Electronucleation mechanism of copper in wastewater by controlled electrodeposition analysis

Abstract

In order to improve the efficiency of copper deposition in wastewater containing the surfactant polyvinylpyrrolidone (PVP) and reveal the mechanism of copper crystals, a controlled electrodeposition process was developed using a low-cost stainless steel cathode and investigated using chronoamperometry (CA), electrochemical impedance spectroscopy (EIS) and infrared spectroscopy (IR). The theoretical analysis was verified by fitting them to experimental curves and calculating the kinetic parameters of the deposition process. The experimental results showed that Cu(PVP)₂ was formed by the reaction between the CO bond of PVP and Cu²⁺. When powdered, reduction of Cu²⁺ in the Cu(PVP)₂ structure was promoted, a positively-charged PVP-coating layer was formed on the surface of the copper crystal nuclei to inhibit the growth of the copper powder. At a potential of −0.2 V, the electrodeposition crystallization curve of copper changed from progressive nucleation to instantaneous nucleation. The kinetic parameters of the deposition process were calculated by fitting the experimental curves to verify the correctness of the theoretical analysis. The EIS tests showed that removing the powder reduced the resistance of the organic solvent (PVP) film on the electrode surface and the charge transfer resistance during copper deposition. According to particle size analysis, removing the powder could reduce the growth energy of copper powder on the electrode surface, increase the area of the active part on the electrode surface, increase the current efficiency of copper powder to 84.2%, and control dust. The size of copper powder reached up to around 900 nm.