الفهرس 
CHAPTER I : INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
Abstract
Rare earth elements (REEs) are a group of 15 chemical elements in the
periodic table, also it called lanthanides. Scandium and yttrium have a similar
physiochemistry to the REEs. In this thesis, the main objective of the studies
aims to sorption some of rare earth elements by ion exchanger process. In this
respect, preparation of new hybrid inorganic ion exchanger by precipitation
method and study their removal efficiency towards REEs has been carried
out. The present work carried out in this thesis, is classified into three main
chapters.
The first chapter, which is the introduction, includes background
about REES, their properties, their abundance and distribution in different
minerals. It includes information about separation of REEs from their ores
and classification of ion exchange were reported. This chapter also includes
the literature survey of removal and separation of some REEs using ion
exchange methods.
The second chapter is experimental section. It contains chemicals and
reagents those used and their purity, the stock solution of elements under
study and new hybrid inorganic ion exchanger of AST were reported.
Sorption investigations by batch and column system were described. Finally,
description for the instrument those used in this study was reviewed.
The third chapter is results and discussion section. In the first part of
this chapter the optimum conditions of preparation the hybrid inorganic ion
exchanger AST was investigated. Different factors such as molar ratio,
concentration, ageing time and drying temperature on the preparation of
hybrid inorganic ion exchanger has been studied. It can concluded that the
molar ratio of (1:1:1), the concentration of (0.1M:0.1M: 0.003M) and the
ageing time of 4 days at 50 oC as drying temperature are the best conditions
for preparation of a new AST materials.
In the second part, the physicochemical characterization of the selected
hybrid inorganic ion exchanger AST was investigated using various
techniques. In order to gain the property of AST, the Fourier Transformer
Infra Red (FTIR) spectra have been studied. The presence peaks related to
bond were observed. The results of XRD indicated
that the AST materials have the amorphous nature. It was found that the main
elements are Al(III), Si(IV), Ti(III) and H2O which tentatively suggests the
following formula:
[(Al2O3)3 (SiO2)4 (TiO2)] nH2O.
A tentative molecular formula of the exchanger can be written as:
[(Al2O3)3 (SiO2)4 (TiO2)] 8H2O AST 1,
[(Al2O3) (SiO2) (TiO2)9] H2O AST 6 and
[(Al2O3) (SiO2) (TiO2)6] 9H2O AST 20.
Surface area analysis, indicates that AST 1, AST 6 and AST 20 are type
IV according to the IUPAC isotherm, which is typical for mesoporous
materials. The BET surface area of the prepared hybrid materials were 229.8,
151.7 and 145 m2/g for AST 1, AST 6 and AST 20, respectively. It was
observed from DT and TG analyses that AST material has high thermal
stability.
In The third part of this chapter, the prepared hybrid inorganic ion
exchanger AST were tested for sorption of La(III), Eu(III) and Fe(III) ions
from aqueous solution. AST 1, AST 6 and AST 20 inorganic ion exchanger
were found to be the most effective in sorption of Eu(III), La(III) and Fe(III),
respectively. Some factors affecting on adsorption process as function of
influence of pH, influence of shaking time, influence of initial metal
concentration and influence of temperature were studied. The obtained results
indicated that the equilibrium time reached within 120 min at pH 4 for Eu(III)
and La(III), pH 3 for Fe(III). The results of kinetic were analyzed by different
kinetic models. The calculated parameters showed the second-order kinetic
model is the best describing the sorption process and indicating the
chemisorption process. The different isotherm models were applied to
evaluate the sorption isotherms. These models include Langmuir and
Freundlich isotherms. By comparing the calculated correlation coefficients,
R
2
, for each model it can be concluded that the experimental data fit the
Langmuir model better than the Freundlich model. from the Langmuir
isotherm parameters, the maximum capacity q
o
of Eu(III), La(III) and Fe(III)
onto AST l were found to be 44, 36 and 32 mg/g respectively. The maximum
capacity q
o
of Eu(III), La(III) and Fe(III) onto AST 6 were found to be 32, 31
and 26 mg/g, respectively, and the maximum capacity q
o
of Eu(III), La(III)
and Fe(III) onto AST 20 were found to be 33, 33 and 28 mg/g, respectively.
Freundlich isotherm parameters (K and n), showed favorable adsorption and
high of Eu(III), La(III) and Fe(III) onto AST materials. The thermodynamic
parameters (indicated that the endothermic nature,
increased randomness at the solid/ solution interface and the spontaneous
nature of the sorption processes.
In the Fourth part of this chapter: operation and performance of a
column (fixed bed column sorption experiments) were carried out. The
break-through capacity of Eu(III), La(III) and Fe(III) onto AST1 in fixed bed
column were found to be 35, 29 and 25 mg/g, respectively.