Selective Sc Recovery from Rare Earths in Nitric Acid Medium by Extraction Chromatography

Abstract

Chemical compounds containing scandium (Sc) are widely applied to various fields such as catalysts, alloys, lamps and etc. Sc is found in mineral ore, and it is necessary to develop efficient Sc separation and recovery technology for the industrial applications.(HONTA) extractant has been shown to be promising for selective Sc extraction. In this study, applicability of the extraction chromatography technology using HONTA impregnated adsorbent for the selective Sc recovery from other rare earth elements (REs) was experimentally evaluated through batch-wise adsorption/elution studies and column separation experiments. Batch-wise experiments showed that distribution coefficient of Sc onto the HONTA/SiO 2 -P adsorbent was far larger than those of other REs at acidity region with 0.001 < [HNO 3 ] < 4 mol dm -3 and that the adsorbed Sc was efficiently eluted into 1 M H 2 SO 4 solution. Appropriate experimental conditions for the column separation experiment were proposed based on those results, and performance of the flow-sheet was examined for laboratory scale column system. Only Sc in 4 mol dm -3 HNO 3 solution was adsorbed into a packed column with the adsorbent while other REs were discharged from the column with the feed solution, and then loaded Sc was properly eluted into 1 M H 2 SO 4 solution. Purity of the Sc product solution obtained by the column separation experiment depended on Sc recovery ratio, and about 99.9 % purity was achieved with 97 % recovery ratio. The residual Sc was eluted from the column with other REs and did not remain inside the column, therefore repeated used of the column was shown to be possible. This process was shown to be promising for selective Sc recovery from mixture of REs in nitric acid. therefore the yield of scandium is not so large due to difficulty in separation from other REs. Effective and appropriate Sc extraction and purification procedures from mineral ore, which is main source of Sc, is essential for its commercial use. So far, several fundamental studies on recovery and purification ( ) 31

Overview of development program for engineering scale extraction chromatography MA(III) recovery system

“…Sr(II) and Mo(IV) as well as RE(III) should be separated from MA(III) by the 2nd column. Hexaoctyl-nitrilotriacetamide (HONTA) impregnated adsorbents are used for the 2nd columns owing to its selectivity for MA(III) (Sasaki et al, 2013) and excellent adsorption/desorption performance of the HONTA impregnated adsorbent (Takeuchi et al, 2019;Watanabe et al, 2018b). Our preliminary experiments showed that selective MA(III) recovery is possible even though several modifications have to be made in the process flow for more efficient separation (Akuzawa et al, 2022).…”