الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Radioactive waste is one of the most serious challenges that was and still facing many countries particularly those having Nuclear Power Plants. Such waste will most likely remain into the far future, a problematic legacy of the existence of humans especially since the nuclear accidents at Chernobyl and Fukushima.
Radioactive waste is any material that is either radioactive itself or is contaminated by radioactivity, for which no further use is envisaged. Such waste could be resulted from different activities like research, mining and oil exploration, industrial, and medical application of radioisotopes. Radioactive wastes could be categorized in many ways based on their characteristics, e.g. activities, concentrations, toxicities, physical and chemical forms, as well as the half-lives of the radionuclides. The radioactive liquid waste has drawn attention of scientists over the past years; since inappropriate control of such waste may result in transportation of hazardous radionuclides in water and bottom sediments then it becomes a source of threat to the living beings.
The current work has focused on the treatment of radioactive liquid waste using sorbent materials prepared from low cost sources (Eggshell and Fishbone) as an alternative material to the high cost commercial ion exchanges.
The thesis consists of three basic chapters. Chapter (1) is the introduction; chapter (2) is the experimental part that includes the methodology and the practical steps of this work.
The last part is chapter (3) that represents the discussion of the practical results, and explain the- factors affecting the application of the prepared materials for the removal of the metal ions under investigation. The third chapter is subdivided into two parts; the first included the characterization results while the second one is the batch applications results.
Chapter 1:-
The aim of this chapter is to give an overview of radioactive waste, and how it’s classified according to the standards of the International Atomic Energy Agency, as well as types and sources of such waste. The introduction also included the potential dangers and negative impact of the radioactive waste on human health and the environment as well. The adsorption phenomenon and its types, was also highlighted in this part. Also it included a short note about ion exchangers, types, and applications for radioactive waste treatment; up to hydroxyapatite as a model for ion exchanges, where its types and some methods of its preparation were explained, especially from cheap sources such as Eggshell and Fish bones. The last section of this chapter showed the hazardous impact of the radionuclides under investigation, and different contributions to treating these radionuclides using different materials.
Chapter 2:-
In this part the details of the practical steps that were carried out during the research from preparation, characterization, and measurement, were highlighted starting with the chemicals raw materials used for preparation as well as the different methods and parameters used for preparation of sorbent materials were explained in details.
Another section of this chapter was focusing on giving a brief overview of the instruments and measuring tools that were used during the work. The end of this chapter was about batch adsorption technique of the metal ions under investigation through different adsorption parameters included the effect of pH, contact time, initial concentration, and temperature and all related calculations and modeling.
Chapter 3:-
The first section of this chapter represented the discussion of the physicochemical characterization results for the prepared sorbent materials. The XRD results proven that the two prepared materials from Eggshell and Fishbone were hydroxyapatite compared to the standard XRD curve of hydroxyapatite; whereas the XRD of the two modified sorbents was quite different as they were having amorphous nature. This could be attributed to the incorporation of copolymer constituents in to the composite matrix. The surface area results indicated that the prepared materials have relatively low surface area which may support that the adsorption has occurred on the surface.SEM results showed variety of pores and agglomerates for the prepared sorbents.
The XRF results reveals relatively good agreement for HAP and FB with the ideal Ca/P ratio (1.67), where HAP was the closest one to this ratio; while MHAP, MFB didn’t follow this ratio which could be attributed to modification and change of the composite matrix.
The FT-IR spectrum of both HAP and FB has displayed a number of hydroxyapatite characteristic bands such as OH-, CO32- and PO43-, while that of MHAP and MFB have showed the appearance of new bands like CH2, C=O , C≡N, and P–O that belongs to copolymer constituents.
In the second section of this chapter, the experimental results of batch sorption were discussed in details. First the prepared sorbent materials were tested in a preliminary comparison to select the most appropriate materials for further investigation. The results showed a noticeable difference for the removal of metal ions, and in general sorbents that was modified by Acrylic acid and Acrylonitrile were the best; accordingly they were selected for further investigations. Another preliminary test was conducted to select the suitable sorbent amount and results indicated that the appropriate sorbent amount was 0.05 g for all the studied sorbent materials.
In the second step batch adsorption experiments were extensively performed and the start was by effect of pH. The results have showed that solution pH greatly influence sorption behavior and for the studied metal ions it was found that metal ion removal generally increase with increasing solution pH. The high acidic medium causes very low affinity towards metal ion adsorption due to the high competition between H+ and cationic metal ions for occupancy of the binding sites.
The sorption of Co2+ ion was markedly increasing with increasing pH; reaches maximum values of 86, 73, 42, and 44.5 % at pH 8 for both HAP, MHAP, FB, and MFB respectively. The precipitation of cobalt (formation of Co (OH) 2) started at pH 8.5 and reached maximum at pH 11.0; accordingly initial pH of the Co2+ solution suggested with both MHAP and MFB was adjusted at pH 8 due to their acidic nature, while it was- adjusted at pH 6 for HAP and FB and as they already shows slight basicity when introducing to metal ion solution.
The best initial pH of Sr2+ solution was 6 since it exhibited the best removal, and beyond this pH value up to pH 8 there’s a little DROP in adsorption which might be attributed to the increase total ionic strength of the solution due to the addition of NaOH to fix the pH therefore, decreasing Sr2+ sorption.
In terms of Eu3+ removal the alkaline conditions (pH > 6.8) lead to hydrolysis of europium and subsequent precipitation of Eu(OH)3, and to avoid the possibility of precipitation the initial pH of Eu3+ solution used with both HAP and MFB was adjusted at pH 3,whileit was fixed at pH 5 for MHAP and MFB of the acidic nature. Contact time investigations showed that, the adsorption started with an initial rapid adsorption rate followed by a slower one and the equilibrium state was attained at about 180 min.
The effect of initial metal ion concentration was another factor that has been investigated; and it was found that the uptake of the investigated metal ions has enhanced by increasing the concentration of metal ion. This increase in the removability may be due to higher probability of collision between investigated ions and the adsorbent particles.
The effect of temperature was considered crucial parameter in adsorption reactions, and the experimental results of adsorption at three different temperatures, showed different behaviors of the three investigated metal ions.
The adsorption of both Co2+ and Sr2+ ions was an endothermic process, also was Eu3+ sorption except with MFB that was exothermic.
The influence of interfering ions on the adsorption process was also studied using Na+, Mg2+, Fe3+ as coexisting or interfering ions. The results showed that presence of cations usually reduces the percentage removal of metal ions, and these phenomena can be explained in terms of hydrated ionic radius as well as valance of the interfering ion and electronegativity.
It was found that Mg2+, Sr2+, and Fe3+ had the highest effect in reducing the sorption of Co2+ and same result was noticed with Eu3+ while Mg2+, Co2+ were greatly reducing Sr2+ sorption as they have very close hydrated ionic radius. The lowest negative impact was noticed with Na+ ion which may attribute to the lower valance as well as lower electronegativity.
The sorption studies were analyzed at different temperatures using Freundlich, Langmuir, D-R and Temkin sorption isotherm, and the correlation coefficient r2 values showed that Co2+ and Sr2+ were better described with Freundlich isotherm model. The separation factor of Langmuir (RL) values were found to be less than one and greater than zero showing a favorable sorption. ).
The isotherm modeling results of Eu3+ indicated that the adsorption was best fitted and described by D-R adsorption model for both HAP and its modified form MHAP. from Langmuir isotherm modeling the qm value as well as Qo was increasing as the temperature increased and this may suggest that the distribution coefficient was considerably increased by enhancing the solution temperature from 25 to 45°C.
On the other hand the FB and MFB results showed that the correlation coefficient r2 is closer to unity for Langmuir than the other three models.
The mathematical calculations indicated that the obtained n values of Co2+ was higher than unity which mean that the adsorption is most likely physisorption. This result also was of a good agreement with D-R free energy calculations that was < 8 kJ mol−1 indicating that physical adsorption may be the predominant of the adsorption process.
For kinetic studies different kinetic models were applied like pseudo-first order, pseudo-second order, Elovich, and Intraparticle diffusion models; and the results indicated that the adsorption process was better described by pseudo-second order rate equation.
In terms of regeneration of the exhausted sorbent materials, and from economical point of view a desorption experiment was conducted using three different reagents HCl, NaOH and distilled water, and it was found that mineral acid was the most effective desorbing eluent as this reagent could alter the chemical for of the adsorbed metal ion or destroy the bonding between the adsorbate and adsorbent.
The efficiency of the prepared sorbents was finally assessed through application for the treatment of simulated radioactive liquid waste containing 60Co,134Cs, 90Sr, and 152Eu radionuclides. The results showed that the efficiency of the prepared sorbents towards adsorption of these hazardous radionuclides was higher than many sorbent materials used by different researchers.