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Experimental studies on the influence of porosity on membrane absorption process

GAO Jian, REN Zhongqi, ZHANG Zeting, ZHANG Weidong

《化学科学与工程前沿（英文）》 2007年第1卷第4期页码 385-389 doi: 10.1007/s11705-007-0070-0

摘要： Eight kinds of flat membranes with different micro-structures were chosen to carry out the membrane absorption experiments with CO and de-ionized water or 0.1 mol · L NaOH solution as the experimental system. According to experimental results, the membrane pores shape (stretched pore and cylinder pore) and membrane thickness do not affect the membrane absorption process, and the membrane porosity has only little influence on membrane absorption process for slow mass transfer system. However, the influence of porosity on the membrane absorption process became visible for fast mass transfer system. Moreover, the mass transfer behavior near the membrane surface on liquid side was studied. The results show that the influence of membrane porosity on mass transfer relates to flow condition, absorption system and distance between micro-pores, etc.

关键词： de-ionized · L different membrane porosity CO

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Conversion of polyethylene to gasoline: Influence of porosity and acidity of zeolites

《能源前沿（英文）》页码 763-774 doi: 10.1007/s11708-023-0897-1

摘要： Plastic waste is causing serious environmental problems. Developing efficient, cheap and stable catalytic routes to convert plastic waste into valuable products is of great importance for sustainable development, but remains to be a challenging task. Zeolites are cheap and stable, but they are usually not efficient for plastic conversion at a low temperature. Herein a series of microporous and mesoporous zeolites were used to study the influence of porosity and acidity of zeolite on catalytic activity for plastics conversion. It was observed that H-Beta zeolite was an efficient catalyst for cracking high-density polyethylene to gasoline at 240 °C, and the products were almost C₄–C₁₂ alkanes. The effect of porosity and acidity on catalytic performance of zeolites was evaluated, which clearly visualized the good performance of H-Beta due to high surface area, large channel system, large amount accessible acidic sites. This study provides very useful information for designing zeolites for efficient conversion of plastics.

关键词： plastics conversion polyethylene zeolites acidity porosity

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A time−space porosity computational model for concrete under sulfate attack

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0985-7

摘要： The deterioration of the microscopic pore structure of concrete under external sulfate attack (ESA) is a primary cause of degradation. Nevertheless, little effort has been invested in exploring the temporal and spatial development of the porosity of concrete under ESA. This study proposes a mechanical–chemical model to simulate the spatiotemporal distribution of the porosity. A relationship between the corrosion damage and amount of ettringite is proposed based on the theory of volume expansion. In addition, the expansion strain at the macro-scale is obtained using a stress analysis model of composite concentric sphere elements and the micromechanical mean-field approach. Finally, considering the influence of corrosion damage and cement hydration on the diffusion of sulfate ions, the expansion deformation and porosity space−time distribution are obtained using the finite difference method. The results demonstrate that the expansion strains calculated using the suggested model agree well with previously reported experimental results. Moreover, the tricalcium aluminate concentration, initial elastic modulus of cement paste, corrosion damage, and continuous hydration of cement significantly affect concrete under ESA. The proposed model can forecast and assess the porosity of concrete covers and provide a credible approach for determining the residual life of concrete structures under ESA.

关键词： expansion deformation porosity internal expansion stress external sulfate attack mechanical–chemical coupling model

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Tuning porosity of coal-derived activated carbons for CO2 adsorption

《化学科学与工程前沿（英文）》 2022年第16卷第9期页码 1345-1354 doi: 10.1007/s11705-022-2155-1

摘要： A simple method was developed to tune the porosity of coal-derived activated carbons, which provided a model adsorbent system to investigate the volumetric CO₂ adsorption performance. Specifically, the method involved the variation of the activation temperature in a K₂CO₃ induced chemical activation process which could yield activated carbons with defined microporous (< 2 nm, including ultra-microporous < 1 nm) and meso-micro-porous structures. CO₂ adsorption isotherms revealed that the microporous activated carbon has the highest measured CO₂ adsorption capacity (6.0 mmol∙g^–1 at 0 °C and 4.1 mmol∙g^–1 at 25 °C), whilst ultra-microporous activated carbon with a high packing density exhibited the highest normalized capacity with respect to packing volume (1.8 mmol∙cm⁻³ at 0 °C and 1.3 mmol∙cm^–3 at 25 °C), which is significant. Both experimental correlation analysis and molecular dynamics simulation demonstrated that (i) volumetric CO₂ adsorption capacity is directly proportional to the ultra-micropore volume, and (ii) an increase in micropore sizes is beneficial to improve the volumetric capacity, but may lead a low CO₂ adsorption density and thus low pore space utilization efficiency. The adsorption experiments on the activated carbons established the criterion for designing CO₂ adsorbents with high volumetric adsorption capacity.

关键词： coal-derived activated carbons porosity CO₂ adsorption molecular dynamics

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Easily-manufactured paper-based materials with high porosity for adsorption/separation applications in

《化学科学与工程前沿（英文）》 2023年第17卷第7期页码 830-839 doi: 10.1007/s11705-022-2267-7

摘要： A multi-functional porous paper-based material was prepared from grass pulp by simple pore-forming and green cross-linking method. As a pore-forming agent, calcium citrate increased the porosity of the paper-based material from 30% to 69% while retaining the mechanical strength. The covalent cross-linking of citric acid between cellulose fibers improved both the wet strength and adsorption capacity. In addition, owing to the introduction of high-content carboxyl groups as well as the construction of hierarchical micro-nano structure, the underwater oil contact angle was up to 165°. The separation efficiency of the emulsified oil was 99.3%, and the water flux was up to 2020 L·m^–2·h^–1. The theoretical maximum adsorption capacities of cadmium ion, lead ion and methylene blue reached 136, 229 and 128.9 mg·g^–1, respectively. The continuous purification of complex wastewater can be achieved by using paper-based materials combined with filtration technology. This work provides a simple, low cost and environmental approach for the treatment of complex wastewater containing insoluble oil, organic dyes, and heavy metal ions.

关键词： adsorption oil–water separation underwater superoleophobicity wastewater treatment

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The ITZ microstructure, thickness, porosity and its relation with compressive and flexural strength of

《结构与土木工程前沿（英文）》 2022年第16卷第2期页码 191-201 doi: 10.1007/s11709-021-0792-y

摘要： A new insight into the interfacial transition zone (ITZ) in cement mortar specimens (CMSs) that is influenced by cement fineness is reported. The importance of cement fineness in ITZ characterizations such as morphology and thickness is elucidated by backscattered electron images and by consequences to the compressive (F_c) and flexural strength (F_f), and porosity at various water/cement ratios. The findings indicate that by increasing the cement fineness the calcium silicate hydrate formation in the ITZ is favored and that this can refine the pore structures and create a denser and more homogeneous microstructure. By increasing cement fineness by about 25% of, the ITZ thickness of CMSs was reduced by about 30% and F_c was increased by 7%–52% and F_f by 19%–40%. These findings illustrate that the influence of ITZ features on the mechanical strength of CMSs is mostly related to the cement fineness and ITZ microstructure.

关键词： cement fineness interfacial transition zone compressive and flexural strength

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Effect of process parameters on the density and porosity of laser melted AlSi10Mg/SiC metal matrix composite

Omotoyosi H. FAMODIMU, Mark STANFORD, Chike F. ODUOZA, Lijuan ZHANG

《机械工程前沿（英文）》 2018年第13卷第4期页码 520-527 doi: 10.1007/s11465-018-0521-y

摘要：

Laser melting of aluminium alloy—AlSi10Mg has increasingly been used to create specialised products in various industrial applications, however, research on utilising laser melting of aluminium matrix composites in replacing specialised parts have been slow on the uptake. This has been attributed to the complexity of the laser melting process, metal/ceramic feedstock for the process and the reaction of the feedstock material to the laser. Thus, an understanding of the process, material microstructure and mechanical properties is important for its adoption as a manufacturing route of aluminium metal matrix composites. The effects of several parameters of the laser melting process on the mechanical blended composite were thus investigated in this research. This included single track formations of the matrix alloy and the composite alloyed with 5% and 10% respectively for their reaction to laser melting and the fabrication of density blocks to investigate the relative density and porosity over different scan speeds. The results from these experiments were utilised in determining a process window in fabricating near-fully dense parts.

关键词： selective laser melting additive manufacturing mechanical alloying powder metallurgy aluminium metal matrix composite

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我国低孔渗储层天然气资源大型化成藏特征与分布规律

赵文智,王红军,卞从胜,汪泽成,柳广弟

《中国工程科学》 2012年第14卷第6期页码 31-39

摘要：

低孔渗储层天然气资源是目前和未来一段时间我国天然气勘探和开发的主体，具有大型化成藏的特点。集中讨论了这类天然气资源大型化成藏的特征和分布规律，认识到成藏要素具有大型化发育与规模变化的特征，是天然气大型化成藏的基础；薄饼式、集群式成藏是天然气大型化成藏的主要样式；气源灶埋藏期规模“蓄能”和抬升期规模排气是大型化成藏重要气源输入；体积流和扩散流充注是天然气大型化成藏的主要运聚方式。低孔渗储层天然气藏的成藏分布具有近源性，成藏组合以大面积和大范围两种类型为主，成藏类型以地层—岩性圈闭为主，主要分布在海相克拉通盆地古隆起围斜区、陆内坳陷盆地广大斜坡区和向斜区以及前陆盆地缓翼斜坡等地区。低孔渗储层天然气资源大型化成藏认识的提出，提升了我国天然气资源发现潜力，扩展了勘探范围，为客观评价我国天然气主体资源总量和分布、推动有效发现大气田提供了理论基础。

关键词：低孔渗储层大型化成藏体积流扩散流薄饼式集群式

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Continuous modeling of soil morphology —thermomechanical behavior of embankment dams

Bettina ALBERS, Krzysztof WILMANSKI

《结构与土木工程前沿（英文）》 2011年第5卷第1期页码 11-23 doi: 10.1007/s11709-010-0081-7

摘要： Macroscopic modeling of soils is based on a number of properties that refer to the mesoscopic morphology. The most fundamental parameters of this art are: 1) coupling parameters between partial stresses of components and deformations of components, 2) porosities, 3) saturation, and 4) permeability and diffusivity, tortuosity. The main aim of this paper is to present in juxtaposition continuous one-, two-, and three-component models of geomaterials appearing in construction of embankment dams. In particular, the above mentioned features, especially saturation with water and seepage problems, modeling of fluidization yielding piping, and generalizations of the Darcy law and changes of porosity, are presented.

关键词： thermomechanical modeling soil morphology saturation porosity

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堆积床相变储热系统中径向孔隙率振荡分布对热性能的影响 Article

刘红兵, 赵长颖

《工程（英文）》 2021年第7卷第4期页码 515-525 doi: 10.1016/j.eng.2020.05.020

摘要：

由于具有较高的储热能力和传热速率，堆积床相变储热被认为是一种很有潜力的储热方法。在堆积床中，壁面效应会影响相变胶囊的填充结构，从而引起径向孔隙率的振荡。本研究建立了一个基于球体实际堆积过程的三维堆积床相变储热模型，以描述径向孔隙率的振荡分布，并分析了其内部的流动和传热情况。通过在堆积床中沿径向不同位置截取圆柱面，揭示了相变胶囊的排列与径向孔隙率之间的对应关系。径向孔隙率的振荡分布导致换热流体速度呈不均匀分布，因此相变材料的径向温度分布和液相分数分布进一步受到影响。此外，本文讨论了不同的无量纲参数（如管与胶囊的直径比、雷诺数和史蒂芬数）对换热流体和相变材料径向特性的影响。结果表明，不同的直径比对应于不同的径向孔隙率分布。此外，随着直径比的增加，在壁面附近区域换热流体速度显著变化，而中心区域换热流体速度的不均匀性将减小。雷诺数和史蒂芬数对换热流体的相对速度分布有轻微影响，而更高的雷诺数可导致速度成比例地提高，史蒂芬数的增加可加快堆积床相变储热系统的储热过程。

关键词：堆积床相变储热径向孔隙率振荡流动换热传热强化直径比

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Porosity model for flows in CMP

ZHANG Chao-hui, YE Wei, LUO Jian-bin, WEN Shi-zhu

《机械工程前沿（英文）》 2006年第1卷第4期页码 418-423 doi: 10.1007/s11465-006-0050-y

摘要： In an effort to explore the contribution of the pad, which is usually full of pores, to the performance of CMP (chemical mechanical polishing), a three-dimensional flow model of CMP is presented by assuming that the fluids in the porous layer comply with Darcy s law, which states that the flow velocity is proportional to the pressure gradient and inverse proportional to the viscosity. The flow equation is deduced accordingly and, by taking advantage of the multilevel technique and line relaxation technique, numerical simulations are carried out to reveal the relationships between the load capacities and operational parameters (including pivot height, roll angle and pitch angle), under conditions with different porous parameters and different thicknesses of the porous layer. The little porous parameter will lead to a prominent increase of load capability (for instance, the load and the moment predicted), which is still augmented by the thicker layer parameter. This will result in a higher material removal ratio of CMP. A pad full of large pores will be used to deduce load capability, facilitating the free flow of the fluids through the pores. The research will add some insights on the mechanism of the CMP technique.

关键词： multilevel technique three-dimensional proportional research thicker

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Membrane fouling control by ultrasound in an anaerobic membrane bioreactor

SUI Pengzhe, WEN Xianghua, HUANG Xia

《环境科学与工程前沿（英文）》 2007年第1卷第3期页码 362-367 doi: 10.1007/s11783-007-0062-9

摘要： In this study, ultrasound was used to control the membrane fouling online in an anaerobic membrane bioreactor (AMBR). Short-term running experiments were carried out under different operating conditions to explore feasible ultrasonic parameters. The experimental results indicated that when the crossflow velocity was more than 1.0 m/s, membrane fouling could be controlled effectively only by hydrodynamic methods without ultrasound. When ultrasound was applied, an ultrasonic power range of 60–150 W was suitable for the membrane fouling control in the experimental system. The experimental results showed that the membrane fouling was controlled so well that membrane filtration resistance (Σ) could stay at 5 × 10 m for more than a week with the crossflow velocity of 0.75 m/s, which equaled the effect of crossflow velocity of more than 1.0 m/s without ultrasound.

关键词： membrane filtration filtration resistance different feasible ultrasonic anaerobic membrane

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Novel membrane separation technologies and membrane processes

Yanying Wei, Gongping Liu, Jianquan Luo, Libo Li, Zhi Xu

《化学科学与工程前沿（英文）》 2021年第15卷第4期页码 717-719 doi: 10.1007/s11705-021-2053-y

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A critical review on thermodynamic mechanisms of membrane fouling in membrane-based water treatment process

《环境科学与工程前沿（英文）》 2023年第17卷第10期 doi: 10.1007/s11783-023-1729-6

摘要：

● Fundamentals of membrane fouling are comprehensively reviewed.

关键词： Membrane fouling Thermodynamic mechanism XDLVO theory Flory-Huggins theory Fouling migration

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A review on membrane distillation in process engineering: design and exergy equations, materials and

《化学科学与工程前沿（英文）》 2022年第16卷第5期页码 592-613 doi: 10.1007/s11705-021-2105-3

摘要： One of the problems that most afflicts humanity is the lack of clean water. Water stress, which is the pressure on the quantity and quality of water resources, exists in many places throughout the World. Desalination represents a valid solution to the scarcity of fresh water and several technologies are already well applied and successful (such as reverse osmosis), producing about 100 million m³·d⁻¹ of fresh water. Further advances in the field of desalination can be provided by innovative processes such as membrane distillation. The latter is of particular interest for the treatment of waste currents from conventional desalination processes (for example the retentate of reverse osmosis) as it allows to desalt highly concentrated currents as it is not limited by concentration polarization phenomena. New perspectives have enhanced research activities and allowed a deeper understanding of mass and heat transport phenomena, membrane wetting, polarization phenomena and have encouraged the use of materials particularly suitable for membrane distillation applications. This work summarizes recent developments in the field of membrane distillation, studies for module length optimization, commercial membrane modules developed, recent patents and advancement of membrane material.

关键词： membrane distillation recent developments heat and mass transfer wetting membrane material