In order to decrease the solubility of PbSO4 and enhance lead recovery from PbSO4 bearing wastes, CO was employed as a reductant to transform PbSO4 into Pb S. Reaction system was established and reductive thermodynamics of PbSO4 was calculated by software HSC 5.0. The effects of gas concentration, reaction temperature, time and mass of sample on reduction of PbSO4 were examined by thermogravimetry(TG) and XRD. Roasting tests further verify the conclusions of thermodynamic and TG analyses. The results show that increasing temperature in the reasonable range and CO content are favorable for the formation of Pb S. The reduction process is controlled by chemical reaction and calculation value of the activation energy is 47.88 k J/mol.
In order to enhance the lead and zinc recovery from the refractory Pb-Zn oxide ore, a new technology was developed based on sulfidation roasting with sulphur by temperature gradient method. The solid-liquid reaction system was established and the sulfidation thermodynamics of lead and zinc carbonate was calculated with the software HSC 5.0. The effects of roasting temperature,molar ratio of sulphur to lead and zinc carbonate and reaction time in the first step roasting, and holding temperature and time in the second roasting on the sulfidation extent were studied at a laboratory-scale. The experimental results show that the sulfidation extents of lead and zinc are 96.50% and 97.29% under the optimal conditions, respectively, and the artificial galena, sphalerite and wurtzite were formed. By the novel sulfidizing process, it is expected that the sulphides can be recovered by conventional flotation technology.
Cleaning of high antimony smelting slag from an oxygen-enriched bottom-blown was tested by direct reduction in a laboratory-scale electric furnace.The effects of added CaO,mass ratio of coal(experimental)to coal(theoretical)(ω)and the slag type on the reduction procedure were considered.The contents of Sb and Au were investigated.Iron contamination of the metal phase was analyzed as this may impede the economical viability of this process.The initial slag,coal and CaO were mixed and homogenized before charging into the furnace,and the residual slag averagely contains 1.26 g.ton^-1 Au and1.17 wt% Sb.However,the iron contamination of antimony alloy becomes unacceptably high in this case as the metal phases contain up to 10 wt% Fe.In the slag system with mass ratio of SiO2:FeO:CaO= 45:27:18,the residual slag obtained after reduction under these conditions averagely contains<1 g·ton^-1 Au and<1 wt% Sb,and the metal phase contains<7 wt% Fe.The recoveries of Au in the metal phase are>98 % in all experiments which is proved to be an economic and cleaning process.
Hong-Lin LuoWei LiuWen-Qing QinYong-Xing ZhengKang Yang
The volatilization of stibnite(Sb2S3) in nitrogen from 700 to 1000 °C was investigated by using thermogravimetric analysis. The results indicate that in inert atmosphere, stibnite can be volatilized most efficiently as Sb2S3(g) at a linear rate below850 °C, with activation energy of 137.18 k J/mol, and the reaction rate constant can be expressed as k=206901exp(-16.5/T). Stibnite can be decomposed into Sb and sulfur at temperature above 850 °C in a nitrogen atmosphere. However, in the presence of oxygen,stibnite is oxidized into Sb and SO2 gas at high temperature. Otherwise, Sb is oxidized quickly into antimony oxides such as Sb2O3 and Sb O2, while Sb2O3 can be volatilized efficiently at high temperature.
