In today's information society, the electronics industry is developing rapidly, and PCB circuit boards have become one of the important industries in the electronics industry, but a large amount of waste water will be generated in the production process of PCB circuit boards. Since the manufacturer of circuit boards is a very complex and comprehensive processing technology, chemical materials of different properties are used in the production process, which constitutes the complexity of its wastewater.
During the processing, the waste water produced by different production processes contains pollutants of different properties, including heavy metal compounds, organic polymer compounds and various organic additives. If it is directly discharged without effective treatment, it will inevitably cause serious pollution to the surrounding water environment.
I. Features of PCB Circuit Board Wastewater
1. The printed PCB production process of the circuit board factory needs to go through dozens of production processes such as inner layer treatment, electroplating, outer layer treatment, surface processing and final treatment, which will produce various wastewater, and the composition of each kind of wastewater is very different.
2. The production process of PCB printed circuit boards is complex, and different wastewater will be produced in different production stages, and the composition of various wastewater is also different.
3. The production wastewater of PCB printed circuit boards can be divided into single-panel, double-panel and multi-panel production wastewater according to different wiring levels.
4. According to the types and forms of pollutants in the wastewater, it can be divided into wastewater containing heavy metals (containing Cu2+ 、Pb2+ 、Ni2+, without complexing agents such as EDTA and NH4+ ), wastewater containing fluorine, wastewater containing complexes (containing heavy metal ions, complexing agents, including heavy metal-EDTA complexes and heavy metal-ammonia complexes), and acid and alkali wastewater (including dissolved organic matter, inorganic acid and alkali, CN-, etc.)
5. In addition, a large amount of wastewater will be generated in the production process of printed circuit boards, mainly membrane wastewater, chemical copper wastewater and other bath liquids and electroplating liquids.
II. Treatment Technology of Printed Circuit Board Wastewater
Due to the many nodes and complex components of printed circuit board wastewater, the current methods for treating wastewater mainly include coagulation sedimentation, ion exchange, air flotation, adsorption, iron-carbon micron-electrolysis, membrane separation, and catalytic oxidation, biodegradation method and combined treatment method, etc.
The adsorption method is to use porous solid adsorbents to treat pollutants. One or several components of the pollutants are adsorbed on the solid surface under the action of molecular attraction or chemical bonds, so as to achieve the purpose of separation. Commonly used adsorbents are activated carbon, humic acid, sepiolite, polysaccharide resin, etc. The advantages of the adsorption method are fast speed, good stability, and small equipment footprint. Its main disadvantages are high investment, difficulty in adsorbent regeneration, and high pretreatment requirements.
2. Iron Carbon Micro-electrolysis
The electrolytic materials of the iron-carbon micro-electrolysis process generally use cast iron scraps and activated carbon or coke. When the material is immersed in wastewater, both internal and external electrolytic reactions occur. The products produced by the electrode reaction have high activity and can undergo redox reactions with various components in wastewater, and many refractory and toxic substances can be effectively degraded. At the same time, the metal can undergo a replacement reaction with the heavy metal ions in the wastewater whose activities are ranked after the iron.
3. Membrane Separation Method
At present, membrane separation methods mainly include electrodialysis, microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO), etc. Firstly, conventional pretreatment technologies such as manganese sand filtration and chlorine sterilization are use, then through microfiltration system, the primary treated wastewater can meet the requirements of RO device for influent water. Finally, the anti-ollution RO membrane element is selected, which can realize zero discharge of industrial wastewater pollutants and reuse of wastewater.
Hongtek provides a series of microfiltration products, such as melt blown cartridges, string wound cartridges and Pleated Filter Cartridges, that are suitable for pre-filtration of printed circuit board wastewater with high removal efficiency and simple operation.
What's more, the PPH Plastic Housing that Hongtek supply could be perfect choice to be used in the prefiltration process of printed circuit board wastewater. The plastic filter housing is integrally formed, no welding, the structure is firm, safe and reliable, with simple installation, and it is economical and durable. The special material PPH can be used for filtration of most chemicals and has corrosion resistance to most chemicals.
4. Biodegradation Method
The biological method is suitable for the treatment of organic wastewater containing low metal ions, such as the comprehensive wastewater formed by the washing water of electroplating, etching, template, mold release and ink removal. The application of biological methods is mainly based on water quality conditions, combining different pretreatment methods to improve the biodegradability of refractory organic matter. The main disadvantages of biological method are long processing time, great influence by external environment, instability, etc. The complexity of the microbial structure determines that the mechanism of microbial treatment of printed circuit board wastewater is very complex, and has not yet been uniformly recognized.