Knowledge Management System Of Institute of process engineering,CAS
|Place of Conferral||北京|
|Keyword||黄铁矿 控电位 接触作用 辉铜矿 酸平衡|
Pyrite is the most abundant sulfide minerals on earth, and the oxidation of pyrite is highly related to metallurgy of sulfide ore and also acid drainage generation by ore residue and waste. Pyrite is the source of the excessive acid and iron in copper sulfide bioheap. The dissolution rate of pyrite is significant correlation with redox potential in ferric sulfate solution. Microbial activity played important role in pyrite oxidation. The planktonic bacteria can oxidize Fe2+ to Fe3+ , consequently, redox potential was lifted. However the role of bacteria attached on pyrite was not fully elucidated. In this project, the independent developed instruments which can control the redox potential during the pyrite oxidation is used to elucidated the boundary condition of oxidation of pyrite. Based on the result above, bio-oxidation of pyrite in a solution with a redox potential below the rest potential of the mineral via thermo orbital Shaker was investigated with a novel method to study the relative effect of “contact mechanism” and “non-contact mechanism”. Confocal laser scanning microscopy (CLSM), atomic force microscopy (AFM) and scanning electron microscope (SEM) are used to investigate the extracellular polymeric substances (EPS) formation of mixed and attachment of microbes, and its influence on pyrite oxidation. We desire to deepen the understanding of the “contact mechanism” in the process of pyrite oxidation.The result shows the oxidation of pyrite is controlled by surface chemical reaction fitting shrinking core model and the dissolution rate is correlation with Eh in order of 11.265 under the controlled potential. The dissolution of pyrite was negligible if the redox potential fell to 650 mV, even at 60℃. Based on this result, Pyrite was oxidized by growth of mixed mesophilic microorganisms below 650mV. The pyrite was confirmed to be undissolved by leaching data and surface analysis, even with high activity leaching bacteria, 70% coverage rate on pyrite surface and forming biofilm. Thus, the “contact mechanism” of leaching bacteria wasn’t detected under 650mV. In addition, high acidity can inhibit the attachment of bacteria on pyrite. The conclusion point out the direction on inhibiting acid generation in copper sulfide bioheap system.Chalcocite is the most common secondary copper sulfides and one of the most important copper sulfide resources applied in metallurgy. Since 1980s, there have been more than 20 copper bioleaching operations. There exist prominent problems in heap bioleaching of chalcocite ores, however, especially low efficiency and long period of copper extraction. In order to study the role of bacteria played in the process of chalcocite dissolution, relatively high-grade natural chalcocite (Cu2S) was leached in column under controlled redox potential (Eh) to simulate bioleaching test which was also conducted in similar column instrument.The result shows the second stage is controlled by in-diffusion that Fe3+ diffuse from mineral surface to S-CuS interface. The ratio between chemical reaction and diffusion gradually decreases with process of reaction and effect of diffusion enhanced. The leaching bacteria indeed accelerate the dissolution rate of CuS in the second stage. The rate constant of bioleaching test was 2.35 higher than the chemical leaching test. Different type of bacteria which played their own roles make the accelerating processes.At last, based on the composition of ore and chemical reaction in secondary copper sulfides bioheap system , the empirical equation which can be used to evaluate the overall acid generation was obtained from relation between the equations. The study shows that the oxidation reaction of S has a little effect on the acid balance and the empirical equation was confirmed to effectively evaluate the acid generation and the dissolution rate of pyrite at balance point. Based on the dissolution rate of pyrite combined with the pyrite and gangue content in ore , acid generation can be adjusted in the secondary copper sulfides bioheap.
|刘畅. 次生硫化铜矿生物堆浸中微生物“接触作用”与酸平衡研究[D]. 北京. 中国科学院研究生院,2016.|
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