Transformation process of cathode lead structure in the recovery of waste lead paste by suspension electrolysis

Abstract

Lead is directly recovered for reuse from waste lead paste by suspension electrolysis. However, the industrial-scale application of the extracted lead is limited by the extremely low reduction rate of cathodic metallic lead during electrolysis. We used constant voltage suspension electrolysis of waste lead paste to investigate the evolution of lead product components and morphological characteristics during cathode deposition. To determine the reasons for the low reduction rate of lead in suspension electrolysis, we compared the results with those of the electrolysis of pure lead compounds. The experimental results showed that at the beginning of the suspension electrolysis, the cathode surface first deposits flower cake PbO2 primary crystals, which are then gradually reduced to PbOx flake crystals. Some flake crystals are further reduced to PbO, which is converted to PbSO4 under acidic conditions, forming a (PbO)x(PbSO4)y complex salt with PbO and finally being deposited to form an amorphous three-dimensional spongiform structure. The amorphous three-dimensional spongiform structure has poor electrical conductivity, limiting its further reduction to metallic lead. These findings provide a prospective approach for reusing waste lead paste.

Keywords

• Suspension electrolysis
• Waste lead paste
• Amorphous three-dimensional spongiform structure
• Electrical conductivity