Protonation of Organic Bases in Clay—Water Systems

Samuel W. Karickhoff and George W. Bailey
Environmental Research Laboratory, U.S. Environmental Protection Agency, Athens, Georgia 30601, U.S.A.

Abstract: The extent of protonation of organic bases in clay—water systems depends upon the adsorptive properties of the organo-clay species involved, and upon the structure and degree of hydration of the clay system. Organic molecules that can disperse cationic charge over two or more condensed aromatic rings give rise to greater surface-induced protonation than do single-ring organic molecules with similar solution pKa. Protonation in clay suspensions is frequently far in excess of that predicted on the basis of electrolytic suspension pH and solution pKa of the organic base. For a given organic base, protonation in a clay film exceeds that in the suspended clay system. Protonation in an organo-clay film increases as the film moisture content decreases. The extent of protonation in organo—clay systems varies with cationic species, cationic saturation, and clay type.

Clays and Clay Minerals; August 1976 v. 24; no. 4; p. 170-176; DOI: 10.1346/CCMN.1976.0240404
© 1976, The Clay Minerals Society
Clay Minerals Society (www.clays.org)