Microporous Ceramic Membranes Research Articles

Sacrificial GO-BD interlayer for high performance ceramic ultrafiltration membrane

As a new two-dimensional material, graphene oxide (GO) has been widely used in the preparation of microporous ceramic membranes. In this work, we report a facile GO and borax decahydrated (GO-BD) coating intermediate sacrificial layer by co-sintering process to prepare defect-free, ultrathin ceramic membranes. GO and BD were successfully crosslinked, which effectively blocked the permeation of membrane particles. Based on the GO-BD (GB) layer, a crack-free film layer with boehmite sol as the main components is prepared. The experiment showed that 0.8Al2O3/0.2 C3H8O3 was the film solution ratio that suited best. Meanwhile, 1050 °C is the optimal sintering temperature. Additionally, the prepared porous ultrathin membrane exhibited excellent permeability. The water flux and rejection (for methyl blue) of the ultrafiltration membrane (UM) were 720 L·m−2·h−1·bar−1 and 91.6% respectively, with a layer thickness of only 720 nm at the sintering temperature of 1050 °C. The method proposed in this work can effectively reduce the mass transfer resistance and sintering cost, and has great potential in the water treatment field.

Effects of condensate film flowing on condensation heat and mass-transfer deterioration on some regions within water-recovery module consisted of micro-porous ceramic membranes

Heat-transfer deterioration is a thermal phenomenon existing one or multiple wall temperature fluctuation along the flowing direction on porous heat-transfer surface. Effects of condensate film on deterioration phenomenon for non-condensation heat-transfer process has been reported in the literature, but for condensation process is seldom proposed and specifically researched. Here, the condensation heat and mass-transfer characteristics on micro-porous ceramic membrane module is investigated experimentally and numerically, with absolute humidity of artificial flue gas, inlet temperature of cooling water, volume flux of cooling water covered the ranges of 0.6375–0.6845 kg/m3, 294.4–297.2 K, 0.32–0.41 m3/s, respectively. Sudden temperature fluctuation and collapsing water-recovery efficiency are observed nearby 1/3 region of the ceramic membrane module, which corresponds to the fact that remaining condensate film induces large thermal resistance because of the low thermal conductivity of the gas-like phase, and causes fluctuation of temperature gradient (i.e. condensation heat-transfer deterioration) on membrane surface. It is found that, condensation-regime transition range decreases to 0.763–0.781 at 1/3 region of membrane module, which results in a more remarkable permeation hysteresis effect and a more dominant capillary condensation process. The present findings of this paper are helpful to optimize the design parameters and operation conditions of micro-porous ceramic membrane modules.

Numerical study of condensation film formation and transforming processes on porous surface within ceramic membrane

Porous wall surface on micro-sized ceramic membrane involves many applications such as film-wise condensation and permeation, but condensate dynamics on such surface is not well understood. Here, condensate forming and transforming on membrane wall surface was described by corresponding conservation equations. The volume of fluid (VOF) method tracked the gas-liquid interface. A set of parameters such as inlet velocity, convective heat-transfer coefficient etc. were combined to form three key non-dimensional parameters of We, F (spreading factor) and P (permeating factor). Numerical simulations agreed with experimental results on a same size micro-porous ceramic membrane in references. Here, we investigated three modes of condensate pattern within membrane, i.e. half-annular, stratified and annular pattern. The transformation among these three condensate patterns results in several condensate flowing state, e.g. separating state caused by transformation form half-annular pattern to stratified pattern. By adjusting the predominant driving force on condensate film, makes it possible to varying transforming principle on condensate pattern, such as condensate transformation from half-annular pattern to stratified pattern when We = 0.1, F/F0 varies from 0.5 to 2.5. The present findings of this paper are helpful to design controllable condensation membrane and ensure condensate film with a ideal thickness during the flowing process.

Research on the theoretical basis for engineering application of transport membrane condenser

Membrane separation technology is an important technology for efficient recovery of resources in the industrial production processes. Transport membrane condenser is a new type of membrane contactor which can recover moisture and waste heat from flue gas. In order to promote the large-scale industrial application of transport membrane condenser, several engineering experiments are designed in this paper. Based on the quantitative results, the effects of particulate matter in flue gas, cooling water physical parameters, porous ceramic membrane reliability and energy grade are analyzed. For engineering application, a series of suggestions are put forward. It includes setting microporous ceramic membranes before transport membrane condenser to capture particulate matter, designing the double circulating cooling water system, adopting the multi-stage transport membrane condenser arrangement, and using the recovered hot water to heat the feed water of No. 8 heater or shaft gland heater in the coal-fired power plant. These results effectively build a bridge between theoretical research and engineering application, and realize the guidance of theory to engineering.

Electrostatic adsorption and removal mechanism of ochratoxin A in wine via a positively charged nano-MgO microporous ceramic membrane

Ochratoxin A (OTA) is a very important mycotoxin. However, there are few studies on the removal of OTA in wine because of the great influence on product quality and difficulty in practical application. A nano-MgO-modified diatomite ceramic membrane (MCM) with a high positive charge was prepared and applied to remove OTA in wine. The isotherm adsorption between the positively charged membrane and OTA was in accordance with the Langmuir model, with a maximum adsorption capacity of 806 ng/g at 25 °C. All of the changes in adsorption enthalpy (ΔH), adsorption free energy (ΔG) and adsorption entropy (ΔS) were negative, which indicated that the combination of nano-MgO MCM and OTA was a spontaneous exothermic and nonspecific physical adsorption process. The concentrations of OTA in adsorption-treated wines were lower than 2 μg/kg, and the removal rates exceeded 92%. After OTA removal, the composition of wines was preserved to some extent.

Gas permeation and thermomechanical properties for macroporous alumina focused on necking size at grain boundaries

AbstractThe gas permeation and thermomechanical properties of macroporous alumina used as a support substrate for microporous ceramic permselective membranes were investigated. The porosity, pore size, and apparent necking size between grains of macroporous alumina were systematically varied, and the relationships between the porous microstructure and material properties were examined. The grain necking size at alumina grain boundaries was evaluated by microstructural observations. The nitrogen gas permeance of the porous alumina increased with increasing pore size. All the measured thermal and mechanical properties decreased with increasing porosity. The properties of porous alumina samples with extensive grain necking showed higher values even in samples with the largest pore size. The high thermal conductivity of porous alumina with extensive grain necking was due to the low interfacial thermal resistance at grain boundaries. Porous alumina with extensive grain necking had high thermal shock strength due to the higher thermal conductivity. It was demonstrated that a porous structure combining high gas permeability and excellent fracture resistance could be successfully achieved.

Textile Industry Wastewater Treatment by Cavitation Combined with Fenton and Ceramic Nanofiltration Membrane

This work first time reports the intensification of real wastewater treatment by combination of hydrodynamic cavitation (HC), Fenton reagent, and membrane separation. In this work, a micro-porous ceramic membrane was used for the preparation of nano-porous catalytic membrane reactor. Initially, the aluminium boehmite sol has been synthesized and coated onto the tube side of the ceramic membrane by wet impregnation technique. A layer by layer technique was adopted for the wet impregnation of boehmite sol onto the ceramic membrane. After achieving a desired number of layers coating onto the ceramic membrane, a prepared catalyst sol was further used for coating. The dried boehmite powder was characterized using X-ray diffractometer and particle size distribution analysis. Mercury intrusion porosimetry (MIP) technique was used to identify the pore size distribution of modified ceramic membrane. The modified ceramic membrane was used in conjunction with HC for industrial dye wastewater treatment. The impact of process parameter such as cavitation unit (orifice) inlet pressure, intensifying chemical additive like Fenton reagent, and H2O2 dosage was investigated. HC along with intensifying chemical additives H2O2 and Fenton reagent improved the organic pollutants removal from textile industry wastewater

Plasma Enhancement Gases separation via ceramic porous membranes for plasma exhaust processing system of DEMO

Plasma Enhancement Gases (PEGs), i.e. N2 and noble gases, are used to mitigate the heat load over plasma facing components. Therefore, in DEMO, the tokamak exhaust stream will contain a certain amount of these PEGs which require a dedicated purification and separation unit. In the last years, PEG separation using microporous ceramic membranes has been studied at ENEA Frascati laboratories in the framework of the EUROfusion programme. The experiments conducted with a binary gas mixture have revealed the poor separation capability of the multi-channel membranes as a consequence of their high permeance.In this activity, the behaviour of a commercial microporous single-channel membrane made of alpha alumina has been theoretically studied to evaluate its efficacy in separating H2 from PEGs. The analysis has considered a total feed flow rate of 20 L min−1 (at STP) having an equimolar composition of H2 with one of the following species: PEG (Ar or N2), D2 or He. The separation capability has been evaluated by assuming the upstream pressure in the range 200−1000 kPa and keeping the downstream pressure at 100 kPa. Considering the values of the permeances assessed in our previous work for single gas tests, the membrane length needed to achieve a given target of separation has been evaluated as a function of the H2 mole fraction in the retentate stream.

Development of H2 selective silica membranes: Performance evaluation through single gas permeation and gas separation tests

To prove the usefulness and achieve penetration of microporous ceramic membranes in gas separation applications of industrial interest, their behavior needs to be validated and predicted at relatively realistic conditions. In this respect, the present study employed hybrid silica (HybSi) membranes, modified by chemical vapor infiltration (CVI) in order to render them more selective to hydrogen in hydrogen/carbon dioxide binary mixtures, which are representative to effluent streams of methane or biogas steam reforming/water gas shift processes. Experimental studies with a single modified membrane exhibited high hydrogen permeance (1.5.10−7 mol.m−2.s−1.Pa−1, at 250 °C) and H2/CO2 permselectivity (H2/CO2 = 61.3, at 250 °C). Gas separation tests with binary gas mixtures revealed that high hydrogen purity values (>99%) can be reached at different process conditions. The mathematical model, also developed in this study in order to interpret the experimental results, can reliably predict hydrogen separation process performance over a wide range of operating conditions and also serve as a tool for subsequent optimum process engineering purposes.

Experimental study on synergistic capture of fine particles and waste heat from flue gas using membrane condenser

This work proposes a new method for capturing fine particles based on heterogeneous condensation technology. The microporous ceramic membranes are used to manufacture membrane condenser, which is used to capture fine particles from the exhaust emitted by a natural gas-fired boiler. The effects of different operating conditions on fine particle capture efficiency, condensate water quality, condensation and thermal performance are investigated experimentally. In addition, the technical economy of membrane condenser applied in a 330 MW coal-fired generating unit is analyzed. The results show that membrane condenser can effectively capture fine particles from flue gas, and capture efficiency is positively related to the heterogeneous condensation intensity. Furthermore, membrane condenser has a good application prospect in thermal power plants. Based on the proposed evaluation method and application on the natural gas-fired boiler, this work studies the heterogeneous condensation performance from multiple dimensions, expands the application scenarios of device, and explores the feasibility of synergistic capture of fine particles, water vapor and waste heat.

In situ growth of two-dimensional ZIF-L nanoflakes on ceramic membrane for efficient removal of iodine

Radioactive pollutants are in places a serious environmental pollution problem. By virtue of their structural diversity and tunability, two-dimensional (2D) zeolitic imidazolate frameworks-L (ZIF-L) have shown a promising ability for pollutant removal by adsorption. For the first time, we propose a 2D ZIF-L assembled on and in a microporous ceramic membrane for efficient removal of iodine via seed-assisted in situ growth. It is challenging to customize inner pore channels of ceramic membrane due to its irregular structure. This work provides new insights into the crystallographic growth of ZIF-L on the inner irregular pore channels and a homogenous ZIF-L layer on porous silicon carbide (SiC) membranes. The resulting hybrid membrane contains highly loaded ZIF-L nanoflakes on the surface and pore channels of the SiC membrane. These multilayers structure and ZIF-L@SiC synergistic features provide more active sites and improve the mass transfer of molecular iodine dissolved in cyclohexane, thereby enhancing removal efficiency. The removal efficiency of iodine using the hierarchically nanostructured ZIF-L@SiC hybrid membrane is near 100% and 96% at a flux of 9.37 × 103 L m−2 h−1 with iodine/cyclohexane concentrations of 5 mg L−1 and 50 mg L−1, respectively. This porous adsorption membrane, with excellent separation and adsorption capacities for iodine, opens a new way for radionuclide adsorption.

Water vapor capture using microporous ceramic membrane

Porous ceramic membrane can effectively capture water vapor from flue gas. In this paper, the transport membrane condenser (TMC) is manufactured using microporous ceramic membranes with a pore size of 0.4 nm, and its feasibility to capture water vapor is verified on a gas-fired boiler experimental platform. The water vapor capture mechanism of microporous ceramic membrane is analyzed by designing different experiments under different operating conditions and different operating modes. According to the results, film condensation is the main capture mechanism; under the action of Knudsen diffusion mechanism, the microporous ceramic membrane can capture water vapor, but the capture flux is very small; no capillary condensation occurs in the pores of microporous ceramic membrane. Based on laboratory-scale research, a pilot-scale experimental platform is set up to test water vapor capture performance in the coal-fired power plants. The pilot-scale testing result further demonstrates the feasibility of capturing water vapor with microporous ceramic membrane, which greatly expands the selection range of materials used to manufacture TMC.

Laser induced graphene /ceramic membrane composite: Preparation and characterization

In this work, laser induced graphene (LIG) was successfully fabricated on microporous ceramic membranes. The surface area, morphology, and chemical characterizations were performed on the LIG layer. Water contact angle measurements showed the hydrophobicity of LIG. Pure water and solvents with different polarities were used to understand the solvent flux behavior of LIG membrane. The LIG membrane showed very high non-polar solvent fluxes and remarkably low water permeability, and thus, the transport through the LIG membrane is related to dipole moment and dielectric constant, represented by solvent polarity. The LIG membrane achieved 90% rejection for 255 nm diameter silica particles, suggesting the presence of submicron size connecting pore channels that dominate the transport mechanism.

Study on Permeability Stability of Sand-Based Microporous Ceramic Filter Membrane.

The instability of diafiltration is a widespread problem in the practical application of microporous ceramic filtration membranes. In this paper, a series of microporous ceramic filter membranes were prepared using inexpensive standard sand and river sand as matrix materials. Semi-empirical formula for the effective permeability radius of ceramic membranes with respect to time was established from analysis of the response mechanism between water flow and material properties. Finally, on the basis of theoretical analysis, some measures were proposed to improve permeate flux. The experimental results showed that during the initial stage of filtration, the microporous ceramic filter membrane had a large change in permeate flux, and during the late stage of filtration, permeate flux tended to be stable. Over time, open porosity and closed porosity changed the actual seepage area of the ceramic membrane, and this affected the stability of permeate flux and final stable permeate flux. The roughness of the inner wall of microporous ceramic pores affected the hydraulic loss coefficient, and this controlled the outflow process. Trace elements that were rich in sand produced a large amount of glass phase after sintering. The glass phase was rich in polar groups and formed a temporary hydrogen bond with the small flow of water molecules. It led to an increase in viscous resistance effect of the side wall along the water flow and the extent of the permeate flux of the ceramic membrane changed with time.

Experimental study of condensation heat-transfer and water-recovery process in a micro-porous ceramic membrane tube bundle

Micro-porous ceramic membrane tube is a new type of condensation material which can synchronously recover both water vapor and its accompanied latent heat from exhausted flue gas. The recovery outcome is helpful to reduce amount of make-up water and enhance boiler efficiency of thermal power plant. In this study, an experiment has been carried out to investigate condensation heat-transfer, water-recovery, and flow-resistance performance of micro-porous ceramic membrane tube bundle (CMTB), respectively. In addition, real exhausted flue gas with inlet flow rate ranging from 390 to 750 m3/h, temperature ranging from 323 K to 373 K was used as experimental feed gas. Results showed that the condensation heat-transfer process got more apparently with increasing of flue gas inlet temperature (from 335.3 K to 364.8 K). In addition, both cooling water flow rate and heat-transfer temperature difference had a remarkable influence on the water-recovery performance of the CMTB, and maximal water-recovery mass flow rate could reach 0.0336 × 103 kg/h. Most of all, velocity drop of flue gas was controlled within an appropriate range (from 28.94 m3/h to 178.78 m3/h). The application analysis on the CMTB gives a good perspective for designing high efficiency membrane-type condenser to recover water vapor from exhausted flue gas and make good use of its latent heat in the thermodynamic system of power plant.

Heat and water recovery from flue gas: Application of micro-porous ceramic membrane tube bundles in gas-fired power plant

Heat and water trans-membrane condenser (HWTMC) consisted of ceramic membrane tube bundles and cooling pathway is a functional apparatus to recover heat and water from flue gas in thermal power plants. In this study, the water and heat-recovery performance of 2 μm HWTMC on a gas-fired power plant was studied theoretically and experimentally. The simultaneous drop-wise/film-wise condensation heat transfer process was proposed in this study, and we investigated them by installing several temperature sensors within the HWTMC. In addition, the heat and water-recovery performance of HWTMC was evaluated respectively under different operational conditions, and the velocity loss of flue gas was also measured to verify its practicability. The experimental results showed that flue gas temperatures change significantly in the first 2/3 of the HWTMC unit, while barely change at end, especially when they are higher than 103.5°C. Compared with other operational conditions, moreover, a moderate cooling water inlet flow rate (0.3 m3/h) would result in a remarkable heat and water-recovery performance. To guarantee the efficiency of the experimental HWTMC with total membrane area of 0.145 m2, flue gas flow rate should be set under 500 m3/h. This paper is useful for membrane type waste heat and water-recovery installation design.

Graphene Coated Microfiltration Ceramic Membrane Fabricated by Photothermic Conversion of Polyimide

ABSTRACTIn this study, a novel technique has been developed for the fabrication of uniform, stable, and strongly bonded graphene layers on microporous ceramic membranes. A composite ceramic-LIG membrane was obtained following one step scalable methodology. First, the ceramic support was spin-coated with poly (pyromellitic dianhydrideco-4,4´-oxidianiline, amic acid) (PMDA-ODA) and transformed to polyimide (PI) by thermal imidization. The PI was then irradiated with a CO2 laser to photothermally convert the sp3-carbon atoms to sp2-carbon atoms. Different PMDA-ODA layers were applied to achieve uniform coating by LIG on the membrane surface. The LIG was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and contact angle (CA) measurements. FTIR results showed a complete conversion of PMDA-ODA to PI following the thermal imidization reaction. The XRD results revealed the crystalline structure of graphene layer, which had a surface area of 130 ± 5.6 m2/g, determined by BET nitrogen adsorption. However, the permeability of uncoated ceramic membranes decreased with increasing number of PMDA-ODA layers, as evidenced by the clean water filtration experiments. The new composite membrane is a promising new material for membrane distillation or electro osmosis, where the hydrophobicity of the graphene layer may provide important advantages over current membrane materials.

Effect of mass transfer on heat transfer of microporous ceramic membranes for water recovery

In this work, a theoretical study was carried out to investigate the heat and mass transfer of recycling water vapor from flue gas with using the microporous ceramic membrane. The mathematical model was also built to study the effect of mass transfer on heat transfer in the microporous ceramic membrane with the gas on one side and the liquid on the other side. Results showed that the heat transfer due to mass transfer increased with the increasing mass transfer flux, and gradually became the predominant part of the total heat transfer on the feed side. Inside the membrane, the heat conduction is the main heat transfer. In addition, the heat transfer due to mass transfer could be neglected on the permeate side. The modified heat and mass transfer model for calculating the wall temperatures of the membrane showed good agreement with the experimental results.

Stability of oil-in-water emulsions produced by membrane emulsification with microporous ceramic membranes

Membrane emulsification has been drawing attention due to its many application possibilities. This study aimed to assess the preparation and stability of oil in water (O/W) emulsions by membrane emulsification technique. Microporous ceramic membranes with mean pore size 0.2 μm and 0.8 μm were used for producing sunflower oil in water emulsions, displaying mean droplet size ranging from 2.9 to 11.6 μm and from 4.8 to 16.2 μm, respectively. The effect of the oil concentration (10%–20%), surfactant concentration (1%–4%), tangential velocity (0.12 m s−1 to 0.24 m s−1), and feed pressure (100 kPa–300 kPa) on the process performance was investigated using an experimental design. All the parameters significantly influenced the mean droplet size, the droplet size distribution, and the emulsion stability. Depending on the emulsification conditions, monodisperse and polydisperse emulsions were obtained. The use of a membrane with 0.2 μm mean pore size led to better results than those obtained with a 0.8 μm membrane, since they yielded emulsions displaying smaller droplet size and narrower size distribution. The emulsions prepared using this membrane were stable up to 100 days.

Positively charged microporous ceramic membrane for the removal of Titan Yellow through electrostatic adsorption

To develop a depth filter based on the electrostatic adsorption principle, positively charged microporous ceramic membrane was prepared from a diatomaceous earth ceramic membrane. The internal surface of the highly porous ceramic membrane was coated with uniformly distributed electropositive nano-Y2O3 coating. The dye removal performance was evaluated through pressurized filtration tests using Titan Yellow aqueous solution. It showed that positively charged microporous ceramic membrane exhibited a flow rate of 421L/(m2·hr) under the trans-membrane pressure of 0.03bar. Moreover it could effectively remove Titan Yellow with feed concentration of 10mg/L between pH3 to 8. The removal rate increased with the enhancement of the surface charge properties with a maximum rejection of 99.6%. This study provides a new and feasible method of removing organic dyes in wastewater. It is convinced that there will be a broad market for the application of charged ceramic membrane in the field of dye removal or recovery from industry wastewater.