Adsorption of Organic Matter at Mineral/Water Interfaces: 7. ATR-FTIR and Quantum Chemical Study of Lactate Interactions with Hematite Nanoparticles

Journal Article · Thu Dec 04 04:00:00 EST 2008 · Langmuir

DOI:https://doi.org/10.1021/la800122v· OSTI ID:1006989

Ha, Juyoung; Yoon, Tae Hyun; Wang, Yingge; Musgrave, Charles B

The interaction of the l-lactate ion (l-CH{sub 3}CH(OH)COO{sup -}, lact{sup -1}) with hematite ({alpha}-Fe{sub 2}O{sub 3}) nanoparticles (average diameter 11 nm) in the presence of bulk water at pH 5 and 25 C was examined using a combination of (1) macroscopic uptake measurements, (2) in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and (3) density functional theory modeling at the B3LYP/6-31+G* level. Uptake measurements indicate that increasing [lact{sup -1}]{sub (aq)} results in an increase in lact{sup -1} uptake and a concomitant increase in Fe(III) release as a result of the dissolution of the hematite nanoparticles. The ATR-FTIR spectra of aqueous lact{sup -1} and lact{sup -1} adsorbed onto hematite nanoparticles at coverages ranging from 0.52 to 5.21 {mu}mol/m{sup 2} showed significant differences in peak positions and shapes of carboxyl group stretches. On the basis of Gaussian fits of the spectra, we conclude that lact{sup -1} is present as both outer-sphere and inner-sphere complexes on the hematite nanoparticles. No significant dependence of the extent of lact{sup -1} adsorption on background electrolyte concentration was found, suggesting that the dominant adsorption mode for lact{sup -1} is inner sphere under these conditions. On the basis of quantum chemical modeling, we suggest that inner-sphere complexes of lact{sup -1} adsorbed on hematite nanoparticles occur dominantly as monodentate, mononuclear complexes with the hydroxyl functional group pointing away from the Fe(III) center.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: USDOE
• OSTI ID: 1006989
• Journal Information: Langmuir, Journal Name: Langmuir Journal Issue: (13) ; 2008 Vol. 24; ISSN LANGD5; ISSN 0743-7463
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
58 GEOSCIENCES
ADSORPTION
DENSITY FUNCTIONAL METHOD
DISSOLUTION
HEMATITE
INTERACTIONS
INTERFACES
LACTATES
SORPTIVE PROPERTIES
SPECTROSCOPY
UPTAKE
WATER