Australia’s EcoMag is working on a project to recycle waste-water streams, which are known as bitterns, to extract hydrated magnesium carbonate or HMC.
At present, the focus is on the streams generated by Dampier Salt, a sea salt producer mostly owned by Rio Tinto in the Pilbara region.
Magnesium is the third most abundant element dissolved in seawater. The first two, sodium and chlorine, are removed as sodium chloride by producers like Dampier.
In an interview with MINING.com, EcoMag’s Executive Director of Communications Walter Munro explained that HMC is a high-purity, high-value magnesium product that currently fetches circa $1,250/tonne.
According to Munro, the advantage of recovering it from salty water rather than mining it is the possibility of obtaining purity levels of 99% plus, as opposed to 85-95% typically from ore.
“Also, our base product is the ideal starting point for producing oxides and esters with specific chemical and physical characteristics that are expensive -often prohibitively so- to achieve when starting from a mined ore,” he said.
Who buys this?
EcoMag is planning on selling magnesium compounds directly to large-scale industrial, agricultural, environmental and mining users, and via international distributors to smaller users.
In the mining industry, magnesium oxide is used specifically for hydrometallurgy processes as an alkali to precipitate metals from acid streams. In other words, the compound aids in higher recovery of valuable metals from ore extraction such as cobalt, nickel and copper from acid leach solutions.
In agriculture, on the other hand, Mg compounds are used in fertilisers and animal feed supplements. They are also used for human consumption products such as health supplements, pain relief and acidity regulation medication, and as a stabiliser in bread-making and other food processing.
Munro explained that there are also environmental uses such as an acid stream neutralizer and to precipitate heavy metals in wastewater treatment plants, and technology uses, as magnesium oxide is one of the additives employed to chemically strengthen the toughened, ultrathin glass used in smartphones, slates, laptops and most devices with LCD screens.
A $130-million plant
To go ahead with the plan of becoming a major supplier of magnesium compounds, EcoMag is proposing the development of a $130-million processing facility in Karratha, Western Australia. The plant is expected to initially produce 80,000 tonnes of HMC per year.
Munro said that he forecasts expansion to take place shortly after the facility becomes operative because recently completed modeling studies revealed that the volume of bitterns available for processing in the area is much larger than initially considered and could potentially support production levels eight times higher.
But before expansion plans can be considered, EcoMag needs to complete a regulatory approval process for its initial plant. The process involves providing bitterns dispersal modelling to the Western Australia Department of Water and Environmental Regulation and incorporate 45 years of data for evaporation rates, rainfall patterns, tides, and extreme weather events such as the cyclones that occasionally strike the area.
As this is ongoing, Munro and the EcoMag team are providing samples to distributors that look for magnesium compounds with minimal impurities and specific particle sizes.
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