A passive water treatment system has been demonstrated to remediate coal mine drainage while also capturing yttrium, neodymium and other rare Earth elements (REEs) for reuse in the manufacture of computers, batteries and other electronic products.

The trap-extract-precipitate (TEP) process developed at The Ohio State University uses the alkalinity and filtering capacity of stabilized flue gas desulfurization material or water treatment plant sludge to remediate coal mine drainage waters and extract critical elements of industrial value. In laboratory-scale experiments conducted with samples from rivers across Ohio, Pennsylvania and West Virginia, the gravity-powered seepage of coal mine drainage through the sludge materials was observed to facilitate trapping and extraction of the REEs as well as common pollutants.

The TEP process yields REE feedstock while neutralizing coal mine drainage. Source: Marcos M. Miranda et al.

While the alkaline treatment materials effectively neutralize coal drainage in a process that delivers environmental benefits relative to conventional active treatment schemes, the cost of the passive TEP treatment scheme is a couple orders of magnitude above the market price for REEs. The researchers expect that centralizing extraction facilities could reduce total and levelized costs through economies of scale and increase the amount of REEs recovered per unit of coal mine drainage, flue gas desulfurization material or wastewater treatment plant sludge.

The research is published in Environmental Engineering Science.