الفهرس 
SPENT NUCLEAR FUEL (SNF)Only 14 pages are availabe for public view
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Abstract
Palladium, molybdenum, zirconium and niobium are among the
fission products and are considered as strategic materials The
increasing demands of these elements in different industrial and
nuclear applications faced with limited and decreasing natural
resources (especially for Pd), makes spent nuclear fuel a potential
source of these metals and an alternative to mineral contributors. In
this context, liquid-liquid extraction, emulsion liquid membrane
(ELM) and sorption techniques are employed for the extraction and
separation of Pd, Mo, Zr and Nb from nitric acid medium using
commercial extractants such as green diesel fuel, CYANEX 471X,
CYANEX 923 and Ionquest 801. The different parameters affecting
the liquid-liquid extraction process of these metals have been
separately studied in terms of shaking time, nitric acid, hydrogen ion,
nitrate ion, extractant and metal ion concentration, the phase ratio
and temperature, stripping investigations were also studied. The
possibility of extraction and recovery of palladium from the sulphate
leach solution of spent automotive catalyst using green diesel in
kerosene was explored and a modified process is proposed and
evaluated.
In the ELM investigations for palladium extraction using CYANEX
471X in chloroform as carrier, the effects of the different parameters
affecting the membrane stability were studied as well as the kinetics
of Pd(II) permeation through the prepared membrane were also
discussed and the results indicated that the rate of permeation
depends on the carrier, Pd(II), and nitric acid concentration. The
extraction of molybdenum (VI) from aqueous nitric acid solution
with trialkylphosphine oxide (CYANEX 923) in kerosene as diluent was carried out and the results show that the loading capacity of
CYANEX 923 was found to be 0.015 mole of Mo (VI) per mole
extractant. In order to test the viability of the used extraction system
(CYANEX 923/kerosene) for the extraction of Mo(VI) from its ores,
an application study under the optimum experimental conditions was
carried out on the Gattar Granite ore.
The adsorption of Mo(VI) from nitric acid solution using styrene
divinyl benzene copolymer (SM-4) impregnated with 30% CYANEX
923 using batch and column techniques were carried out. The effects
of the different parameters affecting the extraction of Mo(VI) such as
contact time, nitric acid concentration, V/M ratio, metal ion
concentration as well as temperature effect were investigated. The
experimental results show that sorption of Mo(VI) obeys Freundlich
isotherm. Breakthrough curves indicate that column performs better
with low flow rate, concentration and high bed height. An application
was also carried out on Gattar granite for the recovery of Mo(VI)
from other metals.
The extraction of Zr(IV) and Nb(V) from nitric acid solution with
IONQUEST 801 in kerosene were also separately studied. The
effects of the parameters affecting the extraction process were
investigated. Further, the separation feasibility of zirconium and
niobium is also discussed based on the experimental results of their
extraction and stripping percentages as well as temperature effect. In
this respect, two successive separation methods were investigated to
separate zirconium from niobium from their admixture and flow
sheets which describe the separation process are proposed.
In addition, the separation process of the four investigated metals
from each other from their mixture in a synthetic solution was investigated. A flow sheet which summaries the proposed method for
separation between Pd (II), Mo(VI), Nb (V) and Zr (IV) from 3 M
nitric acid is proposed.
Key words: Solvent Extraction, CYANEX 923, Emulsion membrane,
CYANEX 471X, Sorption, IONQUEST 801, , Nitrate medium,
palladium, molybdenum, zirconium, niobium.