Scientists have developed a breakthrough method to turn one of the mining industry’s most toxic byproducts into a valuable chemical used to treat drinking water, offering a rare win-win for communities, ecosystems, and industry.
Researchers from Heriot-Watt University and the University of South Africa have found a way to convert acid mine drainage (AMD) into ferric chloride, a widely used coagulant for water purification.
AMD is among the most destructive legacies of mining. It is highly acidic, metal-rich, and capable of contaminating rivers, groundwater, and soil for decades. Its corrosive nature can also damage bridges, pipes, and other infrastructure.
South Africa alone discharges nearly 400 million liters of AMD every day from active and abandoned coal and gold mines, creating a massive environmental and public health burden.
Toxic waste transformed
The research team extracted ferric iron (Fe(III)) from AMD and chemically converted it into ferric chloride.
In lab tests, the recovered ferric chloride removed over 99% of pollutants like aluminum, iron, and chromium from river water. The treated water met the country’s drinking water standards.
Professor Vhahangwele Masindi from the University of South Africa said the approach could turn a major hazard into an economic opportunity.
“Active and derelict coal and gold mines in South Africa discharge close to 400 million litres of acid mine drainage per day, and this demonstrates the viability of using this wastewater stream as a secondary mine for valuable minerals. This approach supports the circular economy by turning waste into a product with real value,” he said.
To extract iron, the team used magnesium oxide nanoparticles produced from locally sourced magnesite. These nanoparticles precipitated iron from AMD, which was then reacted with hydrochloric acid to produce ferric chloride.
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Water from waste
Dr Spyros Foteinis from Heriot-Watt University said the results show how mining regions worldwide could benefit.
“We’re demonstrating that even highly contaminated mine water can be cleaned up. This could be a low-energy and low-carbon practical solution to a problem that blights communities around the world and has lasting health, ecological and economic impact.”
The researchers now plan to pilot the technology in rural and peri-urban communities in South Africa and beyond, particularly in regions facing acute water scarcity.
They believe the method can scale to industrial levels and offer a sustainable alternative for countries dealing with legacy mining pollution.
Mamile Belina Mahlohla from the University of South Africa and Magalies Water said the technology could help address future water challenges.
“Climate change is exacerbating water scarcity pressures and creates new challenges that the water sector needs to address sustainably. “
“This technology can be part of a portfolio approach. We’re also working on different methods of recovering nutrients and clean water from municipal wastewater.”
The findings were presented at the International Mine Water Association (IMWA) 2025 conference.
NOTE – This article was originally published in Intresting Engineering and can be viewed here
