The Bioleaching Of Low Grade Copper Sulphide Ore

The bacteria used in this paper were isolated from the acid mine drainage waste in Da Baoshan and Yu Shui Mine, marked as DB and YS, respectively, and the pure Acidithiobacillus ferrooxidans.The effect of many factors, such as temperature, pH, concentration of copper ion, on the bacterial growth and oxidation activity of ferrous ion and sulphur were investigated. Then the bioleaching of chalcopyrite as well as that of sulphide copper ore were carried out in the Erlenmeyer flask in order to research the interaction of the factors which have an effect on the bioleaching of chalcopyrite and copper sulphide ore. In the Bioleaching Controlling System the column bioleaching of the copper sulphide whole ore was carried out and the effects of several variables on copper recovery in column bioleaching have been analysed. The impacting mechanism of various variables in the bioleaching process was studied, using the electrochemical analysis methods, SEM, X-Ray diffraction and Energy Dispersive X-ray Analysis (EDXA).The bacteria growth and the growth and oxidation activity of ferrous ion and sulphur were investigated.It was indicated that the bacteria grew best when the temperature was 30±1℃, the pH value was 2.0 and the concentration of copper ion was below 0.015mol/L.On this condition the bacteria oxidation activity of ferrous ion and sulphur were highest, which was intensively inhibited while on the no best condition.The experiment results showed that the mixed bacteria oxidation activity of sulphur was better than that of the pure Acidithiobacillus ferrooxidans.The bioleaching of chalcopyrite were conducted to research the bioleaching behaviors of chalcopyrite. The experiment result showed that the dissolution of chalcopyrite was accelerated in the presence of bacteria. The copper extraction yield was 46.27% for 75 days of bioleaching, in which theâ–³G_298.15⁹ of chalcopyrite dissolution reaction was -5623.80 kJ·moL^-1, while those of acid leaching being 11.5%,121.53kJ·mol^-1 respectively for the same duration. It was found that the copper dissolution was affected by the inoculum size, pulp density, pH value and redox potential. The bioleaching rates reached their highest point in chalcopyrite with a pulp density of 5% and pH value of 2. Inoculum size had no effect on the final copper extraction. In bioleaching the rodex potential was mainly determined by the rate of ferric iron concentration to ferrous iron concentration, and the redox potential was in the range of 506 mv～518mv, in which chalcopyrite could dissolved at high rate. The atom ration of chalcopyrite before and after bioleaching showed that the element sulphur and iron precipitation was found on the surface, forming sulphur film and iron deposition such jarosite which hindered the dissolution of chalcopyrite, but the rate of chalcopyrite dissolution keep at a high level by the mixed bacteria with the effective oxidation of element sulphur due to the better sulphur oxidation activity and low pH value.The bioleaching of sulphide copper ore were carried out in Erlenmeyer flask and column. The column bioleaching of copper sulfide ore was carried out in the Bioleaching Controlling System. It was studied that the interaction of several factors by the experiment in the Erlenmeyer flask. The results of column experiment showed that the sulphide copper ore could dissolve effectively, and the copper extraction yield was greater in presence of mixed bacteria than that with Acidithiobacillus ferrooxidans. The whole bioleaching process coule be divided into two steps, in the first step the dissolution rate of chalcopyrite was quiker than that in the second step. It was found thait particle size and liquid irrigation flow rates have an effect on the dissolution. The leaching rates of chalcopyrite tend to increase with the low liquid irrigation flow rate and the suitable particle size. Furthermore, the redox potential of the solution tended to be higher as well as the leaching rate of chalcopyrite tended to increase with dissolved ferric ion concentration at lower pH ranges, In the inoculated column, jarosite and elemental sulfur were formed.Results show that the maximum zinc recovery was achieved on the conditong of particle size rage was -10+5m and liquid irrigation flow rate was 3ml/cm²Â·h. Zinc dissolution reached 43.64%for DB mixed bacteria, after 80 days.The dissolution behavior of chalcopyrite was determined by the crystal structure. The semiconductor electrochemical investigate demonstrated that in initial chalcopyrite was oxidized by the transfer of holes between semiconductor and solution surface, then company with the electron transfer. The dissolution rate of chalcopyrite tend to increase with the holes transport velocity.In presence of bacteria, the corrosion current was higher than that in bacteria being absent.