Radiation-induced dissolution of colloidal lead oxide

Abstract

The reduction of Ludox-stabilized colloidal PbO{sub 2} using radiolytically generated viologen radicals (ZV{sup {minus}}) has been studied by using both steady-state {gamma}-radiolysis and pulse radiolysis techniques. The steady-state radiolysis results indicate that reduction of PbO{sub 2} is consistent with the overall reaction PbO{sub 2} + 4H{sup +} + 2ZV{sup {minus}} {yields} Pb{sup 2+} + 2ZV + 2H{sub 2}O. Temporal examination of the reduction process, monitored conductometrically and spectroscopically, reveals that two main steps are involved in the overall reduction process. The first step occurs rapidly and involves a one-electron reduction of a PbO{sub 2} colloid with virtually the simultaneous adsorption of a proton. Once the colloid possesses one electron, the second electron is more difficult to transfer and a slower electron-transfer step occurs consuming, again simultaneously, three protons to produce Pb{sup 2+}.