Electrochemical oxidation behavior of pyrite bioleaching by Acidthiobacillus ferrooxidans

The electrochemical oxidation behavior of pyrite in bioleaching system of Acidthiobacillusferrooxidans was investigated by cyclic voltammetry （CV）, polarization curve and electrochemical impedance spectroscopy （EIS）. The results show that in the presence or absence of A. ferrooxidans, the oxidation reaction of pyrite is divided into two steps： the first reaction step involves the oxidation of pyrite to S, and the second reaction step is the oxidation of S to SO4^2-. The oxidation mechanism of pyrite is not changed in the presence of A. ferrooxidans, but the oxidation rate of pyrite is accelerated. With the extension of reaction time of A. ferrooxidan with pyrite, the polarization current density of pyrite increases and the breakdown potential at which the passive film dissolves decreases. The impedance in the presence ofA. ferrooxidans is obviously lower than that in the absence of A. ferrooxidans, further indicating that microorganism accelerates the corrosion process of pyrite.

嗜热硫氧化硫化杆菌与喜温嗜酸硫杆菌混合浸出铁闪锌矿研究

采用正交试验,通过考察温度、pH值、喜温嗜酸硫杆菌接种时间和喜温嗜酸硫杆菌接种浓度4个因素,研究硫氧化硫化杆菌与喜温嗜酸硫杆菌混合菌对铁闪锌矿浸出的影响。试验结果表明:氧化硫细菌的加入,有助于消除铁闪锌矿浸出过程中生成的、覆盖在矿物表面的元素硫,使得硫氧化硫化杆菌和喜温嗜酸硫杆菌混合菌浸出铁闪锌矿的效果比单一硫氧化硫化杆菌浸出效果好;混合菌浸出铁闪锌矿时浸出率达到54.2%,而单一硫氧化硫化杆菌浸出时浸出率为46.8%。正交试验结果统计分析表明混合菌浸出铁闪锌矿的最优条件为:pH=1.8、第3 d接种喜温嗜酸硫杆菌和喜温嗜酸硫杆菌接种浓度2.5×106个/mL;其中pH值是影响混合菌浸出铁闪锌矿的主要因素,其次是喜温嗜酸硫杆菌接种浓度及喜温嗜酸硫杆菌接种时间。

平阳霉素加地塞米松局部注射治疗血管瘤的临床应用

目的观察平阳霉素加地塞米松局部注射治疗血管瘤的疗效及优越性。方法选择200例血管瘤(草莓状、海绵状及混合性)患者,常规消毒,瘤体内注射平阳霉素及地塞米松备用溶液。结果痊愈92例,显效84例,有效9例,无效15例,总有效率为92.5%(185/200)。无1例出现发热、过敏等不良反应。结论平阳霉素加地塞米松局部注射治疗血管瘤安全有效,值得推广使用。

Surface characterization of chalcopyrite interacting with Leptospirillum ferriphilum

The alteration of surface properties of chalcopyrite after biological conditioning with Leptospirillum ferriphilum was studied by adsorption,zeta-potential,contact angle and bioleaching tests.The strains of L.ferriphilum cultured using different energy sources（either soluble ferrous ion or chalcopyrite） were used.The adhesion of bacteria to the chalcopyrite surface was a fast process.Additionally,the adsorption of substrate-grown bacteria was greater and faster than that of liquid-grown ones.The isoelectric point（IEP） of chalcopyrite moved toward that of pure L.ferriphilum after conditioning with bacteria.The chalcopyrite contact angle curves motioned diversely in the culture with or without energy source.The results of X-ray diffraction patterns（XRD）,scanning electron microscopy（SEM） and energy-dispersive X-ray spectroscopy（EDS） analysis indicate that the surface of chalcopyrite is covered with sulfur and jarosite during the bioleaching process by L.ferriphilum.Furthermore,EDS results imply that iron phase dissolves preferentially from chalcopyrite surface during bioleaching.The copper extraction is low,resulting from the formation of a passivation layer on the surface of chalcopyrite.The major component of the passivation layer that blocked continuous copper extraction is sulfur instead of jarosite.

甲硝唑注射液和庆大霉素注射液交替冲洗治疗根尖区瘘管的疗效观察

目的:探讨甲硝唑注射液和庆大霉素注射液治疗根尖区瘘管的疗效。方法:124例根尖区瘘管患者随机分为两组:甲组和乙组,每组62例。甲组按常规进行根管治疗,治疗后瘘管行甲硝唑注射液和庆大霉素注射液交替冲洗治疗;乙组进行根管治疗后或同时,经瘘管搔刮后,在瘘管壁涂搽薄荷醇溶液,再经瘘管行甲硝唑注射液和庆大霉素注射液交替冲洗根尖瘘管,分别进行3、6、12个月的随访观察。结果:甲、乙组的成功率分别为83.87%,93.55%,两组比较,差异有统计学意义(P<0.05)。结论:甲硝唑注射液和庆大霉素注射液交替冲洗,配合瘘管搔刮,及瘘管壁涂搽薄荷醇溶液,治疗根尖区瘘管,具有疗效肯定,安全可靠及取材方便等优点,能有效节省医疗费用,是一种有效的治疗手段。

Bioleaching and electrochemical property of marmatite by Leptospirillum ferrooxidans

The effects of several variables on the bioleaching of marmatite with pure L. ferrooxidans were investigated. The results show that zinc extraction increases with the decrease of pulp density. Adjusting pH tol.6 during the bioleaching process has a positive effect to the dissolution of marmatite. External addition of Fe^3＋ ions accelerates the bioleaching, while the concentration of additional Fe^3＋ over 2.5 g/L weakens the acceleration effect due to the inhibition effect on bacteria growth and the promotion of jarosite production. The electrochemical measurements were used to make further understanding on the dissolution of marmatite with and without additional Fe^3＋ in the presence of L. ferrooxidans. The experimental data illustrate that additional Fe^3＋ ions could increase the corrosion current density, which is favorable to zinc extraction. The EIS spectra show that rate-limiting step does not change when Fe^3＋ is added.

Bioleaching of chalcopyrite by Leptospirillum ferriphilum

Chalcopyrite oxidation rates were examined under various conditions in the presence of Leptospirillum ferriphilum,in which the effects of different pulp content,inoculation amount,external addition of Fe3+ and initial pH value were studied.The bioleaching residues were investigated by X-ray diffractograms(XRD),scanning electron microscopy(SEM) and energy dispersion spectrum(EDS) analysis.The results show that low pulp concentration increases the leaching rate of copper,and external addition of Fe3+ is also beneficial to leaching chalcopyrite.The changes of inoculation amount and initial pH from 1.6 to 2.5 have a little effect on the final leaching rate.The results also imply that Fe3+ ions are important for bioleaching of chalcopyrite.At the end of bioleaching,jarosite and sulfur are observed on the surface of chalcopyrite residues by using XRD,SEM and EDS.With the passivation layer formed by jarosite and sulfur,the continuous copper extraction is effectively blocked.

Bioleaching and electrochemical properties of chalcopyrite by pure and mixed culture of Leptospirillum ferriphilum and Acidthiobacillus thiooxidans

The bioleaching of chalcopyrite was investigated using a pure and mixed culture consisting of iron-oxidizing Leptospirillum ferriphilum （L. ferriphilum） and sulfur-oxidizing Acidthiobacillus thiooxidans （.4. thiooxidans）. The electrochemical tests were conducted to investigate the bioleaching behavior of chalcopyrite by various bacteria. Bioleaching efficiency of chalcopyrite in mixed culture is higher than that in the pure culture of L.ferriphilum alone. The iron-oxidizing L.ferriphilum plays a dominant role during bioleaching of chalcopyrite in the mixed culture of L. ferriphilum and A. thiooxidans. During bioleaching, certain values of redox potential are beneficial to the decomposition of chalcopyrite. Jarosite and sulfur are observed as products of bioleaching. The addition of A. thiooxidans during leaching by L. ferriphilum can change the electrochemical control steps of leaching. The corrosion current density is substantially promoted in the culture involving bacteria, especially in the mixed culture.

Stepwise dissolution of chalcopyrite bioleaching by thermophile A.manzaensis and mesophile L. ferriphilum

Chalcopyrite dissolution was evaluated by bioleaching and electrochemical experiments with thermophile A. manzaensis（Acidianus manzaensis） and mesophile L. ferriphilum（Leptospirillum ferriphium） cultures at 65 ℃ and 40 ℃, respectively. It was investigated that the bioleaching of chalcopyrite was stepwise. It was reduced to Cu2 S at a lower redox potential locating in the whole bioleaching process by A. manzaensis at high temperature while only at initial days of bioleaching by L. ferriphilum at a relative low temperature. No reduced product was detected when the redox potential was beyond a high level（e.g., 550 m V（vs SCE）） bioleached by L. ferriphilum. Chalcopyrite bioleaching efficiency was substantially improved bioleached by A. manaensis compared to that by L. ferriphilum, which was mainly attributed to the reduction reaction occurring during bioleaching. The reductive intermediate Cu2 S was more amenable to oxidation than chalcopyrite, causing enhanced copper extraction.

Formation of passivation film during pyrrhotite bioleached by pure L. ferriphilum and mixed culture of L. ferriphilum and A. caldus

Bioleaching and electrochemical experiments were conducted to evaluate pyrrhotite dissolution in the presence of pure L.ferriphilum and mixed culture of L. ferriphilum and A. caldus. The results indicate that the pyrrhotite oxidation behavior is the preferential dissolution of iron accompanied with the massive formation of sulfur in the presence of L. ferriphilum, which significantly hinders the leaching efficiency. Comparatively, the leaching rate of pyrrhotite distinctly increases by 68% in the mixed culture of L. ferriphilum and A. caldus at the 3rd day. But, the accumulated ferric ions and high p H value produced by bioleaching process can give rise to the rapid formation of jarosite, which is the primary passivation film blocking continuous iron extraction during bioleaching by the mixed culture. The addition of A. caldus during leaching by L. ferriphilum can accelerate the oxidation rate of pyrrhotite, but not change the electrochemical oxidation mechanisms of pyrrhotite. XRD and SEM/EDS analyses as well as electrochemical study confirm the above conclusions.