RADIOTRACER ANALYSIS OF THE PHYSICOCHEMICAL STATE OF TRACE-ELEMENTS IN AQUEOUS-SOLUTIONS .3. LEAD

The physico-chemical state of trace lead in aqueous nitrate solutions (I=0.01) was studied using equilibrium calculation, free-liquid electrophoresis, dialysis and centrifugation methods and210, 212Pb. It has been found that lead is present exclusively as nonhydrolyzed cations in solutions of pH 2-3.5. Colloidal or larger particulate forms of lead exist in solutions of lower acidity (pH>4). They are of pseudocolloidal nature, i.e. they are formed by adsorption of lead on solid impurities in the studied solutions. The pseudocolloids are negatively charged at pH>5 and reversible at pH 4-7. Reversibility of the adsorption of lead on impurities decreases at pH>7. Experiments have indicated that a significant hydrolysis of bivalent lead takes place already at pH>4. Anionic hydroxo-complexes of lead predominate in alkaline solutions of pH>12. © 1979 Akadémiai Kiadó.