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Factors affecting the quality of electrowinning silver powder:
1. Current density, the higher the current density, the worse the quality of silver powder produced. A higher cathode current density can be used when the coarse silver anode has a high silver content, a high concentration of silver ions in the electrolyte, and a low concentration of impurity ions. The current density is generally 300~800A/m2, the silver content in the anode is generally above 98%, and the silver content in the electrolyte is generally above 100g/L.
2. Electrolyte circulation volume, a large circulation volume is conducive to ion diffusion to reduce concentration polarization, generally choose 4~10 times of tank/hour.
3. Anode composition: Au+Ag>97%;
4. Composition of electrolyte: Ag=100-150g/L, HNO3=8g/L-15g/L;
5. Washing method of silver powder: Soak and wash with 5% nitric acid solution for 2 times, then wash with >60°C deionized water until neutral, then centrifugally dehydrate.
6. Electrolytic silver refining operation control: pay attention to whether the anode bag is damaged, whether the gloves, tools and containers are clean, and pay attention to environmental hygiene.
