الفهرس 
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Abstract
The increasing concern towards protection of the environment and optimization of a wide range of activities in nuclear field imposes the need for the development of advanced separation processes in particular for treatment of liquid wastes. But, applying the traditional treatment processes is challenged by the coexistence of cationic and anionic (radio)toxicants in liquid wastes, where multi- treatment processes and/or multi-steps are required to treat such wastes. Accordingly, the time and cost of the treatment process are increased. A one-step treatment process is therefore necessary to avoid such drawbacks.
The work presented in this thesis addressed the above objective through synthesizing two novel polyacrylonitrile (PAN)-based polymeric adsorbents and evaluating their adsorbability towards two adsorbate systems (134Cs+ cations/HCrO - anions and 60Co2+ cations/MnO - anions). The thesis comprises four chapters which are summarized below.
CHAPTER I: Introduction
The aim of this first chapter is to give an overview of:
(i) The conventional treatment technologies: basic concepts, advantages and disadvantages,
(ii) Adsorption: definitions and terminology, adsorption steps, adsorption operation modes, categorization of adsorbents, categories of adsorption isotherms, surface-complexes, adsorbent materials and adsorbent selection,
(iii) Polyacrylonitrile: synthesis, properties and activation methods (functionalization, nitrile conversion, copolymerization and composite formation),
(iv) Past work reported on simultaneous removal of cationic and anionic (radio)toxicants.
A number of other topics are also introduced and discussed.
CHAPTER II: Experimental
This chapter introduces the reagents, apparatus, general procedure of adsorption, adsorbents synthesis, …etc., used in the present work:
(i) Reagents: polyacrylonitrile (PAN), copper chloride, cetrimonium bromide and potassium ferrocyanides which are used for synthesis of the applied adsorbents. Radioisotopes preparation and other many reagents that are used in the thesis are also included in this chapter,
(ii) Instruments and equipments: this includes the apparatus used either during synthesis of the adsorbents or performing the adsorption experiments (pH-meter, magnetic stirrer, digital balance, water-bath shaker, …etc.) together with those used for characterization of the adsorbents (Fourier-transformed infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TGA)) and analysis of the adsorbates (single-channel analyser and UV-visible spectrophotometer).
(iii) General procedures for adsorption and desorption processes performed in the present work,
(iv) Synthesis methods of the adsorbents (polyacrylonitrile (PAN), potassium copper ferrocyanide (KCuFC), potassium copper hexacyanoferrate III (KCuHCF), PFICB and PAN/CB/KCuHCF),
(v) Radiometric and spectrophotometric analysis of 134Cs+/60Co2+ and HCrO4-/MnO4-, respectively, and
(vi) Determination of the adsorption efficiency methods and data presentation.
CHAPTER III
Synthesis of Polyacrylonitrile/ferrocyanide composite incorporated with cetrimonium bromide and its employment as a bifunctional adsorbent for coremoval of Cs+ and HCrO - from aqueous solutions
The presence of cationic (radio)toxicants together with the anionic ones in liquid wastes is concerned a major environmental concern. To properly decontaminate of such wastes, both cationic and anionic (radio)toxicants must be removed. In most cases, treatment of such wastes is governed by using multi- treatment processes and/or multi-steps which decreases the efficiency of the treatment process. Therefore, it is of major importance to remove the cationic and anionic (radio)toxicants by using a one-step treatment process.
This study has, therefore, been performed to explore the feasibility of a polyacrylonitrile (PAN)-based polymeric composite (PAN/ferrocyanide composite incorporated with cetrimonium bromide (PFICB)) for simultaneous removal of 134Cs+ cations and HCrO4-, one of Cr(VI) species, anions from aqueous solutions. PAN, potassium copper ferrocyanide (KCuFC) and PFICB particles were characterized by Fourier-transformed infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscope (SEM) techniques. characterization results and the data of adsorption and adsorption studies are summarized in the following points.
• Characterization of the materials by FT-IR and XRD techniques clarified that peaks of PAN and KCuFC are coexisted in the spectra (in case of FT-IR) and pattern (in case of XRD) of PFICB. These findings confirmed the formation of PFICB particles. Formation of PFICB particles was further
confirmed by SEM analysis. The SEM image of PAN showed the formation of relatively uniform and thin sheets, while KCuFC particles were thick with larger size. But, PFICB image indicated the existence of homogeneous aggregates of fine particles. Eventually, the TGA data showed that the synthesized PFICB composite exhibited a satisfactory thermal stability.
• Adsorption kinetics data of cesium at different pH values indicated that changing the solution pH slightly affected the removal percentage of cesium, while had no effect on its equilibrium time. For hexavalent chromium, increasing the solution pH from 3.4 to 9.5 increased the equilibrium time from 5 to 60 min while decreased the removal percentage from 88.2 to 59.3%. At different initial adsorbates concentration, the obtained kinetic data showed that the equilibrium time of Cs(I) and Cr(VI) ions is unaffected, whereas the removal percentage is deleteriously affected by increasing the initial concentration of the studied adsorbates. The fast adsorption kinetics of cesium cations, Cs+, and chromium (VI) anions, HCrO4- and/or CrO42-, revealed the physisorption process of these species onto PFICB.
• The pseudo-first-order and pseudo-second-order kinetic models are utilized to analyse the adsorption kinetic data of cesium and chromium at the studied conditions and the results indicated that the later model is better than the former one.
• The variation of the removal percentage and the adsorbed amount of Cs+ and HCrO4- with mass of PFICB in the range 1 – 20 g/L is studied at pH 3.4. It is found that, the removal percentage is increased from 28.2 to 97.2% (for Cs+) and from 18.1 to 89.6% (for HCrO4-) with increasing the mass of PFICB from 1 to 10 g/L. Further increase in the adsorbent mass to 20 g/L giving rise to removal percentages of 98.9 and 91.2% for Cs+ and HCrO4-, respectively. Owing to this slight increase in the removal percentage along
with the economic point of view, the adsorption experiments of Cs+ and HCrO4- were conducted using 10 g/L PFICB.
• The results obtained by the effect of the solution pH in the range of 2.5 – 10 on the removal of Cs(I) and Cr(VI) ions by PFICB represented that the efficiency of the present adsorption processes are obviously dependent on the adsorbent mass. At 10 g/L PFICB, the removal percentage of Cs(I) is increased from 45.7 to ˃ 99% with increasing the solution pH from 2.5 to 3.4, which remained unchanged up to pH 10.1. While 95% of Cr(VI) ions are removed at pH values ≤ 3 which decreased with increasing the solution pH and reached to 61.2% at pH 10.1. The reduction in the removal percentages of cesium (at pHs below 3.5) and chromium (at pHs beyond 3) is avoided by increasing the adsorbent dosage to 20 g/L. But, from the economic and waste management points of view, the lower adsorbent mass (PFICB= 10 g/L) was chosen for the present adsorption process.
• Adsorption processes of Cs+ cations and HCrO4- anions, at pH 3.5, onto PFICB are found to be unaffected by the temperature in the range 15 – 45 oC, which suggested that the concerned adsorption processes are governed by physical adsorption. The calculated values of the free energy change (∆Go) are found to be -13.49, -14.02, -14.35 and -14.63 KJ/mol (for Cs+) and -12.94, -13.31, -13.64 and -14.32 KJ/mol (for HCrO4-) at temperatures of 15, 25, 35 and 45 oC, respectively, which confirmed that adsorption of the studied (radio)toxicants onto PFICB is achieved by physical adsorption.
• By increasing the initial concentration of cesium from 10 to 750 mg/L and that of chromium from 10 to 500 mg/L, the removal percentage is decreased from 98.6 to 49.3% (for Cs+) and from 78.2 to 33.7% (for HCrO4-), while the adsorbed amount is increased and reached to 36.98 mg/g (for Cs+) and 16.83
mg/g (for HCrO4-). Based on the results of the effect of the initial adsorbates concentrations on their adsorbed amounts, the adsorption isotherms of Cs+ and HCrO4- are constructed to which Freundlich and Langmuir isotherm models are fitted. The results showed that Freundlich model exhibited higher correlation coefficient (R2= 0.9939 for Cs+ and 0.9552 for HCrO4-) than Langmuir model (R2= 0.9433 for Cs+ and 0.8586 for HCrO4-). Accordingly, it is concluded that Freundlich model was better than Langmuir model for describing the present adsorption processes. This finding is confirmed by fitting the experimental adsorption isotherms of Cs+ and HCrO4- to Langmuir-Freundlich isotherm model, where very small KLF values are obtained (KLF= 6.6×10-4 for Cs+ and 8.8×10-4 for HCrO4-) which implied that Langmuir-Freundlich model is transformed to Freundlich model. According to Langmuir-Freundlich model, the synthesized PFICB adsorbent exhibited maximum adsorption capacities of 41.79 mg/g (for Cs+) and 19.39 mg/g (for HCrO4-) which are found to be comparable with those reported in literature for these (radio)toxicants using other adsorbents.
• Except for NH4+ ion, adsorption efficiency of Cs+ onto PFICB is mostly unaffected by the coexistence of high concentration (3 mol/L) of foreign cations (K+, Na+, Ca2+, Mg2+ or Al3+). For NH + ion, the results demonstrated that this cation had no effect on the removal percentage of Cs+ up to
0.1 mol/L while deleteriously affected the adsorption process at higher values and only 49.7% of Cs+ ions are removed at 3 mol/L NH4+. On the other hand, the removal percentage of HCrO4- is slightly affected by the coexistence of other anions (Cl-, NO3-, CO32-, SO42- or PO43-) particularly at concentrations higher than 0.1 mol/L. The data obtained by the effect of coexistence of foreign ions on the present adsorption processes reflected the high efficiency of the synthesized PFICB adsorbent for simultaneous
removal of Cs+ and HCrO4- even in presence of high concentration of background electrolytes.
• Desorption studies of Cs+ and HCrO4- loaded onto PFICB showed that most of the studied desorbing agents ((NH4)2SO4, NaCl, KNO3, CaCl2 or Al(NO3)3) failed to desorb Cs+ ion in the studied concentration range of
0.001 – 0.1 mol/L. By using HCl, maximum desorption percentage of about 52% is obtained at concentrations ≥ 0.25 mol/L. On the other hand, the maximum desorption percentage, " ~ " 72%, of HCrO - is achieved by using Al(NO3)3 at concentrations ≥ 0.25 mol/L. Consequently, it is concluded that PFICB removed Cs+ ion by chemisorption, whereas, physisorption was predominant removal of HCrO - .
This summary for the obtained results reported in the present thesis clearly demonstrates that the synthesized PFICB composite efficiently succeeded to simultaneously remove 134Cs+ cations and HCrO - anions from aqueous solutions. Herein, PFICB can be considered a promising adsorbent for simultaneous removal of cationic and anionic (radio)toxicants from liquid wastes.
CHAPTER VI
Efficient removal of radiocobalt and manganese from their binary aqueous solutions by batch adsorption process using
PAN/CB/KCuHCF composite
This chapter deals with the utilization of polyacrylonitrile/cetrimonium bromide/potassium copper hexacyanoferrate III (PAN/CB/KCuHCF) composite, synthesized by a different method to that used in chapter III, as a novel adsorbent for removal of 60Co2+ cations (one of radiocobalt species) and MnO4- (one of manganese (VII) species) from their binary aqueous solutions. The synthesized adsorbent was firstly characterized and followed by its employment as an
adsorbent for conducting the adsorption experiments of cobalt and manganese at different parameters and the data obtained are outlined as follow.
• Characterization by FT-IR technique showed that the characteristic absorption peaks of PAN and KCuHCF are coexisted in the spectrum of PAN/CB/KCuHCF composite, which indicated the formation of the concerned composite. Similarly, the characteristic diffraction peaks of PAN observed at 2θ of 17.1o, 29.8o and those obtained for KCuHCF at 2θ of 17.5o, 24.9o, 35.8o, 39.9o, 43.9o, 51.3o, 54.7o and 57.8o are coexisted in the XRD pattern of PAN/CB/KCuHCF. This finding is considered as a further evidence in the formation of the synthesized composite. characterization by TGA pointed out that PAN/CB/KCuHCF could be effectively applied as an adsorbent at temperature below 200 oC, where decomposition of the composite is observed at higher temperatures.
• By using 1 g/L PAN/CB/KCuHCF, the results of the effect of the solution pH in the range 1.5 – 7.8 revealed that almost complete removals are attained for cobalt at pH values ≥ 3.3, while maximum adsorption percentage of 76% is achieved for manganese at pH values below 3.3. By increasing the adsorbent dosage to 4 g/L, the removal percentage of cobalt at the studied pH range is slightly affected, while 99.5% of manganese ions are removed in the pH range 1.5 – 7.8. Adsorption of cobalt onto PAN/CB/KCuHCF composite at pH < 6 is attributed to the ion exchange of Co2+, the predominant species of cobalt at these pHs, with K+ and/or Cu2+ ions at the adsorbent surface. While ion exchange of MnO4-, the predominant species of manganese (VII), with the surfactant (CB) counter anion (Br-) at the composite is considered the main reason for adsorption of manganese onto PAN/CB/KCuHCF.
• Both the removal percentage and the adsorbed amounts of the studied (radio)toxicants are obviously dependent on the dosage of PAN/CB/KCuHCF composite. Increasing the adsorbent dosage increased the removal percentage that reached to 99% using 1.5 and 3 g/L for cobalt and manganese, respectively. On the other hand, the adsorbed amount is decreased from 99.3 to 39.1 mg/g (for cobalt) and from 27.8 to 7.9 mg/g (for manganese) as the adsorbent dosage increased from 1 to 4 g/L.
• The effect of contact time on the removal percentage of the studied adsorbate concentrations (30 and 60 mg/L for cobalt and 55 and 137 mg/L for manganese) at pH 3.5 showed that " ~ " 100% (of cobalt) and 70% (of manganese) are uptaken by PAN/CB/KCuHCF in the first minute. Three extensively used kinetic models, namely, Lagergren-first-order, pseudo- second-order and Elovich, are applied to fit the obtained kinetic data of manganese. The kinetic data of cobalt could not be kinetically modelled where its adsorption onto PAN/CB/KCuHCF was a very fast process as the equilibrium is attained in the first minute. By comparing the correlation coefficient (R2) values of the aforementioned kinetic models, it is found that the pseudo-second-order model exhibited higher values (R2= 0.999 for the studied concentrations) than Lagergren-first-order (R2= 0.937 and 0.963) and the Elovich model (R2= 0.941 and 0.918) for 55 and 137 mg/L manganese, respectively. Accordingly, it is deduced that pseudo-second- order is the best kinetic model for describing the adsorption kinetic data of manganese onto PAN/CB/KCuHCF composite.
• To discriminate between film diffusion and pore diffusion mechanisms, adsorption kinetic data of manganese onto PAN/CB/KCuHCF was further analysed by Weber-Morris and Boyd kinetic models. The unsatisfactory correlation coefficients (R2= 0.919 for 55 mg/L and 0.877 for 137 mg/L) and
the non-zero intercept of the Boyd plots (intercept= 0.694 for 55 mg/L and
1.131 for 137 mg/L) suggested that adsorption process of manganese onto PAN/CB/KCuHCF composite is controlled by film diffusion.
• Plots of ln Kd versus 1/T for the studied adsorption processes in the temperature range 25 – 60 oC resulted into straight lines with high correlation coefficients (R2= 0.965 for cobalt and 0.973 for manganese). The positive values of the enthalpy change (∆Ho), calculated from the slope of the plots, suggested that adsorption of cobalt and manganese onto PAN/CB/KCuHCF composite were endothermic processes. While the positive values of entropy change (∆So), calculated from the intercept of the plots, indicated the increase of randomness at the solid-liquid interface. The negative values of free energy change (∆Go) suggested that the present adsorption processes were spontaneous.
• Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin adsorption isotherm models are applied to analyze the adsorption isotherms of cobalt and manganese onto PAN/CB/KCuHCF composite. According to R2 values of plots, it is concluded that Freundlich and Langmuir isotherm models are the best models for fitting the adsorption isotherms of cobalt and manganese, respectively, which suggested that cobalt ions are physisorbed onto PAN/CB/KCuHCF while manganese ions are chemisorbed.
• Desorption results of cobalt and manganese ions loaded onto PAN/CB/KCuHCF composite at different concentrations of (NH4)2SO4, CaCl2, Al(NO3)3, HCl, and Na2HPO4 demonstrated that maximum desorption percentage of 76% is achieved for cobalt using HCl. While the studied desorbing agents had no ability to desorb manganese loaded onto PAN/CB/KCuHCF. Herein, it is deduced that manganese ion is strongly bound to PAN/CB/KCuHCF composite than cobalt ion.
Accordingly, it can be concluded that PAN/CB/KCuHCF composite had the ability to remove cobalt and manganese from their binary aqueous solutions and thus its potential application for treatment of liquid wastes contaminated with cationic and anionic (radio)toxicants.