[Hongjie Water Service] Reverse Osmosis Membrane Treatment and Application

There are currently four methods for producing pure water, namely distillation, electrodialysis, ion exchange, and reverse osmosis. And reverse osmosis is the most advanced, efficient, and energy-saving technology for producing pure water. Reverse osmosis is a water treatment process that rapidly developed in the 1960s. At present, it has been used in urban water, boiler feed water, power plant boiler feed water, industrial wastewater and seawater desalination, and solute separation in various solutions.

At present, thermal power generation is still the main force in China's power generation, and the technology of reverse osmosis for water treatment is widely used in thermal power production. Huaneng Yuhuan Power Plant's reverse osmosis seawater desalination, Datang Gangu Power Plant's reverse osmosis water treatment, Guodian Handan Thermal Power Plant's reverse osmosis water treatment, Shanxi Yangquan Youguang Power Generation Co., Ltd., and so on.

1. Reverse osmosis principle;

If fresh water and saline water are separated by a semi permeable membrane that can only penetrate water but cannot penetrate solutes, the water in fresh water will pass through the semi permeable membrane to the saline side, and this phenomenon is called permeation. Therefore, during the infiltration process, the increase in liquid level on one side of the brine will generate pressure, thereby inhibiting further infiltration of fresh water into the brine side. Finally, when the liquid level on the concentrated water side is at a certain height from the fresh water surface, so that the pressure it generates is sufficient to offset its tendency to penetrate, the liquid level on the concentrated water side will no longer rise. At this point, the amount of water entering the concentrated solution through the semi permeable membrane is equal to the amount of water leaving the concentrated solution through the semi permeable membrane, so they are in equilibrium. At equilibrium, the liquid level difference h between saline and fresh water represents the osmotic pressure difference between these two solutions. If fresh water is replaced with pure water, this pressure difference represents the osmotic pressure of saline water. Based on this principle, it is not difficult to infer that if a pressure higher than the osmotic pressure is applied to the concentrated water side, pure water in the brine can be squeezed out, which becomes water in the brine and permeates into the pure water. In this way, its infiltration direction is opposite to natural infiltration, which is the reverse osmosis principle.

2. Semipermeable membrane;

The phenomenon of infiltration was discovered in the 18th century. Most people use animals for experiments. Animal membranes are not truly semi permeable membranes, they have many drawbacks and cannot be applied in industry. So, the development of reverse osmosis technology depends on the production process of semi permeable membranes. A good semi permeable membrane should have the following characteristics: 1. high permeability and high desalination; 2. High mechanical strength; 3. Resistant to acid, alkali, and microbial invasion; 4. Long service life; 5. Easy to make and lower in price.

2.1 Cellulose acetate membrane

This is the earliest practical artificial film made in 1960. Now, its manufacturing method has been improved multiple times, and the product has the advantages of high water permeability, high desalination rate, and low price.

2.2 Polyamide film

Before 1970, the main films made were aliphatic polyamide films, such as nylon 66, nylon 6, etc., which had poor water permeability. Later, aromatic polyamide films were made, which had good water permeability, desalination rate (see Table 1), mechanical strength, and chemical stability. It can be used within a pH range of 4 to 10 (long-term use range is pH=5-9). Aromatic polyamide membranes are mainly made into hollow fibers.

2.3 Composite membrane

The reason why the above semi permeable membranes can perform permeability is due to the activated layer on their surface. This activation layer only needs to be very thin - it is too thick to facilitate infiltration, but instead will cause a decrease in water permeability and accelerate the rate of flow decay with running time. However, when preparing these membranes, it was difficult to make the activation layer thinner than 0.001m, so a composite membrane was developed.

A composite membrane is a composite of two thin layers (see Figure 2), which is first made into a porous support layer on the fabric, and then undergoes polymerization reaction of an activation layer on its surface. The support layer material can be polysulfone, and the activation layer can be polyurea.

The composite membrane has superior performance in terms of permeability, desalination rate, and flow attenuation. Its appearance greatly reduces the operating pressure of reverse osmosis, prolongs the lifespan of the membrane, and improves the economic benefits of reverse osmosis.

As a pioneer in the industry, Hongjie Water always adheres to the business philosophy of integrity, professionalism, and innovation, constantly developing new technologies, exploring new fields, and providing optimized solutions for users. The business field has involved industries such as chemical, food and beverage, bucket/bottled water, semiconductor, electronic appliances, medical and health care, biopharmaceuticals, aquaculture and planting, and can provide feasibility study planning and design, manufacturing and installation, engineering construction, engineering management, and after-sales service solutions for a large number of households.

More information can be found on the official website of Shenzhen Hongjie Water Technology Co., Ltd. www.czhengwei.net. If you need it, you can call the company's hotline for free at 180 3800 0078. We will be happy to serve you.