title: Heavy metal sorption at the muscovite (001)-fulvic acid interface.
abstract: The role of fulvic acid (FA) in modifying the adsorption mode and sorption capacity of divalent metal cations on the muscovite (001) surface was evaluated by measuring the uptake of Cu(2+), Zn(2+), and Pb(2+) from 0.01 m solutions at pH 3.7 with FA using in situ resonant anomalous X-ray reflectivity. The molecular-scale distributions of these cations combined with those previously observed for Hg(2+), Sr(2+), and Ba(2+) indicate metal uptake patterns controlled by cation-FA binding strength and cation hydration enthalpy. For weakly hydrated cations the presence of FA increased metal uptake by approximately 60-140%. Greater uptake corresponded with increasing cation-FA affinity (Ba(2+) ≈ Sr(2+) < Pb(2+) < Hg(2+)). This trend is associated with differences in the sorption mechanism: Ba(2+) and Sr(2+) sorbed in the outer portion of the FA film whereas Pb(2+) and Hg(2+) complexed with FA effectively throughout the film. The more strongly hydrated Cu(2+) and Zn(2+) adsorbed as two distinct outer-sphere complexes on the muscovite surface, with minimal change from their distribution without FA, indicating that their strong hydration impedes additional binding to the FA film despite their relatively strong affinity for FA.
authors.affiliation: Department of Earth and Environmental Sciences, 845 West Taylor Street MC-186, University of Illinois at Chicago, Chicago, Illinois 60607, United States. sslee@anl.gov
authors.forename: Sang Soo
authors.initials: SS
authors.lastname: Lee
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Nagy
authors.forename: Changyong
authors.initials: C
authors.lastname: Park
authors.forename: Paul
authors.initials: P
authors.lastname: Fenter
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D001578:Benzopyrans / Q000737:chemistry*; D019216:Metals, Heavy / Q000302:isolation & purification*; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; D001578:Benzopyrans; D019216:Metals, Heavy; C517971:muscovite; C005023:fulvic acid