Rare Earth Elements and Critical Minerals from Acid Mine Drainage

By Luanne McGovern

If you’ve been following the news from the 2022 West Virginia Legislative session, you know that recovery of Rare Earth Elements (REEs) from Acid Mine Drainage has been a hot topic.   In mid-February, a group from the WV Highlands Conservancy Board went to WVU to discuss their REE research program with Dr. Paul Ziemkiewicz, Director of the WV Water Research Institute.

(See January 2022 The Highland Voice article: “Something Useful from Acid Mine Drainage: Is that Possible?” by John McFerrin for background.)

Dr. Ziemkiewicz is a nationally recognized expert on Acid Mine Drainage (AMD) and has been investigating the recovery of Rare Earth Elements for several years.  In 2019, he and his team were awarded $5 million by the U.S. Department of Energy to scale up its successful Rare Earth Recovery Project, which will include building a facility at the acid mine drainage treatment plant near Mount Storm in Tucker County WV.

What are Rare Earth Elements?

Rare Earth Elements are a set of 17 heavy metals that are not really that “rare”.  They are actually quite plentiful in the Earth’s crust, but are not concentrated and are difficult to separate.  The elements have very similar chemical properties, but each has unique electronic and magnetic properties, and so can fill technology niches in today’s electronics.

How are REEs recovered from Acid Mine Drainage?

Getting from highly dilute concentrations of REEs in AMD to pure elements is a complicated multistep process.  The first step would occur at the mine water source, since the water is already being treated before discharge.

Step 1 – pH adjustment and Water Removal:

AMD usually has a pH of about 2.5, and contains a mixture of all types of metals, including iron, aluminum, silica, cobalt, zinc and the REEs.  The first step of the process would add lime and increase the pH to about 4.5, which would allow the iron, silica and aluminum to be removed.  The second step would increase the pH to about 8.5, which would allow the cobalt, zinc and REEs to be removed.  The majority of the water would be removed and then be discharged as usual from the facility.  The solids (sludge) would be recovered to become the feed source for the REE refinery. This sludge can contain between 500 and 1000 grams of REEs per ton of sludge.  

Step 2 – REE Refining:

The concentrated sludge would then be sent to a centralized REE refinery.  Using a multistep (and highly secretive!) process, the REEs would be extracted from the sludge through a variety of acid leaching, solvent extraction and liquid separation steps.  This is part of the technology that WVU will also be piloting at Mt. Storm.  The final concentrate is expected to be essentially 100% REEs.  There could also be an option to recover Critical Minerals, such as zinc and cobalt.

Step 3 – Elemental Separation

Finally, the various REEs must then be separated from each other.  Refiners use a variety of chemical, mechanical, electrical and magnetic processes to separate the various minerals into their pure forms.  These pure REEs are then used in hundreds of different applications in most high tech products.

As you can see, getting the REEs from acid mine drainage water to your smart phone is a long and complicated process.  Dr. Ziemkiewicz envisions that the Step 1 would be accomplished at individual mine sites.  For Step 2, the sludge would then be shipped to a centralized refinery – hopefully located within West Virginia.  The final concentrate would then be sold to refiners, who would produce the final elemental materials (Step 3).  Initial cost estimates for the centralized refinery are in the hundreds of millions of dollars, and would take many years to build and start up.

Given the high cost and long timeframes for development, the WV Legislature is looking at multiple tax incentives to drive this industry forward.  HB 4003 establishes that the value of all materials recovered from the AMD belong to the persons treating the water.  HB 4025 would grant a 5 year exemption from severance tax on all recovered materials.  Both of these bills have passed the House and are under consideration in the Senate.  HB 4657 would give tax credits to entities building REE facilities in the state.