Rare Earth Elements (REEs) comprising 15 Lanthanides, Yttrium, and Scandium are some of the cornerstones of many strategic sectors like defence, renewable energy, and electronics.
With ever-increasing demand for these critical elements, coupled with limited primary sources, it becomes pivotal to extract these elements from available secondary resources like industrial wastes. There are different industrial wastes, namely, Phosphogypsum, Fly-ash, and wastes of alloy industries, which carry REEs and have the potential to fill a part of the country's REE demand.
The major challenge in extracting REEs from these resources is the low concentration of REEs in them. For instance, Phosphogypsum, a waste by-product of the phosphoric acid industries, carries a mere 200-400 ppm of REEs.
PG holds great potential as a source of REEs like Yttrium, Neodymium, Cerium, and Lanthanum, along with minor quantities of other REEs.
We have performed preliminary and advanced hydrometallurgical investigations to develop flowsheets for the extraction of REEs from Phosphogypsum through direct and indirect means. We have explored the leaching efficiency of different mineral acids like sulphuric acid, hydrochloric acid, and nitric acid in extracting REEs.
Keeping an eye on the growing environmental concerns, we have also explored potential organic lixiviants like methanesulphonic acid to extract these critical elements from Phosphogypsum. Apart from the direct leaching of Phosphogypsum with these acids, we have also explored the potential of indirect methods.
| Method | Temperature (°C) | Acid Concentration (M) | Duration (min) | Solid-to-Liquid Ratio | Leaching Efficiency (%) |
|---|---|---|---|---|---|
| Direct | 60 | 4 | 60 | 1/8 | 70 |
| Indirect | Room Temp. (27.2) | 2 | 30 | 1/8 | 70 |
We have developed a first-of-its-kind leaching process that works at room temperature with a significant reduction in cost and environment along with efficiency. A patent is filed for the same. We are in talks with a major company to take it further for commercialization.
With the success of REE extraction of Phosphogypsum, we are encouraged to work on other industrial wastes to extract REEs and make the country self-sustainable.
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