Vol.4 No.3 2012

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Research paper : A novel technology for production of drinking water in emergencies (A. Sonoda)−157−Synthesiology - English edition Vol.4 No.3 (2012) In the past five years, there were 530 cities, towns, and villages with wells that exceeded the environmental standard, and that dominates 31 % of all cities, towns, and villages. The cause of “nitrate-nitrogen and nitrite-nitrogen” pollution is mainly due to the nitrogen from fertilizer application, farm animal excrements, and sewage. In many cases there are multiple causes of pollution, and the range of pollution covers a large area.When the water containing “nitrate-nitrogen and nitrite-nitrogen” over a certain concentration is consumed, it is known to cause methemoglobinemia, a disease where the oxygen deficiency occurs due to the loss of oxygen carrying capacity of the blood, mainly in infants. The environmental standard value for contamination of underground water for “nitrate-nitrogen and nitrite-nitrogen” is 10 mg/L or less, which is the sum of the concentrations of the “nitrate ion” and “nitrite ion” converted into “nitrogen”.In a case where the pollution that exceeds the environmental standard is found in the groundwater, according to the Water Quality Pollution Control Act, the prefectures and ordinance-designated cities must take the following measures: 1) take measures such as installing drinking regulations, such as designating as undrinkable, from the perspective of protecting health, 2) conduct surveys to determine the range of pollution and to identify the source of pollution, and 3) promote measures such as purification considering the usage of the groundwater.Attempts to remove the nitrate ion using the anion exchanger have been done, but the effect was limited in the presence of coexisting anions. Therefore we developed a novel adsorbent reagentNote 3) that was selective for nitrate ion (Figs. 3, 4, and 5).The adsorbent reagent selective to nitrate ion is a layered double hydroxide (LDH) of aluminum and magnesium. It is an inorganic ion exchanger (Mg0.80Al0.20(OH)2Cl0.20) with anions with different Mg/Al ratios and ion exchangeability from the mineral called the hydrotalcite (Mg0.75Al0.25(OH)2(CO3)0.125). The studies to increase the ion exchanging volume were done by increasing the aluminum content in the LDH, but it was found that the selectivity against nitrate ion appeared by decreasing the aluminum content. Also, since it was a chloride ion type, the nitrate ion could be adsorbed in water such as seawater that contains vast amounts of chloride ions.The awareness of disaster prevention increased since the Great Hanshin Awaji Earthquake, and many local governments prepared the water purification system for emergency. However, the reverse osmosis (RO) system that can produce pure water from seawater requires power and cannot be operated readily by an untrained person, and therefore, a simple water purification system was in demand. In this R&D, we aimed at a product different from the RO system, and at a market of “simple device that can be operated manually without exterior power source”, and created a prototype. The water qualities were measured for raw water from rivers, wells, and pools. The river water did not contain harmful ion, and sufficient drinkability could be obtained with the combination of simple filtering and sterilization. Some well water exceeded the tap water standard value for nitrate ion in some regions, and selective adsorbent material for nitrate ion would be effective. For pool water, the bromate ion, an impurity of the chloride disinfectant, was detected in some cases, and it was necessary to use a removing reagent for bromate ion. 2 Objective of the R&DIn the Consortium R&D Project for Regional Revitalization of FY 2006, a joint research unit was organized centered around AIST and Teijin Engineering Ltd., with universities, public research institutions, and local small/medium companies such as Kyowa Chemical Industry Co., Ltd. The unit worked on the topic “Development of mobile water purification system by the contactless compositing of nano-particles with separating functions”.AIST developed a nitrate ion removal system using a selective adsorbent reagent to make groundwater, which Fig. 3 SEM photograph of powder adsorbent reagentSize of plate-like particle: width about 500 nm and thickness about 20 nmFig. 4 SEM and TEM photographs of the fibrous adsorbent materialDiameter of the fiber is about 1 mm. The interior structure consists of powder adsorbent reagent sealed inside the porous polymer without contact.1 mmφPowder adsorbent reagentContactless interface

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