Xiuxiang Tao

Bio-solubilization of Chinese lignite I：extra-cellular protein analysis

Abstract A white rot fungus strain, Trichoderma sp. AH, was isolated from rotten wood in Fushun and used to study the mechanism of lignite bio-solubilization. The results showed that nitric acid pretreated Fushun lignite was solubilized by T. sp. AH and that extracellular proteins from T. sp. AH were correlated with the lignite bio-solubilization results. In the presence of Fushun lignite the extracellular protein concentration from T. sp. AH was 4.5 g/L while the concentration was 3 g/L in the absence of Fushun lignite. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the extracellular proteins detected at least four new protein bands after the T. sp. AH had solubilized the lignite. Enzyme color reactions showed that extracellular proteins from T. sp. AH mainly consisted of phenol-oxidases, but that lignin decomposition enzymes such as laccase, peroxidase and manganese peroxidases were not present.

Characteristics of oxygen consumption of coal at programmed temperatures

Abstract Oxygen consumption is an important index of coal oxidation. In order to explore the coal-oxygen reaction, we developed an experimental system of coal spontaneous combustion and tested oxygen consumption of differently ranked coals at programmed temperatures. The size of coal samples ranged from 0.18∼0.42 mm and the system heat-rate was 0.8°C/min. The results show that, for high ranked coals, oxygen consumption rises with coal temperature as a piecewise non-linear process. The critical coal temperature is about 50 °C. Below this temperature, oxygen consumption decreases with rising coal temperatures and reached a minimum at 50 °C, approximately. Subsequently, it begins to increase and the rate of growth clearly increased with temperature. For low ranked coals, this characteristic is inconspicuous or even non-existent. The difference in oxygen consumption at the same temperatures varies for differently ranked coals. The results show the difference in oxygen consumption of the coals tested in our study reached 78.6% at 100 °C. Based on the theory of coal-oxygen reaction, these phenomena were analyzed from the point of view of physical and chemical characteristics, as well as the appearance of the coal-oxygen complex. From theoretical analyses and our experiments, we conclude that the oxygen consumption at programmed temperatures reflects the oxidation ability of coals perfectly.

Comparison Analysis of Coal Biodesulfurization and Coal's Pyrite Bioleaching with Acidithiobacillus ferrooxidans

Acidithiobacillus ferrooxidans (A. ferrooxidans) was applied in coal biodesulfurization and coals pyrite bioleaching. The result showed that A. ferrooxidans had significantly promoted the biodesulfurization of coal and bioleaching of coals pyrite. After 16 days of processing, the total sulfur removal rate of coal was 50.6%, and among them the removal of pyritic sulfur was up to 69.9%. On the contrary, after 12 days of processing, the coals pyrite bioleaching rate was 72.0%. SEM micrographs showed that the major pyrite forms in coal were massive and veinlets. It seems that the bacteria took priority to remove the massive pyrite. The sulfur relative contents analysis from XANES showed that the elemental sulfur (28.32%) and jarosite (18.99%) were accumulated in the biotreated residual coal. However, XRD and XANES spectra of residual pyrite indicated that the sulfur components were mainly composed of pyrite (49.34%) and elemental sulfur (50.72%) but no other sulfur contents were detected. Based on the present results, we speculated that the pyrite forms in coal might affect sulfur biooxidation process.

Bio-solubilization of Chinese lignite II:protein adsorption onto the lignite surface

Abstract Lignite bio-solubilization is a promising technology for converting solid lignite into oil. This study concerns the adsorption of lignite-solubilizing enzymes onto the lignite surface. Adsorption capacity, infrared spectral analysis and driving forces analysis are studied as a way to help understand the bio-solubilization mechanism. The results show that the amount of lignite bio-solubilization is proportional to the amount of adsorbed lignite-solubilizing enzymes. An increase in lignite-solubilizing enzyme adsorption of 10% leads to a 7% increase in lignite bio-solubilization. However, limited amounts of enzymes can be adsorbed by the lignite, thus resulting in low percentages of bio-solubilization. Infrared spectral analysis shows that side chains, such as hydroxyl and carbonyl, of the lignite structure are the main, and necessary, structures where lignite-solubilizing enzymes attachto the lignite. Furthermore, driving force analysis indicates that the electrostatic force between lignite and enzymes is the main adsorption mechanism. The forces are influenced by solution pH levels, the zeta potential of the lignite and the isoelectric points of the enzymes.

Degradation of lignite model compounds by the action of white rot fungi

Abstract Three compounds modeled on the lignite structure were chosen for experimental degradation by different fungi strains. Culture conditions and extracellular enzyme activities were optimized. The growth curves of the strains were determined to study mycelium dry weight and protein content changes. Gas chromatography and infrared spectroscopy were used to detect changes of functional groups before and after the action of the fungi on the model compounds. Possible decomposition products and degradation mechanisms were proposed. The research findings show that C. Versicolor and Golden Mushroom can grow in presence of the model compounds. The optimum culture conditions were a pH of 6.0, a carbon-nitrogen ratio of five and a Tween-80 concentration of 0.1%. Newly produced substances were found by gas chromatography. Infrared analysis showed that the model compounds degraded under the action of the microorganisms.

X-ray photoelectron spectroscopy study on the chemical forms of S, C and O in coal before and after microwave desulphurisation

The chemical forms of S, C and O of high-sulphur bituminous coal were analysed before and after microwave desulphurisation by using X-ray photoelectron spectroscopy (XPS). Sulphur existed as 17.908% mercaptan (sulfoether) and 62.160% thiophene before microwave irradiation and decreased to 4.644% mercaptan (sulfoether) and 49.483% thiophene after irradiation with assistance of alkali solution. On the contrary, sulphur that occurred in the chemical form of sulfone (sulfoxide) and sulphates increased from 7.516% and 12.416% to 14.697% and 31.176%, respectively. This increase may be due to the mobility of sulphur-containing species and the oxidisation effect of desulphurisation additive. After irradiation, the relative contents of C-H and C-C groups decreased while C=O and COO-groups in the coal increased. This shows that the organic carbon is oxidised to a higher valence state. These observed changes in functionalities led to a low coking quality of the desulphurised coal. [Received: February 5, 2015; Accepted: December 12, 2015]

A study on soil basic characteristics, main microbial flora and typical metal fraction surrounding coal gangue dump in Xiangtan Hunan Province, south of China

During the coal ore mining and utilization process, coal and its associated minerals have been discharged as coal gangue. Upon interacting with the water, air and microbial oxidation, the harmful metals and sulfides in coal gangue will cause serious pollution. In present work, the basic chemical characteristics, main microbial flora and typical metal speciation of the soil around coal gangue dump in Liejiaqiao coal mine, xiangtan mining area, Hunan province south of China were analyzed with several methods including XRF, XRD, microbial plate culture count and Tessier’s sequential extraction scheme. Correlation, cluster and principal component analysis (PCA) were used to estimate the possible main factors of coal gangue dump’s effect on surrounding soil and their correlation with microbial flora. Research results showed that the soil surrounding the coal gangue dump had low pH and microbial abundance (including bacteria, fungi and actinomycete). The soil samples contained high levels of metals especially for Mn, Fe and Cr. Tessier’s sequential extraction results showed that Fe, Mn and Cr were mainly associated residual fraction. Risk assessment revealed that Fe and Cr had lower risk than Mn to the surrounding environment. Based on PCA and cluster analysis results, the obtained ten samples can be divided into three groups. Among of them, mobile fraction of metals, microbial abundance could be the main factor reflecting the soil pollution around the coal gangue dump. Furthermore, correlation analysis showed that the abundance of bacteria and actinomycete had significant relationship (at 0.05 levels) with mobility factor of Fe and pH condition of the soil samples, respectively.