| Summary: | 碩士 === 中原大學 === 化學工程研究所 === 94 === Abstract
Many fossil fuel power plants employ flue gas desulfurization (FGD) using scrubbing systems to remove contaminants from boiler exhaust gases. The waste composition in the effluent from the scrubbing system varies widely, designing an FGD wastewater treatment system that meets regulations can be challenging. Thus, aspirations for new wastewater treatment/recovery processes with environmental friendly technologies, lower energy consumption, and improved economics have emerged. In this study, the simulated FGD effluent from activated carbon column was treated by nanofiltration (NF) process to assess the potential of NF to replace softening column in FGD wastewater treatment process. Experimental results depict that NF membranes notably reject divalent ions. While monovalent ions and divalent ions passing through, the latter had a significant effect on the rejection of NF process. Increase of the concentration of anion in feed solution will results in an ionic exclusion effect and thus retarding cation diffusion, and vice versa to the case of cations. The existence of organic matter may affect the pH value of the feed solution, which will result in protonation of the carboxylic group in the membrane. This change of membrane property will reduce the amount of negative charge of the membrane and caused a reduction of steric exclusion to the ions as well as a increase of flow rate. Finally, the transport parameters of salt in this low-pressure NF process were also evaluated. Theoretical analysis reveals that effective charge density, pore radii and the ionic strength determine the rejection of monovalent ions.
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