Adsorption of aniline and toluidines on montmorillonite
- Univ. of Tennessee, Knoxville, TN (United States)
Bentonite clay liners are commonly employed to mitigate the movement of contaminants from waste disposal sites. In order to assess the ability of clay liner material to restrict the mobility of amine compounds under a variety of chemical conditions and to further elucidate amine adsorption characteristics, the adsorption of aniline and o-, m-, and p-toluidine on Ca[sup 2+]- and K[sup +]-saturated Wyoming bentonite (SWy-1) was investigated. Adsorption experiments were performed under conditions of varied pH and ionic environment. Amine adsorption on montmorillonite is pH dependent. Maximum amine adsorption occurs when solution pH is approximately equal to the pK[sub a] of the anilinium ion deprotonation reaction (pH 4.45-5.08). An amine adsorption envelope results from the combined influence of increasing anilinium ion and anilinium-aniline complex formation (as pH decreases to the pK[sub a]) and amine competition with H[sup +] for surface sites, decreasing anilinium-aniline complex concentration, and decreasing aniline available for water bridging with exchangeable Ca[sup 2+] and K[sup +] (as solution pH decreases below the pK[sub a]). For any given amine, maximum adsorption increases with decreasing ionic strength. Maximum amine adsorption is greater in the Ca[sup 2+] systems than in the K[sup +] systems at equivalent cation charge and reflects the formation of an amine water bridge with the exchangeable Ca[sup 2+]. Amine adsorption is also greater in chloride systems compared with sulfate systems at comparable cation concentrations, possibly due to the formation of aqueous anilinium-sulfate complexes. The amine compounds are retained mainly by bentonite through a cation exchange process, the capacity of the clay to adsorb the amine compounds being a significant percentage of the exchange capacity at the pK[sub a]. However, amine retention decreases with increasing pH and is minimal at solution pH values greater than 7. 19 refs., 6 figs.
- OSTI ID:
- 6899986
- Journal Information:
- Soil Science; (United States), Vol. 158:3; ISSN 0038-075X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
ANILINE
ADSORPTION
BENTONITE
PERFORMANCE TESTING
TOLUIDINES
WASTE DISPOSAL
LINERS
MONTMORILLONITE
PH VALUE
AMINES
AROMATICS
CLAYS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MANAGEMENT
MATERIALS
ORGANIC COMPOUNDS
SORPTION
TESTING
WASTE MANAGEMENT
052002* - Nuclear Fuels- Waste Disposal & Storage
540220 - Environment
Terrestrial- Chemicals Monitoring & Transport- (1990-)