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SOLID-LIQUID SEPARATION – Processing Challenge Met at El Boleo

MEXICO - The El Boleo project, located at Santa Rosalia, Baja California Sur, Mexico, is a sediment-hosted deposit...


MEXICO – The El Boleo project, located at Santa Rosalia, Baja California Sur, Mexico, is a sediment-hosted deposit of copper-cobalt-zinc, with possible indium, gallium and germanium credits, in a clayey mineral matrix. The copper-cobalt and zinc values in the ore can be leached using sulphuric acid solutions in a slurry leach process. While the dissolution of the valuable metals into the leach solution is relatively straightforward, the subsequent separation of metal containing solution from leached solids has historically been challenging.

In order to meet this challenge, BAJA MINING of Vancouver commissioned a program of work at SGS LAKEFIELD RESEARCH to test the ability to successfully carry out solid-liquid separation and washing of the barren solids. This work was overseen by BATEMAN ENGINEERING and involved POCOCK INDUSTRIAL and OUTOKUMPU In the testing. The results have demonstrated that Boleo ores can be settled and washed in a conventional counter-current decantation (CCD) circuit utilizing high-rate thickeners.

The simplified 7,500-tonne/day Boleo flowsheet now consists of the following steps: conventional crushing, scrubbing and grinding of run-of-mine ore, a two-stage atmospheric leach, partial neutralization, solid-liquid separation utilizing high rate thickeners, copper solvent extraction and electrowinning. After iron precipitation, the copper raffinate is then stripped of the contained cobalt, zinc and residual copper utilizing a proprietary extraction system developed by COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANIZATION, Minerals Division (CSIRO). Zinc is stripped from the CSIRO extractant and is then precipitated as a saleable zinc sulphate. Cobalt is stripped into a highly purified solution and is then electrowon to produce cathode cobalt.

The next step is to build an integrated pilot plant at SGS Lakefield in November. More information is available from Baja president John Greenslade at 604-685-2323 or the investor relations department at 604-683-5774.


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