Cobalt and nickel recovery from iron-rich mine drainage water

Abstract

This thesis describes a pilot-scale trial on the Morecovery project’s modular recovery system for critical raw materials (CRM), rare earth elements (REE) and base metals from mine drainage waters. The pilot-scale trial was carried out at an old Finnish nickel mine, Hitura, which was an active mine site for 45 years before being closed in late 2015.

In the trial at Hitura, the selected metals for extraction were iron, nickel and cobalt. Iron extraction proved challenging while trying to keep as much nickel and cobalt within solution as possible for later phases of the process. Amount of co-precipitating nickel and cobalt during the iron removal process was studied in different scenarios in which process pH, volume and mixing intensity was varied. The selected process comprised two stages, where the first step was to extract iron via an oxidation–precipitation reaction, leaving nickel and cobalt in the solution, and the second step was to recover nickel and cobalt selectively. Process outputs were iron-rich sludge, nickel- and cobalt-rich sludge and purified water resulting from the purification process.

The contents of this thesis are partly confidential and those sections are only to be distributed by the client, GTK.