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Table of Content
05 June 2023, Volume 74 Issue 6
    Reviews and monographs
    Research progress in downer fluidized bed reactor for biomass fast pyrolysis
    Zhenghao YANG, Zhen HE, Yulong CHANG, Ziheng JIN, Xia JIANG
    2023, 74(6):  2249-2263.  doi:10.11949/0438-1157.20230170
    Abstract ( 416 )   HTML ( 27)   PDF (2291KB) ( 253 )  
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    Under the goal of carbon neutrality, the future development path is to change from the raw material system of fossil energy to the raw material system of renewable energy. As an important substitute for fossil resources, biomass is the only renewable carbon resource that can replace fossil resources on a large scale. Fast pyrolysis of biomass is an important way to convert biomass resources into liquid fuels, and its core technology is the reactor. The downer circulating fluidized bed reactor has the advantages of short product residence time and near-plug flow performance, and has broad application prospects in fast pyrolysis of biomass. In this paper, the characteristics of fluidized bed reactor and the research status of pilot and demonstration/commercial units are introduced. The characteristics, structure, classification and hydromechanical properties of downer reactor are summarized in detail, and the bottleneck problems in the process of downer reactor scale-up and the direction of further research are analyzed, which can provide reference for promoting the industrial application of downer reactor in fast pyrolysis of biomass.

    Performance regulation strategies of Ru-based nitrogen reduction electrocatalysts
    Tan ZHANG, Guang LIU, Jinping LI, Yuhan SUN
    2023, 74(6):  2264-2280.  doi:10.11949/0438-1157.20230048
    Abstract ( 323 )   HTML ( 25)   PDF (3457KB) ( 241 )  
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    Ammonia is an important chemical and ideal energy vector. Artificial ammonia synthesis through the Haber-Bosch (H-B) process is energy-intensive. In contrast, ammonia is generated from N2 and H2O under mild conditions through the electrocatalytic ammonia synthesis. Ru-based catalyst performs superior activities during the nitrogen reduction reaction (NRR), which has attracted extensive attention. However, its development is limited owing to its scarcity. Therefore, the NRR reaction mechanisms are briefly outlined and a systematic summary of Ru-based electrocatalysts for ammonia synthesis is introduced firstly. Subsequently, it is methodically discussed how the strategies for performance enhancement (structural optimization, surface/interface engineering, defect engineering) of catalysts regulate the active sites or electronic structure and then promote the activity of catalysts. Finally, the remaining challenges of Ru-based electrocatalysts in future are highlighted. This review aims to achieve the usage of the Ru metal effectively through the performance-improving strategies of Ru-based electrocatalysts and provides the theory guidance for the design of the other NRR catalysts.

    Research progress in preparation of lignonanocellulose by acid hydrotropes and their functional applications
    Maolin DONG, Lidong CHEN, Liulian HUANG, Weibing WU, Hongqi DAI, Huiyang BIAN
    2023, 74(6):  2281-2295.  doi:10.11949/0438-1157.20230182
    Abstract ( 189 )   HTML ( 12)   PDF (5977KB) ( 168 )  
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    Lignonanocellulose has received extensive attention in various fields due to its simple preparation process, environmental friendliness, and high cost-effectiveness. Its production and application has become research hotspots in related fields. However, the aggregated structure of the lignocellulose and the complex chemical bonding (ether bond, ester bond, etc) between their components form an anti-depolymerisation barrier, which needs to be broken by pretreatment. Acid hydrotropes system has the advantages of high dissolution selectivity, easy separation of products, and recyclability, which is an important pretreatment method for the preparation and high value utilization of lignonanocellulose. This paper firstly introduces the concept and mechanism of acidic hydrotropes, then reviews the preparation methods and properties of lignocellulose with acidic hydrotropes, discusses the progress of functional application of lignocellulose, and finally summarizes the development of acidic hydrotropes. The deficiencies of the system are discussed, and the future research direction is prospected.

    Research progress on the water resistance of degradable cellulose-based materials
    Zhangning CUI, Zixuan HU, Lei WU, Jun ZHOU, Gan YE, Tiantian LIU, Qiuli ZHANG, Yonghui SONG
    2023, 74(6):  2296-2307.  doi:10.11949/0438-1157.20230316
    Abstract ( 220 )   HTML ( 9)   PDF (2415KB) ( 200 )  
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    The preparation of plastic substitutes from biomass resources has become one of the most attractive research topics at present. Cellulose, a polymer widely found in biomass, has been used as a precursor of high-value materials due to its degradability, sustainability, and good mechanical properties. However, the rich hydroxyl structure in cellulose enhances its hydrophilicity, leading to the softening of cellulose-based materials after water absorption, thus their mechanical properties are seriously affected. On the premise of retaining the environment-friendly properties of cellulose, the improvement of the water resistance of cellulose-based materials is to increase their water stability and mechanical properties in high humidity environments, thereby broadening the practical application range of cellulose-based materials and making them an excellent candidate for petroleum and making them become the excellent alternatives to petroleum-based or coal-based plastics. Based on the analysis of structure and properties of cellulose, the problem of poor water resistance of cellulose-based materials was raised firstly, and then the performance indicators and industry requirements of the water resistance for cellulose-based materials were introduced. Three optimization methods (coating hydrophobic coatings, preparing composite materials, and adding additives) for the improvement of the water resistance of cellulose-based materials were emphasized. At last, the water resistance of cellulose-based materials was summarized and prospected, and the problems and challenges in their practical optimization were pointed out.

    Research progress of conductive thin film materials
    Bin CAI, Xiaolin ZHANG, Qian LUO, Jiangtao DANG, Liyuan ZUO, Xinmei LIU
    2023, 74(6):  2308-2321.  doi:10.11949/0438-1157.20230366
    Abstract ( 402 )   HTML ( 22)   PDF (1672KB) ( 378 )  
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    Due to the advantages of high conductivity, high transmittance and bendability, conductive film materials are widely used in photoelectric conversion, electrothermal conversion, electromagnetic conversion and other fields. Currently, conductive fillers for thin film materials mainly include metals and their compounds, carbon-based materials and conductive polymers. In general, it is difficult for a single conductive material to adapt to the dual needs of conductivity and stability. Composite conductive films prepared by doping or assembling two or more conductive materials show better conductivity and environmental stability. Surface modification is a powerful way to improve the bonding strength of conductive materials to substrates. This paper summarizes the characteristics, advantages and disadvantages of various conductive thin film materials focusing on the conductive properties, and puts forward suggestions for improving the conductivity and stability of conductive thin film materials, providing reference for the research of conductive thin film materials.

    Research progress in the application of lignin-based carbon fiber composite materials in energy storage components
    Jing LI, Conghao SHEN, Daliang GUO, Jing LI, Lizheng SHA, Xin TONG
    2023, 74(6):  2322-2334.  doi:10.11949/0438-1157.20230208
    Abstract ( 228 )   HTML ( 11)   PDF (3753KB) ( 260 )  
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    Based on the advantages of low cost, renewability, abundant sources, simple preparation process and controllable structure of lignin natural polymer, it has been used to prepare carbon fiber and applied to energy storage components such as supercapacitors and rechargeable batteries. The advantages of fast charge and discharge speed, high energy density and long cycle life have been confirmed and applied. The process technology and fiber properties of lignin-based carbon fibers prepared by spinning method in recent years were systematically reviewed. Based on the structural design diversity of lignin-based carbon fibers, the different electrochemical properties of different lignin-based carbon fibers as electrode materials for supercapacitors and rechargeable batteries were summarized. In addition, an overview of the development prospects and challenges of lignin-based carbon fiber composites was provided to think for the next step of research and development of lignin-based carbon fiber composites.

    Fluid dynamics and transport phenomena
    Study on the pressure pulsation characteristics in jet influence zone of riser
    Zhihang ZHENG, Junnan MA, Zihan YAN, Chunxi LU
    2023, 74(6):  2335-2350.  doi:10.11949/0438-1157.20230418
    Abstract ( 153 )   HTML ( 8)   PDF (4357KB) ( 115 )  
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    In the riser large-scale cold mode experiments, the pressure pulsations in the jet influence zone are collected. To make a comparison, effects of upward and downward jets are investigated. The pressure pulsation distribution and gas-solid interaction pattern in the jet influence zone are obtained. On this basis, the connection between pressure pulsation characteristics and jet velocity in the influence zone is established by using wavelet analysis. The results show that the downward inclined jet makes the overall value of the pressure pulsation standard deviation increase by 30% in the riser comparing with the upward inclined jet. At the same time, by introducing the downward inclined jet, the axial and radial variation gradients are reduced, so that the intensity of gas-solid mixing process increases. In wavelet analysis, as the jet velocity increases, the wavelet energy value at each scale in the region near the nozzle inlet decreases by 25% when the jet inclines upward. While in the downward inclined jet influence zone, the wavelet energy value increases by 29%, of which ED4 and EA8 accounted for the largest energy. Generally, it is found that the downward inclined jet can effectively increase the intensity of high-frequency pressure pulsation in the jet influence zone, which is conducive to improving the gas-solid contact effect.

    Effect of agglomerate structure on drag force by numerical simulation
    Daoyin LIU, Bingqi CHEN, Zuyang ZHANG, Yan WU
    2023, 74(6):  2351-2362.  doi:10.11949/0438-1157.20230291
    Abstract ( 203 )   HTML ( 15)   PDF (7069KB) ( 95 )  
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    Viscous particles mostly exist in the gas-solid two-phase system in the form of agglomerates, and the drag force exerted by the fluid on the agglomerates plays a crucial role in the two-phase flow and heat and mass transfer. However, the irregular and porous structure of the agglomerate result in complexities of the drag characteristics. In this study, a series of fractal-like agglomerates are generated by discrete element method (DEM) with a cohesive contact model, and the flow field including the external and interior flow through the agglomerate is resolved by computational fluid dynamic (CFD). The effect of agglomerate structure on drag characteristics at low Reynolds number flows (Re=0.1—10) is investigated. The simulation results show that the flow through the agglomerate is greatly influenced by the agglomerate structure. The permeability of agglomerate is enhanced by increasing agglomerate porosity, resulting in an increase of the contact surface between the fluid and agglomerate, thus increasing the drag force. The drag coefficient for agglomerates with different structures are calculated, which indicates that the drag coefficient of non-spherical agglomerates is influenced not only by structure parameters (size, porosity, fractal dimension) but also by the orientation between the agglomerate and gas flow direction. Finally, a correlation of the drag force coefficients based on the current simulations is proposed for porous agglomerates with fractal-like shapes.

    Study and prediction of flow field in the annular region of geometrically similar turbo air classifier
    Yuan YU, Weiwei CHEN, Junjie FU, Jiaxiang LIU, Zhiwei JIAO
    2023, 74(6):  2363-2373.  doi:10.11949/0438-1157.20230301
    Abstract ( 144 )   HTML ( 7)   PDF (2708KB) ( 226 )  
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    In order to explore the distribution characteristics of the flow field in the annular region of the geometrically similar turbo air classifier, the turbo air classifier models of different sizes were established, the geometric parameters of the key structures were extracted, and the influence of the size scale factor on the flow field distribution in the annular region of the classifier was analyzed through numerical simulation. The numerical simulation results show that under the same air inlet velocity, the tangential velocity distribution in the annular region of the geometrically similar classifier model presents the distribution of quasi-free vortices. With the increase of model size, the area weighted average tangential velocity of cylinder surface in the annular region increases, and the overall distribution of tangential velocity in the annular region is non-uniform. If the tangential velocities are similar between the inner and outer edges of the rotor cage, the tangential velocity fluctuation is small in the annular region. The radial velocity distribution in the annular region of the geometrically similar classifier model conforms to the law of point sink. Except for the large difference in the radial velocity values near the outer edge of the rotor cage, the area weighted average radial velocity of the cylinder surface in the annular region does not change with the scale factor of the classifier. The numerical simulation data of geometrically similar classifier models are used as the training samples to fit the prediction formula of the area weighted average tangential velocity and radial velocity of the cylinder surface in the annular region of the classifier, and the test and verify sample classifier model is established to test the prediction formulas. The maximum errors between the predicted and simulated area weighted average tangential velocity and radial velocity of the cylinder surface are 3.5% and 1.8%, respectively. In addition, by analyzing the kinematic similarity and dynamic similarity of the flow field in the annular region of the geometrically similar turbo air classifier models, it is concluded that the flow fields of geometrically similar classifier models have similarity.

    Study on flow characteristics of nanoparticles in a rotating fluidized bed based on DEM method
    Juhui CHEN, Qian ZHANG, Lingfeng SHU, Dan LI, Xin XU, Xiaogang LIU, Chenxi ZHAO, Xifeng CAO
    2023, 74(6):  2374-2381.  doi:10.11949/0438-1157.20230312
    Abstract ( 180 )   HTML ( 14)   PDF (1754KB) ( 178 )  
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    In this paper, based on the DEM method, the flow of two kinds of nanoparticles with different particle sizes in the rotating fluidized bed was simulated by using MFIX software.Comparing the simulation results with previous experimental results, it is found that the results are in good agreement, which verifies the accuracy and reliability of the rotating fluidized bed model. The movement process of nanoparticles in a rotating fluidized bed is numerically simulated. Adding the van der Waals force, the distribution of nanoparticles, the velocity vector distribution of nanoparticles and the pressure drop of the nanoparticle bed layer changing with gas velocity under different centrifugal accelerations were simulated. The results indicate that a small fraction of nanoparticles become entrained in the upper region of the rotating fluidized bed, while the majority of particles follow the movement of the bed. When the nanoparticles reach an angle of approximately 60°, they experience a downward motion followed by repeated cycles due to particle accumulation. The bed pressure drop in the rotating fluidized bed increases with increasing centrifugal acceleration and gas velocity. Under the same conditions, the bed pressure drop for TiO2 particles is higher than that of Al2O3 particles, and Al2O3 particles reach a steady state earlier compared to TiO2 particles.

    Heat and mass transfer and energy consumption for microwave drying of coal slime
    Guangyu WANG, Kai ZHANG, Kaihua ZHANG, Dongke ZHANG
    2023, 74(6):  2382-2390.  doi:10.11949/0438-1157.20230122
    Abstract ( 142 )   HTML ( 4)   PDF (2498KB) ( 137 )  
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    The basic characteristics of the coal slime drying process and its heat and mass transfer characteristics were investigated by microwave heating method, and the basic laws of dynamics and energy consumption changes in different stages were expounded. The results show that the process of microwave drying of coal slime may be divided into three stages, i.e., preheating stage, constant-rate drying stage and decreasing-rate drying stage. The free water within coal slim is removed mainly in the both preheating stage and constant-rate drying stage, whilst the bound water is removed in the decreasing-rate drying stage. The linear model and modified Page Ⅰ model can be used to describe the corresponding kinetic processes in the constant-rate and decreasing-rate stage, respectively. Furthermore, the apparent activation energy of the selected sample in the decreasing-rate stage is obtained as 3.23 W/g. The energy consumption in the constant-rate drying stage ranges from 2.94 kJ/g to 5.90 kJ/g, which is significantly lower than that in the preheating or decreasing-rate drying stage. The energy consumption is decreased gradually with the increase of microwave power ranging from 500 W to 800 W or initial mass from 150 g to 300 g.

    Analysis and calculation of void fraction of gas-liquid two-phase flow in vertical riser under fluctuating vibration
    Qichao LIU, Yunlong ZHOU, Cong CHEN
    2023, 74(6):  2391-2403.  doi:10.11949/0438-1157.20230300
    Abstract ( 121 )   HTML ( 3)   PDF (2021KB) ( 93 )  
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    Accurate prediction of void fraction of gas-liquid two-phase flow under undulating vibration is of great significance to the safe and stable operation of floating nuclear power plants. The void fraction characteristics of gas-liquid two-phase flow in vertical riser under different vibration and flow conditions were studied experimentally. The results show that the fluctuation vibration has a significant effect on the void fraction in bubbly flow, however it has a weak effect on slug flow, churn flow and annular flow. Generally speaking, the undulating vibration leads to an increase in the void fraction of the bubbly flow and a decrease in the void fraction of the other three flow patterns. The void fraction calculation model in static pipeline is evaluated. It is found that the existing void fraction calculation model is suitable for the calculation of void fraction under fluctuating vibration, but the prediction error of void fraction under bubbly flow and slug flow is relatively large. Considering the influence of vibration, the Froude number of liquid phase is introduced, and the calculation formula of void fraction considering flow pattern is established, which significantly improves the prediction accuracy of void fraction under fluctuating vibration.

    Gas-liquid mass transfer and reaction characteristics of SNCR denitration in CFB coal-fired unit
    Yuanyuan ZHANG, Jiangyuan QU, Xinxin SU, Jing YANG, Kai ZHANG
    2023, 74(6):  2404-2415.  doi:10.11949/0438-1157.20230084
    Abstract ( 149 )   HTML ( 6)   PDF (4540KB) ( 100 )  
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    The CFD simulation method was used to predict the reductant droplet evaporation, flue gas mixing and reaction characteristics in the SNCR denitrification process of a 300 MW circulating fluidized bed unit. The numerical results show that the flue gas is attached to the wall of the cyclone separator and forms a double-vortex structure including a quasi-free vortex and a quasi-forced vortex, which makes the droplets start to evaporate at a constant temperature after contacting the flue gas for about 0.01 s and enhances the mixing behavior between flue gas and gaseous reducing agent. NH3 is mainly distributed above the cone of cyclone separator when aqueous ammonia is used as the reductant, whilst both HNCO and NH3 are produced with the consumption rate of HNCO higher than that of NH3 when aqueous urea is as the reductant. Although the concentration distribution of NH3 is similar, the denitration efficiency is about 79.5% for aqueous ammonia compared to about 76.5% for aqueous urea under both the same flue gas temperature and ammonia nitrogen molar ratio. The reaction rate of NH3 and NO is increased and the denitration efficiency increases from 19.7% to 81.0% when the temperature is increased from 1023 K to 1173 K. However, the oxidation rate of NH3 itself is increased significantly resulting in a reduction of denitration efficiency to 17.4% when the temperature is further increased from 1173 K to 1323 K. The denitration efficiency is increased with the increase of NH3/NO mole ratio (NSR), but the utilization efficiency of reductant is decreased which leads to the increase of ammonia slip. Considering the SNCR denitration efficiency together with ammonia escape rate of the CFB boiler unit used in this study, the NSR of 1.25—1.50 can meet the ultra-low emission standard of NO x emission not higher than 50 mg/m3.

    Catalysis, kinetics and reactors
    Reaction engineering calculation of deactivation kinetics for ethylene catalytic oxidation over irregular-shaped catalysts
    Jipeng ZHOU, Wenjun HE, Tao LI
    2023, 74(6):  2416-2426.  doi:10.11949/0438-1157.20230168
    Abstract ( 170 )   HTML ( 12)   PDF (2665KB) ( 116 )  
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    For the reaction of ethylene catalytic oxidation to ethylene oxide, the finite element method (FEM) is employed to solve the deactivation kinetics and reaction-mass transfer-heat transfer model simultaneously. The convergence of the model and accuracy of calculation results are very well. After the catalyst particles reacted for 16 months, the activity coefficients of the main and side reactions decreased significantly, and the deactivation rate of the side reactions was greater than that of the main reactions. With the deactivation of catalysts, the first kind deactivation internal effectiveness factor increases with time, and the second kind deactivation internal effectiveness factor decreases at first and then increases slightly. It is shown by quantitative calculation that the internal diffusion resistance can “delay” the reduction of apparent reaction rate caused by catalyst deactivation. For ethylene catalytic oxidation system with severe internal diffusion limitations, the apparent deactivation rate is only 50.8% of intrinsic deactivation value. The parameter values of the deactivation kinetic equations by experiments are strongly influenced by internal diffusion, and a distinction must be made between intrinsic and macroscopic deactivation kinetics. When the activity factors are reduced to a certain value, the reaction temperature can be increased to ensure the reaction at a high range. This model can be applied to guide reactor design and optimize the operation parameters with deactivation process.

    Effect of Mg content on isobutane dehydrogenation properties over nanosheets supported Pt-In catalysts
    Xiqing ZHANG, Yanting WANG, Yanhong XU, Shuling CHANG, Tingting SUN, Ding XUE, Lihong ZHANG
    2023, 74(6):  2427-2435.  doi:10.11949/0438-1157.20230258
    Abstract ( 125 )   HTML ( 4)   PDF (1247KB) ( 77 )  
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    A series of hydrotalcite nanosheets with different Mg content were in-situ constructed on the surface of Al2O3 support by one-step synthesis method. And promoter In and active component Pt were introduced in the nanosheets by consecutive impregnation-reconstruction method. Furthermore, the supported Pt-In bimetallic catalysts PtIn/HTR-x (x = 0.05, 0.1, 0.15, 0.2 mol·L-1) were prepared by calcination and reduction. The relationship between the structure, physical and chemical properties of the catalyst and its precursor and the direct dehydrogenation performance of isobutane was explored. The results show that the Mg2+ concentrations determine the nanosheets thickness, which affects the structure, reducibility, surface chemical states, and surface acidity and dehydrogenation properties of these catalysts. The catalyst with Mg2+ concentration of 0.15 mol·L-1 exhibits the optimum dehydrogenation performance, of which the isobutene yield reaches 58%. The excellent activity, selectivity and stability of PtIn/HTR-0.15 are attributed to the maximum specific surface area, strong metal-support interaction and high surface In3+/In0 atomic ratio, and the good anti-carbon deposition performance is related to the low concentration and weak strength of surface strong acid sites.

    Corrosion micro-nano scale kinetics model development and application in non-conventional supercritical boilers
    Yanhui LI, Shaoming DING, Zhouyang BAI, Yinan ZHANG, Zhihong YU, Limei XING, Pengfei GAO, Yongzhen WANG
    2023, 74(6):  2436-2446.  doi:10.11949/0438-1157.20230440
    Abstract ( 154 )   HTML ( 6)   PDF (1335KB) ( 413 )  
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    Deep and frequent peak shaving supercritical/ultra-supercritical coal-fired boilers of thermal power units will serve in non-conventional conditions with frequent temperature changes and large changes. However, the traditional corrosion kinetic model relies on continuous exposure time at a constant temperature, which is challenging to meet the corrosion prediction and safety assessment of boilers in non-conventional service. According to the fundamental atomic/molecular scale process of corrosion of boiler high-temperature heating tube (in supercritical water environments), this paper proposes a new micro-nano scale kinetic model construction method for the prediction of corrosion in non-conventional conditions and the multi-scale application of the model in macro-corrosion data fitting and micro-scale corrosion process analysis. On this basis, a mechanistic corrosion kinetic model with clear microscopic processes and physical meaning for T92 steel was obtained. And a micro-nano scale oxide film growth rate model with temperature and film thickness as independent variables was developed. Finally, these micro-nano scale kinetic models were employed for the corrosion prediction of boiler tubes with known corrosion levels or/and at frequent variable load (non-constant temperature). It is of tremendous importance for evaluating the safety of large coal-fired boilers in non-conventional service.

    Preparation of Mn3O4 catalyst by redox method and study on its catalytic oxidation performance and mechanism of toluene
    Chen WANG, Xiufeng SHI, Xianfeng WU, Fangjia WEI, Haohong ZHANG, Yin CHE, Xu WU
    2023, 74(6):  2447-2457.  doi:10.11949/0438-1157.20230196
    Abstract ( 176 )   HTML ( 9)   PDF (6063KB) ( 230 )  
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    The Mn3O4 catalyst was synthesized by controlling the calcination temperature and atmosphere based on the redox method for the preparation of α-MnO2. Their catalytic performance was systematically investigated. The results showed that Mn3O4 has greater catalytic properties than that of MnO2, its conversion rate was kept above 90% for 100 h at 230℃. In situ infrared and other series of characterization results show that compared with MnO2, Mn3O4 has appropriate redox ability, higher lattice oxygen activity, more surface adsorbed oxygen and stronger toluene adsorption ability, which promotes the benzoic acid species on the surface of the catalyst and rapid conversion, thereby improving its toluene catalytic performance. This work can serve as a guide for the development of manganese-based catalysts and their mechanism for toluene catalytic oxidation performance enhancement.

    Construction of Ni@C@TiO2 core-shell dual-heterojunctions for advanced photo-thermal catalytic hydrogen generation
    Yong LI, Jiaqi GAO, Chao DU, Yali ZHAO, Boqiong LI, Qianqian SHEN, Husheng JIA, Jinbo XUE
    2023, 74(6):  2458-2467.  doi:10.11949/0438-1157.20230323
    Abstract ( 304 )   HTML ( 60)   PDF (4344KB) ( 188 )  
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    Photo-thermal synergistic catalysis coupling photo-chemical and thermo-chemical conversions integrates the benefits of both high driving force of photocatalysis and high selectivity of thermocatalysis. It is one of the most promising methods to enhance its catalytic efficiency. Unfortunately, rapid heat loss and fast charge carrier recombination seriously affect its solar energy utilization and conversion efficiency. Herein, a hierarchical Ni@C@TiO2 core-shell dual-heterojunctions is prepared by resorcinol formaldehyde (RF) template and Ar calcination process to realize efficient heat accumulation and high-flux charge transfer for achieving advanced photo-thermal catalytic hydrogen performance. This system fully combines the broadband absorption of carbon layer and plasmonic property of Ni core. A giant internal electric field (IEF) in the dual-heterojunctions is built, enabling the charge transfer efficiency to be enhanced by 2.4 times. Benefiting from the synergistic effect between Ni@C core photo-thermal effect and Ni/C and C/TiO2 dual-heterojunctions, an excellent photo-thermal efficiency of 78.0% and the performance of photo-thermal catalytic water splitting for hydrogen production hydrogen evolution rate is (1538 μmol·g-1·h-1) are eventually improved. Robust core-shell nanoparticles can be applied to the design of other photo-thermal catalytic systems, providing ideas for the development of more efficient full-spectrum utilization photocatalysts.

    Separation engineering
    Four-channel hollow fiber MFI zeolite membrane for the separation of xylene isomers
    Kuikui HAN, Xianglong TAN, Jinzhi LI, Ting YANG, Chun ZHANG, Yongfen ZHANG, Hongquan LIU, Zhongwei YU, Xuehong GU
    2023, 74(6):  2468-2476.  doi:10.11949/0438-1157.20230293
    Abstract ( 192 )   HTML ( 9)   PDF (1730KB) ( 175 )  
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    MFI zeolite membranes were prepared on four-channel α-Al2O3 hollow fiber supports (7 cm) with high mechanical strength and high loading density by secondary growth method. The effects of synthetic time, operation temperature, partial pressure of raw material and purge gas flow rate on the membrane separation performance of xylene isomer were investigated. The results showed that the four-channel hollow fiber MFI zeolite membrane prepared by hydrothermal synthesis at 160℃ for 12 h possessed the better separation performance of xylene isomers. The separation factor of p-xylene/o-xylene was up to 878 at 150℃, partial pressure of raw material 2 kPa and purge gas flow rate 20 ml/min. PX permeance was 2.1×10-8 mol·m-2·s-1·Pa-1. Based on the optimized membrane preparation conditions, the MFI zeolite membranes were further prepared on the 27 cm long four-channel hollow fiber supports. An excellent p-xylene/o-xylene membrane separation performance was obtained, and the as-prepared membrane can run stably for more than 100 h for the separation of xylene isomer mixture. This study laid the foundation for promoting the batch preparation of hollow fiber MFI zeolite membranes and the technical innovation of traditional separation process.

    Simulation and optimization of selective electrodialysis magnesium and lithium separation process
    Xingchi ZHU, Zhiyuan GUO, Zhiyong JI, Jing WANG, Panpan ZHANG, Jie LIU, Yingying ZHAO, Junsheng YUAN
    2023, 74(6):  2477-2485.  doi:10.11949/0438-1157.20230403
    Abstract ( 165 )   HTML ( 6)   PDF (1969KB) ( 87 )  
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    Selective electrodialysis (S-ED) technology is an effective means to extract lithium resources from brine with high magnesium lithium ratio. A two-dimensional mass transfer steady state model was established to investigate the effects of ionic strength, applied voltage and channel flow rate on the separation of magnesium and lithium with the ion flux distribution as the research object. The results show that the increase of ionic strength and channel flow rate and the decrease of applied voltage can both promote the separation of magnesium and lithium. Under the condition that the ionic strength of the system is 1378 mol/m3, the applied voltage is 0.8 V, and the channel flow rate is 5.7 cm/s, the separation coefficient of lithium and magnesium is 2.31. The research results can provide theoretical guidance and data reference for the promotion of numerical simulation of S-ED processes.

    Modeling neutralization dialysis desalination driven by low concentration waste acid and its validation
    Zhaoguang CHEN, Yuxiang JIA, Meng WANG
    2023, 74(6):  2486-2494.  doi:10.11949/0438-1157.20230275
    Abstract ( 149 )   HTML ( 5)   PDF (1146KB) ( 84 )  
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    The reclamation of low concentration waste acid has long puzzled acid-related technology. Based on the Donnan dialysis principle, a novel technology which couples the waste acid reclamation with neutralization dialysis desalination is put forward in this work. Its feasibility is demonstrated by means of model simulation and experiment validation on the basis of the practical application of surface water desalination driven by a series of waste acid with typical concentrations. Firstly, based on Nernst-Planck equation, Navier-Stokes equation and electroneutral condition, an unsteady mathematical model is established to explore the effects of acid concentration on the desalination rate, desalination speed and pH of system. The simulated results show that the relative low concentration of acid (pH=0.5—2) is strong enough to drive the neutralization dialysis process which is not strengthened remarkably after a further increase of acid concentration. Subsequently, a neutralization dialysis membrane stack is constructed by typical commercial homogeneous or heterogeneous membranes for desalination experiments and provides a series of results which agree well with model predictions. Experiments also show that for high-concentration waste acid, the more significant leakage of the same ion in the heterogeneous membrane will seriously deteriorate the desalination efficiency. The comprehensive research shows that the coupled new process is expected to open up a new way for the resource utilization of low-concentration waste acid.

    Process system engineering
    Dynamic soft sensor modeling method based on distributed Bayesian hidden Markov regression
    Weiming SHAO, Wenxue HAN, Wei SONG, Yong YANG, Can CHEN, Dongya ZHAO
    2023, 74(6):  2495-2502.  doi:10.11949/0438-1157.20230360
    Abstract ( 189 )   HTML ( 11)   PDF (1827KB) ( 122 )  
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    Real-time prediction of key parameters in the chemical process by using soft sensing technology is of great significance for on-line monitoring, automatic control, and real-time optimization of production process. Therefore, a dynamic soft sensor modeling method based on hidden Markov model is proposed. Firstly, aiming at the problem of low computational efficiency caused by large data scales and insufficient utilization of data due to missing data, a predictive model based on distributed Bayesian hidden Markov regression is proposed. Then, a distributed training method that can obtain accurate posterior distribution is proposed for model training. Finally, the effectiveness of the proposed model is verified by the wax oil hydrogenation process.

    Fault monitoring of fermentation process based on attention dynamic convolutional autoencoder
    Xuejin GAO, Yuzhuo YAO, Huayun HAN, Yongsheng QI
    2023, 74(6):  2503-2521.  doi:10.11949/0438-1157.20230332
    Abstract ( 143 )   HTML ( 3)   PDF (2316KB) ( 213 )  
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    The status monitoring of the fermentation process plays a vital role in timely detection of various abnormal faults. However, due to the nonlinear characteristics of the fermentation process data, it is difficult to extract feature information, which increases the difficulty of fault monitoring. In order to solve the above problems, an attention dynamic convolutional autoencoder (ADCAE) based fault monitoring method for fermentation process is proposed. Firstly, a dynamic convolution structure is designed, which can extract low-level features using large-size convolution kernels in the shallow layer, and extract high-level features using small-size convolution kernels in the deep layer, thereby broadening the scope of model feature learning scale. Secondly, a channel convolutional attention (CCA) module is designed, which can extract the nonlinear features of input from different scales, and can be better extract local features in the process of converting channel vectors into weights, which improves the ability to pay attention to effective information. Finally, the dynamic convolution structure and CCA module are integrated into the convolutional autoencoder, so that the model can effectively capture the nonlinear relationship in the variables, so as to better cope with the problem of fault monitoring in the fermentation process. The feasibility of the method was verified by using the simulation platform of penicillin fermentation process and the actual production data of Escherichia coli, and the results showed that the method had good fault monitoring performance.

    Quality-related non-stationary process fault detection method by common trends model
    Yuanzhe SHAO, Zhonggai ZHAO, Fei LIU
    2023, 74(6):  2522-2537.  doi:10.11949/0438-1157.20230066
    Abstract ( 141 )   HTML ( 5)   PDF (3630KB) ( 73 )  
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    Existing quality-related monitoring methods are based on the assumption that the data is stationary, but there are a large number of non-stationary processes in actual production. In order to solve these problems, a new fault detection method based on common trend model is proposed for non-stationary process quality-related faults. The method first identifies the non-stationary process variables and quality variables in the system, then use Gonzalo-Granger decomposition to solve the common trend model, so as to separate the non-stationary part and the stationary part of the non-stationary data. By integrating stationary subspaces of originally stationary data and non-stationary data, slow feature analysis (SFA) and canonical correlation analysis (CCA) are used to establish quality-related monitoring models to realize the effective monitoring of non-stationary quality variables. Finally, by comparing the previous methods with the simulation experiments, it is proved that the proposed method can effectively detect the quality-related faults in the system containing non-stationary variables.

    Surface and interface engineering
    Study on leakage characteristics and parameter influence of pump-out spiral groove oil-gas seal
    Jinbo JIANG, Xin PENG, Wenxuan XU, Rixiu MEN, Chang LIU, Xudong PENG
    2023, 74(6):  2538-2554.  doi:10.11949/0438-1157.20230234
    Abstract ( 135 )   HTML ( 12)   PDF (11011KB) ( 70 )  
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    Taking the pump-out spiral groove oil-gas seal as the research object, the two-phase Reynolds model for solving the flow field of oil-gas seal was established based on the continuity equations of oil and gas phase, respectively. The flow field distribution of the oil-gas sealing medium is obtained by using the finite volume method to discretize and program the solution. The calculation accuracy and efficiency of commercial software VOF model, single-phase Reynolds model and two-phase Reynolds model in solving the flow field of oil-gas seal were compared and analyzed. The effects of operating parameters such as seal gap, oil-gas ratio, rotational speed, medium pressure, and seal ring size on the flow field and steady-state performance of the oil-gas seal were studied, and the near-zero leakage characteristics of the oil-gas seal and its key influencing factors were discussed. The results show that the proposed two-phase Reynolds model method is a high precision and efficient numerical method for calculating the flow field of oil-gas seal. It has the approximate accuracy with the commercial software VOF model, while the calculation time is reduced by one order of magnitude. The medium leakage characteristics and near zero leakage pressure differential of oil-gas seal are mainly affected by the seal clearance, rotational speed and seal ring width. It is expected to achieve zero leakage of oil-gas through the reasonable value of the above-mentioned parameters.

    Rheological and tribological properties of poly-hexylnaphthalene/ poly-α-olefin lithium grease
    Zhiping ZHAO, Chen CHEN, Qiong TANG, Hong XU, Lei LIU, Jinxiang DONG
    2023, 74(6):  2555-2564.  doi:10.11949/0438-1157.20230173
    Abstract ( 126 )   HTML ( 2)   PDF (5178KB) ( 160 )  
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    Poly-hexylnaphthalene base oil was synthesized with 1-hexene and naphthalene catalyzed by ionic liquid (Et3NHCl-AlCl3). Lithium grease prepared by poly-α-olefin (PAO8) base oil was used as reference. Lithium grease with different soap contents was prepared by adjusting the complex ratio of poly-hexylnaphthalene and PAO8 in the base oil (10∶90, 20∶80, 30∶70 and 40∶60). The physicochemical properties of different grease samples were tested and characterized. Meanwhile, the rheometer and SRV-V friction and wear tester were used to systematically evaluate the effects of poly-hexylnaphthalene added on the rheological and tribological properties of lithium grease. And with the help of 3D white light interference analyzer, the worn surface of the steel disc was analyzed. The experimental results show that the combination of poly-hexylnaphthalene and PAO8 had excellent synergistic effect at the mass ratio of 20∶80. The addition of poly-hexylnaphthalene can significantly improve the thickening ability of PAO8 base oil and save the amount of thickener. At the same time, poly-hexylnaphthalene can improve the rheological and tribological properties of PAO8 lithium grease under the condition of higher temperature (85℃).

    Multi-objective optimization analysis of high temperature dynamic pressure split ring seal parameters
    Enzhe BI, Shuangxi LI, Lianxiang SHA, Dengyu LIU, Kaifang CHEN
    2023, 74(6):  2565-2579.  doi:10.11949/0438-1157.20230210
    Abstract ( 155 )   HTML ( 9)   PDF (7882KB) ( 66 )  
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    Aiming at the severe wear and tear characteristics of the aero-engine expansion ring seal under high temperature conditions, a dynamic pressure split ring seal with spiral groove on the end face of the split ring was proposed. Considering the mutual influence of the notch on the flow of the end face of the main seal, the fluid-solid thermal coupling numerical analysis model was established to analyze the sealing performance of the dynamic pressure swelling ring seal. The structural parameters of the static ring were optimized by the response surface method, and the accuracy of the model was verified by experiments. The results show that the sealing performance of dynamic pressure swelling ring is mainly affected by the clearance of the incision, and the wear reduction performance is mainly affected by the axial thickness and radial width. The increase of notch clearance will lead to the decrease of sealing performance and wear reduction performance, but the increase of axial thickness and radial width can effectively reduce the adverse effect of notch clearance. The optimized parameter combination was notch clearance 0.2 mm, axial thickness 13 mm and radial width 6.5 mm. After optimization, the leakage rate was reduced by 26.73%, and the sealing performance and wear reduction performance were significantly improved.

    Effect of glass primary container surface modification on monoclonal antibody aggregates induced by mechanical stress
    Xinyue WANG, Junjie WANG, Sixian CAO, Cui WANG, Lingkun LI, Hongyu WU, Jing HAN, Hao WU
    2023, 74(6):  2580-2588.  doi:10.11949/0438-1157.20230201
    Abstract ( 103 )   HTML ( 0)   PDF (1466KB) ( 115 )  
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    The inner surface of middle borosilicate glass tubing was modified by octadecyltrichlorosilane (OTS). The contact angles of modified surfaces which were measured by contact angle goniometer increased from 50°±1° to 90°±2°. The surface roughness which was measured by atomic force microscope increased from 0.448±0.086 to 1.282±0.117, and the result of Fourier transform infrared spectroscopy (FTIR) indicated that the OTS was successfully coated on the glass surfaces. The monoclonal antibody in glass containers were subjected to mechanical stress. Microflow imaging, size exclusion-high performance liquid chromatography (SE-HPLC) and extrinsic fluorescence dye were used to characterize the stability of monoclonal antibody. The results showed that the OTS-treated hydrophobic interface could reduce the generation of mechanical stress-induced protein aggregates. Due to the strong hydrophobic interaction between hydrophobic surface and protein, the hydrophobic surface could effectively reduce the aggregation of antibody molecules induced by mechanical stress.

    Biochemical engineering and technology
    Efficient preparation of carbon anhydrase nanoparticles capable of capturing CO2 and their characteristics
    Lei MAO, Guanzhang LIU, Hang YUAN, Guangya ZHANG
    2023, 74(6):  2589-2598.  doi:10.11949/0438-1157.20230175
    Abstract ( 164 )   HTML ( 10)   PDF (3432KB) ( 116 )  
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    The use of carbonic anhydrase (CAs) to capture CO2 is more in line with the concept of sustainable development, but it is urgent to reduce the cost of its separation and purification and enhance its survivability in complex environments. Herein, the ferritin with the capability of self-assembling and forming multimers was used as the tag, and the carbonic anhydrase (SazCA) from Sulfurihydrogenibium azorense was linked to the ferritin by a rigid linker. The intracellular difficultly soluble active aggregates were formed during gene expression, which facilitate the purification of SazCA and the activity recovery was as high as 84.8%. The recombinant CAs were obtained after 30 min of sonication of the active aggregates, which was incubated at 50℃ for 50 days without detectable activity lost, and the half-life in pH=9.0 buffer were 150 days. The difficultly soluble active aggregates can spontaneously re-solubilize and formed nano-scale CAs from the micron-scale CAs. The activity of the nano-scale CA was 10-fold higher than that of the micron-scale one. Encouragingly, they showed significantly improved thermal stability compared with wild-type CAs, with a half-life of (211±22) h at 80℃. More importantly, they had a half-life of up to (40.8±2.2) h in the ionic liquid [N1111][Gly] (pH=11.64) with the concentration of 15% (mass), which may have great potentials in the combined uptake and regeneration of CO2 by subsequent ionic liquids and CAs. Finally, the molecular mechanism of difficultly soluble reactive aggregate formation was explored and the electrostatic interaction was found to be one of the important factors. The results demonstrated that ferritin was a novel tag that both greatly simplifies the preparation process and substantially improves its stability, laying a solid foundation for industrial CO2 capture by CAs.

    Study on the construction of high-efficient SRB mixed microflora and its performance under acid stress
    Yanmei ZHANG, Tao YUAN, Jiang LI, Yajie LIU, Zhanxue SUN
    2023, 74(6):  2599-2610.  doi:10.11949/0438-1157.20230157
    Abstract ( 126 )   HTML ( 4)   PDF (3945KB) ( 98 )  
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    Sampling was taken from different natural habitats, and 6 strains of sulfate-reducing bacteria (SRB) with the ability to efficiently remove SO42- were screened out through enrichment, domestication and isolation. Through molecular biological identification, it was determined that the screened strains were Desulfovibrio. The SRB mixed flora was constructed by combining various strains to explore its desulfurization performance under acid stress. A series of batch tests were used to analyze the growth characteristics and sulfate reduction performance of the selected strains. The results showed that the optimal growth C/S ratio of the strains SRB-T3, SRB-X7 and SRB-W6 under neutral conditions was 2.5, and the sulfate reduction capacity could reach more than 0.200 kg/(m3·d). The best growth C/S ratio of domesticated strains SRB-G2, SRB-H1 and SRB-X8 under weak acid conditions is 4.0, which can adapt to low pH environment conditions (pH 5.0—6.5) quickly and reach (0.15±0.007) kg/(m3·d) sulfate reduction capacity. The above strains were combined to construct SRB mixed flora in the ratio of 1∶1∶1∶3∶6∶6, and the sulfate reduction capacity was as high as 0.401 kg/(m3·d) under neutral conditions. Acidity impact test was used to study the desulfurization performance of mixed flora. The results showed that the mixed bacterial system could have good acid resistance and stability through the complementary synergy between different strains compared with the single bacterial system. With the continuous decrease of pH (pH 6.0—5.0), the mixed bacterial system was superior to the single bacterial system in terms of microbial growth and sulfate reduction. When the pH drops to 4.5, the mixed bacterial system could gradually adapt to the acidic environment and recover the sulfate reduction function after a 12 day lag period, and reached 90% of the SO42- removal rate after 28 days, while each single bacterial system showed different degrees of acid inhibition and even successively failed.

    Energy and environmental engineering
    Study on the methane-pulsing reduction characteristics of Fe2O3-Al2O3 oxygen carrier
    Xiaowen ZHOU, Jie DU, Zhanguo ZHANG, Guangwen XU
    2023, 74(6):  2611-2623.  doi:10.11949/0438-1157.20230254
    Abstract ( 137 )   HTML ( 13)   PDF (3993KB) ( 220 )  
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    Developing a highly efficient and low-priced iron-based oxygen carrier is the key to the application of chemical looping reforming of natural gas for hydrogen production. In order to explore the basic principle of designing such an oxygen carrier, the methane-pulsing reduction characteristics of Fe2O3-Al2O3 oxygen carriers with different Fe2O3 contents were studied at 800℃ and without the influence of external and internal diffusion by using a self-designed reactor system capable of on-line methane pulsing and synchronized analysis of gaseous reaction products. The results show that the reduction reaction of Fe2O3 proceeds according to a two-stage mechanism, which can stop at Fe2O3 or completely proceed to FeO with the content of Fe2O3 in the oxygen carrier particles. The variation pattern of the molar ratio of CO2 to CO in the gas phase product with the number of CH4 pulses is also closely related to the content of Fe2O3. Pulse reduction results of particles prepared from a mixture of α-Al2O3 powder and powdery 80% (mass) Fe2O3-Al2O3 oxygen carrier further reveal that the reduction degree of Fe2O3 in a single particle as well as in the whole bed is determined by the molar ratio of CH4 entering the particle per unit time to the absolute amount of Fe2O3 in the particle. At last analysis on the correlations of the reduction degree of Fe2O3 and CH4 conversion and CO2 selectivity leads to a conclusion that only limiting the reduction process of Fe2O3 oxygen carries to the stage of Fe3O4 formation could yield a reacted stream of a sufficiently high CO2 concentration for low-cost recovery of high purity CO2.

    Experimental study on the low to medium temperature oxidation characteristics and kinetics of micro-size iron powder
    Xueyan WEI, Yong QIAN
    2023, 74(6):  2624-2638.  doi:10.11949/0438-1157.20230121
    Abstract ( 199 )   HTML ( 8)   PDF (7153KB) ( 75 )  
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    Micro-size iron powder is a new type of carbon-free energy with great potential. In order to realize large-scale and efficient clean combustion and utilization of metal fuel, it is necessary to master its basic combustion characteristics and chemical reaction kinetics principle. This requires a great deal of research on the chemical kinetics parameters, especially the activation energy. Thermogravimetric analysis (TGA) is the most commonly used tool to obtain kinetic data in experiments, and isotransform kinetic analysis is the most effective method to process the calculation of TGA data. In this paper, six micro-size iron powders of 6, 25, 30, 40, 55, and 120 μm were used to conduct experiments on the thermogravimetric analyzer, and the TGA data are processed and analyzed by Friedman isoconversional method, including the analysis of original TGA data, obtaining conversion data, interpolation of conversion and derivative conversion data, calculating activation energy and conversion function of six kinds of iron powder fitting by Friedman isoconversional method, and comparative analysis of iron powder data with different particle sizes. The results show that in most cases, the smaller the particle size of micro-size iron powder, the more sufficient the reaction is at the same temperature. Before the reaction speed reaches its peak value, the smaller the particle size of iron powder, the faster the reaction speed can get. When the reaction speed reaches its peak value, the smaller the particle size of iron powder, the slower the reaction speed can get. When the conversion is greater than 0.300, for 30, 40, 55, and 120 μm samples, the smaller the particle size of iron powder, the higher the activation energy can get.

    Experimental study on inhibition effect of natural gas hydrate formation by mixing ionic liquid with PVCap
    Zhen LONG, Jinhang WANG, Junjie REN, Yong HE, Xuebing ZHOU, Deqing LIANG
    2023, 74(6):  2639-2646.  doi:10.11949/0438-1157.20230180
    Abstract ( 148 )   HTML ( 5)   PDF (3752KB) ( 148 )  
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    An investigation on the effect of an ionic liquid N-butyl-N-methylpyrrolidine tetrafluoroborate ([BMP][BF4]), a commercial kinetic hydrate inhibitor poly(N-vinylcaprolactam) (PVCap) and their binary mixture on the hydrate formation process from methane/ethane/propane ternary mixture was carried out by using a self-designed high-pressure apparatus. It was found that at any concentration [0.25%—2.0% (mass)], [BMP][BF4] had a much weaker inhibitory effect on mixed gas hydrate than PVCap, but had a significant synergistic effect on PVCap, which was enhanced as the proportion of PVCap increased. Moreover, with the increasing proportion of PVCap, the compound inhibitor performed better. Both powder X-ray diffraction patterns and low-temperature Raman spectra indicated that sⅠ and sⅡ hydrates coexisted in all tested systems. The inhibitors containing PVCap reduced the relative contents of sⅠ and sⅡ hydrates in the samples. The images observed from scanning electron cryomicroscopy (Cryo-SEM) indicated that the presence of PVCap and its mixture with [BMP]BF4] made the formed hydrates more coarse and porous.

    Application of quinone profile method to indicate structure and activity of functional microbial community in trichloroethylene-contaminated soil
    Lixiang ZHU, Moye LUO, Xiaodong ZHANG, Tao LONG, Ran YU
    2023, 74(6):  2647-2654.  doi:10.11949/0438-1157.20230271
    Abstract ( 99 )   HTML ( 0)   PDF (892KB) ( 42 )  
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    This study aimed to evaluate the potential of bioremediation of organic polluted sites using quinone profile method to analyze the activity of functional microbial in trichloroethylene (TCE)-contaminated soil. Microcosm experiments were conducted to investigate the degradation process of TCE in soil and to create a quinone profile. The profile was compared with existing quinone spectral libraries, and a quinone with potential indicator microbial activity for TCE-contaminated soil was selected. By analyzing the changes of the total quinone concentration (TQ) and the concentration of the selected quinone, changes in the active microbial population and functional microbial activity during the degradation process were observed and validated as feasible indicators for reflecting potential microbial activity. The results indicated that primary degradation occurred during 0—50 days, with a degradation rate of TCE over 65% for all three soil groups. Differences in the biodegradation pathways of TCE were observed in the three soil groups. UQ-8, UQ-9, MK-6, and MK-8 were identified as characteristic quinones in TCE-contaminated soil. There were significant positive correlations between TQ, microbial biomass carbon (MTOC), total concentration of characteristic quinones and dehydrogenase activity (P<0.05). Therefore, the quinone profile method can provide an important monitoring method guidance for the monitoring of natural attenuation risk control or the implementation of bioremediation in organically polluted sites.

    Remediation of percolate water from uranium tailings reservoir by coupling iron-carbon micro-electrolysis and sulfate reducing bacteria
    Nan HU, Demin TAO, Zhaolan YANG, Xuebing WANG, Xiangxu ZHANG, Yulong LIU, Dexin DING
    2023, 74(6):  2655-2667.  doi:10.11949/0438-1157.20230147
    Abstract ( 104 )   HTML ( 1)   PDF (5796KB) ( 47 )  
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    Six reactors, including iron-carbon micro-electrolysis coupling with sulfate reducing bacteria (Fe/C-SRB), aluminum-carbon micro-electrolysis coupling with sulfate reducing bacteria (Al/C-SRB), carbon coupling with sulfate reducing bacteria (C-SRB), iron-carbon micro-electrolysis (Fe/C), aluminum-carbon micro-electrolysis (Al/C) and carbon (C), were designed to investigate their effects on the remediation of U, Mn, Zn, SO42- and NO3- in the percolate water from the uranium tailings reservoir. The results indicated that the concentration of U in the effluent of Fe/C-SRB reactor system decreased to 0.05 mg/L after 2.5 h. The concentration of Mn decreased to 10 mg/L and the concentration of Zn decreased to 0.05 mg/L after 1 d. The concentration of SO42- decreased to 50 mg/L after 10 d, and the concentration of NO3- decreased to 10 mg/L after 18 d, all of which satisfied with the relevant national emission standards, and operated stably. The treatment efficiency of Fe/C-SRB reactor was significantly higher than that of other reactors. The total abundance of microbial communities including Desulfotomaculum, Desulfovibrio, and Desulfosporosinus with the function of reducing U(Ⅵ) in the filler of the Fe/C-SRB reactor system reached 61.45%, which was 40.35%, 60.06%, 57.22%, 59.73% and 52.46% higher than that of Al/C-SRB, C-SRB, Al/C, Fe/C and C reactor systems at 60 d, respectively. The 33.20% of U(Ⅵ) in the leachate was reduced to U(Ⅳ) by microorganisms and iron. The study demonstrates that Fe/C-SRB is a promising method for remediating percolation water from uranium tailings reservoir.

    Performance study of KOH modified carbide slag for removal of carbonyl sulfide
    Feng ZHU, Kailin CHEN, Xiaofeng HUANG, Yinzhu BAO, Wenbin LI, Jiaxin LIU, Weiqiang WU, Wangwei GAO
    2023, 74(6):  2668-2679.  doi:10.11949/0438-1157.20230296
    Abstract ( 123 )   HTML ( 7)   PDF (4627KB) ( 62 )  
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    In this paper, KOH modified carbide slag was prepared by excessive impregnation using carbide slag as raw material, and the effects of different KOH content (10%—30%), calcination temperature (700—900℃), calcination time (5—7 h), carbonyl sulfide (COS) inlet concentration (200—1000 mg/m3), space velocity (5733—11404 h-1), and reaction temperature (25—75℃) on the removal of COS were investigated. The desulfurization performance and reaction process of KOH modified carbide slag were preliminarily studied by N2-BET, SEM-EDS, XPS, XRD and FTIR, and it was found that catalytic hydrolysis, oxidation reaction and acid-base adsorption mainly occurred in the process of COS removal with KOH modified carbide slag. The results showed that the optimal preparation conditions were the calcination temperature of 800℃, the calcination time of 6 h, and the KOH content of 25%. Under this condition, the best effect of COS removal from KOH modified carbide slag was achieved when the inlet concentration, reaction temperature and space velocity was 600 mg/m3, 25℃ and 5733 h-1, respectively, and COS breakthrough adsorption amount was 43.70 mg/g at this time.

    Material science and engineering, nanotechnology
    Development and properties of PEG-EG solid-solid phase change materials
    Zhen LI, Bo ZHANG, Liwei WANG
    2023, 74(6):  2680-2688.  doi:10.11949/0438-1157.20230231
    Abstract ( 279 )   HTML ( 20)   PDF (2815KB) ( 220 )  
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    Aiming at the problems of easy leakage and low thermal conductivity of solid-liquid phase change materials, a polyethylene glycol (PEG) solid-solid phase change composite material was proposed. The composite material is obtained by chemical grafting of expanded graphite (EG) framework with different proportions and high thermal conductivity and PEG. The results show that the composite phase change material has a leakage phenomenon when the mass fraction of EG is 10%, while there is no more leakage phenomenon when the mass fraction of EG is 20% and 30%. In addition, the thermal conductivity of the composites increased with the increment of EG content. The highest thermal conductivity of 8.031 W·m-1·K-1 was obtained with the EG mass fraction of 30%, which was 27.79 times that of the pure phase change material (0.289 W·m-1·K-1). After 50 cycles, the phase change temperature and enthalpy of all composite materials did not change significantly, which proved the excellent thermal stability. Considering the comprehensive performance, under the condition of the optimal EG mass fraction of 20%, the phase change composite is form-stable and own high phase change enthalpy (138.30 J·g-1), high crystallinity (88.6%), and high thermal conductivity (6.870 W·m-1·K-1).

    Study on preparation of poly(N-isopropylacrylamide-co-allylthiourea) smart microgels and responsive performance of Hg2+
    Shiting XIE, Zhuang LIU, Rui XIE, Xiaojie JU, Wei WANG, Dawei PAN, Liangyin CHU
    2023, 74(6):  2689-2698.  doi:10.11949/0438-1157.20230298
    Abstract ( 158 )   HTML ( 7)   PDF (1515KB) ( 60 )  
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    In this paper, a kind of smart microgels, poly(N-isopropylacrylamide-co-allylthiourea) (PNA), for the detection and removal of Hg2+ was prepared by using N-isopropylacrylamide (NIPAM) and allylthiourea (ATU) as copolymer monomers, N,N'-methylenebisacrylamide (MBA) as a crosslinking agent, and 2,2'-azobis(2-methylpropionamidine) dihydrochloride (V50) as an initiator through precipitation polymerization. The chemical composition and morphology of the microgels were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The particle size distribution and temperature responsiveness of microgels were studied by dynamic light scattering nanoparticle analyzer (DLS). The effects of interfering ions, pH and temperature on the Hg2+-response of microgels were investigated. The adsorption and removal efficiency of PNA microgels for Hg2+ were explored by using atomic absorption spectrometer (AAS). The results show that, the PNA microgels have a temperature sensitivity and specific responsiveness to Hg2+. The shrinkage ratio (RD) caused by Hg2+-response decreases with the increase of ATU monomer ratio. The optimal detection temperature was determined to be 30℃. With the increase of Hg2+ concentration, the RD value gradually decreased. According to the corresponding relationship between the Hg2+ concentration and the RD of microgels, the calculation formula of Hg2+ concentration was fitted. The lowest detection concentration of PNA microgels can reach 10-8 mol·L-1. In the adsorption experiment, the adsorption capacity of the PNA microgel was found to increase with the Hg2+ concentration. An adsorption rate of over 80% was achieved for Hg2+ solutions below 10-4 mol·L-1, and the minimum concentration of Hg2+ could be reduced to 0.0005 mg·L-1. Compared with Zn2+, Cd2+and Pb2+, the adsorption rate of PNA microgels for Hg2+ is about 7 times more than other metal ions. The research results provide a new method for the detection and removal of harmful metal Hg2+.

    Fabrication and properties of dual shape memory MXene based hydrogels for flexible sensor
    Qin YANG, Chuanjian QIN, Mingzi LI, Wenjing YANG, Weijie ZHAO, Hu LIU
    2023, 74(6):  2699-2707.  doi:10.11949/0438-1157.20230261
    Abstract ( 231 )   HTML ( 12)   PDF (2889KB) ( 258 )  
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    The construction of multifunctional hydrogel flexible sensors with excellent conductivity and multiple shape memory is extremely challenging. Herein, MXene nanosheets were incorporated into both temperature-responsive polymer polyvinyl alcohol and metal ion-responsive polyacrylic acid networks by free copolymerization and freeze-thaw methods through molecular design to prepare a conductive hydrogel with dual shape memory and construct a strain sensor. The morphology and structure of MXene nanosheets and composite hydrogels were studied by transmission electron microscopy, scanning electron microscopy, X-ray diffraction and infrared spectroscopy, and the influence of MXene content on the mechanical properties, electrical conductivity and shape memory performance of the hydrogels were investigated. The research shows that MXene nanosheets uniformly dispersed in the hydrogel and crosslinked with the hydrogel network through hydrogen bonding, which not only strengthens the mechanical properties of the hydrogel, but also improves the shape fixation rate of the double shape memory hydrogel. The tensile strength of the composite hydrogel is increased to 236.10 kPa, 7.3 times that of the pure water gel, the shape fixation rate of ferric ions increased from 69.44% to 94.44%, and the shape fixation rate of the temperature response increased from 63.89% to 88.89%. The signal of the hydrogel sensor showed excellent continuity and consistency under multiple rapid tensile strain cycles, which provides new ideas for the construction of environmentally adaptive flexible sensors.

    Influence of geometrical dimensions and defects on the thermal transport properties of graphyne nanoribbons
    Yuanchao LIU, Xuhao JIANG, Ke SHAO, Yifan XU, Jianbin ZHONG, Zhuan LI
    2023, 74(6):  2708-2716.  doi:10.11949/0438-1157.20230242
    Abstract ( 138 )   HTML ( 4)   PDF (3957KB) ( 142 )  
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    Based on the molecular dynamics simulation method, the thermal transport properties of graphyne nanoribbons (GYNR) are profoundly studied, focusing on the influence of geometrical dimensions, defect type and defect position (horizontal and vertical directions, benzene ring and acetylene chain), and arrangement on the phonon thermal transport, etc., and the regulation mechanism of the phonon thermal transport is revealed and analyzed. The research results show that the ideal thermal conductivity of GYNR is only 18.22 W/(m·K). Compared with graphene, the thermal conductivity of GYNR only rises to 21.37 W/(m·K) with the increase of size. The thermal conductivity of GYRN is less dependent on the geometry size. For defect types, the thermal conductivity is suppressed more strongly in the presence of vacancy defects than nitrogen doping, which can be as low as 9.19 W/(m·K). For the location of defects, the thermal conductivity is lower when the defects are located on the benzene ring or near the nanoribbon boundary compared to the alkyne chain. If multiple defects are distributed in parallel, the thermal conductivity can lower than 8.00 W/(m·K) compared with the triangular structure distribution. The results can provide theoretical support and reference for the development, application and regulation of graphyne materials in the thermoelectric field of nano-devices.