الفهرس 
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Abstract
Factors controlling the extraction of rare earth elements from leach
liquors of Abu Rushied Lamprophyre dykes, South Eastern Desert, Egypt, are
investigated. At ambient temperature, the optimum leaching conditions are 3
M of HCl, 250 rpm stirring speed, and 1/4 S/L ratio for 180 minutes.
Under the optimized conditions, the ΣREEs leaching efficiency was 94.2%.
The positive values of both ΔH° and ΔS° indicate the endothermic and random
nature of REEs leaching while the negative ΔG° value indicates spontaneous
REEs dissolution process.
The impregnation conditions of polyvinyl chloride impregnated by
cetylpyridinium bromide (CPB) and sodium Diethyl-dithiocarbamate (DdTC)
are suggested as new adsorbent to collect RE ions from leach liquor of the
studied geological sample then characterized by XRD, SEM, TGA, EDX, and
FTIR. The obtained results proved that RE ions are adsorbed on the prepared
CPB/PVC and DdTC/PVC adsorbents more effectively than PVC only
without impregnation.
The optimum adsorption conditions are attained at pH 5.5 for 60
minutes at room temperature. The REEs maximum loading capacities of REEs
on PVC, CPB/PVC, and DdTC/PVC are 65.12, 182.6, and 156.6 mg/g,
respectively.
The adsorption of RE ions onto the three adsorbents obeyed well in both
pseudo-second-order kinetic and Langmuir isotherm models. Furthermore,
the thermodynamic parameters have been examined, and it is found that the
adsorption of RE ions on PVC is non-spontaneous. In contrast, the adsorption
of RE ions on both CPB/PVC and DdTC/PVC adsorbents is spontaneous. Also,
the adsorption process is exothermic for the three adsorbents. Releasing of RE
ions from the loaded adsorbents is investigated. The optimum RE ions
desorption conditions from the loaded adsorbents are 1 M of HCl, and 1:60 S:L
ratio, for 60 minutes at ambient temperature.
Finally, three-liquid-phase partition behaviors were scrutinized to conceive
a possible extraction approach to extract Light, intermediate, and heavy rare-earth
as groups. The impacts of pH, polymer amount, complexing agents, and salt
concentration on the three-phase partitioning of three groups of rare-earth ions
were scrutinized. The optimum partition conditions occur at pH 2.5 and 1 M of
(NH4)2SO4. Moreover, adding DTPA by molar ratio 1:1 also enhances partition.
Light rare earth ions are partitioned into the bottom salt-rich phase, but middle
rare earth ions are separated in the polymer middle layer, and heavy rare earth
ions are extracted in the top organic phase.
from these successfully obtained results, we can conclude that the
suggested procedure for recovering rare earth elements is realized and can be
applied to another variety of rock compositions. A simple flow sheet
describing the whole process is presented.