RECOVERY OF PGMS FROM MINE SLUDGE BY LEACHING

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7105-98-8 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 11, 987-994 pp, DOI: 10.5593/sgem2017/11/S04.126

ABSTRACT

South Africa host massive deposits of Platinum Group Metals (PGMs) in the Igneous Bushveld Complex. These deposits have been mined for a long time and in the process Mine sludge has been produced. It has been piled up and there is need to recover PGMs locked in it. The conventional way of processing PGMs has proved to be very difficult due to ultra-fines in the sludge that causes major loses during flotation. An alternative hydrometallurgical process for recovery of PGMs from a mine sludge by leaching using a mixture of hydrochloric acid and different oxidizing agents was investigated. It was found that the mine sludge contained 8.93 g/t Pt, 6.99 g/t Pd, 2.79 g/t Ru and minor percentages of Rh, Ir, and Au. It had a particle size distribution (PSD) of 84.64% passing 38 microns. Major mineral phases present are sphalerite, chalcopyrite, pentlandite, covellite, bornite, chromite, and silica as the main gangue. HCL + H2O2 (1:1) combination managed to leach all the PGMs and gold. HCL + Ferric Chloride (1:1) combination managed to leach Pt, Rh and Ru very well but it could not leach Pd. Further investigation on the optimization of the leaching conditions is being done.

Keywords: Mine sludge, leaching, oxidizing agents and Platinum group metals.