What are the differences in the working principles between pure water machines and ultrapure water machines
Laboratory pure water machines generally use advanced reverse osmosis technology to produce pure water. The working principle of a pure water machine is to apply a certain pressure to water, allowing water molecules and ionized mineral elements to pass through the reverse osmosis membrane. However, the vast majority of inorganic salts (including heavy metals), organic matter, bacteria, viruses, etc. dissolved in water cannot pass through the reverse osmosis membrane, thus strictly separating the permeated pure water from the impermeable concentrated water. The pore size on the reverse osmosis membrane is only 0.0001 micrometers, while the diameter of viruses is generally 0.02-0.4 micrometers, and the diameter of ordinary bacteria is 0.4-1 micrometers. The water flowing out of the pure water machine meets the drinking water standard.
Ultra pure water machine is based on reverse osmosis technology, with the addition of ion exchange and terminal treatment technology. Some of them also have equipment for deep ion desalination, ultrafiltration, and UV photooxidation, and the resulting water quality is better than the water quality requirements of the national standard GB/T6682-2008 for laboratory grade water.
What is the purification process of ultrapure water machine? Common impurities in natural water include soluble inorganic matter, organic matter, particulate matter, microorganisms, soluble gases, etc. The ultra pure water machine aims to remove these impurities as much as possible. The commonly used methods for purifying water quality include distillation, reverse osmosis, ion exchange, filtration, adsorption, UV oxidation, etc. Ultra pure water machines can generally divide the water purification process into four steps: pretreatment (primary purification), reverse osmosis (producing pure water), ion exchange (producing 18.2M Ω. cm ultra pure water), and terminal treatment (producing ultra pure water that meets special requirements).
1) Preprocessing
Since the pre treated water will undergo further purification through reverse osmosis, it is essential to remove impurities that may affect the reverse osmosis membrane as much as possible; Mainly including large particulate matter, residual chlorine, and calcium and magnesium ions. It should be noted that different treatment units must be equipped according to the differences in inlet water quality. Most pure water machine manufacturers cannot effectively help customers solve this problem, which can lead to subsequent purification not achieving ideal results and shortening the lifespan of major components such as reverse osmosis membranes and ultra purification columns. To effectively solve this problem, precision filters, activated carbon adsorption filters, and softening resins are designed to remove large particulate matter, residual chlorine, calcium ions, and magnesium ions from water with targeted pre-treatment effects. The timely replacement of pre-treatment consumables (which are relatively cheaper) is crucial for the long-term stable operation of ultra pure machines and the protection of core components.
2) Reverse osmosis
Reverse osmosis is the use of a high-pressure pump to provide a pressure greater than the osmotic pressure difference to a high concentration solution. Water molecules are forced to pass through a semi permeable membrane to the low concentration side. Reverse osmosis can filter out 90% -99% of the vast majority of pollutants, including inorganic ions, due to its outstanding purification efficiency. Reverse osmosis is a very effective technology in water purification systems because it can remove most of the pollutants. Therefore, it is often used as a pre-treatment method, which can significantly extend the service life of the deionization exchange column. Considering that reverse osmosis is crucial in the water purification process and the replacement price of reverse osmosis membranes is high, it is recommended that users choose ultrapure water machines with protective functions for reverse osmosis membranes. In order to extend the service life of the reverse osmosis membrane as much as possible and improve the filtration efficiency of the reverse osmosis membrane, * technology was adopted, combined with a reverse osmosis flow limiting design and a flow limiting valve at the outlet, so that the reverse osmosis membrane is always immersed in water, without affecting its service life due to drying. Extending the lifespan of the reverse osmosis membrane ensures the quality of the effluent and also improves the cost-effectiveness of the ultrapure water system. The quality of reverse osmosis membranes has a significant impact on their lifespan and the service life of ultra purification columns, so it is recommended that users pay attention to the brand of reverse osmosis membranes, such as Dow.
3) Ion exchange
Ion exchange refers to the exchange of positive ions in water with H ions in ion exchange resin, and negative ions in water with OH - ions on ion exchange resin, in order to purify water. By removing ions through ion exchange, theoretically almost all ionic substances can be removed. At 25 ℃, the effluent resistivity reaches 18.2M Ω. cm. The quality of the effluent after ion exchange mainly depends on the quality of the ion exchange resin and the exchange efficiency between water and resin in the exchange column. The quality of ion exchange resin has a direct impact on the effluent quality and service life of ultrapure water machines.
4) Terminal processing
We mainly produce ultrapure water based on customers' special requirements, including ultra-low temperature, sterile, and heat free types. There are various treatment methods for different requirements, such as ultrafiltration for removing heat sources, dual wavelength ultraviolet oxidation for reducing total organic carbon (TOC) in water, and microfiltration for removing bacteria. Ultrafiltration (UF) membrane is a molecular sieve that, based on size, allows the solution to pass through extremely fine membranes to separate molecules of different sizes in the solution. It can reduce the heat source content in ultrapure water to below 0.001EU/ml. The dual wavelength ultraviolet oxidation method can utilize photo oxidation of organic compounds to reduce the total organic carbon concentration in ultrapure water to below 5ppb.