title: Filtration of triazine herbicides by polymer-clay sorbents: coupling an experimental mechanistic approach with empirical 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 (HPVP-CoS-MMT) composite was especially high due to specific interactions between the herbicides and polymer, mainly hydrogen bonds and π-π stacking. The binding kinetics to the composite was in the order of simazine > atrazine > terbuthylazine, which was in accord with their equilibrium Langmuir 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. Herbicide 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 μg L(-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 μg L(-1)). Effluent concentrations from GAC columns exceeded the limit after filtering 5 L. Experimental 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.
authors.affiliation: Dept. Soil and Water Sci., The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
authors.forename: Ido
authors.initials: I
authors.lastname: Gardi
authors.affiliation: Dept. Soil and Water Sci., The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
authors.forename: Shlomo
authors.initials: S
authors.lastname: Nir
authors.affiliation: Dept. Soil and Water Sci., The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel. Electronic address: yael.mishael@mail.huji.ac.il.
authors.forename: Yael G
authors.initials: YG
authors.lastname: Mishael
mesh_terms: D000327:Adsorption; D001546:Bentonite / Q000737:chemistry*; D036262:Empirical Research; D005374:Filtration / Q000379:methods*; D006540:Herbicides / Q000737:chemistry / Q000302:isolation & purification*; D007700:Kinetics; D011108:Polymers / Q000737:chemistry*; D013816:Thermodynamics; D014227:Triazines / Q000737:chemistry / Q000302:isolation & purification*
chemical_list: D006540:Herbicides; D011108:Polymers; D014227:Triazines; D001546:Bentonite
keywords: Competitive adsorption; Filtration; Modeling; Polymer-clay composites; Simazine; Triazine herbicides