High purity water, free of micro-organisms, can be used various purposes in medical treatments, semiconductor industry for the manufacture of chips and electronic devices etc. Filtration by fibrous filters is one of the principle methods used to remove fine particles in the liquid. The most widely u...
High purity water, free of micro-organisms, can be used various purposes in medical treatments, semiconductor industry for the manufacture of chips and electronic devices etc. Filtration by fibrous filters is one of the principle methods used to remove fine particles in the liquid. The most widely used mechanism of filtration is the mechanical sieving process, but this process usually has the characteristics of the high pressure drop and low filtration efficiency. Whereas in the case of electrokinetic capturing mechanism, contaminants are retained on the surface by attractive short range Van Der Waal's forces. The advantage of electrokinetic capture over mechanical straining is that the filter medium can separate very tiny particles which are practically impossible to be separated by simple mechanical straining. Also, in electrokinetic capture, the pores need not be smaller than the particulates to retain them since the most of particle in liquid usally have negative charges. The ability of the filter medium to hold back particles of very small size by electrokinetic capture depends greatly on the surface charge of both the filter surface and the particles to be separated. These surface charges are termed as the zeta potential. It is the most important cause for the affinity between virus and filter surfaces. The main of the present work is to modify positively the surface of nanofiber filter for capturing negatively charged contaminants mainly bacteria and virus from water. In this study, The filter media are made of glass fiber(0.45 ㎛), cellulose(10 ㎛) and poly-ethylenimine(PEI) at 50 cmHg vacuum pressure and 6 kgf/㎠ roller pressure. The base materials, glass fiber and cellulose are taken in desired proportion and mixed together to form a slurry. The type of processing used to wet processing. The PEI is dissolved in water to make a solution of desired concentration. This PEI solution are next mixed with the base materials slurry. The slurry is formed into long sheets by the vacuum process, roller pressure and drying process. After the nanofiber filters are investigated the pore size, zeta potential, filtration efficiency and pressure drop as the PEI ratio of content and base fiber(glass fiber, cellulose) ratio of content. In this experiment of result, The average pore size of nanofiber filters are measured by image processing method(IMT, Bethtech). It is 0.5 ㎛. Also, The surface of filter is formed the coverage by PEI The surface of filters are measured the zeta potential by ESL-8000(Otsuka). This result of zeta potential is increased by content ratio of PEI. Especially, The nanofiber filter with a high positive zeta potential of + 37.92 mV is obtained with PEI content ratio of 100 % at the glass fiber and cellulose content ratio of 50: 50. Also, the nanofilter is increased the filtration efficiency as increasing zeta potential. Especially, the zeta potential value and filtration efficiency of the modified nanofiber filter were + 37.92 mV at pH 7 and 78 % for PSL particles of 0.085 ㎛ at the glass fiber and cellulose content ratio of 50: 50. In analysis of result, PEI has a positive zeta potential which makes it suitable for the electro-positively charged nanofiber filter. Also, the pore size of 0.5 ㎛ can be manufactured which can trap most bacteria and virus from water. The developed filter can apply to the ultra-pure watering system.
High purity water, free of micro-organisms, can be used various purposes in medical treatments, semiconductor industry for the manufacture of chips and electronic devices etc. Filtration by fibrous filters is one of the principle methods used to remove fine particles in the liquid. The most widely used mechanism of filtration is the mechanical sieving process, but this process usually has the characteristics of the high pressure drop and low filtration efficiency. Whereas in the case of electrokinetic capturing mechanism, contaminants are retained on the surface by attractive short range Van Der Waal's forces. The advantage of electrokinetic capture over mechanical straining is that the filter medium can separate very tiny particles which are practically impossible to be separated by simple mechanical straining. Also, in electrokinetic capture, the pores need not be smaller than the particulates to retain them since the most of particle in liquid usally have negative charges. The ability of the filter medium to hold back particles of very small size by electrokinetic capture depends greatly on the surface charge of both the filter surface and the particles to be separated. These surface charges are termed as the zeta potential. It is the most important cause for the affinity between virus and filter surfaces. The main of the present work is to modify positively the surface of nanofiber filter for capturing negatively charged contaminants mainly bacteria and virus from water. In this study, The filter media are made of glass fiber(0.45 ㎛), cellulose(10 ㎛) and poly-ethylenimine(PEI) at 50 cmHg vacuum pressure and 6 kgf/㎠ roller pressure. The base materials, glass fiber and cellulose are taken in desired proportion and mixed together to form a slurry. The type of processing used to wet processing. The PEI is dissolved in water to make a solution of desired concentration. This PEI solution are next mixed with the base materials slurry. The slurry is formed into long sheets by the vacuum process, roller pressure and drying process. After the nanofiber filters are investigated the pore size, zeta potential, filtration efficiency and pressure drop as the PEI ratio of content and base fiber(glass fiber, cellulose) ratio of content. In this experiment of result, The average pore size of nanofiber filters are measured by image processing method(IMT, Bethtech). It is 0.5 ㎛. Also, The surface of filter is formed the coverage by PEI The surface of filters are measured the zeta potential by ESL-8000(Otsuka). This result of zeta potential is increased by content ratio of PEI. Especially, The nanofiber filter with a high positive zeta potential of + 37.92 mV is obtained with PEI content ratio of 100 % at the glass fiber and cellulose content ratio of 50: 50. Also, the nanofilter is increased the filtration efficiency as increasing zeta potential. Especially, the zeta potential value and filtration efficiency of the modified nanofiber filter were + 37.92 mV at pH 7 and 78 % for PSL particles of 0.085 ㎛ at the glass fiber and cellulose content ratio of 50: 50. In analysis of result, PEI has a positive zeta potential which makes it suitable for the electro-positively charged nanofiber filter. Also, the pore size of 0.5 ㎛ can be manufactured which can trap most bacteria and virus from water. The developed filter can apply to the ultra-pure watering system.
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