Treatment methods for printed circuit board wastewater

　　The production process of printed circuit boards (PCBs) produces wastewater with complex components, including heavy metal ions such as copper and nickel, as well as complex/chelate components such as ammonia and EDTA. If not properly treated, it will cause serious environmental pollution. At present, the mainstream treatment methods in the industry are centered on chemical coagulation and ion exchange, and the combination of the two has become the preferred solution for dealing with complex wastewater.

　　Chemical coagulation: basic and efficient primary treatment

　　The chemical coagulation method is to add coagulants (such as ferrous sulfate, polyaluminum chloride, etc.) to the wastewater to form flocs through adsorption, bridging, precipitation, etc., and then remove pollutants through solid-liquid separation.

　　The core advantages are economy and convenience: low initial investment, no need for complex equipment; simple operation process, easy for workers to master; mainly consume coagulants during operation, the cost is relatively low, suitable for small and medium-sized enterprises or large-scale wastewater treatment scenarios.

　　However, this method has obvious limitations: for multilayer circuit board wastewater containing complexing components (such as ammonia) and chelating components (such as EDTA), since these components will form stable soluble complexes with heavy metals, it is difficult for coagulants to effectively destroy their structures, resulting in unstable treatment effects and difficulty in ensuring that wastewater continues to meet discharge standards, especially when the water volume is large, the difficulty of meeting standards is further increased.

　　Ion exchange method: precise and stable deep treatment

　　The ion exchange method is based on the reversible exchange reaction between ion exchangers (mainly ion exchange resins) and target ions (such as copper ions) in wastewater to achieve the separation and removal of pollutants. Commonly used ion exchange resins can be divided into strong acid, strong alkaline, weak acid, weak alkaline and other types according to their exchange capacity, and can adsorb specific ions in a targeted manner.

　　The outstanding feature of this method is that the treatment effect is stable and reliable: the copper ion concentration in the wastewater can be controlled at 0.01mg/L-0.30mg/L, which is far below the discharge standard; and it is not affected by complexing/chelating components, and can deeply purify the wastewater. In addition, ion exchange resins can be recycled through regeneration, which can reduce the loss of consumables to a certain extent.

　　However, its shortcoming is the high cost: the initial investment in treatment facilities is large, especially in large-scale wastewater treatment scenarios; resin regeneration during operation requires the consumption of acid, alkali and other reagents, and the long-term operating cost is significantly higher than the chemical coagulation method, which is more suitable for precision treatment scenarios with extremely high requirements for effluent quality or small treatment volume.

　　Combined process: the optimal solution to balance cost and effect

　　With the technological innovation of the circuit board industry, the components of wastewater pollution are becoming increasingly complex, and a single process is difficult to take into account both standard discharge and economic feasibility. Therefore, the process of combining chemical coagulation and ion exchange is widely used: using chemical coagulation and sedimentation as the main treatment process, first remove most of the heavy metal ions and suspended solids in the wastewater to reduce the subsequent treatment load; then using ion exchange as a deep treatment unit, the residual trace heavy metals (especially complexed heavy metals) are accurately removed as the "last line of defense" for standard discharge.

　　This combined process has significant advantages: it retains the characteristics of low investment and low operating costs of the chemical coagulation method, and with the help of the stability of the ion exchange method, it ensures that even in the face of complex wastewater or water volume fluctuations, it can still meet the discharge standards stably, achieving a balance of "low cost + high reliability", and becoming the mainstream choice for current circuit board wastewater treatment.

　　Industry Application and Trends

　　At present, a mature system has been formed for the treatment of circuit board wastewater at home and abroad. Chemical coagulation and ion exchange methods, as basic technologies, are constantly optimized in practice. With the increasingly stringent environmental protection standards and the complexity of wastewater components, the combined process of the two will be further improved, such as improving the ability to break complexes by improving coagulants, or developing low-cost, highly selective ion exchange resins to reduce operating costs. In the future, circuit board wastewater treatment will develop in the direction of "high efficiency, low cost, and resource utilization", achieving the recycling of heavy metals while meeting discharge standards, and promoting the green and sustainable development of the industry.