Acid Mine Drainage to Ferric Chloride for Water Purification Utilizing Magnesium Oxide Nanoparticles: South Africa Project Extracts Ferric Iron (Fe(III)) from AMD and Chemically Converts to Ferric Chloride

       Interesting Engineering reports that scientists from Heriot-Watt University and the University of South Africa were able to convert acid mine drainage (AMD) to ferric chloride, a widely used coagulant for water purification. This could become a successful circular economy, turning waste into value.

     AMD is toxic and among the worst environmental problems of both coal and mineral mining. South Africa discharges 400 million liters of AMD per day from coal and gold mines.

“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.”

     Magnesium oxide nanoparticles produced from locally sourced magnesite were used to extract the iron, precipitating it out. It was then reacted with hydrochloric acid to form ferric chloride. The availability of local magnesite for the process aids the economics of extraction.

     The paper was presented at the International Mine Water Conference in July 2025. According to one of the paper's authors, Dr. Spyros Foteinis:

“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 AMD basically becomes a feedstock for the production of ferric chloride (FeCl3). The production process requires calcination via heating the Fe(III)-rich sludge at 1200 °C in a furnace. A reaction chamber and agitation are also employed. The calcination step improves FeCl3 yields.

“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.”

     The equation for removal efficiency is shown below, followed by a chemical table of the raw mine water.

Where, C-initial and C-final represent initial concentration (level) and final concentration (level), respectively.

     The effects of dosage, mixing speed, and contact time were evaluated and are shown below.

     The AMD and the river water parameters were measured with the following equipment:

“…multi-parameter probe (Hach Company HD40D) was used to measure the pH and electrical conductivity (EC). Turbidity was recorded using a tungsten lamp turbidimeter (Hach Company TL2350). Metal and non-metal fractions were determined using inductively coupled plasma mass spectrometry (ICP-MS) (Thermo Scientific XSERIES 2 ICP-MS, coupled to ASX-520 auto sampler) and inductively coupled plasma – optical emission spectrometry (ICP-OES) (Agilent Technologies 5110 ICP-OES coupled with SPS 4 auto sampler), as required based in their concentration.”

 

    

 

References:

 

Toxic mine wastewater turned into water treatment chemical removing 99% pollutants. Neetika Walter, Interesting Engineering. December 3, 2025. Toxic mine wastewater turned into water treatment chemical removing 99% pollutants

Recovery of Poly-Cationic Metal Sulfate from Acid Mine Drainage and its Beneficiation as a Coagulant for Water Treatment. Mamile Belina Mahlohla, Vhahangwele Masindi, Memory Tekere, and Spyros Foteinis. International Mine Water Association (IMWA) 2025 Conference Proceedings. Pgs. 592-597. IMWA 2025_Papers COMBINED.indb