New Process For Production Of Antimony By Directly Smelting In Low Temperature Molten Salt Of Na₂CO₃-NaCl From Gold-antimony Concentrate

A new process to extracted antimony from gold-antimony concentrate by molten salt smelting at low temperature was presented in this paper to avoided the shortcomings of the traditional pyrometallurgical process, which included high smelting temperature, high energy and material consumption,high production cost and severe environmental pollution.In the process, the crude antimony was produced one step at the temperature of700℃-900℃in the smelting system of soda and sodium chloride, and crude antimony can enrich valuable metals.While added sulfur agent ZnO to fixed sulfur dioxide, Most of the molten salt back to melting process directly after separated, Na2CO3which participate react partially can be recovered by hydro-process, ZnS generated in smelting process can sale or return to smelting process when roasted after ore dressing.The thermodynamic analysis of antimony sulfide smelting process in low temperature molten salt was calculated. The calculation results show that the reaction of antimony sulfide and ZnO in the condition of carbon reduction can be spontaneous carry, antimony sulfide will also react with Na2CO3and generated Na2S, But Na2S will be regenerated by ZnO soon.These reactions have large thermodynamic trend; The thermodynamic of mechanism of melting process was calculated, By comparing the△Gθ of each possible approaches, we found that the process of Sb2S3occurs desulfurization reaction with ZnO and generate the Sb2O3firstly, then reduced to the metal antimony was the most impossible mechanism.The thermodynamic analysis of the behavior of MgCO3、FeS2、 CaCO3、SiO2and Al2O3which are the main gangue in antimony sulfide concentrate in smelting process was calculated. The calculation results show that all the silicon generated solubility Na2SiO3, MgCO3decomposd and didn’t reacet with Na2CO3. CaCO3、FeS2and Al2O3occur partially reaction and consumed part of the molten Na2CO3. Smelting experiments need to keep additional Na2CO3. The calculation results also show that AgS、PbS、Cu2S、As2O3charged to Ag, Pb, Cu and As in the molten salt smelting medium. FeS2and ZnS directly entered into slag without any reaction occured.Antimony sulfide ore form chenzhou mining group was used for low-temperature molten salt smelting test.Effects of molten salt composition, smelting temperature, reaction time, salt amount, and ZnO addition on the molten salt smelting of stibnite concentrate have been investigated in detail. The optimum conditions was determined as follows: WNa2CO3/WNaCl=0.55:0.45、temperature850℃、time1h、Wmolen salt/Wsolids=5:1、Wzno/Wtheory=1.0、4times theoretical coal powder.Under above-mentioned optimum conditions, the average direct recovery ratio of antimony is81.93%, and the average grade of crude antimony is85.58%.The behavior of major gangue are investigated by XRD analysis and DSC-TGA thermal analysis techniques on the basis of thermodynamic calculations when separation antimony from stibnite concentrate through a low temperature smelting. The result shows that their behavior and thermodynamic analysis consistent and only the CaCO3react partially.The new process has advantage of sharp decrease of smelting temperature, reducing the energy consumption and improve the operating environment.The melting process does not produced smoke, and eliminating the environmental pollution of low concentration SO2.It has a great significance to the technology of antimony smelting improvement.