Cleaner production of rare earth elements from phosphorus-bearing sulfuric acid solution of vein deposit monazite

Abstract

In the present study, the recovery of rare earth elements (REEs; viz. cerium, lanthanum, and yttrium) from sulfate leach liquor of vein deposit Korean monazite has been investigated using the solvo-chemical techniques. The dissolved phosphorus (373 mg L-1), which may significantly affect the products' purity, was selectively removed using the benzyl-di-methyl amine (BDMA). The logarithmic distribution vs. BDMA concentration along with spectral analysis of the organic phases revealed the formation of extracted species (3[BDMA]center dot[H3PO4]) over bar. The quantitative removal of phosphorus was achieved in three stages of counter-current extraction (CCE) under the organic-to-aqueous (O:A) ratio of 1.0:1.5, leaving REEs' into the raffinate. Subsequently, Cyanex 923 was employed to selectively extract cerium(IV) from P-depleted solution under the varying parameters of extractant and sulfuric acid concentration, temperature, and O:A ratio. The quantitative extraction of cerium (similar to 99% from 864 mg L-1 feed concentration) showing exothermic nature was achieved at an O:A of 1:2 under three stages of CCE while using 0.15 mg L-1 extractant into organic phase and 1.12 mol L-1 H2SO4 into aqueous phase. Further, the experimental results and spectral analysis of the organic phases could reveal that cerium solvates as <([Ce(SO4)(2)]center dot 2[Cyanex 923]center dot[HSO4-])over bar> species. Cerium was successfully stripped from loaded organic by contacting with a higher concentration of H2SO4 solution (>= 4.0 mol L-1) in presence of 0.1 mol L-1 H2O2, yielding an enriched high-purity solution of 2.54 g L-1 cerium. Lanthanum and yttrium were recovered from the Ce-depleted raffinate by co-precipitation with oxalic acid, forming a mixture of C6La2O12 center dot 10H(2)O and C6Y2O12 center dot 4H(2)O. The study approaches a cleaner production of high-purity REEs for clean energy programs under Sustainable Development Goals.