الفهرس 
Introduction & Literature reviewOnly 14 pages are availabe for public view
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Abstract
The interesting demand of radioactive elements in
nuclear energy program require a suitable method for their
separation, preconcentration and determination in various types
of samples e.g. rocks, waste effluents, water samples and etc.
Actually, these heavy elements have been present virtually
everywhere in the earth’s crust. The great interest for their
accurate determination at low concentrations arises from their
toxicity and the possibility to reach human beings through
different pathways. They are known to cause acute
toxicological effects for human and their compounds are
potential occupational carcinogens.
Modern analytical chemistry is characterized by
hyphenated analytical methods which involve a combination of
a separation and/or sensitive detection technique with a
preconcentration step. The latter operation is a consequence of
the problems encountered in the chemical analysis of real
analytical samples such as low analyte concentrations (in many
cases incompatible with quantification limits of instrumental
methods) and high concentrations of matrix interference
species present in these complex samples, especially those of
environmental origin. Consequently, there is an ongoing need
for the development of separation and preconcentration
procedures prior to their determination which should be safe,
rapid, convenient, and accurate.Several enrichment and separation techniques including
solvent extraction, coprecipitation, ion exchange,
electrodeposition, cloud point extraction and solid phase
extraction have been used for separation of most analytes
before their determination.
In the last decades, cloud point extraction and solid
phase extraction procedures have been extensively applied to
trace metal ions before their determination in several matrices.
These techniques offer several advantages including
experimental convenience, low cost and environmental safety.
The use of micellar systems such as CPE has attracted
considerable attention in the last few years mainly because it is
in agreement with the “green chemistry” principles, because
low amounts of low toxicity surfactants replace the usual toxic
organic solvents. In addition, surfactants are non-flammable
and present low volatility, minimizing risks in the extraction
process.
Cloud point extraction procedure is based on the
following phenomenon: When a non-ionic surfactant solution
is heated over a critical temperature, namely cloud point (CP),
the solution easily separates into two distinct phases. The first
one is a surfactant phase, which consists a large hydrated
micelles (surfactant-rich phase) of the small volume and the
second one (aqueous phase) is an aqueous solution in which the
concentration of the surfactant is approximately equal to the
critical micelle concentration. Any organic or inorganic species
interacts with the aggregates of micelles formed, and at and above cloud point it will be extracted into small surfactant-rich
phase.
Solid phase extraction is another approach that offers a
number of important benefits. It reduces solvent usage and
exposure, disposal costs and extraction time for sample
preparation. In recent years SPE has been successfully used for
the separation and sensitive determination of metal ions.
The present work is concerned with the
preconcentration and separation of thorium(IV) by cloud point
extraction from aqueous solutions using Triton X-114 as a nonionic
surfactant and 5-Br-PADAP as a complexing agent. The
effect of parameters affecting the cloud point extraction of
thorium ions is investigated. Also, the factors controlling the
determination and preconcentration of uranium after the
adsorption of (NH4
+) (TPB-) ion pair complex on naphthalene
are examined. The present thesis comprises into three main
chapters.
The first chapter
It includes the information about occurrence, the main
uses of uranium and thorium and their hazard effects. It also
contains the literature survey related to the methods of
separation and preconcentration (cloud point extraction and
solid phase extraction) for the two interested elements.Additionally, it highlights on the principles and theoretical
aspects for the two procedures.
The second chapter
It involves the specification of chemicals, standards and
reagent solutions with detailed explanation of their
preparations as well as instruments used throughout this work.
It also contains the procedure that used for adsorbent
preparation. Moreover, the method that used for samples
preparation and the recommended procedures for the cloud
point extraction of thorium ions and solid phase extraction of
uranium ions are discussed in details.
The third chapter
This chapter encloses the results and discussion of the
obtained data. It divides into two main parts.
The first part
Cloud point extraction method has been proposed for
the preconcentration of thorium species as a prior step using
5-Br-PADAP as ligand. For that, the formed complex is
extracted by Triton X-114 and subsequently detected
spectrophotometrically at 531 nm. The operating conditions
affecting on CPE procedure of thorium ions from aqueous
solution e.g. pH, buffer type, surfactant concentration, dye
concentration, salt type and concentration, equilibration
temperature and time, centrifugation rate and time, diluting
agent type and foreign ions are studied. It is induced at the
optimized conditions: λ 531nm, pH 3.4, 1.0 ml of 0.05% 5-Br PADAP and 2.0 ml of 0.5% Triton X-114 in the presence of
0.6 M NaCl as salting out with equilibration temperature and
time 55°C, 15 min and centrifuge rate of 5000 rpm in 20 min.
Calibration curve is linear in range (0.125-2.5) μg/ml of Th(IV)
with molar absorptivity of 1.63 ×105 l/mol cm. The proposed
method is applied on different water samples and some
geological silicate samples collected from Wadi Sikait area that
located in the South Eastern Desert of Egypt.
The second part
This part explains the preconcentration of uranium ions
by solid phase extraction technique using (5-Br-PADAP) as
chelating reagent in addition to the (NH4+) (TPB-) ion pair
supported on naphthalene as adsorbent. The reveling factors
effect on the determination of uranium ions such as absorption
spectra, pH, buffer type, reagents concentration, shaking time,
solvent type, influence of foreign ions and validity of the
method are examined and treated. Uranium species are found to
be enriched quantitatively from aqueous solution at pH 8.0, 2.0
ml of 0.05% 5-Br-PADAP, 1.5% TPB and 20% naphthalene.
The linearity is maintained in the concentration range (0.05-
1.0) μg/ml of uranium ions with molar absorptivity 2.63 ×105
l/mol cm. FTIR spectra for ligand and its complex with
uranium ions are carried out and the surface of adsorbent is
examined using SEM before and after loading of uranium that
confirms its adsorption on the surface of naphthalene–NH4–
TPB adsorbent.The investigated procedure is assessed by standard
addition method using fresh water samples and some reference
certified rock samples then applied for analytical uranium
determination in liquid waste and some collected silicate
samples. Finally, we conclude that the procedures of cloud
point extraction and solid phase for the determination of
thorium and uranium ions, receptively using the suggested dye
reagent are simple, highly sensitive and accurate. It can detect
very low concentration levels.