 2014 Keywords: Triazine herbicides Simazine Polymer-clay composites Competitive adsorption Filtration Modeling abstract Triazine herbicides detected in surface and groundwater pose environmental and health risks. Removal of triazine herbicides (simazine, atrazine and terbuthylazine) by polymer- clay composites was studied and modeled. Their binding by a poly 4-vinyl pyridine co styrene-montmorillonite (HPVPeCoSeMMT) composite was especially high due to specific interactions between the herbicides and polymer, mainly hydrogen bonds and p-p stack- ing. The binding kinetics to the composite was in the order of simazine > atrazine > terbuthylazine, which was in accord with their equilibrium Lang- muir binding coefficients; 44,000, 17,500 and 16,500 M 1 , respectively, which correlated with herbicide accessibility to form specific interaction with the polymer. Simazine binding kinetics to the composite was significantly faster than to granulated activated carbon (GAC), reaching 93% vs 38% of the maximal adsorption within 10 min, respectively. Her- bicide filtration by composite columns was adequately fitted by a model which considers convection and employs Langmuir formalism for kinetics of adsorption/desorption. Filtration of simazine (10 mgL 1 ) by composite columns (40 cm long, which included 26 g composite mixed with sand 1:40 (weight ratio)), was well predicted by the model with nearly 120 L purified, i.e., effluent concentrations were below regulation limit (3 mgL 1 ). Effluent concentrations from GAC columns exceeded the limit after filtering 5 L. Experi- mental results and model predictions suggest that while GAC has a high capacity for simazine binding, the composite has higher affinity towards the herbicide and its adsorption is faster, which yields more efficient filtration by composite columns. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Pesticides provide substantial agronomic and economic ben- efits. However, pesticide migration may cause soil, surface and ground-water contamination (Werf, 1996). For example, tens of thousands of tons of triazine herbicides are being manufactured and applied to fields all over the world, and are frequently detected in high concentrations in surface and groundwater (Pionke and Glotfelty, 1989; Pucarevi c et al., 2002). Due to its stability, high concentrations of atrazine have been detected in groundwater under fields years after it * Corresponding author. Tel.: þ972 8 948 9171; fax: þ972 8 948 9856. E-mail address: yael.mishael@mail.huji.ac.il (Y.G. Mishael). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/watres water research 70 (2015) 64 e73 http://dx.doi.org/10.1016/j.watres.2014.11.032 0043-1354/© 2014 Elsevier Ltd. All rights reserved.