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Bioleaching is regarded as an essential technology to treat low grade minerals, with the distinctive superiorities of lower-cost and environment-friendly compared with traditional pyrometallurgy method. However, the bioleaching efficiency is unsatisfactory owing to the passivation film formed on the minerals surface. It is of particular interest to know the dissolution and passivation mechanism of sulfide minerals in the presence of microorganism. Although bioleaching can be useful in extracting metals, it is a double-edged sword. Metallurgical activities have caused serious environmental problems such as acid mine drainage (AMD). The understanding of some common sulfide minerals bioleaching processes and protection of Amd environment is reviewed in this article.

Bioleaching experiments combined with X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were conducted to investigate three kinds of bornites from different regions leached by moderately thermophilic mixed bacteria of Leptospirillum ferriphilum YSK, Acidithiobacillus caldus D1 and Sulfobacillus thermosulfidooxidans ST. The results of bioleaching experiments showed that the leaching efficiency and the redox potential were significantly increased. The copper extraction efficiencies of three kinds of bornite maintained rapid growth until around the 12th day and no longer increased after the 18th reaching 83.7%, 96.5% and 86.6%, respectively. The XRD results of the leaching residue indicated that three kinds of bornites all produced jarosite in the late stage of leaching, and the leaching residues from of Daye Museum and Yunnan Geological Museum contained a mass of elemental sulfur. XPS analysis and scanning electron microscopy experiments showed that the surface of mineral particles was jarosite and the copper in the leaching residue was almost dissolved.

The phase transformation of chalcopyrite and the effect of its phase status on bacterial leaching were studied. Under the protection of high-purity argon, different temperatures (203, 382 and 552 °C) were applied to natural chalcopyrite to complete the phase change. In addition, the chalcopyrite was bioleached before and after the phase change. The results show that the chalcopyrite heated at 203 and 382 °C remained in the α phase, whereas the chalcopyrite changed from α to β phase at 552 °C. The leaching rates of chalcopyrite after the phase transitions at 203, 382 and 552 °C were 32.9%, 40.5% and 60.95%, respectively. Further, the crystal lattice parameters of chalcopyrite increased and lattice energy decreased, which were the fundamental reasons for the significant increase in leaching rate. Electrochemical experiments demonstrated that with increasing annealing temperature, the polarization resistance decreased and corrosion current density increased. The higher the oxidation rate was, the higher the leaching rate was.

The leaching of chalcopyrite under different redox potentials was studied with a redox potential controlling device based on microcontroller technology. The leaching test was carried out in a 500 mL flask with 4 g pure chalcopyrite and 200 mL sulfuric acid. The additional total Fe concentration was 0.1 mol/kg, and the initial pH was 0.7. Chalcopyrite leaching tests with initial redox potential of 400 mV and 600 mV (vs. Ag/AgCl, the same below) and controlled redox potential of 350 mV, 400 mV, 450 mV, 500 mV, and 600 mV were carried out at a temperature of 60 °C and a stirring speed of 300 rpm. The results showed that the dissolution of chalcopyrite could not be hindered until the granular intermediates (S0 and Sn2−) accumulated to a certain amount on the chalcopyrite surface. The main passivating species in chalcopyrite dissolution may be iron-deficient polysulfides. At 400 mV, the chalcopyrite passivation by polysulfides was overcome by the galvanic effect between pyrite and chalcopyrite, and the chalcopyrite was rapidly oxidized with Cu leaching rate reaching up to 32% in 7 h, while it was only 15% in the other experimental groups. However, at 450–500 mV, pyrite was oxidized and the galvanic effect between chalcopyrite and pyrite was destroyed, leading to a significant decrease in Cu leaching rate. When the redox potential was 600 mV, the dissolution of metal-deficient polysulfides was promoted, thus, the passivation was weakened.

Chalcopyrite (CuFeS2) is the most abundant copper-containing resource in the earth and is also widely distributed in solid wastes and secondary resources. Biohydrometallurgy (bioleaching) is considered as a promising minerals processing and extractive metallurgy technology because of its environmental and economic advantages over the conventional beneficiation-pyrometallurgy process, and the bioleaching of chalcopyrite is always a challenge because chalcopyrite can be easily passivated in bioleaching. Hence, it is important to understand the dissolution process and passivation mechanism of chalcopyrite in bioleaching. In this paper, the dissolution process and passivation mechanism of chalcopyrite bioleaching have been summarized and discussed according to previous publications. The reported possible passivating species are mainly S-containing species consisting of polysulfide (Sn2−), elemental sulfur (S0) and insoluble sulfate (SO42−). The effects of physicochemical properties of chalcopyrite and multiple factors on the dissolution and passivation mechanism of chalcopyrite bioleaching have been summarized. We particularly discussed the role of redox potential in chalcopyrite bioleaching and its controlling techniques.

This study investigated a potential method for the removal of arsenic from enargite leach solution containing 5.86 g/L As(V) by precipitation of magnesium ammonium arsenate (MAA). The experimental ...

Theoretically, controlling redox potential to a relatively low value and inhibiting jarosite formation on the chalcopyrite surface would be an effective strategy to accelerate the bioleaching of chalcopyrite. In this work, using limonite as seed crystals, the effects of the goethite precipitation process on the bioleaching of chalcopyrite were studied for the first time. The bioleaching results showed that the addition of limonite controlled the redox potential in an appropriate range and promoted chalcopyrite dissolution through the removal of ferric (Fe3+) ions. X-ray diffraction and scanning electron microscope analyses indicate that limonite significantly induced the goethite precipitation process and inhibited the production of jarosite. We conclude that promoting the goethite precipitation process with limonite is an effective strategy in accelerating the bioleaching process of chalcopyrite.

Alkaline leaching is a promising treatment to extract arsenic from enargite. This study investigates the feasibility of leaching enargite concentrate in the presence of pyrite in alkaline solution with sodium hydroxide only. Single factor and orthogonal experiments were performed to determine the effect of sodium hydroxide concentration, temperature, leaching time and liquid-to-solid ratio on enargite dissolution and to optimize leaching conditions. The results indicate that sodium hydroxide concentration has the greatest effect on arsenic dissolution from enargite, while the liquid-to-solid ratio has the smallest effect. Finally, over 99% of arsenic was removed using optimal conditions. Characterization of the leach residue by XRD and SEM-EDS analyses showed that enargite was converted into non‑arsenic copper sulfides such as anilite (Cu7S4), geerite (Cu8S5) and djurleite (Cu31S16). This research is applicable to solving problems related to arsenic pollution.

To investigate the correlation between CD44v6 and cyclooxygenase-2(COX-2) expression and recurrence and deterioration of pleomorphic adenoma of parotid gland.Immunohistochemistry was used to detect the expression of CD44v6 and COX-2 in 19 normal parotid tissues, 25 primary pleomorphic adenomas, 15 first recurrent pleomorphic adenoma, 15 second recurrent pleomorphic adenoma and 13 cancer in pleomorphic adenomas. The correlation between CD44v6 and COX-2 and the recurrence and deterioration of pleomorphic adenomas was evaluated using SPSS 15.0 software package.The positive expression rate of CD44v6 in normal parotid gland, primary pleomorphic adenoma, first recurrent pleomorphic adenoma, second recurrent pleomorphic adenoma and cancer was 5.26%, 44.00%, 60.00%, 93.37% and 100.00%, respectively;and the positive expression rate of COX-2 was 10.53%, 40.00%, 63.33%, 93.37% and 100.00%, respectively. There was significant difference in the positive expression intensity of CD44v6 and COX-2 among the groups (P0.05). The positive expression rate and intensity of CD44v6 and COX-2 in normal parotid gland tissue were significantly lower than those in other groups (P0.05). There was no significant difference in the positive expression rate and intensity of CD44v6 between primary pleomorphic adenoma and first recurrent pleomorphic adenoma (P0.05). There was no significant difference in the expression intensity of COX-2 between the two groups (P0.05), but the positive expression rate of COX-2 between the two groups was not significant(P0.05). The positive expression rate and intensity of CD44v6 and COX-2 in the second recurrent pleomorphic adenoma were significantly higher than those in the first recurrent pleomorphic adenoma(P0.05), but there was no significant difference between the two groups(P0.05). CD44v6 in the second recurrent pleomorphic adenoma and cancer was significantly higher than that in the first recurrent pleomorphic adenoma(P0.05). There was no significant difference in the expression rate and intensity of COX-2 (P0.05).CD44v6 and COX-2 may play an important role in promoting occurrence, invasion, recurrence and deterioration of pleomorphic adenoma through synergistic action.

The hydrophobic flocculation flotation of rutile fines in the presence of styryl phosphonic acid (SPA) was investigated by flotation tests, zeta-potential measurement, optical microscope observation, laser-based particle size analysis, adsorption measurements and DLVO theory. The flotation tests indicated that rutile fines could be flocculated by SPA, and pH, shear force (stirring speed) and stirring time played significant roles in flocculation. The isoelectric point (IEP) and zeta-potential in whole range all moved to negative values as SPA was added according to the results from zeta-potential measurement. It was demonstrated that the primary reason for above was chemical adsorption. The laser-based particle size results showed the particle size at a stirring speed of 1800 r/min and 1000 mg/L SPA was the largest in all experiments. Furthermore, using the optical microscope observation and flotation tests, it was important for flotation of rutile fines to produce the flocculant. In the light of above-mentioned facts, floc flotation of rutile fines could be induced in the form of chemical adsorption by SPA to increase particle size. The data calculated from DLVO theory also indicated that chemical adsorption was the main reason for the formation of flocculant.

The adsorption behavior and mechanism of Bi(III) ions on the rutile–water interface were investigated through micro-flotation, Zeta potential measurement, adsorption amount measurement and X-ray photoelectron spectroscopy (XPS). According to the results of micro-flotation, Bi(III) ions could largely improve the rutile flotation recovery (from 62% to 91%), and they could increase the activating sites and reduce the competitive adsorption between nonyl hydroxamic acid negative ions and OH− ions, which determined that Bi(III) ions were capable of activating rutile flotation. The adsorption of Bi(III) ions onto the rutile surface led to the shift of Zeta potential into the positive direction, which was good for the adsorption of nonyl hydroxamic acid anions. In addition, the results of XPS indicated that the chemical environment around Ti atom had not changed before and after the adsorption of Bi(III) ions. Based on the adsorption mechanism of Bi(III) ions, it was deduced that firstly Bi(III) ions occupied the vacancies of the original Ca2+, Mg2+ and Fe2+ ions on the rutile surface; secondly Bi(III) ions covered on the rutile surface in the form of hydroxides.

This study explores the influences of external iron ions on the dissolution behavior of covellite minerals at different temperatures. External iron ions can significantly accelerate covellite dissolution. The copper extraction of acid covellite leaching was less than 5%, while the addition of external iron ions (ferric or ferrous ions, Fe3+/Fe2+) effectively enhanced covellite dissolution. Covellite copper extraction with 0.1 mol/L Fe2+ was 25% at 303 K and 40% at 318 K after 18 days, and for leaching systems with 0.1 mol/L Fe3+, it was approximately 40% at 303 K and 60% at 318 K. The dissolution process of covellite with external iron ions can be divided into two stages. The dissolution kinetics at the first stage are controlled by the chemical reaction between iron ions and covellite, as the generated elemental sulfur has not yet blocked the covellite surface. Compared with ferrous ions, ferric ions further increase the dissolution rate of covellite, which is also suggested by the scanning electron microscopy analysis results. Additionally, Fe3+ accelerates the release of copper ions by effectively reducing the particle size of covellite. In the second stage (copper extraction >40%), the reaction kinetics shift to the mixed control of the surface chemical reaction with iron ions and diffusion due to the accumulation of an elemental sulfur layer on the surface. Although Fe2+ cannot directly oxidize covellite, the electron exchange between Fe2+ and oxygen is improved through the covellite mineral, which is attributed to its metallic properties. Then, the ferric ions generated in the above process gradually corrode covellite. In addition, the temperature rise can significantly accelerate the oxidation reaction process of iron ions with covellite by forming a more porous corrosive structure. Finally, leaching bacteria (Acidithiobacillus caldus and Leptospirillum ferriphilum) are proved to boost copper extraction from covellite by transforming Fe2+ into Fe3+ and eliminating surface elemental sulfur passivation. However, dense passivation layers inevitably form on the covellite surface at the end of bioleaching, which passivates the subsequent dissolution process.

Chemical element analysis and X-ray diffraction (XRD) analysis showed that the two chalcopyrite minerals were of high purity. A mixed culture of moderately thermophiles was used for chalcopyrite bioleaching at 45°C and the copper recovery of chalcopyrite (a) and chalcopyrite (b) was 66.1% and 21.4%, respectively, after 19 days of leaching. Bioleaching behavior of the two different chalcopyrite samples was studied through comparing the lattice parameter and grain size of chalcopyrite. It was shown that lattice parameter and grain size are not the key factors affecting the leaching of chalcopyrite. The corrosion current density of chalcopyrite (a) calculated through Tafel curves was 1.149 μA/cm2, while that of chalcopyrite (b) was only 0.5696 μA/cm2. The higher corrosion current density suggested that chalcopyrite (a) can be more easily dissolved than chalcopyrite (b).

Zhong-Ming Huang, He Xiao, Zhi-Gang Ji, Wei-Gang Yan, Yan-Sheng Zhang Department of Urology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100730, China Background: To evaluate the evidence available on the effects and safety of tension-free vaginal tape (TVT) versus transobturator tape (TOT) for female stress urinary incontinence therapy based on randomized controlled trials (RCTs). Methods: PubMed, Cochrane, Embase, Wanfang, China National Knowledge Infrastructure, and Weipu database were searched up to July 2017 to identify relevant studies, including qualified RCT and quite-RCT and literature sources. Relative risks (RRs), mean difference (MD), and 95% CI were calculated in our review. Result: Twenty-eight RCTs were involved in the meta-analysis with 2,505 patients in the TVT group and 2,477 patients in the TOT group. The aggregated results indicated that TOT significantly decreased the operative time (MD, −1.27; 95% CI: −1.77 to −0.76) and hospital stay (MD, −0.62; 95% CI: −1.08 to −0.17) when compared with TVT. Besides, the complications (RR, 0.86; 95% CI: 0.64–1.16) and blood loss (MD, −0.29; 95% CI: −0.71 to 0.14) were decreased in TOT but with no statistical significance; the change of VAS score (MD, 0.07; 95% CI: −0.05 to 0.19), IIQ-7 score (MD, 0.06; 95% CI: −0.03 to 0.15), and UDI-6 score (MD, 0.15; 95% CI: −0.19 to 0.48) were larger in TOT group than in TVT group, but still, with no statistical significance. However, there was no significant difference of cure rate (RR, 1.00; 95% CI: 0.96–1.04) and satisfied rate (RR, 1.00; 95% CI: 0.96–1.04) between the 2 groups. Conclusion: TOT may have more valid effects than TVT in operative time and hospital stay. Besides, TOT method showed fewer complications and blood loss than TVT, but there was no significant difference between them. The scores of VAS, incontinence impact questionnaire short form-7 (IIQ-7), and urogenital distress inventory short form-6 (UDI-6) were higher in TOT than TVT, but still no significant difference was observed. However, more studies with higher quality and larger sample size that are multicentric and have longer follow-up in the form of RCTs are warranted to confirm the current findings. Keywords: TVT, TOT, SUI, meta-analysis, randomized controlled trial

The composition of passive layer of chalcopyrite was investigated by X-ray photoelectron spectroscopy (XPS), accompanied with cyclic voltammetry (CV). The leaching experiment shows that the extraction rates of Cu with leaching for 30 d by sterile control and microorganisms are 4.0% and 21.5%, respectively. In comparison, 3.8% and 10.5% Fe are leached by sterile control and microorganisms, respectively. The results of XPS studies suggest that Fe atoms dissolve preferentially from the chalcopyrite lattice, and disulfide (S 2 2− ), polysulfide (S n 2- ) and elemental sulfur (S 0 ) are identified on the chalcopyrite surfaces leached by sterile control and microorganisms. Additionally, sulfate (SO 4 2- ) is detected on the chalcopyrite surfaces leached by microorganisms, and most of it probably originates from jarosite. The analysis of CV results reveals that metal-deficient sulfide (Cu 1- x Fe 1- y S 2- z , y > x ) and elemental sulfur (S 0 ) passivate the surface of chalcopyrite electrode. The elemental sulfur and/or jarosite coating on the chalcopyrite surface may have impact on the leaching process; however, the disulfide, polysulfide or metal-deficient sulfide plays a more key role in the chalcopyrite leaching.

Chalcopyrite (CuFeS2) and marmatite [(Zn, Fe) S] are associated together most of the time in the raw ores and flotation concentrates. In this work, the interactions between chalcopyrite and marmatite during bioleaching by moderately thermophilic bacteria were investigated by electrochemical measurements and bioleaching experiments. In the initial stage of bioleaching of mixture of chalcopyrite and marmatite, the dissolution of marmatite was preferential, and was significantly accelerated with the addition of chalcopyrite because of the galvanic effect and catalytic effect of Cu2+ ions, while the dissolution of chalcopyrite was inhibited mainly due to the galvanic effect before the accomplishment of marmatite dissolution. Chalcopyrite dissolves fast when the dissolution of marmatite is finished, and small amount of marmatite cannot inhibit the final copper extraction of chalcopyrite if leaching time was long enough. Therefore, stepwise or selective bioleaching was feasible in processing mixture of chalcopyrite and marmatite to avoid complex flotation process in separating chalcopyrite and marmatite.

Additive Gauss white noise is one of the most commonly observed interferences in practical engineering applications. This paper proposed an algorithm for the adaptive determination of the optimal wavelet decomposition level based on Jarque-Bera test in efforts to solve the filtering problem of additive white Gaussian noise signal. By, The optimal decomposition level of wavelet is determined by testing the white noise which was realized by calculating skewness (S) and kurtosis (K) of the parameters. With signal-to-noise ratio (SNR) as the measurement index, simulation results show that the presented algorithm have higher accuracy, and better filtering effect on low SNR signals compared with nonparametric test methods.