الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Phosphate rock is considered as one of the most promising potential new recourses of REEs. These elements play significant roles in the development of future energy, particularly green energy, high tech equipment, and advancement of various key technologies. In phosphoric acid production using wet process, REEs are distributed into two parts; about 30 % of REEs enter phosphoric acid solution, while 70 % REEs transferred into phosphogypsum which means that REEs split into various streams in the treatment of phosphate rocks. Accordingly, it is far better to extract uranium and REEs from the phosphate rock than spread it over to different streams. In this regards, the present work aimed to develop a convenient flowsheet for production of pure REEs from Abu-Tartur phosphate rock through the following processes; leaching of rare earth elements from Abu-Tartur phosphate rock using tartaric acid followed by the extraction of REEs from the produced acidulate solution using D2EHPA organic solvent. The REEs is then stripped from the loaded organic solvent using hydrochloric acid, and finally, precipitated as REEs oxide.
The present thesis is composed of a three main chapters, each of which can be summarized as follow:
THE FIRST CHAPTER:
This chapter concern with a full literature survey for REEs importance and resources, kinetic leaching of phosphate ore and recovery of REEs from phosphoric acid. The main points that have been discussed through this chapter can be summarized as follow:
Importance and different applications of Rare earth elements.
Rare earth elements conventional and non-conventional resources.
REEs occurrences in Egypt.
Phosphoric acid production.
Leaching of phosphate ore by organic acids.
Kinetic analysis of phosphate rock leaching process.
Different approaches for REEs recovery.
THE SECOND CHAPTER:
The utilized chemicals, reagents, materials, apparatus, instruments and equipment were stated. It could be summarize the experiments which have been done in this work as follow:
Preparation of Abu-Tartur phosphate rock working Sample.
Study the factors affecting the leaching of REEs from Abu-Tartur phosphate rock by tartaric acid which include; tartaric acid concentration, temperature, leaching time, liquid/ solid ratio, and mechanical stirring speed.
Investigate the kinetic leaching of REEs as well as P2O5 from Abu-Tartur phosphate rock by tartaric acid.
Application of Design of Experiments methodology to optimize REEs leaching process.
Study the parameters controlling the extraction of REEs from the produced leach liquor such as; D2EHPA concentration, shaking time, temperature, aqueous/ organic phase ratio, and mechanical stirring speed.
Investigate the factors affecting REEs stripping from the loaded organic solvent by hydrochloric acid which include; shaking time, hydrochloric acid concentration, organic/ aqueous phase ratio, ratio and mixing stirring speed.
THE THIRD CHAPTER:
The results of experimental chapter were declared and discussed. This chapter consists of three main parts; rare earth elements leaching investigation, REEs extraction from the produced leach liquor by D2EHPA organic solvent, and REEs stripping from the loaded organic solvent using hydrochloric acid.
The first part
This part includes the REEs leaching investigation using One-factor-at-a-time (OFAT) methodology and Design of Experiment (DoE) methodology. In regards to OFAT methodology, the impact of leaching time, tartaric acid concentration, liquid/ solid ratio, reaction temperature, and mechanical stirring speed have been investigated. The obtained results clear that stirring time, tartaric acid concentration, and liquid/ solid ratio have enhanced the REEs leaching efficiency while reaction temperature and mechanical stirring speed have almost no effect on the leaching process. The preferred leaching conditions for REEs leaching from phosphate rock were; 0.5 M tartaric acid concentration, reaction time of 30 min, liquid/ solid ratio, ml/ g, 5/ 1, room temperature. The leaching kinetics of REEs and P2O5 was performed in order to obtain the leaching activation energy. The kinetic data show that the leaching rate was controlled by the diffusion of reactants through a porous ore, and the apparent activation energy were about 12.4 for REEs and 15.0 kJ/ mol for P2O5.
According to the DOE methodology, four factors were taken into consideration in the experimental planning: tartaric acid concentration (A), liquid/ solid ratio (B), reaction time (C), and reaction temperature (D). In this regards, the full factorial design involving 16 treatment combinations and 4 replications of the central point are chosen to investigate the REEs leaching process. The obtained results clear that about 96.9 % of REEs was successfully leached from Abu-Tartur phosphate rock regards to the following conditions; 0.6 M tartaric acid concentration, liquid/ solid ratio, ml/ g, 3/1, reaction time of 45 min and room temperature. The normal first order model (fitted model) between significant factors and the response was developed by the Design Expert 10.0 software.
Y REEs = 46.69 - 2.57 * A + 1.71 * B + 7.58 * C -15.39 * D -12.07 * AB + 8.36 * AC -7.37 * AD + 3.40 * BC + 2.57 * BD -6.26 * CD + 1.84* ABC + 3.40 * ABD -1.98 * ACD -3.39 * BCD -1.85 * ABCD
The obtained results clarify that the positive sign of coefficients for main factor B, C, and the interactions AC, C, ABD, BC, BD, and ABC confirm their enhancement on REEs leaching percent while the negative sign of coefficient for the main factors A, D, and the interactions of AB, AD, CD, BCD, ACD, and ABCD denotes a negative effect. These results are different than the results obtained from OFAT methodology, where in the OFAT methodology; tartaric acid concentration (A), liquid/ solid ratio (B), reaction time (C), factors are positively affect the REEs leaching process. The analysis of variance (ANOVA) for the fitted model showed that there is a good agreement for REEs leaching process between the experimental data and the model, which means that the model is statistically significant and predictable with in the chosen variables.
In the second part
This part concerns with the the effect of different factors in REEs extraction process from the produced leach liquor using D2EHPA organic solvent in kerosene. These factors were: shaking time, D2EHPA concentration, temperature, aqueous/ organic phase ratio, and stirring speed. The aforementioned results clear that, REEs extraction efficiency increase by increase shaking time, D2EHPA concentration, aqueous/ organic phase ratio, and stirring speed. However extraction temperature has negative effect on the extraction process. The preferred extraction conditions were found to be; 0.6 M D2EHPA in kerosene, shaking time of 10 min, room temperature, aqueous/ organic phase ratio equal 3, and stirring speed 300 rpm. The extraction isotherm indicates that, theoretically two stages are enough to extract about 95 % of total REEs content in the phosphate ore leach liquor.
In the third part
This part deals with the impact of various parameters on REEs stripping from the loaded organic solvent using hydrochloric acid. These variables included; shaking time, hydrochloric acid concentration, organic/ aqueous phase ratio, temperature, and stirring speed. The obtained data indicated that, REEs stripping process enhanced with the increase in shaking time, hydrochloric acid concentration, temperature, organic/ aqueous phase ratio and stirring speed. The preferred stripping results were found to be; 1.0 M hydrochloric acid; shaking time of 15 min, O/ A phase ration of 2, stirring speed of 200 rpm, and reaction temperature of 40 oC. Based on these conditions, theoretically 3 stages were sufficient for removing about 96.5 % of the total present REEs in the loaded organic. Finally REEs was precipitated from the pregnant strip solution using oxalic acid. The produced REEs oxalate precipitate was calcined to obtain rare earth oxide (ΣREO). The assay of the produced (ΣREO) was about 87.8 %. The produced REEs precipitate was collected for further separation of individual REEs.