During the PCB production process, various substances harmful to the environment are inevitably generated. Besides production capacity, the capability to manage these harmful substances is crucial for modern factories. Implementing “green production” is essential for the contemporary industry. Now, the question arises: how should we address the harmful substances generated during PCB production?
PCB wastewater consists of cleaning wastewater, ink wastewater, complexation wastewater, concentrated acid waste liquid, concentrated alkali waste liquid, and other types. These wastewater streams contain diverse pollutants and complex compounds. The key to ensuring wastewater treatment meets standards lies in targeting the appropriate quality of wastewater treatment.
PCB wastewater treatment primarily involves chemical and physical methods. Chemical methods aim to convert pollutants in wastewater into forms that are easily separable (solid or gas). This includes methods such as chemical precipitation, redox reactions, ion exchange, and electrolysis. On the other hand, physical methods focus on concentrating pollutants in the wastewater or separating them into easily treatable forms to meet discharge standards. Examples of physical methods include sedimentation, electrodialysis, and reverse osmosis.
1. Redox method
The oxidation-reduction method utilizes oxidizing or reducing agents to convert harmful substances in wastewater into less harmful forms, which then precipitate out. Cyanide and chromium-containing wastewater from circuit boards commonly undergo treatment using the oxidation-reduction method.
2. Chemical precipitation
Chemical precipitation involves the use of specific chemical agents to convert harmful substances into easily separable solids or precipitates. Various chemicals like NaOH, CaO, Ca(OH)2, and Na2S are employed in treating PCB circuit board wastewater. These precipitants facilitate the conversion of heavy metal ions into precipitates, which are subsequently separated from the liquid phase through inclined plate sedimentation tanks, PCB sand filters, pressure filters, etc.
3. Ion exchange method
For treating high-concentration wastewater, chemical precipitation is often insufficient and is thus combined with ion exchange. Initially, the chemical precipitation method reduces heavy metal ion content to approximately 5 mg/L, after which the ion exchange method further lowers these ions to meet emission standards.
4. PCB electrolysis
Electrolysis is employed to treat high-concentration circuit board wastewater by reducing heavy metal ion content. However, this method is effective only for treating high-concentration heavy metal ions and consumes significant power. It is suitable primarily for treating individual metals.
5. Gaseous Condensation-Electric Filtration Method
This innovative method comprises three main components. Firstly, an ionized gas generator modifies air within the PCB generator, transforming it into highly activated magnetic oxygen and nitrogen ions by altering its chemical structure via ionized magnetic fields. These ions are introduced into wastewater using a PCB jet device, facilitating oxidation and aggregation of harmful substances such as metal ions and organics, making them easier to filter and remove. Secondly, an electrolytic filter removes aggregates formed in the first step. Finally, a high-speed UV irradiation device oxidizes organic matter and chemical complexing agents in the water, thereby reducing CODcr and BOD5. This integrated approach achieves the desired treatment outcomes.
PCB wastewater consists of cleaning wastewater, ink wastewater, complexation wastewater, concentrated acid waste liquid, concentrated alkali waste liquid, and other types. These wastewater streams contain diverse pollutants and complex compounds. The key to ensuring wastewater treatment meets standards lies in targeting the appropriate quality of wastewater treatment.
PCB wastewater treatment primarily involves chemical and physical methods. Chemical methods aim to convert pollutants in wastewater into forms that are easily separable (solid or gas). This includes methods such as chemical precipitation, redox reactions, ion exchange, and electrolysis. On the other hand, physical methods focus on concentrating pollutants in the wastewater or separating them into easily treatable forms to meet discharge standards. Examples of physical methods include sedimentation, electrodialysis, and reverse osmosis.
1. Redox method
The oxidation-reduction method utilizes oxidizing or reducing agents to convert harmful substances in wastewater into less harmful forms, which then precipitate out. Cyanide and chromium-containing wastewater from circuit boards commonly undergo treatment using the oxidation-reduction method.
2. Chemical precipitation
Chemical precipitation involves the use of specific chemical agents to convert harmful substances into easily separable solids or precipitates. Various chemicals like NaOH, CaO, Ca(OH)2, and Na2S are employed in treating PCB circuit board wastewater. These precipitants facilitate the conversion of heavy metal ions into precipitates, which are subsequently separated from the liquid phase through inclined plate sedimentation tanks, PCB sand filters, pressure filters, etc.
3. Ion exchange method
For treating high-concentration wastewater, chemical precipitation is often insufficient and is thus combined with ion exchange. Initially, the chemical precipitation method reduces heavy metal ion content to approximately 5 mg/L, after which the ion exchange method further lowers these ions to meet emission standards.
4. PCB electrolysis
Electrolysis is employed to treat high-concentration circuit board wastewater by reducing heavy metal ion content. However, this method is effective only for treating high-concentration heavy metal ions and consumes significant power. It is suitable primarily for treating individual metals.
5. Gaseous Condensation-Electric Filtration Method
This innovative method comprises three main components. Firstly, an ionized gas generator modifies air within the PCB generator, transforming it into highly activated magnetic oxygen and nitrogen ions by altering its chemical structure via ionized magnetic fields. These ions are introduced into wastewater using a PCB jet device, facilitating oxidation and aggregation of harmful substances such as metal ions and organics, making them easier to filter and remove. Secondly, an electrolytic filter removes aggregates formed in the first step. Finally, a high-speed UV irradiation device oxidizes organic matter and chemical complexing agents in the water, thereby reducing CODcr and BOD5. This integrated approach achieves the desired treatment outcomes.
