Dissolution of Iron Oxides

Abstract

This paper presents an in depth analysis of the DCB (dithionite-citrate-bicarbonate) method popularly adopted for iron oxide removal from clays as outlined by Mehra and Jackson (1960). We reviewed the reaction conditions of the DCB method and found several inconsistencies in the selection of procedures such as pH, method of washing, etc. We then carried out a theoretical analysis of the chemistry of dithionite reduction, deduced the effect of pH on the reduction potential and studied the fundamental mechanisms of iron dissolution. Analysis indicates that the basic arguments on which the DCB method is based, is not in agreement with theoretical facts. These flaws are discussed. To overcome the shortcomings of the DCB method, an alternative DCO (dithionite-carbonate-oxalate) method as proposed by Goswami et al. (1995) is briefly described here.