Electro-Membrane Filtration：Effects of Carbon nanotubes on Treating Natural Organic Matter
Date Issued
2008
Date
2008
Author(s)
Wu, Hsin-Chieh
Abstract
An electro-membrane cross-flow filtration was conducted with the inorganic ceramic tubular membrane in this study. Three various mixed solutions were prepared from 5mg/L DOC humic acid (HA) which was used to simulate nature organic matter in water, and 40 mg/L single-wall carbon nanotubes (SWCNT) or multi-wall carbon nanotubes (MWCNT). Both the effects of decrement in flux and removal of organic matters in water on different solutions under various pressures and electric field strength were investigated.he best performance of permeate flux and rejection of UV254 as well as DOC was resulted when applied electric field strength was near theoretical critical electric field value. With respect to the cost-effectiveness evaluation, it is advisable to apply the strength near critical electric field when an electro-membrane filtration process with carbon nanotube addition was implemented.he benefit of carbon nanotube addition to electro-membrane filtration process is more obvious under 98kPa pressure. The permeate flux of solutions with carbon nanotubes was better than pure humic acid (HA) solution under various electric field strength. When HA+SWCNT solution under 49kPa pressure, the DOC rejection only increased 3.61% with electric field strength rose from 43.42 V/cm to 72.36 V/cm. It was much less than 18.11% increase of DOC rejection when electric field strength rose from 19.30 V/cm to 43.42 V/cm which was close to the critical electric field strength.hen electric field was applied, HA+SWCNT solution has dramatic improvement on rejection of UV254 and DOC. For example, the average rejection of HA+SWCNT solution was 11% more than that of HA solution under 49kPa pressure but there’s little difference between HA+MWCNT solutions and HA solutions. It showed the selectivity of different type of carbon nanotubes to the rejection of target substances in the electro-membrane filtration process. he total resistance (Rtot) of filtration process could be greatly reduced due to electrokinetic phenomenon induced by electric field application. The effect of electrophoresis caused the decline of the resistance of fouling and concentration polarization layer (Rs), as well as the membrane intrinsic resistance (Rm) under the influence of electro-osmosis while electric field strength increased.verage rejection of humic acid after adding carbon nanotubes without membrane process, (UV254, DOC) removal were (5.72%, 5.55%) of SWCNT and (1.30%, 1.26%) of MWCNT, respectively. It was much different compared with more than 50% rejection under electro-membrane filtration process, and seemed to be more obvious of adding SWCNT. It could be suggested that SWCNT with more complete carbon structure has better ability of adsorption to humic acid. This phenomenon could attribute to the electric field application like electrophoresis and electro-osmosis, both play important role of the system to enhance permeate flux and rejection of pollutant.
Subjects
electro-membrane filtration
humic acid
carbon nanotube
electro-osmosis
electrophoresis
Type
thesis
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