BacTech produces first commercial-sized copper cathodes

Partners BacTech Enviromet (YBA-V), Industrias Peoles and Mintek of South Africa have produced the first commercial-sized copper cathodes from copper concentrate using their proprietary bioleach process technology at their demonstration plant in Monterrey, Mexico.

Procesos Biometalurgicos (PBM), a joint venture company representing all three partners, has produced several tonnes of cathode using an integrated bioleach, solvent extraction and electrowinning circuit, with design capacity of 500 kg of copper per day. The plant is running on a mix of four concentrates, three of those from Peoles-owned mines.

BacTech’s CEO Geoffrey Donohue said, "The production of commercial-sized copper cathodes is a clear demonstration that the BacTech-Mintek proprietary bioleach process technology is able to recover copper from sulphide concentrates. Given the environmental, capital and operating cost advantages that the technology offers over traditional treatment processes it is only a matter of time before bioleaching combined with solvent extraction and electrowinning becomes the process of choice in the US$7-billion smelting industry and for other base metal projects.”

The production of the copper cathodes represents a significant step towards the completion of PBM’s feasibility study of a commercial, 25,000-tonne-per-year copper and zinc bioleach plant. The study, which is due in late February 2002, is expected to confirm an internal rate of return of 20% or greater on a projected investment of US$50 million.

The BacTech-Mintek proprietary bioleach process employs environmentally harmless, naturally occurring micro-organisms that live on inorganic material such as pyrite, arsenopyrite and other metal sulphides, including chalcocite and chalcopyrite.

A continuous stream of slurried concentrate is fed into primary reactors, or tanks, containing a suspension of bacteria in a mildly acidic environment. There, chemical and biological forces work together to oxidize the metal sulphide to form acid-soluble sulphates. Iron, arsenic and base metals (copper, cobalt and zinc) pass into solution, which can be separated from the residue and treated by conventional processing methods, such as solvent extraction.

The method avoids the problem of sulphur gas production and the release of other toxic elements related to traditional roasting and smelting. It can also boost recovery rates from refractory ores, which resist normal treatment.

The partners also say that they continue to review a number of other base and precious metal opportunities that may be amenable to the bioleaching process.

Under a 1999 agreement with BacTech and Mintek, Peoles holds the exclusive right to participate, with a 55% interest, in commercial bioleaching operations for copper in Mexico plus five other Latin American countries, including Venezuela, Bolivia, Guatemala, Argentina and Colombia.

Peoles will have the option to increase its interest to 60% in any Mexican project by funding half of BacTech and Mintek’s share of capital requirements. BacTech and Mintek would then each hold 20%.