What is the principle of reverse osmosis in water treatment?

The principle of reverse osmosis in water treatment primarily revolves around the use of a semipermeable membrane. This membrane allows water to pass through while blocking a vast majority of dissolved ions, molecules, and larger particles. This method is effective in removing contaminants such as salts and impurities from water, making it suitable for producing clean drinking water or for various industrial applications.

In reverse osmosis, pressure is applied to overcome the natural osmotic pressure, causing the water to move through the semipermeable membrane from a region of higher concentration of solutes (contaminated water) to a region of lower concentration (clean water). This process efficiently separates unwanted substances from the water, thereby ensuring the resulting water is much purer and safer for consumption or use.

Other methods mentioned in the options rely on different principles. For instance, using heat to purify water focuses on boiling, which is effective for killing pathogens but does not remove dissolved solids or contaminants. Gravity-based filtration generally involves physical barriers to remove particulates but does not address dissolved substances effectively. Thus, the unique capability of reverse osmosis to selectively separate ions and larger impurities using a semipermeable membrane is what distinguishes it as an essential method of water treatment.