Reverse osmosis membrane - Gyakushin to Umaku (English spelling)

Japanese: 逆浸透膜 - ぎゃくしんとうまく（英語表記）reverse osmosis membrane

If a container is divided by a semipermeable membrane such as cellophane that allows water to pass through but not salt, and seawater is placed in one side and fresh water in the other, the fresh water will pass through to the seawater side and the seawater level will rise. The pressure on the seawater side of the membrane is higher than that on the fresh water side, and is called osmotic pressure. When pressure is applied to the seawater side, the seawater moves to the fresh water side, but if pressure greater than the osmotic pressure is applied, the amount of fresh water increases. This method of extracting fresh water from seawater is called reverse osmosis (correctly called hyperfiltration). Compared to evaporation methods, it consumes very little energy because it obtains fresh water in liquid form. It is used in arid regions such as Saudi Arabia and on ships. Reverse osmosis membranes are also used to produce ultrapure water, which is necessary for the electronics and pharmaceutical industries. There is also a theory that one of the reasons why Japanese semiconductors are superior is that they have developed superior reverse osmosis membranes. A pressure of about 6 MPa (megapascals) is applied for operation, but recently low-pressure reverse osmosis membranes that can be used at pressures of about 1 MPa have been developed.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

セロファンのような水は透 (とお) すが塩 (えん) を透さない半透膜で容器を仕切り，一方に海水を他方に真水を入れると，真水は海水側に透過して海水の水位が上昇する。海水側で膜にかかる圧力は真水側より高く，浸透圧と呼ばれる。海水側に圧力をかけると海水中の水が真水側に移動するが，浸透圧以上の圧力を加えると真水の量が増大する。このようにして海水中から真水を取り出す方法を逆浸透法 (正しくは超ろ過法 hyperfiltration) という。蒸発法に比べて液体のままで真水が得られるのでエネルギー消費量が非常に少ない。サウジアラビアのような乾燥した地域や船舶で使用されている。このほか電子工業，製薬工業に必要な超純水の製造にも逆浸透膜が使われている。日本製の半導体が優れている原因の一つに，優れた逆浸透膜を開発した結果だという説もある。操作には 6MPa (メガパスカル) 程度の圧力を加えているが，最近 1MPa程度の圧力で使用できる低圧逆浸透膜も開発されている。

出典　ブリタニカ国際大百科事典小項目事典ブリタニカ国際大百科事典小項目事典について　情報

<<: Arc sine function

>>: Reverse Osmosis