Reduction of Oxide Minerals by Hydrogen Plasma: An Overview

Carbothermic reduction of oxide minerals is one of the major routes to obtain the corresponding metals. This process produces a lot of CO2, which is responsible for greenhouse effect. Alternatively, hydrogen plasma containing hydrogen in atomic, ionic, and excited states can reduce almost every metal oxide even at lower temperatures. Besides this advantage, plasma processing also offers kinetic advantages. Further, hydrogen-water cycle does not pose any environmental problems. However, reduction of metal oxides in hydrogen plasma is not so straightforward-there are issues relating to introduction of material into the plasma zone, residence time, reverse reaction, and scale-up that must be resolved-yet, it holds the key to future environmental challenges particularly with respect to CO2 emission. This paper provides an overview of reduction of oxide minerals by hydrogen plasma. The influences of various reaction conditions particularly with respect to reduction of oxides are discussed and some aspects of both thermal and non-thermal cold plasma linking oxidative as well as dissociative reduction are presented.