Contributions of Microbial "Contact Leaching" to Pyrite Oxidation under Different Controlled Redox Potentials

The function of microbial contact leaching to pyrite oxidation was investigated by analyzing the differences of residue morphologies, leaching rates, surface products, and microbial consortia under different conditions in this study. This was achieved by novel equipment that can control the redox potential of the solution and isolate pyrite from microbial contact oxidation. The morphology of residues showed that the corrosions were a little bit severer in the presence of attached microbes under 750 mV and 850 mV (vs. SHE). At 650 mV, the oxidation of pyrite was undetectable even in the presence of attached microbes. The pyrite dissolution rate was higher with attached microbes than that without attached microbes at 750 mV and 850 mV. The elemental sulfur on the surface of pyrite residues with sessile microorganisms was much less than that without attached microbes at 750 mV and 850 mV, showing that sessile acidophiles may accelerate pyrite leaching by reducing the elemental sulfur inhibition. Many more sulfur-oxidizers were found in the sessile microbial consortium which also supported the idea. The results suggest that the microbial "contact leaching" to pyrite oxidation is limited and relies on the elimination of elemental sulfur passivation by attached sulfur-oxidizing microbes rather than the contact oxidation by EPS-Fe

Competitive Growth of Sulfate-Reducing Bacteria with Bioleaching Acidophiles for Bioremediation of Heap Bioleaching Residue

Mining waste rocks containing sulfide minerals naturally provide the habitat for iron- and sulfur-oxidizing microbes, and they accelerate the generation of acid mine drainage (AMD) by promoting the oxidation of sulfide minerals. Sulfate-reducing bacteria (SRB) are sometimes employed to treat the AMD solution by microbial-induced metal sulfide precipitation. It was attempted for the first time to grow SRB directly in the pyritic heap bioleaching residue to compete with the local iron- and sulfur-oxidizing microbes. The acidic SRB and iron-reducing microbes were cultured at pH 2.0 and 3.0. After it was applied to the acidic heap bioleaching residue, it showed that the elevated pH and the organic matter was important for them to compete with the local bioleaching acidophiles. The incubation with the addition of organic matter promoted the growth of SRB and iron-reducing microbes to inhibit the iron- and sulfur-oxidizing microbes, especially organic matter together with some lime. Under the growth of the SRB and iron-reducing microbes, pH increased from acidic to nearly neutral, the Eh also decreased, and the metal, precipitated together with the microbial-generated sulfide, resulted in very low Cu in the residue pore solution. These results prove the inhibition of acid mine drainage directly in situ of the pyritic waste rocks by the promotion of the growth of SRB and iron-reducing microbes to compete with local iron and sulfur-oxidizing microbes, which can be used for the source control of AMD from the sulfidic waste rocks and the final remediation

<p>Evidence of weak interaction between ferric iron and extracellular polymeric substances of Acidithiobacillus ferrooxidans</p>

Although ferric iron in extracellular polymeric substances (EPS) was believed to be pivotal in bioleaching, the real existing form of ferric iron in EPS has remained poorly understood. In this study, whole cells of Acidithiobacillus ferrooxidans were used to study the composition and properties of EPS. The components sugars, proteins and uronic acids could be extracted from cells rich in EPS. Four distinct surface functional groups were characterized on the bacterial surfaces by the fitting of titration data. Subsequently, these functional groups were confirmed as carboxyl groups, phosphoryl groups, thiol groups, and amine groups by combining FTIR and XPS. However, with the help of modeling results and FTIR, these functional groups failed to dissociate protons in a strong acidic environment. The protonated functional groups could unlikely complex ferric iron according to the site-specific surface complexation theory. Besides, the isolated EPS could not sharply reduce the concentration of free ferric ions, and the ferric iron could be removed by washing the cell surfaces with HClO4. These results indicate that there is no strong chemical interaction between bacteria and ferric iron. This study suggests a weak interaction of ferric iron with the EPS of A. ferrooxidans, and gives some deeper insight into the microenvironment of EPS

Plasma-Assisted Surface Interactions of Pt/CeO2 Catalyst for Enhanced Toluene Catalytic Oxidation

The performance of plasma-modified Pt/CeO2 for toluene catalytic oxidation was investigated. Pt/CeO2 nanorods were prepared by wet impregnation and were modified by thermal (PC-T), plasma (PC-P), and combined (PC-TP and PC-PT) treatments. The modified catalysts were characterized by TEM (transmission electron microscope), BET (Brunauer-Emmett-Teller), H2-TPR, O2-TPD, XPS, UV-Raman, and OSC tests. The significant variation of the surface morphologies and surface oxygen defects could have contributed to the modification of the Pt/CeO2 catalysts via the plasma treatment. It was found that plasma could promote the surface interaction between Pt and CeO2, resulting in the thermal stability of the catalyst. The Pt-Ce interaction was also conducive to an increase in the number of oxygen vacancies. Furthermore, PC-PT and PC-TP showed a significant difference in oxygen vacancy concentrations and catalytic activities, which illustrated that the treatment sequence (plasma and thermal treatment) affected the performance of Pt/CeO2. The PC-PT sample showed the highest catalytic activity with T100 at 205 &deg;C. This work thus demonstrates that plasma in combined treatment sequences could assist surface interactions of catalysts for enhanced toluene catalytic oxidation

Waterloo Building Dataset: A city-scale vector building dataset for mapping building footprints using aerial orthoimagery

Automated building footprint extraction is an important area of research in remote sensing with numerous civil and environmental applications. In recent years, deep learning methods, when trained on appropriate datasets, have far surpassed classical algorithms. In this paper, we present the Waterloo Building Dataset for building footprint extraction from very-high-spatial-resolution aerial orthoimagery. Our dataset covers the Kitchener-Waterloo area in Ontario, Canada, contains 117,000 manually labelled buildings, and extends over an area of 205.8 km2. At a spatial resolution of 12 cm, it is the highest resolution publicly available building footprint extraction dataset in North America. We provide extensive benchmarks of commonly used deep learning architectures trained on our dataset which can be used as baseline for future models. We also identify a key challenge in aerial orthoimagery building footprint extraction which we hope can be addressed in future research.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Additional file 5: of The effect of socioeconomic status on health-care delay and treatment of esophageal cancer

Table S5. Multivariable logistic regression analysis of between SES and treatment modalities