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{"title":"Efficient and Selective Recovery of Trace Scandiumnby Inorganic Titanium Phosphate Ion-Exchangers from Leachates of WastenBauxite Residue","authors":"Wenzhong Zhang (609797), Risto Koivula (1699330), Elmo Wiikinkoski (3808159), Junhua Xu (3808156), Sami Hietala (1495597), Jukka Lehto (3808153), Risto Harjula (1699333)","doi":"10.1021/acssuschemeng.6b02870.s001","DOIUrl":"https://doi.org/10.1021/acssuschemeng.6b02870.s001","url":null,"abstract":"Bauxitenresidue (BR) is an inevitable industrial waste generated through thenclassic Bayer extraction of alumina from bauxite minerals. It containsnrelatively significant amount of valuable rare earth elements, includingnscandium, and therefore, we explored the suitability of trace scandiumnrecovery from BR acid leachate by titanium phosphate (TiP) ion exchangers.nThree kinds of TiP materials (amorphous TiP, α-TiP, and γ-TiP)nwere synthesized through fluorine-free precursors and characterizednby chemical analysis, X-ray diffraction (XRD), field emission scanningnelectron microscopy (FE-SEM), Fourier transform infrared (FTIR), ultraviolet/visiblen(UV/vis) diffuse reflectance spectrometry, <sup>31</sup>P magic anglenspinning (MAS) nuclear magnetic resonance (NMR), thermogravimetricnanalysis (TGA), and potentiometric titration. The Sc<sup>3+</sup> exchangencapacities were determined as 1.74, 0.55, and 0.22 mequiv g<sup>–1</sup> for amorphous, α-, and γ-TiP, respectively. Competitionnof major elements (Fe, Al, Ca) in BR leachate with Sc uptake werenstudied in batch experiments using binary equimolar mixtures, andnthe separation factors of Sc/Fe<sup>2+</sup>, Sc/Al, and Sc/Ca reachednmagnitudes of 10–1000 on amorphous TiP. The high Sc<sup>3+</sup>selectivity by amorphous TiP was suspected to be the matching ofnTi<sup>4+</sup> lattice radius with Sc<sup>3+</sup> ionic radius (bothn0.745 Å). Finally, the separation of trace scandium from thensimulated BR leachate solution was demonstrated on an amorphous TiPncolumn. The interference of Fe<sup>3+</sup> has been partially resolvednby on-column reduction using sodium sulphite. The optimized finalneluate contained only Sc, Fe, and Al. The concentration ratio of Sc/Fencan be increased by a factor of 8.8 and Sc/Al by 265 through a singlencycle of chromatographic separation with an Sc recovery rate of 91.1%.","PeriodicalId":523774,"journal":{"name":"Figshare","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147921753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}