Catalytic mechanism of manganese ions and visible light on chalcopyrite bioleaching in the presence of Acidithiobacillus ferrooxidans

The bioleaching of chalcopyrite is low cost and environmentally friendly,but the leaching rate is low.To explore the mechanism of chalcopyrite bioleaching and improve its leaching rate,the effect and mechanism of manganese ions(Mn^(2+))and visible light on chalcopyrite mediated by Acidithiobacillus ferrooxidans(A.ferrooxidans)were discussed.Bioleaching experiments showed that when both Mn^(2+)and visible light were present,the copper extraction was 14.38%higher than that of the control system(without Mn^(2+)and visible light).Moreover,visible light and Mn^(2+)promoted the growth of A.ferrooxidans.Scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS)analysis revealed that Mn^(2+)promoted the formation of extracellular polymeric substance(EPS)on the surface of chalcopyrite,changed the morphology of A.ferrooxidans,enhanced the adsorption of bacteria on chalcopyrite surface with light illumination,and thus promoted the bioleaching of chalcopyrite.UV–vis absorbance spectra indicated that Mn^(2+)promoted the response of chalcopyrite to visible light and enhanced the catalytic effect of visible light on chalcopyrite bioleaching.Based on X-ray photoelectron spectroscopy(XPS),the relevant sulfur speciation of chalcopyrite before and after bioleaching were analyzed and the results revealed that visible light and Mn^(2+)promoted chalcopyrite bioleaching by reducing the formation of passivation layer(S_(n)^(2-)/S0).Investigation into electrochemical results further indicated that Mn^(2+)and visible light improved the electrochemical activity of chalcopyrite,thus increasing the bioleaching rate.

Double perovskite anti-supported rare earth oxide catalyst CeO_(2)/La_(2)CoFeO_(6)for efficient ventilation air methane combustion

Ventilation air methane is one of available resources with a massive reserve.However,most of ventilation air methane is discharged into the air and pollutes the environment.Catalysts with high temperature resistance(>800℃)for ventilation air methane are very essential for utilization of the ventilation air methane.We mainly prepared catalysts CeO_(2)/La_(2)CoFeO_(6)and La_(2)CoFeO_(6)/CeO_(2)and comparative samples CeO_(2)and La_(2)CoFeO_(6)by the simple sol-gel method and calcined them under 9000C,and tested the catalytic performance of ventilation air methane combustion under the condition of 5 vol%H_(2)O.The experimental results show that the light-off temperature(T_(1O))and complete combustion temperature(T_(90))of the ventilation air methane combustion reaction of CeO_(2)/La_(2)CoFeO_(6)catalyst are 417.4 and 587.7℃,respectively.T_(1O)and Tgo of La_(2)CoFeO_(6)/CeO_(2)only reach 425.5 and 615.8℃.The T_(10)and T_(9O)of CeO_(2)/La_(2)CoFeO_(6)are 417.4 and 587.7℃,which are lower than those of La_(2)CoFeO_(6)[T_(10)=452.4℃and T_(90)=673.0℃)and La_(2)CoFeO_(6)/CeO_(2)(T_(10)=425.5℃and T_(90)=615.8℃).Therefore,the catalytic performance of the anti-supported rare earth oxide catalyst CeO_(2)/La_(2)CoFeO_(6)is better than that of La_(2)CoFeO_(6)and supported catalyst La_(2)CoFeO_(6)/CeO_(2).