Influence of hydrophobicity of Natural organic matter on the fouling of Electrically enhanced membrane filtration
|Keywords:||天然有機物;親疏水性;外加電場薄膜程序;膜孔大小;Natural organic matter;NOM;Hydrophobicity;Electric enhanced membrane process;pore sizes||Issue Date:||2005||Abstract:||
In this study, NOM fractionation by DAX-8 resin has been used to obtain hydrophobic and hydrophilic NOM solution. The effect of hydrophobicity on electric enhanced membrane process under three pore sizes of membrane and different electric field strength were investigated. When electric field was not applied, hydrophilic NOM solution caused more flux decline than hydrophobic one. The flux decline was getting worse with increasing pore size, while the NOM rejection was getting better with decreasing pore size. Besides, hydrophilic NOM solution resulted in significant NOM rejection due to the greater fouling as compared to the hydrophobic sample. Through the calculation of series resistance for membrane, it was observed that the hydrophilic components largely contributed to irreversible resistance but the reversible/irreversible resistance caused by the hydrophobic components was quite similar. Membrane cleaning operations such as backwash, chemical cleaning were more economical for hydrophobic NOM solution. Accordingly, hydrophobic NOM solution is more applicable to water treatment than hydrophilic one.
When an electric field was applied, flux increased with the strength of the electric field. Direct current electric field could be used to reduce the fouling resistance by the electrophoresis effect. By analyzing the fouling resistances, the total fouling resistances of hydrophobic and hydrophilic NOM solutions were both reduced with the electric field. Under the electric field, NOM rejection was increased because electrophoresis decreased the NOM concentration on the membrane surface. Additionally, NOM rejection depended on the pore size of membrane, even if a high electric field was applied, so the pore sizes of membrane appeared to be another important factor affecting the rejection ratio. With regard to the flux increase, the fouling reduction, and the rejection ratio enhancement under the electric field, the proposed method is more suitable for hydrophobic NOM solution. Moreover, compared with the experiment of electrophoresis, the electrophoretic mobility of hydrophobic components is higher than that of hydrophilic ones, and a positive correlation between the electrophoretic mobility and the performance of electrically enhanced membrane filtration was recognized. Our experimental results showed that the electrically enhanced membrane filtration can handle hydrophobic components where electrophoretic velocity is faster. Under these conditions, the electric field enhanced filtration process improves the removal efficiency and the filtration flux obviously. Hydrophobic water could also increase the total volume of permeate than hydrophilic water. Consequently, the electric field enhanced filtration has great potential for rejection of NOM containing more hydrophobic components.
Key words: Natural organic matter; NOM; Hydrophobicity; Electric enhanced membrane process; pore sizes
|Appears in Collections:||環境工程學研究所|
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