|
The bioleaching copper technology is an economical effective method for treating low grade and difficult recovery copper ores, which has a broad application prospect. But the iron content of copper bioleaching solution is higher, which has an side effect on the solvent extraction of copper.Copper sulfate pentahydrate was prepared from copper bioleaching solution by sulfide precipitation, hydrogen peroxide leaching and evaporative concentration process, and the elemental sulfur was recovered from slags by hot melting method. Futhermore, the iron of the solution after recovering copper was removed by oxidizing sedimentation method and sodium jarosite method and the wastewater was recycled.Compared with Na2S method, treating copper bioleaching solution by H2S method needs less agent, and no Fe(OH)3 gels are formed.The precipitation rate of Cu was 100% and the reduction of Fe3+ was 91% by H2S treatment when the molar ratio of H2S:Cu was 1.9:1, the solution pH value was 1, the reaction temperature was 30℃, and the reaction time was 3h. The main phase of sediments were both CuS and S, of which the Cu content was 45%.Copper sulfide sediment was leached by hydrogen peroxide and sulphuric acid. The copper leaching rate was 92.1% under the conditions of molar ratio of hydrogen peroxide with copper, reaction temperature, liquid-solid ratio, concentration of sulfuric acid, and reaction time were set to be 6.4:1,50℃,15:1,3mol·L-1 and 2h, respectively. CuSO4·5H2O was obtained by evaporative cooling crystallization process when the volume of solution after evaporation and concentration was 1/2 of the stock solution under the cooling temperature of 6℃. The purity of obtained CuSO4·5H2O was 96%, and its quality satisfies the standard of industrial copper sulfate (GB437-93). Elementary sulfur was recovered from sulfur sediment by hot melting when the screen diameter was 38μm and the filtration temperature was 145℃. The purity of obtained elementary sulfur was 99.93% and its quality meets the standard of industrial sulfur standard (GB/T2449-2006).Fe was removed from copper bioleaching solution by oxidizing sedimentation. When the reaction pH was 10, the air flow was 0.1m3h-1, the reaction time was 2.5h, and the reaction temperature was 25℃, the removal rate of Fe was nearly 100% and the remove rate of Mg and Al were 99.8% and 99.7% respectively, and the iron content of the precipitate was 42.5%. While Fe was removed by sodium jarosite method, the iron removal rate was 99.2% under the optimum conditions that the dosage of sodium sulfate was twice of stoicheiometric value, the reaction pH was 2.0, the reaction time was 2h and the reaction temperature was 95℃. Comparing oxidizing sedimentation method with sodium jarosite method, the product of later has a easier filtration, and its lower reation pH needs lower alkali consumption and benefits wastewater recycling.
|