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

It is generally believed that the success of a permanent lunar base would r ely on its near self-sufficiency in crucial life-sustaining, habitat and op erating materials. Although these materials can be extracted from soils and ores, it is imperative that such processing be as simple, efficient and re liable as possible. A candidate processing technology for producing concent rated ilmenite, from which oxygen can be extracted for human use on the moo n, is the triboelectrostatic separation method. In this research, an experimental study was conducted to investigate the fu ndamentals of triboelectrification and the potential of applying these fund amentals to triboelectrostatic separation for mineral beneficiation. Five s amples representing minerals typical of those found in lunar regolith from the plagioclase group - albite, the pyroxene group - augite, as well as ilm enite, forsterite and quartz were mixed at size ranges of + 200 to - 140 me sh (75-106 mu m). The charge polarity and magnitude on the particle surface as a consequence of impacting a copper tube surface were measured. The rel ative work functions of these minerals were then qualitatively predicted. T he mixtures were also subjected to purification/beneficiation tests by usin g our analytical triboelectrostatic separator. The parent mineral mixtures and their separated fractions were characterized by optical microscopy to d etermine to what extent the mixtures were beneficiated. These preliminary r esults show that dry triboelectrostatic separation has potential to be a si mple and efficient method to separate ilmenite from a physical mixture of c losely related minerals. (C) 1999 Elsevier Science B.V. All rights reserved .