Effect Of Magnetite On Bioleaching Of Chalcopyrite

As a common oxidizing ore associated with chalcopyrite,the effect of magnetite on chalcopyrite leaching has not been studied systematically.In this paper,through the leaching test of chalcopyrite and magnetite mixed ore with different mass ratios in sterile system and bacteriological system,and using X-ray diffraction,Raman spectrum and infrared spectrum detection methods,as well as electrochemical testing methods such as open-circuit potential,cyclic voltammetry curve and Tafel curve,the influence of magnetite on chalcopyrite microbial leaching was systematically studied.The reasons for the difference of chalcopyrite leaching effect and the factors affecting the dissolution of chalcopyrite were discussed,and the strengthening mechanism of magnetite on chalcopyrite microbial leaching was revealed.（1）In aseptic system,the addition of magnetite can promote chalcopyrite leaching to a certain extent.When 0.5 g magnetite was added to the system,the copper leaching rate was the highest,and the redox potential was maintained within650-750 m V（vs.NHE）,and chalcopyrite was reduced to the more oxidizing chalcocite.When the magnetite dosage was 1 g and 2 g,the redox potential was maintained within 850-900 m V（vs.NHE）,and chalcopyrite was mainly oxidized by Fe³⁺.In chalcopyrite leaching system alone,the redox potential was maintained in the range of 650-750 m V（vs.NHE）,but due to the low concentration of iron ions in the system,copper extraction was the lowest.（2）In the bacterial system,the redox potential remained above 800 m V（vs.NHE）after stabilization,and chalcopyrite was mainly oxidized by Fe³⁺.In the undomesticated Acidithiobacillus ferrooxidans system,the bacterial activity is low and the Fe²⁺oxidation ability is weak.The leaching rate of chalcopyrite increases with the addition of magnetite.After domestication,the activity of bacteria was enhanced,and Fe²⁺was rapidly oxidized to Fe³⁺.When the magnetite content is 0.5 g,the copper extraction can be increased by about 8%.When the addition amount of magnetite is greater than 0.5 g,jarosite is formed in the system,which worsens the leaching environment and affects bacterial activity.Meanwhile,jarosite covers the mineral surface,hindering the further dissolution of chalcopyrite,resulting in the copper leaching rate of the system only increasing by about 2%.Compared with the single bacterial system,the mixed bacteria further enhanced chalcopyrite leaching and improved the leaching rate of chalcopyrite,but there was still jarosite precipitation in the system.（3）The electrochemical test results showed that the galvanic interaction between chalcopyrite and magnetite was not conducive to the oxidation and dissolution of chalcopyrite in sterile and bacterial systems,but the iron ions in the system could affect the electrochemical reaction strength and corrosion current of chalcopyrite.In the bacterial system,bacterial action enhanced the electrochemical reaction of chalcopyrite and increased the corrosion current of chalcopyrite,and domestication could further promote the corrosion of chalcopyrite.