RE: Rare Earth Extraction from phosphoric acid is game changing.20 Apr 2023 05:49
If you are writing about typical REE content of 0.4%, then read this article about typical content -
K. Kovler, in Toxicity of Building Materials, 2012
Annual world production of phosphogypsum is estimated to be ~300 Mt (Yang et al., 2009). This by-product is contaminated by various impurities, both chemical and radioactive, and is usually stockpiled within special areas. The problem of contaminated phosphogypsum has already become an international ecological problem. For example, a huge amount of phospho-gypsum has accumulated in Florida (more than 1 billion (!) tons), in Europe (where the contaminated phosphogypsum is discharged into the River Rhine close to the North Sea), in Canada, Morocco, Togo, India, China, Korea, Israel, Jordan, Syria, Russia, and other parts of the world.
The building materials industry seems to be the largest among all the industries which is able to reprocess the greatest amount of this industrial by-product and benefit man. However, because of the contamination, only 15% of world phosphogypsum production is recycled as building products and asset ******er in the manufacture of Portland cement (a small amount is recycled as agricultural fertilizer or for soil stabilization amendment), while the remaining 85% is disposed of without any treatment (Tayibi et al., 2009). Disposed phosphogypsum is usually dumped in large stockpiles, occupying considerable land areas and causing serious environmental damage due to both chemical and radioactive contamination.
Typical concentrations of radium (226Ra) in phosphogypsum are 2003000 Bq kg- 1(US Environmental Protection Agency, 1990). They are similar to those in phosphate ores. Digestion with sulfuric acid causes the selective separation and concentration of naturally occurring radium (226Ra), uranium (238U) and thorium (232Th): about 80% of 226Ra is concentrated in phospho-gypsum, while nearly 86% of 238U and 70% of 232Th end up in phosphoric acid (Tayibi et al., 2009). In other words, most of the 226Ra follows phospho-gypsum, which is responsible for its enhanced radioactivity, and most of the 238U and 232Th remain in the phosphoric acid product.
In addition to radionuclides, phosphogypsum contains some trace contaminants which may pose health and environmental hazards, such as ****nic, lead, cadmium, chromium, fluorine, zinc, antimony, and copper (US Environmental Protection Agency, 1990). These trace elements may be leached from phosphogypsum, as radionuclides, migrate to the nearby surface and ground water, and cause fluorescence on the surface of building elements.
Sign In
Follow the stocks
