Ceramic Ultrafiltration Membrane Research Articles

Mo-BiVO4 Photocatalytically Modified Ceramic Ultrafiltration Membranes for Enhanced Water Treatment Efficiency.

This study highlights the effectiveness of photocatalytically modified ceramic ultrafiltration (UF) membranes in alleviating two major drawbacks of membrane filtration technologies. These are the generation of a highly concentrated retentate effluent as a waste stream and the gradual degradation of the water flux through the membrane due to the accumulation of organic pollutants on its surface. The development of two types of novel tubular membranes, featuring photocatalytic Mo-BiVO4 inverse opal coatings, demonstrated a negligible impact on water permeance, ensuring consistent filtration and photocatalytic efficiency and suggesting the potential for maintaining membrane integrity and avoiding the formation of highly concentrated retentate effluents. Morphological analysis revealed well-defined coatings with ordered domains and interconnected macropores, confirming successful synthesis of Mo-BiVO4. Raman spectroscopy and optical studies further elucidated the composition and light absorption properties of the coatings, particularly within the visible region, which is vital for photocatalysis driven by vis-light. Evaluation of the tetracycline removal efficiency presented efficient adsorption onto membrane surfaces with enhanced photocatalytic activity observed under both UV and vis-light. Additionally, vis-light irradiation facilitated significant degradation, showcasing the versatility of the membranes. Total Organic Carbon (TOC) analysis corroborated complete solute elimination or photocatalytic degradation without the production of intermediates, highlighting the potential for complete pollutant removal. Overall, these findings emphasize the promising applications of Mo-BiVO4 photocatalytic membranes in sustainable water treatment and wastewater remediation processes, laying the groundwork for further optimization and scalability in practical water treatment systems.

Investigating effective strategies for sustainable operation of a submerged anaerobic membrane bioreactor (SAnMBR) coupled with ceramic ultrafiltration membrane

This study presents a mechanistic approach to explore the key operational parameters governing the flux performance of an SAnMBR system coupled with a ceramic flat-sheet ultrafiltration membrane. Experiments were conducted at mixed liquor suspended solid (MLSS) concentrations of 12, 18, and 24 g/L using biogas sparging, backwashing, and a combination of both to investigate the most effective fouling mitigation strategy by exploring the fouling mechanism at a critical flux regime. To validate the experimental findings, a mathematical model was used to simulate the time-based variation of membrane effective pore radius (m), decrease in membrane porosity (%), thickness of cake layer (m), and membrane resistance (1/m). The study found that at a low biomass concentration, there was a sharp decline in the membrane pore radius leading to an increase in membrane resistance in the absence of any fouling mitigation strategies. However, by implementing these strategies individually and in combination, they maintained a higher pore radius and controlled the increase in membrane resistance even at high biomass concentrations. It was observed that biogas sparging outperformed the conventional backwashing strategy and the SAnMBR system exhibited superior performance attaining higher flux rates for prolonged duration. The advanced spectroscopic analysis confirmed the presence of a higher concentration of polysaccharides responsible for cake layer biofouling, and significant pore blocking due to inorganic foulants at high biomass concentrations. This suggests that the SAnMBR system must be operated at optimised biomass levels below the critical flux for sustained operation. Additionally, the key operational parameters identified using the mathematical model provide a precise assessment of SAnMBR performance, to improve its design efficiency for field applications.

Rapid thermal process for fabricating α-alumina tight ultrafiltration membrane with narrow pore size distribution

The development of tight ceramic ultrafiltration membranes for water purification facilitates is challenging because of high fabrication costs and low permeate flux. In this study, a low-energy rapid thermal process (RTP) was comprehensively investigated for fabricating of high-precision, permeable α-alumina tight ultrafiltration membranes. Compared to the conventional thermal process (CTP), RTP offers an ultra-fast heating rate and shorter holding time, effectively mitigating grain growth and pore aggregation. Moreover, the decomposition of organic matter is delayed during RTP, providing a lower interfacial energy that enables direct formation of α-alumina at a low temperature of 750 °C. During a secondary subsequent RTP, the residual phase is fully converted to α-alumina by the in-situ seeding effect. By utilizing RTP, we successfully prepared α-alumina ultrafiltration membranes within 30 min by calcination, with an average pore size of approximately 6 nm, a narrow pore distribution coefficient of 1.12, and high permeance of 219 L−1·m−2·h−1·bar−1.

Fractionation of Glycans from Hot‐Water Extracts with Ceramic Ultrafiltration Membranes

AbstractExtraction of hemicelluloses from biomass with pressurized hot‐water employs the mechanism of autohydrolysis for molecular weight reduction. In a pilot‐scale extraction of depectinized apple pomace, molecular weight was 30 kDa with a broad mass distribution including monomers and their degradation products. Ultrafiltration with sequential use of ceramic membranes with decreasing cut‐off yielded a suitable fraction with molecular weight of 9 kDa representing 10 % of the extracted hemicelluloses. Further autohydrolytic treatment of the extracted hemicellulose decreases molecular weight while increasing the mass of degradation products. For a series of hydrolysates sequential filtration through ceramic membranes was further tested for fractionation and purification. The efficiency of this fractionation was analyzed by size exclusion chromatography and a total mass balance of the ultrafiltration process is given as an evaluation for suitability of purifying and fraction glycans.

Pretreatment of Glucose-Fructose Syrup with Ceramic Membrane Ultrafiltration Coupled with Activated Carbon.

Ceramic membranes are applied to remove non-sugar impurities, including proteins, colloids and starch, from glucose-fructose syrup that is dissolved from raw sugar using acid. The performance of ceramic membranes with 0.05 μm pores in clarifying high-fructose syrup was investigated under various operating conditions. The flux decreased rapidly at the start of the experiment and then tended to stabilize at a temperature of 90 °C, a transmembrane pressure of 2.5 bar, and cross-flow velocity of 5 m/s under total reflux operation. Moreover, the steady-state flux was measured at 181.65 Lm-2 h-1, and the turbidity of glucose-fructose syrup was reduced from 92.15 NTU to 0.70 NTU. Although membrane fouling is inevitable, it can be effectively controlled by developing a practical approach to regenerating membranes. Mathematical model predictions, scanning electron microscopy, energy dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy revealed that foulants primarily responsible for fouling are composed of polysaccharides, proteins, sucrose, phenols, and some metal elements, such as calcium, aluminum, and potassium. Due to the removal of suspended colloidal solids, the membrane-filtered glucose-fructose syrup was decolorized using activated carbon; the filtration rate was effectively improved. A linear relationship between volume increase in syrup and time was observed. A decolorization rate of 90% can be obtained by adding 0.6 (w/w) % of activated carbon. The pretreatment of glucose-fructose syrup using a ceramic membrane coupled with activated carbon results in low turbidity and color value. This information is essential for advancing glucose-fructose syrup and crystalline fructose production technology.

Treatment of highly saline effluents laden with organic pollutants using ceramic ultrafiltration membranes and application to leachate treatment

The aim of this study is to assess the efficacy of three ultrafiltration ceramic membranes with distinct porosities (20, 50, and 100 nm) in treating highly charged effluents and their potential application in leachate treatment. In the initial phase, Response Surface Methodology (RSM) was employed using a solution containing NaCl (TDS = 20 g/L) and glucose (mass concentration (Cm) = 10 g/L). The investigation focused on operational parameters, specifically Circulation velocity (CV) and volumetric concentration factor (VCF). The responses considered encompass permeate flux (PF) and retention (R). In the subsequent phase, as part of a practical application, leachate was subjected to treatment, and the fouling mechanisms specific to each membrane were identified. The Hermia model was employed, distinguishing between four fouling modes: cake formation, intermediate blocking, pore constriction, and complete blocking. The results demonstrate that, during the treatment of the synthetic solution, VCF has a more significant influence on both responses compared to CV. Furthermore, CV impacts the critical flux of the three membranes, without affecting the retention of suspended matter (SS). When treating the leachate, removal efficiencies of 55%, 51%, and 47% for COD and 36%, 33%, and 29% for SS were achieved for membranes with porosities of 20 nm, 50 nm, and 100 nm, respectively. Modeling the flux over time showed that fouling of these three UF membranes is superficial, and the main fouling mechanism is cake formation.

A CuO-modified ultrafiltration ceramic membrane inducing micro-nano bubble collapse to generate hydroxyl radicals for enhancing pollutant removal

It is desirable to develop ceramic membranes with functional performances for wastewater treatment. This work developed a CuO-modified Al2O3 ceramic membrane (CuO/Al2O3 CM) via a sol-gel method. The coated CuO particles provided hydrophobicity and a high zero point of charge for CM, which could accumulate H+ ions and form a liquid depletion layer on the membrane surface. When coupled with micro-nano bubbles (MNBs) in a neutral aqueous solution, the modified CM led to MNBs collapse through the accumulation of H+ and uneven expansion. This collapse generated high temperature sites that activated the CuO particles, leading to the production of reactive oxygen species (ROSs) through the interaction of CuO and surface OH–. Therefore, the modified CM could remove model pollutants (methylene blue) in a stable and high efficiency (88.91 %) through inducing MNBs collapse. Besides, the tests on the pure water flux, reusability and leaching revealed the modified CM had good fouling resistance, stability, and environmental friendliness. Mechanism analysis showed the ROSs, mainly hydroxyl radicals (·OH), were responsible for the methylene blue degradation. This work provides valuable insights into the development of functionalized membranes that can induce MNB collapse to enhance pollutant removal in wastewater treatment.

The pre-coated photocatalytic ceramic membrane with Bi2O3–TiO2/powdered activated carbon nanoparticles to alleviate ultrafiltration fouling caused by intracellular organic matter of Microcystis aeruginosa

Algal intracellular organic matter (IOM), released during algae's normal growth phase and water treatment processes, has long been a source of significant membrane fouling, considerably limiting the effective use of ultrafiltration(UF) technology. In this study, a Bi-doped TiO2 composite with powdered activated carbon (Bi2O3–TiO2/PAC) was loaded on ceramic UF membranes by vacuum filtration, and the prepared photocatalytic modified ceramic membranes (MCMs) were investigated for the removal of IOM and the mitigation of membrane fouling at different loading levels and under three operating conditions: Dark, Dark-UV, and UV. The results showed that the photocatalytic MCMs were able to remove the protein and humic acid fluorescent components of IOM and decompose or mineralize organic matter with molecular weights of 10–50 kDa. Under the Dark, Dark-UV, and UV conditions, the final normalized flux of MCM-2.88 was significantly increased by 22.6 %, 82.1 %, and 108.0 %, respectively. The hydrophilicity of MCMs not only transformed the interactions between IOM and the membrane into repulsive forces, but also the composite material on the membrane surface transforms the membrane fouling mechanism from intermediate blocking model to cake layer formation. Furthermore, the application of photocatalytic oxidation under the Dark-UV and UV conditions yielded a reduction in both reversible and irreversible fouling. This action led to an increased hydrophilicity and elevated free energy of adhesion with IOM during the filtration process. Moreover, the main fouling mechanism changed into complete or intermediate blocking. These outcomes collectively underscore the capability of MCMs to alleviate membrane fouling induced by IOM. This advancement holds substantial promise for the advancement and widespread implementation of photocatalytic ceramic membrane filtration techniques.

Synthesis and application of modified membranes for efficient cationic and anionic dye elimination

This study focuses on developing ceramic ultrafiltration membranes using locally sourced kaolin clay and feldspar. An active layer composed of graphene and alkoxide is added to enhance the performance of these clay supports. This layer is thin, porous, and can vary in thickness. The support and filter layer's porous properties are characterized using SEM, DRX, ATG/ATD, XPS, and FTIR techniques. Filtration tests are conducted on modified porous tubular supports using cationic and anionic dye solutions. The filtration is performed tangentially at a pressure of 3.5 bar and a processing time of 120 minutes. The retention rates of the colored solutions are measured using a UV-visible spectrophotometer. The results show a 100% retention rate for supranol yellow and orange II at a concentration of 10-4 M, while for crystal violet and malachite green, the retention rates are 92.03% and 95.30%, respectively.

Investigating the impact of stormwater fouling on polysulfone ultrafiltration membranes modified with deep eutectic solvents

In this study, we evaluate the performance of modified polysulfone (PSF) ultrafiltration (UF) membranes, which incorporate deep eutectic solvents (DES), in treating stormwater laden with natural organic matter e.g. chemical oxygen demand (COD) and total suspended solids (TSS). We also aim to understand how these organic substances, e.g. COD, TSS, from the water source contribute to the fouling of the synthesized membranes. PSF membranes were synthesized using a non-solvent induced phase separation technique and integrated with varying concentrations of ChCl:FR (Choline Chloride: D-(−)-Fructose) 1:1 DES. The surface and porous structures of the membranes were characterized through Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), contact angle measurements, scanning electron microscopy (SEM), and mechanical testing. The UF performance of these membranes was assessed and compared with different commercially available UF flat sheet membranes in terms of pure water permeability and antifouling behavior against collected stormwater from a sedimentation pond. Furthermore, the study evaluated the quality of the permeate based on parameters such as COD, turbidity, TSS, pH, and conductivity and compared the permeate quality of a pilot-scale ceramic UF membrane unit. The findings indicate that the inclusion of DES in the polysulfone membrane structure enhances the membranes' antifouling properties and permeability. This research offers valuable insights into the role of DES in the formation of polysulfone UF membranes and their potential for practical use e.g. sedimented stormwater.

Membrane fouling monitoring by 3ω sensing

Membrane fouling significantly reduces membrane permeability, leading to higher operational expenses. In situ monitoring of membrane fouling can potentially be used to reduce operation cost by optimizing operational parameters and cleaning conditions. In this study, a platinum wire with a diameter of 20 µm was attached to the surface of a ceramic ultrafiltration membrane, and by measuring the voltage across the wire while applying an AC current, the amplitude of the third harmonic wave, the so-called 3ω signal, was obtained. Results showed increasing 3ω signals during formation of fouling layers, which correlates directly to the hydraulic resistance of the formed fouling layer in semi-dead end filtration of polymeric core shell particles and crossflow filtration of diluted milk. This is explained by the insulating effect of the fouling layers which reduces heat convection by crossflow and the different thermal conductivity in the fouling layer compared with the feed. After membrane cleaning, the permeability and the magnitude of the 3ω signal were partly restored, showing that the 3ω method can be used to monitor the effect of cleaning. The frequency of the AC current was varied so it was possible to measure the heat conductivity in the fouling layer (high frequency) and heat convection due to cross-flow (low frequency). This may potentially be used to get information of the type of fouling (heat conductivity) and thickness of the fouling layer (AC frequency where heat conductivity becomes dominating).

Hybrid ceramic nanofiltration membranes prepared by impregnation and solid-state grafting of organo-phosphonic acids

Grafting of oligomers into the mesopores of ceramic membranes (e.g. γ-alumina) represents an attractive strategy for deploying durable, resistant, and efficient hybrid membranes for the industrial treatment of wastewater containing organic solvents and divers solutes. In general, to control the membrane/solute/solvent interactions, homogeneous surface modification and high grafting yields are required. However, reaching this goal is rather challenging with the current grafting approaches where the active diffusion of the oligomers to the membrane pore surface may be hampered. To mitigate such diffusion limitation, we present here a novel synthesis method consisting of an infiltration of concentrated PEG organophosphonic acid oligomer solution in ceramic ultrafiltration membranes before initiating the solid-state grafting reaction to form a PEG-brush-grafted nanofiltration ceramic membrane. The infiltration step was found to be decisive for the formation of weak bonds between the oligomer linking functions and the ceramic membrane ensuring the final synthesis of robust PEG-based membranes by a grafting reaction. The influence of the solvent polarity (water vs. cyclohexane) on the conformation of the grafted PEG brush inside the γ-alumina mesopores was observed as a key parameter in the analysis of the pore size and permeability results. In addition to this, it was studied here for the first time by molecular dynamic simulations. The as-prepared PEG-brush/ceramic membranes were found very efficient in the separation of small organic dyes such as Rhodamine B (479 g mol−1) up to 85%. As a result, the present synthesis method represents a sustainable and simple alternative way for the preparation of hybrid nanofiltration membranes with controlled surface properties and attractive separation performance. Moreover, the vacuum impregnation and solid-state grafting approach requires a minimal amount of functional oligomers and solvent (0.5 mmol for 2–3 mL of solvent) and can be applied to other porous materials used in separation technologies.

New insight into the irreversible membrane fouling in different pore-sized ultrafiltration ceramic membrane bioreactors (UCMBRs) for high-strength textile wastewater treatment

Despite great achievements in ceramic membrane bioreactor applications, membrane fouling, which decreases the permeability and separation performance of bioreactors and is associated with increased operational costs and energy consumption, remains a problem. The aim of this study was to expand our understanding of the fouling behavior in the long-term performance of ultrafiltration ceramic membrane bioreactors (UCMBRs) for high-strength textile wastewater reclamation. Using real textile wastewater effluent, the effects of ultrafiltration (UF) membrane pore sizes, cleaning strategies, and foulant distribution were systematically evaluated over more than three months of continuous operation. The results showed that UCMBR system achieved chemical oxygen demand and total nitrogen removal efficiencies as high as 91–95% and 39–43%, respectively. The high PN concentration can easily increase the viscosity of mixed liquor samples, contributing to a fouling layer on the membrane surface. In addition, the fouling layer formed on the surface of small-pore-sized ceramic UF membranes was not completely reversible but was difficult to eliminate by simple physical cleaning. Soluble extracellular polymeric substances, especially proteins and low molecular weight neutrals, remained, resulting in irreversible fouling on the UF membrane. However, saturated CO2 backwash showed great potential for enhancing the system through efficient fouling control without using environmentally unfriendly cleaning chemicals. The cake-intermediate and complete-standard models were suitable for explaining the fouling mechanism in the large- and small-pore-sized UF membranes, respectively.

Ozone micro-bubble aeration using the ceramic ultrafiltration membrane with superior oxidation performance for 2, 4-D elimination

Micro-bubble aeration is an efficient way to promote ozonation performance, but the technology is challenged by extensive energy cost. Here, a ceramic ultrafiltration membrane was used to achieve ozone micro-bubble (0–80 µm) aeration in a simple way at gaseous pressures of 0.14–0.19 MPa. Compared with milli-bubble aeration, micro-bubble aeration increased the equilibrium aquatic O3 concentrations by 1.53–3.25 times and apparent O3 transfer rates by 3.12–3.35 times at pH 5.0–8.0. Consequently, the •OH yield was 2.67–3.54 times via faster O3 transfer to the aquatic solution followed by decomposition rather than interfacial reaction. Ozone micro-bubble aeration outperformed milli-bubble aeration, with the degradation kinetics of 2,4-D being 3.08–4.36 times higher. Both O3-oxidation and •OH oxidation were important to the promotion with the contributions being 35.8%-45.9% and 54.1%-64.2%, respectively. The operational and water matric conditions influenced the oxidation performance via both O3 oxidation and •OH oxidation, which is reported for the first time. In general, the ceramic membrane offered a low-energy approach of ozone micro-bubble aeration for efficient pollutant degradation. The O3 oxidation and •OH oxidation were proportionally promoted by ozone micro-bubble due to O3 transfer enhancement. Thus, the promotive mechanism can be interpreted as the synchronous enchantment on ozone exposure and •OH exposure for the first time.

Comparison of ceramic microfiltration and ultrafiltration membranes for the clarification of simulated sebacic acid fermentation broth

Sebacic acid, an important chemical intermediate, is usually prepared by fermentation. However, the composition of the fermentation broth is complex, which causes significant difficulties in the purification of the product and is still a key problem in the industry. In this study, the application of ceramic membranes for the separation and purification of simulated fermentation broth was studied. Ceramic microfiltration (MF) and ultrafiltration (UF) membranes with average pore sizes of 100 and 6 nm, respectively, were systematically compared by analyzing their separation effects on different components in the fermentation broth and their permeation flux during filtration. Both ceramic MF and UF membranes can be used to clarify the fermentation broth with turbidity less than 0.01 NTU by the effective removal of emulsified oil and bacteria while allowing sodium sebacate to pass through freely. However, the ceramic UF membrane showed a higher protein rejection of more than 95%, whereas the removal rate of the MF membrane was only approximately 20%. In addition, the fouling process of ceramic UF membrane was analyzed. In the suitable operating conditions when the pH was 9.2, the temperature was 60 ℃, the pressure was 0.1 MPa and the cross-flow velocity was 1.8 m·s−1, the membrane fouling process was dominated by the reversible cake formation. A ceramic UF membrane with a smaller pore size can effectively avoid pollution in pore channels, and thus exhibits a higher permeation flux in the filtration of the fermentation broth.

Aerobic treatment of fish canning wastewater using a pilot-scale external membrane bioreactor

Fish canning wastewater is characterized by high salinity and organic matter, which makes its treatment particularly difficult. To this purpose, the use of an aerobic membrane bioreactor (AeMBR) process could be a perfect option for the treatment of this wastewater. The aim of this study was to evaluate the effect of different operational conditions on the performance of the biological process and ceramic ultrafiltration (UF) membrane in AeMBR pilot plant for fish canning wastewater treatment. The AeMBR pilot was operated under ambient conditions (21.5 °C), 12 days of sludge retention time (SRT) and for a hydraulic retention time (HRT) of 24 h. The effect of operational parameters including organic loading rate (OLR) (3–5 kg COD/m3.day); total dissolved solids (TDS) (2.5–5 g/L), oxygenation rate (700 and 1300 NL/h) and transmembrane pressure (TMP) (0.05–1.5 bar) affected the quality of the effluent. The main performance results were the removal of approximately 97% of COD, 98% of BOD, 90% of nitrate and over 97% of total Kjeldahl nitrogen (TKN) and total phosphorus (TP). The treated effluent at the output of the AeMBR meets the quality standards according to the Food and Agriculture Organization (FAO) directive and the Moroccan standards for the discharge and reuse of water for irrigation and watering.

Hierarchical membrane by centrifugal casting and effects of incorporating activated carbon as pore-former

Producing ceramic asymmetric membranes usually requires several steps to prepare macroporous support and then the selective layer deposition. This process is energy and time-consuming, which is expensive. In this sense, the one-step centrifugal casting technique is an interesting alternative. Therefore, this work aimed to prepare ultrafiltration ceramic membranes by the centrifugal casting method, investigating the effect of a pore-forming agent on membrane performance. Different concentrations of activated carbon were used in the alumina suspension, and then the tubes were molded, dried, and sintered. The membranes' shrinkage, morphology, apparent porosity, hydraulic permeance, and BSA protein retention were evaluated to identify the effect of using the pore-forming agent. The membrane prepared without activated carbon rejected 91% of the BSA molecules (66 kDa), indicating its molecular weight cut-off. Using more than 2.5% of activated carbon increased the porosity and hydraulic permeance of the membranes, but at the expense of low BSA retention.

Integrated Membrane-adsorption system as a sustainable development approach for semiconductor-industry wastewater treatment

Conventional coagulation and flocculation processes applied for semiconductor industry wastewater treatment contributes to high operating cost due to the use of chemical coagulant and the need of schedule waste disposal. On top of that, precious nano-sized silica particles contain in the semiconductor-industry wastewater is also unable to recover through these processes. The aim of this study is to investigate the efficiency of integrated membrane-adsorption system as a sustainable development approach for semiconductor-industry wastewater treatment. The integrated system consists of two stages, membrane filtration unit followed by GSC adsorption unit. Membrane filtration unit mainly use for the wastewater treatment and silica recovery, whereas GSC is further use for the polishing of semiconductor-industry wastewater. The performance of integrated membrane-adsorption system is evaluated based on the rejection of different water quality parameters. Ceramic ultrafiltration membranes at 0.02 µm and 0.1 µm pore size were tested, while GSC adsorption was performed at three different bed heights (2 cm, 4 cm, and 6 cm). 0.02 µm membrane has greater rejection than 0.1 µm membrane with the removal of 99.25 % TSS, 99.53 % color, 99.91 % turbidity, 100 % COD, 93.97 % ammonia–nitrogen, and 99.8 % nitrate-nitrogen. For the system with a 6 cm bed height, further GSC adsorption achieved excellent results, with the removal of 100 % TSS, 99.8 % color, 99.98 % turbidity, 100 % COD, 97.5 % ammonia–nitrogen, and 99.89 % nitrate-nitrogen. The semiconductorindustry wastewater treatment employing an integrated membrane-adsorption system manage to produce treated water comply to Singapore's NEWater Quality which able to recycle and reuse internally in semiconductor industry.

Improved negative charge of tight ceramic ultrafiltration membranes for protein-resistant and easy-cleaning performance

Fouling caused by adsorption is a challenge in protein separation and purification using membrane technology. The interaction between the membrane surface and proteins is significant for developing antifouling modified membranes. In this study, a negative ZrO2 tubular ceramic membrane was constructed by grafting polyacrylic acid (PAA) to mitigate protein fouling. PAA of 2000 Da had little effect on the membrane pore and surface wettability, as characterized by XPS, dextran retention, contact angle, and water permeance. The protein resistance of the modified membrane was investigated by protein filtration. The modified membranes had a higher stable normalized flux (0.6) and flux recovery ratio (90 %) than that of the original membrane. In addition, the performance of the modified membranes was sensitive to the pore sizes of the original membranes. When the original membrane was unable to completely reject bovine serum albumin (BSA), the weak interaction between BSA and the membrane pores would reduce rejection after PAA modification. And the flux recovery ratio of modified membrane increased by 55 %. Overall, PAA modification reduces irreversible fouling by electrostatic repulsion, and improves the protein-resistant and easy-cleaning performance of ceramic membranes.

Synthesis and characterization of tubular ceramic ultrafiltration membrane from coal fly ash

AbstractIn this study, a tubular ceramic ultrafiltration membrane was synthesized using coal fly ash (CFA) along with fuller clay and a small quantity of inorganic precursors by extrusion method. The composition of membrane precursors was varied to prepare the ceramic membranes which were named as CM1, CM2 and CM3. Thermogravimetric analysis (TGA) confirmed high thermal stability nature of the membranes. The insignificant weight loss (<0.5%) of the membranes in a highly acidic and alkaline medium showed the high chemical resistance of the ceramic membranes. Mullite and Quartz was identified as significant phases of synthesized membranes via XRD analysis. The high negative charge of ceramic membranes was observed by Zeta potential analysis. Molecular weight cut‐off (MWCO) of CM1, CM2, and CM3 membranes were estimated as 59, 50.3 to 36.6 kDa, respectively. The proportion of fuller clay significantly influenced the membrane properties such as porosity, pore size, and hydraulic permeability. The pure water flux of the membranes was increased with increase of applied pressure from 69 to 345 kPa. The maximum water flux was obtained as 11.7 × 10−5 m3/m2 s at 345 kPa for CM1. The pore size and porosity of the membranes were decreased from 131 to 96 nm and 57.68% and 44.8% while increasing the fuller clay from 8% to 12% in the membrane (CM1 to CM3), respectively. The results obtained in this study demonstrate that the CM3 tubular ceramic membrane can be successfully used for various ultrafiltration applications.