Orion Minerals Limited advised that it has commenced a series of field trials for the treatment of mine water at the Prieska Copper-Zinc Mine (PCZM) in South Africa's Northern Cape Province, using a proprietary electrolytic technology to produce saleable products. The process has the potential to extract valuable products such as calcium and magnesium, for agri-nutrient use from water pumped out of the underground mine at Prieska. In addition, other products with potential for by- product sales in the chemicals industry will also be extracted by the process.

The trials have commenced as Orion prepares to commence dewatering of the underground mine and to implement other key elements of its Early Production Plan as it advances the PCZM towards production. The water treatment trials are being undertaken in collaboration with Free Radical Process Design (FRPD), a South Africa-based technology company which has developed an innovative and proprietary process and equipment for the continuous extraction of metals and other valuable minerals from water using electrowinning via a rotating cathode (Electrosoftner). The Electrosoftner has the potential to extract iron hydroxide, hydrogen, calcium, magnesium and base metals such as nickel, zinc and copper from contaminated mine waters.

The ability to harvest the agri-nutrients at the Prieska Copper-Zinc Project (Prieska Project) ­ which is located in a region where renewable energy is abundant and where irrigation agriculture is a core industry ­ has the potential to offer important host-community development opportunities. This will advance Orion's vision of establishing a `green' footprint for the Prieska Project with broad stakeholder benefits as part of its objective to have a world-class ESG framework to support its operations. The commencement of the field trials follows the success of laboratory scale test work, where water samples from PCZM were analysed and were passed through an Electrosoftner demonstration unit, producing precipitates of iron hydroxide, calcium hydroxide/carbonate and magnesium hydroxide while concentrating sodium hydroxide that can be bled off as a liquid from PCZM mine water.

The extensive underground workings at Prieska hold approximately 9 million cubic metres of water, which has accumulated since the mine was closed by Anglovaal in 1991. While the quality of the mine water is relatively benign, with pHs ranging between 6.6 to 7.1 (neutral pH is 7.4), and total dissolved solids measured in the shaft water range between 6,000 and 11,000 mg/l, some water treatment is required if the water is to be considered for off-site discharge and subsequent agricultural or potable applications. The dewatering setup which is being implemented, consists of pump sets and reticulation that will extract mine water from underground workings at a pumping rate that will build up from 120m3/hr to 500m3/hr.

Once on the surface, some of the water will be treated by reverse osmosis (RO) while the balance will be treated by electrolysis. Some brine water will be retained in evaporation dams. The treated waters will be used for irrigation projects, planned to benefit local host communities. Dewatering is planned to occur over a three-and-a-half-year period, during which time, mining is planned to commence in those parts of the Prieska deposit above the water level so that copper and zinc concentrate production can commence within less than three years, as scheduled in the original project development plan (BFS-20 Plan).

FRPD has patented technology for the continuous electrowinning of selected minerals from mineralised leachate using a rotating cathode (RotowinnerTM). The RotowinnerTM consists of a rotating cathode, submerged in pregnant leachate with a scraper arrangement to remove the precipitation of minerals on the cathode. The scraped material is discharged into a collection launder and the spent leacheate is collected to be recycled in the leach circuit.

A mobile demonstration scale plant has been constructed that has been successfully used to produce base metals on a continuous basis. The RotowinnerTM process offers the advantage over conventional electrowinning set-ups of: Being a continuous production process; Having a lower energy requirement than standard electrowinning; With built-in cathode stripping offering a simpler, safer and more cost-effective operation; Having no lifting equipment requirements during operation; Having smaller inter-electrode distances; Completely enclosed construction; Reduced acid mist generation; Modular set-up for versatility and easy scale-up or down; Robust design; Wider and more efficient operating ranges; and Significantly reduced capital cost for establishment. Following from laboratory-scale test work and water quality assessments of the Prieska Mine water, it is anticipated that the RotowinnerTM will be able to produce agricultural use water while extracting calcium, magnesium and iron as products, as well as generating hydrogen, oxygen and chlorine gases and with a sodium hydroxide solution residue.

This would result in the whole water treatment stream having a valuable use. Field trials are expected to continue for six months. Subject to the success of these trials, implementation of a production-scale RotowinnerTM assembly will be undertaken.

The current dewatering infrastructure layout has made provision for incorporating the RotowinnerTM water treatment at the end of the trial period.