1999 Fiscal Year Final Research Report Summary
MASS TRANSFER MECHNISM AND SEPARATION CHARACTERISTICS OF NANOFILTRATION MEMBRANES UNDER VERY LOW PRESSURE OPERATION AND WITH MIXTURE OF DISSOLVED SUBSTANCES INTERACTION
| Project/Area Number |
09450196
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Civil and environmental engineering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
YAMAMOTO Kazuo Environmental Science Center, The University of Tokyo, Professor, 環境安全研究センター, 教授 (60143393)
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| Co-Investigator(Kenkyū-buntansha) |
TAKIZAWA Satoshi Dept. of Urban Eng., The University of Tokyo, Assoc. Professor, 工学系研究科, 助教授 (10206914)
URASE Taro Dept. of Civil Eng., Tokyo Institute of Technology, Assoc. Professor, 工学系研究科, 助教授 (60272366)
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| Project Period (FY) |
1997 – 1999
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| Keywords | nanofiltration / low-pressure operation / multi le dissolved substances / separation characteristics / river water / groundwater / arsenic / THMFP |
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| Research Abstract |
This study aims to elucidate mass transfer and separation characteristics through NF membranes especially at operations under very low pressure and with mixture of dissolved substances interaction.
As the last year of the research periods, a pilot experiment has been carried out at Tamagawa Water Purification Plant, Tokyo. Nanofiltration characteristics of river water was investigated in details. A NF membrane with a high salt retention gave both a high retention of THM precursors and a high retention of dissolved ions for more than a half year operation. The combined effects of size-exclusion, electric charge, and affinity could explain the mechanism of membrane separation. In addition, it is shown that a modified Extended Nernst Plank Equation could well explain the separation of most of dissolved ions by a positively charged membrane. However, a discrepancy between theoretical and experimental was observed for sulfate ions, a further improvement of the model is required for the ion mixture of river water.
A manually driven nanofiltration system has been applied to arsenic removal from groundwater in Bangladesh. The field tests in the rural area has proven the system is technically feasible even at a very low pressure of 3 atm. However, the groundwater heavily contaminated with arsenic typically contains trivalent arsenic compounds and NF gives a lower retention of trivalent arsebnic than that of pentavalent one, suggesting a need of pre-oxidation process prior to NF. These couter measures are easily rationalized by mechanism-oriented understandings as a result of this study.
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