Impact Minerals (ASX:IPT) Lake Hope update highlights CRC P progress on membranes and potash pathways

Impact Minerals has provided a project update on its 80% owned Lake Hope High Purity Alumina project in Western Australia, reporting technical progress during the first 12 months of a A$2.87M Cooperative Research Centre programme focused on integrating membrane technology into the company’s patented 3 stage HPA process.

The work is being carried out with CPC Engineering and the Mineral Recovery Research Centre at Edith Cowan University, and is directed at membrane applications across water management, mineral recovery, acid recovery and waste management within the Lake Hope flowsheet.

Highlights

• Technical progress reported in the first 12 months of the A$2.87M CRC P programme applying membrane technology to Impact’s patented 3 stage HPA process
• Membrane crystallisation assessed for recovering sulphate of potash crystals as a byproduct from Stage 1, with high purity SOP greater than 94% achieved to date
• High water recovery obtained from SOP brine, generating high purity water suitable for reuse in the process
• Pathway identified for magnesium potash, with magnesium captured during ore washing and selectively reintroduced into potash crystallisation to produce higher value fertiliser products
• Potential breakthrough iron removal technology emerging from Stage 2 hydrochloric acid circuit testwork, offering a potential low cost method for key impurity control
• New potential standalone pathway identified for large scale potash and acid production, independent of the HPA flowsheet, that could lead to an additional mining project at Lake Hope and surrounding lakes

The update restates the company’s patented metallurgical process as a straightforward three stage sequence.

Stage 1 is an alkaline leach that yields high purity potash as a valuable liquid byproduct, Stage 2 is a hydrochloric acid leach of the solid residue from Stage 1 which produces aluminium chloro hexahydrate, and Stage 3 is subsequent calcination of aluminium chloro hexahydrate to produce HPA.

The company’s diagram of the flowsheet also identifies five membrane insertion points covering water recycling and reuse, recovery of specific minerals or elements, acid sparging and precursor production, acid recovery and solid waste management.

Stage 1 potash byproduct recovery is described as the main focus to date. Impact reports that membrane crystallisation has been successfully demonstrated for direct SOP recovery, with K2SO4 crystals achieving a purity of greater than 94%.

It also reports development of a microfiltration ultrafiltration nanofiltration pretreatment membrane system removing greater than 99% of particles in the SOP brine, delivering higher quality brine feed for crystallisation, reagent recycling and water reuse loops.

High water recovery from SOP brine has been achieved, with the recovered water described as high purity and suitable for reuse as process water or discharge as waste.

The company also outlines a pathway to magnesium potash products.

Testwork is described as showing that a membrane can selectively capture magnesium during the initial ore washing phase, with magnesium then selectively reintroduced into SOP crystallisation to produce magnesium enriched potash, with the pathway being researched further.

Alongside Stage 1 work, the CRC P programme includes Stage 2 hydrochloric acid recycling and rejuvenation, where a potential breakthrough method for low cost iron impurity removal from hydrochloric acid has been identified, referred to as the Direct Iron Extraction method.

The update also notes work underway on alternatives to hydrochloric acid leaching of the Stage 1 residue, and continued work on integration with the HiPurA process owned by Alluminous Pty Ltd in which Impact holds 50%.

While pointing to pathways directed at operating costs, water efficiency and fertiliser byproducts, Impact Minerals Managing Director Dr Mike Jones said

“the first year of CRC P work has achieved notable technical progress, significantly boosting the value of the Lake Hope project.”

The update includes additional discussion of potash market context and Lake Hope potential.

It states that Australia currently imports virtually all of its MOP and SOP for a market estimated at about 500,000 tpa, and that under the Lake Hope Pre Feasibility Study, for 10,000 tpa of HPA production, estimated SOP production as a byproduct is about 20,000 tpa.

It also states that a different metallurgical flowsheet from the HPA process has been identified that could potentially allow for direct production of potash from clays in Lake Hope and surrounding lakes, without evaporation ponds, with an acid byproduct also generated, and that initial testwork results for the new process are expected by early February.