| Gacun Cu-Pb-Zn polymetallic sulfide ore is rich in tetrahedrite, and productive practice has shown that its flotation separation is very difficult. In order to improve the comprehensive recovery of this kind of resource, the studies of process mineralogy and density functional theory were done first to understand the ore property in this thesis. The research result of the process mineralogy showed that mineral liberation of the ore is difficult because its minerals inlay closely each other and furthermore their particle sizes are so fine. And the research result of the density functional theory showed that the flotation separation between tetrahedrite, which is the primary Cu mineral in Gacun mine, and galena is more difficult than the separation between chalcopyrite and galena, and the floatability of impure tetrahedrite bearing iron is especially close to galena. It is thus clear that the flotation separation indexes of this tetrahedrite type Cu-Pb-Zn sulfide ore will be unsatisfactory if only routine flotation reagents and conventional processes such as differential flotation or partial bulk flotation are applied, so that the studies of new collectors, new flotation process and even beneficiation-metallurgy combination process are necessary.Afterward, the screening experiments of Cu collectors and Lead collectors with the Gacun raw ore were done, and experiment results showed that both of collecting capabilities and selectivities of the two new-type collectors named EICTU (N-ethyl-N’-isopropoxycarbonyl thiourea) and BITCM (S-benzyl-N-ethoxycarbonyl dithiocarbamate) are respectively optimal for Cu and Pb. It was confirmed by the comparison of collectors’complexations with metal ions, collection performances with pure natural minerals and adsorption behaviors on the surfaces of the pure minerals that the selectivities of EICUT for copper and BITCM for lead are both superior to routine collectors, and furthermore the collecting capabilities of the two new-type collectors are also excellent. And then the researches of structure-activity relationships of collectors and the microscopic mechanisms on atomic level how EICTU and BITCM absorb on mineral surfaces were done with density functional method. On the aspect of structure-activity relationship, the analysises of bond lengths of carbonyl S atoms and Mulliken populations of collector molecules and the energy matching of frontier molecular orbitals between collector molecules and mineral crystals have been done, and the results showed again that both of selectivities and collecting capabilities of EICUT and BITCM are separately excellent for Cu and Pb. On the aspect of adsorption mechanism, the adsorptions of EICTU and BITCM molecules on mineral crystal surfaces were simulated, and the research results showed that when an EICTU molecule adsorbs on the surface of tetrahedrite or chalcopyrite or when a BITCM molecule adsorbs on galena surface, carbonyl S and carbonyl O of the collector react with corresponding Cu atoms or Pb atoms and yield respectively normal covalent bonding and back donating bonding and furthermore normal covalent bonding take leading role, and the effects of Zn, As, Ag impurities in tetrahedrite surface on EICTU’s adsorption are negligible but Fe impurity is obvious disadvantage for the adsorption.Three kinds of flotation processes were studied contrastively with Gacun Cu-Pb-Zn polymetallic sulfide ore, and the result showed that differential flotation is beneficial to decrease dirtpercentages of concentrate products whilst partial bulk flotation is helpful to recover silver, and the performaces of the both two prossces were improved distinctly after their combination with EICTU and BITCM, while the new process, Cu-Pb iso-flotation emphasizing on Cu, is able to decrease dirtpercentages of concentrates and increase the Ag recovery simultaneously. The iso-flotation combined with EICTU and BITCM is able to improve furthest the flotation comprehensive recovery of Gacun polymetallic sulfide ore. The percent recoveries of Cu, Pb, Zn and Ag were respectively77.82%,71.83%,84.42%and79.11%in the closed-circuit test of this new process combined with the two new-type collectors, and the recoveries of these metals were raised separately5.79%,7.91%,1.06%and8.34%than the result of the closed-circuit test whose reagent regime and process flow were exactly the same as Gacun dressing plant. But the flotation separation indexes of Cu-Pb bulk concentrate of iso-flotation were still unsatisfactory, so that it is necessary that the flotation is substituted by certain a befitting metallurgical method for a more thorough separation of the bulk concentrate.The experimental investigation of two stage oxygen pressure acid leaching of iso-flotation Cu-Pb bulk concentrate showed that the extraction ratios of Cu and Zn were as high as96.30%and97.37%, while the extraction ratios of impurities such as Fe, As and Sb were as low as15.23%,6.20%and0.50%, and furthermore Pb and Ag weren’t extracted basically, so Cu and Zn can be separated with Pb and Ag relatively thoroughly by this process. The comprehensive recoveries of Cu, Pb, Zn and Ag of the iso-flotation-oxygen pressure acid leaching process were respectively as high as82.94%,80.05%,90.40%and79.11%, and the recoveries of Cu, Pb and Zn were raised separately5.12%,8.22%and5.98%whilst Ag recovery stayed the same compared with the single iso-flotation. The benefication-metallurgy combination new process combining iso-flotation and oxygen pressure acid leaching was recommended in the end for the tetrahedrite type Cu-Pb-Zn polymetallic sulfide ore, because that the comprehensive recoveries of this process are high whilst its metallurgical scale is small and process flow is short. |
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