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Table of Content
05 May 2023, Volume 74 Issue 5
    Reviews and monographs
    Research progress in measurement methods in vapor-liquid critical properties of mixtures
    Xiaoyu YAO, Jun SHEN, Jian LI, Zhenxing LI, Huifang KANG, Bo TANG, Xueqiang DONG, Maoqiong GONG
    2023, 74(5):  1847-1861.  doi:10.11949/0438-1157.20230075
    Abstract ( 324 )   HTML ( 32)   PDF (3732KB) ( 368 )  
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    Near-critical and supercritical fluids have excellent transport and thermodynamic properties and can be widely used in fields such as chemical engineering, environment, machinery, and thermal energy utilization. Since the thermophysical properties including fluid density will change substantially near the critical point, it is of great significance to accurately determine the critical point of the fluid, including critical temperature, critical pressure and critical density data, to guide the optimization of thermodynamic cycle and system component design. Currently, experimental measurement is the most direct way to obtain high-precision critical parameters. This article first outlines the theory of gas-liquid critical points, the current research status of critical parameters, and their typical application scenarios. Secondly, it summarizes the main measurement methods of critical parameters, including constant volume method, variable volume method, flow method, pulse heating method, density line midpoint law method, pressure-volume-temperature (p-V-T) relationship method, quasi-static thermal analysis method, and physical property method. The advantages and disadvantages, scope of application, accuracy and main research institutions of these methods are summarized. Finally, the challenges and future development trends of critical parameter measurement methods are discussed.

    Research progress in the removal of water pollutants by carbon-based materials via electrooxidation
    Xu GUO, Yongzheng ZHANG, Houbing XIA, Na YANG, Zhenzhen ZHU, Jingyao QI
    2023, 74(5):  1862-1874.  doi:10.11949/0438-1157.20230135
    Abstract ( 292 )   HTML ( 19)   PDF (3587KB) ( 279 )  
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    Electrode materials are the key to electro-oxidation technology. Carbon-based materials have the advantages of good stability, adjustable structure, good conductivity, and wide range of sources. Starting from the electrooxidation process of carbon-based materials, this article briefly introduces the degradation behavior of carbon materials under anode current and their ability to enhance free radical generation by composite active materials. The research progress of carbon based materials, such as carbon nanotubes, graphene, and biomass carbon, in regulating the electrooxidation performance through defect control, surface modification, and interface engineering is systematically reviewed. Finally, the development of carbon-based anode materials is prospected.

    Research on high injection superheat cycle for R290 low pressure ratio heat pump
    Bowen LEI, Jianhua WU, Qihang WU
    2023, 74(5):  1875-1883.  doi:10.11949/0438-1157.20221680
    Abstract ( 329 )   HTML ( 10)   PDF (2701KB) ( 411 )  
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    The natural working fluid propane (R290) has a GWP close to zero. It is environmentally friendly, has excellent thermophysical properties, and has good application prospects. The discharge temperature of R290 high-pressure rotary compressor is low due to the low adiabatic index of R290, especially in the small pressure ratio condition. The high solubility of R290 leads to the low viscosity of R290/lubricant mixture in the oil sump of high-pressure rotary compressor, which may be difficult to meet the crankshaft/bearings system lubrication and affect compressor reliability. This paper analyzes the relationship between R290 solubility in lubricant and viscosity of R290/lubricant mixture with mixture superheat in low pressure ratio condition. The high injection superheat cycle (HISC) is proposed that it takes advantage of the available energy in the condenser outlet to improve the injection superheat controlling the discharge superheat and the viscosity of R290/lubricant mixture. Meanwhile, HISC can effectively improve the system performance with 11.4% improvement in COP and 23.4% improvement in volumetric heating capacity compared with the single-stage cycle at evaporation temperature -2.89℃ and condensation temperature 51.5℃.

    Comprehensive evaluation model combined with genetic algorithm for the study on the performance of ORC system with zeotropic mixture
    Yurong DANG, Chunlan MO, Kerui SHI, Yingcong FANG, Ziyang ZHANG, Zuoshun LI
    2023, 74(5):  1884-1895.  doi:10.11949/0438-1157.20221492
    Abstract ( 131 )   HTML ( 7)   PDF (3547KB) ( 59 )  
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    The system uses R601a/R600 as the working fluid to recover industrial waste heat. It uses the thermodynamic performance (output power Wnet, thermal efficiency ηth and exergy efficiency εex), economic performance (investment cost payback period ICPP, heat exchanger area per unit power output APR), and environmental impact (emissions of CO2 equivalent ECE, environmental exergy cost Exc) as evaluation indicators, and the weights of different evaluation indicators are determined by the AHP-sum-product method and combined with the genetic algorithm to conduct comprehensive analysis and optimization of the system. The results show that when the weight of the objective functions of the comprehensive evaluation index F1 is in the following order: environmental impact > economic performance > thermodynamic performance. When the mass fraction ratio of R601a/R600 is 0.33%/99.67% and the evaporation temperature is 137.2℃, Wnet, ηth, εex, APR, ICPP, ECE and Exc are 62.9 kW, 15.8%, 48.7%, 4.3 m2/kW, 6.6 a, 25.0 t, and 4.0 W, respectively. The ECE and Exc obtained are reduced by 45.9% and 57.0%, respectively, compared with those obtained by TOPSIS based on balanced weight. This shows that F1 pays more attention to environmental impact, and can give more reference plans for actual projects according to different weights, which is more instructive than traditional TOPSIS.

    Phase equilibria and calculation of quaternary system LiCl+MgCl2+CaCl2+H2O at 323.2 K
    Ke CHEN, Li DU, Ying ZENG, Siying REN, Xudong YU
    2023, 74(5):  1896-1903.  doi:10.11949/0438-1157.20230115
    Abstract ( 248 )   HTML ( 6)   PDF (1268KB) ( 129 )  
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    The solid-liquid phase equilibria of the quaternary system LiCl+MgCl2+CaCl2+H2O at 323.2 K were studied by the isothermal dissolution method. The density, refractive index and composition of liquid phase were determined experimentally. The phase diagram of the quaternary system at 323.2 K was plotted. The results show that there are two double salts LiCl·MgCl2·7H2O and 2MgCl2·CaCl2·12H2O formed in the quaternary system, belonging to a complex system. The phase diagram of this quaternary system consists of three invariant points, seven univariate curves, five crystallization fields corresponding to MgCl2·6H2O, LiCl·H2O, CaCl2·2H2O, LiCl·MgCl2·7H2O, 2MgCl2·CaCl2·12H2O. Comparing the phase diagram of the quaternary system at 323.2 K and 298.2 K, it has found that with the increase of temperature, calcium chloride is converted from CaCl2·6H2O and CaCl2·4H2O to CaCl2·2H2O, the crystallization fields of LiCl·MgCl2·7H2O and MgCl2·6H2O decrease and the crystallization fields of LiCl·H2O and 2MgCl2·CaCl2·12H2O increase, which indicates that increasing temperature is beneficial to the precipitation of LiCl·H2O and 2MgCl2·CaCl2·12H2O. The solubility of the quaternary system was calculated by using the PSC model, and the calculated results were basically consistent with the experimental results.

    Fluid dynamics and transport phenomena
    Study of the mechanism of internal circulation regulation during evaporation of NaCl droplets on hydrophobic interface
    Zhengtao LI, Zhijie YUAN, Gaohong HE, Xiaobin JIANG
    2023, 74(5):  1904-1913.  doi:10.11949/0438-1157.20230340
    Abstract ( 236 )   HTML ( 12)   PDF (3435KB) ( 241 )  
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    Evaporation crystallization of brine micro-droplets plays a very important role in seawater desalination, crystal preparation, drug premixing and particle screening. Herein, a computational hydrodynamic model is developed to simulate the evaporation process of NaCl aqueous droplets on a hydrophobic platform with different heat transfer coefficients and diameters at the hydrophobic interface, mainly to predict the circulation evolution mechanism of the fluid inside the droplet under the effect of temperature and concentration differences. The simulative results were validated by optical visualization and infrared thermal imager. The results indicated that the circulation inside the NaCl aqueous droplet is dominated by Rayleigh convection and the solute Marangoni effect at room temperature evaporation. Different heat transfer coefficients at the solid-liquid interface affect the heating rate and temperature distribution of the droplet, and the thermal Marangoni effect can dominate the internal circulation of the droplet when the temperature difference is greater than a certain value. A phase diagram of the evolution of the flow field based on the modulation intervals of the Rayleigh and Marangoni numbers was produced to effectively predict the circulation state within the droplet. The direction and duration of circulation within the brine droplet can be controlled by tuning the thermal Marangoni effect, which affects the crystal morphology and deposition distribution of the final evaporative crystallization. This work can provide a theoretical basis for evaporation interface design and process control of evaporation crystallization.

    Effect of thermophysical properties on the heat transfer characteristics of solid-liquid phase change for composite PCMs
    Jialin DAI, Weidong BI, Yumei YONG, Wenqiang CHEN, Hanyang MO, Bing SUN, Chao YANG
    2023, 74(5):  1914-1927.  doi:10.11949/0438-1157.20230070
    Abstract ( 183 )   HTML ( 8)   PDF (4754KB) ( 95 )  
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    For composite phase change materials (CPCMs), the heat storage performance can be described accurately and used effectively only if the effects of thermophysical properties of substrate and phase change materials (PCMs) on heat transfer characteristics are mastered. Therefore, the effects of thermophysical properties on the heat transfer characteristics of phase change for CPCMs were investigated numerically at the pore scale. Based on the validated double-distributed-function (DDF) lattice Boltzmann (LB) model, the phase change, heat transfer, and flow in CPCMs were simulated under the conditions of different specific heat capacities and thermal diffusion coefficients of solid PCMs, liquid PCMs, and substrate. The influence of thermophysical properties on the phase change rate and heat storage were summarized. The numerical results showed that the heat transfer was accelerated by the internal flow of liquid PCMs. The larger the specific heat capacity of the substrate, the faster the phase change frontier and the greater the heat storage capacity can get. The large thermal diffusion coefficient of the substrate could enhance the phase change rate. While the specific heat capacity of solid PCMs was smaller, the phase change rate was faster, and the solid-liquid phase interface was thicker. And the wider interface of phase change could lead to a more unstable process of phase change. If higher phase transition rate is more important, PCMs with the specific heat capacity of solid phase smaller than liquid phase can be selected. However, if the stability of phase transition is more important, PCMs with the specific heat capacity of solid phase larger than liquid phase can be preferred.

    Pore scale numerical simulations for wicking performance of metallic woven mesh
    Xiaoyu JIA, Jian YANG, Bo WANG, Mei LIN, Qiuwang WANG
    2023, 74(5):  1928-1938.  doi:10.11949/0438-1157.20230238
    Abstract ( 206 )   HTML ( 5)   PDF (3938KB) ( 242 )  
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    Metallic woven meshes have received considerable attention in several engineering applications as filtration, catalysis, heat transfer enhancement and explosion suppression owing to their merits of controllable pore structure, high specific surface area, high mechanical strength and low price. In order to characterize their capillary performance, firstly, the detailed geometrical dimensions of four kinds of square-shaped plain weave wire screen with different mesh numbers were measured. Then a numerical model was developed to evaluate the fluid dynamics of a porous woven mesh at the pore scale. Finally, based on the pore scale numerical results, the effects of wire diameter and mesh number on porosity, specific surface area and permeability were analyzed. The study found that the Kozeny-Carman formula can better predict the permeability relationship of wire mesh at low flow rates (less than 0.01 m/s), and the geometric factor has a logarithmic relationship with the mesh diameter. While at high flow rates (larger than 0.01 m/s), the flow regime transition from Darcy to Forchheimer, the inertial contribution can not be neglected. The Darcy and non-Darcy permeability coefficient can be obtained by Forchheimer correlation, and the relationship between permeability and porosity and wire diameter is modified according to Kozeny-like model. The obtained fitting formulae between geometric structure and capillary performance of plain woven wire mesh provide a design guideline for the metallic woven mesh used for wicking and transpiration cooling.

    Effect of burner bias angle on distribution characteristics of gasifier slag layer
    Bimao ZHOU, Shisen XU, Xiaoxiao WANG, Gang LIU, Xiaoyu LI, Yongqiang REN, Houzhang TAN
    2023, 74(5):  1939-1949.  doi:10.11949/0438-1157.20230140
    Abstract ( 131 )   HTML ( 8)   PDF (3154KB) ( 66 )  
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    The ash-slag ratio (the fly ash carried away by syngas to slag deposited on the wall) of the gasifier is critical to the service life of subsequent syngas cleaning equipment. Optimizing the bias angle of burners is an effective way to control the ash-slag ratio of gasifier. The effects of the bias angle of four burners in the first stage of HNCERI (Huaneng Clean Energy Research Institute) gasifier on the ash-slag ratio, slag layer and refractory material are studied by numerical simulation method. The numerical simulation results show that when the bias angle of burners increases from 0°to 4.5°, the ash-slag ratio decreases from 2.0 to 0.8, and the average residence time of liquid slag layer reduced by 31.5%. With the increase of bias angle, the thickness of liquid/solid slag layer increases at the slag tap hole. While the thickness of solid slag layer decreases and the thickness of liquid slag layer increases at H=4.45—5.07 m. The velocity of liquid slag is negatively correlated with the viscosity of the liquid slag and positively correlated with the thickness of the liquid slag. The liquid slag thickness is mainly affected by the velocity of the liquid slag and the particle deposition rate. With the increase of the bias angle, the average temperature of the refractory material surface above the burner plane increases and below the burner plane decreases. When the bias angle is 3.5°, the highest temperature of the refractory material is the lowest. On the premise of effectively reducing the ash-slag ratio, reducing the possibility of the slag block, slag layer falling off and refractory material ablation, the HNCERI gasifier burner deflection angle is recommended to be 3.5°.

    Numerical simulation of bubble plume vortex characteristics for non-Newtonian fluids
    Xin DONG, Yongrui SHAN, Yinuo LIU, Ying FENG, Jianwei ZHANG
    2023, 74(5):  1950-1964.  doi:10.11949/0438-1157.20221462
    Abstract ( 205 )   HTML ( 12)   PDF (9441KB) ( 111 )  
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    In order to further explore the flow characteristics of gas-liquid two-phase flow in non-Newtonian fluid, the large eddy simulation (LES) method was used to study the vortex characteristics of bubble plume in non-Newtonian fluid. Taking clean water and sodium carboxymethyl cellulose (CMC) aqueous solutions with different mass fractions as the research objects, the velocity, plume structure, vorticity and vortex evolution of gas under different apparent gas velocities and liquid rheological properties were analyzed. The results show that the evolution rate of vortices decreases with the increase of non-Newtonian fluid concentration. Combined with the Q criterion, the vortex characteristics distribution under different working conditions was analyzed. With the increase of CMC aqueous solution concentration, the Q value in the flow field decreased continuously, and the evolution rate of vortex in the flow field weakened with the increase of non-Newtonian fluid characteristics.

    Numerical simulation and optimization of acoustic streaming considering inhomogeneous bubble cloud dissipation in rectangular reactor
    Zedong WANG, Zhiping SHI, Liyan LIU
    2023, 74(5):  1965-1973.  doi:10.11949/0438-1157.20230236
    Abstract ( 137 )   HTML ( 6)   PDF (3583KB) ( 159 )  
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    The acoustic flow effect can effectively enhance the mass transfer process in the acoustic reactor, and the driving force of the acoustic flow in the large acoustic reactor mainly comes from the nonlinear dissipation of acoustic waves. A nonlinear acoustic model combined with non-uniform bubbles distribution was employed to predict the acoustic field in a bath-type scale-upsonoreactor. Volume force was coupled with the acoustic field to predict the three-dimension acoustic streaming field. The accuracy of the numerical model was verified through particle image velocimetry. The influence of ultrasonic power, reactor width, and liquid level on acoustic streaming was studied. The results show that while increasing ultrasonic power improved acoustic streaming, it also intensified dissipation, reducing the conversion rate of cavitation energy. The narrow space seriously hinders the development of acoustic flow. While oversized reactor is not conducive to high velocity region volume, but even degrades performance of acoustic streaming effect. The variation curves indicate that under an ultrasonic input of 60 W at 40 kHz, the optimal reactor size and liquid level are about 200 mm and 100 mm, respectively.

    A unified lattice Boltzmann model for heat transfer in opacifiers-doped silica aerogel
    Kunyang FAN, Jingxing YANG, Haibo XU, Xingrong LIAN, Fengmei HE, Conghui CHEN, Zengyao LI
    2023, 74(5):  1974-1981.  doi:10.11949/0438-1157.20221612
    Abstract ( 132 )   HTML ( 3)   PDF (2789KB) ( 173 )  
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    Aerogel is a nanoporous super-insulation material, and its internal heat transfer process involves gas-phase heat conduction, solid-phase heat conduction, gas-solid coupling heat transfer and radiation heat transfer. In the present study, the energy equation containing the radiation source and the radiation transfer equation are derived based on the lattice Boltzmann method (LBM), and a unified lattice Boltzmann model to describe multi-mode and multi-scale coupled heat transfer in SiO2 aerogel composites is established. The effects of diameter and doping volume fraction of SiC opacifiers on the thermal insulation performance of SiO2 aerogel composites are investigated. The temperature-dependent optimal diameter and doping volume fraction of SiC opacifiers are obtained to minimize the effective thermal conductivity of SiC-doped silica aerogel composites.

    Study on influence of mechanical stirring on heat transfer characteristics during jet heating of crude oil storage tank
    Jian ZHAO, Xingchao ZHOU, Dan XIA, Hang DONG
    2023, 74(5):  1982-1999.  doi:10.11949/0438-1157.20230006
    Abstract ( 197 )   HTML ( 7)   PDF (10976KB) ( 102 )  
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    The physical and mathematical models of heat transfer and flow processes in a large floating roof storage tank under the synergy of jet heating and mechanical stirring were established. The sliding grid technique was used to model the stirring impeller. The flow and heat transfer laws of strong and weak buoyant jet heating processes were numerically simulated based on the finite volume method (FVM). The results show that compared with the strong buoyancy jet, the heating rate of the weak buoyancy jet can be increased by 74%, and the heating time required to reach the same temperature can be shortened by 42%. For the strong buoyant jet heating process, the increase of mechanical stirring can significantly increase the overall velocity in the computational domain, enhance the heat exchange between hot and cold media, increase the heating rate by 9.6%. It can also make more uniform oil temperature distribution in the computational domain and a 17% reduction in temperature variance. For the weak buoyancy jet heating process, although increasing the stirring effect can only increase the heating rate by 0.9%, it can reduce the temperature variance by 29%. Mechanical stirring has a more significant effect on the heating rate of strong buoyant jet and the temperature uniform distribution of weak buoyant jet. It is found that mechanical stirring can increase the heating efficiency of strong buoyant jet by 0.7%. In addition, further studies have found that the installation height of agitator plays an important function in eliminating the low-temperature area at the bottom of the actual storage tank and regulating the oil temperature distribution. The numerical simulation results can provide a significant reference for the structural design of mechanical agitator.

    Investigation on flow characteristics of wet particles with power-law liquid-solid drag models in fluidized bed
    Zihan YUAN, Shuyan WANG, Baoli SHAO, Lei XIE, Xi CHEN, Yimei MA
    2023, 74(5):  2000-2012.  doi:10.11949/0438-1157.20230265
    Abstract ( 130 )   HTML ( 9)   PDF (4659KB) ( 211 )  
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    The liquid-solid two-phase flow behaviors in the power-law fluidized bed are simulated using the Euler-Euler two-fluid model (TFM) based on the kinetic theory of granular flow (KTGF). Based on the pressure drop equations and rheological equations of power-law fluids, two kinds of power-law liquid-solid drag models are presented. And the dynamic restitution coefficient model of wet particles considering the liquid film effect is introduced to calculate the interaction between power-law fluids and particles. The predicted solid holdups are compared with the experimental values in references, the results show that the relative errors of power-law liquid-solid drag models combining dynamic restitution coefficient model are between 0.45% and 1.59%, which is closer to the experimental results. The influences of the consistency coefficients and the flow behavior indexes on the flow characteristics of the particles are explored, indicating that with the increase of the rheological parameters, the averaged solids holdup in the fluidized bed decreases, and the liquid film covered on the surface of wet particles becomes thicker and the normal restitution coefficient decreases. The granular temperature increases first and then decreases with the increase of flow behavior index, and rises with the increase of consistency coefficient. The drag coefficient, granular pressure, and granular viscosity all gradually decrease as the rheological parameters enhance. The concentration of particles near the wall is obviously higher than that near the center, and the particles move upward at the center and fall in the vicinity of the wall, forming the classic core-annulus structure.

    Separation engineering
    Effect of alkali cations in zeolites on adsorption and separation of CO2/N2O
    Caihong LIN, Li WANG, Yu WU, Peng LIU, Jiangfeng YANG, Jinping LI
    2023, 74(5):  2013-2021.  doi:10.11949/0438-1157.20221542
    Abstract ( 206 )   HTML ( 7)   PDF (3042KB) ( 116 )  
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    Nitrous oxide (N2O) is the third largest greenhouse gas next to CO2 and CH4, and its emission will aggravate the greenhouse effect. However, N2O has a wide range of uses, so its recovery is of great significance. CO2 and N2O coexist in the tail gas from the production of acid via the phenol and cyclohexane processes. Since they have the same kinetic diameter and similar physical properties, it is a great challenge to separate them. In this paper, the effect of monovalent alkali metal cations (Li+, Na+, K+, Cs+) in A-type zeolites on the adsorption and separation performance of CO2/N2O was investigated. Then, the samples were characterized by XRD, ICP-OES, SEM and TGA and the adsorption performance, IAST selectivity and separation performance were studied. The research results show that with the increase of alkali metal cation radius, the adsorption capacity of CO2 and N2O decreases gradually, and CsA almost does not adsorb CO2 and N2O. However, the selectivity of CO2/N2O shows an opposite trend, with KA reaching the highest selectivity (2.6). The penetration experiment results of mixed gases (VCO2/VN2O=50%/50%) also indicate that KA has some CO2/N2O adsorption separation performance.

    Electrochemically switched ion exchange device with serpentine flow field for selective extraction of lithium
    Zheng ZHANG, Yongping HE, Haidong SUN, Rongzi ZHANG, Zhengping SUN, Jinlan CHEN, Yixuan ZHENG, Xiao DU, Xiaogang HAO
    2023, 74(5):  2022-2033.  doi:10.11949/0438-1157.20230303
    Abstract ( 173 )   HTML ( 10)   PDF (3283KB) ( 134 )  
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    An electrochemically switched ion exchange (ESIX) device with single-channel serpentine flow field was assembled by alternately and symmetrically stacking perforated LiMn2O4-based and carbon black (C)-based film coated electrodes, and employed for selective extraction of lithium from simulated brine with high Mg/Li ratio (about 500). Based on this bottom-up serpentine flow field, increasing the number of chambers in the membrane module can enable more lithium ions to be trapped in the simulated brine. Compared with the conventional driving mode of constant voltage, the collaborative driving mode of constant current-constant voltage could effectively improve the lithium extraction performance of the ESIX device. The extraction efficiency of Li+ reached as high as 97.6% in 120 min with a coupled driving mode of 0.8 mA·cm-2-1 V. In addition, X-ray diffraction (XRD) test demonstrated that most of the adsorbed Mg2+ could be removed by rinsing the surface of the film coated electrodes. Therefore, such a novel ESIX device has potential industrial applications for selective separation of lithium from high Mg/Li ratio salt lake brines.

    Design and optimization of membrane-based integration process for advanced utilization of associated gases in N2-EOR oilfields
    Yongyao SUN, Qiuying GAO, Wenguang ZENG, Jiaming WANG, Yifei CHEN, Yongzhe ZHOU, Gaohong HE, Xuehua RUAN
    2023, 74(5):  2034-2045.  doi:10.11949/0438-1157.20221611
    Abstract ( 143 )   HTML ( 5)   PDF (3339KB) ( 152 )  
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    The enhanced oil recovery technology driven by nitrogen, usually abbreviated as N2-EOR, has been widely launched in Chinese oilfields in recent years. As a result, more and more associated gases are discharged with excessive nitrogen concentration. In this instance, the methods to upgrade the unconventional and inferior resources into qualified natural gas for pipeline transmission, with the intent to enhance material utilization and increase economic benefit, are urgently demanded. After meticulously thinking about associated gases’ feature and added value, two crucial missions are accomplished in this research: the high permeable PDMS composite membrane modules are fabricated, the integrated separation process including the shallow condensation and the multi-membrane permeation units are customized. It is anticipated that this novel process can generate chemical feedstock with sufficient ethane and propane recovery, and meanwhile, generate qualified natural gas meeting Chinese National Standard, i.e., GB 17820—2018. Taking a gathering and transportation station in Northwest Oilfield as an implementation case, the coupled process design was carried out for 7000 m3/h associated gas. The simulation results show that the yield of light hydrocarbons is greater than 77.6%, the utilization rate of methane upgrading is greater than 54.4%, and the output of ethylene cracking raw materials is 23604 t/a. The pipeline natural gas output is 18.03×106 m3/a, and the economic benefit is expected to reach 79.0×106 CNY/a, which provides a promising processing approach for the efficient utilization of nitrogen-containing oilfield associated gas.

    Preparation of SA lithium ion sieve membrane and its adsorptive properties
    Lei WANG, Lei WANG, Yunlong BAI, Liuliu HE
    2023, 74(5):  2046-2056.  doi:10.11949/0438-1157.20230061
    Abstract ( 157 )   HTML ( 8)   PDF (4752KB) ( 94 )  
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    SA lithium ion sieve membrane was prepared by blend of the zirconium-coated lithium ion sieve precursor LMZO with sodium alginate (SA) and polyethylene glycol (PEG). A series of experiments for examining its adsorption and cycle stability were carried out, and the adsorption isotherm model and the adsorption kinetics were analyzed. The results showed that the adsorption capacity of SA lithium ion sieve membrane was 1202.17 mg·m-2 when the concentration of SA was 30 mg·ml-1, the content of PEG was 1%, and the amount of loading of LMZO was 55%. After treated with 0.1 mol·L-1 HCl, the extraction of Li+ reached 66.55% and the dissolution loss rate of Mn2+ was only 0.345% in equilibrium. After 10 cycles of adsorption and desorption in brine, the Li+ adsorption capacity was lost only 7.0% (from 1198.40 mg·m-2 to 1116.64 mg·m-2). In brine containing a variety of complex ions such as Na+, K+, Mg2+ and Ca2+, the SA film-like lithium ion sieve has a high selectivity to Li+, and its adsorption process is more in line with the pseudo-second-order kinetic equation and the Langmuir adsorption isotherm model. It is potential to be used in enrichment and recovery of lithium from salt lake brine and other liquid lithium sources.

    Carbon membrane model based on carbon microcrystal structure and its gas separation simulation
    Chenxin LI, Yanqiu PAN, Liu HE, Yabin NIU, Lu YU
    2023, 74(5):  2057-2066.  doi:10.11949/0438-1157.20230249
    Abstract ( 123 )   HTML ( 7)   PDF (8037KB) ( 42 )  
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    The interaction between the gas and the membrane structure greatly affects the separation during the membrane separation of mixed gases. A carbon membrane model with carbon microcrystal structure based on PEK-C-based carbon membrane characterization was constructed by using molecular simulation to investigate the effects of carbon microcrystal pore size and specific surface area of the membrane on CO2/CH4 adsorption and diffusion. The results show that the adsorption sites of gas inside the carbon membrane are related to its microstructure. Gas molecules will be preferentially adsorbed in the pores formed by the random stacking of carbon microcrystals, while the gas adsorption location shifts to the interior of carbon microcrystals when the pore size of carbon microcrystals increases and the specific surface area increases. The molecular shape is the main factor influencing the diffusion when the pore volume of the carbon membrane is more minor, where the linear CO2 is more easily diffused inside the carbon membrane than the ortho-tetrahedral CH4. The carbon membrane has the best gas separation performance with an adsorption separation coefficient of 10.49 when the pore size of carbon microcrystals is 0.493 nm at 30℃ and 100 kPa. As the carbonization temperature increases, the specific surface area of the carbon film increases, which is not conducive to gas separation, indicating that the carbonization temperature should not be too high. The research results not only expand the mechanism of carbon membrane gas separation but also provide a basis for preparing high-performance carbon membranes.

    Desalination performance and mechanism of porous graphene membrane in temporal dimension under mechanical-electrical coupling
    Hao GU, Fujian ZHANG, Zhen LIU, Wenxuan ZHOU, Peng ZHANG, Zhongqiang ZHANG
    2023, 74(5):  2067-2074.  doi:10.11949/0438-1157.20230106
    Abstract ( 114 )   HTML ( 3)   PDF (3276KB) ( 327 )  
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    The temporal selectivity principle of desalination realizes the efficient desalination of porous graphene membranes with large pore size through fluid-solid interface boundary slip. Using the molecular dynamics method, an electric field is applied to the rotating porous graphene reverse osmosis model to further regulate the boundary slip between porous graphene and seawater, and to explore the influence of the electromechanical coupling effect on the desalination performance of porous graphene. The results show that the application of electric field increases the interfacial friction of porous graphene-seawater and decreases the slip velocity of fluid-solid boundary at the supply end. But importantly, the application of electric field can increase the water flux of porous graphene reverse osmosis membrane by about 12% compared with that without the application of electric field, when the salt rejection, though slightly reduced, still remains above 90%. In addition, by analyzing the energy barrier of salt ions passing through nanopores and the average hydrogen bonding number of water molecules, the influence of electric field on the temporal-dimension desalination performance of porous graphene was elucidated in depth. The results extend the application of temporal selectivity principle and will promote the engineering applications of nanoporous graphene membranes in the fields of seawater desalination and water treatment.

    Process system engineering
    Optimization of ternary-distillation sequence based on gradient boosting decision tree
    Shanghao LIU, Shengkun JIA, Yiqing LUO, Xigang YUAN
    2023, 74(5):  2075-2087.  doi:10.11949/0438-1157.20230345
    Abstract ( 143 )   HTML ( 11)   PDF (3641KB) ( 57 )  
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    A machine learning method based on gradient boosting decision tree (GBDT) is proposed for the optimal selection of ternary-distillation process structure. Economic evaluation data of 9 ternary mixtures separated by 7 distillation process structures were used for model training. By applying both traditional decision tree and GBDT models to multiple cases, the results show that the proposed GBDT model has higher prediction accuracy than the traditional decision tree model for both known and unknown ternary mixtures.

    Surface and interface engineering
    Flow simulation and sealing performance test of ultra-high speed dry gas seal under multiple effects
    Junhua DING, Shurong YU, Shipeng WANG, Xianzhi HONG, Xin BAO, Xuexing DING
    2023, 74(5):  2088-2099.  doi:10.11949/0438-1157.20230285
    Abstract ( 168 )   HTML ( 5)   PDF (6534KB) ( 179 )  
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    In order to investigate the law of gas film flow field of ultra-high speed dry gas seals in major key equipment, considering the turbulence effect, inertia effect, real gas effect, and choked flow effect caused by ultra-high speed on the gas film flow field and sealing performance, a turbulence calculation model under multiple effects was constructed. The test verifies the correctness and validity of the theoretical model, and explores the influence of different operating conditions and structural parameters on the sealing performance under the ultra-high speed condition. The results show that the leakage rate increases with the increase of rotational speed and medium pressure under the turbulence effect; the opening force decreases slightly with the increase of rotational speed and then gradually increases, while the opening force increases nonlinearly with the increase of medium pressure. In this example, under ultra-high speed working conditions (50000 r/min, 11 MPa), the optimization results show that the spiral angle should be selected as 16°, and the groove depth should be selected in the range of 6—7 μm. This provides theoretical support for the design and manufacture of ultra-high speed dry gas seals.

    Biochemical engineering and technology
    Basification modification of transthyretin significantly enhances inhibitory effect on amyloid-β protein aggregation
    Wenqi HOU, Yan SUN, Xiaoyan DONG
    2023, 74(5):  2100-2110.  doi:10.11949/0438-1157.20230144
    Abstract ( 162 )   HTML ( 5)   PDF (4677KB) ( 43 )  
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    Alzheimer's disease (AD) is considered to be closely associated with the fibrillar aggregation of amyloid-β protein (Aβ). Therefore, development of efficient inhibitors against Aβ fibrillization is one of the strategies to combat AD. Previous studies have found the inhibition effect of transthyretin (TTR) on Aβ fibrillization through hydrophobic interactions, but it only showed high inhibitory potency at quite high concentrations (150 μg·ml-1). To elevate the potency of TTR on inhibiting Aβ aggregation, this work used the basification method by modifying TTR with ethylenediamine via its reaction with the carboxyl groups on the protein surface. The TTR basification could increase the electrostatic interactions between basified TTR (TTR-B) and the negatively charged Aβ. Studies have shown that TTR-B3 with the highest degree of modification (on average 38.9% of the carboxyl groups on TTR per molecule are converted to amino groups) has a significantly improved ability to inhibit Aβ aggregation. The potency of TTR-B3 was much more efficient than native TTR. TTR-B3 alleviated the toxicity of Aβ aggregates and increased the cultured cell viability from 78% to >90% at 15 μg·ml-1, which was only 10% of native TTR. As compared to basified human serum albumin (HSA-BF), TTR-B3 also worked at significantly lower dosages. TTR-B3 extended the same lifespan of AD nematodes at 75% of HSA-BF, and completely scavenged Aβ plaques in AD nematodes at 45% of HSA-BF. The results indicated that TTR-B3 is a highly effective inhibitor of Aβ aggregation.

    Metabolic engineering of Escherichia coli for chondroitin production
    Chunlei ZHAO, Liang GUO, Cong GAO, Wei SONG, Jing WU, Jia LIU, Liming LIU, Xiulai CHEN
    2023, 74(5):  2111-2122.  doi:10.11949/0438-1157.20221582
    Abstract ( 231 )   HTML ( 9)   PDF (4097KB) ( 122 )  
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    The current research strategies for biosynthesizing chondroitin mainly focus on the construction of synthetic pathways, lacking the fine regulation of the supply of precursor substances, thus limiting the synthesis efficiency of chondroitin. To solve the above problems, in this study, the biosynthetic pathway for chondroitin synthesis was reconstructed and optimized in Escherichia coli by different metabolic engineering strategies, obtaining a microbial cell factory for chondroitin synthesis by fermentation. A complete synthesis pathway for chondroitin was constructed in E. coli BL21 STAR (DE3) by expressing UDP-glucose dehydrogenase (KfoF), UDP-glucosamine isomerase (KfoA) and chondroitin polymerase (KfoC). The supply of chondroitin precursor UDP-GalNAc was improved by optimizing the gene expression levels of aminotransferase (GlmS) and phosphoglucosamine mutase (GlmM). The supply efficiency of chondroitin synthesis precursor UDP-GlcA was improved by optimizing the gene expression level of KfoF. Finally, with the optimized strain E. coli GZ17, chondroitin production was increased to 2.95 g/L in a 5 L fermenter. The above research strategy laid the foundation for the construction and application of chondroitin sulfate strains, and also provided a reference for metabolic engineering to produce other glycosaminoglycans.

    Energy and environmental engineering
    Effect of oil shale addition on ash fusion behavior of Zhundong high-sodium coal
    Lei HUANG, Lingxue KONG, Jin BAI, Huaizhu LI, Zhenxing GUO, Zongqing BAI, Ping LI, Wen LI
    2023, 74(5):  2123-2135.  doi:10.11949/0438-1157.20230114
    Abstract ( 155 )   HTML ( 4)   PDF (6325KB) ( 190 )  
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    The content of alkali metal sodium in Zhundong coal is high, and the fly ash generated during the gasification process leads to problems such as dust accumulation and corrosion in the heat exchanger, which poses a great challenge to the safe and stable operation of the gasifier. Ash fusion behavior is an important parameter to reveal the ash deposition behavior. In this study, oil shale (OS) as an additive with high contents of Si and Al was selected to investigate its effect on the ash fusion behavior of Zhundong high-sodium coal. The results showed that the initial sintering temperature and liquid phase sintering temperature section of Hongshaquan (HSQ) coal and Jiangerkuang (JEK) coal were increased with the increasing OS additions, which alleviate the deposition tendency of coal ash. Minerals analysis illustrated that the addition of OS decreased the anhydrite content and increased the quartz content in raw coal ashes. Meanwhile, sillimanite was formed, which increases the ash fusion temperatures (AFTs) of Zhundong high-sodium coal. For HSQ and JEK coal, when the OS addition was 15% and 20%, the ash deposition can be effectively avoided for the elevated AFTs. Finally, the prediction of deformation temperature and flow temperature was conducted based on artificial neural network and ash compositions.

    Effect of ash chemical components on biomass gasification properties
    Zefeng GE, Yuqing WU, Mingxun ZENG, Zhenting ZHA, Yuna MA, Zenghui HOU, Huiyan ZHANG
    2023, 74(5):  2136-2146.  doi:10.11949/0438-1157.20230009
    Abstract ( 160 )   HTML ( 8)   PDF (3211KB) ( 125 )  
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    Gasification is one of the effective ways to realize the efficient and clean utilization of biomass resources. The chemical composition of ash is the main factor affecting the gasification of biomass. The influence of different inorganic components on the gasification characteristics of biomass is not yet perfect. In this paper, the raw corn stalk sample was first pre-treated by acid washing to remove the original ash compositions. Then the chemical modulus of different inorganic components was severally loaded on the de-ashing feedstock. After that, the role of ash chemical composition was systematically investigated by a rapid fixed-bed gasification reactor. The addition of inorganic fluxes could enhance the real time yield of hydrogen and restrain the release of methane. The alkaline additives (Ca, Fe, Mg, K, Na) tend to increase H2 and CO2 yields, which have a significant effect on the improvement of the syngas quality (H2/CO), especially Fe based additives can improve H2/CO from 0.75 to 1.54. The addition of acidic additives (Si, Al, P) contributes to CO generation and reduces the cold gas efficiency (CGE). In addition, P, Na and K were prone to escape from the solid phase to the gas phase as the volatile fraction, and Si would totally stay in the solid slag. Furthermore, it can be obtained that P is one of the main factors causing ash sintering and melting problems except for Na and K. All the obtained data was meaningful to provide a modifying reference for alleviating ash-related problems, modifying flux addition principle and the efficient utilization of biomass wastes during gasification process.

    Efficient nitrogen and phosphorus removal from domestic wastewater via simultaneous partial nitritation and phosphorus removal combined Anammox
    Jianhua ZHANG, Mengmeng CHEN, Yawen SUN, Yongzhen PENG
    2023, 74(5):  2147-2156.  doi:10.11949/0438-1157.20230162
    Abstract ( 133 )   HTML ( 3)   PDF (2329KB) ( 92 )  
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    To achieve efficient nitrogen and phosphorus removal from domestic wastewater with low carbon to nitrogen ratio, a simultaneous partial nitritation and phosphorus removal (SPNPR) combined anaerobic ammonia oxidation (Anammox) system was established. Long-term operation performance, nutrient conversion route and microbial community structure of the system were investigated. The results indicated that desirable nitrogen and phosphorus removal performance was achieved in the 225-day experiment despite low temperatures, the average nitrogen and orthophosphate removal efficiencies were 90.7% and 94.2%, respectively. Orthophosphate and most of COD in domestic wastewater were removed in the SPNPR reactor, and the average nitrite accumulation ratio and nitrite/ammonium ratio in effluent were 97.2% and 1.23, respectively, this could provide suitable influent for Anammox reaction. Nitrogen in domestic wastewater was mainly removed by the Anammox biofilm reactor, in which Anammox played a major role, denitrification also accounted for 4.8% of the nitrogen removed. The main functional microorganisms in this reactor are Candidatus_Brocadia, denitrifying bacteria and bacteria that can decompose refractory organic matter. Nitrosomonas (2.27%) and phosphate accumulating organisms (5.27%) were dominant in the SPNPR reactor. Nitrite oxidizing bacteria were not detected. In addition, there were some psychrotolerant microorganisms with relatively high abundance, which could secrete cryoprotective extracellular polymeric substances (EPS) at low temperatures. These guaranteed the efficient SPNPR reaction. EPS component analysis further indicated that, the content of EPS increased significantly both in the two reactors at low temperatures, especially the tightly bound EPS with abundant protein, which is adjacent to cell and could protect microorganisms from environmental hazards such as low temperatures, promoting the stable and efficient operation of system.

    Quantum chemical analysis of n-heptane combustion mechanism under O2/CO2 atmosphere
    Chenxi LI, Yongfeng LIU, Lu ZHANG, Haifeng LIU, Jin’ou SONG, Xu HE
    2023, 74(5):  2157-2169.  doi:10.11949/0438-1157.20230018
    Abstract ( 194 )   HTML ( 2)   PDF (3917KB) ( 146 )  
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    In order to study the combustion characteristics of n-heptane under O2/CO2 atmosphere, a C-H combustion mechanism based on the detailed reaction paths of CO2 and H· was proposed. The possible reaction paths of CO2 and H· were analyzed by using density functional theory, and the calculation grids were established according to the actual size of constant volume combustion chamber. The combustion processes of n-heptane under different atmospheres (air, 53%O2/47%CO2, 61%O2/39%CO2) were calculated through C-H mechanism. A constant volume incendiary bomb visualization experiment platform was built to measure the combustion process of n-heptane in different atmospheres. The reaction site of CO2, the reaction energy barrier of CO2+H·CO+·OH, and the flame length were analyzed. The results show that the C-H mechanism can well predict the combustion flame length of n-heptane under O2/CO2 atmosphere, and the maximum error and the average error are 9.60% and 2.42% respectively under 50%O2/50%CO2. The reactivity of oxygen atom of CO2 is higher than that of carbon atom, and the average local ionization energy and molecular surface electrostatic potential at the oxygen ends are 297.72 and -13.08 kcal/mol, respectively. H· can combine with carbon atom and oxygen atom of CO2, the reaction energy barrier are 26.71 and 11.07 kcal/mol, respectively.

    Gaseous pollutants emissions from rotary kiln combustion of municipal sewage sludge
    Yuhao CHEN, Xiaoping CHEN, Jiliang MA, Cai LIANG
    2023, 74(5):  2170-2178.  doi:10.11949/0438-1157.20230096
    Abstract ( 188 )   HTML ( 5)   PDF (2314KB) ( 545 )  
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    The combustion experiments of municipal sludge were carried out on the rotary kiln test bench to study the effect of combustion temperature, particle size of sludge, and residence time in furnace and molar ratio of calcium to sulfur on the emission characteristics of gaseous pollutants during combustion. The results show that with the increase of incineration temperature, the emission concentration of SO2 increases obviously, but the rising trend slows down with the increase of temperature. The emission concentration of NO also increased with the increase of temperature, but the effect was relatively small. With the increase of sludge particle size, the emission concentration of SO2 decreased significantly, while the emission concentration of NO changed little. By reducing the furnace dip angle to prolong the residence time of sludge in the furnace, the emission of NO and SO2 showed an increasing trend, while the concentration of CO emission decreased. However, when the furnace dip angle changed in the range of 1.5°—2.5°, the emission of gaseous pollutants did not change significantly. When the sludge was mixed with lime, the emission concentration of SO2 decreased obviously, and gradually decreased with the increase of Ca/S molar ratio. When Ca/S exceeded 4, the effect of Ca/S molar ratio on emission reduction of SO2 became smaller. The addition of quick lime also reduced the emission concentration of NO, but with the increase of Ca/S molar ratio, the emission concentration of NO rebounded.

    Effect of surfactant E-1310 on the formation of HCFC-141b hydrate under static conditions
    Wenchao XU, Zhigao SUN, Cuimin LI, Juan LI, Haifeng HUANG
    2023, 74(5):  2179-2185.  doi:10.11949/0438-1157.20230166
    Abstract ( 100 )   HTML ( 0)   PDF (1784KB) ( 44 )  
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    Refrigerant hydrate is an ideal cold storage medium, and the cold storage density of 1,1-dichloro-1-fluoroethane (HCFC-141b) hydrate can reach 344 kJ/kg. There are some problems for hydrate formation in static systems, such as difficult to nucleate, slow crystal growth rate, and the randomness of nycleation. In order to promote the formation of hydrate, the effect of isotriosanol polyoxyethylene ether (E-1310), an environmentally friendly nonionic surfactant, on the formation of HCFC-141b hydrate was studied experimentally. The experimental results show that the addition of E-1310 can effectively promote hydrate formation, and the promotion effect is related to the addition amount. It is found that 1.0% (mass) E-1310 is the best addition mass fraction. The induction time of hydrate formation is the shortest, hydrate nucleation is the most stable, and the growth rate and cold storage capacity of hydrate reached the maximum with 1.0% (mass) E-1310 addition. Decreasing or increasing the addition amount of E-1310 cannot further improve the effect of hydrate formation promotion. The micellar effect is the main promoting mechanism of non-ionic surfactant E-1310 on hydrate formation.

    Effect of H2O2 on nitrogen removal and sludge properties in SBR
    Lanhe ZHANG, Qingyi LAI, Tiezheng WANG, Xiaozhuo GUAN, Mingshuang ZHANG, Xin CHENG, Xiaohui XU, Yanping JIA
    2023, 74(5):  2186-2196.  doi:10.11949/0438-1157.20230060
    Abstract ( 112 )   HTML ( 4)   PDF (4387KB) ( 70 )  
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    Hydrogen peroxide (H2O2), as a green oxidant, is widely used in pharmaceuticals, textile, chemical synthesis and other enterprises. The wastewater produced from these enterprises enters the sewage biological treatment system, which affects biological activity and the efficiency of sewage treatment. In the study, the effect of H2O2 on the removal efficiencies of pollutants and catalase activity in the SBR were investigated. The changes of extracellular polymers (EPS) compositions and sludge properties were analyzed, and the decomposition pathway of H2O2 and its influence mechanisms on the activated sludge were explored. The results showed that ·OH and ·O2- produced by low concentration of H2O2 (<90 mg/L) decomposition had a synergistic effect, and removal efficiencies of COD and TN were improved. The sludge surface became rougher, the flocculation particles were larger and sludge flocculation was improved. The contribution of ·OH was higher than that of ·O2-. However, high concentration of H2O2 (>90 mg/L) inhibited the removal of TN, and catalase activity, sludge flocculation and EPS concentration all reduced. When the concentration of H2O2 is 90 mg/L, the removal rate of COD and TN is the highest, and the enzyme activity is the highest. Therefore, the purpose of improving the removal rate of pollutants and sludge flocculation can be achieved by adjusting the concentration of H2O2.

    Sulfidation couples with aging to enhance the reactivity of zerovalent iron toward Cr() in water
    Chengze WANG, Kaili GU, Jinhua ZHANG, Jianxuan SHI, Yiwei LIU, Jinxiang LI
    2023, 74(5):  2197-2206.  doi:10.11949/0438-1157.20230042
    Abstract ( 164 )   HTML ( 11)   PDF (3438KB) ( 75 )  
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    To resolve the deactivation of zero-valent iron (ZVI) by aging effect, the sulfidation was proposed in this work to improve the reactivity of aged ZVI (AZVI). In addition, the coupled effects of sulfidation and aging on the improved performance of ZVI were explored with the help of Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and electrochemistry. Taking the Cr(Ⅵ) as the targeted contaminant, the results showed that the reaction rate of AZVI decreased from 0.0024 min-1 to 0 within an aging period of 0.5—1 d, while the sulfated AZVI (AZVIS) maintained the high reactivity within 0.5—14 d. Based on structural characterization techniques and correlation analysis, it is clear that steric sulfur (S2-/S22-) can improve the electron transfer ability of AZVI to achieve the synergistic removal of Cr(Ⅵ), and analyze the valence states of Fe and Cr before and after the reaction. In the subshell of AZVIS at 20 nm, the correlation coefficients of S2-/S22- with lgkSA were greater than 0.63, further demonstrating that sulfidation can modulate the reactivity of AZVI through the roles of spatial sulfurs (S2-/S22-). In addition, this work further revealed that the surface Fe3O4 could couple the embedded FeS/FeS2 to mediate the electron transfer from Fe0 core for efficient reduction of Cr(Ⅵ) by AZVIS. In general, this study not only helps to guide the interface reconstruction of ZVI, but also is expected to provide theoretical support for the development of ZVI-based technology for water treatment.

    Study on the electrochemical enhanced cobalt-based cathode to activate peroxymonosulfate
    Ruikang LI, Yingying HE, Weipeng LU, Yuanyuan WANG, Haodong DING, Yongming LUO
    2023, 74(5):  2207-2216.  doi:10.11949/0438-1157.20230146
    Abstract ( 176 )   HTML ( 17)   PDF (3830KB) ( 97 )  
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    Co-MOF was grown by hydrothermal method on the surface of nickel foam (NF), and Co3O4@NF was prepared by heat treatment. The structure and morphology of the prepared material were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalyst as a cathode and peroxymonosulfate (PMS) constitute an electrochemically enhanced peroxosulfate activation system EC/ Co3O4@NF/PMS for the degradation of levofloxacin (LEV). The experimental results show that the degradation rate can reach 95.8% in 40 min, and the COD removal is 73.3% in 55 min when pH is 3.0, PMS dosage is 3.5 mmol·L-1, and current density is 4 mA·cm-2, which are significantly better than the system without applying current. The mechanism of the generation of active species in the system was studied. It shows that electric field promotes the activation of PMS to form singlet oxygen 1O2, free radicals SO4- and ·OH mainly by accelerating the Co3+—Co2+ cycle on the surface of the Co3O4@NF cathode. Therefore, both non-free radical and free radical pathways for LEV degradation are enhanced.

    Catalytic degradation of dissolved organic matter in rifampicin pharmaceutical wastewater by Fenton oxidation process
    Quanbi ZHANG, Yijin YANG, Xujing GUO
    2023, 74(5):  2217-2227.  doi:10.11949/0438-1157.20230044
    Abstract ( 199 )   HTML ( 6)   PDF (3680KB) ( 72 )  
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    In this study, Fenton technology (Fe2+/H2O2) was used to treat the actual antibiotic (rifampicin) wastewater, and the effects of initial pH of solution, reaction time, concentration of ferrous ions and oxidant on the degradation performance were explored. Synchronous fluorescence spectra (SFS) combined with two-dimensional correlation spectroscopy (2D-COS) was used to analyze the fluorescence characteristics of dissolved organic matter (DOM) in rifampicin wastewater. The results showed that when the pH was 3, the concentration of H2O2 was 1.4 ml·L-1, and the concentration of ferrous sulfate was 0.5 g·L-1, the degradation rate of COD and TOC in wastewater could reach 73.29% and 82.51% after reaction for 180 min. Meanwhile, the degradation rates of protein-like (PLF), fulvic-like (FLF), humic-like (HLF) and terrestrial humic-like fluorescence (THLF) in rifampicin pharmaceutical wastewater were about 93%, 90%, 83% and 65%, respectively. The result of 2D-COS analysis indicates that fulvic-like substances at 315 nm are more susceptible to the Fenton oxidation system, which can be preferentially degraded. BMG kinetic model has the best fitting effect on experimental data, and its correlation coefficient is above 0.99. The result also suggests the highest reaction rate for the degradation of fulvic-like substances at 315 nm. There is no distinct change in pH during the oxidation reaction. Free radical capture and EPR experiments confirmed that ·OH produced during the reaction was the main active substance.

    Material science and engineering, nanotechnology
    Preparation and adsorption properties of monolayer polyaniline microsphere arrays
    Shaoyun CHEN, Dong XU, Long CHEN, Yu ZHANG, Yuanfang ZHANG, Qingliang YOU, Chenglong HU, Jian CHEN
    2023, 74(5):  2228-2238.  doi:10.11949/0438-1157.20230029
    Abstract ( 167 )   HTML ( 9)   PDF (9604KB) ( 133 )  
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    Nanomaterials with periodic array structures are widely used in material chemistry, energy storage, photonics, molecular sensing, biomedicine and other fields. In this paper, the aminoated polystyrene (aPS) microspheres with the average diameter of 1.45 μm and good monodispersity were prepared by solution method. And then, the aPS microspheres were successfully prepared into a single-layer array structure onto the ordinary non-conductive glass slide by changing the spin coating time, rotation speed, solid content of aPS microspheres, etc. The array structure had the expected monolayer structure, and the aPS microspheres showed a good periodic arrangement. The overall structure can be seen as a periodically arranged microsphere arrays. With this as the synthesis template, polyaniline (PANI) was in-situ grown on the aPS microsphere arrays using the dilute solution synthesis method to obtain PANI@aPS microspheres arrays. The dye rhodamine 6G (R6G) adsorption experiments found that the saturated adsorption capacity of unaminated PS microspheres, aPS microsphere arrays, pure PANI and PANI@aPS microsphere arrays on R6G were about 1.3, 2.0, 5.0 and 7.1 mg/g, respectively, indicating that the PANI@aPS microsphere array has good adsorption to R6G. Compared with the regular arrangement technology such as the pulling film arrangement, this method was more convenient and easier to implement in general laboratories, and it could provide templates for the regular growth of many metal nanoparticles (such as Au and Ag), inorganic compounds and conductive polymers.

    Synthesis and slurry control of manganese oxide powder for direct ink writing electrode
    Hanbing HE, Zhen LIU, Yong CHEN, Xiaofeng WANG, Jing ZENG
    2023, 74(5):  2239-2247.  doi:10.11949/0438-1157.20221688
    Abstract ( 126 )   HTML ( 5)   PDF (4972KB) ( 129 )  
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    The key to improving the quality of direct writing molding products is to prepare a slurry with a high solid content that is suitable for the direct writing process, but the existing research is still lacking in the universal law of slurry regulation. In this work, a series of manganese oxide powders with controllable size were synthesized by hydrothermal method and used in direct writing electrode. The manganese oxide powder was characterized by XRD, SEM and BET, and the rules of solid content selection for different manganese oxide particle sizes were analyzed. The rheological behavior of the related slurries was tested by steady flow method. The results show that the diameter of manganese oxide particles changes in gradient by adjusting the hydrothermal reaction temperature. The suitable solid content of particles of 1.06—1.64 μm increases with the decrease of particle specific surface area, while that of particles of 46.46—91.36 μm decreases with the increase of particle diameter. The slurry prepared according to this rule could be direct ink writing, with smooth extrusion, small volume shrinkage and high mechanical strength.