EFFECTS OF PH, SOLID-SOLUTION RATIO, IONIC-STRENGTH, AND ORGANIC-ACIDS ON PB AND CD SORPTION ON KAOLINITE

Potentiometric and ion-selective electrode titrations together with batch sorption/desorption experiments, were performed to explain the aqueous and surface complexation reactions between kaolinite, Pb, Cd and three organic acids. Variables included pH, ionic strength, metal concentration, kaolinite concentration and time. The organic acids used were phydroxybenzoic acid, o-toluic acid, and 2,4-dinitrophenol. Titrations were used derive previously unavailable aqueous conditional stability constants for the organometallic complexes. Batch results showed that aqueous lead-organic complexation reduced sorption of Pb by kaolinite. Cadmium behavior was similar, except for 2,4-dinitrophenol, where Cd sorption was increased. Metal sorption increased with increasing pH and decreasing ionic strength. Distribution ratios (K(d's)) decreased with increasing solid/solution ratio. The subsurface transport of lead and cadmium may be enhanced via complex interactions with organic wastes or their degradation products and sorbent mineral surfaces.