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Recovery of rare earth elements from nitrophosphoric acid solutions
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.ORCID iD: 0000-0002-3239-5188
2017 (English)In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 169, p. 253-262Article in journal (Refereed) Published
Abstract [en]

In the present study, the recovery of rare earth elements (REEs) from an apatite concentrate in the nitrophosphate process of fertilizer production has been studied. The apatite concentrate has been recovered from iron ore tailings in Sweden by flotation. In the first step, the apatite is digested in concentrated nitric acid, after which Ca(NO3)2.4H2O is separated by cooling crystallization. The solution is then neutralized using ammonia whereby the REEs precipitate mainly as phosphates (REEPO4.nH2O) and together with calcium as REEn Cam (PO4)(3n + 2m) / 3. In this work, the degree of rare earth coprecipitation during seeded cooling crystallization of Ca(NO3)2.4H2O has been studied. The solubility of calcium nitrate tetrahydrate (Ca(NO3)2.4H2O) in acidic nitrophosphoric acid solutions in the temperature range of − 2 °C to 20 °C has been determined. For the neutralization step, it is shown that the calcium concentration and the final pH play an important role in determining the concentration of REEs in the precipitate. It is found that reaching maximum recovery of REE with minimum simultaneous precipitation of calcium requires careful control of the final pH to about 1.8. It is further observed that the precipitation yield of REEs and iron is favored by a longer residence time and higher temperature. Finally, the effect of seeding with synthesized REE phosphate crystals as well as a mixture of REE and Ca phosphates on the precipitation rate and the composition of the precipitate was studied.

Place, publisher, year, edition, pages
Elsevier, 2017. Vol. 169, p. 253-262
Keywords [en]
Cooling crystallization, Nitrophosphate process, REE, Seeded precipitation, Selective precipitation, Apatite, Calcium, Cooling, Flotation, Iron ores, Metal recovery, Ore tailings, Ore treatment, Phosphate minerals, Phosphates, Rare earth elements, Rare earths, Recovery, Calcium nitrate tetra-hydrate, Concentrated nitric acid, Nitrophosphate, Rare earth elements (REEs), Simultaneous precipitation, Precipitation (chemical)
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-207347DOI: 10.1016/j.hydromet.2017.01.008ISI: 000401878200031Scopus ID: 2-s2.0-85011958720OAI: oai:DiVA.org:kth-207347DiVA, id: diva2:1097315
Funder
Swedish Foundation for Strategic Research , IRT 11-0026
Note

QC 20170522

Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2018-11-15Bibliographically approved
In thesis
1. Recovery of Rare Earth Elements from an Apatite Concentrate
Open this publication in new window or tab >>Recovery of Rare Earth Elements from an Apatite Concentrate
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Rare earth elements (REE) are a group of 17 elements including lanthanides, yttrium and scandium; which are found in a variety of classes of minerals worldwide. The criticality of the application, lack of high grade and economically feasible REE resources and a monopolistic supply situation has raised significant attention in recovery of these metals from low grade ores and waste materials. In this thesis, the recovery of REE from an apatite concentrate, containing 0.5 mass% of REE, within the nitrophosphate route of fertilizer production has been investigated. Most of the REE (≥ 95%) content can be recovered into a phosphate precipitate with almost 30 mass% REE. Different processes have been developed to convert the REE phosphate precipitate into a more soluble form to obtain a solution suitable for further REE purification and individual separation. It has been shown that after reprecipitation of the REE phosphate concentrate as REE sodium double sulphate and then transformation into a REE hydroxide concentrate, a solution containing 45g/L REE free of Ca, Fe and P can be obtained. The results suggest that the apatite waste after processing of iron ore have the potential to be a very important source for REE in Europe and that the economy is strongly supported by the simultaneous extraction of phosphorous.

The potential of using hollow fiber supported liquid membrane (HFSLM) extraction in individual and group separation of REE has been investigated. A hollow fiber supported liquid membrane plant in pilot scale has been operated according to the three main configurations: standard hollow fiber supported liquid membrane technology (HFSLM); hollow fiber renewal liquid membrane technology (HFRSLM) and emulsion pertraction technology (EPT). The standard HFSLM operation is more selective than HFRSLM and EPT, while higher metal transport rate is observed in EPT followed by HFRSLM and HFSLM. The HFRLM configuration helps to maintain the performance of the liquid membrane.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2018. p. 86
Series
TRITA-CBH-FOU ; 2018:49
Keywords
Rare earth elements, precipitation, nitrophosphate process, hollow fiber supported liquid membrane extraction
National Category
Other Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-239058 (URN)978-91-7873-034-6 (ISBN)
Public defence
2018-12-07, Kollegiesalen, Brinellvägen 8, KTH huset, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research , IRT 11-0026
Note

QC 20181116

Available from: 2018-11-16 Created: 2018-11-15 Last updated: 2018-11-16Bibliographically approved

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Alemrajabi, MahmoodRasmuson, Åke C.Korkmaz, KivancForsberg, Kerstin

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