Briefly describe the wastewater discharge generated by each production process of electroplating

Most electroplating plants are comprehensive multi-plating operations involving chromium, nickel, zinc, copper, etc., from The types of plated parts can be divided into metal plated parts and plastic plated parts. Although most of the cyanide-containing electroplating process is eliminated, many electroplating plants are still in use.

The production process of the general electroplating factory is as follows: the electroplating production process is mainly mechanical polishing (polishing or rolling) → degreasing → acid etching → electroplating → drying → qualified products storage

Unqualified products deplating

The electroplating industry implements cleaner production

Clean production refers to continuously adopting measures such as improving design, using clean energy and raw materials, adopting advanced technology and equipment, improving management, and comprehensive utilization to reduce pollution from the source, improve resource utilization efficiency, and reduce or avoid production, The production and discharge of pollutants during the use of services and products to reduce or eliminate harm to human health and the environment. [2]

Plating parts pretreatment mechanical polishing (polishing or barreling)

Mainly by means of special machinery, the use of grinding wheels or belts in the machinery (or abrasives to remove some plated parts using rollers and abrasives to remove rust) to remove burrs, scratches, weld bumps, blisters, etc. on the plated parts , In order to improve the flatness of the plated parts and improve the quality of the plated parts. There is no waste water discharge in this process.

Degreasing

Plated parts of metal products, due to various processing and treatments, will inevitably adhere to a layer of oil stains. In order to ensure a firm bond between the plating layer and the substrate, the oil stains on the surface of the plated parts must be removed. There are many degreasing processes, mainly using organic solvents for degreasing. The process is as follows:

Parts after polishing→clean water→organic solvent degreasing tank→clean water tank→clean water rinse

The waste water in this process mainly comes from the clean water washing process, and the pH value of the water is between 8.5-10.

Erosion

The parts after degreasing often have a lot of rust and thick oxide film on the surface. In order to obtain a bright coating and better bond the coating with the substrate, the rust and oxide film on the parts must be removed , It can also activate the surface of parts after acid soaking. The process is as follows:

Parts after degreasing→acid water tank→recovery tank→clean water tank→clean water rinse

The wastewater in this section mainly comes from the clean water washing process. The wastewater contains a large amount of iron ions, and the PH value is between 2 and 5.

The electroplating production process and the water quality of each plating species

The production process is generally: parts after etching treatment → electroplating tank → recovery tank → clean water tank → clean water rinse.

The waste water of this section mainly comes from the clean water washing process, the waste water contains corresponding metal ions or cyanide, and the cyanide copper plating washing water contains cyanide and copper ions; Chrome plating flushing water contains hexavalent chromium; Nickel plating flushing water contains nickel ions, etc. The flushing water is divided into different effluents according to the plating species. For example, the cyanide-containing wastewater is divided into two stages of cyanide breaking, PH value adjustment, and solid-liquid separation can reach the standard discharge; after the chromium-containing wastewater is divided, it undergoes a reduction reaction, and then undergoes neutralization and neutralization. Standard discharge can be achieved after solid-liquid separation.

Drying into storage

This process mainly uses mechanical, natural and thermal energy to dry the moisture on the surface of the parts after electroplating to avoid rust and damage to the oxide film. There is no waste water discharge in this process.

Deplating

The deplating process has two methods: chemical impregnation and anode electrolysis. The process is:

Unqualified plating parts→deplating tank→recovery tank→clean water tank→wash with clean water.

The PH of wastewater in this section is between 2~6, and the wastewater mainly comes from the rinse water after deplating. The deplating rinsing water can enter the respective waste water tank for treatment, but cannot directly enter the waste water mixed treatment tank. It should be pretreated separately and then discharged into the corresponding waste water treatment branch.