Potential of organic cation-saturated montmorillonite as treatment for poisoning by weak bases

The preferential adsorption of the protonated form of weak bases by montmorillonite causes an increase in the pKeff of atrazine. The effect on the acid-base equilibrium of atrazine is related to the exchangeable cation on the surface of montmorillonite. The greatest effect was produced by the presence of 3-hydroxypropylammonium-saturated montmorillonite, which caused the pKeff of atrazine to increase 5.3 units to 6.9. This shift in pKeff causes the protonated form of atrazine to be the predominate species in the pH range encountered in the GI tract and should result in a high degree of adsorption of atrazine. Fraction-bound studies confirmed this hypothesis by demonstrating virtually complete absorption of atrazine by 3-hydroxypropylammonium-saturated montmorillonite up to pH 6. The fraction-bound studies also verified that protonated atrazine is adsorbed more completely by 3-hydroxypropylammonium-saturated montmorillonite than by bentonite USP or sodium-saturated montmorillonite. It is believed that saturation of the clay surface by an organic cation alters the surface environment of the clay, which results in enhanced adsorption of the protonated form of atrazine. The potential utility of montmorillonite saturated with an organic cation as an adsorbent for the emergency treatment of poisoning by weak bases is suggested.