| Summary: | 碩士 === 中原大學 === 化學工程研究所 === 105 === In this study, a novel polyimide (PI) tubular membrane with bi-continuous morphology was fabricated by membrane morphology design. The polyamide (PA) / PI composite tubular membrane then was prepared by interfacial polymerization for nanofiltration.
The effects of poly (vinyl pyrrolidone) (PVP) pore-forming agents on the morphology of PI tubular membranes were investigated. The results show that with the increase of the molecular weight of PVP, the viscosity of the casting solution also increases, and the membrane formation rate can be reduced, resulting in a surface with more pores. In addition, the pore-forming effect of PVP can increase the pure water flux of PI tubular membrane to 30 L/m2h, which is 2 times that of PI tubular membrane without PVP.
The effects of acetic acid (AA) addition on the morphology of PI tubular membranes were also investigated. Because of the hydrogen bond between AA and PVP/NMP, the formation rate of membrane decreases due to the increase of the viscosity of the casting solution, thereby the surface pore of the membrane is bigger and forms bi-continuous morphology in the cross section of PI tubular membrane. When 10 wt.% acetic acid was added to the casting solution, the PI tubular membrane was an entire bi-continuous morphology with a water flux of 80.90 LMH at 4 bar. It was also found that the thickness of the PI tubular membrane almost did not affect the membrane morphology but could improve the rejection.
In order to enhance the nanofiltration performances of PI tubular membrane, the PI tubular membrane with bi-continuous morphology which was fabricated by using (15 wt.% PI + 4 wt.% PVP360k + 10 wt.% AA) / NMP casting solution was used to prepare PA/PI composite tubular nanofiltration membrane via interfacial polymerization by using piperazine (PIP) and trimesoyl chloride (TMC) as the monomers. The resulted PA / PI composite tubular membrane had a rejection of 80% and 20% for Na2SO4 solution and NaCl solution, respectively, while the rejection for Brilliant Blue R dye solution was 98%, indicating that the PA/PI composite tubular membrane had a good potential in the application of dye purification.
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