Tubular Ceramic Substrate Research Articles

Polyamide nanofiltration membrane with MoS2 interlayer on tubular ceramic substrate for desalination

The tubular ceramic substrate has great potential in membrane separation because of its excellent solvent and temperature resistance, pressure stability, and long service life. However, it is still a challenge to prepare an ultrathin intact selective layer by interfacial polymerization (IP) on a porous tubular ceramic substrate, due to its large pore size and defects on the surface. In this study, a molybdenum sulfide (MoS2) interlayer with a loose structure was formed on the tubular ceramic substrate via hydrothermal, which provided a large surface area and fast transport channels. Subsequently, a polyamide (PA) skin layer was formed on the MoS2 interlayer through the IP procedure to obtain a composite membrane for desalination. The prepared PA/MoS2/ceramic composite membrane showed excellent water permeance of 17.7 L·m−2·h−1·bar−1 with a 96.8 % rejection of Na2SO4. Moreover, the prepared membranes showed good pressure resistance and long-term stability under cross-flow filtration within 30 days.

Fabrication of robust ceramic supported polymeric composite nanofiltration membrane for heavy metal contaminated wastewater treatment

Nanofiltration (NF) membranes with positive charge are essential for efficient removal of heavy metals and salts from waste water. In this work surface modified positively charged novel ‘ceramic-supported-polymeric’ (CSP) composite NF membranes were fabricated with the copper ions embedded crosslinked polyethyleneimine polymer matrix over tubular ceramic substrate using facile dipcoating method. EDX, ATR-FTIR, XPS, FESEM, AFM and contact angle analyses were performed to characterize the chemical structures and morphologies of the prepared membranes. The composite NF membrane exhibited satisfactory pure water permeability (PWP) of 8.1 L.m−2.h−1.bar−1 and promising salt (87.19 % and 74.41 % for Mg2+ and Ca2+, respectively) and heavy metal ion rejections (91.73 %, 83.15 % and 75.50 % for Zn2+, Ni2+ and Cd2+, respectively). Activation energy and overall size-exclusion-dehydration phenomena along with steric hindrance and Donnan electrostatic exclusion plays an important role for heavy metals and salts rejection. In addition, the membrane showed excellent antifouling properties (>99 % humic acid removal) with high flux recovery ratio (77.6 %) and low flux decline ratio (33 %) for 5 h operations (3rd cycle) together with outstanding antibiofouling ability towards Brevibacillusagri and Leclerciaadecarboxylata. Furthermore, excellent chemical stability of the membrane suggests its potential application for waste water treatment under critical conditions.

Alcohols assisted in-situ growth of MoS2 membrane on tubular ceramic substrate for nanofiltration

Molybdenum disulfide-based membranes have received wide attention for their excellent performance in chemical separation field. Yet, manipulating the structure of MoS2 membranes still remains an unprecedented challenge. In this work, the tubular MoS2 ceramic membranes were prepared by in-situ hydrothermal method using aqueous solution of thiourea and ammonium molybdate as precursor solution. The structure and morphology of the membranes were manipulated by introducing different alcohols into the precursor solution. The results indicated that the presence of alcohols drove the transformation of MoS2 morphology from nanosheets to spherical aggregates. As the molecular weight of the alcohols decreased, more small-sized molybdenum disulfide spheres were formed on the tubular ceramic substrate, which resulted in the formation of a great number of large transportation channels and promotion of surface area, and thereby improved the permeability of the membrane. Moreover, the addition of different alcohols enhanced the negative charge of the membrane surface, which ensured an effective rejection while enhancing the membrane permeability. The results demonstrate that the membranes prepared in a water-ethanol mixed solvent possess an excellent permeability for water (33.2 L/(m2 h bar)) and methanol (52.2 L/(m2 h bar)), with a rejection of more than 97% for Eriochrome black T, and an excellent pressure resistance as well as long-term running stability under cross-flow filtration. In addition, such membrane exhibited a below 30% rejection for salts, which can be utilized for dye desalination.

Fabrication of MOF derivatives composite membrane via in-situ sulfurization for dye/salt separation

In this study, metal-organic framework (MOF) layer on the surface of tubular ceramic substrate was prepared as the precursor template to construct ZIF-67-derived CoS x composite membrane through in-situ sulfurization strategy. During the sulfurization process, ZIF-67 as a template was reacted with sulfur ions to form CoS x . Due to the structure change of the ZIF-67 crystal, the aperture of the CoS x was enlarged with the thickness of the separation layer decreased. Moreover, the reorganization of the separation layer caused by the in-situ sulfurization eliminated the non-selective defects. Therefore, a CoS x composite membrane can be obtained with high separation performance and good stability for dye/salt separation. The effects of sulfurization and operation conditions on membrane performance were studied. The CoS x composite membrane had outstanding permeance (751.6 LMH/MPa) and excellent rejection (>99.5%) for dye molecules, while the rejection for salt was below 18.7%. The separation performance of the CoS x composite membrane can be maintained over 100 h, which exhibited great potential in dye desalination. • A ZIF-67-derived CoS x membrane was constructed by in-situ sulfurization strategy. • The aperture of crystal was enlarged, and grain boundary cracks were eliminated. • The thickness of separation layer was decreased after sulfurization. • The CoS x composite membrane had high dye rejection and low salt rejection. • The permeance of the CoS x membrane was enhanced by 2.8 times.

In-situ growth of graphene quantum dots modified MoS2 membrane on tubular ceramic substrate with high permeability for both water and organic solvent

Molybdenum disulfide (MoS2) is widely used in membrane separation because of its outstanding chemical and structural stability. In this study, MoS2 nanosheets were in-situ grown on a tubular ceramic substrate through one-step hydrothermal synthesis with the graphene quantum dots (GQDs) incorporated in the precursor solution. The growth of the MoS2 nanosheets was inhibited due to the combination with GQDs through the Mo-O bond. Therefore, the number of transport channels in the MoS2/GQDs composite membrane were increased to improve the permeability. The results indicated that the MoS2/GQDs composite membrane have excellent permeances for both the aqueous solution and organic solvent. Moreover, the MoS2/GQDs composite membrane can be continuously operated in cross-flow filtration device for 100 h because the in-situ hydrothermal method has greatly improved the stability of membrane. The results indicated that the MoS2/GQDs composite membrane exhibits great potential in nanofiltration.

Ultrathin Reduced Graphene Oxide/Organosilica Hybrid Membrane for Gas Separation.

Here, reduced graphene oxide (r-GO) nanosheets were embedded in an organosilica network to assemble an ultrathin hybrid membrane on the tubular ceramic substrate. With the organosilica nanocompartments inside the r-GO stacks and the intensified polymerization, r-GO sheets endow the as-prepared hybrid membranes with high H2 and CO2 separation performance. The resulting selectivities of H2/CH4 and CO2/CH4 are found to be 223 and 55, respectively, together with gas permeance of approximately 2.5 × 10–7 mol·m–2·s–1·Pa–1 for H2 and 6.1 × 10–8 mol·m–2·s–1·Pa–1 for CO2 at room temperature and 0.2 MPa. To separate larger molecules from H2, the H2/C3H8 and H2/i-C4H10 selectivities are as high as 1775 and 2548, respectively. Moreover, at 150 °C and 0.2 MPa, the hybrid membrane retains high separation performances with ideal selectivities higher than 200 and 30 for H2/CH4 and CO2/CH4, respectively, which are attractive for gas separation and purification of practical applications.

Removal of As(V), Cr(VI) and Cu(II) using novel amine functionalized composite nanofiltration membranes fabricated on ceramic tubular substrate

Novel amine functionalized composite membranes were prepared over tubular ceramic substrate using facile dip-coating and cross-flow filtration approach. The two fabricated membranes, P-60S and P-60S-EDTA with polyethyleneimine (PEI) and EDTA-modified PEI as functional layers respectively, were characterized in terms of EDX, FTIR, XPS, FESEM, AFM and contact angle analyses which confirmed their stable physical and chemical structure for use in high pressure application. Clean water permeability and MWCO study revealed the superior permeability and rejection efficiency of the P-60S-EDTA compared to the P-60S membrane. Incorporation of bulky EDTA molecules in the membrane functional layer simultaneously decreased pore size and increased membrane hydrophilicity. The removal of As(V), Cr(VI) and Cu(II) heavy metals by both membranes were found to be highly pH dependent and overall rejection improved in case of P-60S-EDTA membrane [99.82% for Cu(II), 96.75% for As(V) and 97.22% for Cr(VI)]. Interestingly, rejection of As(V) and Cr(VI) was significantly improved in presence of Cu(II) due to volume resistance provided by EDTA-Cu(II) complex towards the passage of other heavy metal ions. Excellent stability of P-60S-EDTA membrane in continuous operation of 36 h in both ideal and practical water environment suggests its promising application in real field heavy metal contaminated waste water treatment.

Orderly stacked ultrathin graphene oxide membranes on a macroporous tubular ceramic substrate

The orderly stacked laminate structures and extraordinary physicochemical properties of graphene oxide (GO) enable this material to serve as a nano-building block for separation membranes. However, attaining GO that has orderliness and regularity on three-dimensional substrates is still a great challenge. A new multiple tailored assembly is proposed to fabricate ethylenediamine-cross-linked GO composite membranes on a macroporous tubular ceramic substrate. X-ray diffraction, gas transmission rate and contact angle residence time analyses indicate that the GO nanosheets obtained from this method are neatly arranged, thus demonstrating the construction of efficient nanochannels for mass transfer. The resulting mul-EGO-60 membranes feature a permeability of 375.75 Lm−2h−1MPa−1, which is 5.62 times as high as the pristine GO membranes without compromising the rejection (98.60%) of eriochrome black T. The flux and rejection for Na2SO4 are 237.72 Lm−2h−1MPa−1 and 78.32%, respectively. The multiple tailored assembly offers an effective method for preparing high-performance two-dimensional GO membranes for mass separation.

Design of thin and tubular MOFs-polymer mixed matrix membranes for highly selective separation of H2 and CO2

Metal organic frameworks (MOFs) based mixed matrix membranes (MMMs) have shown a great potential for gas separation applications, but rarely reported the fabrication of the tubular MMMs that are favorable for practical applications. Here, for the first time, we report facile fabrication of thin MOFs (NH2-CAU-1 and NH2-MIL-53) based MMMs on tubular ceramic substrate modified by organosilica as bonding layer. The as-synthesized ultrathin and continuous MMMs are tightly bound with the substrate and MOF nanoparticles are well-dispersed into polymer matrix. The resulting membranes display excellent gas separation performance with both elevated selectivity and enhanced permeation rate, which can be affected by the incorporated MOFs. The corresponding MMM containing 20 wt% NH2-MIL-53 and 80 wt% PMMA has a high H2 permeance of 1.094 × 10−8 mol·s−1·Pa−1·m−2 and high selectivity of up to 53.1 for H2 and CO2.

Vacuum-assisted assembly of ZIF-8@GO composite membranes on ceramic tube with enhanced organic solvent nanofiltration performance

Organic solvent nanofiltration (OSN) is an emerging technology for molecular separation and purification in organic media. The separation performances are mainly depended on the material and structure of the membrane. In this study, Zeolitic Imidazolate Framework (ZIF-8) nanoparticles were in situ growth onto the surface of graphene oxide (GO) sheets to form ZIF-8@GO composites, which were co-deposited with polyethyleneimine (PEI) matrix on tubular ceramic substrate through a vacuum-assisted assembly method. The dispersion of ZIF-8 nanoparticles in PEI matrix as well as the compactness and uniformity of the composite membranes were readily improved due to the templating effect of lamellar GO sheets and the transmembrane pressure. Membrane performance in OSN was evaluated on the basis of methanol permeance and retention of dye molecules. Methanol permeance increased when ZIF-8@GO laminates were embedded into the PEI layer, whereas the retention remained higher than 99%. The improvement of separation performance may be due to the well dispersion of ZIF-8 nanoparticles in PEI matrix, which offers more well-defined pathways for solvent molecules. Building on these findings, we demonstrate a simple scalable method to obtain robust ZIF-8@GO based membranes with enhanced OSN performance.

Tuning inter-layer spacing of graphene oxide laminates with solvent green to enhance its nanofiltration performance

In this study, the inter-layer spacing between graphene oxide (GO) layers were tuned with solvent green (SG) to enhance the nanofiltration performance of the laminar GO membranes. GO nanosheets were firstly modified by SG through the strong π-π stacking interactions. The SG@GO nanocomposites were then assembled onto the surface of tubular ceramic substrate through immersion method. The morphologies and structures of the resulting SG@GO composite membranes were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR). The composite membrane was used for removing dye molecules (Eriochrome black T) from water. It was found from the results that the SG@GO composite membranes showed a flux of 330Lm−2h−1MPa−1, which was nearly 6-fold enhancement compared with that of the pristine GO membrane (56Lm−2h−1MPa−1), without sacrificing the dye rejection. Therefore, this strategy may provide a facile approach to tune the inter-layer spacing of GO laminates for efficient molecular separation.

Removal of chromium from synthetic wastewater using MFI zeolite membrane supported on inexpensive tubular ceramic substrate

A mordenite framework inverted (MFI) type zeolite membrane was produced on inexpensive tubular ceramic substrate through hydrothermal synthesis and applied for the removal of chromium from synthetic wastewater. The fabricated ceramic substrate and membrane was characterized by diverse standard techniques such as X-ray diffraction, field emission scanning electron microscope, porosity, water permeability and pore size measurements. The porosity of the ceramic substrate (53%) was reduced by the deposition of MFI (51%) zeolite layer. The pore size and water permeability of the membrane was evaluated as 0.272 μm and 4.43 × 10–7 m3/m2s.kPa, respectively, which are lower than that of the substrate pore size (0.309 μm) and water permeability (5.93 × 10–7 m3/m2s.kPa) values. To identify the effectiveness of the prepared membrane, the applied pressure of the filtration process and initial chromium concentration and cross flow rate were varied to study their influence on the permeate flux and percentage of removal. The maximum removal of chromium achieved was 78% under an applied pressure of 345 kPa and an initial feed concentration of 1,000 ppm. Finally, the efficiency of the membrane for chromium removal was assessed with other membranes reported in the literature.

Co(HCOO)2-based hybrid membranes for the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures

In this work, Co(II)-formate (Co(HCOO)2) has been demonstrated feasible to be used as stable aromatic hydrocarbon transport carrier for facilitating aromatic hydrocarbon transport membranes. Metal-organic framework Co(HCOO)2 materials with different particle sizes were prepared through a solvothermal synthetic method, and then were doped into poly(ether-block-amide) (PEBA). The resulting hybrids were finally deposited on the outer surface of tubular ceramic substrate with a dynamic pressure-driven assembly method. The morphologies and structures of the resulting Co(HCOO)2/PEBA membranes were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDX), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), positron annihilation lifetime spectroscopy (PALS), and nanoindentation. These membranes were then used in separating aromatic/aliphatic hydrocarbon mixtures through pervaporation. When the feed solution is 10wt% toluene/n-heptane mixtures, the permeate flux of the membrane is 771g/(m2h) with a separation factor of 5.1. Meanwhile, due to the immobilization effect of the Co(HCOO)2 for Co(II) ions, the Co(HCOO)2/PEBA membrane showed stable separation performances.

Ceramic tubular MOF hybrid membrane fabricated through in situ layer‐by‐layer self‐assembly for nanofiltration

Nanofiltration has been playing an important role in water purification, in which the developments of novel membrane materials and modules are among significant. Herein, a metal‐organic framework (MOFs) hybrid membrane, ZIF‐8/PSS was fabricated on a tubular alumina substrate through a layer‐by‐layer self‐assembly technique. ZIF‐8 particles in situ grow into PSS layers to improve their compatibility and dispersion, thereby getting high quality membrane, which was loaded into a steel tubular module for nano‐filtrating dyes from water. Under optimized conditions, it shows outstanding nanofiltration properties toward methyl blue, with the flux of 210 Lm−2 h−1 MPa−1 and the rejection of 98.6%. Furthermore, the good pressure resistance ability and running stability of the membrane were revealed, which can be attributed to use the ceramic substrate and the inherent stability of ZIF‐8. This work thus illustrates a simple approach for fabricating MOFs hybrid membranes on tubular ceramic substrates, having great potential for industrial applications. © 2015 American Institute of Chemical Engineers AIChE J, 62: 538–546, 2016

Tubular ceramic-based multilayer separation membranes using spray layer-by-layer assembly

An automatically controlled spray-layer-by-layer (LbL) assembly method was used to build multilayers onto a tubular ceramic macroporous substrate. Poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAA) were alternately sprayed onto a rotating tubular ceramic substrate. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses of different locations on the substrate confirmed that a fine coating formed on both the top surface and in the pores of the macroporous ceramic substrate. The substrate pretreatment using water filling greatly influenced the self-assembly process, slowing the penetration of the polyelectrolyte into the substrate pores, resulting in different multilayer morphologies. The effects of the substrate pretreatment, number of bilayers, and the addition of salt into the polyelectrolyte solution on the dye rejection performance were investigated. We found that the substrate pretreatment and the addition of NaCl to the polyelectrolyte solution could change the multilayer structure, in turn affecting the separation performance of the composite membranes. The composite membrane consisting of 5 layers of PEI/PAA had a flux of ∼10.0 kg m−2 h−1 and a rejection of >99%. Moreover, spray-LbL assembly using different polymer pairs such as poly(diallyldimethylammonium chloride)/poly(styrenesulfonate) (PDDA/PSS) and PEI/TiBisLac/PAA on vertically held tubular Al2O3 substrates was also explored. Using these materials led to the formation of different types of polymeric multilayers and in situ nanohybrid multilayers. Our study demonstrates that a multilayer membrane can be successfully prepared on a 3D support by an automated spray system, and can easily be used to rapidly coat large areas.

Combined adsorption–permeation membrane process for the removal of chromium (III) ions from contaminated water

The objective of this work is the examination of the combined adsorption–permeation process for the removal of trivalent chromium from the aqueous phase. Two types of supported membranes are developed on the top surface of an asymmetric α-Al 2O 3 tubular ceramic substrate by the sol–gel method: the first one was made of γ-Al 2O 3 while the second one of γ-Al 2O 3 or TiO 2. The synthesized membranes are subsequently adapted to an ultrafiltration unit operating in a continuous cross flow mode, and are investigated for the removal of Cr(III) from the aqueous phase. The adsorption capacity of γ-Al 2O 3 and TiO 2 is examined in single batch experiments at different pH values and it is found that maximum chromium removal is observed for TiO 2, at pH = 5. It appears that the adsorption capacity for TiO 2 is not affected by the adsorbent dosage. The combined adsorption–permeation process is then studied in the membrane ultrafiltration unit for the treatment of a 0.5 mg L −1 solution; negligible chromium effluent concentration was measured, for both types of membranes, the one with the TiO 2 layer appearing to have a higher efficiency. The examination of membrane surface by SEM and TEM revealed the formation of a chromium layer, that was attributed to the membrane layer acidic sites. FT-IR studies showed that the membrane with the highest chromium removal capacity presented a high percentage of strong Brönsted acidic sites.

Real-time monitoring of metal deposition and segregation phenomena during preparation of PdCu membranes

The N 2 and H 2 evolution, respectively, were monitored during deposition of Pd and Cu from electroless plating baths to obtain in-process control of the composition during preparation of 3–7 μm thick PdCu membranes on tubular ceramic substrates. Compositions estimated by gas evolution compare favorably to those measured in post-mortem XRD and EDS analyses, mostly differing by not more than 1 at.%. This result suggests that use of gas evolution measurements to enable in-process control of composition to within 1 at.% is feasible. Annealing experiments in an H 2 atmosphere demonstrated that, at 893 K, only 48 h are needed to form a stoichiometrically homogeneous, 9.5 μm thick, face centered cubic (fcc) Pd 63Cu 37 membrane from sequentially deposited layers; at 723 K, the same transformation requires over 2 weeks. The appearance of transient body centered cubic (bcc) and fcc phases with lower Pd contents signaled compositional segregation in the initial stages of alloy formation at 723 and 773 K and could be a source of persistent stoichiometric heterogeneity particularly in bcc PdCu membranes. The H 2 fluxes of fcc Pd 58Cu 42 and Pd 70Cu 30 membranes were J H 2 = ( 1.6 ± 1.1 ) mol m − 2 s − 1 exp [ ( − 24.8 ± 0.4 ) kJ mo l − 1 / R T ] and J H 2 = ( 3.7 ± 0.6 ) mol m − 2 s − 1 exp [ ( − 21.3 ± 1.0 ) kJ mo l − 1 / R T ] , respectively, at 100 kPa H 2 pressure difference.

High flux palladium–copper composite membranes for hydrogen separations

Composite Pd alloy membranes have been investigated as a means of reducing the membrane cost and improving H 2 flux. Recently, we have been able to dramatically reduce the thickness of our Pd alloy membranes to approximately one micron. This is significant because at this thickness, it is the cost of the porous support that controls the materials cost of the composite Pd alloy membrane, not the palladium inventory. We have prepared a 1.3-micronthick Pd 95Cu 5 (composition given in mass %) alloy film, coated on a Pall Corporation Membralox® T1-70 tubular ceramic substrate, which nearly meets the DOE pure hydrogen flux target of 200 scfh/ft 2 at 400°C and 20 psi hydrogen partial pressure.

A method for the uniform chemical vapor deposition of tin-doped indium sesquioxide films on cylindrical substrates

One of the applications of electrically conductive tin-doped indium sesquioxide films is as the air electrode current collector material in a high temperature thin film fuel cell power device. For this application it is necessary to produce films of reproducible uniform thickness and composition on tubular ceramic substrates; this requirement prompted the development of the chemical vapor deposition (CVD) method described in this paper. The method was based on the high temperature hydrolysis of the chloride and oxychloride vapors of tin and indium. A single reactor was employed both for the generation of these vapors and for their hydrolysis reaction. The dimensions of this reactor allowed the formation of films of reproducible and uniform thickness and composition on tubular substrates 25 cm long and of external diameter 1.27 cm. The films, produced on calcia-stabilized zirconia and alumina substrates, were characterized by electrical resistance measure'ments, chemical analysis and microscopic examination. The room temperature resistivity of the as-prepared films was close to 2.0 × 10 −4 Ω cm for thicknesses ranging from 20 to 50 μ. Information on the temperature dependence of the resistivity of annealed films on the calcia-stabilized zirconia substrate is also presented.