An electrolyte bleed stream from the copper tankhouse is passed through columns containing SuperLig® 83 resin, supplied by IBC Advanced Technologies, USA, which selectively extracts the bismuth. All the copper in the bleed stream is returned to the tankhouse and the level of bismuth in the electrolyte is controlled simply by varying the flowrate of the electrolyte bled to the MRT plant. The SuperLig® 83 is regenerated by stripping the bismuth using a sulphuric-acid solution. Bismuth as a saleable product can be recovered from the eluate solution either by direct precipitation of bismuth sulphate of better than 99 % purity, or by electrowinning high-purity bismuth metal.

Controlling bismuth in copper tankhouse electrolytes

Skid-mounted plants for the removal and recovery of bismuth from copper tankhouse electrolytes are being marketed by MRT Africa, an IBC-BATEMAN Company. Its molecularrecognition technology (MRT) can effectively control the bismuth contamination of electrolytes, which deleteriously affects coppercathode production and quality.

The MRT process is financially attractive, easy to implement and use and completely compatible with the tankhouse environment. Bismuth levels in the electrolyte can be reduced to below 200 ppm or even 100 ppm, which means that copper cathodes can be produced with a typical specification of less than 0,3 ppm of bismuth. The bismuth may be sold as a high-value byproduct, adding significantly to the overall financial benefit of the process.

This is an environmentally friendly closedloop process involving only refinerycompatible chemistry. The modular nature of the plant permits easy capacity increases and a wide range of bismuth concentrations can be handled to ensure that recycling of off-spec copper is minimised.

As clean copper orebodies become depleted worldwide, copper concentrates and anodes with high levels of bismuth contamination will increasingly be supplied to copper electrorefiners. Equipment such as the BATEMAN-IBC MRT bismuth-removal plant will become a standard feature of such operations. The first such plant installed at a refinery in Australia is operating as per its design specification to remove 20 t/yr of bismuth at the tankhouse. A second plant in the western hemisphere is due for commissioning in 2002.

Please contact Neill Birdsey,
General Manager, Small Projects, on +27-11-899-3191 or
email tawana@batemanengineering.com for more information.

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