Tests of leaching process confirm high nickel recovery from mine wastes
Further tests of Enpar's ExtrEL leaching technology on nickel mine tailings have confirmed earlier findings of high recovery rates for the valuable metal. The tests, done over the past four months, resulted in nickel recovery rates ranging from 58% to 77% and demonstrated the ability of the process to duplicate the results on demand.
Consequently, the Guelph, Ontario-based company will begin optimization of the ExtrEL leaching process during June, with completion expected in the next three months.
These results will form the basis for designing a pilot unit for relatively large-scale testing. The test results to date show power as the predominant operating cost, although at 38 cents per kilogram of nickel metal recovered, even this is considered to be quite low in view of the market value of nickel, currently standing at nearly $21 (U.S.) per kilogram.
Enpar is hoping to move through the pilot testing stage to construction of a commercial plant within the next 18 months. While preliminary calculations suggest that the capital cost of the equipment would be recovered within a year to a year and a half, the company says additional testing is still needed before firm conclusions can be made about the potential commercialization of this process.
Nevertheless, says Enpar, the ability to recover nickel from what is currently perceived as a waste material represents a major financial opportunity for the company, its shareholders and the mining industry alike. The ExtrEL leaching technology, it adds, has the potential to become a primary hydrometallurgical treatment method for the traditional concentrate from the mill floatation circuit.
Once proven on a commercial scale, the process may offer an alternative to conventional smelting facilities which require large capital investments and pose significant environmental concerns. It would enable both large and small mining companies to process the ore concentrate on-site and ship metal for refining, rather than shipping ore for primary processing.
Based on published information, Enpar estimates that there are hundreds of millions of tonnes of mill sulfide tailings containing potentially economic grades of nickel in Canada, Australia, Russia and several African nations. In many locations, these tailings are apparently similar in mineralogy to those tested by Enpar, making them suitable for treatment using the ExtrEL process. At today's market price for nickel, the in-situ value of the nickel sulfide tailings at these sites is estimated at more than $11 billion (U.S.).
The ExtrEL technology is one of a series of proprietary electrochemical processes developed and patented by Enpar for the recovery of base metals and to the treatment of wastewater and drinking water contaminated by metals or nutrients, e.g. nitrate/ammonia associated with the mining, metal processing, chemical, agricultural, municipal and waste management sectors.