Dry triboelectrostatic separation of mineral particles: a potential application in space exploration

Abstract

It is generally believed that the success of a permanent lunar base would rely on its near self-sufficiency in crucial life-sustaining, habitat and operating materials. Although these materials can be extracted from soils and ores, it is imperative that such processing be as simple, efficient and reliable as possible. A candidate processing technology for producing concentrated ilmenite, from which oxygen can be extracted for human use on the moon, is the triboelectrostatic separation method. In this research, an experimental study was conducted to investigate the fundamentals of triboelectrification and the potential of applying these fundamentals to triboelectrostatic separation for mineral beneficiation. Five samples representing minerals typical of those found in lunar regolith from the plagioclase group — albite, the pyroxene group — augite, as well as ilmenite, forsterite and quartz were mixed at size ranges of +200 to −140 mesh (75–106 μm). The charge polarity and magnitude on the particle surface as a consequence of impacting a copper tube surface were measured. The relative work functions of these minerals were then qualitatively predicted. The mixtures were also subjected to purification/beneficiation tests by using our analytical triboelectrostatic separator. The parent mineral mixtures and their separated fractions were characterized by optical microscopy to determine to what extent the mixtures were beneficiated. These preliminary results show that dry triboelectrostatic separation has potential to be a simple and efficient method to separate ilmenite from a physical mixture of closely related minerals.