الفهرس 
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Abstract
This chapter presents a brief introduction about the nano-materials and nano-technology in water treatment, and the applications in water treatment of toxic pollutants especially the heavy metals due to their toxicity, carcinogenic and harmful effects on the surrounding environment. This chapter provides also the properties and classifications as well as presents examples of nano-sized metal oxides (NMOs) such as ferric oxides, manganese oxides, titanium oxides, zinc oxides, magnesium oxides, cerium oxides and silica nano-particles. This chapter presents also some details about the general physicochemical, thermal, mechanical and optical properties. The different methods of synthesis of silica nano-particles and their surface modification by chemical reactions are also covered in this chapter.
The analytical applications, as well as other application fields of modified nano-silica and silica nano-tubes (SiO2NTs), are also included in this chapter. In addition, the favorable properties of nano-silica as an efficient sorbent as well as solid support and different functionalization of its porous surface are also included.
The second chapter: Experimental
This chapter describes the experimental section including different instrumentation used in this thesis such as scanning electron microscope (SEM), high resolution-transmission electron microscope (HR-TEM), Fourier transform infrared (FT-IR), thermal gravimetric analysis (TGA), pH-meter and atomic absorption spectroscopy (AAS). Chemical, solutions and different titrimetric techniques used for determination of metal ions are also presented. Finally, the immobilization procedures of carboxylic acids such as citric, oxalic and tartaric on the surface of activated nano-silica sorbent was successfully achieved using microwave assisted technique to develop three novel nano-silica sorbents N-Si-Cit, N-Si-Ox and N-Si-Tar, respectively.
The third chapter: Results and Discussion
The third chapter demonstrates the results and applications of these designed nano-silica sorbents for extraction of some selected heavy metal ions.
This Chapter is divided into several main sections:
The first section presents the surface modification and characterization of all nano-silica sorbents using instrumental and surface techniques such as FT-IR, TGA, SEM and HR-TEM. The results collected from these techniques confirmed the surface functionalization of nano-silica sorbents with the target acid functional groups. The shape and particle size of the modified nano-silica sorbents were also identified from the SEM and HR-TEM images. Nano-silica sorbents exhibited a mean diameter of 18–24 nm and after the modification processes, the functionalized nano-sorbents were identified in the range of 22–51 nm range.
The second section of this chapter displays the results and discussion of sorption studies on the selected metal ions and the application of the functionalized nano-silica sorbents for extraction of metal ions from different samples. All sorbents exhibited efficient sorption capacity for removal of metal ions with fast equilibration time and the data are described by both Langmuir and Freundlich models. This is mainly divided into three main parts.
The first part describes the optimization conditions for removal of Mg(II) and Ca(II) from aqueous solutions and the maximum sorption capacity values were established at pH 7.0 by all nano-silica sorbents according to the following orders:
For Mg(II) and Ca(II): N-Si-Tar ≈ N-Si-Cit ≈N-Si- Ox > N-Si
In addition, the applications of these nano-silica sorbents for water softening and treatment from Mg(II) and Ca(II) were also accomplished using seawater samples that are originally containing 1278.9 and 385.5 mg L-1 of both metal ions, respectively. Excellent percentage removal values of these two metal ions from sea water were accomplished as listed in the following Table.
The second part involves the sorption processes of Fe(III) and Co(II) from various water matrices by all nano-silica sorbents. The results of this study confirmed that Fe(III) was efficiently and selectively extracted at pH 4.0, while the optimum pH value for sorption of Co(II) by all sorbents was observed at pH 6.0. In addition, the applications of nano-silica sorbents-functionalized-carboxylic acids for water treatment from these two metal ions were also performed and accomplished.
The third part involves the sorption studies of Pb(II) and Cd(II) and the results were found to refer that all nano-silica sorbents exhibited maximum cadmium at pH 7.0 as listed in the following Table, while that for lead sorption capacity values (μmol g-1) at pH 4.0.
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