Abstract
Rare earth elements (REEs) are defined as lanthanides with Y and Sc. Rare earth occurrences including the REE-bearing phases and their distributions, measured by rare earth oxides (REOs), in the streams of processing a phosphate ore were determined by using MLA, the mineral liberation analysis and EPMA, the electron probe microanalysis. The process includes an apatite ore beneficiation by flotation and further processing of the beneficiation concentrate with sulfuric acid. Twenty-six, sixty-two and twelve percent of the total REOs (TREO) contents from the ore end up in the products of beneficiation tailings, phosphogypsum (PG) and phosphoric acid, respectively. Apatite, allanite, monazite and pyrochlore are identified as REE-bearing minerals in the beneficiation process. In the beneficiation tailings, the REEs are mainly distributed in monazite (10.3% TREO), apatite (5.9% TREO), allanite (5.4% TREO) and pyrochlore (4.3% TREO). Gypsum, monazite, apatite and other REE-bearing phases were found to host REEs in the PG and the REEs distributions are 44.9% TREO in gypsum, 15.8% TREO in monazite, 0.6% TREO in apatite and 0.6% TREO in other REE-bearing phases. Perspectives on the efficient recovery of REEs from the beneficiation tailings and the PG are discussed.
Highlights
The grade of apatite ores can vary from 4% to 20% phosphorus pentoxide (P2 O5 )
The occurrences of Rare earth elements (REEs), including REE-bearing phases and REEs distribution, in the streams of processing a phosphate rock were studied on the basis of mineralogical analyses using mineral liberation analyser (MLA), the mineral liberation analysis and EPMA, the electron probe microanalysis of the apatite ore, the flotation concentrate and the PG
For determining the chemical compositions of REE-bearing phases in the samples, and of certain minerals that cannot be unequivocally identified by the semi-quantitative approach of MLA, the electron probe microanalysis (EPMA) was performed by the wavelength dispersive technique using a Cameca SX100 instrument at the Geological Survey of Finland in Espoo
Summary
The grade of apatite ores can vary from 4% to 20% phosphorus pentoxide (P2 O5 ). A study by Zhang et al (2018) [3] indicated that REEs during a phosphate ore processing are distributed approximately 40% in waste clay, 10% in amine tails, 38% in PG and 12% in phosphoric acid but how the REEs occur in these products was not investigated. The occurrences of REEs, including REE-bearing phases and REEs distribution, in the streams of processing a phosphate rock were studied on the basis of mineralogical analyses using MLA, the mineral liberation analysis and EPMA, the electron probe microanalysis of the apatite ore, the flotation concentrate and the PG. Potential technological pathways for REE recovery from the beneficiation tailings and the PG are discussed
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