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Isolation of Rare Earth Element Phosphate Precipitates in the Nitrophosphate Process for Manufacturing of Fertilizer
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.ORCID iD: 0000-0002-3239-5188
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
2016 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In the present study, the recovery of rare earth elements (REE) in the nitrophosphate process of fertilizer production is investigated. The apatite has been recovered from iron ore tailings by flotation. After digestion of apatite in concentrated nitric acid, Ca(NO3)2.4H2O is first separated by cooling crystallization and then the REEs are recovered by precipitation. Optimum conditions in these steps have been determined in a previous study. The precipitate mainly consists of CaHPO4.2H2O and REE phosphates. In the present study, selective dissolution and re-precipitation have been studied in order to obtain a precipitate that is more concentrated in REEs. The precipitate was selectively dissolved in nitric and phosphoric acid at different acidities (pH 6 to 0) with the liquid /solid ratio of 100 mL/g. It is shown that most of the CaHPO4.2H2O and other calcium containing compounds will be dissolved at pH 2 while the REE phosphates are not dissolved above a pH of approximately 2. Thus, by partial dissolution of the REE precipitate at pH 2.5 most of the solid calcium phosphates will be dissolved and the remaining solid phase, which is more concentrated in REEs, can be filtered off as a fairly concentrated REE solid mass and the liquor can be recycled back to recover more P nutrients. Alternatively, the REE enriched precipitate was dissolved completely in nitric acid and re-precipitated again by addition of ammonium hydroxide to pH 1.2. A chemical equilibrium software, MEDUSA (Puigdomenech, 2013) has been used to evaluate the experimental results and to estimate the optimum conditions for selectively dissolving the precipitate.

Place, publisher, year, edition, pages
2016.
Keywords [en]
Apatite; Precipitation; REE; Selective dissolution
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-237438Scopus ID: 2-s2.0-85048364871OAI: oai:DiVA.org:kth-237438DiVA, id: diva2:1259111
Conference
XXVIII International Mineral Processing Congress (IMPC), rare earth element symposium, Québec City, 11- 15 September
Note

QC 20181217

Available from: 2018-10-27 Created: 2018-10-27 Last updated: 2018-12-17Bibliographically approved

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Rasmuson, Åke C.

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