RO membrane, reverse osmosis membrane

There are two main commercial membrane products on membrane equipment such as ultrafiltration, nanofiltration, and reverse osmosis: cellulose acetate membrane（CA）And polyamide（PA）Composite film series（TFC)

Comparison of properties of commercial reverse osmosis membranes:

*Exposure to 1ppm free chlorine for up to1000hour

Note:

1.CAThe membrane has chlorine resistance and is therefore commonly used in municipal drinking water or beverage industries

2. CleaningCADuring membrane cleaning, cleaning solutionPHThe value must not exceed7.5BecausePHExcessive values may cause damage to the membrane

Desalination rate: The removal rate of ions by the membrane depends on the size and charge of the ion. The desalination rate of common salt systems is shown in the table below.

Working Principle:

A thin film that selectively penetrates substances is called a semi permeable membrane, and a thin film that can only pass through solvents but not solutes is generally called an ideal semi permeable membrane. When dilute solutions (such as fresh water) and concentrated solutions (such as saltwater) of the same volume are placed on both sides of a semi permeable membrane, the solvent in the dilute solution will naturally pass through the semi permeable membrane and flow spontaneously towards the concentrated solution side. This phenomenon is called permeation. When the permeation reaches equilibrium, the liquid level on the concentrated solution side will be higher than that of the dilute solution by a certain height, forming a pressure difference, which is the osmotic pressure. The magnitude of osmotic pressure depends on the inherent properties of the solution, which are related to the type, concentration, and temperature of the concentrated solution and independent of the properties of the semi permeable membrane. If a pressure greater than the osmotic pressure is applied to the concentrated solution side, the direction of solvent flow will be opposite to the original osmotic direction, starting to flow from the concentrated solution to the dilute solution side. This process is called reverse osmosis. Reverse osmosis is a reverse migration movement of osmosis, which is a separation method driven by pressure and using the selective retention effect of a semi permeable membrane to separate solutes and solvents in a solution. It has been widely used in the purification and concentration of various liquids, with the most common application example being the use of reverse osmosis technology in water treatment processes to remove impurities such as inorganic ions, bacteria, viruses, organic matter, and colloids from raw water, in order to obtain high-quality purified water.

Recommended inlet water quality:

Reverse osmosis membranes are widely used in fields such as power, petrochemicals, steel, electronics, pharmaceuticals, food and beverage, municipal and environmental protection. They play an important role in desalination of seawater and brackish water, preparation of boiler feedwater, industrial pure water and electronic grade ultrapure water, production of purified drinking water, wastewater treatment and special separation processes.

Advantages of PA film:

1. Low overall operating costs

2. Low operating pressure

3. High desalination rate

4. Significant reduction in energy consumption

Advantages of CA membrane:

1. Tolerance to chlorine and oxidants-CA膜最高可以耐受1ppmFree chlorine. Chlorine and oxidants can causePAMembrane damage.

2. Suitable for applications with high risk of biological pollution-The ability to tolerate oxidants enablesCAMembrane can be used to solve the problem of microbial contamination. Even if disinfectants such as chlorine are continuously added as oxidants, the membrane will not be damaged.

3. Not prone to pollution and blockage-YuPAMembrane and polysulfone（PS）Compared to membranes,CAThe anti fouling ability of the membrane is stronger.

Disadvantages of CA membrane:

1. Hydrolysis-CAThe acetic acid groups located on the polymer in the membrane will hydrolyze. Due to hydrolysis andPHValue related, in order to ensureCAThe membrane is working normally, it is functioning properlyPHThe value should be maintained at4.0-6.0Once hydrolysis occurs, the membrane will lose its desalination ability.

2. Short service life-Due to hydrolysis issues,CAThe service life of the membrane generally does not exceed three years, andPAThe service life of the membrane can usually reach3-7year

3. High operating pressure-CAThe membrane requires an operating pressure of400psiLeft and right, to ensure normal flux and desalination rate

4. Large investment in fixed equipment-compared toPAMembrane equipment,CAThe operating pressure of the membrane is relatively high, which requires the use of high-power pumps and expensive membrane casingsCAThe fixed assets investment of membrane equipment is relatively large.