April 29-May 4, 2018
Phosphogypsum (PG) is an industrial waste of phosphoric acid (H3PO4) production from phosphate ore by sulphuric acid (H2SO4) digestion, commonly known as the “wet acid” process. Phosphate rock often contains some valuable rare earth elements (REE) and it is well-established that from 70% to 85% of REE originally present in the phosphate rock end up in the PG, with an average REE content of ~0.4 wt. % [1-4]. PG is considered to be an attractive secondary resource of REE. However, processes available currently for REE recovery are often very expensive, sometimes impractical, and in other cases are characterised by highly variable and low overall REE recoveries due to the complexity of the REE association within the PG structure . Mintek developed a novel hydrothermal process which modifies the microstructure of PG and release entrapped REE phases as shown in Figure 1 for subsequent leaching/recovery. Modification of the PG structure resulted in an increase of REE recovery from 5% (m/m) to 80% (m/m). This process was verified on various PG samples and carries a potential to unlock substantial REE value associated with the enormous size of PG stockpiles globally.
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Volha Yahorava, Eugene Lakay, and Wilma Clark, "Hydrothermal Pre-Treatment Process of Phosphogypsum for Enhanced Rare Earths Recovery" in "Beneficiation of Phosphates VIII", Dr. Patrick Zhang, Florida Industrial and Phosphate Research Institute, USA Professor Jan Miller, University of Utah, USA Professor Laurindo Leal Filho, Vale Institute of Technology (ITV), Brazil Marius Porteus, Foskor-Mining Division, South Africa Professor Neil Snyders, Stellenbosch University, South Africa Mr. Ewan Wingate, WorleyParsons Services Pty Ltd., Australia Prof. Guven Akdogan, Stellenbosch University, South Africa Eds, ECI Symposium Series, (2018). https://dc.engconfintl.org/phosphates_viii/35