الفهرس Only 14 pages are availabe for public view
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Abstract
Sorption of both radionuclides and organic ingredients onto solid sorbents is one of the most important ways in processing the aqueous wastes generated from nuclear activities for both inorganic and organic ingredients.The radioactive waste solutions contain chemicals mainly used in decontaminating processes at nuclear activities. The selected contaminants used are 134Cs, 89Sr and 60Co in addition to phenol. So, the current work in this thesis is directed to specify natural materials having high sorption affinity and low economic cost to be used in recovering the selected contaminants from radioactive waste solutions. For this objective, the samples considered are two types of unmodified clay samples (one from South-West of Allamine, Egypt and has a notation S1 and the second from Baharia oasis, Egypt and has a notation S2) and a commercial activated granular carbon sample (from Aldrich company, and has a notation of S3). The other objective is devoted to determine the adsorption capacity of the studied samples to the selected contaminants. This work also is concerned with the sorption behavior of 134Cs, 89Sr, 60Co and phenol onto the samples under various conditions, as well as the characterization of the investigated samples.The experimental results are in the form of batch technique. Column investigations were used to identify the applicability of these sorbents for radioactive waste solutions treatment. The basic methodology used involved making standard solutions; mixing a fixed amount of adsorbent (clay or carbon) with specific volume of solution; and then allowing the mixture to equilibrate for definite time. from the concentration of equilibrium solution and the mother solution the amount adsorbed of the contaminant can be determined. This thesis consists of three chapters summarized as follows:- Chapter (I) This chapter comprises a review on the major groups commonly found in clay minerals especially aluminosilicates, oxides and organic matter. It deals with the electrochemical properties of clay-surface such as permanent charge, variable charge and point of zero charge as well as short account about specific surface area and surface charge of clay. Activated carbon is one of carbonaceous materials so in this chapter the light focused on the origin, sources, surface area, and surface chemistry of activated carbon as well as its importance. Due to the importance of liquid to solid ratio (V/m) for determining the extent of the interaction of two phases, a brief dissection dealing with it has been included. The chapter contains also a brief account on the sorption phenomena, kinds of adsorption, adsorption isotherms and adsorption characteristics (evaluation of the adsorption and quantitative descriptions of adsorption). Finally; it has a short account about nuclear, chemical and environmental characteristics of the considered contaminants. Chapter (II) This chapter contains a detailed description of chemicals, sampling and the instrumentation utilized in this work. It deals with collection and preparation of the investigated samples (S1, S2 and S3), in addition to preparation and characterization of the contaminants (134Cs, 89Sr, 60Co and phenol). It includes the experimental techniques used in sorption of the representative contaminants onto the considered samples and the factors affecting sorption process. Finally, it includes short notes about desorption study of the contaminants from the loaded samples and short notes about column technique investigations. Chapter (III), result and discussions:
This chapter reveals the experimental results of some physical and chemical characteristics of the studied samples (S1, S2 and S3) as well as the mineralogical composition of the investigated clays. It includes the experimental results of sorption affinity of sorbents to the considered contaminants (134Cs, 89Sr, 60Co and phenol) at different conditions. Also, it has the desorption results of the selected contaminants loaded on the studied samples. Finally this chapter includes the experimental results obtained from column investigations. The experimental results can be summarized as follows:-Some properties of the studied samples are as follows:-
- The moisture content (in percent) of the sorbent samples is 4.5%, 5.1% and 1.3% for S1, S2 and S3, respectively.
- Specific surface area of sorbent samples is 407 m2 g-1, 350 m2 g-1 and 610 m2 g-1 for S1, S2 and S3, respectively. - Point of zero charge (PZC) of the sorbent samples of S1, S2 and S3 is 5.8, 6.2 and 6.5, respectively, and this means that their surface will therefore be negatively charged and have an electrostatic affinity for Cs+, Co2+, and Sr2+ from aqueous solutions when the pH of the ambient solution is greater than estimated value of the sorbent.
- The total exchangeable metallic cations (TEMC) of S1and S2 are 95 (meq/100g) and 41 (meq/100g), respectively.- The mineralogical composition of the investigated clay samples obtained from X-ray diffraction (XRD) reveals that the S1 has smectite as a predominant mineral and the mixed layer of illite/smectite as the most abundant. S1 has a small fraction of gypsum. Moreover, S2 has siderite and feldspars as well as calcite as abundant minerals. Kaolinite, calcite and dolomite are present in S2.