The efficient utilization of lignite is a crucial area of research for the sustainable management of existing coal resources. One potential technique for cost-effective and environmentally friendly ...coal processing is the application of microbes or their derivatives to modify the surface of lignite for bioflotation. However, the precise process of surface modification between microbes and coal remains largely unknown. In this study, we focused on the use of a white-rot fungus called Hypocrea lixii AH and its various components, including spores, hyphae, extracellular polymer substances (EPSs), and culture solution, as biosurfactants for lignite modification. By employing techniques such as zeta potential analysis, induction time measurement, contact angle measurement, and Fourier infrared spectroscopy, we investigated the changes in the surface properties of raw and modified lignite. Furthermore, we conducted a preliminary bioflotation test using biosurfactants as collectors in order to explore the potential application of fungal modification in this context. Our results revealed that all biosurfactants were effective in improving the surface properties of lignite, with the EPS demonstrating the most prominent effect, followed by the culture solution, hyphae, and spores. The zeta potential and induction time of the modified lignite decreased, indicating enhanced hydrophilicity, while the contact angle exhibited a slight increase, suggesting a minor increase in hydrophobicity. Analysis of the Fourier infrared spectra indicated that EPS treatment resulted in the highest abundance of functional groups, including carboxyl, hydroxyl, and amidogen groups. Although fungal cells were found to improve the hydrophobicity of coal, they did not exhibit a significant effect on the flotation of lignite. Nonetheless, our findings suggest that fungal cells and their derivatives have the potential to remove or transform minerals present in lignite, particularly those containing sulfur. While they may not serve as effective bio-collectors in microflotation, their capability in mineral alteration makes them valuable candidates for lignite processing with a focus on mineral reduction.
•TPC formation equation of air or oily bubble on low-rank coal surface was fitted.•TPC spreading rate of oily bubbles on low-rank coal surface was higher than that of air bubbles before about ...20 ms.•Oily bubble surface is more hydrophobic than that of air bubble.
Flotation is an effective separation technology with a wide range of applications, and oily bubbles have recently been shown to be more effective than air bubbles at separating low-rank coal. However, the differences in the spreading behaviours of oily and air bubbles at the microscale have not yet been clarified. In this study, high-speed camera technology was used to characterise the interaction process of air and oily bubbles with low-rank coal particles. The three-phase contact (TPC) line formation behaviours of air and oily bubbles on the low-rank coal surface were observed in a deionised solution. At 0–20 ms, the oily bubbles spread more quickly on the low-rank coal surface than the air bubbles; the TPC spreading completion percentages of the oily and air bubbles were 97.58% and 70.73%, respectively. At 20–100 ms, the oily bubbles spread more slowly than the air bubbles because they respectively had 2% and 30% of the TPC spreading process to complete. The results indicated that the oily bubble surface was more hydrophobic than the air bubble surface.
This study focuses on the utilization of Aspergillus flavus(M-3) for the bioleaching mercury from coal, offering an alternative and environmentally to its clean utilization. The fungus was isolated ...from the soil near a high mercury coal mine in Lao Ying Shan (LYS), Guizhou. Utilizing direct mercury analysis, X-ray diffraction (XRD), and Fourier Transform-Infrared (FT-IR) analysis techniques, the transformation of mercury speciation, mineral components, and organic groups in the coal were analyzed before and after the bioleaching process. The findings of the study illustrated that the fungus M-3 exhibited a remarkable capacity for coal bioliquefaction and mercury leaching from LYS coal. Following a 15-day bioleaching process, a remarkable mercury leaching rate of 83.79% was achieved. Various forms of mercury speciation, including residue, organic matter, sulfide-bound, oxide-bound, exchangeable, and carbonate-bound forms, were released from the coal, with leaching rates ranging from 80.41% to 92.60%. XRD analysis indicated that the M-3 strain facilitated the dissolution of coal pyrite and the degradation of macromolecules, effectively loosening the coal structure. FT-IR analysis of raw and residual coal demonstrated the breakdown of the aromatic ring structure and introduced oxygen-containing functional groups by M-3. Overall, this study highlights the efficacy of bioliquefying coal using Aspergillus flavus (M-3) as a method for clean coal utilization while simultaneously bioleaching mercury.
Biosolubilisation of Chinese lignite Yin, Sudong; Tao, Xiuxiang; Shi, Kaiyi ...
Energy (Oxford),
06/2009, Letnik:
34, Številka:
6
Journal Article
Recenzirano
The biosolubilisation of coal is a promising coal processing technology for converting solid coal to liquid oil at ambient conditions. In this study, the biosolubilisation of Chinese lignite was ...studied using a fungus isolated from decaying wood. The intensity of biosolubilisation was determined by estimating the liquid formation time and by measuring the weight loss of the lignite granules gravimetrically. The biosolubilisation product (black liquid) was characterized by ultraviolet spectroscopy, infrared spectroscopy, gas chromatography–mass spectrometry, element analysis, and heating value. Results showed that this fungus isolated from the decaying wood solubilised 31.83% (by weight) of Chinese lignite to black liquid within 11 days at 27.5 °C. The biosolubilisation product mainly contained aromatic acids and chain hydrocarbons, and had organic function groups of hydroxyl, cyclane, carbonyl, ether linkage and aromatic rings. The heating value of the biosolubilisation product was 14 MJ/kg. Chemical analysis of the biosolubilisation product indicated that side chains of lignite were important structures in the biosolubilisation mechanism.
The interaction between coal, surfactants and enzymes was studied in this paper in order to investigate the role of surfactants in coal bio-solubilisation. The results showed that in the absence of ...the surfactants, limited enzymes were adsorbed onto the coal surface (<
0.5
mg/g, enzyme/coal), and then the coal bio-solubilisation occurred to small extents. Under these conditions, the extents of coal bio-solubilisation, characterized by the absorbance of reaction media at 450
nm, were all less than 0.1 (A450nm
<
0.1). But, in the presence of the surfactants, the adsorption of the enzymes onto the coal greatly improved (8.2
mg/g, enzyme/coal), leading to relatively high bio-solubilisation extents (A450nm
=
0.65). The main mechanism was that the surfactants modified the charges and the hydrophilic property of the coal surface such that more enzymes can contact and solubilise the coal. Therefore, during coal bio-solubilisation, surfactants mainly promoted the adsorption of enzymes onto coal to improve coal bio-solubilisation, rather than solubilised coal directly.
► Interaction between coal, surfactants and enzymes during coal bio-solubilisation. ► Without surfactants, limited enzymes were adsorbed onto coal surface. ► With surfactants, the adsorption of enzymes onto coal improved. ► Surfactants modified the charges and the hydrophilic property of coal surface. ► By promoting the adsorption, surfactants improved coal bio-solubilisation.
A mixed culture of A. ferrooxidans and A. thiooxidans isolated from a coal gangue dump was used to bioleach coal gangue in a column reactor to investigate the leaching of elements. The changes of ...metal ions (Fe, Mn and Cr) and sulfate in the leaching solution, elemental composition, mineral components and sulfur speciation of the coal gangue before and after bioleaching were analyzed by atomic absorption, anion chromatography, XRF, XRD and XPS. The results show that the mixed culture could promote the release of metal ions in coal gangue, with a leaching concentration of Fe > Mn > Cr. EC and Eh have significantly increased with the increase of metal ion concentrations in the leaching solution. XRF analyses show that the contents of Fe, Mn and S decreased in coal gangue after bioleaching. XRD results suggest that the bioleaching has impacts on minerals in coal gangue, particularly the Fe-containing components. XPS analyses show that sulfur speciation in the raw gangue samples was associated with sulfate, dibenzothiophene and pyrite sulfur. After continuous leaching by the mixed culture, the total sulfur, pyrite sulfur and sulfate sulfur in coal gangue decreased from 2.06% to 1.18%, 0.66% to 0.14% and 1.02% to 0.52%. The desulfurization rates of the pyrite and sulfate were 78.79% and 49.02 %. It is concluded that the mixed culture of these two microorganisms could effectively leach metals from coal gangue coupling with the oxidation of sulfide to sulfate. This study has provided fundamental information as a potential application in the recovery of valuable metals from coal gangue or environmental remediation related to gangue in the future.
•The desulfurization rate with microwave heating was improved by 26% compared with conventional heating.•Microwave heating promoted the conversion of low-valence sulfur to high-valence sulfur in ...coal.•The strength of CS bond can be reduced by microwave fields during oxidation reaction.•Non-thermal effect of microwave on oxidation reaction was not conducive to the dissociation CS bonds.
This work investigated the non-thermal microwave effect during organic sulfur removal from coal by microwave irradiation combined with oxidation assistants. XANES was used to analyze the change of sulfur forms in the desulfurization process of high organic sulfur coal under microwave heating and conventional heating conditions. The effects of microwave fields on the molecular properties, bond strength and reaction kinetic of organic sulfur-containing groups were studied by quantum chemical calculation. Results showed that the desulfurization rate with microwave heating improved by 26% at the same temperature compared with conventional heating. The XANES analysis indicated that microwave radiation promoted the transformation of low-valence sulfur into high-valence sulfur, which resulted in the sulfur in the treated coal mainly existing as heterocyclic sulfur and oxidized sulfur. For the theoretical calculation, it is observed that the nucleophilic reaction activity of sulfur-containing groups could be improved and the strength of CS bands could be reduced under the extra electric fields due to the non-thermal microwave effect. Besides, the reaction activation energy was reduced and the reaction rate was increased under the same extra electric fields, promoting the formation of oxidized sulfur in coal. Therefore, there was a competitive relationship between sulfur-containing bond dissociation and group oxidation under the action of microwave non-thermal effect, which provided a reference for coal desulfurization research.
Effects of hydrodynamics and surface chemistry properties on attachment interaction between low-rank coal particles and bubbles were investigated. The surfactants such as 2-ethyl hexanol, dodecyl ...amine hydrochloride, and sodium dodecyl sulfate were added to change the surface chemistry of low-rank coal particles. The relationship between induction time and bubble Reynolds number showed an index relationship. The induction time would become shorter while the energy barriers between particles and air bubbles are easily overcome with bubble Reynolds number increase. Therefore, the hydrodynamics and surface chemistry properties had a significant effect on the attachment interaction between low-rank coal particles and bubbles.
In this paper, effect of surfactants on the hydrophobicity of low rank coal particles by sliding time measurements was investigated. X-ray photoelectron spectrometer (XPS) analysis indicated that the ...surfaces of low rank coal particle consisted of many hydrophilic functional groups. It was observed that the sliding time of low rank coal particles in 2-ethyl hexanol solution was the shortest than that of low rank coal particles in dodecyl amine hydrochloride (DAH) and sodium dodecyle sulfate (SDS) solutions. Moreover, the maximum touching angle (θT) of low rank coal particles observed in 10−2 mol/L of 2-ethyl hexanol solution was about 80°, which was the greatest than that of low rank coal particles, about 39° in 10−3 mol/L of DAH and 35° in 10−4 mol/L of SDS solutions, respectively. Therefore, the sliding time results indicated that the hydrophobicity of low rank coal was enhanced by 2-ethyl hexanol and DAH and reduced by SDS. However, it was noted that the hydrophobicity of low rank coal was depressed when the DAH concentration increased to 10−2 mol/L. The flotation performances were consistent with the results of sliding time measurements. Therefore, effect of surfactants on the hydrophobicity of low rank coal particles can be characterized by sliding time measurements.
The attachment interaction in a flotation process is critical because it controls the recovery of mineral particles and is dominated by the interaction energy barrier between bubbles and solid ...particles. In this investigation, the surface properties of coal particles and oily bubbles were evaluated via the X-ray photoelectron spectroscopy (XPS) analysis, zeta potential measurement and induction time tests. The results proved that the classical Derjagin–Landau–Verwey–Overbeek (DLVO) theory did not adequately predict the flotation performances of oily bubble flotation. The attractive interaction or hydrophobic force induced by the hydrophobic force should be considered in the extended DLVO (EDLVO) theory. Throughout this paper, therefore, it is significant to consider the attractive interaction or hydrophobic force between low-rank coal particles and oily bubbles when comparing the advantages of the flotation response using air and oily bubbles.
Display omitted
•Both DLVO and extended DLVO theory were applied to calculate the energy barrier of oily bubble-coal particle interaction.•Long-flame coal concentrate with 83.33% yield was obtained from oily bubble flotation.•Hydrophobic force is the primary driving force for oily bubble–particle adhesion.
PDF
