الفهرس 
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Abstract
The present work is concerned with the chemical processing of Egyptian monazite
sand concentrate (-96% purity) produced from Rosetta beach black sand. The concentrate is
prepared by NMA pilot plant using different physical dressing techniques as based upon the
specific gravity. the magnetic and the electrostatic characteristics of the beach mineraI
constituents. The purpose of the chemical processing is to separate U. Th and REE in their
maximum possible purity to ensure successfully marketable concentrates of adequate purity
suitable for various applications. For U and Th concentrates. their preparation in nuclear pure
forms suitable for nuclear fuel would represent the tinaI target.
Two main chemical methods for monazite processing are competitive and have
actually been commercially applied. These include the alkali process using caustic soda and
the acid processing using sulfuric acid. The former has been applied on a pilot scale at Inchass
Facility of NMA since the sixties. In this process. the phosphate component of the mineraI is
converted to trisodium phosphate while the metal values remain insoluble in the form of what
is called the hydrous oxide cake. The latter is then dissolved in HCI and subjected to gradual
neutralization fist at plI 5.8 to obtain the umcake and then at a pH of about 8 to precipitate
the REE cake. In the sulfuric acid process. the whole mineraI is dissolved resulting in U. Th
and REE sulfates and phosphates. Various recovery techniques have been studied for the
separation of these metal values. However. in the eighties of the last century. it was proven
that the primary amines are capable of selectively extracting U and Th values from sulfate
liquors and it was therefore found necessary to carry out the present work. In the latter, it was
also required to develop a rapid, sensitive and reliable method for U, Th and total REE
analysis of the working mineral concentrate as well as during its breakdown and recovery of
its metal values.
This thesis is therefore divided into thtee main topics, the first is the development of
an IC method for U, Th and total ~E analysis while the second topic involves the acid
breakdown of the monazite concentrate by sulfuric acid and investigating the relevant parameters. The recovery of the metal values from the obtained sulfuric liquor represents the
third topic.
The developed IC method for U. Th and IREE was studied using a Dionex 200
system fitted with an Ion Pac CSSA analytical colwnn and an Ion Pac CGSA guard column. A
gradient elution protocol was applied and the eluent used was composed of HCI and (NHchSO •. The coDCCDtrationofboth eluent composition was studied as well as the effect of
the flow rate to determine the optimum retention time and efficient resolution of the three
analytes. The obtained results revealed that the optimum flow rate is 0.7 mUmin. Separation
of U from Th and IREE was obtained by solution assaying of 0.1 M HCI and 0.1 M
(NH4hSO.. while separation of Th from IREE was achieved using a solution assaying of 0.1
M HCL and 0.2 M (NH4hSO.. . Using these optimum conditions, the necessary standard
curves obeying Beets law have been plotted in the range of 5.79 to 174.5 m&’L for U and in
the range of 5 to 150 mlifL for Th and !REB. The analyzed monazite sand concentrate used in
this work assayed 61.12% RE2OJ, 4.70% ThOz and 0.42% U30 •.
For the breakdown of the study monazite by the sulfuric acid process, several
conditions have been studied including the effects of the acid input, the sand grain size, the
solidlliquid ratio as well as the effects of time and temperature. from the obtained results, it
has been concluded that about 96% monazite dissolution would be obtained by applying the
following optimum conditions upon the Egyptian monazite sand concentrate (as received) ; viz,
- Sulfuric acid concentration (v/v): 80%
• Solidlliquid ratio : 1/3
• Reaction time : 2.5 hr
- Reaction temperature : 180°C
For studying the recovery of U, Th and IREE from monazite sulfilte liquor, various
techniques have actually been applied. The selective precipitation of Th and REB was first
tried using a sulfate liquor assaying (in gIL) 32.20 REB, 2.47 Th, 0.2 U while sol- and PO.3-
assayed 200.12 and 8.94 respectively. Using l00A. Nl40H solution, sevcml sul&te solution
samples have been neutralized to varying pH values. At pH 2, it was found that all Th and
about 9OO” REB have been precipitated together with about 100” U. After filteriDg and proper
washing of the latter, the pH of he obtained filtrate (120 mwr. U)was re-adjusted to 1.8 and
was then passed through an anion exchange column (Amberlite IRA400) for U adsorption.
However due to the high sulfate content (about 200 gIL) beside phosphate (about 9 gIL) the
resin capacity for U did not exceed Sg/L i.e. less than 5% of its theoretical capacity. Ui’anium
was almost readily eluted by 1 M NaCl acidified with H2SO. to O.IM. A contact time of 2
min which corresponded to 7.5 mUmin was used for U elution.
Failure to achieve economic results for U recovery by the ion exchange resin and due
to the fact that primary amines ( 10 earboa atoms) are C8p1bJe of extracting bodI U aDd 1b
It3
from sulfate liquors it was decided to investigate the potentiality of applying this technique to
working monazite sulfate leach liquor. For this purpose dodecyJamine was used and the
relevant extraction and stripping conditions were studied. The former included the amine
concentration, the pH of the sulfate Iiquor, the extraction temperature as well as the nature of
the diluent For studying the effect of the amine concentration, various solutions assaying
between 0.1 up to 5.4% amine in benzene were prepared and allowed to contact the aqueous
phase (room temperature ==25OCtIII for the O/A ratio and using a contact time of 5 min). The
obtained results revealed the improvement of the extraction coefficient with increasing the
amine concentration. The effect of the pH of the working sulfate liquor was also investigated
between pH values ranging from -0.5 to 1.0 and indicated that the distribution coefficient is
greatly improved by increasing the pH. Regarding the diluent, toluene, kerosene and methanol
were used beside benzene. Benzene has indeed resulted in the best coefficients for both U and
Th, On other hand, the equilibriwn data of U and Th obtained by applying different 0/A
ratios during extraction were used to construct the corresponding McCabe_Thiele extraction
diagrams, An operating line of slope 0.575 (equivalent to organic/aqueous flow rate )was
found .suitable for both curves. from the two diagrams, it would be clearly evident that 2 to 3
theoretical stages would be sufficient. Finally, nitric acid with different concentration Was
applied as a possible selective stripping agent. A suitable loaded otganic phase sample
assaying 0.79 g UIL and 11.314 g Th/L was prepared for this purpose. However, it was recommended to apply NaCI or NH4N”0) in presence of a low concentration of the
corresponding acid,