Separating Silver from Tin Silver Alloy Residue: Effect of Agitation Rate

Abstract

In this paper, research on the effects of agitation rate for desilvering tin silver alloy residue by using pyrometallurgy was carried out. SnAg alloy residue with 92 wt.% tin and 3.56 wt.% silver was used in this study, and 99.999 wt.% zinc was added as metal solvent. Residues were melted to a temperature of 400 °C for enriching tin silver alloy. The obtained tin silver alloy was melted in a temperature range of 450 °C to 500 °C by adding zinc to evaluate zinc dissolution. The obtained tin silver zinc was agitated at different agitation rates for 20 min at a temperature of 480 °C, then cooled down while stirring to an eutectic point of tin zinc alloy (198.9 °C) to remove silver zinc dross. X-ray Fluorescent-1800 (XRF-1800) and Field Emission Scanning Electron Microscopy Energy Dispersive Spectroscopy (FE-SEM-EDS) analyses were performed in this research. Different factors including holding time, zinc dissolution, agitation time and agitation rate were evaluated. The results revealed that an agitation rate of 600 RPM, 25% Zn and 60 min at a temperature of 198.9 °C were efficient. Zinc silver was removed as dross every 20 min to get 92% silver separation efficiency, and the use of supergravity centrifuge is highly recommended to get best separation efficiency.

Keywords

• tin silver alloy residue
• pyrometallurgy
• silver extraction
• thermodynamics
• environmental issues
• valuable metals