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Title: INTERACTIONS WITH THE NON-IONIC SURFACTANT BRIJ 35 INFLUENCE SORPATION OF ATRAZINE ON K- AND CA-SMECTITES

Author
item CHAPPELL, M - IOWA STATE UNIVERSITY
item Laird, David
item THOMPSON, M - IOWA STATE UNIVERSITY
item EVANGELOU, V - DECEASED

Submitted to: Clay Minerals Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/24/2004
Publication Date: 6/24/2004
Citation: Chappell, M.A., Laird, D.A., Thompson, M.L., Evangelou, V.P. 2004. Interactions with the non-ionic surfactant Brij 35 influence sorpation of atrazine on K- and Ca-smectites [abstract]. Program and Abstracts of the Clay Minerals Society. p. 56.

Interpretive Summary:

Technical Abstract: Nonionic polyethylene oxide (PEO) surfactants like Brij 35 are commonly used in commercial herbicide formulations. Little is known about how the surfactants impact fate and efficacy of herbicides in soil environments. This work was conducted to determine how interactions between saturating cation (potassium [K] and calcium [Ca]), Brij 35, and air-drying treatments influence the sorption of atrazine on the reference smectite, Panther Creek (PC). The data showed that additions of Brij 35 up to 2100 mg L-1 suppressed atrazine sorption. Greater suppression of sorption occurred for K-PC than Ca-PC. However, atrazine sorption 'rebounded' somewhat with the addition of 6300 mg L-1 Brij 35. Sorption studies of Brij 35 in the absence of atrazine revealed that the surfactant was very strongly sorbed on both K- and Ca-PC (on the order of 105 mg kg-1 clay). Higher adsorption maximums for Brij 35 were observed on air-dried clays. X-ray diffraction (XRD) analysis of the clay suspensions showed that intercalation of Brij 35 reduced never-dried (ND) K-PC d-spacing from 1.88 nm to 1.35 nm, while minimal changes in d-spacing for ND Ca-PC were observed in suspensions. However, XRD analysis of oven-dried samples of ND Ca-PC systems revealed that the Brij 35 was present in the interlayers. Sedimentation experiments also revealed that Brij 35 induced flocculation of Ca-PC. Our results show that lower concentrations (£ 2100 mg L-1) of Brij 35 suppressed atrazine sorption by effectively blocking atrazine's access to interlayer sorption sites. A model is proposed showing how increasing concentrations of Brij 35 first inhibited, then enhanced atrazine sorption.