{"649297":{"#nid":"649297","#data":{"type":"event","title":"PhD Defense by Laura M. Stoy","body":[{"value":"\u003Cp\u003E\u003Cbr \/\u003E\r\nRECOVERY OF RARE EARTH ELEMENTS FROM COAL FLY ASH USING IONIC LIQUIDS\u003Cbr \/\u003E\r\nLaura M. Stoy\u003Cbr \/\u003E\r\nDr. Ching-Hua Huang\u003Cbr \/\u003E\r\nDr. Susan Burns, Dr. Sotira Yiacoumi, Dr. Yuanzhi Tang, Dr. Arthur Ragauskas\u003Cbr \/\u003E\r\nAugust 19, 2021, 1:00 pm - 4:00 pm Eastern\u003Cbr \/\u003E\r\nVirtual- Blue Jeans link to be provided\u003Cbr \/\u003E\r\nRare earth elements (REEs), the 15 lanthanides and Sc and Y, have played an invaluable role in the progress of clean energy technology\u003Cbr \/\u003E\r\nand high-tech manufacturing in past decades. Their high demand and global scarcity have led to disruptions in supply, exacerbated by the\u003Cbr \/\u003E\r\nfact that there are no adequate replacements. Thus, it is crucial to develop alternative sources to secure a steady supply of REEs. Coal fly ash\u003Cbr \/\u003E\r\n(CFA), a byproduct of burning coal for electricity, may be one such source. Conventional REE-CFA recovery methods are energy and\u003Cbr \/\u003E\r\nmaterial intensive and leach elements indiscriminately, generating impure mixtures of REEs. Ionic liquids (ILs) may be one solution, but to\u003Cbr \/\u003E\r\ndate, they have not been applied to CFA.\u003Cbr \/\u003E\r\nThis dissertation focuses on the IL betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]) for preferential extraction of REEs from\u003Cbr \/\u003E\r\ndifferent CFAs. Efficient extraction relies on [Hbet][Tf2N]\u0026#39;s thermomorphic behavior with water: upon heating, water and the IL form a\u003Cbr \/\u003E\r\nsingle liquid phase, and REEs are leached from CFA via a proton-exchange mechanism. Upon cooling, the water and IL separate, and\u003Cbr \/\u003E\r\nleached elements partition between the IL and aqueous (AQ) phases. REEs were preferentially extracted over bulk elements from CFAs into\u003Cbr \/\u003E\r\nthe IL phase then recovered in a subsequent mild acid stripping step, regenerating the IL. Two optimizations, alkaline pretreatment and\u003Cbr \/\u003E\r\nadding supplement betaine, significantly improved REE leaching efficiency and separation between REEs and bulk elements. Significantly,\u003Cbr \/\u003E\r\nthis method consistently exhibits a particularly high extraction efficiency for scandium.\u003Cbr \/\u003E\r\nThe IL extraction process yields a mildly acidic REE-rich solution contaminated with Fe. To address this, three strategies for limiting Fe\u003Cbr \/\u003E\r\ncoextraction into the IL phase were investigated: magnetic separation, alternative salts, and ascorbic acid reduction. The latter two methods\u003Cbr \/\u003E\r\nproved successful and should be used to generate an REE-rich acidic solution with very low concentrations of Fe.\u003Cbr \/\u003E\r\nTo gain a better understanding of CFA leaching behavior with [Hbet][Tf2N], eighteen additional elements were studied (29 total). It was\u003Cbr \/\u003E\r\nfound that in the IL phase, bulk elements were found in low concentrations, trace elements were not found, and of the actinides, Th was\u003Cbr \/\u003E\r\nextracted into the IL phase and U was not leached at all. Other important optimizations were also studied, including pH, temperature, and\u003Cbr \/\u003E\r\nduration of leaching. The process is also compared to several published CFA solid extraction methods and CFA leacheate separation methods\u003Cbr \/\u003E\r\nto place this dissertation in context with existing literature. Finally, a number of process sustainability improvements are recommended,\u003Cbr \/\u003E\r\nincluding the use of microwave heating, water and IL recovery strategies, and beneficial uses of residual solids.\u003Cbr \/\u003E\r\nFinally, two other ILs were studied along with [Hbet][Tf2N] to investigate the effect of IL\u0026#39;s cation functional group modifications. The two\u003Cbr \/\u003E\r\nILs possess the same anion [Tf2N], but one with a less acidic cation having an alcohol group, choline [Chol], and one with a more acidic\u003Cbr \/\u003E\r\ncation having an alkyl sulfonic acid group, trimethylammoniumethane hydrogen sulfate ([N111C2OSO3H]), in comparison with [Hbet], which\u003Cbr \/\u003E\r\nhas a carboxyl group. [Chol][Tf2N] was broadly unsuccessful at leaching almost all elements from all CFA samples tested. [N111C2OSO3H]\u003Cbr \/\u003E\r\n[Tf2N] was more successful, achieving greater or comparable leaching efficiencies but was not able to separate REEs from bulk and trace\u003Cbr \/\u003E\r\nconstituents.\u003Cbr \/\u003E\r\nOverall, the research outcome of this dissertation filled several knowledge gaps in REE recovery. The method presented is novel and is\u003Cbr \/\u003E\r\namong the first to demonstrate direct application of an IL to solid CFA for efficient recovery of REEs. The recyclability of IL and mild\u003Cbr \/\u003E\r\nextraction conditions offer significant advantages for environmental sustainability. Altogether, this thesis builds a foundation for new\u003Cbr \/\u003E\r\nIL-based strategies for future extractions from CFA and other REE-rich wastes.\u003C\/p\u003E\r\n","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":"","field_summary_sentence":[{"value":"RECOVERY OF RARE EARTH ELEMENTS FROM COAL FLY ASH USING IONIC LIQUIDS"}],"uid":"27707","created_gmt":"2021-08-05 19:31:36","changed_gmt":"2021-08-06 13:44:44","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2021-08-19T14:00:00-04:00","event_time_end":"2021-08-19T17:00:00-04:00","event_time_end_last":"2021-08-19T17:00:00-04:00","gmt_time_start":"2021-08-19 18:00:00","gmt_time_end":"2021-08-19 21:00:00","gmt_time_end_last":"2021-08-19 21:00:00","rrule":null,"timezone":"America\/New_York"},"extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78761","name":"Faculty\/Staff"},{"id":"78771","name":"Public"},{"id":"174045","name":"Graduate students"},{"id":"78751","name":"Undergraduate students"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}