A bench-scale lithium hydroxide test-work program has been completed by SGS Canada with results comparing favourably with current battery quality market specifications.
Lithium hydroxide was produced from spodumene concentrate at SGS facilities in Lakefield, Ontario, Canada, from core samples taken from the Piedmont Lithium Project.
The company has a market cap of approximately A$105.6 million and shares have been as much as 13% higher to A$0.115 cents intra-day.
President and chief executive officer Keith D Phillips said: “The successful production of battery-quality lithium hydroxide from ore samples taken from the company’s drill core represents a major milestone for Piedmont Lithium.”
Low impurity profile
He said: “The Carolina Tin-Spodumene Belt is renowned for its pure spodumene mineralogy, and we are very pleased that this test-work program confirms the low-impurity profile of our 100%-owned mineral resource.”
SGS’ program results demonstrate the ability of Piedmont to concentrate and produce battery-quality lithium hydroxide via an ‘ore-to-hydroxide’ conversion route.
Consistent with design
This is consistent with the chemical plant process design in Piedmont’s recently completed lithium chemical plant pre-feasibility study.
"Phillips added: With Austin Devaney now on board as our VP - Sales & Marketing, we look forward to sharing these results with prospective customers in the automotive, battery and cathode businesses, as we advance in our goal of becoming a leading American lithium hydroxide producer.”
To support lithium conversion test-work, Piedmont prepared a spodumene concentrate sample using dense medium and flotation processing.
A test-work program was designed to run small-scale optimisation tests and bulk tests to carry the concentrate sample through to battery-quality lithium hydroxide.
A block flow diagram of the LiOH conversion test-work program.
The bench-scale test-work program was a multi-step effort that includes extraction of lithium from spodumene, several stages of impurity removal and a sequence of crystallisation steps.
Step 1 – Calcination
To extra lithium from spodumene concentrate the spodumene must be converted from alpha-phase to leachable beta- and gamma- phase at high temperature.
In the program to spodumene concentrate sample was calcined in a pilot kiln at around 1050oC for around one hour to achieve this conversion.
Beta-spodumene product after calcination (left) and after milling (right).
Step 2 – Acid roasting
The beta-spodumene was then roasted in a pilot-scale kiln by mixing it with sulphuric acid and heating to 250oC for roughly 30 minutes to complete the roasting process.
Acid roasted calcined spodumene (left) and residual solids after water leach (right).
Step 3 – Water leach
Lithium was then extracted from the roasted product by a water leach process. The acid roasted concentrate was mixed with hot water at about 60oC in a reactor for 60 minutes to extract lithium into solution.
Steps 1-3 of the program are critical in the overall recovery of lithium from spodumene concentrate.
The resulting solution after water leach contains predominantly lithium sulphate with other impurities and is referred to as pregnant leach solution (PLS).
Step 4 – Impurity removal
Impurity removal from the PLS is a multi-step process including several stages of pH adjustment, filtration and ion exchange top remove metals from lithium solution prior to crystallisation.
Step 5 – Causticisation
Causticisation involved the addition of sodium hydroxide to the PLS following impurity removal. Excess sodium hydroxide was added to the lithium sulphate solution to complete this step.
Step 6 – Sodium sulphate removal
Sodium sulphate was removed from the causticized PLS by lowering the temperature to about -5oC for an extended time. This reaction produced sodium sulphate crystals, called Glauber’s salt.
The Glauber’s salt crystals were filtered out of the solution and washed.
The PLS was then rechilled to further reduce the sodium sulphate through a second Glauber’s salt crystallisation and filtration step.
At the conclusion of step 6, some sodium sulphate remained in the PLS after Glauber’s salt crystallisation.
Step 7 – First stage crystallisation
First stage lithium hydroxide crystals were prepared by evaporating the PLS to a sodium sulphate concentrate of 18% (weight/weight basis) in two batches.
The resultant crystals were first filtered and then washed using hot distilled water.
Step 8 – Second stage crystallisation
The first stage crystals were then re-dissolved to a target concentration of 128 g/L LiOH. This near-saturated solution was then recrystallised by evaporation.
The resulting second stage crystals were filtered and washed with distilled water. The crystals were then filtered and dried.
Additional second stage lithium hydroxide crystals were prepared from filtrate and wash solutions from the initial second stage crystal production.
Final filtered second stage LiOH crystals.