The ongoing metallurgical test work is being undertaken by Hazen Research of Golden, Colorado, and to date has demonstrated high lithium recoveries of more than 95% with short residence times using a conventional sulphuric acid leach.
The most recent tests tested two aspects:
- The potential to reduce acid consumption by recycling the leachate; and
- The potential for beneficiation of the run of mine ore by separation of a specific size fraction.
The recycled leachate experiments involved taking the leachate from an individual leaching experiment, adding additional acid to make it up to the original acid concentration and leaching a fresh batch of ore.
Acid consumption for the second leaching experiment was 450 kilograms of hydrogen sulphate per tonne of ore compared with the average acid consumption in previous lithium recoveries of more than 95% of 530 kilograms.
This represents a saving of 15% on average acid consumption or saving of 11% on the previous best result of 506 kilograms of acid per tonne of ore.
The company believes this is substantial given that recent studies on similar lithium deposits in the US identified sulphuric acid is a major cost component and that a combination of high lithium extraction rates with lower acid consumption results in a reduction of capital and operating costs.
Attrition scrubbing tests on a portion of the same sample demonstrated that the minus 10µm fraction of the attritioned material assayed 0.34% lithium and contained 78% of the lithium in about 50% of the weight.
The implication of this work is that most of the lithium is contained within 50% of the run of mine ore and a simply industry standard process could be used to reject a large proportion of the ore at an early stage of any process.
Additional attrition scrubbing tests and ore characterisation work is underway to understand this better and potentially achieve even better outcomes.