Supervisors info:
Χριστίνα Στουραΐτη, Αναπληρώτρια Καθηγήτρια ΕΚΠΑ (επιβλέπουσα)
Αριάδνη Αργυράκη, Καθηγήτρια ΕΚΠΑ
Χαράλαμπος Βασιλάτος, Επίκουρος Καθηγητής ΕΚΠΑ
Summary:
The object of the present dissertation is the examination of the distribution of REE (Rare Earth Elements) in the grain size fractions and magnetic fractions of the black sands of Nea Peramos – Loutra Eleftheron, Kavala, Northern Greece and the effect of the mineralogical composition in the beneficiation process. The tests were carried out on a composite sample of coastal black sand from Nea Peramos-Loutra Eleftheron, Kavala prefecture. The process of pre-concentration of REE minerals was carried by applying grain size separation and then selection of the REE-rich fractions and finally the application of the Wet High Intensity Magnetic Separation at different magnetic field intensities of the different fractions. The study area is known from previous studies for its natural enrichment in the light REE-mineral allanite.
In placer sands Rare Earth Element (REE)-bearing minerals are usually concentrated in the heavy mineral fraction. The mineral phases that have been observed in the sands of the sampling area during the macroscopic and microscopic observation are quartz, feldspars (sanidine, microcline, albite), mica (biotite, muscovite and paragonite), titanite, epidote, hornblende, apatite and ilmenite. The mineral phases that host the largest percentage of Rare Earths include allanite, monazite, and xenotime. Allanite, due to its increased and detectable presence in relation to other REE minerals, is the aim of the present study, in terms of its behavior during the Liquid Magnetic Separation process. Quantification of valuable minerals in the ore body is of key importance for ore deposit characterization and optimization of process operations. Kavala’s black sands have been intensively studied because of their increased percentage in heavy REE-bearing minerals, which is due to natural gravity enrichment by the erosion-weathering processes. According to studies of geological occurrence of the black sands of Kavala, it’s deposit potential is about 485 million tonnes.
The efficiency of the test method is evaluated by semi-quantitative XRD analysis and ICP-MS chemical analysis. Preliminary WHIMS results from the composite sample A-mixed at several magnetic field intensities (0.24T, 0.48T, 0.96T and 2.40T) showed that the highest allanite concentration is achieved even at 0.48 T and reaches 8 wt.% (in the particle size analysis) as shown in the XRD semi-quantitative analysis. The same magnetic field conditions were then applied to the more REE-rich particle-size fractions: -0.500 +0.425 mm, -0.425 +0.355 mm, -0.355 +300 mm and -0.300 mm. Particle size analysis showed the highest TREE concentration in fractions of -0.423+0.355 mm and -0.355+0.300 mm, that reach 0.37 wt.% and 0.48 wt.% respectively. In the magnetic separates of the particle fraction -0.355+0.300 mm, the distribution of TREE corresponds to the values of 0.95 wt.%, 1.26 wt.%, 1.39 wt% and 1.21 wt.% for the four magnetic field intensities (0.24T, 0.48T, 0.96T and 2.40T respectively).
