Study On Treatment Of Heavy Metals Pollution Of Copper Tailings By Air-lift Bio-reactor

In this dissertation, the copper mine tailings taken from Yangla Mine Copper inYunnan was taken as research objective and Acidthiobacillus ferrooxidans was used asthe experimental bacteria. The surface microstructure and component of tailings wereexamined by SEM and ICP-OES technology, then Dold sequential extraction procedure,which was a good way to evaluate the leachable component in the tailings, was adoptedto analyze the speciation of heavy metals contained in the tailings. Finally we conductedthe bioleaching experiment of tailing in the air-lift reactor and attempted to research theleaching velocity and concentration of heavy metals through changing the pulp density,the initially pH value in the leaching system and the inoculum amount of leachingbacteria respectively. After the experiment, the mechanism of bioleaching was discussed,aiming to add some knowledge to the theoretical basis of bioleaching with At.f.The SEM pictures showed that the tailings surface was characteristic of some flawsand also some flocculent substance could be seen on the surface. The results ofICP-OES indicated that the major elements contained in tailings were Si, Al, Ca, Fe, S,and the components were250.35mg/g,82.1786mg/g,71.6768mg/g,141.931mg/g,66.6592mg/g respectively. While other elements like Cu, Zn, Cd, As, which posed asevere threaten on human health, had a relatively low components of3.4906mg/g,1.3706mg/g,0.064mg/g,1.2221mg/g.The results of Dold sequential extraction procedure suggested that the mainspeciations of Cu were exchangeable fraction, secondary Cu-sulfides, primary sulfidesand residual, and their own proportions were13.8%,24.9%,16.7%,42.6%. Theexchangeable fraction of Cd made up6.9%of the total, and the proportions of primarysulfides and residual of Cd were19.4%and69.4%. the exchangeable fraction, Fe(Ⅲ)oxyhydroxides, secondary sulfides, primary sulfides and residual of Zn accounted for4.5%,4.0%,13.1%,48.3%,39.3%respectively. While the maion speciations of As wereprimary sulfides (20.2%) and residual (78.7%).The bioleaching results revealed that the pulp density, initial pH value in theleaching system and inoculum amount of leaching bacteria played important roles inleaching heavy metals from tailings. The best leaching conditions for Cu are at thetemperature of25℃, pulp density of10%(w/v), initial pH value at1.6, and the leachingconcentration of copper reaches54.1mg/L (leaching rate16.58%) after24days. While the best leaching conditions for Cd, Zn and As are at the temperature of25℃, pulpdensity of10%(w/v), initial pH value at1.2and the leaching concentrations of Cd, Znand As are1.05mg/L,103.89mg/L,54.04mg/L, with leaching rates of Cd(17.51%),Zn(81.10%), As(47.32%), respectively after24days.