Recovery of silver and mercury from COD samples by iron cementation

Abstract

Cementation experiments were conducted on solutions containing mercury and silver and on actual wastes from chemical oxygen demand to assess mercury and silver recovery with iron as the reductant. Reaction order, reaction rate, removal efficiency, and stoichiometry of the reaction were evaluated. Reactions were half-order with respect to the noble ion concentration. The ratio of iron dissolved to noble metal removed indicated that the amount of iron used in the reactions was greater than the theoretical requirement for both metals. The relationship between the iron consumption ratio and initial noble metal concentration was investigated. Removal efficiencies of better than 99% for silver and mercury were readily attainable. The thickness of the mercury film deposited from single-solute mercury solutions was directly proportional to the ratio of initial mercury concentrations to reductant surface area. 13 references, 14 figures, 4 tables.