Electroplating wastewater source and water quality analysis is the basis of wastewater treatment engineering process design.

1. Pre-treatment of wastewater

The surface pretreatment consists of two main processes: oil removal and oxidation film removal. The workpiece usually USES surfactant emulsification to remove oil, and the Chemical Oxygen Demand (COD) of this part of wastewater is relatively high. The selection of oxidation film removal process is closely related to the substrate material. Usually, the treatment solution is composed of various acids, and this part of the wastewater contains metal ions of the substrate material. In general, the pretreatment process is mainly acidic and alkaline wastewater, including Ni2+, Cu2+, Ag+, Fe2+, Fe3+, COD and other pollutants.

Plating wastewater

According to the production process, electroplating wastewater is mainly divided into the following three categories:

1. Chromium-containing wastewater: chromium-containing wastewater mainly comes from the chromium-anhydride pickling of silver alloy, chromium-anhydride passivation of copper alloy and luminescence of silver coating and other processes. The wastewater mainly contains Cr6+ and a very small amount of metal ions such as Cu2+ and Ag+.

2. Nickel wastewater: there are two main sources of nickel wastewater: electroplating nickel and electroless nickel plating. The nickel plating wastewater mainly comes from the rinse water of acidic nickel plating production line, and the wastewater mainly contains NiSO4, NiCl2, etc. The composition of electroless nickel plating wastewater is complex, which usually contains complexing agent, stabilizer, pH value buffer and so on.

3. Cyanide-containing wastewater: cyanide-containing wastewater is generated by cyanide-bearing copper plating, cyanide-bearing silver plating and gold plating. The wastewater contains CN-, Cu2+, Ag+ and other pollutants.

Waste plating solution and back plating solution

Due to the service life of the plating solution to reach, plating bath process and plating parts back reasons will produce waste plating solution and plating solution, the waste liquid concentration is higher, its composition is complex, usually can separate collection and pretreatment in slow after adding to the corresponding wastewater processing, also can separate collection, entrust the external qualification units for processing.

Water intake and quality

Mass separation is the premise of wastewater treatment, so it is necessary to define the type of wastewater discharged from each plating bath, measure the discharge of each wastewater and control the direction of surface drainage.

The pretreatment wastewater belongs to acid and alkali wastewater. Cyanide-containing plating bath wastewater belongs to cyanide-containing wastewater; The chromium-containing anhydride plating wastewater belongs to chromium-containing wastewater. After preliminary treatment, electroless nickel plating wastewater is classified as nickel containing wastewater. The wastewater from washing plating bath and workshop floor is classified into corresponding wastewater.

Electroplating wastewater treatment process mainly includes chemical method, electrolysis method, adsorption method, reverse osmosis method, etc. At present, the treatment process with stable treatment effect, strong adaptability, low treatment cost and simple management is still chemical method, adding alkaline solvent to make metal ions in wastewater form hydroxide floc, and then precipitation separation and removal.