Production of a rare earths concentrate after phosphogypsum treatment with dietary NaCl and Na2CO3 solutions

Due to their unique physicochemical properties, rare earth elements (REEs) are increasingly becoming significant in developing new technologies. Their extraction from ores and industrial wastes has attracted the interest of several researchers. Phosphogypsum (PG) is one of many industrial wastes considered as an attractive source of such elements. Since rare earths are present in small quantities in PG, the different steps of their concentration in this waste remain essential before any attempt of extraction. In the present work, after determining the content of REEs and their distribution in the phosphogypsum sample, a total rare earth enrichment of about 84% was achieved in the final solid. The method consists of a washing step with 25 g/L sodium chloride solution followed by leaching the residue with sodium carbonate solution at 90 °C for 1 h. A new result was discovered while examining the recrystallized Na2CO3 from the carbonated filtrate (at low temperature) with photoluminescence technique. This analysis shows the characteristic emissions of Ce3+ and Eu3+ at 374 nm and 555–612 nm respectively after selective excitations. The presence of REEs both in the final residue and in the solid recrystallized from the filtrate suggests that such elements are linked differently in the PG sample.