الفهرس 
INTRODUCTION AND LITERATURE REVIEW (1 - 41)Only 14 pages are availabe for public view
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Abstract
The sample under study was collected from Gabal El-Faliq which lies in
the South Eastern Desert, Egypt. It was considered mainly as pegmatite
mineralization. This sample was firstly subjected to physical upgrading then
chemical treatment. Gabal El-Faliq area is considered as one of the promising
occurrences for Zr beside the associated economic metal values e.g. REEs,
Nb, Ti,….etc. The main target of the present work is the studying of the
mineralogical and chemical specification of G. El-Faliq concentrate sample as
well as studying the suitable processing method for this concentrate sample to
recover Zr, Nb and REEs which have several economic, technological and
nuclear applications.
For this purpose, a technological representative concentrate sample
from G. El-Faliq area was properly prepared. The chemical analysis of this
concentrate sample proved the presence of 33.6%w/w ZrO2, 2% w/w Nb2O5
and 4.8% w/w RE2O3 as the elements of interest. The mineralogical analysis of
this sample using XRD technique emphasized that, it consists mainly of zircon
(ZrSiO4) associated with fergusonite [(Y,Er)(Nb,Ta,Ti)O4, Xenotime
(Y,Er)PO4 and Samarskite (Y,Er)(Nb,Ta)2O6. Two different and subsequent
leaching techniques were performed to conduct the optimum conditions that
realize the highest dissolution efficiencies for all the metals of interest. KOH
fusion followed by distilled H2O leaching technique was applied upon the
concentrate sample for selective dissolution of Nb dissolution efficiency
97.9% away from Zr and REEs as Nb form soluble potassium niobates while
Zr and REEs form insoluble hydrous oxides. The applied optimum leaching
conditions were concentrate sample/KOH mass ratio of 1/2, 2.5h fusion time
at 550oC fusion temperature. On the other hand, HCl acid leaching was
applied upon the concentrate residue after the alkaline fusion. The optimum
acidic leaching conditions were 25% HCl acid concentration, S/L ratio of 1/3
with stirring time for 0.5 h at leaching temperature of 80oC for dissolving
99.9% of Zr and 99.7% of REEs.
Two different leach liquors were prepared to perform the suitable
extraction technique for the recovery of the metals of interest. These leach
liquors were alkaline solution for the recovery of Nb and chloride leach liquor
for Zr and REEs.
Firstly, prepared alkaline leach liquor was obtained by processing 200
g of the present concentrate sample and assays 1.36 g/L of Nb, 0.03 g/L of
Ta, 0.25 g/L of Fe, 11.76 g/L of Si and its pH value higher than 12. Due to the
high contents of SiO2 in the prepared alkaline leach liquor, it was first treated
with conc. H2SO4 for adjusting the pH value of the leach liquor to pH value 10
as almost SiO2 was precipitated as SiO2 gel with small amounts of Nb (0.95%).
After separation and washing the precipitate of SiO2 gel, the filtrate contains
Nb and the remains of SiO2 was subjected for further acidification to
hydrolyze and precipitate of Nb. Almost complete precipitation of Nb
(99.8%) was attained at pH 8.5, while its purity was low and only 55.3 % with
the interfering impurities of Si, Fe, K, Y. So, further purification was needed
using solvent extraction aliquat 336S in xylene. The optimum conditions 5%
Aliquat 336S concentration, pH 3.5, contact time 10 min and Aqueous
/Organic ratio 1:1. Co-extraction of both of Nb and Fe with their maximum
extraction efficiencies 97.9 and 93.8% respectively was concluded so, 0.7M
H2SO4 acid concentration was first applied for the selective stripping of
almost parts of Fe (90.3%) from the loaded organic solvent with minimal
amount of Nb (only 8.2%) at contact time 5 min and A/O ratio 1/1. This was
followed by stripping of Nb by using aqueous solution of HNO3. The
maximum value of stripping of Nb (99.1%) was reached by applying the
optimum conditions 0.8 M HNO3 acid concentration, 6 min contact time and A/O ratio 1:1. The strip nitrate solution rich in Nb was treated with NH4OH
solution where Nb was completely precipitated at pH 7.5. After filtration and
washing, the obtained Nb hydroxide cake was ignited at 650oC for 1h and
identified using XRD analysis.
Secondary, with respect to Zr and REEs recovery from the prepared
chloride leach liquor containing 28.5 g/L of Zr, 5.4 g/L of REEs, 4.2 g/L of Si
and has a pH lower than 1. Direct precipitation technique was used for the
extraction of both Zr and REEs. selective precipitation of Zr with 99.9%
precipitation efficiency was obtained after adjusting the pH value of the
prepared alkali leach liquor via 10% Na2S to be 3 for 25 min at 80oC. The
resulted zirconium sulfide which was filtered, washed and dryness was ignited
at 850oC for 2h and identified using SEM-EDX analysis. The effluent solution
free from Zr was subjected to REEs recovery via their precipitation as
RE2(C2O4)3 by using 10% H2C2O4. Almost complete precipitation of REEs
was attained at pH 1.1 and after stirring for 45 min. with precipitation
efficiency reached 99.8%
Finally, flow sheet for processing of G. El-Faliq concentrate pegmatite
was designed for the recovery of Zr, Nb beside REEs Fig (38).