Bonding of chlorophenols on iron and aluminum oxides

Journal Article · Sun Mar 31 23:00:00 EST 1991 · Environmental Science and Technology; (United States)

DOI:https://doi.org/10.1021/es00016a015· OSTI ID:5225540

Kung, K S; McBride, M B ^[1]

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1. Cornell Univ., Ithaca, NY (United States)

The adsorption of 10 chlorophenols on synthetic, naturally occurring iron and aluminum oxides was studied to elucidate the mechanism of binding and relative bond strength of the chlorine-substituted phenols was identified by spectroscopic methods. Chlorophenolates were found to be chemisorbed on oxide surfaces via an inner-sphere coordination. Chlorophenols also bonded on oxides by weak physical forces (H bonding and condensation), but these types of weak bonding were identified only when adsorption occurred from the vapor phase onto dry surfaces. Physisorbed chlorophenols, unlike chemisorbed molecules, were readily removed from oxide surfaces by washing with water. Poorly crystallized iron and aluminum oxides showed similar mechanisms of chlorophenol binding, although the bond for chlorophenolate chemisorbed on iron oxide was stronger than that on aluminum oxide. Only physically adsorbed chlorophenols were detected on crystalline gibbsite, suggesting that the dominant (001) crystal face, with surface hydroxyl groups doubly coordinated to Al, was not specifically reactive with the chlorophenols. Chemisorption, however, was identified on the crystalline iron, geothite. From the extent of perturbation of aromatic ring electrons, the surface bond strength for chlorophenolates on aluminum oxide was found to correlate with the Lewis basicity of the phenolate anions (the higher the pK{sub {alpha}} of the chlorophenols, the stronger the surface bond). Nevertheless, the amount of chlorophenol adsorbed on noncrystalline iron oxide at controlled pH of 5.4 was limited by the extent of deprotonation (the lower the pK{sub a}, the more adsorption).

• OSTI ID: 5225540
• Journal Information: Environmental Science and Technology; (United States), Journal Name: Environmental Science and Technology; (United States) Vol. 25:4; ISSN ESTHA; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
54 ENVIRONMENTAL SCIENCES
540220 -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
540320 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
ABSORPTION SPECTROSCOPY
ADSORPTION
ADSORPTION ISOTHERMS
ALUMINIUM COMPOUNDS
ALUMINIUM HYDROXIDES
ALUMINIUM OXIDES
ANIONS
AROMATICS
BASES
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTIONS
CHEMISORPTION
CHLORINATED AROMATIC HYDROCARBONS
DATA
EXPERIMENTAL DATA
GIBBSITE
GOETHITE
HALOGENATED AROMATIC HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXIDES
HYDROXY COMPOUNDS
INFORMATION
INFRARED SPECTRA
IONS
IRON COMPOUNDS
IRON OXIDES
ISOTHERMS
LEWIS BASES
MILLER INDICES
MINERALS
NUMERICAL DATA
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHENOLATES
PHENOLS
SEPARATION PROCESSES
SORPTION
SPECTRA
SPECTROSCOPY
SURFACES
TRANSITION ELEMENT COMPOUNDS