Description of butanol aqueous solution transport through commercial PDMS pervaporation membrane using extended Maxwell–Stefan model

The mass transport of components during the pervaporation of binary butanol aqueous solutions using commercial PDMS membranes has been investigated. A simplified approach of the Maxwell–Stefan model was extended to include the effect of membrane swelling and temperature on the diffusion coefficients and sorption properties. Partial permeate fluxes obtained at different temperatures and concentrations have been fitted to determine the extended model parameters. The sorption properties and diffusion coefficients of components have been estimated using fitted parameters. Predicted values of the solubility and diffusivity were used to calculate and compare the permeability of the components under different operating conditions.

Abbreviations: HPLC - High performance liquid chromatography; MS - Maxwell–Stefan; PDMS - Polydimethylsiloxane; SEM - Scanning electron microscope     

Preparation,characterization, and performance evaluation of LTA zeolite–ceramic composite membrane by separation of BSA from aqueous solution

Using low-cost clay supports as substrates, ceramic–LTA zeolite composite membranes (Z1–Z4) were fabricated with hydrothermal crystallization. The composite membranes were achieved with variations in the sequential zeolite depositional steps. For Z1–Z4 membranes, various characterization techniques such as thermogravimetric (TG), particle size distribution (PSD), X-ray diffraction (XRD), and field emission scanning electron microscopic (FE-SEM) analysis were applied. For the Z1–Z4 membranes, the pure water permeability, porosity, and average pore size varied from 1.22 × 10^?7 to 1.19 × 10^?8 m³/m²s kPa, 30–23%, and 215–76 nm, respectively. For the Z4 membrane, ultrafiltration experiments were conducted at a pH of 2.5 and transmembrane pressure differential of 207 kPa using aqueous bovine serum albumin (BSA) solutions. The optimal flux and rejection correspond to 4.54 × 10^?7 m³/m²s and 80%, respectively.     

Cellulose acetate–silica fume membrane: characterization and application for separation of starch and maltose

Maltose is one of the starch derivatives. Maltose can be produced by starch hydrolysis using any kind of hydrolytic process. One of the methods to separate a mixture of both compounds is using porous membrane. In this research, a novel type of hybrid membrane was prepared from a mixture of cellulose acetate and silica fume. Silica fume is widely used in the domain of construction as cement material, whereas in this research silica fume was successfully used as membrane material. Various compositions of membrane dope solutions were prepared for obtaining the membranes used for separation of starch and maltose. Such synthesized membranes demonstrate a good performance in separation processes. The best performance is achieved when the composition of cellulose acetate in membrane dope solution is 15 % (w/w) in N,N-dimethylacetamide solvent and the mass ratio between cellulose acetate and silica fume is 4:1. For this composition, the rejection of membranes towards starch and maltose is 87 and 2 %, respectively, at working pressure of 3 bar and compaction time of 2 h. Infrared spectrum indicates no new peaks are found compared to raw materials’ spectral peaks. Thus, it can be concluded that the interaction between the cellulose acetate and silica fume is merely a physical type. From the observation of cross-sectional SEM images, we can remark that the morphology of such a membrane is porous. X-ray diffractogram indicates that the synthesized membranes are amorphous.     

Exclusive and fast water channels in zwitterionic graphene oxide membrane for efficient water–ethanol separation

Graphene oxide (GO) membranes have shown great prospects as the next-generation membranes to tackle many challenging separation issues. However, the employment of GO membranes remains difficult for the precise separation of molecules with strong coupling effect and small size discrepancy such as water–ethanol. Herein, a new strategy of constructing exclusive and fast water channels in GO membrane was proposed to achieve high-performance water–ethanol separation via the synergy between zwitterion-functionalized GO and hydrophilic polyelectrolyte. The as-formed ordered and stable channels possess high-density ionic hydrophilic groups, which benefit from inhibiting the strong coupling between water and ethanol, facilitating the fast permeation of water molecules while suppressing ethanol molecules. As a result, the ultrathin GO-based membrane acquires exceptionally high separation performance with a flux of 3.23 kg/m² h and water–ethanol separation factor of 2,248 when separating water–ethanol (10 wt%/90 wt%) mixture at 343 K. This work paves a feasible way to construct 2D channels for the high-efficiency separation of strong-coupling mixtures.     

Fabrication and characterization of poly(vinylidene fluoride)–polytetrafluoroethylene composite membrane for CO2 absorption in gas–liquid contacting process

The wetting resistance of poly(vinylidene fluoride) (PVDF) membrane is a critical factor which determines the carbon dioxide (CO₂) absorption performance of the gas–liquid membrane contactors. In this study, the composite PVDF–polytetrafluoroethylene (PTFE) hollow fiber membranes were fabricated through dry-jet wet phase-inversion method by dispersing PTFE nanoparticles into PVDF solution and adopting phosphoric acid as nonsolvent additive. Compared with the PVDF membrane, the composite membranes presented higher CO₂ absorption flux due to their higher effective surface porosity and surface hydrophobicity. The composite membrane with addition of 5 wt % PTFE in the dope gained the optimum CO₂ absorption flux of 9.84 × 10⁻⁴ and 2.02 × 10⁻³ mol m⁻² s⁻¹ at an inlet gas (CO₂/N₂ = 19/81, v/v) flow rate of 100 mL min⁻¹ by using distilled water and aqueous diethanolamine solution, respectively. Moreover, the 5% PTFE membrane showed better long-term stability than the PVDF membrane regardless of different types of absorbent, indicating that polymer blending demonstrates great potential for gas separation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47767.     

Synthesis of gelatin–PVA adsorbent and its application in the separation of ginkgo flavonol glycosides and terpene lactones

Spherical adsorbents derived from the glutaraldehyde cross-linked hybrid of gelatin and polyvinyl alcohol (PVA) were synthesized, and their adsorption selectivity for ginkgo flavonol glycosides and terpene lactones was also investigated in detail. An adsorbent with an appropriate gelatin content can selectively adsorb flavonol glycosides with a high adsorption capacity based mainly on hydrogen bond interactions, while showing only a fairly low adsorption capacity for terpene lactones. A much higher adsorption affinity of flavonol glycosides than that of terpene was calculated from the adsorption isotherms. Thus, a simple preparative separation procedure for ginkgo flavonol glycosides and terpene lactones from a ginkgo leaf was established. An enriched extract containing flavonol glycosides of up to 60% and terpene lactones as low as 0.2% and an extract with a terpene lactones content up to 30% was prepared by this method, respectively.     

Preparation of polyacrylamide–montmorillonite nanocomposite and its application in Cr(III) adsorption

The polyacrylamide–montmorillonite “water in water” (PAM-MMT W/W) emulsion was prepared by dispersion polymerization method in the presence of organo-montmorillonite (OMMT). Based on the analysis of the polymerization process, the structure of material was investigated using thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy experiments. Here, the dispersion was determined to be a blend of PAM W/W emulsion and PAM network interspersed by MMT particles, this unique structure of the material was considered to provide better adsorption ability compared to PAM without MMT. Therefore, a PAM-MMT adsorbent was made from the PAM-MMT W/W emulsion, and its adsorption capacity toward Cr(III), one of the heavy metal pollutants from the tannery waste was investigated. The PAM-MMT nanocomposite was demonstrated to have good Cr(III) removal performance, the maximum adsorption capacity of the nanocomposite was found to be 59.74 mg/g at a pH of 5.5 and temperature of 70°C. Results show that pseudo-second-order kinetic model and Langmuir isotherm were applicable for Cr(III) adsorption.     

Plasma grafting montmorillonite/iron oxide composite with β-cyclodextrin and its application for high-efficient decontamination of U(VI)

β-Cyclodextrin (CD) was grafted onto montmorillonite/iron oxides to prepare a novel magnetic CD/MMT/iron oxide composite by low-temperature plasma technology, and applied to remove U(VI) from aqueous solutions. The sorption irreversibility was attributed to inner-sphere binding of U(VI) on CD/MMT/iron oxide surface sites. The thermodynamic parameters indicated that the sorption of U(VI) on CD/MMT/iron oxide was an endothermic and spontaneous process. The maximum sorption capacity of U(VI) on CD/MMT/iron oxide was considerably higher than that of U(VI) on other reported materials. The CD/MMT/iron oxide can be potentially used as a cost-effective material for the purification of actual U(VI)-bearing effluents.     

pH-Sensitive performance of dextran–poly(acrylic acid) copolymer and its application in controlled in vitro release of ibuprofen

Dextran–poly(acrylic acid) copolymers (D-A) are prepared through copolymerizing of acrylic acid (AA) with dextran. Their structural properties and performances are characterized using various methods. The results indicate that the carboxyl groups of poly(acrylic acid) strongly interact with the proton acceptors of glucose units in dextran, and the effects of AA/dextran molar ratio on the pH sensitivity of obtained copolymers are remarkable. The D-A copolymer shows a smart pH response, specifically, shrinkage in a low pH medium and swelling at high pH. The potential application of D-A copolymer as a drug delivery matrix is explored using ibuprofen as a model drug.     

Removal of Cd(Ⅱ) from dilute aqueous solutions by complexation–ultrafiltration using rotating disk membrane and the shear stability of PAA–Cd complex

Removal of cadmium(Ⅱ) ions from dilute aqueous solutions by complexation–ultrafiltration using rotating disk membrane was investigated. Polyacrylic acid sodium(PAAS) was used as complexation agent, as key factors of complexation, pH and the mass ratio of PAAS to Cd~(2+)(P/M) were studied, and the optimum complexation–ultrafiltration conditions were obtained. The effects of rotating speed(n) on the stability of PAA–Cd complex was studied with two kinds of rotating disk, disk Ⅰ(without vane) and disk Ⅱ(with six rectangular vanes) at a certain range of rotating speed. Both of the rejection could reach 99.7% when n was lower than 2370 r·min~(-1) and 1320 r·min~(-1), for disk I and disk Ⅱ, respectively. However, when rotating speed exceeds a certain value,the critical rotating speed(n_c), the rejection of Cd(Ⅱ) decreases greatly. The distribution of form of cadmium on the membrane was established by the membrane partition model, and the critical shear rate(γ_c), the smallest shear rate at which the PAA–Cd complex begins to dissociate, was calculated based on the membrane partition model and mass balance. The critical shear rates(γ_c) of PAA–Cd complex were 5.9 × 10~4 s~(-1), 1.01 × 10~5 s~(-1),and 1.31 × 10~5 s~(-1) at pH = 5.0, 5.5, and 6.0, respectively. In addition, the regeneration of PAAS was achieved by shear induced dissociation and ultrafiltration.     

Structure–reactivity studies on the polymerization and crosslinking behavior of tri(propylene glycol) diacrylate in aqueous solutions

Radiation induced polymerization of tri(propylene glycol) diacrylate (TRPGDA) has been investigated by steady state and pulse radiolysis (PR) techniques. Reactions of TRPGDA with primary species of water radiolysis such as OH radical, ${\text{e}}_{\text{aq}}^{-}$, H atom and oxidizing species like ${\text{N}}_3^{\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/rad"></mglyph>}}$ are reported. The rate constant values of 2.9 ± 0.19 × 10⁹ dm³ mol⁻¹ s⁻¹ and 1.3 × 10⁹ dm³ mol⁻¹ s⁻¹ were obtained for the reaction of TRPGDA with ${\text{e}}_{\text{aq}}^{-}$ and OH radical, respectively. The spectrum of hydrated electron was found to be pH dependent whereas the spectrum of transient species formed with OH radicals was found to be unaffected with pH variation. The radical anion formed, preferentially undergoes propagation. The OH adduct was found to be an α-carboxyalkyl radical with an absorption maximum at 300 nm. Steady state investigation reveals a significant dependence of the polymerization behavior on the nature of radiolytic species present and on the ambient environment. A very efficient function of TRPGDA as a crosslinker in poly(vinyl alcohol) matrix was demonstrated by the reduction in D_gel value from 1.1 kGy to 0.2 kGy for crosslinking in presence of 1% TRPGDA.     

Three-liquid-phase extraction and separation of V(V) and Cr(VI) from acidic leach solutions of high-chromium vanadium–titanium magnetite

A new method by liquid–liquid–liquid three phase system, consisting of acidified primary amine N1923(abbreviated as A-N1923), poly(ethylene glycol)(PEG) and (NH_4)_2SO_4 aqueous solution, was suggested for the separation and simultaneous extraction of V(V) and Cr(VI) from the acidic leach solutions of highchromium vanadium–titanium magnetite. Experimental results indicated that V(V) and Cr(VI) could be selectively enriched into the A-N1923 organic top phase and PEG-rich middle phase, respectively, while Al(III)and other co-existing impurity ions, such as Si(IV), Fe(III), Ti(IV), Mg(II) and Ca(II) in acidic leach solutions,could be enriched in the(NH_4)_2SO_4 bottom aqueous phase. During the process for extraction and separation of V(V) and Cr(VI), almost all of impurity ions could be removed. The separation factors between V(V) and Cr(VI) could reach 630 and 908, respectively in the organic top phase and PEG middle phase, and yields of recovered V(V) and Cr(VI) in the top phase and middle phase respectively were all above 90%.Various effects including aqueous p H, A-N1923 concentration, PEG added amount and(NH_4)_2SO_4 concentration on three-phase partitioning of V(V) and Cr(VI) were discussed. It was found that the partition of Cr(VI) into the PEG-rich middle phase was driven by hydrophobic interaction, while extraction of V(V) by A-N1923 resulted of anion exchange between NO_3~- and H_2V_(10)O_(28)~(-4). Stripping of V(V) and Cr(VI) from the top organic phase and the middle PEG-rich phase were achieved by mixing respectively with NaNO_3 aqueous solutions and Na OH-((NH_4)_2SO_4 solutions. The present work highlights a new approach for the extraction and purification of V and Cr from the complex multi-metal co-existing acidic leach solutions of high-chromium vanadium–titanium magnetite.     

Study of Li2O addition on crystallization behavior and thermal expansion properties of CaO-Al2O3–SiO2 (CAS) glass-ceramic and its application for joining SiC ceramic

Various glass-ceramics were prepared based on the CaO-Al₂O₃-SiO₂ system with the addition of Li₂O in an attempt to develop a suitable sealant for SiC ceramic. The effects of Li₂O content on crystallization behavior and thermal expansion properties were systematically investigated. The results revealed that the addition of Li₂O significantly reduced the crystallization activation energy of glass. Besides, as the Li₂O content increased, the precipitation of spodumene and wollastonite was promoted while the precipitation of anorthite was suppressed. By controlling the Li₂O content and crystallization treatment, the coefficient of thermal expansion (CTE) of glass-ceramic could be adjusted in a certain range, from 8.5 × 10^?6/°C to 2.8 × 10^?6/°C. When the content of Li₂O was 3 wt.%, the CTE of the formed glass-ceramic was well-matched with that of SiC ceramic. Furthermore, it was confirmed that this glass-ceramic possessed an excellent wettability and weldability to SiC ceramic.     

Surface modification of magnesium hydroxide and its application in flame-retardant oil-extended styrene–ethylene–butadiene–styrene/polypropylene composites

Magnesium hydroxide (MH) was modified with triethoxysilane and polymethyl–vinyl silicone rubber and used to prepare flame-retardant oil-extended styrene–ethylene–butadiene–styrene (O-SEBS)–polypropylene (PP) composites. The water contact angle of modified magnesium hydroxide (MMH) reached 141°; this indicated that MMH possessed excellent hydrophobic properties. The samples (1.6 mm) passed the UL-94 V-0 rating during vertical burning tests when the loading amount of MH or MMH was 70 wt %. This indicated the modification did not decrease the flame-retardant properties of MH. The tensile strength and elongation at break values of the MMH–O-SEBS–PP composites increased by 20.4 and 88.9%, respectively, compared with those of the MH–O-SEBS–PP composites. The modification of MH enhanced the interfacial compatibility between the flame retardant and the matrix; thus, the mechanical performance was enhanced. Moreover, MMH was scarcely extracted after water treatment for 168 h at 70 °C. As a result, the mechanical properties and flame retardancy of the MMH–O-SEBS–PP composites were well maintained after the water treatment. The modification of the MH endowed the O-SEBS–PP composites with an excellent compatibility and water-resistant performance. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47129.     

Preparation of waterborne polyurethane/β-cyclodextrin composite nanosponge by ion condensation method and its application in removing of dyes from wastewater

Currently, polymer nanosponges have received extensive attention. However, developing new synthetic techniques for novel nanosponges remains a challenge. Furthermore, to date, composite nanosponge adsorbents based on waterborne polyurethane(WPU) and β-cyclodextrin(β-CD) have not been reported.Herein, a novel green method, ion condensation method, was developed in this study for the preparation of polymer nanosponge adsorbents for efficient removal of dyes from wastewater. Based on the principle ...     

Crystallization behavior of BaO–CaO–SiO2–B2O3 glass sealant and adjusting its thermal properties for oxygen transport membrane joining application

In this work, the thermal stability of a BaO–CaO–SiO₂–B₂O₃ glass sealant, named “H”, was investigated by differential scanning calorimetry (DSC). The crystallization behavior of glass H as the sealant matrix was investigated by a combination of experimental X-ray diffraction (XRD) analysis and thermodynamic simulation with the FactSage package. A good agreement was found between the Rietveld refinement of XRD experiments and the FactSage simulation. Particular attention was also given to the influence of the Sr₂SiO₄ filler added to the glass matrix “H” on the thermal expansion and microstructures of glass-Sr₂SiO₄ composites by means of dilatometry and scanning electron microscopy (SEM). The reinforced 20 wt% Sr₂SiO₄ composite (HS2S20) showed excellent properties and, thus, its joining performance was investigated using SrTi_0.75Fe_0.25O_3-δ (STF25) and Aluchrom as promising oxygen transport membrane (OTM) and counterpart, respectively. The joining behaviors were investigated by comparing different joining temperatures. 920 °C is the best joining temperature for HS2S20 sealant.