Phase Evolution of Silver in Lead-Silver Slag During Melting-Fuming Process
The phase evolution of silver in lead-silver slag during melting-fuming process was studied.The thermodynamic mechanism of silver phase volatilization in lead-silver slag was analyzed by thermody-namic calculation and analysis.Based on the thermodynamic theory calculation,the influence of single factor(reaction temperature,carbon proportion and holding time)on silver recovery rate was studied,and the optimum process parameters were obtained.Then,by observing the microstructure morphology,combined with theoretical calculation and experimental results,the evolution law of silver phase in lead-silver slag during melting-fuming process was clarified.The thermodynamic analysis results show that Ag2 O in the lead-silver slag is preferentially volatilized into the soot.AgCl in the slag does not undergo oxida-tion reaction,reduction reaction and decomposition reaction,and will volatilize into the dust.Ag2S in lead-silver slag does not volatilize or undergo reduction reaction,and will be oxidized to Ag2SO4.At low temperature,Ag2SO4 will be reduced to elemental silver,and elemental silver will form an alloy with lead and zinc,which will be carried into the soot.At high temperatures,the vapor pressure of Ag2SO4 increa-ses sharply and Ag2SO4 volatilizes into the dust.The experimental results of silver slag show that the pha-ses in the dust are Ag2O,AgCl,Ag2SO4 and elemental silver,which is consistent with the results of ther-modynamic analysis.The single factor experiment showed that the optimum process parameters for silver recovery from lead-silver slag were reaction temperature of 1 300 ℃,carbon proportion of 16.30％,hold-ing time of 150 min.Under these conditions,the silver recovery rate was 80.26％.
lead silver slagmelting-fumingsilver phasethermomechanical anaysissingle factor
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