الفهرس 
INTRODUCTION AND LITERATURE SURVEYOnly 14 pages are availabe for public view
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Abstract
Rare earth elements (REEs) have seen a significant surge in demand recently because of their wide range of possible uses in advanced technologies. REEs are known as ”the vitamins of modern industry” due to their requirement. Heavy environmental pollution and a rise in the economic cost of these components result from industrial separation from REEs ores. Additionally, it was challenging to separate REEs due to their comparable chemical and physical characteristics. Precipitation, adsorption, solvent extraction, and ion exchange are just a few of the procedures that have been used to separate REEs. Due to its high production capacity and quick mass transfer, the main industrial-scale approach uses solvent extraction from the leaching solution and is followed by an ion exchange procedure.
The main objective of thesis is to develop selected process for separation of individual or groups of rare earths from the effluent solution produced after monazite digestion on chemical precipitation, solvent extraction and ion exchange resins. For this purpose and after a brief review of the different methods for the separation of the individual REEs, it was found that the band displacement technique using an ion exchange resin represent the main and unique commercials process actually applied for REE’s separation at the highest possible purity exceeding 99.99%. The up-grading and purification was fulfilled through solvent used as tri-butyl phosphate and economical resins as cation exchange resin Dowex 50-X8.
The laboratory separation procedure is oriented to be commercialized for large industrial scale application (utilizing the commercially available reagents in Egypt). The present thesis is composed of a three main chapters; each can be summarized as follow:
I. IN THE FIRST CHAPTER, a full literature survey concerning the rare earth elements with a special focus on monazite was introduced. The main points that have been discussed through this chapter can be summarized as follow:
a) The definition of rare earth elements and their discovery.
b) Exploration of the different minerals containing rare earth elements, their distribution and reserves all over the world.
c) The properties of rare earth elements atoms and ions, which include the electronic configuration, position in the periodic table, oxidation states, magnetic and spectral properties.
d) The different methods for the physical and chemical processing of monazite and rare earth elements were presented and reviewed.
e) Reviewing of the methods concerning the separation of rare earth elements.
f) A brief review on solvent and ion exchange extraction of rare earth elements from acidic solutions.
II. IN THE SECOND CHAPTER, the utilized chemicals, reagents, materials, instruments and equipments were stated. We can summarize this chapter as follow:
a) Chemicals and Reagents.
b) Instruments and Equipments
c) Preparation of rare earth hydrous oxides, thorium and uranium oxides cake from Egyptian monazite
d) Demonstration of the analytical procedures for determination of rare earth elements, thorium and uranium.
e) Sulphuric acid digestion procedure for monazite was carried out in order to get a rare earth, thorium and uranium cakes were also summarized.
g) Studying of Thorium, rare earth elements and uranium Precipitation Efficiency.
h) Methods for different applied solvent extraction schemes for rare earth elements separation and purification were also presented with their calculations.
i) Methods for different applied ion exchange extraction schemes for rare earth separation and purification were also presented with their calculations.
III. IN THE THIRD CHAPTER, the results of experimental chapter were declared and discussed. This chapter consists of three main parts;
a) In the first part,
Cerium oxide production:
Rare earth, uranium, thorium feed solutions on the semi-pilot trial were prepared in batches by adding monazite (85 %) to sulfuric acid at high monazite/acid ratio (1:2). The mixture was stirred for 2.5 hrs at 200-220 oC, and then diluted with iced water. The slurry was filtrated and the filtrate was diluted with H2O, and the remaining residue constitutes silica, zircon and other undigested gangue minerals. The produced acidic leach liquor was precipitated by diluted ammonia solution at pH 1 to precipitate thorium as pyrophosphate. The resultant filtrate after thorium separation was neutralized to a pH value of 2.5 using the ammonia solution to precipitate the REEs cake. The produced cake reacted with coastic soda over stiochiometric ratio to produce rare earth oxides. Rare earth element oxides cake was dissolved in concentrated hydrochloric acid then precipitated with ammonium hydroxide at two pHs 5.8 and 9. The rare earth hydroxide which produced at pH 9 was air oxidized in dryer at 160°C for 10 hours. Rare earth hydroxide was leached with nitric acid solution. The rare earth solution was oxidized with (0.2mol/L) potassium permanganate with the addition of 0.3mol/L Na2CO3 for 85% purity of cerium oxide at pH within 2.5 to 3.0.
b) In the second part:
group and Individual REEs Isolation by tri-butyl phosphate
The acidic filterate after monazite digestion was precipitated first at pH 1 to produce thorium pyrophosphate, filtrate. The second filtrate was completely precipitated by sodium hydroxide till pH 9; add sulfuric acid gradually till reach pH to 1.75. 150 gm of this TREEs was totally dissolved by concentrated nitric acid and completed to 1L by distilled water (the mother liquor of the solvent separation process). The organic extractant is combined with the pregnant leach solution, which contains effective levels of REEs, a mechanical shaker was used to shake the mixture at a specific volume ratio for five minutes at room temperature, then a separation funnel was then used to separate the two phases. Studying the concentration of TPB, different stripper, different scrubber, and concentration of stripper to isolate the LREEs from MREEs with 55.94, 11.48, 14.97 and 7.61 % purity of Ce, La, Nd and Pr respectively in the fifth stage. Ce and Nd were extracted with percent purity equal 55.32 and 44.68 respectively in the first stage after studying the pH control, contact time.
c) In the third part:
Ion exchange for lanthanon
The partial separation of some individual REEs from such mixture was tried for member’s fractionation via common applied cationic exchange resin Dowex 50 -X8, with size 100-200 mesh in the sodium form. Results of separation of rare earth as groups or individually by ion exchange resin Dowex 50-X8 will be herein discussed from chloride media and 0.5 M citric acid solution adjusted to a pH 3.9 with a contact time of 150 min. which was used as eluting agent. It was found that many neodymium fractions can be obtained started from ultrapure fraction with > 99.99 purity from the collected eluate in the effluents no. 11, 12, 13, 14, 15 in which no any other trace quantities of REEs were detected with total perecent recovery nearly " ~ " 50% of Nd content in the starting loading group REEs solution. The many other fractions for Nd can be collected through addition of the previous five eluent cuts and the next three cuts to reach maximum recovery >98% of the eluent content but it was against the purity. In other words neodymium concentrates with " ~ " 100, 99.5, 98, 97.1% purity and 50, 80, 81, 82.5 % recovery can be obtained on the desire for marketing or further chemical or technical approaches for the fractions obtained.