الفهرس 
FORWARD OSMOSISOnly 14 pages are availabe for public view
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Abstract
Nowadays, the world is seeking energy-efficient desalination technologies to provide fresh water with lower energy consumption and, hence, a lower cost of production. Forward Osmosis (FO) is a developing membrane-based desalination process that uses natural osmotic pressure as the driving force to transfer clean water through a semipermeable membrane between a draw solution (DS) with high osmotic pressure and a feed solution (FS) with low osmotic pressure. There are multiple draw agents that were examined for FO desalination. However, hydrogels that are defined as three-dimensional network structures are distinguished from all other draw agents by their finite reverse solute flux. The main purpose of the present thesis is to synthesize two different types of novel hydrogels: SA/PVA bioartificial hydrogel from a polymer blend of sodium alginate (SA) and polyvinyl alcohol (PVA) using epichlorohydrin (ECH) as a crosslinker, and SA/FG/PEG green hydrogel from the crosslinking of sodium alginate (SA) and flaxseed gum (FG) using ECH as a crosslinker and polyethylene glycol (PEG) as a semi-interpenetrating network polymer. Then, the impact of different polymer contents in the polymer blend and the variation of crosslinking dose on the swelling capacity of both hydrogels was studied. In addition, the effect of the addition of semiinterpenetrating network polymer with different mass ratios on the response of SA/FG/PEG hydrogel was investigated. The optimized composition of both hydrogels from swelling measurements was characterized using FTIR, XRD, SEM, and compression tests. The performance of both optimized hydrogels as draw agents in the FO batch unit was examined. The water flux and the reverse solute flux were measured under the effect of different parameters such as average hydrogel particle size, feed solution temperature, feed solution concentration, and membrane orientation. The swelling measurements revealed that the maximum swelling ratio (SR) (%) after 1 hour and equilibrium swelling ratio (ESR) (%) of 645.42 and 5228, respectively, were achieved with the optimum SA/PVA hydrogel, which has 25% PVA by mass and a crosslinker/total polymer mass ratio of 0.8. Whereas the optimal (SA/FG/PEG) hydrogel of 0.3 PEG/total polymer blend mass ratio, 12% flaxseed gum, and 0.95 ECH/total polymer blend mass ratio exhibited a SR (%) of 1800 after an hour and an ESR (%) of 5300. In addition, from FO experiments, the highest water flux achieved by the optimum SA/PVA hydrogel was 0.845 LMH when distilled water at 40°C, was used as a feed solution, with an average hydrogel particle size of 60 µm. While the maximum water flux accomplished by the optimum SA/FG/PEG hydrogel was 1.27 LMH when the average hydrogel particle size was 112.5 µm and distilled water at 35°C was the feed solution. III Real brackish water from two distinct wells with total dissolved solids of 1160.8 and 1633.16 ppm was desalinated by this FO batch system based on the optimal FO process conditions, employing each hydrogel as a draw agent. The results revealed that water fluxes of 0.21 and 0.34 LMH with the optimized SA/PVA hydrogel and 0.254 and 0.27 LMH with the optimum SA/FG/PEG hydrogel were achieved, respectively. Moreover, it was necessary to note that the reverse solute flux in all FO experiments was negligible.