MP4 Organic, Metallic, Organometallic Pollutants and Method
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(CHE-1118-031350) Configurations of Montmorillonite-Sorbed Myristylpyridinium Cation and Their Influences on Uptakes of Organic Compounds.

Chen, Baoliang¹, Zhu, Lizhong², ¹ Zhejiang University, Hangzhou, Zhejiang, PR China² Zhejiang University, Hangzhou, Zhejiang, PR China

ABSTRACT- Despite that sorption characteristics of organoclays have been extensively studied for their application in pollutants abatement, more information is needed to elucidate the transition in sorption mechanism(s) with the configuration of clay-sorbed surfactant. Variations in configuration of sorbed myristylpyridinium (MP⁺) surfactant cation with its loading levels in montmorillonite were examined by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR); the attractive force from clay basal surfaces to both of sorbed-MP⁺ and water molecule in the interlayers were estimated by thermogravimetric analysis (TG-DTG). At low loading levels (i.e., < CEC), MP⁺ was sorbed mainly by cation exchange to clay basal surfaces to form tightly-adhered "organic films" (i.e. flat-layer). With increasing MP⁺loading, the sorbed MP⁺ gradually changed into a less confined "phase-like medium" (i.e. paraffin-type structures) via London attraction forces. The attractive forces between mineral basal surfaces and sorbed-MP⁺ varied with the interlayer spacing and the stacking of MP⁺. Sorption of phenol and naphthalene to the resultant MP⁺-clay was a function of the configuration of MP⁺ aggregates on clay surfaces. At low MP densities, the sorbed-MP film acted as an effective adsorbent for organic compounds over water. The carbon-normalized solute distribution coefficients (K_sf) were exceptionally large and increased with MP⁺ densities up to ∼340 (phenol) and ∼15000 mL⋅g^-1 (naphthalene). At high MP+ loadings, the MP⁺ aggregates transformed into a partition-like medium and the K_sf values decreased sharply and leveled off to ∼140 (phenol) and ∼5000 mL⋅g^-1 (naphthalene) at 2.3-2.5 CEC for MP⁺. Nonetheless, due to the enhanced MP⁺ packing density within clay interlayer, the solute K_sf with confined sorbed-MP⁺ phase exceeded the corresponding aqueous micelle-water partition coefficients (K_mc).

Key words: Organoclay, Configuration, Organic pollutants, Sorption mechanism(s)