Sorption of Organic Compounds by Al And Zr-Hydroxy-Intercalated and Pillared Bentonite

Winnie Matthes and Guenther Kahr
Laboratory for Clay Mineralogy, Division of Geotechnical Engineering, Swiss Federal Institute of Technology, CH-8093 Zurich, Switzerland
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Abstract: Owing to their large and chemically active surface, hydroxy-intercalated and pillared clays can be potent sorbents for organic compounds. The sorption behavior of Al and Zr-hydroxy-intercalated bentonite (HAl−, HZr−MX80), Al and Zr-pillared bentonite (Al-MX80, Zr-MX80), and a commercial Al-pillared bentonite (EXM 534) for 3-chloroaniline (3-CA), atrazine (AT), and 3-chlorophenol (3-CP) was investigated. The results were compared with the sorption behavior of the untreated Na-rich bentonite (MX80) and granulated activated carbon (GAC). Also the influence of the salinity of the sorbate and the age of the sorbents was studied.

Al and Zr-hydroxy-intercalated and pillared bentonites sorbed higher amounts of 3-CA, AT, and 3-CP than the untreated bentonite. The quantities sorbed related to the electron-donating properties of the sorbate and the acidity of the sorbents. Sorbed quantities increased from the hydroxy-intercalated to the pillared species, and from the Al to the Zr forms. The organic bases, 3-CA and AT, were sorbed in higher quantities than the organic acid 3-CP. For AT, the sorbents exhibited a high affinity. Aging of the samples and a high ionic strength of the sorbate reduced the sorption of 3-CA, whereas the sorption of AT was not affected greatly. The sorption capacity of GAC for organic bases was generally higher than that of the hydroxy-intercalated and pillared bentonites.

The data suggest that at initial concentrations at a ppm level, 3-CA and AT can be entirely removed from aqueous solutions by Al and Zr-hydroxy-intercalated and pillared bentonites. These materials, especially Zr-pillared bentonites, represent potent alternative sorbents for atrazine, chloroanilines, and probably a wide range of other organic bases.

Key Words: Activated Carbon • Al-Pillared Montmorillonite • Atrazine • 3-Chloroaniline • 3-Chlorophenol • Sorption • Zr-Pillared Montmorillonite

Clays and Clay Minerals; December 2000 v. 48; no. 6; p. 593-602; DOI: 10.1346/CCMN.2000.0480601
© 2000, The Clay Minerals Society
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