Formaldehyde oxime leaching of metals from deep-sea manganese nodules and other ores

Abstract

Formaldehyde oxime, CH₂=NOH, has for a long time been recognized as a sensitive colorimetric reagent for manganese, copper and metals of the iron group. In alkaline medium, the oxime dissociates, forming the CH₂=NO⁻ anion which bonds to multivalent metals, giving complexes of the general formula M(CH₂NO)₆⁽⁶⁻ⁿ⁾⁻, where n is the oxidation state of the metal^1,2. Here I report the results of experiments which show that aqueous formaldehyde oxime constitutes a new and effective leaching agent for several types of ores, such as pyrolusite, malachite, heterogenite and deep-sea manganese nodules. The reagent seems particularly attractive for nodules, as the leaching is rapid, in acid as well as in neutral and or alkaline media, and at ambient and lower temperatures. Manganese nodules constitute an important potential source of nickel and especially cobalt: the amount of cobalt recoverable from the north-west equatorial Pacific alone is estimated⁵ to be 4×10⁶ tonne—of the same order as the world total land-based reserves.