الفهرس 
I.1. INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Leaching and recovery parameters controlling the releasing of rare
earth elements from Nusab El-Balgum altered alkaline granite rock are
studied and determined. The optimum conditions of batch leaching are
attained at 3 M of HCl concentration, 200 rpm stirring speed and 1/6
solid to liquid ratio for 180 min contact time at room temperature.
Under the optimized conditions, the ΣREEs leaching efficiency was
92.4%. The thermodynamic data showed positive values of both ΔH
and ΔS which indicates that the leaching process is indeed
endothermic and random while the obtained negative values of ΔG
indicate that REEs dissolution process is spontaneous in nature.
Three-liquid-phase system (Cyanex 272/PEG 2000/(NH4)2SO4–H2O)
is employed for rare earths separation from associated impurities in
the obtained leach liquor. The relevant factors controlling and
selective enrichment of those ions in aqueous salt phase are
investigated. The optimized conditions are occurred at pH 2, 3g of
PEG, and 1.6 M of (NH4)2SO4. Separation of REEs ions from bottom
aqueous phase after removal of impurities is achieved and precipitated
by adding oxalic acid.
Copy Right, IJAR, 2016,. All rights reserved.
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Introduction:-
Rare earth elements (REEs) have unique physicochemical properties that have led to their application in wide range
of high-value market sectors including phosphors, optical glass, lasers, advanced ceramics, capacitors, metal alloys,
critical military applications, nuclear and the manufacturing of high intensity magnets1,2. Since REEs have become
an indispensable part of modern life, their extraction procedures now hold huge importance3. Actually, the rare-earth
deposits are associated with of several rock types and in some mineral concentrate4-5. They occur in low
concentrations of few mg/kg in many rock formations and their major minerals, such as bastnaesite, monazite,
allanite, gadolinite and xenotime6. These minerals occur in concentrations of 5-10% in carbonatites formations, iron
ores and phosphate rocks7.
Numerous studies have been reported on the leaching of REEs using mineral acids and their salts solutions. The
choice of leaching agent depends on the selectivity in the separation of rare-earth elements, type of gangue minerals
in the ore and the type of the reagents to be used in the further extraction procedures8-14. In this context ionadsorption
clays are leached with concentrated inorganic salt solutions of monovalent cations. The physisorbed
REEs are relatively easily and selectively desorbed and substituted on the substrate by these ions and transferred into
Corresponding Author:- Mohamed F. Cheira.
Address:- Nuclear Materials Authority, P.O. Box 530 El Maadi, Cairo, Egypt.
ISSN: 2320-5407 Int. J. Adv. Res. 4(9), 787-801
788
solution as soluble sulfates or chlorides15. Ammonium chloride and ammonium nitrate were used as a mixed
leachate to treat weathered deposited rare earth ores16. Other researchers suggested magnesium sulfate as leaching
agent for ion-adsorption type rare earth ore to reduce or even eliminate ammonia-nitrogen emissions17,18. On the
other hand releasing of rare earth ions from a mineral concentrate containing minerals require severe conditions to
destroy their structure. Xue et al., reported that the hydrochloric acid leaching process of the activated bastnaesite
occurred at 90 ℃ leaching temperature and 20:1 liquid to solid ratio19. In fact, leaching ores by HCl are
environmentally beneficial for those containing bastnaesite.
Solvent extraction and ion-exchange techniques have been reported to produce high purity single rare earth element
solutions or compounds. In this context, several extractants have been suggested with various ligands20-29. Also,
commercial ion exchangers in the hydrogen, sodium and chloride forms that are available under the trade names of
Amberlite, Duolite, Dowex, Ionac, and Purolite are used for extraction of REEs. These techniques have the
advantage of allowing the recovery of the metallic ions, but they are expensive and sophisticated30-36.
Three-liquid-phase system (TLPS) is a process for simultaneous extraction and separation of multiple target
components even with slight differences in physicochemical properties. In a well-designed TLPS, multiphase
extraction and selective separation of different components respectively into three different liquid phases can be
achieved by only one-step of extraction37. TLPE is composed of an organic solvent-rich top phase, a polymer-rich
middle phase and a salt-rich bottom phase. According to the strategy developed by Sui et al., it is possible to
separate REEs in groups and also from undesirable ions by this approach38. They concluded that most of the rare
earths in their solutions remained in salt-rich bottom phase due to the formation of hydrophilic complexes between
them and complexing agents. On the basis of this data, it could be separate and recover ΣREEs in relatively pure
form by controlling variant parameters whereas the obtained leach liquor containing about 90% light rare earth ions.
The current work aimed to study the leaching and recovery parameters of total REEs from Nusab EI Balgum altered
alkaline granite rock sample. The leaching parameters included the type of leaching agents, the concentration of
hydrochloric acid, agitation time, solid/liquid ratio, stirring rate, grain particle size and leaching temperature are
studied. The leaching performance of total iron which is the primary impurity ion in the leachate is also investigated.
In addition, thermodynamic parameters of the leaching process are also determined. Recovery of total REEs from
the obtained leach liquor is carried out using the three-liquid-phase system. The effect of acidity, concentration of
ammonium sulfate and the suitable amount of polyethylene glycol are determined.
Materials and methods:-
Characteristic of working sample:-
The studied sample is obtained from Nusab EI Balgum area, in the central southwestern desert of Egypt. The area is
bounded by latitudes 23° 15/ to 23° 20/ N and longitudes 29° 15/ to 29° 20/ E. It covers about 40 km2 and forms the
northern part of Bir Safsaf area. It consists mainly of sandstone, volcanic rocks, altered granitic. The working
sample is firstly subjected to preparation through crushing, grinding and sieving followed by proper quartering, then
analyzed quantitatively after complete dissolution using the suitable techniques.
Reagents:-
The chemicals and reagents used in this work are of the analytical grade in all experiments, double-distilled water
was used for aqueous solutions preparation and dilution. The main chemicals used in this work are hydrochloric acid
37% obtained from Adwic, ascorbic acid from Sigma-Aldrich, formic acid from Prolabo and Arsenazo III from
BDH, England. Bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272, purity of 85 wt%) is supplied by Sigma,
polyethylene glycol (PEG) with average molecular weight of 2000 is purchased from Loba Chemie. The stock
solution of (NH4)2SO4 salt is prepared by dissolving an appropriate amount of (NH4)2SO4 in double distilled water,
ethylene diamine tetraacetic acid (EDTA) is supplied from Loba Chemie and 1,10- phenanthroline (phen) is
obtained from Sigma-Aldrich.
Analytical methods:-
The mineralogical analyses of working sample are assayed by X-ray Diffraction analysis (XRD), which is used to
determine bulk mineral assemblages based on the diffraction of X-rays interacting with a rock sample. The
quantitative analysis of the studied sample after its digestion is then carried out for the determination of the major
oxides and trace elements. The major oxides SiO2, Al2O3 and TiO2 have been spectrophotometrically analyzed using
Unicam UV2-100 UV/Vis spectrometer according to standard methods of analysis while Na and K oxides have
ISSN: 2320-5407 Int. J. Adv. Res. 4(9), 787-801