How to treat circuit board wastewater

- Dec 25, 2019-

How to treat circuit board wastewater

    Summary of content: During the process of grinding, etching, plating, hole metallization, development, and film removal of the circuit board production enterprises, circuit board wastewater will be generated. Circuit board wastewater mainly includes the following:

    The complexed and chelated copper-containing wastewater produced by chemical copper deposition and etching processes has a pH value of 9-10 and a Cu2 + concentration of 100-200mg / l.

    A large amount of acidic heavy metal wastewater (non-complexed copper wastewater) generated during the cleaning process before electroplating, grinding, and brushing, including wastewater containing Sn / Pb, pH value is 3 ~ 4, Cu2 + is less than 100mg / l, Sn2 + is less than 10mg / l and trace Heavy metals such as Pb2 +.

    Dry film, film release, development, ink removal, screen cleaning and other processes produce a higher concentration of organic ink waste liquid, and the COD concentration is generally between 3000 and 4000 mg / l.

According to the different characteristics of circuit board wastewater, different wastewater must be diverted during treatment, and different methods should be adopted for treatment.

    1. Complexed copper-containing wastewater (copper ammonia complexed wastewater)

    The heavy metals Cu2 + and ammonia in this kind of wastewater form a relatively stable complex. The copper hydroxide precipitation cannot be formed by the general method of hydroxide coagulation. The complex structure must be destroyed before coagulation and precipitation. Sulfurization is generally used for treatment. Sulfurization refers to the use of S2- in sulfide and Cu2 + in copper-ammonia complex ions to form CuS precipitates to separate copper from wastewater, while excess S2- is used to produce FeS using iron salts. The precipitate was removed.

The processing process is as follows:

    Copper-ammonia complexation wastewater → regulating tank → breaking complex reaction tank → coagulation reaction tank → inclined tube sedimentation tank → intermediate pond → filter → pH callback tank → discharge

    The control of reaction conditions should be determined during commissioning according to the different water quality of each plant. Generally, the pH value is adjusted to neutral or alkaline before adding the sulphide and other disintegrating agents to prevent the generation of hydrogen sulfide. In some cases, the pH is adjusted to be slightly acidic. The dosage of sulfide is determined according to the amount of copper ammonium ions in the wastewater. Generally, excessive drug is administered. An ORP instrument is installed in the breaking cell to measure. When the potential reaches -300mv (empirical value), the sulfide is considered excessive and the reaction is complete. The excessive sulfide is removed by adding ferrous salt, and the amount of ferrous added is determined according to debugging and quantitatively added through a flow meter. The reaction time of the breaking network is 15-20 minutes, and the reaction time of the coagulation reaction pool is 15-20 minutes.

   2.Ink wastewater

   Due to the small amount of water, the stripped and deinked wastewater is generally treated intermittently. The organic ink is separated from the wastewater to produce suspended matter under acidic conditions and removed. The pretreated ink wastewater can be mixed into the comprehensive wastewater. It can be used for subsequent treatment together with it. If the amount of water is large, it can be treated by biochemical method alone.

The processing process is as follows:

   Organic ink waste water → acidification slag removal pond → discharge into comprehensive waste water pond or biochemical treatment

   When the amount of wastewater is small, the ink particles in the reaction tank float on the surface of the water under the action of bubbles to form scum, which can be skimmed manually; when the amount of water is large, it can be dewatered with a plate and frame filter press, or can be skimmed After biochemical treatment, COD is further removed.

  3.Circuit board comprehensive wastewater

    This type of wastewater mainly includes comprehensive wastewater containing acid and alkali, Cu2 +, Sn2 +, Pb2 + and other heavy metals. The treatment method is the same as that of electroplating integrated wastewater, and it is treated by the coagulation precipitation method of hydroxide.

  4. Comprehensive treatment of multiple circuit board wastewater

    When a circuit board factory contains the above types of circuit board wastewater, copper ammonia complex wastewater, ink wastewater, and comprehensive heavy metal wastewater should be collected separately. After the ink wastewater is pretreated, it is mixed into the integrated wastewater for subsequent treatment with copper ammonia. The complex wastewater is treated separately and enters the integrated wastewater treatment system.

The processing process is as follows:

   Copper-ammonia complex wastewater → regulatory pond → broken-collar reaction pond → coagulation reaction pond → inclined tube sedimentation pond → intermediate pond

   Organic ink waste water → acidification slag removal tank → discharged into comprehensive waste water tank

Integrated wastewater → Integrated wastewater tank → Fast mixing tank → Slow mixing tank → Oblique tube sedimentation tank → Intermediate tank → Filter → pH callback tank → Discharge

Previous:How to prevent others from copying your PCB board? Next:Precautions when PCB copper