Method for electrolyzing high-quality nickel from electroless nickel plating wastewater

Abstract

A method for electrolyzing high-quality nickel from electroless nickel plating wastewater is disclosed, according to the method, the electrolysis current efficiency can be improved greatly, and a nickel layer which is uniform, compact and flat and with metallic luster can be obtained. The method for electrolyzing the high-quality nickel from the electroless nickel plating wastewater includes the following steps of (1) collecting electroless nickel plating wastewater by using a collecting tank; (2) adjusting the PH value of the collected wastewater to an alkalescence condition under which hydrogen evolution side reaction can be reduced; (3) adding polyvinyl alcohol with a volume percent concentration of 1%-5% and sodium persulfate with a mass percent concentration of 1%-10% to the wastewater and mixing, and standing for 12-24 hours; and (4) draining the wastewater being conducted standing to an electrolytic tank and conducting nickel electrolysis. The method for electrolyzing high-quality nickel from the electroless nickel plating wastewater is completely different with traditional electrolysis technologies, the current efficiency can reach to 70%, the COD degradation rate can reach to 70%, and the amount of total phosphorus is decreased 60%; by adoption of the method, the nickel layer which is uniform, compact and flat and with the metallic luster can be obtained, so that the effect of recycling nickel sources is achieved, meanwhile, organics can be degraded and total phosphorus can be removed, and accordingly the method has good application prospects.

Description

technical field [0001] The invention relates to an electrolysis process, in particular to a process for electrolyzing high-quality nickel from chemical nickel plating wastewater. Background technique [0002] As we all know, industrial electroless nickel plating is carried out in an acidic system with sodium hypophosphite as a reducing agent. In order to ensure the stability, service life and coating quality of the plating solution, complexing agents, stabilizers, accelerators, pH buffer and brightener. These substances are all organic matter, such as: citric acid, tartaric acid, malic acid, glycolic acid, succinic acid, succinic acid, acetic acid or the like, and complexing agents are added in more amounts in the electroless plating solution. It has strong complexation and forms a stable complex state with nickel. When the aqueduct ages, electroless nickel plating wastewater will be produced. Usually, the nickel content in the wastewater is 2-7g / L, the COD is 40000-70000m...

AI Technical Summary

Problems solved by technology

But hydrogen has a more positive potential than nickel, and hydrogen is easier to precipitate. Although in the actual electrolysis of nickel metal, there is an overvoltage of the electrode reaction due to polarization. As a result of polarization, hydrogen ions are on the cathode. The precipitation potential changes to a more negative direction, making it possible for nickel ions to be electrolyzed by discharge

However, in the electroless nickel plating wastewater, due to the high concentration of organic matter and the low concentration of nickel ions existing in a complex form, the side reactions of oxygen evolution and hydrogen evolution in electrolytic nickel plating wastewater are serious.

That is to say, due to the serious concentration polarization, the treatment capacity per unit tank is small, the electrolysis efficiency is low, and the amount of nickel obtained from the cathode is small, resulting in a small amount of nickel precipitation.