In recent years, the technological enterprises in CHINA's mining industry have made great progress, and various enterprises have come out one after another, which has played an important role in diverting talents and invigorating enterprises. Among them, the development of electronic technology companies is the most eye-catching . Various integrated circuits and electronic instrument products have been used in production in varying quantities. In the mass production of integrated circuits and electronic instruments , pure water with different purities must be used to clean the parts. And the purity of pure water (the amount of pollutants) directly affects the performance and yield of electronic products. For example, in solid-state circuits, due to the extremely small distance between adjacent components (only 0.1 mil), that is to say, particles larger than 0.1 mil are enough to overlap the functions of the integrated circuit, resulting in failure or failure of the microcircuit Short circuit, so that the products are scrapped in batches. Therefore , with the development of scientific and technological enterprises, especially the development of electronic enterprises, the requirements for pure water are getting higher and higher. Facing numerous water treatment technologies, how to choose a more representative combined treatment method to remove various pollutants in water has aroused widespread concern.
1 Factors affecting the preparation of pure water
At present, most of the pure water preparations in industrial and mining enterprises in CHINA use drinking tap water as the water source. Drinking tap water, although in line with the national "Drinking Water Hygienic Standards", still contains colloidal substances, Graduation substances, oxides and organic substances. Among them, colloidal substances rely on molecular Brownian motion, electrostatic repulsion, and hydration to maintain a dispersed and suspended state for a long time, and become the main pollutants in the process of pure water preparation. Oxide is the product of disinfection of tap water by adding chlorine, usually in the form of Cl2, HClO, ClO -1 and NHCl2, which has a great influence on the preparation of pure water. Organic matter is mainly macromolecular organic acid. When its content is high, it will form flocs with flocculant in the pretreatment process, causing filter pollution. At the same time, the negative charge carried by this organic matter interacts with anions. The positive charge of the exchange resin produces suction, which causes it to be adsorbed on the anion exchange resin, blocking the micropores of the resin and reducing the exchange capacity. Graduation substances exist in the form of carbonate, sulfate and silicon dioxide . Once Graduation is formed, it is very difficult to clean.
2 Discussion on water pre-treatment methods and combined processes
2.1 Pretreatment method
There are many methods of pretreatment of water, and these methods have their own characteristics. Several representative methods are described below.
(1) Multi-media filtration. In the pretreatment process of pure water preparation, multi-media filtration is generally used as a primary filtration, that is, coarse filtration. This kind of filtration is to add an organic cationic polymer to make it mix to form flocs without sedimentation, and directly intercept a large amount of pollutants through the multi-media filter material, thereby completing the coarse filtration.
(2) Microporous filtration and activated carbon adsorption. Microporous filtration is secondary filtration. Aluminum alloy water filters, ceramic sand filter rods, etc. are commonly used as microporous filtration equipment, and the effect is satisfactory. Activated carbon is a granular adsorption medium, which has a strong adsorption capacity for odor, poisonous gas, grease, residual chlorine , and has a very good effect on chlorine removal.
(3) Fine filter. The fine filter uses macroporous Cl type soda ash cation exchange resin as the organic adsorption column. Due to the unique structure of the resin (macroporous), it is easy to adsorb organic matter, and after saturation, it can be regenerated with a mixture of 2% NaOH and 10% NaCl, so it has certain practical and promotional significance.
(4) Electrodialysis. Electrodialysis is to use an ion exchange membrane to selectively permeate ions in water under the action of an external electric field , so as to achieve the purpose of separating solute and solvent.
(5) Membrane separation technology. Membrane separation methods mainly include reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF) and other membranes, and their main characteristics are shown in Table 1.
The reverse osmosis (RO) filter membrane has a small pore size of about 0.1-1nm . It can be considered as a broad-spectrum filter membrane, which can filter particles, bacteria, organic matter, and colloids in a wide range, and the filtration efficiency can reach 90%. It not only has strong adaptability to water quality changes, but also has certain stability in the process of treatment. It can not only separate organic substances with different molecular weights, but also separate inorganic electrolytes. NF membrane has the characteristics of lower energy consumption and higher recovery than reverse osmosis membrane in the removal of low molecular weight organic matter and inorganic salt in water, and it is a very potential separation technology. UF ultrafiltration can separate solutes with a molecular weight greater than 500, and the required working pressure is 0.3-0.7 MPa. This method can remove bacteria with a particle size of 0.3 μm and infectious .
2.2 Discussion on combination process
According to the experimental research , the author believes that the advanced treatment of tap water with NF membrane combination technology is more satisfactory. The NF membrane combination process is shown in Figure 1.
In the above process, the multi-media filter is a commonly used coarse filtration method; the activated carbon system uses a carbon column with a thickness of 
12mm× 300mm, a packing height of 1500mm, and a particle size of 
2mm to 4mm; the filter element of the fine filter is 
100mm×250mm. Provide qualified ; the pump is designed to provide a certain pressure for the NF membrane, usually the operating pressure is 0.5-1.1MPa ; the NF membrane system used is produced by the American TRISEP company.
Using the process shown in Figure 1 and under the relevant conditions, the relationship curves of water production, recovery rate and desalination rate are shown in Figure 2 and Figure 3. It can be seen from Figure 2 and Figure 3 that when other process conditions remain unchanged and the pump pressure is stable at 0.9MPa, the water production rate is 39L/h, the recovery rate is 19%, and the desalination The results of the water quality analysis are shown in Table 2.
It can be seen from Table 2 that the removal effect of various pollutants in water by the NF membrane combination process is satisfactory. The experimental discussion shows that the advanced treatment of tap water by the NF membrane combination process is a satisfactory process.
3 Conclusion
According to the actual needs of enterprise production, the preparation of pure water will be taken for granted, and it will undoubtedly have important practical significance to explore a reasonable process flow . Through the analysis of this paper, the following conclusions can be drawn:
(1) Advanced treatment of tap water by NF membrane combination technology, the process is simple and reasonable;
(2) Using the process shown in Figure 1, when the original pressure is 0.9MPa, the water production rate can reach 39L/h, the recovery rate is 19%, and the desalination rate reaches 94.3%, and the effect is good;
(3) NF membranes will have broad .
