Summary of Pure Water Preparation Process

The demand for ultrapure water has increased with the development of the semiconductor industry, leading to higher requirements for ultrapure water quality. This has greatly promoted the development of pure water technology, resulting in the widespread application of ultrapure water systems. Advanced water treatment technologies such as microfiltration, ultrafiltration, electrodialysis, and reverse osmosis have developed rapidly. Membrane-based pure water production has replaced traditional ion exchanger systems, solving the TOC (Total Organic Carbon) problem and meeting the pure water quality requirements of the electronics industry.

I. Fine Filtration Pure Water Treatment

Uses filter membranes made of special materials, offering high filtration precision. Common methods include microfiltration membranes and cartridge filters.

II. Coarse Filtration Pure Water Treatment

This refers to mechanical filtration, removing suspended solids, colloids, turbidity, color, odor, etc., from water. Main filtration methods include clarifiers, rapid filters, sand filters, sand filters, multi-media filters, activated carbon filters, disc filters, and high-efficiency fiber filters.

III. Ultrapure Water Treatment

This is a type of membrane filtration, removing large molecules, colloids, bacteria, etc. It offers high filtration precision, with ultrafiltration membranes being the most common. Ultrafiltration membranes cannot remove ions from water; that is, they do not have desalination capabilities. They are used for pretreatment of reverse osmosis or for fine treatment after reverse osmosis, and can also be used alone. Ultrafiltration is a tangential flow and pressure-driven filtration process that separates particles according to their molecular weight. The pore size of ultrafiltration membranes is approximately in the range of 0.002-0.1 micrometers. Dissolved substances and substances smaller than the membrane pore size can pass through the membrane as permeate, while substances that cannot pass through the membrane are concentrated in the effluent. Therefore, the product water contains water, dissolved solids, and low molecular weight substances, while colloids, suspended particles, high molecular weight organic matter, bacteria, viruses, and protozoa are filtered out.

IV. Reverse Osmosis Pure Water Treatment

Reverse osmosis, abbreviated as RO, is a membrane separation technology developed in the 1960s. Its principle is that raw water passes through a reverse osmosis membrane under high pressure, and the solvent in the water diffuses from a high concentration to a low concentration, thereby achieving separation, purification, and concentration. Because it is the opposite of natural osmosis, it is called reverse osmosis. Reverse osmosis can remove bacteria, viruses, colloids, organic matter, and over 98% of dissolved salts from water. This method features low operating costs, simple operation, high automation, and stable effluent quality. Compared to other traditional water treatment methods, it has significant advantages and is widely used in ultrapure water treatment technology.

V. EDI Pure Water Treatment

EDI is a new desalination process combining electrodialysis and ion exchange. This equipment leverages the strengths of both electrodialysis and mixed-bed ion exchange, compensating for their respective weaknesses. It utilizes ion exchange for deep treatment without the need for chemical regeneration; the H+ and OH- ions generated by ionization are used to regenerate the resin. EDI has high requirements for the influent; it must be reverse osmosis permeate or water of equivalent quality. It has the following characteristics:

1. It can continuously produce qualified ultrapure water that meets user requirements, with stable water production;

2. It requires no chemical regeneration and has no chemical emissions, making it a green and environmentally friendly product;

3. It has a compact structure, small footprint, and low water production cost;

4. The device is fully commissioned before leaving the factory, making on-site installation and commissioning simple;

5. It is easy to operate, with extremely low labor intensity and easy training.

VI. Ion Exchange Pure Water Treatment

Various inorganic salts in water ionize to generate cations and anions. When passing through a hydrogen-type ion exchanger layer, the cations in the water are replaced by hydrogen ions, which is the desalination principle of a cation bed.

Various inorganic salts in water ionize to generate cations and anions. When passing through an OH-type ion exchanger layer, the anions in the water are replaced by OH- ions, which is the desalination principle of an anion bed.

A mixed bed is an ion exchange device in which cation and anion exchange resins are mixed in a certain proportion and packed in the same exchange column. The uniformly mixed resin layer has cation and anion resins arranged in a close interleaved manner. Each pair of cation and anion resin particles is similar to a set of mixed beds. Therefore, the mixed bed can be regarded as an infinite number of mixed beds operating in series.