Study On The Bioleaching Of High Arsenic-bearing Copper Sulfide Ore

With the development of national economy, the demand for copper is increasing. But theore grade of copper mining has been declining. According to statistics, the ore grade of mostcopper mine is below1%. The copper ore with ore grade above3%only exists in a fewcountries, such as Chile. Therefore, the cost of smelting copper by the traditionalmetallurgical process is increasing. With the in-depth studies on the treatment of low gradeand refractory ores，bioleaching is proved to be a new technology that can effectively leachvaluable metals, protect the environment, and reuse the wastes. In this study, the higharsenic-bearing copper sulfide ore （HACSO） was leached by Acidithiobacillus ferrooxidans.The leaching microbial population structure was studied. The leaching mechanism ofHACSO was determined and the optimum leaching conditions were investigated.The mixed leaching bacteria were screened from acidic mud samples collected fromthe Dabaoshan, Shaoguan, Guangdong Province. After enrichment and domestication, thebacteria were proper for ore leaching. The leaching bacteria were analyzed by thePCR-DGGE and we found that the leaching bacterial composite consisted of the threeAcidithiobacillus ferrooxidans strains. The three strains were named as DBS-3, DBS-4andDBS-6, respectively. Their accession numbers in the GenBank nucleotide database are DBS-3（JN866828）, DBS-4（JN866829） and DBS-6（JN866831）.The leaching mechanism of HACSO is crucial to provide bases for determining andoptimizing bioleaching effect factors, it is useful to increase copper extraction rate. In thispaper, we observed the surface change of the ore and the adsorption of Acidithiobacillusferrorxidans on the surface of ores. The change of iron ion concentration in the copperextraction during a13-day leacing process was also investigated. We found that the maininteractive mechanism in the bioleaching of HACSO was an indirect mechanism.The effects of a number of factors, including nutrients, solution pH, initial Fe²⁺concentration and two-stage leaching process, on the leaching rate of HACSO were studied.We found that the inorganic nutrients contained in HACSO could meet the need of theleaching bacteria. The pH range of1.8².2was favorable for leaching bacteria. Because theleaching process consumes acid, a timely adjustment of the leaching solution pH is a must. The ideal Fe²⁺concentration was6g/L. Excessive amount of Fe²⁺would generate ironvanadium and increase the cost. The low amount of Fe²⁺would result in a lower copperrecovery. Two-stage leaching process reduced the leaching time. When the initialconcentration of Fe3+was6.01g/L, the leaching time can be shortened by4days. Higherconcentrations of Fe3+resulted in a shorter leaching time. The addition of Fe3+can saveoperating costs and improve copper recovery to some extent.