الفهرس 
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Abstract
The present work develop selected process for recovery of uranium
and rare earths from the effluent solution to produced commercial uranium
and rare earths concentrate from a low-grade Egyptian ores. The raw
material under study obtained from El-Erediya mineralized ore was
subjected to several hydrometallurgical processes included the leaching step
followed by the uranium separation through the extraction step by using
Ambersep 400 SO4 then the elution step and finally precipitation of the crude
yellow cake. Additional procedure was applied upon the raffinate solution
after the uranium extraction step to prepare rare earth elements concentrate
as a byproduct. The optimum adsorption parameters affecting on the
extraction of rare earths by using cation exchange resin Dowex 50X8 from
chloride medium was studied then the elution step of Dowex 50X8 and
finally the eluate solution subjected to selective precipitation of the rare
earths constituents by using oxalic acid.
This thesis deals mainly with the kinetics aspects of uranium and rare
earth elements respectively by diluted sulphuric acid in the presence of H2O2
as an external oxidant according to shrinking core model (SCM).
A representative sample of El-Erediya ore material containing 0.12
wt% uranium, 0.15 wt% total REEs and 2 wt% iron was subjected as a
beginning on bench scale to various leaching and filtration experiments to
choose the most suitable and moderate conditions to leach maximum of both
uranium and rare earth elements with minimum gangue dissolution. The
present work in this thesis is classified into three chapters as follows:
Chapter (1) Introduction
This chapter includes a brief description of uranium and rare earth
elements in the periodic table, chemical and physical properties of uranium
and rare earth elements, occurrence in nature, ore preparation, resources and
minerals. It includes aim of work and brief account on the location and map.
It contains uranium and rare earth elements dissolution from its ores depending on the type of uranium and rare earth elements mineral. The
industrial applications of uranium and rare earth elements were showed as in
nuclear uses, metallurgy, petroleum-cracking catalysts, in ceramics & glass
industries and other uses. It indicates the extractive hydrometallurgy of the
ores especially uranium, acidic reagents for leaching and oxidant
requirement. In addition, chemistry of uranium and rare earths leached by
sulfuric acid was represented. Further, the best conditions for uranium and
rare earth elements leaching and recovery was obtained. It includes a brief
account on chemical structure of ion exchange resins cation and anion
exchange and chemical structure of anion and cation exchange resin. Also,
chemistry of uranium and rare earth elements with ion exchange and ion
exchange systems was represented. Finally, the literature survey and aim of
the work, which is related to the present work is also given.
Chapter (2) Experimental
This chapter includes chemicals used in the course of this work with
their chemical purity and reagents used in the experimental work. It includes
detailed description of the different instruments used, which are analytical
balance, mechanical stirrer, Hot plate magnetic stirrer, UVspectrophotometer
single beam, pH–mv–temp. meter, atomic absorption for
measuring trace elements, X-ray fluorescence element analyzer (XRF) for
sample characterization and final product determination and ICP-OES for
determination of individual REEs. FT-IR spectroscopy and SEM were
employed to determine the interactions between resin and metal ions. This
chapter also contains methods for determination of uranium, rare earths and
Iron oxide (III) concentration, experimental procedures and equations. This
chapter also contains experimental apparatus, which used in this work.
This chapter contains leaching experiments upon bench scale selective
sample from El-Erediya mineralization to study factors affecting on the
leaching efficiency as acid type, sulfuric acid concentration, contact time,
solids-liquid ratio, particle size, oxidant concentration, stirring rate and the
reaction temperature Uranium extraction parameters from the pregnant leach liquor was
conducted by using strongly anionic ion exchange resin namely; Ambersep
400 SO4. Uranium elution from the loaded anion exchange resin carried out
by chloride elution system, which was applied with the loaded resin.
Ambersep 400 SO4 eluate solutions were objected to complete uranium
precipitation using hydrogen peroxide in the form of uranium peroxide dihydrate.
Study rare earth elements precipitation from the effluent solutions after
extraction of uranium using sodium hydroxide at different pH values. The
optimum adsorption parameters affecting the extraction of rare earths by
using cation exchange resin Dowex 50X8 from chloride medium was studied
then the elution step of Dowex 50X8 and finally the eluate solution subjected
to selective precipitation of the rare earths constituents by using oxalic acid.
All of these experiments, procedures, apparatus and equations were indicated
in this chapter.
Chapter (3) Results and Discussion
The chapter includes the experimental results obtained and their
interpretation. This chapter contains results of various leaching experiments
of El-Erediya ore material. The leaching conditions of: 1.5 M H2SO4; 1 M
H2O2; a stirring rate of 600 rpm, a solid/liquid ratio of 1 : 1, 120 min, a
particle size of 100-64μm at ambient temperature are considered satisfactory
for leaching of both uranium and rare earth elements. The leaching
temperature was self-generated due to addition the amount of concentrated
acid (96%) directly to the leach slurry. Results of leaching condition showed
that the leaching efficiencies of uranium and rare earth elements were 95.2%
and about 83.3% respectively, while minimum iron content was dissolved.
The leaching kinetics study of uranium and rare earth elements showed
that the leaching reaction using H2SO4 acid in the presence of H2O2 as an
oxidant is a diffusion controlled and governed by the shrinking core model
(SCM):1-3 (1-X) 2/3 + 2 (1-X) = k1t
The apparent activation energies of the leaching reaction of uranium
and REEs from El-Erediya ore by diluted sulphuric acid was obtained from
Arrhenius equation to equal 25.0 and 15.3 kJ mol−1 respectively. In addition,
the reaction order of the uranium leaching was determined to equal .00..0
while the reaction order of REEs was about 000.1 respectively. The reaction
order of the total H2O2 concentration of uranium and rare earth elements
were 0.84 and 00.101 respectively.
The kinetics study also showed that the leaching reaction of uranium
and rare earths has a strong dependence on the concentrations of acid,
hydrogen peroxide and solid/liquid ratio. The linear relationship between the
rate constant, k, and the inverse of the initial particle diameter indicates that
the rate controlling step of uranium and rare earth elements leaching is
diffusion controlled. The final empirical kinetic model equation of uranium
and REEs was obtained.
K Uranium = ЌU C1
1.05 C2
1.20 P 1.068 D-2.292 e –25.016/RT
K REEs = ЌREEs C1
1.32 C2
1.36 P 0.456 D-2.120 e –15.35/RT
Uranium extraction from the pregnant leach liquor was studied in
details using ion exchange technique by strongly anionic ion exchange resin
Ambersep 400 SO4. Pregnant pH of 0.25 to 2.75, contact time upon uranium
adsorption from 2.5 to 180 minutes, extraction temperature from 25oC to
60oC, dose concentration (R/A) from 1/40 to 1/500 and initial uranium
concentration of 400 to 1350 ppm. The results revealed that the suitable
extraction conditions for Ambersep 400 SO4 resin pH of sulfate leach liquor
was 1.75, dose concentration (R/A) of 1/250, 60 minutes stirring time at
ambient temperature and finally extraction efficiency increased with the
initial uranium concentration. Under these conditions, uranium extraction
efficiency using Ambersep 400 SO4 resin reached 96.05 %.
The adsorption kinetics was also in agreement with pseudo second
order kinetic model. Langmuir and Freundlich isotherms were tested; the former had better fit with experimental data. The monolayer adsorption
capacity was found to be 56.49 mg/g. Effect of temperature was also studied,
the obtained data showed that temperature has bad effect on adsorption (%),
the thermodynamic parameters were calculated, the obtained data showed
that all ΔG values were negative, indicating that the adsorption process of
U(VI) ions on to Ambersep 400 SO4 resins spontaneous. ΔH value was
negative indicating that the process is exothermic in nature. In addition, the
negative ΔS parameter suggests decreasing the system randomness at the
solid-liquid interface during the adsorption process. Ambersep 400 SO4 was
successfully applied to adsorb U(VI) ions from leach liquor and the obtained
data showed the closeness between these values and previous ones. Thus this
resin can be used as an efficient sorbent for the pre concentration of U(VI)
from aqueous solutions. Homogeneous particle diffusion model (HPDM)
was studied with different agitation speed and temperature; the obtained data
showed that the rate determining step is controlled by matrix diffusion (MD).
The third step in our work is the elution U(VI) loaded on the surface of
used resin. Elution of uranium from the loaded anion exchange resin carried
out by different eluents, sodium chloride the optimum agent which was
applied with the loaded resin with 1.5 M; pH was adjusted to 1.0 by the
sulphuric acid addition. The obtained data indicate uranium elution
parameters were contact time at 60 minutes and the eluate/resin ratio (E/R) is
6/1. The sodium chloride eluate solution was stirred with the loaded
Ambersep 400 SO4 anion exchange resin at agitating speed 250 rpm at
ambient temperature. Under these conditions, uranium elution efficiency
using sodium chloride reached 96%.
Ambersep 400 SO4 eluate solutions were objected to complete uranium
precipitation using hydrogen peroxide in the form of uranium peroxide dihydrate.
The eluates were firstly adjusted by 10% NaOH solution to pH 3.0
then an excess amount of 50% hydrogen peroxide (V/V) was added. The pH
of the eluates was reduced to less than 2.0. Small additions of NaOH solution
were kept eluate solutions pH at 2.0. Finally, the precipitation was left for hours to ensure complete uranium precipitation, and then filtered,
washed by 2 % H2O2 solution (V/V) and dried at 110oC for 6 hrs. The
produced uranium concentrate from Ambersep 400 SO4 eluate solutions
were analyzed using X-ray fluorescence (XRF) element analyzer scanning to
identify the uranium content and the co-extracted elements.
Results of rare earth elements precipitation from the effluent solutions
using sodium hydroxide indicated that the effluent solutions firstly
precipitated at pH 3.3 with sodium hydroxide to precipitate iron then the pH
increased from 3.5 to 9.5 for almost complete precipitation of the present
rare earths, which was quantitatively analyzed using (ICP-OES) to identify
the co-extracted elements.
Rare earth elements extraction by cation exchange resin namely;
Dowex 50X8 from the hydroxide cake which dissolved in hydrochloric acid
medium was studied in details using ion exchange technique by strongly acid
cation exchange resin. Pregnant pH of 0.5 to 4.5, contact time upon rare
earths adsorption from 2.5 to 120 minutes, extraction temperature from 25oC
to 55oC, dose concentration (R/A) from 1/100 to 1/500 and initial REEs
concentration of 150 to 1200 ppm. The results revealed that the suitable
extraction conditions for Dowex 50X8 resin pH of aqueous solution was
1.25, dose concentration (R/A) of 1/400, 75 minutes stirring time at ambient
temperature and finally extraction efficiency increased with the initial REEs
concentration. Under these conditions, REEs extraction efficiency using
Dowex 50X8 resin reached 91.5 %.
The adsorption kinetics was also in agreement with pseudo second
order kinetic model. Langmuir and Freundlich isotherms were tested; the
former had better fit with experimental data. The monolayer adsorption
capacity was found to be 85.47 mg/g. Effect of temperature was also studied,
the obtained data showed that temperature has bad effect on adsorption (%),
the thermodynamic parameters were calculated, the obtained data showed
that all ΔG values were negative, indicating that the adsorption process of
RE(III) ions on to Dowex 50X8 resins spontaneous. The negative ΔS parameter suggests decreasing the system randomness at the solid-liquid
interface during the adsorption process. ΔH value was negative indicating
that the process is exothermic in nature. Dowex 50X8 was successfully
applied to adsorb RE (III) ions from aqueous solution and the obtained data
showed the closeness between these values and previous ones. Thus this
resin can be used as an efficient sorbent for the pre concentration of RE (III)
from aqueous solutions. Homogeneous particle diffusion model (HPDM)
was studied with different agitation speed and temperature; the obtained data
showed that the rate determining step is controlled by matrix diffusion (MD).
Elution of rare earth elements from the loaded cation exchange resin
carried out by different eluents, hydrochloric acid the optimum agent which
was applied with the loaded resin with 4.0M. The obtained data indicate rare
earth elements elution parameters were contact time at 120 minutes and the
eluate/resin ratio (E/R) is 6/1. Hydrochloric acid eluate solution was stirred
with the loaded Dowex 50X8 cation exchange resin at agitating speed 250
rpm at ambient temperature. Under these conditions, rare earth elements
elution efficiency using hydrochloric acid reached 93%.
The properly collected eluates fractions were then subjected to
selective precipitation of the rare earths constituents by using oxalic acid and
washed several times by 1% oxalic acid then dried and ignited at 800oC to
remove the oxalate organics then quantitatively analyzed using ICP- OES).