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Quantitative characterization of the change in the cleat and pore structures and fractal dimensions in anthracite after electrochemical modification is crucial for better understanding of the modification effect. Thus, lump anthracite samples were electrochemically modified in our manufactured device with 0, 0.5, 1, and 2 V/cm potential gradients. The changes in heterogeneity and porosity after modification were tested and analyzed by mercury intrusion porosimetry (MIP) and fractal theory. The results indicated that the total volume of the pores increased after electrochemical treatment and continuously increased with increasing potential gradient during the treatment process. After modification, the number of pores or fractures with a pore size between 6 and 20 μm in coal after modification increases significantly. According to the intrusion pressure, three stages were defined as lower (

The wettability of gas and liquid on the coal surface is one of the fundamental factors that affect the depressurization process during the coalbed methane (CBM) extraction. The wettability of coal surface changed after electrochemical modification, leading to the change in methane adsorption/desorption and water movement in coal reservoirs. Thus, the CH4 adsorption amount, desorption ratio, and coal-water contact angle of raw and modified anthracite samples were measured and simulated. The mechanism of electrochemical modification was analyzed by functional groups, surface free energy, pore characteristics, interaction energies, and coal swelling. The experimental results showed that the saturated adsorption amount of methane decreased from 41.49 to 34.72 mL/g, and the simulation results showed that the saturated adsorption amount of methane decreased from 2.01 to 1.83 mmol/g. The coal-water contact angle also decreased from 81.9 to 68.6°. Electrochemical modification mainly affects the wettability of CH4 and H2O by changing the functional groups and pore structures of anthracite, and the influence on functional groups of coal surface is greater. This work provided a basis for enhancing CBM extraction by electrochemical modification.

In this work, we demonstrated a facile approach for fabrication of Au nanoflowers (Au NFs) using an amino-containing organosilane, 3-aminopropyltriethoxysilane (APTES), as a shape-directing agent. In this approach, the morphology of the Au particles evolved from sphere-like to flower-like with increasing the concentration of APTES, accompanied by a red shift in the localized surface plasmon resonance peak from 520 to 685 nm. It was identified that the addition of APTES is profitable to direct the preferential growth of the (111) plane of face-centered cubic gold and promote the formation of anisotropic Au NFs. The as-prepared Au NFs, with APTES on their surface, presented effective catalytic and surface-enhanced Raman scattering (SERS) performances, as evidenced by their applications in catalyzing the dimerization of p-aminothiophenol and monitoring the reaction process via in situ SERS analysis.

Based on the Turian-Yuan heterogeneous resistance model, the simulation results of three urban sludge pipelines with a volumetric concentration of 2.38, 3.94, and 5.39% were analyzed. The reasons for the large deviation of the simulation results under high Reynolds number conditions were also analyzed. The results showed that the deviation of the simulation was mainly caused by the difference between the sludge volumetric concentration (C V), the settlement resistance coefficient (C D), and the values of the two parameters in the Turian-Yuan heterogeneous resistance model. Consequently, it was necessary to optimize the index m 1 of C V and the index m 2 of C D. Taking mean square deviation as the objective function, using Matlab programming, the abovementioned two indexes were optimized by the simulated annealing algorithm. The optimized index m 1 of C V was 0.887, and the index m 2 of C D was -0.162. Hence, a modified Turian-Yuan heterogeneous resistance model was obtained. The model verified that the minimum value of the regression coefficient, R 2, of the simulated value reached 0.9701, proving that, the model can be used to simulate the heterogeneous resistance of urban sludge pipeline transportation.

Accelerating the drainage of water in coal reservoirs can significantly improve the extraction efficiency of coalbed methane (CBM). The movement of water with different pH values in anthracite was tested and analyzed. The results showed that the electro-osmotic flow velocity increased first and then slightly decreased with the increase of time up to 120 h. The electro-osmotic flow was markedly strengthened under a strong acid (pH 2) or strong alkaline (pH 13) environment, and the direction of electro-osmosis was reversed at a pH of 3-4. The changes in zeta potential, surface groups, and minerals in anthracite were tested to analyze the mechanism of electro-osmotic characteristics. The results obtained from this work will provide a basis for the process of drainage and depressurization during the CBM extraction.

The application of electrochemical modification for accelerating methane extraction in lean coal seams is limited due to the lack of experimental and theoretical research studies. Therefore, electrochemical modification with different electric potential gradient values was selected to modify lean coals in this study; meanwhile, the amount of methane adsorption and the methane desorption ratio were tested and analyzed. The results showed that the maximum amount of methane adsorption in coal samples decreased after electrochemical modification and the decrease in methane adsorption increased with an increase in electric potential gradient. The methane desorption ratio increased from 83.20% up to 87.84 and 86.90% at the anode and cathode zone, respectively, after electrochemical modification using a 4 V/cm electric potential gradient. A higher electric potential gradient performs better in the electrochemical modification. The mechanism of electrochemical modification using different electric potential gradients was revealed based on the measurements of Fourier transform infrared spectroscopy and liquid nitrogen adsorption. It is due to an increase in acid groups in coal molecular structure and the change of the specific surface area of coal after modification. The results obtained from this work contribute to the methane extraction via the electrochemical method in lean coal seams.

Carbon dots (CDs) as a kind of potential materials have drawn much attention due to their excellent optical properties. However, it is a challenge to fabricate new CDs-based thin films with intelligent responses. Herein, a kind of CDs with mechanical- and basic/acidic vapor-stimulated responsive behaviors was prepared using glutathione as a passivation agent via a one-pot solvothermal reaction. The high solubility of CDs enhanced by glutathione passivation was suitable for the preparation of CDs-based thin film. It is worth noting that the fluorescence of CDs-based poly(methyl methacrylate) (PMMA) thin film can be enhanced under grinding treatment, and it was also sensitive to the presence of ambient acids or bases. These CDs-based films with high stability and excellent mechanical and acid/base responses have great potentials for environmental monitoring.

This study aimed to reveal the flow and distribution lows of chemical oxygen demand (COD) and nitrate-nitrogen under different main anoxic stage oxidation-reduction potential (ORPan) conditions based on the analysis of material balance in each reaction stage of the modified university of cape town (MUCT) process, combined with the biochemical reaction principles of activated sludge. The rule of the carbon source saving effect was also clarified. The study adopted the programmable logic controller automatic control system and the feedback control structure using the inner circulation flow of nitrate as the controlled variable. The ORPan setting values of control parameters were -140, -125, -110, -95, -70, and -60 mV, respectively. The results showed that when the ORPan setting value was -95 mV, COD distribution ratios of phosphorus-accumulating bacteria reached the highest in the anaerobic stage and preanoxic stage, with the values of 51.74 and 7.70%, respectively. The COD was distributed between heterotrophic bacteria and denitrifying bacteria in the main anoxic stage, and the distribution ratios were 4.40 and 7.19%, respectively, when the ORPan setting value was -95 mV. The study also showed the distribution of nitrate-nitrogen between denitrifying bacteria and denitrifying phosphorus-accumulating bacteria in the main anoxic stage, and when ORPan increased from -140 to -60 mV, the distribution ratios of denitrifying phosphate-accumulating bacteria increased from 76.46 to 86.32%. When there was no denitrification and phosphorus absorption, the acetic acid dosage increased from 20.33 g/d at -140 mV to 24.76 g/d at -95 mV, and the carbon source saving rate increased from 23.19 to 26.56% under similar conditions. Therefore, in the MUCT process, the regulation of ORPan changed the material flow direction and mass quality distribution of COD and nitrate nitrogen. When ORPan set value was -95 mV, COD and nitrate-nitrogen got the best distribution and the carbon source saving effect was the most significant.

The application of cyclical microwave modification for accelerating the extraction of coalbed methane (CBM) from anthracite is limited. In this study, the apparent permeability of anthracite samples before and after each microwave treatment (three in total) for 120 s was measured by a self-built permeability-testing platform. Microcomputed tomography (micro-CT) technology and image-processing technology were employed to analyze the 3D micron-scale pore structures, especially the quantitative characterization of connected pores and throats. After modification, the average apparent permeability increased from 0.6 to 5.8 × 10-3 μm2. The generation, expansion, and connection of micron-scale pores and fractures became more obvious with each treatment. The total porosity increased from 3.5 to 6.2%, the connected porosity increased from 0.9 to 4.8%, and the porosity of isolated pores decreased from 2.5 to 1.4% after three cycles. The number, volume, and surface area of the connected pores as well as the number, radius, and surface area of the throats were significantly increased. In addition, the release of alkyl side chains from the anthracite surface reduced the capacity of the anthracite to adsorb CH4 and the decomposition of minerals promoted the development and connectivity of pores. As a result, the gas seepage channels have been greatly improved. This work provides a basis for micron-scale pore characterization after cyclical microwave modification and contributes to CBM extraction.