Study On The Bioleaching Mechanism And Biodiversity Of Sulfide Ore

With the rapid development of world economy and the populationcontinued to climb, the demand for metal mineral resources is alsoincreasing, the high grade ore, easy processing has exhausted, low gradeand difficult process is the main ore mineral resourcesavailable.Traditional ways of metallurgical processing of low grade oreexist pollution, high energy consumption. Use of microbial oxidation indissolution of valuable metals, in the ore biological metallurgytechnology, have many advantages, such us environmental friendly, shortprocess, low cost. But its existence oxidation rate is slow, shortcomingsand so on bacteria vulnerable to environmental impact.Therefore,improve the efficiency of bacterial oxidation of ore, promoting theefficient recovery of valuable metals is the hotspot of hydrometallurgyfields need to be solved problem.Bacterial used in this experiment was enriched in acid mine drainage ofDexing copper mine, Jiangxi Province, China. The gold ore sample wassampled from Axi gold ore by Changchun Gold Research Institute, and the massive chalcopyrite was bought. A9K medium with iron free?pH=1.5?was used. In experiment a mount of homocysteine was addedinto medium.Therefore, it is necessary and significant to investigate howhomocysteine interacts with mineral. Fourier transform infraredspectroscopy (FTIR), X-ray diffraction (XRD), scanning electronmicroscope and Energy-dispersive X-ray spectroscopy (SEM-EDS) wereemployed to provide detailed insight into the interaction mechanism.Inaddition, biodiversity of the bacteria involved in bioleaching wasexamined by Miseq High throughput sequencing.Electrochemical methods (Tafel, EIS and cyclic voltammetrycharacterization) were used to characterize the dissolution of massivechalcopyrite electrodes during bioleaching. The effects of homocysteinein chalcopyrite bioleaching were further evaluated.During bioleaching,the surface of the chalcopyrite electrode was observed by Microscope. Inthe end, rhodamine B fluorescent probes was designed and synthesizedfor the detection of Fe3+.Adding a small amount of the homocysteine to bioleaching solution incontact with gold ores, largely enhanced the leaching rate of Fe, whilecysteine inhibited the extraction of As. XRD, SEM/EDS observationsshowed bioleaching products were mainly jarosite and sulfur.Furthermore, FTIR led to the conclusion that cysteine has adsorbed onmineral powder surfaces. Combining the results of the bioleaching experiment and the analysis of SEM/EDS, FTIR and XRD leads us toconclude that homocysteine addition just facilitated the electron transferbut did not change the gold ore oxidation mechanism.Bioleaching of chalcopyrite by a moderate thermophiles dominatedculture was studied. And, the effect of homocysteine on bio-oxidationkinetics of chalcopyrite was studied by Tafel curves, electrochemicalimpedance spectroscopy (EIS) and cyclic voltametry ?CV?test. BothTafel curves and EIS showed adding homocysteine just improvedperformance of bioleaching and did not change the controlled step ofbioleaching. In addition? the electrochemical response of massivechalcopyrite electrodes bioleached in10-3M homocysteine for variousperiods up to10days was studied using CV tests. The results showed thatas bioleaching proceeded, anodic and cathodic current signals ofelectrodes decreased. Furthermore, all the oxidation peak potentialsmoved positively as a function of bioleaching time, and the oxidationpeak of intermediate species (CuxS) existed throughout the wholebioleaching process.Miseq High throughput sequencing method was used to analyse thecommunity structure of the mixed moderate thermophiles in bioleachingof gold ores with and without homocysteine.The results showed that therewere many species of bacteria in bioleaching, but three species weredominant species and they were Acidithiobacillus, Leptospirilliu ferriphilum and Acidiphilium. Among of these species, the relativeabundance of Acidithiobacillus was the highest which reached to64.7%.24days later, the relative abundance of Leptospirilliu ferriphilum andAcidiphilium increased, and reached to10.3%and9.6%respectfully,while the relative abundance of Acidithiobacillus decreased to45.6%.When homocysteine was added, the relative abundance ofAcidithiobacillus decreased to47.2%, and the relative abundance ofLeptospirilliu ferriphilum and Acidiphilium increased to12.1%and11.3%. The result of heatmap showed that during the bioleaching proeess,community structure of the mixed moderate thermophiles in had changedgreatly. Furthermore, adding homocysteine did not change the communitystructure of the mixed moderate obviously.Rhodamine B fluorescent probe was designed and synthesized for thedetection of Fe3+, which can form complex with Fe3+, and causedenhancement of fluorescence, while other metal ions, such us Cu2+, Mg2+et, al, caused no significant or little enhancement of fluorescence.So thisprobe was selective and sensitive to Fe3+.Further more, in acid solution,the fluorescence was stronger.When used in bioleaching system,fluorescence enhanced with bioleaching proceeding. There was obviousdependency between fluorescence enhanced and the Fe3+concentrationincrease. Therefore, Rhodamine B fluorescent probe synthesized can detect Fe3+in bioleaching and was regarded as a effective and sensitivemethod.