Preparation Of Sulfonated Polyethersulfone(SPES) Thin Film Composite Forward-osmosis Membranes And Study On Its Properties

Forward osmosis(FO) membrane separation technology for its no external pressure-driven, low power, low cost, high recovery, anti-fouling etc. has become a hot research field of membrane separation technology, it shows a good application prospects in various field, and gets a degree of engineering application. However, there are still restrictions that limit its development, these limitations mainly related to the following aspects: First of all,there are no draw solutes/solution that can be conveniently and economically concentrated or recycled. Second, serious membrane concentration polarization inside and outside. Back diffusion of solute is also not a negligible issue.But the core problem is that there is no suitable FO membrane, therefore, the preparation of high-performance FO membrane is very necessary, this paper focused on the effects of preparation conditions of the support layer and polyamide separation layer for the performance of sulfonated polyethersulfone forward osmosis thin film composite membrane(SPES-FO membrane),and also studied the effect of operating conditions to enhance SPES-FO membrane performance.This paper used immersion precipitation phase inversion to prepare the support layer of SPES-FO membrane to focuse on the method of preparing sulfonated polyethersulfone support layer and its influencing factors. influence of mass concentration of polyethersulfone and pore agent and sulfonation of sulfonated polyethersulfone in casting solution,and the thickness of casting solution film on the formation of the support layer structure were studied respectively. The optimum conditions are as follows: the support layer casting solution obtained in accordance with the polymer concentration of 16%, pore agent concentration of 10%, sulfonation of sulfonated polyethersulfone of 6%, and the thickness of casting solution film was 120 μm. Under such conditions, the SPES-FO membrane reached its largest pure water flux,Na Cl backmixing flux was Relatively low.Interfacial polymerization over the sulfonated polyethersulfone support layer were carried out in a homemade frame to prepare active layer.Influence of structural changes of active layer under different conditions of interfacial polymerization on the change of pure water flux and Na Cl Backmixing flux of SPES-FO membrane were studied respectively.The results showed that the optimum interfacial polymerization curing time is 30 s, the optimum curing temperature is 80℃, the optimum curing time is 1 min.if backmixing flux of Na Cl is not particularly demanding, water flux of SPES-FO membrane reached its highest without heat treatment, Na Cl backmixing Flux can also reaches the ideal level of value. After interfacial polymerization with the aqueous phase solution adjusted to the alkaline, SPES-FO membrane performance face great decline.Performance tests of SPES-FO membrane were carried out under the conditions of different temperatures and velocities of cross-flow and different Na Cl concentrations to optimize operating conditions for forward osmosis membrane separation process. Research showed that improving the temperature and velocity of cross-flow are conducive to slow down the concentration polarization of SPES-FO membrane, increasing the Na Cl concentration although to some extent exacerbated the membrane ICP, but it indeed can enhance film water flux, Na Cl backmixing flux were also increase. In FO mode, dilutive ICP occured within the support layer was the main factor affecting film performances; in PRO mode, dilutive CP occured near the active layer was the main factor affecting film performances.