| Membrane separation technique has been largely used in many fields as an integrate process of separation, concentration, purification, and depuration. Especially in water treatment and related fields, it is working for solving the problems of worsening conditions of water shortage and pollution, and has been playing a greater role. Most of the current membrane technologies, such as MF, UF, NF and RO, are pressure driven membrane processes. They occupy the main membrane market. Some kinds of new membrane technologies are emerging, and are under development. Forward osmosis (FO), deserved many focuses and researches, is an osmotically driven membrane technology, and it has many applications with broad prospect.In the present research, depending on the FO trial platform: firstly, we selected the typical draw solutes, and their osmotic pressure properties were analyzed by the OLI system; Secondly, the basic principles of FO process, were studied by using commercial RO ane FO membrane. Compared with the PRO mode, FO mode has poorer performance. We speculated that the holes of the membrane were blocked because the reverse diffused solutes entered the loose backing part of the membrane. however it is generally believed that this phenomenon is due to the dilute inner concentration polarization.Based on the previous work about the FO properties, FO membrane were prepared, and the membrane properties and structure were characterized. CA were chosen as the membrane material, and the membrane preparation depended on the immersion-precipitation phase inversion methods. DMAc, polar organic solvent, acetone, fine solvent for CA, dioxane, fine solvent for CTA, were selected. The experimental results show that, FO membrane, DMAc as solvent, is too loose; Dioxane as solvent, keep nice water flux and solute rejection; Acetone as solvent, get higher solute rejection, even at low polymer content, but low water flux. Then, we added some organic additives in the membane casting solutions, for changing the solution mobility, membrane structure and performance. Addition of TEP can increase the FO water flux; Addition of formamide can also increase the water flux, but the salt reversion get worse; The addition of methanol can make the membrane denser.Because the sole solvent can not make both high water flux and solute rejection membrane, and for adding alloy polymer, we studied the prepared membrane propreties by mixing solvents. The FO membrane, prepared by the mixing solvents, dioxane and DMAc, can get a controlled water flux and rejection, at degree; Dioxane and acetone, can get a better solute rejection, and have a good permeability. Then, we investigated the membrane structure and performance variation by the organic additives, which were mixed in the mixing solvents. The trial results show that, TEP can improve the membrane permeability; Formamide can change the membrane water flux, but with lower solute rejection. The FO membrane, based on the optimized solvents formula,"dioxane, and DMAc or acetone as the mixing solvents", can get a good water flux with certain solutes rejection, and it can be a promising candidate for membrane improving research.At last, we compared the commercial FO and RO membrane, and the prepared optimized FO membrane, for seawater and brackish water desalination simulation tests. The results show that, the optimized FO membrane, have a good water flux and solute rejection, which can approach the HTI FO membrane performance. During the FO process, 1.5M sucrose as draw soulution, 0.5M NaCl as the simulated seawater, the water flux can get 3L/(m~2·h) around, and the salt permeable flux keep lower than 1g/(m~2·h); for 8000mg/L NaCl as the simulated brackish water, water flux can reach 4.5L/(m~2·h), and the salt permeable flux can keep around 1g/(m~2·h). Preliminary results showed that, our opitimized FO membrane, with a bright prospect, can reach or even surpass the commercial FO membrane, by modification study and preparation technology improving.
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