AMD from coal mining is a significant environmental problem. When pyrite rock, which contains iron sulfide, comes into contact with water and air, it oxidises, creating sulfuric acid. The acid can then break down the surrounding rock releasing heavy metals into the water.
Researchers at Penn State University have developed a way to extract up to 90 percent of critical Elements, such as Aluminium, and 85 percent of rare earth elements present in the contaminated water. Other methods can extract up to 70 percent of rare earth elements. This approach incorporates CO2 mineralisation to achieve a higher level of recovery.
While this approach does not negate the need to treat AMD, nor does AMD cease to be a significant challenge for coal mining, it does provide a way to extract some value from the contaminated water.