Extraction of Copper, Nickel, and Cobalt from Ocean Manganese Nodules by Aqueous Ammonia-Ammonium Salt-Carbohydrate Solution

Abstract

Leaching of three different samples of nodules from the Pacific Ocean floors was carried out by using ammoniacal ammonium salts solutions containing carbohydrates such as D-glucose and starch. Direct reduction-leaching at 80°C or higher temperature with aqueous ammonia-ammonium chloride-glucose solution yielded high extractions of metal values of copper, nickel, and cobalt (≥80%). When aqueous ammonia-ammonium carbonate-glucose solution-was used, the extractions of manganese and iron were much lower than the case when aqueous ammonia-ammonium chloride-glucose was used, and copper, nickel and cobalt extractions were lowered some extent (Tables 3, 4). On the other hand, a higher temperature of 160°C was required to obtain high extractions of the metal from nodules in aqueous ammonia-ammonium chloride-formaldehyde (or starch) solution (Figs. 10~12). Since the behavior of manganese in the leaching process was always similar to that of copper, nickel, and cobalt, the mechanism of the leaching is considered that the three metals dissolve in the solution as these metal ammines with proceeding the reduction of manganese(IV) oxide in the nodules by carbohydrate. © 1977, The Chemical Society of Japan. All rights reserved.