Reverse Osmosis (RO) technology is a membrane separation and filtration technology that utilizes pressure difference as a driving force. Its pore size is as small as the nanometer level (1 nanometer=10-9 meters). Under a certain pressure, H2O molecules can pass through the RO membrane, while impurities such as inorganic salts, heavy metal ions, organic matter, colloids, bacteria, viruses, etc. in the source water cannot pass through the RO membrane, thus strictly distinguishing between permeable pure water and impermeable concentrated water. The working principle diagram of reverse osmosis is as follows:

Separate pure water from a solution containing solutes using a semi permeable membrane that can only pass through water. At this point, the water on the pure water side spontaneously penetrates the semi permeable membrane and enters the solution side, causing the water level on the solution side to rise. This phenomenon is called permeation. When the liquid level rises to a certain height, the pressure on both sides of the membrane reaches equilibrium, and the liquid level on the solution side no longer rises. At this point, there is a pressure difference on both sides of the membrane, called osmotic pressure. If a pressure greater than the osmotic pressure is applied to the solution side, the water molecules in the solution will be squeezed to the pure water side, which is exactly the opposite of osmosis. We call this reverse osmosis. We can see from the process of reverse osmosis that due to pressure, water molecules in the solution enter pure water, increasing the amount of pure water while the solution itself is concentrated.

The reverse osmosis device mainly consists of a high-pressure pump, a reverse osmosis membrane, and a control part. The high-pressure pump pressurizes the incoming water. Except for water molecules that can pass through the RO membrane, almost all other substances in the water (minerals, organic matter, microorganisms, etc.) are rejected from the membrane and cannot pass through the RO membrane, and are washed away by high-pressure concentrated water.

The reverse osmosis membrane filtration process utilizes the high desalination performance of RO membranes to completely remove TOC that was difficult to remove in the past pure water manufacturing process, SiO2、 Particles and bacteria. At the same time, it completely eliminates the consumption of acid and alkali in ion exchange regeneration, eliminates acid and alkali pollution, and avoids secondary pollution of bacteria and organic matter in the ion exchange layer. After reverse osmosis treatment, water can remove over 99% of dissolved solids, over 99% of organic matter and colloids, and almost 100% of bacteria.

The RO membrane has a removal rate of over 99% for high valence ions, colloids, bacteria, and organic substances with a molecular weight greater than 300 daltons (including heat sources), and a removal rate of over 95% for low valence ions (NA+, K)

Reverse osmosis is the most economical method to achieve a 90% -99% impurity removal rate, and it is also the best pretreatment method for reagent grade ultrapure water systems.

Note: The filtration capacity of RO membrane is greatly affected by water temperature, and the most suitable water temperature is 22 ℃ -28 ℃. For every 1 ℃ decrease in temperature, the water production of RO membrane decreases by about 3%. When the water temperature approaches 0 ℃, the RO membrane will stop producing water.