关键词：
Anaerobic digestion;Direct interspecies electron transfer;LCFAs;Methane;Palmitate;Rapeseed oil
摘要：
Due to long-chain fatty acids (LCFAs) and acidification, rapeseed oil as a typical lipid in kitchen waste is difficult to be biodegraded by anaerobic digestion. It has been reported that incorporation of some conductive materials into reactors treating complex organic matter could enhance reactor performance. In this study, the aim was to study this possibility of application of granular activated carbon (GAC) in anaerobic digestion of rapeseed oil. As expected, the GAC-amended reactor could significantly improve methane yield and reduce acidification. Besides, the GAC-amended broth could efficiently degrade palmitate into methane. Microbial community analysis showed that bacteria (Syntrophomonas) and methanogens (Methanosarcina) were greatly enriched on the GAC surface in GAC-amended system. These results, and the kwon of easy enrichment of Syntrophomonas on conductive materials or current-harvesting electrodes in methanogenic and/or electrogenic systems, suggest that Syntrophomonas could participate in direct interspecies electron transfer with Methanosarcina species, when GAC is available as an electron transfer mediator. Hence, the addition of GAC could efficiently, stably and environmentally enhance the methanogenic metabolism of rapeseed oil.
关键词：
energy consumption;graphene oxide;nanocomposite bricks;self-heating
摘要：
In cold climate regions, the energy associated with indoor heating constitutes a large portion of energy consumption. Increasing energy utilization efficiency is critically important for both economic and environmental reasons. Directly converting electrical energy to thermal energy using joule heating construction elements can save energy and investment to the water pipelines which have been extensively used for indoor heating in China. The fired brick has been extensively used to make pavements, walls and other masonry. Taking advantage of the high dispersion quality of graphene oxide (GO) in water, as well as the firing process used to make fired bricks, graphene nanocomposite bricks with excellent electrical properties and improved mechanical performance were prepared in China. The compressive strength of the bricks showed a substantial increase from 3.15 MPa to 7.21 MPa when GO concentration was 0.1 wt.%. Through applying 5 volts of electrical field within 5 minutes, the nanocomposites can be heated from room temperature to 60 degrees C, 110 degrees C and 160 degrees C for the nanocomposite bricks with graphene concentration of 3 wt.%, 4 wt.% and 5 wt.%, respectively, due to the extremely low percolation threshold (similar to 0.5 wt.%) and high conductivity (10 Omega<bold>cm at </bold>1 wt.%). The sheets were connected more tightly when the GO content was increased. The thermal efficiency can reach up to 88% based on the applied voltage, measured resistance and temperature rise curves.
期刊：
Heat Transfer Engineering,2020年41(8):723-738 ISSN：0145-7632
通讯作者：
Mobedi, Moghtada
作者机构：
[Wang, Chunyang; Mobedi, Moghtada; Kuwahara, Fujio; Nakayama, Akira] Shizuoka Univ, Fac Engn, Naka Ku, 3-5-1 Johoku, Hamamatsu, Shizuoka, Japan;[Nakayama, Akira] Wuhan Polytech Univ, Sch Civil Engn & Architecture, Wuhan, Hubei, Peoples R China
通讯机构：
[Mobedi, Moghtada] S;Shizuoka Univ, Fac Engn, Naka Ku, 3-5-1 Johoku, Hamamatsu, Shizuoka, Japan.
摘要：
A numerical study on melting of an ice block assisted by aluminum metal foam and placed in a channel is performed. The same problem is also solved for a clear ice block without assisting metal foam. The dimensional and dimensionless forms of the governing equations are presented. The continuity, momentum, and energy equations for the entire region are solved to obtain the velocity, pressure, and temperature distributions. The influence of three dimensionless parameters as Reynolds number, Stefan number, and aspect ratio on heat and fluid flow mechanism and total melting period is investigated. It is found that the use of metal foam in the ice block has negligible effect on the heat transfer enhancement in some studied cases. The highest effect of metal foam on melting period is observed when the thermal interaction between the block and flowing fluid is weak. The maximum reduction in the specific dimensionless total melting period is found around 38% because of the metal foam. For the cases with strong thermal interaction between the block and flowing fluid in the channel, the use of metal foam does not have considerable effect on the acceleration of phase change. Due to the limited studies on the solid/liquid phase change under forced convection in a channel, the results of present study can also be used as benchmark solution for validation of future studies.
摘要：
VOCs are the major harmful pollutants released from MSW landfills, which are toxicity to human health. In order to in-situ biodegradation of VOCs released from landfill, two novel laboratory-scale biocovers, including waste-char obtained from MSW pyrolysis (WC), and sewage sludge modified the WC (SWC), are used to degradate VOCs. The removal performances of VOCs as well as the bacterial community in the WC and SWC are investigated in a simulated landfill systems with the contrast experiment of a landfill cover soil (LCS) for 60 days. Meanwhile, the adsorption-biodegradation of VOCs model compounds over the LCS, WC, and SWC are also tested in fixed-bed adsorption reactor and in-situ FTIR. The VOCs removal efficiencies by the SWC are maintained above 85% for a long-term, much higher than that of the LCS and WC. The higher removal efficiencies and long-term stability for VOCs degradation in SWC are attributed to a strongly positive synergistic between adsorption and biodegradation that the gaseous VOCs released from MSW is effectively adsorbed by the SWC due to its higher VOCs adsorption capacity, and then the adsorbed-VOCs is converted into CO(2 )and H2O by the microorganisms that consuming the adsorbed-VOCs as energy and carbon sources. Subsequently, the decrease of the adsorbed-VOCs in SWC would also promote the transformation of the gaseous VOCs into the adsorbed VOCs and accelerate the growth of microorganisms by taking the adsorbed-VOCs as the energy and carbon source, resulted in a higher adsorption rate and degradation rate for VOCs. (C) 2020 Published by Elsevier Ltd.
摘要：
Floor radiant heating embedded phase change materials (PCMs) are a prospective field owing to its highly efficient energy-saving effect and comfortable thermal environment. In this work, using a non-eutectic mixture comprised of NaAc center dot 3H(2)O (main PCM) and glycine (temperature regulator) as PCM, and expanded graphite (EG) as supporting material, a novel composite PCM with high thermal performance used in the heat exchanger for the floor radiant heating was developed. The composition of the composite PCM was optimized, and its properties were studied. The results showed that the mixture containing 12% glycine was favorable due to its suitable phase change temperature (48.62 degrees C) and high phase change enthalpy (258.5 kJ.kg(-1)). The addition of 12% EG into the mixture could enhance thermal conductivity and prevent leakage of the mixture simultaneously. The resulting composite PCM melted at 47.14 degrees C with phase change enthalpy of 214.7 kJ.kg(-1), supercooling degree of 1.49 degrees C and thermal conductivity of 6.400 W m(-1) K-1. The composite PCM also presented a good thermal reliability. Hence, the as-prepared composite PCM would be of great promise for use in the heat exchanger for the floor radiant heating. Besides, the present work is expected to provide a new pathway for exploring new types of PCMs. (C) 2020 Elsevier B.V. All rights reserved.
作者机构：
[Li Cong; Zhang Rong-tang; Liu Jie-sheng] Wuhan Polytech Univ, Sch Civil Engn & Architecture, Wuhan 430023, Hube, Peoples R China.;[Lu Bo; Li Cong; Zeng Ping; Zhu Jie-bing; Jiang Yu-zhou; Wang Bing] Changjiang River Sci Res Inst, Key Lab Geotech Mech & Engn, Minist Water Resources, Wuhan 430010, Peoples R China.;[Liu Zhi-jun] Guangzhou Baiyun Int Airport Co Ltd, Guangzhou 510406, Peoples R China.
通讯机构：
[Zhu Jie-bing] C;Changjiang River Sci Res Inst, Key Lab Geotech Mech & Engn, Minist Water Resources, Wuhan 430010, Peoples R China.
关键词：
Model test;Bedding slope;Prestressed anchorage;Corrosion;Electrochemical measurement
摘要：
The long-term stability of a prestressed anchored slope might be influenced by the durability of the anchorage structure. To understand long-term stability of anchored rock slopes, the research presented herein evaluated the performance evolution of a prestressed anchored bedding slope system in a corrosive environment by model test. The corrosion process in a prestressed anchor bar was monitored in terms of its open-circuit potential (OCP), corrosion current density (CCD), and electrochemical impedance spectroscopy (EIS). The stability of the prestressed anchored slope was evaluated by monitoring changes in anchorage force and displacements. The experimental results show that prestress and oxygen could reduce the corrosion resistance of the anchor bar, and anchor bars in a chloride-rich environment are very susceptible to corrosion. Prestressed tendons in a corrosive environment suffer a loss of anchorage force, the prestress decreases rapidly after locking, and the rate thereof decreases until stabilising; in the later stage, corrosion leads to the reduction of the cross-sectional area of the steel bar which may cause the reduction in anchorage force again. Anchorage force controls the deformation and stability of the anchored slope, the prestress loss caused by later corrosion may lead to an increased rate of displacement and stability degradation of the prestressed anchored rock slope.
摘要：
This study focused on the permeability and structural evolution of impeded soil layers in landfill. A series of laboratory tests including a permeability test, X-ray diffraction, nuclear magnetic resonance, scanning electron microscopy, and laser particle size tests were conducted to analyze the permeability and microstructure characteristics of undisturbed silty clay polluted by landfill leachate. The hydraulic conductivities increased with time in the first 108 h. After 108 h, the hydraulic conductivities of undisturbed silty clay polluted by landfill leachate decreased. After 205 h, the changes in the hydraulic conductivity stabilized, and the hydraulic conductivity decreased with the increase of the concentration of leachate. The volume fractions of inter-particle and intra-aggregate pores were much higher than those of other pores. The optimal radius decreased as the concentration of leachate increased. The blockage of the pore channel and weakened permeability was caused by solid matter interception by the porous medium. As the height of the specimen increased, the volume fraction of coarse grain changed rapidly and sharply, and the volume fraction of fine grain changed slowly. The average particle size increased with increased specimen height and decreased as the leachate concentration increased. A comprehensive structural parameter (zeta) of undisturbed silty clay polluted by landfill leachate was obtained based on the test results. The equation of comprehensive structural parameter zeta of undisturbed silty clay polluted by leachate was established. These results can provide fundamental data for evaluating the stability of the underlying stratum of landfill sites.
摘要：
Salinity stress during anaerobic digestion is known to cause extensive changes in biogas production and microbial community structure. Thus, our study sought to characterize the adaptation response of bacteria when challenged with increased salinity. Firstly, experiments were conducted at eight salinity levels at a constant kitchen waste/inoculum ratio (K/I = 1.0), which indicated that the effect of salinity on anaerobic digestion was strictly dosage-dependent. Then, kitchen waste anaerobic digestion was conducted for 70 days at five increasing salinity levels (1.0, 2.0, 4.0, 8.0, and 16.0 g NaCl/g). Furthermore, six samples taken at the end of each salinity level acclimation phase were analyzed by high-throughput sequencing, which illustrated that Euryarchaeota, Synergistetes, Firmicutes, and Bacteroidetes were dominance at phylum level. Moreover, the proportion of Methanosaeta as major genus among Euryarchaeota was 16.46% after being acclimated 70 days of NaCl acclimation, which was higher than its proportions at the initial sample (22.08%). Methanosarcina were also enriched after acclimation. Therefore, Methanosaeta and Methanosarcina could both potentially adapt to high- salinity environments. (C) 2019, The Society for Biotechnology, Japan. All rights reserved.
期刊：
Bulletin of Engineering Geology and the Environment,2019年78(6):4611-4622 ISSN：1435-9529
通讯作者：
Lu, Haijun
作者机构：
[Lu, Haijun; Xu, Shicheng; Li, Jixiang] Wuhan Polytech Univ, Sch Civil Engn & Architecture, Wuhan 430023, Hubei, Peoples R China.;[Lu, Haijun] Chinese Acad Sci, Inst Rock & Soil Mech, State Key Lab Geomech & Geotech Engn, Wuhan 430071, Peoples R China.;[Liu, Junzhu] Beijing Geo & Inv Engn Inst, Beijing 100083, Peoples R China.
通讯机构：
[Lu, Haijun] W;[Lu, Haijun] C;Wuhan Polytech Univ, Sch Civil Engn & Architecture, Wuhan 430023, Hubei, Peoples R China.;Chinese Acad Sci, Inst Rock & Soil Mech, State Key Lab Geomech & Geotech Engn, Wuhan 430071, Peoples R China.
关键词：
Structured clay;Landfill leachate;Triaxial shear test;Microstructure;Particle distribution
摘要：
City solid waste stock has exceeded 8 billion tons in China, and the output and coverage area of solid waste are increasing daily. Landfill leachate can be generated during biodegradation of disposed and stored solid waste. Leachate contains high concentrations of organic mixtures and heavy metal ions. Natural undisturbed soil has high anti-seepage capacity and its permeability coefficient is less than 1 x 10(-7) cm/s in underlying stratum, which can delay leachate contamination of the environment surrounding a landfill site. However, undisturbed soil exhibits certain structural characteristics. After long-term leachate corrosion, leachate leakage will inevitably influence the stability of stratum underlying a landfill. In this study, the mechanical characteristics of undisturbed clay under the actions of landfill leachate and stress were analyzed via a consolidated-undrained triaxial shear test. Comprehensive microstructure laboratory tests, including X-ray diffraction, scanning electron microscopy, and laser particle size tests, were performed to determine at different times the microstructure of undisturbed clay due to corrosion by landfill leachate. Experimental results indicate the strength and microstructural evolution of structured clay under the actions of landfill leachate and stress. The research results are helpful for evaluating the safety and predicting the stability of a landfill's underlying stratum.
关键词：
dynamic water grouting;water-soluble polyurethane slurry;hydroxypropyl methyl cellulose;chemical modification;diffusion radius
摘要：
In underground project, water inrush disaster often occurs, resulting in a large number of casualties and economic losses. To solve these problems, grouting is one of the main techniques for controlling water inrush. At present, the research results on the treatment of water inrush by grouting are based on anhydrous or hydrostatic grouting. However, the study of dynamic water grouting is relatively few and the grouting materials are a little bit. In this paper, water-soluble polyurethane was selected as grouting material, modified by adding hydroxypropyl methyl cellulose, and the bond strength and microstructure change before and after modification are studied via bond strength experiment and microscopic observation. In addition, the WPU (water-soluble polyurethane) diffusion regularity of dynamic water grouting is studied by indoor flat grouting test. The research also adopts the Bingham fluid model according to the slurry characteristics to derive the grouting diffusion radius. The results show that the compactness of HPMC (hydroxypropyl methyl cellulose)-WPU is improved, the heterogeneity is reduced by 50.4%, and the bonding strength is increased by 153%. Therefore, the anti-scour ability of the HPMC-WPU is enhanced. The deviation of the WPU in the X-axis diffusion radius is 7.7 cm, and the HPMC-WPU is 4.39 cm. What's more, the formula of grouting diffusion radius is derived. By comparing the formula with experiment results, the deviation is less than 15%, therefore, the formula has the significance of guiding engineering practice.
期刊：
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY,2019年19(8):4465-4473 ISSN：1533-4880
通讯作者：
Shi, Xianming
作者机构：
[Gong, Jing; Li, Zhipeng; Zhang, Rongtang] Wuhan Polytech Univ, Sch Civil Engn & Architecture, Wuhan 430023, Hubei, Peoples R China.;[Gong, Jing] Wuchang Univ Technol, Coll Urban Construct, Wuhan 430223, Hubei, Peoples R China.;[Li, Jianfen] Wuhan Polytech Univ, Sch Chem Engn & Environm, Wuhan 430023, Hubei, Peoples R China.;[Shi, Xianming] Washington State Univ, Dept Civil & Environm Engn, Lab Adv & Sustainable Cementitious Mat, Pullman, WA 99164 USA.
通讯机构：
[Shi, Xianming] W;Washington State Univ, Dept Civil & Environm Engn, Lab Adv & Sustainable Cementitious Mat, Pullman, WA 99164 USA.
关键词：
High Volume Fly Ash;Polyethylene Microfiber;Nano-Montmorillonite;Interface;EDX;Microhardness
摘要：
Foamed cement-based materials have attracted much attention as a new type of thermal insulation materials (TIMs) that may offer a sustainable solution to the built environments. This laboratory study explores the combined use of nano-montmorillonite and polyethylene microfiber in foamed paste with high volume fly ash (HVFA) binder. A total of 16 foamed HVFA paste mixtures were fabricated which consisted of 70% Class F fly ash, 30% Portland cement, 2% sodium alpha-olefin sulfonate, 0.38% Na(3)PO(4), and 2% nano-montmorillonite. The dosage and type of polyethylene microfibers (90 mum in diameter) were explored in the present study, with six dosages (0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% by volume) and three lengths (3 mm, 6 mm, and 9 mm) tested. Based on the experimental results, the highest 28-day rupture strength (1.51 MPa) was achieved with the use of 3-mm long PE microfibers at 0.4 vol.%. Synergistic utilization of nMMT and microfibers exhibited a great influence on the dry density and water absorption of the foamed paste. The SEM micrographs illustrated the multiple mechanisms by which the microfibers serve to reduce shrinkage-induced cracking of the foamed paste. Energy-dispersive X-ray spectroscopy was employed to obtain the contents of Ca, Si, Al, S and mole ratios of Ca/Si, Ca/(Si + Al), S/Ca, and Al/Si in the hardened pastes, which reveal the difference in hydration products near or away from the nMMT-pretreated polyethylene microfibers. The results of microhardness test were also used to elucidate such nano-/micro-synergistic effects, which improved the bonding between microfibers and foamed paste matrix. A mechanism was proposed to explain the role of various admixtures and the balanced performance of such inorganic TIMs.
