الفهرس 
INTRODUCTION
Properties of Heavy Metals Under InvestigationOnly 14 pages are availabe for public view
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Abstract
The main objective of this work is to develop new
methods for the determination of Cr(VI), Mo (VI) and U(VI) in
ground water and rocks using striping voltammetry and
derivative spectrophotometry. Stripping voltammetry, have
important advantages such as high sensitivity, low detection
limit, relative simplicity and low cost of equipment and
automatic on-line and portable options, for the determination
of metals at trace levels. Derivative spectrophotomtery offers
greater selectivity than does normal spectrophotomtery ,
because it decreases spectral overlap and allows better
resolution.
Chromium is widely distributed in nature,
hexavalent chromium(VI) is a potential carcinogenic agent ,
moreover it has become one of the main pollution sources for
environment. Consequently, the accurate determination of
chromium(VI) is important for monitoring environmental
pollution and for quality control of industrial products.
Molybdenum is a biologically and physiologically
significant element. Due to its unique properties and its
importance in nature, Mo has been the subject of a great deal
of attention in terms of developing new methods for its
determination.
It is well known that uranium is toxic as well as being
radioactive; the safety profiles for uranium compounds are
well established. Because uranium is a relatively mobile
element in many surface or near-surface environments, its
geochemical exploration methods require the measurement
of the trace quantities of the metal ion in water samples,
along with that in plants, soils, and rocks.
The present study is undertaken, hopefully, to cover
the subject of interest and to present some thorough work
on direct voltammetric and spectrophotometric
determination of chromium , molybdenum and uranium
content of ground water and rocks samples. In any case, here
it is for the benefit of any one who would like to make use of
it.
The thesis comprises five main chapters. In addition,
the aim of the work, summary and a list of references are
included.
Chapter One:
In the first chapter an introductory section is
given including, properties of heavy metals under
investigation, stripping analysis measurements and derivative
spectrophotometry. General survey of the voltammetric and
spectrophotometric determinations of Cr(VI), Mo(VI) and
U(VI) is given.
The literatures showed that, no studies have yet
been reported demonstrating the solution equilibria of
chromium, molybdenum and uranium with any of the
reagents used in this study or the use of these reagents for
voltammetric and spectrophotometric determination of
chromium, molybdenum and uranium.
Recently, our newly article entitled ”Determination of
uranium(VI) in underground water and rock samples by
adsorptive cathodic stripping voltammetry” has been
accepted for publication in El-Minia Science Bulletin,
2013,24(1),1-23.
Chapter Two:
This chapter, describes the experimental details of
the preparation of solutions needed to analysis of the water
and rock samples. Instrumentation and working procedures
are also described.
Chapter Three:
This chapter includes the results and discussion of the
voltammetric analyses of the three metal ions under
investigation in the water and only uranium(VI) in rock samples
was determined using standard addition method. This method
is applied to minimize the interferences (if any) and to measure
the signal of the total metal content under the same
environment of the sample. Plotting the currents signal against
the metal ion concentration added to the sample gave straight
lines. from this linear relationship, the concentrations, the
standard deviation and correlation coefficient values were
obtained. In what follows are the conditions of the
determination of metal ions under consideration. This method
depends on increasing the concentration of the metal onto the
electrode surface by adsorption phenomena.
The optimum conditions were adjusted to obtain the
highest reduction peak signal and resolution for these metal
ions in different samples.
(a) Cr(VI) was determined by cathodic linear sweep
stripping voltammetry (CLSSV) using a mixture of 7.5 X10-3M
potassium nitrate as supporting electrolyte and 10 mM mono
and disodium hydrogen phosphate as buffer solution pH~7 at
accumulation potential + 0.05V vs. Ag/AgCl sat’KCl.
(b) Mo(VI) was determined by differential pulse anodic
stripping voltammetry (DPASV) using a mixture of 7.5 X10-3M
potassium nitrate as supporting electrolyte and 10 mM mono
and disodium hydrogen phosphate as buffer solution pH~7 at
preconcentration potential -0.6V vs. Ag/AgCl sat’KCl.
(c) U(VI) was determined by differential pulse cathodic
stripping voltammetry (DPCSV), using a 1 X10-2M solution of
sodium perchlorate as a supporting electrolyte and potassium
hydrogen phthalate as a buffer solution pH~7 at accumulation
potential of -0.4V vs. Ag/AgCl sat’KCl.
The results indicate that the concentration of metal
ions content in water samples is less than permissible value as
given by EPA, Canadian Drinking Water Quality, and the World
Health Organization’s guideline.
Chapter Four:
This chapter in cludes the results and discussion of
the spectrophotometric study of the acid-base equilibria
of Purpurogallin in aqueous solutions containing 40% (v/v)
ethanol. The spectral changes are explained in terms of shifts
in equilibria amongst different molecular and ionic species
existing in solutions. The ionization constants corresponding
to the various acid-base equilibria have been determined.
Also the results of the complexation reactions of Cr(VI),
and Mo(Vl) with Purpurogallin have been discussed. The
composition, molar absorptivities, equilibrium constants and
stability constants of the chelates of this reagent were
determined. The absorption spectra of solutions with
equimolar concentrations of metal ion and the ligand or with
an excess of one component were recorded at different pH
values in 40% (v/v) ethanol medium.
A rapid and sensitive method has been proposed for
simultaneous determination of Cr(VI) and Mo(Vl) in their
binary mixture using derivative ratio spectra and zerocrossing
techniques. The proposed method has been applied
successfully for simultaneous determination of Cr(VI) and
Mo(Vl) content of some rocks .
Chapter Five:
This chapter includes the results and discussion of
the spectrophotometric study of the acid-base equilibria
of Pyrocatechol Violet in aqueous solutions containing
40% (v/v) ethanol. The spectral changes are explained in
terms of shifts in equilibria amongst different molecular and
ionic species existing in solutions. The ionization constants
corresponding to the various acid-base equilibria have been
determined.
Also the results of the complexation reactions of U(VI),
and Mo(Vl) with Pyrocatechol Violet have been discussed.
The composition, molar absorptivities, equilibrium constants
and stability constants of the chelates of this reagent were
determined. The absorption spectra of solutions with
equimolar concentrations of metal ion and the ligand or with
an excess of one component were recorded at different pH
values in 40% (v/v) ethanol medium.
A rapid and sensitive method has been proposed for the
determination of U(VI) or Mo(VI) in the presence of Fe(III)
and V(V) in their ternary mixture using derivative ratio
spectra, zero-crossing technique. The proposed method has
been applied successfully for determination of U(VI) or
Mo(VI) content of some rocks.