New PhD on REE recovery from bauxite residue

On July 2^nd, 2018, Dženita Avdibegović obtained her PhD degree in Chemistry. She successfully defended her PhD thesis entitled ‘Recovery of rare earths from bauxite residue leachates by functionalised sorbents‘. (Leuven, 02/08/2018)

The research was supervised by Prof. Koen Binnemans (promotor) and Dr. Mercedes Regadio (co-promotor). Dr. Avdibegović obtained her degree in the framework of the European Training Network for Zero-Waste Valorisation of Bauxite Residue (REDMUD). A list of the peer-reviewed papers published in the framework of her PhD can be found below. The full text of the thesis will become available once all research results have been officially published in the peer-reviewed literature. Dr. Avdibegović will now continue her research career as a postdoc in the group of Prof. Koen Binnemans, where she will work on the separation of REE ions by magneto-chromatography.

Abstract

Bauxite residue, better known as red mud, is a waste product of the alumina industry, but with many unexploited values. The estimated inventory of bauxite residue in operating and closed alumina refineries reaches the value of several billion of tonnes. Stockpiling of huge amounts of residue can create environmental problems. Bauxite residue comprises iron, aluminium, titanium, sodium and even more interestingly, valuable rare-earth elements (REEs). Although a lot of research has been done on bauxite residue valorisation, to date there are no large-scale applications of bauxite residue yet. The REEs, and scandium in particular, are generally more enriched in residues originating from karst bauxites. Interestingly, bauxites found in the southern region of Europe belong to the group of karst bauxites. Europe currently has no operating REE mine, although these elements are getting an increasing role as materials for the transition to cleaner energy and the production of high-tech devices.

In this PhD thesis sorbents were synthesised and investigated for the recovery of REEs from bauxite residue leachates. The leachates can be prepared by direct leaching of bauxite residue with mineral acids, or as a processing step after recovery of other valuable metals. The leachates typically comprise low concentrations of REEs, whereas base elements like iron or aluminium are concentrated. Liquid-solid extraction is a suitable method for recovery of elements from dilute streams. This process requires sorbents selective for elements of interest. Supported ionic liquid phases (SILPs) and crystalline zirconium-phosphate (α-ZrP) were synthesised, characterised and examined for the REEs recovery and separation from other element present in bauxite residue leachates. Moreover, hybrid materials prepared by grafting of short n-alkyl chains (ethyl, n-propyl and n-butyl) to titanium(IV) phosphate functionalised mesoporous MCM-41 silica were tested for mutual separation of REEs.

Publications by Dženita Avdibegović in the framework of her PhD

1. Avdibegović D., Regadío M., Binnemans K. (2018). Efficient separation of rare earths recovered by a supported ionic liquid from bauxite residue leachate, RSC Advances, 8, 11886–11893.
2. Avdibegović , Regadío M., Rivera R.M., Onoughene G., Van Gerven T., Binnemans K., Purification of low concentration of rare earths from high concentration impurities in leach liquor of bauxite residue slag by a supported ionic liquid phase. In: Y. Pontikes (ed) Proceedings of the 2^nd International Bauxite Residue Valorisation and Best Practices Conference. 7-10 May 2018, Athens, Greece, 381-386.
3. Avdibegović D., Regadío M., Binnemans K. (2017). Recovery of scandium(III) from diluted aqueous solutions by a supported ionic liquid phase (SILP). RSC Advances, 7, 49664-49674.
4. Zhang W., Avdibegović, D., Koivula R., Hatanpaa T., Hietala S., Regadío M., Binnemans K., Harjula R. (2017). Titanium alkylphosphate functionalised mesoporous silica for enhanced uptake of rare-earth ions. Journal of Materials Chemistry A, 5(45), 23805-23814. Joint first author with Wenzhong Zhang.
5. Avdibegović, D., Yagmurlu, B., Dittrich, C., Regadío, M., Friedrich, B., Binnemans, B., Combined multi-step precipitation and supported ionic liquid phase chromatography for the separation of rare earths from the base elements in bauxite residue leachates. Manuscript under revision. Joint first author with Bengi Yagmurlu.
6. Avdibegović, D., Zhang, W., Xu, J., Regadío, M., Koivula, R., Binnemans, K. Selective ion-exchange separation of Sc(III) over Fe(III) by crystalline α-zirconium phosphate platelets from bauxite residue leachates. Manuscript under preparation. Joint first author with Wenzhong Zhang.