Study Of Combined Chemical Leachin And Bioleaching Process On Secondary Copper Sulfide Concentrate

At present, the pyrometallurgical processes still account for a large proportion in copper extraction of bornite and chalcocite and other secondary copper sulfide copper concentrate in China. The process suffers from lower resource utilization and higher energy requirement, and it is difficult to reach the level of conventional slag type, and it also has the disadvantage of producing SO2gas, which can cause serious environmental pollution. Bioleaching process of copper has the advantage of lower cost and lower power consumption, but the bioleaching method has a trouble of long leaching period as well as slow leaching velocity.In view of these problems, a new combination process of chemical leaching and biological leaching was innovatively proposed. The new method was carried out in this way:leaching bacteria was inoculated in early bioleaching while an appropriate amount of ferric sulfate was added into the system at the same time, and in this way, ferric sulfate can be regenerated in a steady stream as strong oxidants, which supplement Fe3+that consumed by the individual chemical leaching, and it can also make up the deficiencies that the existence of an uncertain lag in single biological process.The mineralogical research was carried on the secondary copper sulfide concentrate. The results showed that the copper was mainly formed as secondary copper sulfide, such as chalcocite, bornite and minor malachite and others, which shared87.15%, and the copper grade was21.56%.Acid leaching of the copper concentrate was analyzed at first; secondly, separate experiments (chemical leaching and bioleaching) were investigated separately on the acid leaching residue; finally, the acid leaching residue was researched in combined chemical leaching and bioleaching process, and through which the optimal processing conditions were investigated.(1) The results indicated that the optimal conditions of a particle size of-180mesh, pulp density of20%, agitation leaching60min～90min in acid leaching process, whose copper leaching rate was17.13%.(2) Separate chemical leaching experiments was carried on when a certain concentration of Fe3+was added into the system of secondary copper sulfide concentrate, and the copper leaching rate of chemical leaching was53.82%after48hours, and the total copper leaching rate was about60%after eight days.(3) Under optimal conditions of the Fe2+of9g/L, pulp density of10%, temperature of30℃, inoculum amount of10%, particle size of-180mesh in alone bioleaching, whose copper leaching rate was just about40%, taking the copper leaching rate of acid leaching (17.13%)into account, the total copper leaching rate of bioleaching was less than60%after8days.(4) Using the combined chemical leaching and bioleaching process, the total copper leaching rate of the combined process can be as high as84.36%, which was41.92%higher than the individual biological leaching, and was27.31%higher than the individual chemical leaching after eight days.The combined chemical leaching and bioleaching process can indeed improve leaching efficiency of the secondary copper sulfide copper concentrate, and was significantly better than the individual chemical leaching and individual bioleaching process. It can shorten the leaching period and was an environmentally-friendly new method. It was found that combined chemical leaching and bioleaching process can open a new way for hydrometallurgical process of the secondary copper sulfide.