Ion Exchange for Dummies Lenntech（假人Lenntech离子交换）.pdfVIP

Rohm and Haas Ion Exchange ION EXCHANGE FOR DUMMIES An introduction Water Water is a liquid. Water is made of water molecules (formula H O). 2 All natural waters contain some foreign substances, usually in small amounts. The water in the river, in a well or from your tap at home is not just H O, it contains a little of: 2 • Solid, insoluble substances, such as sand or vegetal debris. You can in principle filter these solid substances out. • Soluble substances, that you most often cannot see and that cannot be filtered out. These substances can be inorganic or organic, they can be ionised (electrically charged) or not. The soluble, non-ionised substances are present in the water in form of molecules of various sizes and formulas, for instance: • Carbon dioxide is a small molecule with a simple formula: CO . 2 • Sugar is a larger molecule with a complicated formula abbreviated as C12H22O11. You may want to remove these foreign substances from the water. You can remove the ionised substances by ion exchange. Ions The soluble, ionised substances are present in water as ions, which are electrically charged atoms or molecules. The positively charged ions are called cations, and the negatively charged ions are called anions. Because water is globally neutral electrically (otherwise you would get an electric shock when you put your hand in water) the number of positive charges is identical to the number of negative charges