The effect of functional groups of humic acid on PAC-UF process
| Autor: | Shih-hsiang liu, 劉世翔 |
|---|---|
| Rok vydání: | 1999 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 87 Use of ultrafiltration (UF) for dissolved organic matter removal in water industry has become emerges in recent years. The role of dissolved organic matter (DOM) on membrane performance in terms of permeate flux decline as well as permeate water quality are the two primary concerned issues in UF process. It has been studied extensively that UF flux decline is primary attributed to the association of DOM and membrane material. The adsorption of DOM on membrane surface, gel layer formation on surface, and membrane pore clogging are the major reasons accounting for permeate flux decline. In our previous work, the effects of important characteristics of humic acids as molecular size and hydrophobicity on UF operation were investigated exclusively. The objective of this current work is placed on understanding the role of humic acid*s functional groups on UF and PAC-UF performance. To isolate humic acid fractions bearing carboxylic functional groups from phenolic functional groups, a secondary amine anionic exchanger resin and DEAE anionic resin were employed for this purpose. The secondary amine anionic exchanger resin is able to bind the humic acid fractions with phenolic groups. The DEAE anionic resin can react with the carboxylic group of a humic acid. The isolated humic acid fractions were examined for identifying various functional groups with the use of FTIR and a set of acid-base titration. With these two different resins, carboxyl-containing fractions can be separated from the phenol-containing fractions. The isolated humic acid fractions were subject to the UF performance evaluation in terms of flux and water quality. Two different membrane materials, hydrophobic polysulfone (PS) and hydrophilic regenerated cellulose acetate (CA) were selected for UF experiments in this study. Under various TOC concentrations, pH, and the electric conductivity (EC) conditions, solutions with carboxylic group dominated humic acids caused the worst flux decline. The situation was adversely affected by the presence of high EC. On the other hand, solutions with phenolic group dominated humic acid exhibited less membrane fouling and were not profoundly affected by the presence of high EC. Similar results were obtained in both UF and PAC-UF modes for these two solutions. The advantage of using PAC for pre-adsorption of humic acid fractions is only the reduction of TOC concentration as well as THMFP in permeate. Membrane fouling and flux decline was not improved significantly with the help of PAC in PAC-UF operation. However, the permeate flux of solutions with less carboxyl groups doesn''t tend to cause additional flux decline. The hydrophilic CA membrane seems to generate higher permeates flux than the hydrophobic PS membrane. The flux decline for combined PAC-UF streams is worse with PS membrane than the CA membrane. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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