| Summary: | 碩士 === 國立宜蘭大學 === 化學工程與材料工程學系碩士班 === 107 === In this study, the polyamide composite membranes were prepared by using the interfacial polymerization of different amine monomers (trans-2,5-dimethylpiperazine (DMPZ), 2-methylpiperazine (MPZ), and piperazine (PIP)) with acyl chloride monomer trimesoyl chloride (TMC) on the surface of asymmetric polysulfone (PSf) support membrane. These composite membranes were applied to the forward osmosis to separate aqueous salt solution. To improve membrane flux, the asymmetric porous PSf support membranes were fabricated by adding PEG20000 as pore forming agent. The effects of pore forming agent content in the casting solution, amine monomer chemical structure, and polymerization conditions (the monomer concentrations of aqueous and organic solutions, immersion time of aqueous amine solution, and polymerization time) on the forward osmosis performance through the polyamide composite membranes were investigated. To improve membrane forward osmosis performance, the different surfactants were added in aqueous solution. The effects of the concentration and charge property of surfactant were investigated. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was used to characterize the chemical structure of composite membrane. Water contact angle measurements were used to analyze the hydrophilicity of composite membrane. Scanning electron microscope (SEM) was used to observe the morphology of membrane. Atomic force microscope (AFM) was used to observe the roughness of membrane surface.
The addition of pore forming agent causes a variation in the morphology of asymmetric PSf support membrane and influences the forward osmosis performance of polyamide composite membrane. The best concentration of pore forming agent PEG20,000 in a casting solution is 50 wt%. In addition, the different chemical structure of amine monomers also caused the different membrane morphology and influencedmembrane forward osmosis performance. In this study, the desirable amine monomer is PIP. From the result of the forward osmosis experiment, the polyamide composite membrane was prepared by PSf substrate contacting with 0.35 wt% PIP aqueous solution,for 1 min and then contacting with 0.1 wt% TMC organic solution for 0.1 min showed the desirable performance for the forward osmosis with 1.0 M Na2SO4 solution as the draw solution, that is, water flux of 48.70±3.14 LMH and salt reverse flux of 14.54±2.47 gMH.
To improve the membrane FO performance, Anionic surfactant sodium dodecyl sulfate (SDS), cationic surfactant dodecyltrimethylammonium bromide（DTAB）, and Nonionic surfactant sorbitan monolaurate (Span 20) were incorporated in the PIP aqueous solution for forward osmosis. From the experimental results, the polyamide composite membrane prepared with 0.7 wt% DTAB in the PIP aqueous solution showed the best performance which was water flux of 63.23±2.24 LMH and the salt reverse flux of 17.83±2.18 gMH。
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