title: Interactions of hydrophobic fractions of dissolved organic matter with Fe(3+) - and Cu(2+)-montmorillonite.
abstract: Interactions of dissolved organic matter (DOM) with clays can significantly affect a variety of soil processes. We studied adsorption and fractionation of hydrophobic acid (HoA) and hydrophobic neutral (HoN) fractions of DOM on Cu(2+)- and Fe(3+)-montmorillonite. Adsorption of both samples was higher on Fe(3+)-montmorillonite than on Cu(2+)-montmorillonite. A pH increase of about one unit was recorded followed by HoA adsorption by Fe(3+)-montmorillonite. This suggested exchange of negatively charged DOM groups on surface hydroxyl groups of Fe(3+)-montmorillonite surfaces. Adsorption of HoA on Cu(2+)-montmorillonite and HoN on Fe(3+)- and Cu(2+)-montmorillonites was governed mainly by van der Waals interactions. Spectroscopic analyses showed a distinct HoA fractionation by molecular size and aromaticity only by Fe(3+)-montmorillonite. On the basis of the pH measurements (increase in pH following adsorption of acid components) and enhanced DOM fractionation by molecular size and aromaticity we suggest that DOM reacted with Fe(3+)-montmorillonite similar to goethite.
authors.affiliation: Department of Soil and Water Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel.
authors.forename: Tamara
authors.initials: T
authors.lastname: Polubesova
authors.forename: Yona
authors.initials: Y
authors.lastname: Chen
authors.forename: Rotem
authors.initials: R
authors.lastname: Navon
authors.forename: Benny
authors.initials: B
authors.lastname: Chefetz
mesh_terms: D000327:Adsorption; D001546:Bentonite / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D012987:Soil / Q000032:analysis*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D005290:Ferric Compounds; D012987:Soil; D001546:Bentonite; D003300:Copper