الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Improved water supply and sanitation, plus better management of water resources, can boost countries’ economic growth and contribute greatly to poverty reduction. As a result, the advancement of water purification and seawater desalination technologies is now critical, not only to combat water pollution but also to combat dangerous climate change. These technologies are basically built on the physical phenomenon ””osmosis.”” The quality of semi-permeable membranes is the principal controlling factor of the osmosis process. Hence the improvement of the membrane`s permeability during or after its fabrication was the aim of this work. The strategy to carry out this improvement was to subject the membranes to some external physical stimuli and record the osmotic water flow rate across the membrane. A special cell for measuring the osmotic flow rate was designed and assembled. The membranes used in this work were cast from solutions of cellulose acetate (CA), cellulose triacetate (CTA), and commercial thin film composite (TFC) membranes. A single-draw solution was used in this work; it consists of 10% by weight NaCl in distilled water. The applied stimuli were: casting membranes in a hot environment; thermal annealing of prefabricated membranes; freezing of wet membranes; casting membranes in a strong magnetic field; irradiation of prefabricated membranes by C-band ultraviolet (UV) radiation; and soaking prefabricated membranes in a strong acidic solution and a strong alkaline solution. It was found that CA membranes casted at 170 oC show improved osmotic flow rate and improved tensile strength, while CTA membranes casted at 200 oC show a good osmotic flow rate and good mechanical strength. The annealing technique destroyed the osmotic flow rate across all types of used membranes, but at the same time it improved the mechanical strength dramatically. Freezing wet membranes improved both flow rate and mechanical strength in all types of used membranes. Membranes that are cast in a magnetic field show improved flow rate but decreased mechanical strength. Irradiated CA, CTA, and TFC membranes exhibit satisfactory improvements in flow rate after 1.5 hours of irradiation time, but CA and CTA exhibit excellent mechanical improvement after 1 hour of irradiation time, whereas TFC exhibits poor mechanical strength due to the irradiation process. Chemical treatments with acidic and alkaline solutions reduced the mechanical strength and increased the flow rate, with limited values for all types of membranes. Hence, if a target was to modify a prefabricated membrane, one should select the adequate stimulus that causes the most required effects. For example, in applications involving forward osmosis, a higher flow rate is more required than high mechanical strength, while in applications involving reverse osmosis, the highest mechanical strength is more required than the flow rate, and so on.