Mechanical Activation of Al-oxyhydroxide Minerals-A Review

Advances in the field of mechanical activation of Al-oxyhydroxide minerals (synthetic as well as in natural bauxites) over the years around the globe are described in this review. An overview of fundamental aspects of mechanical activation with select examples of applications/examples in extractive metallurgy preludes the theme, mechanical activation of Al-oxyhydroxides. The focus is primarily on mechanically induced reactivity of largely used (and most commonly available too) Al-oxyhydroxides viz. gibbsite and boehmite. Reactivity, considered in the context of dissolution in alkali solution and transformations during thermal treatment, is reported to increase with mechanical activation. Available information is collaged to answer the question why/how does the observed effects happen. Gaps in the existing knowledge and prospects in Bayer process are also discussed.