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MEI Online: Hydrometallurgy: Latest News: November 12th 2003


Click for more info on Biohydrometallurgy '18

   :: Nickel and Cobalt Salvage from Laterite Leach Tailings  

The three nickel laterite plants in Western Australia extract nickel and cobalt from lateritic ores using the pressure acid leach process. After dissolving the nickel and cobalt with acid at high temperatures and pressures, the metal-containing liquid is separated from the solid residue before further processing.

This separation is not completely efficient and 5-10% of the nickel and cobalt is lost to the tailings with the solid waste. Zaimawati Zainol, a Parker Centre PhD student, has developed a process to reclaim the lost metals and generate significant additional revenue for the producers.

Zaima’s process utilises an ion-exchange resin made of synthetic polymer beads to pull the nickel and cobalt out of the tailings pulp (this is referred to as resin-inpulp or RIP). Positively charged hydrogen ions attached to the resin are released and replaced by the positively charged metal ions. The nickel and cobalt are later released from the loaded resin by elution (washing) with dilute sulfuric acid.

This process for recovering nickel and cobalt has been developed in collaboration with one of the WA nickel producers.

Zaima’s initial experiments in the laboratory showed this approach would work and identified the best commercial resin for recovery of the nickel and cobalt. She says a method was also developed to remove iron and chromium ions from the pulp which would otherwise compete with the nickel and cobalt to bind to the resin.

The data from her preliminary work were used to run a computer simulation of the RIP process using a simulation program based on resin-in-pulp for gold recovery. The simulation generated the operating conditions needed to run a RIP mini-plant in the laboratory with pulp obtained from the nickel plant. The success of this mini-plant led to a larger scale pilot plant trial on-site at the nickel operation. Zaima says the pilot plant consisted of five 40 litre stirred tanks arranged in a descending series. The tailings pulp flowed continuously down through the tanks while the resin was moved from tank to tank in the opposite direction. After passing through all the tanks, the resin was transferred to columns where the nickel and cobalt attached to the resin was recovered by elution with sulfuric acid.

The RIP computer simulation was used to determine the operating conditions required for the pilot plant such as the resin concentration needed in the tanks, the resin flow rate and the pulp flow rate.

The pilot plant demonstrated the new RIP process can operate on a continuous basis with excellent nickel and cobalt recoveries from the tailings pulp. “We recovered more than 90% of the nickel and 60% of the cobalt present in the tailings," says Zaima.

Zaima says that if 10% of the nickel ends up in the tailings after leaching but 90% of that loss can be reclaimed, this extra nickel would be worth around $US 20 million a year.

The process now needs to be scaled up to a full-scale plant. “This process, if successfully implemented, should result in more widespread adoption of RIP technology in the nickel industry and in other industries," says Professor Mike Nicol, Zaima’s PhD supervisor.

Zaima’s work is part of the Parker Centre’s Leaching, Separation and Reduction Research Program.




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