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 16,500M-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 10min, 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 (10μgL-1) by composite columns (40cm long, which included 26g composite mixed with sand 1:40 (weight ratio)), was well predicted by the model with nearly 120L purified, i.e., effluent concentrations were below regulation limit (3μgL-1). Effluent concentrations from GAC columns exceeded the limit after filtering 5L. 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.
Bibliographical noteFunding Information:
Supported by The European Commission in the framework of the Project 'Diffusion of nanotechnology based devices for water treatment and recycling – NANOWAT' (ENPI CBC MED I–B/2.1/049, Grant No. 7/1997 ).
© 2014 Elsevier Ltd.
- Competitive adsorption
- Polymer-clay composites
- Triazine herbicides