Electrochemical aspects in hydrometallurgy

Abstract

Hydrometallurgy is concerned with extraction of metal values from ore minerals through aqueous processing. This is usually achieved in two steps, namely (i) solubilising the specific metal value into the aqueous phase and (ii) subsequently taking it out of the solution. These are heterogenous processes involving solid and liquid phases. Quite often a gaseous phase is also involved. These steps may be chemical or electrochemical in nature. The electrochemical phenomena, if present will depend on the electrical properties of the solid material and redox characteristics of the solution. The present paper discusses some electrochemical aspects of hydrometallurgical operations and describes a useful electrochemical method for studying reactions. The method is based on the study of polarization data of individual half cell reactions. Five examples are cited to discuss the following phenomena : (i) corrosion coupling, (ii) galvanic coupling, (iii) dissolution via cyclic action of a redox couple, (iv) displacement or cementation reaction and (v) precipitation under reducing conditions.