I. Introduction to electroless nickel plating process
Electroless plating is a process in which electrons are supplied by a reducing agent to reduce metal ions to a metal plated surface of the plated member. Unlike electroplating, electroless plating does not require an external power source, but rather a chemical deposition process through a redox reaction.
Electroless nickel plating, which is currently popular on the market, is acid electroless nickel plating with hypophosphite as a reducing agent. In electroless nickel plating bath, nickel ions are mainly supplied by nickel sulfate, and the reducing agent is mostly sodium hypophosphite. Sodium phosphate is relatively reductive and provides the electrons required for nickel ions during the electroplating process. In addition, in electroless nickel plating, an organic acid or a salt thereof is required as a complexing agent, and the complexing agent can combine with nickel ions to form complex complex ions, thereby avoiding the formation of nickel hypophosphite precipitate, which is common in electroless nickel plating. Complexing agents include glycolic acid, citric acid, lactic acid, malic acid, succinic acid, and the like. Organic acids having an excessively long carbon chain are generally not used as complexing agents.
Second, the composition of chemical nickel wastewater
The main source of chemical nickel wastewater is the cleaning water of electroless nickel plating solution. The complexing agent and sodium hypophosphite are present in the electroless nickel electroplating solution. Therefore, the main components of the chemical nickel wastewater are hypophosphorous acid and complex nickel, which are corresponding to the electroplating wastewater treatment index. Nickel content and phosphorus content.
For complex nickel, since the complexing agent and nickel ion can be stably combined, causing alkali precipitation in the nickel-containing wastewater, the conventional liquid recapture agent or sodium sulfide has limited chelating ability, and it is difficult to remove nickel ions. The complexing agent is taken away.
For sodium hypophosphite, unlike normal orthophosphorus, sodium hypophosphite cannot be precipitated by lime, and treatment by oxidation does not completely oxidize hypophosphite to orthophosphate, so phosphorus cannot be removed.
Third, chemical nickel treatment agent
For chemical nickel wastewater, phosphorus removal needs to be treated with the sub-phosphorus remover P3. In addition to nickel, it needs to be treated by the nickel removal agent M2, and the nickel phosphorus can be treated to the standard of Table 3.
The sub-phosphorus remover P3 is an inorganic composite salt, which can directly combine with hypophosphite ions to form a precipitate under the catalytic action of hydrogen peroxide in wastewater; the high-efficiency nickel removal agent is an organic compound, and the principle of chelation is adopted. The complexing agent in the complexed nickel is destroyed to combine with nickel ions to form a precipitate.
Fourth, the electroless nickel plating wastewater treatment steps
The chemical nickel wastewater is treated with the sub-phosphorus remover P3 and the high-efficiency nickel removal agent M2. The specific steps are as follows:
1. First take electroless nickel plating wastewater to adjust the pH of the wastewater.
2. Adding the sub-phosphorus remover P3 to carry out the reaction, and simultaneously adding hydrogen peroxide to carry out the catalytic reaction.
3. Adjust the pH of the wastewater and add PAM for flocculation and sedimentation.
4, precipitated water, phosphorus can reach the standard.
5, adjust the pH of the wastewater to alkaline
6. Add high-efficiency nickel removal agent M2 for reaction
7. Add PAC coagulation, PAM flocculation and sedimentation
8, the water, nickel can reach the standard
By treating the chemical nickel wastewater through the above process, both nickel and phosphorus can reach the standard, wherein the nickel concentration can be treated to below 0.1 mg/L, and the phosphorus concentration can be treated to below 0.5 mg/L.
V. Precautions for the treatment of electroless nickel plating wastewater
Treatment of chemical nickel wastewater with sub-phosphorus remover P3 and high-efficiency nickel removal agent M2:
1, the pH of the reaction is critical, in the use of sub-phosphorus remover P3 treatment, need to control the pH
2, you can take the first step to remove phosphorus, then remove nickel to treat chemical nickel wastewater
3. The treatment of chemical nickel wastewater by using the sub-phosphorus remover P3 and the high-efficiency nickel removal agent M2 can treat the phosphorus to below 0.5 mg/L and the nickel to below 0.1 mg/L.
4. This method can be used to treat chemical nickel wastewater. This method can also be used to treat copper electroplating wastewater.
Electroless plating is a process in which electrons are supplied by a reducing agent to reduce metal ions to a metal plated surface of the plated member. Unlike electroplating, electroless plating does not require an external power source, but rather a chemical deposition process through a redox reaction.
Electroless nickel plating, which is currently popular on the market, is acid electroless nickel plating with hypophosphite as a reducing agent. In electroless nickel plating bath, nickel ions are mainly supplied by nickel sulfate, and the reducing agent is mostly sodium hypophosphite. Sodium phosphate is relatively reductive and provides the electrons required for nickel ions during the electroplating process. In addition, in electroless nickel plating, an organic acid or a salt thereof is required as a complexing agent, and the complexing agent can combine with nickel ions to form complex complex ions, thereby avoiding the formation of nickel hypophosphite precipitate, which is common in electroless nickel plating. Complexing agents include glycolic acid, citric acid, lactic acid, malic acid, succinic acid, and the like. Organic acids having an excessively long carbon chain are generally not used as complexing agents.
Second, the composition of chemical nickel wastewater
The main source of chemical nickel wastewater is the cleaning water of electroless nickel plating solution. The complexing agent and sodium hypophosphite are present in the electroless nickel electroplating solution. Therefore, the main components of the chemical nickel wastewater are hypophosphorous acid and complex nickel, which are corresponding to the electroplating wastewater treatment index. Nickel content and phosphorus content.
For complex nickel, since the complexing agent and nickel ion can be stably combined, causing alkali precipitation in the nickel-containing wastewater, the conventional liquid recapture agent or sodium sulfide has limited chelating ability, and it is difficult to remove nickel ions. The complexing agent is taken away.
For sodium hypophosphite, unlike normal orthophosphorus, sodium hypophosphite cannot be precipitated by lime, and treatment by oxidation does not completely oxidize hypophosphite to orthophosphate, so phosphorus cannot be removed.
Third, chemical nickel treatment agent
For chemical nickel wastewater, phosphorus removal needs to be treated with the sub-phosphorus remover P3. In addition to nickel, it needs to be treated by the nickel removal agent M2, and the nickel phosphorus can be treated to the standard of Table 3.
The sub-phosphorus remover P3 is an inorganic composite salt, which can directly combine with hypophosphite ions to form a precipitate under the catalytic action of hydrogen peroxide in wastewater; the high-efficiency nickel removal agent is an organic compound, and the principle of chelation is adopted. The complexing agent in the complexed nickel is destroyed to combine with nickel ions to form a precipitate.
Fourth, the electroless nickel plating wastewater treatment steps
The chemical nickel wastewater is treated with the sub-phosphorus remover P3 and the high-efficiency nickel removal agent M2. The specific steps are as follows:
1. First take electroless nickel plating wastewater to adjust the pH of the wastewater.
2. Adding the sub-phosphorus remover P3 to carry out the reaction, and simultaneously adding hydrogen peroxide to carry out the catalytic reaction.
3. Adjust the pH of the wastewater and add PAM for flocculation and sedimentation.
4, precipitated water, phosphorus can reach the standard.
5, adjust the pH of the wastewater to alkaline
6. Add high-efficiency nickel removal agent M2 for reaction
7. Add PAC coagulation, PAM flocculation and sedimentation
8, the water, nickel can reach the standard
By treating the chemical nickel wastewater through the above process, both nickel and phosphorus can reach the standard, wherein the nickel concentration can be treated to below 0.1 mg/L, and the phosphorus concentration can be treated to below 0.5 mg/L.
V. Precautions for the treatment of electroless nickel plating wastewater
Treatment of chemical nickel wastewater with sub-phosphorus remover P3 and high-efficiency nickel removal agent M2:
1, the pH of the reaction is critical, in the use of sub-phosphorus remover P3 treatment, need to control the pH
2, you can take the first step to remove phosphorus, then remove nickel to treat chemical nickel wastewater
3. The treatment of chemical nickel wastewater by using the sub-phosphorus remover P3 and the high-efficiency nickel removal agent M2 can treat the phosphorus to below 0.5 mg/L and the nickel to below 0.1 mg/L.
4. This method can be used to treat chemical nickel wastewater. This method can also be used to treat copper electroplating wastewater.
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