\u00a9 iStock\/Andrzej Rostek<\/figcaption><\/figure>\nPrevious AMD treatment processes<\/h3>\n The researchers obtained acid mine drainage and associated sludge material representing the Lower Kittanning coal bed and evaluated the recovery of multiple critical minerals. A new purification process based on a previous AMD treatment process was then designed to recover high-grade aluminium, rare earth elements, cobalt, and manganese products from the sludge<\/p>\n
\u201cThe extraction of REEs and CMs directly from AMD eliminates the need for the dissolution of sludge and associated costs of reagents and processing, resulting in more sustainable waste disposal practices with low cost,\u201d said Mohammad Rezaee, Assistant Professor of Mining Engineering at Penn State and co-author on the study.<\/p>\n
\u201cWe have demonstrated that we are able to turn these waste streams, which have been of environmental concerns for decades, into valuable resources, so this is a win-win for the environment, the commonwealth, and the nation.\u201d<\/p>\n
Usually, AMD is treated by adding lime or other chemicals to raise the pH to 7. However, the researchers changed this in their new process.<\/p>\n
\u201cTypically, AMD is neutralised through the addition of various alkaline chemicals,\u201d said Rezaee. \u201cAs the pH of the AMD increases during the treatment process, metals precipitate as metal hydroxides or other complexes.\u201d<\/p>\n
The new AMD system to extract rare earth element oxides<\/h3>\n In the new system developed by the researchers, the pH is still raised to 7, but this is done in stages.<\/p>\n
\u201cInstead of adding sodium hydroxide, calcium hydroxide, or lime all at once to raise the pH, we are raising it in stages,\u201d said Pisupati. \u201cThe advantage of this method is that it allows certain minerals to precipitate out at different pH levels. If we add in our base all at once and bring the pH to 7, all these things will precipitate at the same time. Then we would need to go back and separate them.\u201d<\/p>\n
The pH was raised to the level needed for iron to precipitate, and then to the pH needed for aluminium to precipitate. After this precipitation, rare earths and then recovered through carbonate precipitation.<\/p>\n
\u201cOur challenge was that we could not get 100% of the iron and aluminium removed; there was a little bit of residue in the REE concentration,\u201d said Pisupati. \u201cEven if you have only 1% of aluminium content in the mixture it dominates, and your quality of rare earths will not be as pure. This was addressed in the new purification process.\u201d<\/p>\n
The precipitates that were removed are then put back through the cycle in the purification process to remove iron, aluminium, and other residues.<\/p>\n
\u201cIn the purification process, we go through the cycle all over again, going back to a pH of 3 or 3.5 and starting all over,\u201d said Pisupati. \u201cWe are getting rid of the other residues slowly, maybe two times or three times through the cycle, to increase the REE purity. In our previous research, we were at about 17% to 18% grade, so this is a significant accomplishment.\u201d<\/p>\n
Purity of the recovered minerals<\/h3>\n For the target elements, recoveries of more than 99% were achieved with the design of a recycling load. In the previous AMD process, the cobalt and manganese precipitates had a concentration of 0.85% and 23%, respectively. The new purification process increased their concentrations to 1.3% and 43%.<\/p>\n","protected":false},"excerpt":{"rendered":"
Researchers have developed a new purification process that extracts mixed rare earth element oxides from acid mine drainage.<\/p>\n","protected":false},"author":18,"featured_media":27640,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[24502],"tags":[24335,24308],"acf":[],"yoast_head":"\n
New process developed to extract rare earth element oxides<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n \n \n \n \n \n\t \n\t \n\t \n