الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 195 |  |  |
| | | from | 195 | | |
Abstract
Nowadays, lack of clean and soft drinking water is one of the major problems faced by human society. Membrane-based separation is one of the most popular technologies for water reuse and desalination of brackish/ saltwater. Membrane-based separation became a suitable alternative to thermal separation techniques. Although the reverse osmosis (RO) process has substituted the routine thermal distillation process as the prevailing desalination technology after 40 years of development, the dramatic rise in oil prices has affected its potential for water softening. Since high hydraulic pressure must be supplied in the RO process to overcome the osmotic pressure of the feed solution, it is not reasonable to use this technique for water treatment processes. Forward osmosis (FO) is a novel membrane process that shows great potential as an alternative to the conventional membrane process. Unlike reverse osmosis (RO) that uses hydraulic pressure to create the driving force for water permeation, FO processes utilize an osmotic pressure difference between the feed and draw solution across a semipermeable membrane as the driving force to persuade the clean water to flow through the membrane to the draw solution. Compared to conventional pressure-driven membrane process such as the RO, the FO has shown many advantages namely:
(1) Reduce fouling tendency and easy cleaning;
(2) Low cost;
(3) Higher water recovery,
(4) More extensive application such as power generation, juice or food concentration, protein, and pharmaceutical enrichment, desalination and wastewater treatment.
The main parts of the present study can be summarized as follows:
Introduction
This chapter includes a general introduction about water scarcity problem in the world and its water resources, identification of desalination process and different desalination techniques, identification of forward osmosis (FO) technique, draw solutions and different types of draw solution used in FO process, properties of membranes used in FO, methods used in the preparation of FO membranes and different nano-materials which were used in this work.
Chapter 2 Literature review
It includes a survey and review of previous work related to the history of forward osmosis, draw solutes used in forward osmosis, and the recovery methods of draw solutes in forward osmosis, membrane modification using nanomaterials, and applications of forward osmosis.
Chapter 3 Material and methods
This chapter presents the important materials that were used in the completion of this work, their properties, and their sources, and also includes a simple explanation of the preparation of a polysulfone substrate and a thin polyamide layer through the IP process, the preparation of a thin modified polyamide layer by different nanomaterials. It also includes important characterization device characteristics used in this work, steps for preparing samples for characterization tests, and simple expression for preparing a unit FO and its various components and schematic diagrams. It also includes how to calculate the water flux, salt rejection, reverse solute, etc.
Chapter 4 Result &discussion
This chapter is divided into two parts:
The first part includes the results of the nanomaterials characterization (XRD- Raman spectroscopy - FTIR – SEM – TEM) which confirmed the crystal structure and phase of nanomaterials.
1. XRD Patterns results illustrated that the 2θ peak can be seen at 10.83° for GO, and a broader peak can be seen for rGO at 2θ = 25.11°. For the multi-wall carbon nanotubes, the XRD pattern shows the intense peak at 2θ = 25.87o. All diffraction peaks of the sample prepared ( TiO2- TiO2/N- TiO2/C) show the complete organization of the anatase phase according to the diffraction peaks at 25.33°, 38.03°, 48.02°, and 53.89° corresponding to lattice planes (101), (004), (200), (105), (333) for anatase structure, respectively.
2. Raman spectrometer results illustrated that the two fundamental vibrations can be observed in the range of 1100 and 1700cm-1 for GO, rGO, and MWCNT. The D vibration band is formed from a breathing mode of j-point photons of A1g symmetry can be seen at 1340.07, 1340.78, and 1327.29 cm-1 for GO, rGO, and MWCNT respectively. On the other hand, the G vibration band from the first-order scattering of E2g phonons by sp2 carbon appeared at 1587.87, 1577.68, and 1573.85 cm-1 for GO, rGO, and MWCNT respectively. TiO2, TiO2/N, and TiO2/C show six Raman active fundamental modes correspondingly at 144cm−1 (Eg), 197cm−1 (Eg), 397cm−1 (B1g), 518 cm−1 (A1g
+ B1g), and 640 cm−1 (Eg) which confirm crystalline anatase TiO2.
3. ATR-FTIR spectrometer results illustrated that TiO2, TiO2/N, and TiO2/C show a strong absorbance band that appeared in the range of 400–700 cm-1. This band is assigned to the stretching vibration of the Ti-O-Ti bond referring to the creation of TiO2. The shift observed in this band confirms the incorporation of the dopants into the TiO2 lattice.
4. Scanning Electron Microscope (SEM), The SEM micrograph of GO shows wrinkled and layered flakes on the surface, while the micrograph of rGO shows that the rGO surface contained crumpled thin sheets which accumulated to form disordered structure material. The micrograph of MWCNTs was shown in
different curvature and length that resemble a gathering of worms. The micrograph of TiO2, TiO2/N, and TiO2/C have rounded shape and form sponge- like aggregates
5. Transmission Electron Microscope (TEM), both GO and r GO appeared as a sheet in morphology with different transparencies and thicknesses. On other hand, the TEM image of MWCNT shows a tubular structure with diameters ranged between 2and 6 nm. TEM image of the TiO2 and TiO2 doped with (N,
C) shows the spherical shape with different particle sizes.
The second part includes the results of characterization of the prepared membrane and modified films using nanomaterials as follows
1. ATR- FTIR spectrometer results illustrated that the characterizing peaks of the PA layer at 1609 cm-1, 1654 cm-1, and 1541 cm-1, which are assigned to the aromatic ring breathing, amide II band (C=O stretching), and amide II band (C– N stretching), respectively. All the TFN membranes contain very similar functional groups, as they all have very similar peaks. This is expected because the chemical compositions of the membranes are nearly the same, however, they contain different concentrations of nanomaterial which apparatus can’t detect as small quantities.
2. Scanning Electron Microscope (SEM), Both the TFC and TFN membranes indicated a ridge-valley-like structure on their surfaces. Detailed observation shows that the TFC membrane presented a more nodular surface relative to the denser structure of TFN membranes.
3. Atomic Force Microscope (AFM), TFC and TFN membranes have the ‘‘ridge- and-valley’’ PA structure distributed throughout the plane. AFM analyses represent that presence of nanomaterials improved the surface deep depression (pores) and nodules. Besides, the roughness of the substrate is assigned to the height of the surface’s lumps.
4. The contact angle was measured for TFC and TFN membranes and experimental results shown that contact angle decrease by the addition of nanomaterials (GO, rGO, MWCNT, TiO2, TiO2/N, and TiO2/C) from 64.8 to
35.9 due to the roughness of the surface and presence of functional groups at nanomaterials.
Chapter 5 Performance
This chapter is divided into four parts:
The first part includes RO experiments, the pure water flux (A), salt permeability (B), and NaCl rejection (R) of TFN membrane increased with the increase of nanomaterials (GO, rGO, MWCNT, TiO2, TiO2/N, and TiO2/C) loadings at different concentration (0.3- 0.5- 0.7- 0.9 w/v). At a certain concentration limit and after that the water flux is reduced due to the nanomaterials accumulating on the surface of the polyamide layer. The optimum concentration for all nanomaterials TFC, TFN-GO 0.7, TFN-rGO 0.5, TFN-MWCNT 0.5, TFN-TiO2 0.7, TFN-TiO2/N 0.7 and TFN-TiO2 /C 0.5.
The second part includes FO experiments, the synthesized TFC and TFN FO (GO, rGO, MWCNT, TiO2, TiO2/N, and TiO2/C) membranes exhibited high water flux in both AL-DS (active layer facing draw solution) and AL-FS (active layer facing feed solution) orientations where FS contained deionized water and DS contained 1M NaCl. Higher water flux is due to the enhancement of hydrophilicity and roughness. While the reverse solute flux in both AL-DS and AL-FS orientations decrease with an increase in the nanomaterials due to the same reason. The optimum concentration for all nanomaterials TFC, TFN-GO 0.7, TFN-rGO 0.5, TFN-MWCNT 0.5, TFN-TiO2 0.7, TFN-TiO2/N 0.7 and
TFN-TiO2 /C 0.5.
The third part includes the effect of the concentration of feed and draw solution. The water flux for TFC and TFN-GO 0.7, TFN-rGO 0.5, TFN-MWCNT 0.5, TFN-TiO2 0.7, TFN-TiO2/N 0.7 and TFN-TiO2 /C 0.5, at different DS concentrations (0.5, 1, 1.5, and 2 M NaCl). Greater DS concentration increased the water flux of both the TFC and TFN membranes due to the larger osmotic driving force available. Both AL-DS and AL-FS orientations of FO membranes were investigated under different feed concentrations (0 - 0.5 M NaCl) and a fixed 1 M NaCl as DS. Water flux of the two FO membranes decreased sharply by increasing FS concentration within 0 -0.1 M NaCl and then decreased slowly as FS concentration over 0.1 M NaCl under AL-DS orientation.
The four-part includes the effect of time. The results indicate that the water flux decreased gradually with time through FO membrane processes via osmotic pressure as the driving power for water flux via the membrane.
Chapter 6 Application
Different types of fertilizer draw solutes include KCl, NH4Cl as monovalent ions, (NH4)2SO4 as divalent cations and dipotassium hydrogen orthophosphate (K2HPO4) as divalent anion using deionized water & 0.1 M NaCl as Feed solution and 1M from each different fertilizer DS. KCl and NH4Cl gave high water flux and high reverse solute flux with all membranes (TFC, TFN-GO 0.7, TFN-rGO 0.5, TFN-MWCNT 0.5, TFN-TiO2 0.7, TFN-TiO2/N 0.7, TFN-TiO2
/C 0.5), due to high osmotic pressure and small ions, but (NH4)2SO4 and (K2HPO4) gave low water flux and low reverse solute flux with all membranes. Application of the TFN-GO 0.7 modified membrane displays the high water flux using the selected natural groundwater sample collected from El Daba`a area, the Northwestern coastal zone of Egypt with salinity 9244 mg/L as FS and 1M of KCl as draw solutions under the FO approach. The results reveal that the water flux of the TFN-GO 0.7 modified membrane showed the water flux
23.94 L/m2.h.