Two‐dimensional simulation of hollow fiber membrane fabricated by phase inversion method

In the steady fabricating process, two‐dimensional hollow fiber membrane near the spinneret was numerically simulated using the finite element method (FEM). The unknown positions of free surface and moving interface were calculated simultaneously by the velocity and pressure fields. The effects of seven relevant parameters, i.e., inertia term, gravity term, dope flow rate, bore flow rate, dope viscosity, tensile force, end velocity and non‐Newtonian on the velocity and diameter profile were studied. On the basis of the simulated results, the inertia term in hollow fiber‐spinning process was safely neglected in low speed, while the effect of gravity was not be neglected. Besides, the outer diameter of the fibers increased with an increase of dope flow rate and bore flow rate; Large tensile force or large end velocity could cause large deformation in the air gap; larger viscous dope solution tended to make less deformation in the air gap. It was found that an increase of the dope flow rate at small dope flow rate resulted in an increase of the inner diameter, while at large dope flow rate, it decreased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2067–2074, 2006     

BaTiO3-based thermistor hollow fibers prepared using a phase inversion spinning process for energy efficient gas sorption

Positive temperature coefficient of resistivity (PTCR) hollow fibers that exhibit self-regulating heating characteristics have potential applications in temperature-swing adsorption systems (TSA), such as CO₂ recovery and drying of compressed air. La-doped BaTiO₃ hollow fibers displaying a PTCR effect were produced by phase inverting a casting solution consisting of N-methly-2-Pyrrolidone, polymethyl methacrylate, polyvinylpyrrolidone, BaTiO₃, TiO₂, and La₂O₃ through a spinneret into a coagulating waterbath. This was followed by polymer debinding, high temperature sintering between 1350?1400 °C and annealing in air at 1175 °C to produce hollow fibers of the composition Ba_0.9975La_0.0025TiO₃. Hydrothermal synthesis was implemented to deposit an adsorbent porous zeolite X layer within the hollow fiber lumen, which was confirmed by electron dispersive X-ray spectroscopy and CO₂ adsorption at 0 °C. Hence, these materials can be applied to energy efficient TSA gas separation processes. The results are discussed in terms of hollow fiber microstructure, adsorption characteristics and electrical properties.     

Performance control of dead-end tubular membranes fabricated with a modified phase inversion casting method

A modified phase inversion casting method is employed for the formation of dead-end tubular membrane shape in a single step. Ce_0.9Gd_0.1O_1.95-δ (CGO)-Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) composites are applied as the membrane material. Performance of the membrane is optimised by adjusting the processing conditions in the fabrication process. Long finger-like channels, which were found to promote oxygen permeation flux without decrease of the membrane mechanical strength, were obtained in the dead-end tubes by adjusting the ceramic loadings of the casting slurries. Slurries with lower viscosity provided reduced resistance for the channel growth during the phase inversion in water. The performance of the dual-phase membranes with varied CGO:BSCF ratios were compared. The membranes containing more BSCF show higher oxygen permeation fluxes with helium as sweep gas. It was also verified that CGO content played an important role in enhancing the mechanical strength of the CGO-BSCF membranes.     

Preparation and characterization of porous PDMS beads for oil and organic solvent sorption

In this article, poly (dimethyl siloxane) (PDMS) porous beads were prepared by suspension polymerization method using n‐octane and carbon tetrachloride (CCl₄) as diluents and pore formation agents. The apparent density, porosity and other characteristics were characterized. The absorption experiments showed that the porous PDMS beads exhibited more absorption capacity and faster absorption rate toward oils than the nonporous or oligoporous PDMS beads did, moreover they are of remarkable stability and recyclability, which could provide a path to absorb the oils floating on water. POLYM. ENG. SCI., 54:2965–2969, 2014. © 2014 Society of Plastics Engineers     

Synthesis of alginate beads filled with nanohydroxyapatite: An efficient approach for fluoride sorption

Nanohydroxyapatite (n‐HAp) powder is a promising adsorbent material with high defluoridation capacity (DC); however, it causes pressure drop during field applications. To overcome such problems and utilize the advantages of n‐HAp, it is aimed to prepare n‐HAp in a usable bead form with the support of alginate (Alg) biopolymer. n‐HApAlgLa composite beads were synthesized by introducing n‐HAp powder in Alg polymeric gel, and the resulting solution was dropped into La³⁺ ions for crosslinking. Defluoridation experiments were carried out in batch mode to optimize various influencing parameters like contact time, pH, challenger anions, initial fluoride concentrations, and temperature. The beads were characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy with energy‐dispersive X‐ray analyzer analysis. The sorption process was explained using diverse isotherms and kinetic models. The values of thermodynamic parameters indicate that the nature of fluoride is spontaneous and endothermic in nature. In field studies, n‐HApAlgLa beads reduce the fluoride concentration below the tolerance limit. The regeneration and reusability studies were proposed to effectively use the sorbent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41937.     

Heavy oil sorption and recovery by using carbon fiber felts

On fibrous carbon materials, including activated carbon fibers, sorption capacity for heavy oils, less viscous A-grade and more viscous C-grade, was determined. Sorption capacity depended strongly on their bulk density; the correlation was the same as that found previously on exfoliated graphite and carbonized fir fibers. On carbon fiber felts, excellent recycling performance was observed, though sorption capacity was not so high as on exfoliated graphite and carbonized fir fibers. By filtration under suction, about 90% of sorbed A-grade heavy oil could be recovered and no decrease in sorption capacity was detected even after eight cycles. By washing with solvents, n-hexane for A- and C-grade oils and A-grade oil for C-grade oil, almost 100% recovery with no marked reduction in sorption capacity was found for each cycle. For the felts of PAN-based carbon fibers, rather severe operations for oil recovery, centrifugation and squeezing with twisting, could be applied without pronounced decreases in sorption capacity and recovery ratio.     

Metal ion sorption by chitosan–tripolyphosphate beads

Heavy metal removal from wastewater is crucial for the proper management of discharged water from mining operations. This residual water is typically unusable for other purposes such as for human/animal, crop, or industrial consumption. Eco‐friendly adsorption materials are necessary to ensure the sustainable treatment of this wastewater. Therefore, the sorption of Cu(II), Cd(II), Pb(II), and Zn(II) ions onto chitosan–tripolyphosphate (CTPP) beads was investigated using real mining wastewater and prepared ion metal solutions. The effects of pH, contact time, temperature, selectivity, and maximum sorption capacity in successive batches at different concentrations were studied. The optimum sorption of cations, except for copper (pH 3) was found at pH 5. Equilibrium in the adsorption of all metals was reached at 24 h of contact. Studies of the maximum sorption capacity at different concentrations showed that the CTPP beads could adsorb 158, 55, 47, and 47 mg/g of Pb(II), Cu(II), Cd(II), and Zn(II), respectively. Experimental data for the sorption of Pb(II) were optimally correlated with the Langmuir model. The thermodynamic parameters such as the changes in enthalpy (ΔH⁰), entropy (ΔS⁰), and free energy (ΔG⁰) were determined. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45511.     

Whiskerization of carbon beads by vapor phase growth of carbon fibers to obtain sea urchin-type particles

Whiskerization of sulfur-containing hard carbon beads with carbon fibers has been examined to prepare sea urchin-type particles. Propylene was used as a source material for the fiber growth and decomposed at 1000°C for 2 hr. Sulfur-catalyzed carbon fibers 4–6 μm in diameter and 90–120 μm long formed with a density of 400–550 per bead on the surfaces of carbon beads containing ≥ 2.5 wt% sulfur. These beads were prepared by carbonization of styrene/divinylbenzene copolymers sulfonated with fuming sulfuric acid. Very few, if any, fibers grew on beads from copolymers sulfonated with chlorosulfuric acid, probably because of lower sulfur contents (<2.5 wt%) and/or inhibition by residual chlorine.     

Pore architectures and oil absorption behavior of porous mullite beads fabricated via dripping-ice templating

Porous mullite beads with a good spherical shape and a uniform size distribution of about 1.2 mm were fabricated by ice-templating in combination with dripping methods. These internal pore structures exhibited a radially oriented laminar channel from the center of the sphere to the surface. With the decreasing of freeze temperature to −196°C, the thickness of pore walls and the width of pore decreased. The mullite grain morphology in the pore wall was also influenced by the frozen temperature. High aspect ratio mullite grain was formed in the pore wall of beads frozen at −25°C, while low aspect ratio mullite whiskers constituted the pore wall of beads frozen at −196°C. In addition, the obtained porous mullite beads exhibited a good oil adsorption performance under capillary force for kerosene, edible oil, and motor oil with adsorption values of 3.37, 4.07, and 4.04 g/g, respectively.     

Study of carbon fibre sorbents by the method of dynamic sorption

A rapid method of studying the characteristics of carbon fibre sorbents by dynamic sorption was developed. It was shown that in the 40–200°C temperature range, equilibrium between the sorbed and vapor phases of benzene is attained in the selected desorption conditions. The results obtained are in agreement with the static sorption data and can be used to comparatively evaluate the porosity of CFS.Avtor Scientific and Industrial Association, Mytishchi. Translated from Khimicheskie Volokna, No. 6, pp. 39–41, November–December, 1995.     

Assessment of sorption kinetics of carbon nanotube-based composite foams for oil recovery application

Sorption kinetics of pollutant oils, such as kerosene, virgin naphtha, crude oil, and pump oil, into porous siloxanic foams filled with carbon nanotubes (CNTs) are investigated. Both, pristine and functionalized, CNTs are used as foam fillers. Among all, the foam filled with pristine CNT shows a poor affinity with water and high sorption rate in light oils, in which it achieves the highest absorption values (7991 mg g⁻¹ after 660 s and 6685 mg g⁻¹ after 420 s, respectively, in virgin naphtha and kerosene). The kinetic data are described by the pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models. Results show that chemisorption processes are rate limiting the sorption step. In fact, pseudo-second order model better represents the equilibrium isotherm data. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47374.     

Optimisation of carbon nanotube ink for large-area transparent conducting films fabricated by controllable rod-coating method

Single-walled carbon nanotubes (SWCNTs) were dispersed in water with the help of surfactants to achieve high concentration SWCNT ink. SWCNT transparent conducting films (TCFs) were fabricated by rod coating using the SWCNT ink. A combination of two surfactants provided optimal rheological behaviour, which produced uniform films by preventing dewetting and rupture of SWCNTs during drying. The combination led to a dramatic increase of shear viscosities but no change of their wettability. The viscosity of SWCNT ink was controlled by the ratio of two surfactants. The thickness of SWCNT films could be easily varied by controlling both the concentration of SWCNT ink and the size of the wire-wound rod. The produced uniform SWCNT-TCFs treated by nitric acid have a relatively low sheet resistance of ∼80 Ω sq⁻¹ at 80% transmittance. The performance has a wide range of applied interest for touch screen and flexible electronics.     

Biporous polymeric beads fabricated by double emulsification for high‐speed protein chromatography

Rigid biporous beads (BiPB) were fabricated by double emulsification. An aqueous suspension of superfine calcium carbonate granules and organic solvent were used as porogenic agents to create superpores and micropores, respectively. The polymerization of monomers, glycidyl methacrylate, and ethylene glycol dimethacrylate was initiated with benzoin ethyl ether by ultraviolet irradiation. Modified with diethylamine (DEA), the BiPB were derivatized into an anion‐exchange medium (which is denoted as DEA–BiPB). The DEA–BiPB with an average diameter of 46.3 μm was characterized to possess two types of pores, that is, micropores (20–200 nm) and superpores (500–5300 nm). Flow hydrodynamic experiments showed that the DEA–BiPB column had a smaller backpressure than that of the conventional microporous beads column at a given flow rate. The static adsorption capacity of the DEA–BiPB was close to that of the DEA–MiPB for bovine serum albumin. However, frontal analysis demonstrated that the dynamic binding capacity of the DEA–BiPB column was two times higher than that of the DEA–MiPB at a flow rate of 1800 cm/h. Moreover, the purification of the molecular chaperone GroEL was carried out with the DEA–BiPB column at two flow rates (150 and 1500 cm/h). This showed that the GroEL purification was nearly the same at the two flow rates tested. These results indicate that the DEA–BiPB column is promising for high‐speed protein chromatography. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 17–23, 2007     

相转化法制备氧化钇稳定氧化锆中空纤维陶瓷膜

采用相转化和烧结相结合的方法制备了氧化钇稳定氧化锆(YSZ)中空纤维陶瓷膜，研究了铸膜液中YSZ粉末含量和烧结温度对中空纤维陶瓷膜的微观结构和性能的影响。结果表明，YSZ中空纤维陶瓷膜的不对称结构包含指状结构和海绵状结构，YSZ含量会影响两种结构的比例，烧结则会引起微观结构的致密化。在铸膜液配比为m(YSZ):m(PSF):m(NMP)=5.0:1:4，烧结温度为1200 ℃的条件下制备出性能良好的中空纤维陶瓷膜，其纯水通量为2.33 m3/(m2·h·MPa)，抗弯强度为134.5 MPa。     

Characteristics of phenylalanine imprinted membrane prepared by the wet phase inversion method

A phenylalanine imprinted membrane without a sponge layer containing macrovoids was prepared by the wet phase inversion method. The structure of the phenylalanine imprinted membrane prepared by an in-situ implanting procedure was denser than that of the membrane prepared by post implanting. Consecutive washings with distilled water and acetic acid solution removed nearly all of the template molecules from the membrane prepared by the post implanting procedure, although much of the template molecules remained in the membrane prepared by in-situ implanting. The removal of the template molecules from the membrane increased the population of the free COOH groups but reduced that of the dimerized COOH groups in the membrane. A D-Phenylalanine imprinted membrane prepared by post implanting selectively adsorbed D-phenylalanine from a racemate solution, where the adsorption selectivity reached 4.79. A D-phenylalanine imprinted membrane prepared by in-situ implanting exhibited an inverse adsorption affinity.     

Effect of additives on mechanical properties of oxidation-resistant carbon/carbon composite fabricated by rapid CVD method

The optimum composition of additives was obtained by the orthogonal design test method for oxidation-resistant carbon/carbon composites (C/C) fabricated by the rapid CVD method. The effect of additives on mechanical properties was examined. The additives used in this test included silicon carbide, silicon nitride, and metal borides. Additives doped into the matrix of C/C increase not only the initial oxidation temperature from 400 to 657°C (64%), but also its flexural strength from 121 to 254 MPa (110%), and flexural modulus from 25 to 45 GPa (96%). The increase of mechanical properties is considered to be due to the formation of a metallic carbon–boron compound in the microstructure.     

Droplet size and stability of nano-emulsions produced by the temperature phase inversion method

We studied the formation and stability of n-decane in water nano-emulsions produced by the phase inversion temperature (PIT) emulsification method using polyoxyethylene lauryl ether as surfactant. The results obtained indicate that the droplet size and size distribution are strongly dependent on the methods of heating and cooling, and on the final temperature to which the mixture is cooled after phase inversion. Importantly, there exists an optimum storage temperature, at which the nano-emulsions are most stable, and develop ultra-small droplet sizes, ranging from 35 nm to 54 nm, with low polydispersity indices (0.2). This optimum temperature is about 20 °C below the PIT, and dependent on the surfactant concentration. Any departure in temperature from the optimum would result in increases in droplet sizes, polydispersity and instability by Ostwald ripening. Furthermore, nano-emulsions destabilized after a long period of storage at different temperatures can be rejuvenated simply by equilibration for a few minutes at the optimum temperature.     

Mechanism of selenium sorption by activated carbon

Selenium, along with mercury and halides, represents one of the most volatile trace metallic emissions from coal‐fired combustors and utility boilers. This study investigates the potential of activated carbon in capturing gas phase selenium species in the low temperature range (125°C to 250°C) and elucidates the mechanism of interaction between selenium species and activated carbon. Selenium dioxide is chosen as the representative selenium species and experimental investigations are carried out in a differential bed reactor to illustrate the mechanism of SeO₂ and carbon Interaction, Activated carbons with different structural properties are studied as adsorbents for selenium dioxide capture at low temperature. The capture mechanism is found to involve both physical and chemical adsorption in the low temperature range. At 125°C, about 1.5 wt% of selenium is captured at equillbrium. Carbon surface analyses and XPS studies confirm the presence of both elemental and oxide forms of selenium on the surface suggesting partial reduction of selenium dioxide to elemental selenium at carbon surface.     

Electrical conductivity and mechanical properties of carbon black modified polyolefinic blends influenced by phase inversion

Electrically conductive polymer composites (CPCs) containing a carbonaceous filler and a polymeric matrix have been widely researched and utilized. Immiscible polymers are often used as the matrix of CPCs, which leads to segregated structures, hence low percolation threshold and good conductivity of a material. Polymeric blends often show low mechanical properties due to the lack of affinity of the resins. A way to improve toughness of a CPC and maintain good electrical properties is mixing two immiscible yet compatible resins. In our case one of them was polyethylene and the other was an olefinic conductive thermoplastic elastomer. In this study, a correlation between conductivity, mechanical properties, and morphology of conductive blends was analyzed. Results of tensile test, conductivity measurements, and differential scanning calorimetry were juxtaposed with information of phase morphology of the blends. A relationship of drastic changes of different properties of the blends and phase inversion point was found. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45512.     

超临界二氧化碳相转化技术制备组织工程支架研究进展

组织工程支架是组织工程研究的关键要素之一。然而,传统制备方法存在操作条件复杂或有机溶剂残留量高等问题。本文基于超临界二氧化碳相转化技术操作条件温和、可以将相分离与干燥过程合二为一、有效地去除有机溶剂等优点,简要介绍了超临界二氧化碳相转化技术中应用的组织工程支架材料,具体阐述了制备出具有致密无孔结构、孔洞结构以及三维纳米纤维结构的组织工程支架的研究进展。随后对其目前存在的不足,如该项技术缺少系统的理论研究、部分制备出的支架不利于传质、负载生长因子和细胞粘附等问题提出了可能的解决方案。最后对超临界二氧化碳相转化技术制备具有类似细胞外基质结构和功能、孔洞相互贯通、微观粗糙纳米纤维表面的组织工程支架进行了展望。