الفهرس 
Aim of the workOnly 14 pages are availabe for public view
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Abstract
Several studies related to the exploration of sandy dolostone ore at
Gabal Allouga, southwestern Sinai, Egypt indicated that the presence of some
valuable metals in the host rock as a result of mineralization. It mainly includes
U, REEs, V, Cu…..etc. Development of the methods required for leaching and
recovery in addition of studying the kinetics of these procedures is of great
important. Thereby, the present work is directed towards the selective leaching
and recovery of U, REEs, V and Cu species from a proper collected ore sample
due to their useful industrial applications.
This work comprises three chapters; the first one includes the literature
survey reported for the extractive metallurgical processes of U, REEs, V and
Cu ore materials. Also, the kinetics leaching studies have been briefly
reviewed. The second chapter deals with the experimental work including the
optimum leaching, extraction and recovery procedures as well as the chemicals
and apparatus used during the course of work. The third chapter involves the
results and discussions of the obtained data. It also includes the kinetic leaching
of U and Cu. Finally, a workable flow sheet comprises the all steps involving
these processes are presented.
To realize the objectives of this work a representative sample from
sandy dolostone at Gabal Allouga, Southwestern Sinai was collected and which
was found to assay 0.15% U, 1.2% Cu, 0.15% REEs and 0.06% V. The X-ray
diffraction analysis revealed to the presence of Ankerite
[Ca(Fe,Mg,Mn)(CO3)2], Azurite [Cu3(CO3)2(OH)2 ], Quartz [SiO4], Malachite
(Cu2CO3(OH)2), Chalcocite (Cu2S), Hematite (Fe2O3) , and Hematitized pyrite
minerals. As a matter of fact, the presence of such high carbonate content about
41% has been behind the choice of carbonate system leaching of uranium and
copper in order to avoid the excessive consumption of sulfuric acid in classical
leaching procedures. To optimize alkaline processing for the recovery of both
metal values several series of leaching experiments have first been performed.
All experiments were run on roasted and un- roasted (raw ore material).
The relevant leaching factors of the roasted dolostone (at 5400C)
optimized at 100 g/L of 3:1 mixed Na2CO3 / (NH4)H CO3 for 90 minutes at 60ºC in a solid liquid ratio of 1:3 from this study it has been revealed 94%U,
and 95% Cu leaching efficiency have been realized.
In case of un-roasted dolostone material the relevant leaching
parameters have thus been optimized at 150 g/L of 3:1 mixed Na2CO3 /
(NH4)HCO3 for 180 minutes at 80ºC in a solid liquid ratio of 1:5 from this
study it has been revealed 93.75%U, and 97% Cu leaching efficiency have
been realized.
Under the optimum conditions, it was possible to realize a dissolution
efficiency of about 95 and 97% for Cu and uranium achieved 94 and 93.75 %
for roasted and un – roasted raw sample respectively. The leaching process for
un-roasted sample has been preferred for economic point of view.
The leaching kinetics of the dissolved uranium and copper of the studied
sample using mixed carbonate solution showed that the leaching rate of
uranium and copper is controlled by diffusion through the ‘‘product’’ layer. As
a matter of fact, the leaching rate of both set experiments followed the kinetic
model 1 – 2/3(X) – (1-X)2/3 = kt with an apparent activation energy of 27.37 for
Cu and 27 kJ/mole for U.
To recovery of the dissolved copper and uranium metal values a proper
carbonate leach liquor has been prepared at optimum conditions. Ion exchange
procedure was suggested for recovery of U and direct precipitation for Cu.
Amberlite IRA 400 resin was used for adsorption and separation of uranium
from carbonate leach liquor and the adsorption were optimized at pH of 9.5 and
a contact time of about 30 min equivalent to a flow rate of about 0.3 ml / min..
The total U adsorption efficiency was 94.2 %. The obtained equilibrium data
were found to be satisfactory fitted with Langmuir isotherm. A maximummetal
uptake of 58.8 mg U / g was observed at the obtained optimum
conditions. The pseudo second order kinetic model was found to best fit the
experimental results of uranium adsorption. The effect of temperature data on
uranium adsorption by Amberlite IRA 400 showed that the enthalpy change is -
77.08 kJ/mol indicating its exothermic nature.
Uranium was then eluted from the resin by 1 M NaCl with 0.25M Na2CO3
using a contact time of 15min. The elution efficiency of 97 % has been
realized. Uranium from the collected eluate was precipitated at a pH of about using 40 % NH4OH solution in the form of ammonium diuranate. from the
uranium effluent liquor, blue copper hydroxide crystals have been obtained by
adjusting its pH to 5.5 using proper dilute hydrochloric acid.
After the recovery of U and Cu, from the study raw material, the dried
residue was then subjected to another two successive recovery procedures for
V and REEs. These remaining two metal values which were left behind in the
spent residue were found to assay 1575 and 649 ppm for REEs and V
respectively. So, the present work was then shifted to study the recovery of
both V and REEs metal values from the spent residual material. These involved
V recovery by alkaline leaching followed by ammonium sulfate leaching
procedures for REEs. from the later a procedure for separating V from the
accompanying REEs can be achieved by breaking down the study spent ore
residue by using NaOH at the optimum conditions of spent ore residue /
NaOH ratio: 1/3, 3 h. roasting time and 600 °C roasting temperature. The
roasted cake was then leached with hot distilled water to obtain the dissolved
vanadate ions. Under these condition, the dissolution efficiency of the
vanadium attained 97% V. The solution containing vanadium (0.629 g/l) was
then directed to the ion exchange unit which consists of a column of 100 cm in
height and 0.7cm in diameter packed with 65ml of wet settled resin (wsr)
Amberlite IRA743 in its hydroxide form. The applied flow rate was 2.5 ml/min.
The amount of loaded vanadium upon the resin was realizing high loading
efficiency of 92.25%. The loaded vanadium was then eluted from the resin
using 4% H2SO4 acid at flow rate of 1.5 ml/min. Vanadium rich solution was
adjusted to pH 2.5 with NH4OH solution and then oxidized by the addition of
0.25g KClO3. Complete precipitation of vanadium (98%) as a red cake (V2O5)
was obtained at 75 0C after 2h stirring time.
For separating 97% of REEs from the spent ore residue free from V, this
can be achieved by using (NH4)2SO4 300 g/L concentration, 90 min. stirring
time within S/L: 1/5 at room Temp. The obtained liquor was then subjected to
precipitation using crystalline evaporation to precipitate REEs as REEssulfate.
Finally, a workable flow sheet describing all the studied procedures for
the processing of studied ore material has been proposed.
Thus, this research work can be applied on an economic level, offering a
simple new technique and economically promising to extract of strategic
elements value such as uranium and elements of economic value such as
copper and vanadium and the rare earths of dolomite ore from Al-uga Future
goal: It is to apply the obtained promising laboratory results in the Nuclear
Materials Authority. First in a semi pilot project and seconed in full pilot
project plant.