The history of ultrapure water manufacturing:
* Stage: Pretreatment filter -> Yang bed -> Yin bed -> Mixed bed
Second stage: pretreatment filter -> reverse osmosis -> mixed bed
Current stage: pretreatment filter -> reverse osmosis -> EDI (no acid or alkali required)
In recent decades, mixed bed ion exchange technology (D) has been the standard process for the preparation of ultrapure water. Since it requires periodic regeneration and consumes a large amount of chemicals (acid and alkali) and industrial pure water during the regeneration process, and causes certain environmental problems, it is necessary to develop an acid-free ultrapure water system.
Because traditional ion exchange has become increasingly incapable of meeting the needs of modern industry and environmental protection, EDI technology combining membrane, resin and electrochemical principles has become a revolution in water treatment technology. The regeneration of its ion exchange resin uses electrical energy, which eliminates the need for acid and alkali, and is therefore more environmentally friendly in today's world.
Since the industrialization of EDI membrane technology in 1986, thousands of EDI systems have been installed worldwide, especially in the pharmaceutical, semiconductor, power and surface cleaning industries, as well as in the fields of wastewater treatment, beverages and microbes. It is also widely used.
The equipment is applied after the reverse osmosis system to replace the traditional mixed bed ion exchange technology (MB-DI) to produce stable ultrapure water. Compared with hybrid ion exchange technology, EDI technology has the following advantages:
1 water quality is stable
2 easy to achieve fully automatic control
3 will not stop due to regeneration
4 no need for chemical regeneration
5 low operating costs
6 factory area is small
7 no sewage discharge
How EDI works:
The EDI module clamps the ion exchange resin between the anion/cation exchange membrane to form an EDI unit. The working principle of EDI is shown in the figure. In the EDI module, a certain number of EDI units are separated by a grid to form a concentrated water chamber and a fresh water chamber. A female/positive electrode is also provided at both ends of the unit group. Under the push of direct current, the anions and cations in the water flow through the fresh water chamber pass through the anion-cation exchange membrane and enter the concentrated water chamber to be removed in the fresh water chamber. The ions are taken out of the system through the water in the concentrated water chamber to become concentrated water. The EDI equipment generally uses secondary reverse osmosis (RO) pure water as the EDI feed water. The RO pure water resistivity is generally 40-2 μS/cm (25 ° C). EDI pure water resistivity can be as high as 18 MΩ.cm (25 ° C), but according to deionized water use and system configuration settings, EDI ultrapure water is suitable for the preparation of resistivity requirements of 1-18.2M Ω.cm (25 ° C) pure water.
EDI technology is widely accepted by the pharmaceutical industry, the microelectronics industry, the power generation industry, and laboratories. Applications in surface cleaning, surface coating, electrolysis, and chemical industries are also growing.
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