Comparison of reverse osmosis and electrodialysis technology

Since its establishment in the 1950s, electrodialysis technology has risen rapidly in the application of engineering technology. It has played an increasing role in industries such as seawater desalination, brackish water desalination, seawater concentration salt production, wastewater treatment, and food, medicine, electronics, and power industries . With many excellent application examples, it has confirmed its technological advancement and several excellent characteristics that other separation methods cannot replace. Several magical functions that are being developed and will be developed are even more colorful. China is the research and development work of electrodialysis project since 1958, and it belongs to one of the countries that started earlier in the world.

It has at least the following four purposes:

  1.  Separate some ions from the electrolyte solution to reduce the concentration of the electrolyte solution. Such as desalination of sea water, desalination of brackish water, preparation of industrial pure water or drinking pure water, radioactive wastewater treatment, etc.
  2.  Transfer part of the electrolyte and ions in the solution to another solution and increase its concentration. Such as seawater concentration system, the purification of chemical products, the recovery of useful components in industrial residual liquid, etc.
  3.  Remove electrolyte ions from organic solutions. It is currently mainly used in the food and pharmaceutical industries. It has been very successful in whey desalination, sugar desalination and amino acid refining.
  4.  In the electrolyte solution, the separation of ions with the same charge but different charges and the separation of ions with the same charge, ion exchange membranes that only allow the penetration of monovalent ions to concentrate seawater for salt production are examples of the former industrial application.

Reverse osmosis technology is a new technology applied in the world in the late 1960s. Reverse osmosis (RO), also known as reverse osmosis, is mainly composed of a high-pressure pump and a reverse osmosis membrane. In the case of high enough pressure, except for water molecules, other minerals in the water, organic and various ions are almost rejected outside the membrane, and washed out by high pressure water flow. The water that penetrates the other side is safe, hygienic and pure water. The principle is equivalent to a semi-permeable membrane in the human body, so that useful substances can be used through the membrane, and unnecessary substances are discharged. Because it is in the opposite direction of natural penetration. It is called reverse osmosis. It has become an important technical equipment in modern pure water, high-purity water preparation, seawater desalination, brackish water desalination and other industrial separation projects.

It has the following five characteristics:

  1. Low energy consumption and significant economic benefits. Practice has proved that desalination of 2000-5000mg / L of brackish water to 5000mg / L of drinking water is the most economical.
  2. Flexible system application, convenient operation and maintenance According to different conditions and requirements, different forms of system design can be flexibly used. Parallel connection can increase water production, series connection can increase the desalination rate, and circulation or partial circulation can shorten the process flow. During operation, several main parameters of voltage, current, concentration, flow, pressure and temperature are controlled to ensure stable operation.
  3. No pollution to the environment
  4. Long service life. The membrane can be used for 3-5 years, the electrode can be used for 7-8 years, and the separator can be used for about 15 years.
  5. High raw water rate. The recovery rate of seawater and high concentration brackish water can reach more than 60%. The general brackish water recovery rate can reach 65% -80%.

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