Bioleaching of two different genetic types of chalcopyrite and their comparative mineralogical assessment

The use of biochar for controlling acid mine drainage through the inhibition of chalcopyrite biodissolution

Although chalcopyrite biodissolution plays an important role in the formation of acid mine drainage (AMD), the control of AMD through inhibiting the biodissolution of chalcopyrite has not been studied until now. In order to fill this knowledge gap, a novel method for inhibiting chalcopyrite biodissolution using biochar was proposed and verified. The effects of biochar pyrolysis temperature and biochar concentration on the inhibition of chalcopyrite biodissolution in the presence of Acidithiobacillus ferrooxidans (A. ferrooxidans) were studied. The results indicate that biochar significantly inhibited chalcopyrite biodissolution, thus reducing the number of copper and iron ions and quantity of acid released. In turn, this suggests that AMD generation was suppressed under these conditions. Biochar pyrolyzed at 300 °C (Biochar-300 °C) was the most effective at inhibiting chalcopyrite biodissolution and reduced its biodissolution rate by 17.7%. A suitable concentration of biochar-300 °C enhanced its inhibition of chalcopyrite biodissolution. The optimal concentration of biochar-300 °C for inhibiting chalcopyrite biodissolution was 3 g/L. Biodissolution results, cyclic voltammetry, mineral surface morphology, mineralogical phase, and elemental composition analyses reveal that biochar inhibited the biodissolution of chalcopyrite by promoting the formation of passivation layer (jarosite and S_n^2-/S⁰) and adsorbing bacteria.

Catalytic effect of silver on copper release from chalcopyrite mediated by Acidithiobacillus ferrooxidans

Although silver ion in the solution is an important factor affecting the biodissolution of chalcopyrite, the effect of silver ion on the release of copper ion from chalcopyrite to the environment has not been explored until now. In order to fill this knowledge gap, the effect of silver ion on copper release from chalcopyrite in the presence of Acidithiobacillus ferrooxidans was investigated. The results indicate that silver ion significantly enhanced chalcopyrite biodissolution, thereby releasing more copper ion. In turn, this indicates that the release of copper ion from chalcopyrite to the environment was increased under these conditions. Biodissolution results, bacterial adsorption experiments, elemental composition analysis, and electrochemical analysis reveal that the enhancement of silver ion on copper ion release from chalcopyrite was mainly attributed to the improvement of electrochemical activity of chalcopyrite and the inhibition of the formation of passivation layer (S_n^2-/S⁰) on the chalcopyrite surface. This study provides a better understanding of the effect of silver ion on the release of copper ion from chalcopyrite to the environment. In the future, the influence of silver ion on chalcopyrite biodissolution should be considered in the evaluation of copper ion pollution to ensure reliability.

Combined effects of jarosite and visible light on chalcopyrite dissolution mediated by Acidithiobacillus ferrooxidans

Although jarosite and visible light are important factors for the formation of acid mine drainage (AMD), the effects of combined jarosite and visible light on chalcopyrite biodissolution have not been explored until now. In order to fill this knowledge gap, the combined effects of jarosite and visible light on chalcopyrite dissolution mediated by Acidithiobacillus ferrooxidans were investigated. The results indicated that jarosite and visible light could significantly accelerate chalcopyrite biodissolution, thus releasing more copper ions, iron ions and producing more acid. This in turn suggests enhanced generation of AMD under these conditions. Biodissolution results, mineral surface morphology, mineralogical phase and elemental composition analyses revealed that the promotion of chalcopyrite dissolution by additional jarosite and visible light was mainly attributed to the acceleration of ferric iron/ferrous iron cycling and the inhibition of the formation of a passivation layer (jarosite and S_n^2-/S⁰) on the surface of chalcopyrite. This study provides a better understanding of the effects of jarosite and visible light on chalcopyrite biodissolution. In the future, the influences of jarosite and visible light on chalcopyrite dissolution should be considered in AMD evaluation to ensure reliability.

Chalcopyrite bioleaching of an in situ leaching system by introducing different functional oxidizers

Introducing exogenous species to an indigenous microbial community is an effective way to reveal the connections between metabolic processes, ecological function and microbial community structure. Herein, three different functional consortia (ferrous oxidizers, sulfur oxidizers and ferrous/sulfur oxidizers) were added to a natural leaching solution system derived from Zijin copper mine, China. The leaching experiment showed that the copper extraction rate of the community invaded by a sulfur-oxidizing consortium was 50.40% higher than that of the indigenous leachate at the endpoint of bioleaching. The variations of ferrous content, total iron, pH and redox potential in leachates also provided evidence that the community with exogenous sulfur oxidizers was more efficient. XRD analysis demonstrated that a proper addition of the sulfur-oxidizing consortium could eliminate sulfur passivation, promote production of chalcocite and enhance leaching. Furthermore, an exogenous ferrous-oxidizing consortium and a sulfur-oxidizing consortium greatly changed the community structure and microbial succession and promoted the cell growth rate during the bioleaching process, while ferrous/sulfur oxidizers showed no obvious effects on the indigenous community. Exogenous ferrous oxidizers, mainly L. ferriphilum, and sulfur oxidizers, mainly A. thiooxidans, successfully established and colonized in the indigenous community. However, only colonized A. thiooxidans, rather than L. ferriphilum, showed advantageous enhancement in the dissolution of chalcopyrite. Results indicated that exogenous sulfur oxidizer A. thiooxidans, which was scarce in the indigenous community, could easily colonize in the indigenous community, significantly change the community structure, sufficiently execute its function, and greatly enhance copper dissolution.

Introducing different functional consortia into a native system revealed that complementary sulfur invaders greatly enhanced the community function.