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Isolation of rare earth element phosphate precipitate in the nitrophosphate process for manufacturing of fertilizer
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.ORCID iD: 0000-0002-3239-5188
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
2016 (English)In: IMPC 2016 - 28th International Mineral Processing Congress, Canadian Institute of Mining, Metallurgy and Petroleum , 2016Conference 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
Canadian Institute of Mining, Metallurgy and Petroleum , 2016.
Keywords [en]
Apatite, Precipitation, REE, Selective dissolution, Ammonium hydroxide, Calcium carbide, Calcium phosphate, Concentration (process), Dissolution, Fertilizers, Flotation, Heterojunctions, Iron ores, Metal recovery, Nitric acid, Ore tailings, Ore treatment, Phosphates, Rare earth elements, Rare earths, Calcium-containing compounds, Chemical equilibriums, Concentrated nitric acid, Cooling crystallization, Fertilizer production, Optimum conditions, Partial dissolution, Precipitation (chemical)
National Category
Geochemistry
Identifiers
URN: urn:nbn:se:kth:diva-236893Scopus ID: 2-s2.0-85048364871ISBN: 9781926872292 (print)OAI: oai:DiVA.org:kth-236893DiVA, id: diva2:1270129
Conference
28th International Mineral Processing Congress, IMPC 2016, 11 September 2016 through 15 September 2016
Funder
Swedish Foundation for Strategic Research
Note

QC 20181212

Available from: 2018-12-12 Created: 2018-12-12 Last updated: 2018-12-12Bibliographically approved

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