Preparation of Al_2O_3-SiO_2-TiO_2-ZrO_2 Composite Ceramic Membranes by Sol-Gel Method

Al 2O 3-SiO 2-TiO 2-ZrO 2 supported membranes were prepar ed by Sol-Gel method. These composite ceramic membranes are level, even and no macro crack. There exist several crystalline phases such as Al 2O 3, TiO 2(a natase), Al 2SiO 5, and ZrO 2 in these membranes. Changing the molar ratio of Al∶Si∶Ti∶Zr,the kinds and content of crystal phases of composite membranes could be different, which may lead to a variety of microstructure of membranes. The surface nanoscale topography and microstructure of membranes were investiga ted by XRD,SEM,AFM,EPMA. The effects of additives and heat treatments on the sur face nanoscale topography and microstructure of composite ceramic membranes were also analyzed.

The Fouling Mechanism of Ceramic Membranes Used for Recovering TS-1 Catalysts

Ceramic ultrafiltration membranes were used to separate titanium silicalite-1 （TS-1） catalysts from the slurry of catalytic ammoximation of cyclohexanone to oxime. Silica was shown to have a great effect on membrane fouling in the alkaline environment of this system. In the ammoximation system, there are three main silica sources, which are residual silica on the catalyst particles surface during preparation, silica dissolved from TS-1 catalyst particles by ammonia solvent, and silica sol added into the reaction slurry to inhibit the dissolution erosion of the TS-1 catalyst. The silica dissolved by ammonia has been proved to influence membrane fouling most among the three silica sources. This was because the amount of silica dissolved by ammonia was the largest, and the polymerization of silica monomers at high concentration caused colloid particles formation, which led to a dense cake layer depositing on the membrane surface. Meanwhile, the size reduction of catalyst particles caused by alkaline dissolution also increased specific resistances of cake layers.

Superhydrophobic modification of ceramic membranes for vacuum membrane distillation

The hydrophobically modi fied ceramic membranes have great potential for energy-ef ficient membrane distillation.In this work,flat-sheet ceramic membranes with a superhydrophobic surface were fabricated by grafting 1H,1H,2H,2H-per fluorooctyltrichlorosilane or 1H,1H,2H,2H-per fluorodecyltriethoxysilane and followed by ultraviolet irradiation.The surface water contact angle was improved from 46° of original ceramic membrane to 159°,which exhibited a stable and excellent superhydrophobic effect.The modi fied membranes showed a high flux of 27.28 kg·m^(-2)·h^(-1) and simultaneously maintained an excellent retention rate of 99.99%,when used in vacuum membrane distillation process for treatment of a 1 wt% NaCl(75 °C) aqueous solution.These results suggested that superhydrophobic modi fication of ceramic surface is a facile and cost-effective way to achieve higher membrane distillation performance.The superhydrophobically-modi fied ceramic membrane with an excellent desalination capacity would show considerable potential in practical membrane distillation utilizations.

Multilayer Membranes Based on Ceramic Materials——Sol-gel Synthesis,Characterization and Membrane Performance

In nearly all chemical and petrochemical systems, separation of products generally accounts for more than 50% of the capital cost and the greatest part of the energy consumption. It is generally believed that membrane systems can offer benefits in both reducing the energy consumption of the separation stages and lowering the capital expenditure （CAPEX）. Microporous ceramic membranes have the potential to overcome the limitation in polymer membranes operation, which has been the subject of a large amount of research worldwide in the last two decades. And most of the research has aimed at the production of the asymmetric multilayered membrane based on amorphous oxides by sol-gel techniques. The paper is to give an overview of publications on ceramic membranes, including less common materials of titania, zirconia, which can be used for pervaporation in corrosive media. Commercially available microporous membranes based on these membrane materials and the membrane economics are also summarized.

Polymer/Ceramic Composite Membranes and Their Application in Pervaporation Process

Pervaporation(PV),as an environmental friendly and energy-saving separation technology,has been received increasing attention in recent years.This article reviews the preparation and application of macroporous ceramic-supported polymer composite pervaporation membranes.The separation materials of polymer/ceramic composite membranes presented here include hydrophobic polydimethylsiloxane(PDMS) and hydrophilic poly(vinyl alcohol)(PVA),chitosan(CS) and polyelectrolytes.The effects of ceramic support treatment,polymer solution properties,interfacial adhesion and incorporating or blending modification on the membrane structure and PV performance are discussed.Two in-situ characterization methods developed for polymer/ceramic composite membranes are also covered in the discussion.The applications of these composite membranes in pervaporation process are summarized as well,which contain the bio-fuels recovery,gasoline desulfuration and PV coupled proc-ess using PDMS/ceramic composite membrane,and dehydration of alcohols and esters using ceramic-supported PVA or PVA-CS composite membrane.Finally,a brief conclusion remark on polymer/ceramic composite mem-branes is given and possible future research is outlined.

Enhanced cross-flow filtration with flat-sheet ceramic membranes by titanium-based coagulation for membrane fouling control

Application of ceramic membrane(CM)with outstanding characteristics,such as high flux and chemical-resistance,is inevitably restricted by membrane fouling.Coagulation was an economical and effective technology for membrane fouling control.This study investigated the filtration performance of ceramic membrane enhanced by the emerging titanium-based coagulant(polytitanium chloride,PTC).Particular attention was paid to the simulation of ceramic membrane fouling using four widely used mathematical models.Results show that filtration of the PTC-coagulated effluent using flat-sheet ceramic membrane achieved the removal of organic matter up to 78.0%.Permeate flux of ceramic membrane filtration reached 600 L/(m2$h),which was 10-fold higher than that observed with conventional polyaluminum chloride(PAC)case.For PTC,fouling of the ceramic membrane was attributed to the formation of cake layer,whereas for PAC,standard filtration/intermediate filtration(blocking of membrane pores)was also a key fouling mechanism.To sum up,cross-flow filtration with flat-sheet ceramic membranes could be significantly enhanced by titanium-based coagulation to produce both high-quality filtrate and high-permeation flux.

Nanocomposite Membranes based on Perfl uorosulfonic Acid/Ceramic for Proton Exchange Membrane Fuel Cells

Perfl uorosulfonic acid/ceramic nanocomposite membranes were investigated as electrolytes for polymer electrolyte membrane fuel cell applications under low relative humidity. Different nanosized ceramics（SiO2, ZrO2, TiO2） with diameters in the range of 2-6 nm were synthesized in situ in Nafion solution through a sol-gel process and the formed nanosized ceramics were well-dispersed in the solution.The nanocomposite membranes were formed through a casting process. The nanocomposite membrane showes enhanced water retention ability and improved proton conductivity compared to those of pure Nafi on membrane. The mechanical strength of the formed nanocomposite membranes is slightly less than that of pure Nafi on membrane. The experimental results demonstrate that the polymer ceramic nanocompsite membranes are potential electrolyte for fuel cells operating at elevated temperature.

Carbon Capture from Flue Gas Based on the Combination of Non-Contact Hydrophobic Porous Ceramic Membrane and Bubbling Absorption

A hybrid system combined with a non-contact membrane and bubbling absorption is proposed to capture CO_(2) from flue gas.The non-contact way of membrane and liquid absorbent effectively avoids the reduction of gas diffusion flux through the membrane.High-porosity ceramic membranes in hybrid systems are used for gas-solid separation in fuel gas treatment.Due to the high content of H_(2)O and cement dust in the flue gas of the cement plant,the membrane is hydrophobically modified by polytetrafluoroethylene(PTFE)to improve its anti-water,anti-fouling,and self-cleaning performances.The results show that the diffusion flux of CO_(2) through the membrane is still higher than 7.0×10^(−3) mol/m^(2)s(20%CO_(2) concentration)even under the influence of water and cement dust.In addition,slaked lime selected as the absorbent is cheap and the product after bubbling absorption is nano-scale light calcium carbonate.To sum up,the hybrid system combining non-contact membrane and bubbling absorption is expected to be used to capture carbon dioxide from the flue gas of the cement plant.

Simultaneous generation of electricity, ethylene and decomposition of nitrous oxide via protonic ceramic fuel cell membrane reactor

Ethylene,one of the most widely produced building blocks in the petrochemical industry,has received intense attention.Ethylene production,using electrochemical hydrogen pump-facilitated nonoxidative dehydrogenation of ethane(NDE)to ethylene,is an emerging and promising route,promoting the transformation of the ethylene industry from energy-intensive steam cracking process to new electrochemical membrane reactor technology.In this work,the NDE reaction is incorporated into a BaZr_(0.1)Ce_(0.7)Y_(0.1)Yb_(0.1)O_(3-δ)electrolyte-supported protonic ceramic fuel cell membrane reactor to co-generate electricity and ethylene,utilizing the Nb and Cu doped perovskite oxide Pr_(0.6)Sr_(0.4)Fe_(0.8)Nb_(0.1)Cu_(0.1)O_(3-δ)(PSFNCu)as anode catalytic layer.Due to the doping of Nb and Cu,PSFNCu was endowed with high reduction tolerance and rich oxygen vacancies,showing excellent NDE catalytic performance.The maximum power density of the assembled reactor reaches 200 mW cm^(-2)at 750℃,with high ethane conversion(44.9%)and ethylene selectivity(92.7%).Moreover,the nitrous oxide decomposition was first coupled in the protonic ceramic fuel cell membrane reactor to consume the permeated protons.As a result,the generation of electricity,ethylene and decomposition of nitrous oxide can be simultaneously obtained by a single reactor.Specifically,the maximum power density of the cell reaches 208 mW cm^(-2)at 750℃,with high ethane conversion(45.2%),ethylene selectivity(92.5%),and nitrous oxide conversion(19,0%).This multi-win technology is promising for not only the production of chemicals and energy but also greenhouse gas reduction.

Hydrogen Permeation Properties of Perovskite-type BaCe_(0.9)Mn_(0.1)O_(3-δ)Dense Ceramic Membrane

The electrical conduction properties of dense BaCe0.9Mn0.1O3-d (BCM10) membrane were investigated in the temperature range of 600-900oC. High ionic and electronic conductivities at elevated temperatures make BCM10 a potential ceramic material for hydrogen separation. Hydrogen permeation through BCM10 membranes was studied using a high- temperature permeation cell. Little hydrogen could be detected at the sweep side. However, appreciable hydrogen can permeate through BCM10 membrane coated with porous platinum black, which shows that the process of hydrogen permeation through BCM10 membranes was controlled by the catalytic decomposition and recomposition of hydrogen on the surfaces of BCM10 membranes.

Oily Water Treatment by Ceramic Membrane: Modeling and Simulation

The separation process of oily water using membranes has attracted the attention of researchers and engineers. The greater problem in the use of membrane separation process is the reduction in permeate flux due to clogged pores by oil deposition inside the membrane or by the effect of the concentration polarization. For this purpose, a theoretical study of a water/oil separation module was performed. This device consists of a tubular ceramic membrane provided with a rectangular inlet section. Numerical simulations were performed using Ansys CFX software to solve the mass and momentum conservation equations in the fluid and porous domains. Here was adopted the RNG k-ε turbulence model. The effect of the membrane porosity and the inlet velocity of the fluid mixture on the two-phase flow behavior inside the separation module were evaluated. Results of the volumetric fraction, velocity and pressure fields of the oil and water phases are presented and analyzed. The results indicate a higher oil concentration within the membrane for the cases of higher porosity, and that the inlet fluid mixture velocity does not substantially affect the velocity profile within the separation module. It is found that the maximum separation efficiency of the module was obtained with feed velocity of 40 m/s and membrane porosity of 0.44.

Progress on Porous Ceramic Membrane Reactors for Heterogeneous Catalysis over Ultrafine and Nano-sized Catalysts

Heterogeneous catalysts with ultrafine or nano particle size have currently attracted considerable attentions in the chemical and petrochemical production processes, but their large-scale applications remain challenging because of difficulties associated with their efficient separation from the reaction slurry. A porous ceramic membrane reactor has emerged as a promising method to solve the problem concerning catalysts separation in situ from the reaction mixture and make the production process continuous in heterogeneous catalysis. This article presents a review of the present progress on porous ceramic membrane reactors for heterogeneous catalysis, which covers classification of configurations of porous ceramic membrane reactor, major considerations and some important industrial applications. A special emphasis is paid to major considerations in term of application-oriented ceramic membrane design, optimization of ceramic membrane reactor performance and membrane fouling mechanism. Finally, brief concluding remarks on porous ceramic membrane reactors are given and possible future research interests are also outlined.

Preparation of Monodispersed O/W Emulsion by Ceramic External Membrane Emulsification System——Preliminary Study on Integrated Ceramic Membrane Emulsification Reactor

A new reactor with integrated conventional slurry stirred reactor and ceramic external membrane emulsification system, was introduced in this paper. Toluene and toluene containing surfactant was separately used as dispersed phase for preparation of emulsions. Two kinds of emulsions were prepared and compared. The volume average sizes of prepared emulsions were 3.53μm and 3.6μm respectively. The results showed that the droplet sizes of two kinds of emulsions were similar, but the monodispersed emulsion was only obtained with addition of surfactant into the dispersed phase.

Feasibility analysis of SO_2 absorption using a hydrophilic ceramic membrane contactor

Hydrophilic ceramic membranes would be potential candidates for membrane gas absorption if they could be applied to appropriate separation processes.This study highlights a novel concept for the practical implementation of SO_2 absorption in hydrophilic ceramic membrane that exhibits outstanding thermal and mechanical stabilities.With this aim,we investigated experimentally the performance of SO_2 absorption into aqueous sodium hydroxide (NaOH) solution in a hydrophilic alumina (Al_2O_3) membrane contactor in terms of SO_2 removal efficiency and SO_2 mass transfer flux,and compared the performance with that in a hydrophobic one.A series of experiments were performed at various conditions over a NaOH concentration range of 0–1.0 mol·L^(-1),a liquid flow rate range of 30–180 ml·min^(-1),a gas flow rate range of 120–1000 ml·min^(-1),an inlet SO_2 concentration range of 400–2000μl·L^(-1),and a temperature range of 10–35°C.It was found that the hydrophilic membrane was more competitive when using a NaOH concentration higher than 0.2 mol·L^(-1).Furthermore,it can be inferred that the hydrophilicα-Al_2O_3 membrane exhibited exceptional long-term stability under 480 h continuous operation.

Effect of Cross-flow Velocity on the Critical Flux of Ceramic Membrane Filtration as a Pre-treatment for Seawater Desalination

Pre-treatment, which supplies a stable, high-quality feed for reverse osmosis （RO） membranes, is a criti- cal step for successful operation in a seawater reverse osmosis plant. In this study, ceramic membrane systems were employed as pre-treatment for seawater desalination. A laboratory experiment was performed to investigate the effect of the cross-flow velocity on the critical flux and consequently to optimize the permeate flux. Then a pilot test was performed to investigate the long-term performance. The result shows that there is no significant effect of the cross-flow velocity on the critical flux when the cross-flow velocity varies in laminar flow region only or in turbulent flow region only, but the effect is distinct when the cross-flow velocity varies in the transition region. The membrane fouling is slight at the permeate flux of 150 L·m^-2·h^-1 and the system is stable, producing a high-quality feed （the turbidity and silt density index are less than 0.1 NTU and 3.0, respectively） for RO to run for 2922.4 h without chemical cleaning. Thus the ceramic membranes are suitable to filtrate seawater as the pre-treatment for RO.

Preparation and Characterization of Alumina Membranes on Capillary Supports： Effect of Film-coating on Crack-free Membrane Preparation

Ceramic capillary membrane has received much attention due to its relatively high pack density and favorable mechanical strength.However,it is difficult to prepare capillary membrane on its thin support by a dip-coating method.In this study,alumina microfiltration membranes were prepared on the inner surface of alumina capillary support(outer diameter 4 mm,inner diameter 2.5 mm)by a dip-coating method.Scanning electron microscopy(SEM)observation,gas bubble pressure(GBP)method and membrane permeation test were carried out to evaluate membrane performance.Two major effects in preparation of crack-free membrane,capillary filtration and film-coating,upon the thin support were studied.The as-prepared crack-free membrane presents a narrow pore size distribution,a mean pore size of about 0.6μm and a high pure water flux of 86000 L·m -2 ·h -1 ·MPa.It is proved that the membrane thickness should be sufficiently large to overcome the defects of support surface,but it is only one of the prerequisites for the formation of crack-free membrane.Furthermore,it is demonstrated that the capillary filtration effect is greatly restricted for thin capillary support with the dip-coating method and the film-coating effect plays a crucial role in the formation of crack-free membrane.

CFD simulation of flow field and resistance in a 19-core tandem ceramic membrane module

CFD simulation of the permeation process of a 19-core tandem ceramic membrane module was established to investigate flow field and resistance and its change in permeate flux to the membrane element position and the channel of each membrane element.The results show that when the volume flow rate changes from26 m3·h-1 to 89 m3·h-1,the resistance of each part of the membrane module increases gradually.The increase in resistance loss in the membrane element is faster than the plates and the bell mouths.In a single ceramic membrane module,the maximum difference in flow rate of each membrane tube is 7.23%.In a single membrane tube,the outer ring channels 3–5,3–6,3–7,3–8 are relatively slow.The maximum mass flow deviation from the mean is 2.7%.This work helps to clarify the flow mechanism within the modules,optimize the structure of the equipment and provide a reliable basis for the improvement of industrial ceramic membrane modules.

Zwitterionic monolayer grafted ceramic membrane with an antifouling performance for the efficient oil-water separation

Enormous demands on the separation of oil/water(O/W)emulsions in various industries,such as petrochemical,food and pharmaceutical industries,are looking for high performance and energy-efficient separation methods.Ceramic membranes have been used to deal with O/W emulsions,for its outstanding characteristics of easy-operation,high-flux,and long-term stability.However,membrane fouling is still a challenge in the industrial application of ceramic membranes.Herein,antifouling ceramic membranes were fabricated by grafting zwitterions on the membrane surface via an environment-friendly two-step grafting method,which improves the antifouling property and permeability.Successful grafting of such zwitterion on the ceramic surface was assessed by the combination of FTIR and XPS characterization.More importantly,the hydration can be formed by electrostatic interactions layer on the modified membrane,which was confirmed by TGA characterization.The antifouling performance of prepared zwitterionic ceramic membranes in the separation of O/W emulsions was systematically tested.The results suggested that zwitterion can significantly improve the flux of ceramic ultrafiltration membrane,and can also improve antifouling property dramatically by reducing the irreversible fouling in the separation of O/W emulsions.Therefore,zwitterionic ceramic membranes hold promising potentials as an antifouling,highly efficient and green method in the practical purification of the O/W emulsions.

River Water Purification via a Coagulation-Porous Ceramic Membrane Hybrid Process

Membrane filtration technology combined with coagulation is widely used to purify river water.In this study,microfiltration(MF)and ultrafiltration(UF)ceramic membranes were combined with coagulation to treat local river water located at Xinghua,Jiangsu province,China.The operation parameters,fouling mechanism and pilot-scale tests were investigated.The results show that the pore size of membrane has small effect on the pseudo-steady flux for dead-end filtration,and the increase of flux in MF process is more than that in UF process for cross-flow filtration with the same increase of cross-flow velocity.The membrane pore size has little influence on the water quality.The analysis on membrane fouling mechanism shows that the cake filtration has significant influence on the pseudo-steady flux and water quality for the membrane with pore size of 50,200 and 500 nm.For the membrane with pore size of 200 nm and backwashing employed in our pilot study,a constant flux of 150L·m 2·h 1was reached during stable operation,with the removal efficiency of turbidity,total organic carbon(TOC)and UV254 higher than 99%,45%and 48%,respectively.The study demonstrates that coagulation-porous ceramic membrane hybrid process is a reliable method for river water purification.

Easy Fabrication of Dense Ceramic Membrane for Oxygen Separation

A combined EDTA-citrate complexing method was developed for the easy preparation of mixed oxygen-ionic and electronic conducting dense ceramic membrane for oxygen separation. The nea method takes the advantage of lower calcination temperature for phase formation. lower membrane sintering temperature and higher relative density over the standard ceramic method.