Colloidal Silver Catalyzed Multi‐Electron Transfer Processes in Aqueous Solution

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Abstract
(CH3)2COH radicals were γ‐radiolytically produced in aqueous solutions of colloidal silver (2.5 · 10−4 mol/l, acetone (0.1 – 0.2 M) and propanol‐2(0.2 – 0.4 M). The radicals were able to reduce Cd2+, N2O, and NO−3 with yields of practically 100%. In the absence of colloidal silver, Cd2+ was not reduced, but N2O or NO−3 were reduced with yields of the order of 1%. The reduction processes in the presence of silver occurred in competition with the reduction of water by the organic radicals. The catalytic action of colloidal silver is explained by electron transfer from the organic radicals to the silver particles that become a pool of electrons and adsorbed hydrogen atoms. The stored electrons are then used to carry out the reduction of water or of dissolved substances. Relative rate constants for a number of multi‐electron transfer processes at the colloidal silver pool are given and details of the reaction mechanism including the action of adsorbed Hδ‐ atoms are discussed. — Radiolytically produced Cd+ ions were also reduced at the colloidal silver pool. However, Zn+, Ni+, and Co+ were found to transfer an electron to the pool. The homogeneous reaction between NO−3 and (CH3)2COH was also investigated. A rate constant of 28 M−1 s−1 was found for this reaction.

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