Mechanism Research On Tellurium Recovery From Soda Slag Produced From Lead Anode Slime

Nowadays, the lead anode slime is still treated by pyrometallurgy method mainly, and thus, most tellurium, bismuth, copper and other valuable metals in lead anode slime are concentrated in soda slag during treating process. How to recover these valuable metals comprehensively from soda slag has been concerned by metallurgical industries and researchers. However, some shortages such as long flow and low comprehensive recovery still exist for current treating methods. Therefore, it’s significant to research the mechanism of recovering valuable metals from soda slag from the view of theory and application.Based on the results of previous, a method and technology was proposed to leach simultaneously tellurium, bismuth, copper and other valuable metals according to their phase characteristics in soda slag. Subsequently, the thermodynamics and kinetics of reducing tellurium from leach solution were studied, and also, the reduction technologic parameters were explored. The main results of this research are listed as follows:Thermodynamic calculation of leaching valuable metals from soda slag were carried out based on their existing form in slag. Results show that tellurium, bismuth and copper can be leached simultaneously by hydrochloric acid under a certain temperature and acidity.Results of leaching experiment show that Two-Stage leaching technology is feasible to leach simultaneously tellurium, bismuth and copper from soda slag and is effective to avoid low metal density and large treatment volume of leaching solution. The leaching rate of tellurium, bismuth and copper are more than97%under the condition:hydrochloric acid density5.0mol/L, reaction temperature40℃reaction time2hours, ratio of leaching liquid to solid of the first stage4:1, and ratio of leaching liquid to solid of the second stage8:1.The electric potential equations of reducing complex ions in leaching solution were deduced according to the complex reaction between metal ions and chloride ion. The electric potential equation of tellurium complex ion is as follow: ETeCl62/Te=0.63+0.00641n[TeCl62]-0.03851n[Cl-]The mechanism of adding reductant was explored by thermodynamic analyzing the tellurium reducing process with sodium sulfite as reductant. Then, a Small-Amount and Many-Time adding method was proposed. Experiment results verify that this method is useful to control the reducing electric potential and can be used successfully to reduce tellurium from multi-metal leach solution and produce elementary tellurium.The kinetic research results show that the tellurium reducing reaction by sodium sulfiteis second-order reaction with an activation energy value of50.00kJ/mol under the condition:reaction temperature25~55℃, initial acidity3~6mol/L, ration of reductant practicalconsumption to theoretical consumption0.5~2, and initial tellurium density0.15~0.45mol/L.Results of this research will provide theoretical support for the industrial application andtechnological innovation of recovering valuable metals from soda slag.