Ceramic Microfiltration Membranes Research Articles

Pore-scale numerical study of intrinsic permeability for fluid flow through asymmetric ceramic microfiltration membranes

The asymmetric ceramic microfiltration (MF) membrane is widely used in water treatment processes, yet the dependence of its intrinsic permeability on the microstructure parameters of different layers are not thoroughly understood. In this study, a numerical model combining the Discrete Element Method (DEM) with Lattice Boltzmann Method (LBM) is developed to simulate the fluid flow through the detailed pore structure of an asymmetric ceramic MF membrane. The model is validated by comparing the simulated pure water permeability to experimental data with an average deviation of 8% (Max∼25%). The simulation results show that the pore size D50 and porosity ε, of the top and intermediate layers are dominant microstructure parameters that determine the membrane pure water permeability. A new asymmetric ceramic MF membrane intrinsic permeability Km as a function of D50, ε and layer thickness h of both top and intermediate layers is derived. The verification of this Km correlation is conducted by comparison with experimental data and Carman-Kozeny (C–K), Hagen-Poiseuille (H–P) correlations, indicating the proposed Km correlation can accurately predict the membrane permeability. It provides a useful tool for a fundamental understanding of the effect of membrane microstructures on intrinsic permeability.

A Novel ceramic tubular membrane coated with a continuous graphene-TiO2 nanocomposite thin-film for CECs mitigation

This work presents a ceramic tubular membrane coated with a continuous graphene-TiO2 nanocomposite thin-film for contaminants of emerging concern (CECs) removal from synthetic and real matrices in single-pass flow-through operation. Microfiltration ceramic membranes were coated in situ with graphene (G)-TiO2-P25 nano-composite using two different methods: Membrane type A - TiO2-P25 incorporated in the G preparation stage (1% [MA-1], 2% [MA-2] and 3% [MA-3] [w/v]), and Membrane type B - TiO2-P25 thin-film uniformly coated over the G film surface (coating layers: 3 [MB-1], 6 [MB-2], and 9 [MB-3]). After the catalyst deposition and before the pyrolysis step, air was forced to pass through the membranes pores (inside-outside mode), providing a porous film. The CECs solution (diclofenac-DCF, 17β-estradiol-E2, 17α-ethinylestradiol-EE2 and amoxicillin-AMX) was prepared using Ultrapure water (UPW) or an urban wastewater after secondary treatment (UWW) fortified with 500 µgL−1 of each CEC. Membranes were characterized by the following techniques: Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier-Transform Infrared spectroscopy (FTIR), Diffuse Reflectance UV-Visible spectroscopy (DR UV-Vis) and Raman spectroscopy. The membranes coated with MA-3 and MB-2 catalyst films, irradiated by UVA light, showed the highest ability for CECs removal. Furthermore, the Relative flux reduction ratio (RFR) decreased around 45% in the absence of UVA light, owing to membrane fouling. The combination of filtration and oxidation (G-TiO2-UVA) provided a permeate with higher quality and minimized membrane fouling. Although membrane type B allowed for a permeate with higher quality, membrane type A provided a higher permeate flux.

Impact of C-CVD synthesis conditions on the hydraulic and electronic properties of SiC/CNTs nanocomposite microfiltration membranes

In this study, commercial SiC ceramic microfiltration membranes were coated with carbon nanotubes (CNTs) using chemical vapor deposition (CVD) to obtain a conductive and hydrophobic membrane material. In order to have better control of the surface and electronic properties of the developed material, two adjacent fractional factorial designs (25-2) were implemented to quantify CNTs synthesis parameters influence. The design of experiments revealed that the quantity of the synthesized CNTs was mainly controlled by CVD temperature, duration and iron catalyst concentration. The structure of the CNTs layer was mainly controlled by CVD temperature within the investigated parameter range (650–850 °C). It was demonstrated that pure water permeability was anti-correlated with CNTs synthesis yield due to an increase in membranes' hydrophobicity and potential pore blockage. The membrane coated with the largest amount of CNTs was obtained at 850 °C for a duration of at least 1 h and showed relatively low electrical resistance and good microwave absorption. Finally, such tunable nanocomposite material has the potential to further improve the filtration performances and membranes widespread application.

Manufacture of Layered-type MF Ceramic Membrane for Advanced Wastewater Treatment and its Fouling Control using Modularized Mechanical Scraper

In this study, a novel layered-type microfiltration (MF) ceramic membrane for advanced wastewater treatment was fabricated; composed of the support, buffer layer, and active layer. The buffer and active layers allow for the easy formation of the active layer on the support and selective permeation of the ceramic membrane, respectively. The average pore sizes of the support, buffer layer, and active layer were 2,677, 773.3, and 33.1 nm, respectively. The diameters of the active layer pores were <0.1 μm. The ceramic membrane performance and mechanical scraping effects on the membrane permeability improvement were evaluated. Mixed liquor suspended solids (MLSS) were used for the feed of an enhanced ceramic membrane filtration system, by combining the fabricated membranes and devised scrapers. The average flux recovery by scraping was 54% of the clean water flux; maintained by scraping despite the high turbidity feed. The permeation concluded within 0.2 h during scrape-off. This was not recovered despite scraping because the internal membrane pores became blocked due to the material turbidity and could not be separated at the surface of the ceramic membrane.

Innovative in situ investigations using synchrotron‐based micro tomography and molecular dynamics simulation for fouling assessment in ceramic membranes for dairy and food industry

AbstractProteins in dairy streams result in organic fouling and function loss for ceramic membrane's porous structure. Synchrotron‐based X‐ray microtomography (SR‐µCT) is a new method with a high signal to noise ratio and accordingly significant level of accuracy. The goal of this study was to perform an in situ assessment of ceramic membrane fouling in the dairy stream filtration process, using SR‐µCT. This study attempted to assess porosity variation and membrane fouling through different layers from the top, middle, and bottom layers of the ceramic microfiltration membrane before and after skimming milk filtration. Molecular dynamics simulation (MDS) was used for depth understanding of milk protein interactions with the ceramic membrane. Fouling was found to be more intense on the top of the ceramic membrane even though the top layer was slightly more porous, which indicates that top layers were more prone to fouling. A regression model was derived to correlate the porosity loss due to membrane fouling at different membrane thicknesses. The MDS results showed more affinity of the milk proteins to the ceramic membrane compared to water molecules. The MDS studies showed how the presence of the milk's protein macromolecules could change the hydrophilicity trend on the membrane's surface.

Catalytically active membranes for decomposition of organic compounds in aqueous solutions

This work is devoted to the preparation of microfiltration ceramic tubular membranes based on α-Al2O3 with deposited catalytically active layers for use in wastewater treatment processes. Cobalt and manganese oxides were used as the material of the catalytically active layer; deposition was carried out using a mixture of aggregative stable aqueous dispersions of Co3O4 and MnO2 nanoparticles. According to the data of scanning electron microscopy, the thickness of the obtained deposited layers does not exceed 3 μm. X-ray fluorescence analysis confirmed the presence of Mn and Co on the surface of the samples. The resulting membranes with a mass of 10 mg of the deposited layer of the oxide mixture were tested in the methylene blue decomposition reaction in dilute aqueous solutions (1,2 mg/L). The reaction was carried out in a batch reactor at room temperature, complete discoloration of the solution was observed after 180-240 minutes.

Efficiency of removal of whey protein from sweet whey using polymeric microfiltration membranes

Our objective was to measure whey protein removal percentage from separated sweet whey using spiral-wound (SW) polymeric microfiltration (MF) membranes using a 3-stage, 3× process at 50°C and to compare the performance of polymeric membranes with ceramic membranes. Pasteurized, separated Cheddar cheese whey (1,080 kg) was microfiltered using a polymeric 0.3-μm polyvinylidene (PVDF) fluoride SW membrane and a 3×, 3-stage MF process. Cheese making and whey processing were replicated 3 times. There was no detectable level of lactoferrin and no intact α- or β-casein detected in the MF permeate from the 0.3-μm SW PVDF membranes used in this study. We found BSA and IgG in both the retentate and permeate. The β-lactoglobulin (β-LG) and α-lactalbumin (α-LA) partitioned between retentate and permeate, but β-LG passage through the membrane was retarded more than α-LA because the ratio of β-LG to α-LA was higher in the MF retentate than either in the sweet whey feed or the MF permeate. About 69% of the crude protein present in the pasteurized separated sweet whey was removed using a 3×, 3-stage, 0.3-μm SW PVDF MF process at 50°C compared with 0.1-μm ceramic graded permeability MF that removed about 85% of crude protein from sweet whey. The polymeric SW membranes used in this study achieve approximately 20%lower yield of whey protein isolate (WPI) and a 50% higher yield of whey protein phospholipid concentrate (WPPC) under the same MF processing conditions as ceramic MF membranes used in the comparison study. Total gross revenue from the sale of WPI plus WPPC produced with polymeric versus ceramic membranes is influenced by both the absolute market price for each product and the ratio of market price of these 2 products. The combination of the market price of WPPC versus WPI and the influence of difference in yield of WPPC and WPI produced with polymeric versus ceramic membranes yielded a price ratio of WPPC versus WPI of 0.556 as the cross over point that determined which membrane type achieves higher total gross revenue return from production of these 2 products from separated sweet whey. A complete economic engineering study comparison of the WPI and WPPC manufacturing costs for polymeric versus ceramic MF membranes is needed to determine the effect of membrane material selection on long-term processing costs, which will affect net revenue and profit when the same quantity of sweet whey is processed under various market price conditions.

Determination of the efficiency of removal of whey protein from sweet whey with ceramic microfiltration membranes

Our research objective was to measure percent removal of whey protein from separated sweet whey using 0.1-µm uniform transmembrane pressure ceramic microfiltration (MF) membranes in a sequential batch 3-stage, 3× process at 50°C. Cheddar cheese whey was centrifugally separated to remove fat at 72°C and pasteurized (72°C for 15 s), cooled to 4°C, and held overnight. Separated whey (375 kg) was heated to 50°C with a plate heat exchanger and microfiltered using a pilot-scale ceramic 0.1-µm uniform transmembrane pressure MF system in bleed-and-feed mode at 50°C in a sequential batch 3-stage (2 diafiltration stages) process to produce a 3× MF retentate and MF permeate. Feed, retentate, and permeate samples were analyzed for total nitrogen, noncasein nitrogen, and nonprotein nitrogen using the Kjeldahl method. Sodium dodecyl sulfate-PAGE analysis was also performed on the whey feeds, retentates, and permeates from each stage. A flux of 54 kg/m2 per hour was achieved with 0.1-µm ceramic uniform transmembrane pressure microfiltration membranes at 50°C. About 85% of the total nitrogen in the whey feed passed though the membrane into the permeate. No passage of lactoferrin from the sweet whey feed of the MF into the MF permeate was detected. There was some passage of IgG, bovine serum albumen, glycomacropeptide, and casein proteolysis products into the permeate. β-Lactoglobulin was in higher concentration in the retentate than the permeate, indicating that it was partially blocked from passage through the ceramic MF membrane.

A novel ceramic microfiltration membrane fabricated by anthurium andraeanum-like attapulgite nanofibers for high-efficiency oil-in-water emulsions separation

Anthurium andraeanum-like Fe3O4-attapulgite (FATP) fibers were prepared by anchoring nano-Fe3O4 particles on the surface of attapugite (ATP) via chemical coprecipitation. Then a novel ceramic microfiltration membrane with superhydrophilic and underwater superoleophobic performance was fabricated based on the FATP fibers. Ascribed to the hydrophilic performance of Fe3O4 and micro-nano structure of FATP fibers, the underwater oil contact angles of the FATP membrance for various types of oils are larger than 158° and the membrane also possesses rather low adhesion force with oil droplets. After 3 cycles of oil-in-water (O/W) emulsion separation, the steady flux of FATP membrane is 209 L m−2 h−1, 44% higher than that of ATP membrane. Moreover, the FATP membrane is stable and easy to clean, its oil rejection maintains at 98.7% and flux can recover by 86.5% using hot water as cleaning agent. The as-developed anthurium andraeanum-like structure in membrane surface provides promising guidance to improve the O/W purification performance of membrane.

Comparative Assessment of Tubular Ceramic, Spiral Wound, and Hollow Fiber Membrane Microfiltration Module Systems for Milk Protein Fractionation.

The fractionation efficiency of hollow fiber membranes (HFM) for milk protein fractionation was compared to ceramic tubular membranes (CTM) and spiral wound membranes (SWM). HFM combine the features of high membrane packing density of SWM and the more defined flow conditions and better control of membrane fouling in the open flow channel cross-sections of CTM. The aim was to comparatively analyze the effect of variations in local pressure and flow conditions while using single industrially sized standard modules with similar dimensions and module footprints (module diameter and length). The comparative assessment with varied transmembrane pressure was first applied for a constant feed volume flow rate of 20 m3 h−1 and, secondly, with the same axial pressure drop along the modules of 1.3 bar m−1, similar to commonly applied crossflow velocity and wall shear stress conditions at the industrial level. Flux, transmission factor of proteins (whey proteins and serum caseins), and specific protein mass flow per area membrane and per volume of module installed were determined as the evaluation criteria. The casein-to-whey protein ratios were calculated as a measure for protein fractionation effect. Results obtained show that HFM, which so far are under-represented as standard module types in industrial dairy applications, appear to be a competitive alternative to SWM and CTM for milk protein fractionation.

Anti-fouling effect by internal air injection in plate-type ceramic membrane fabricated for the treatment of agro-industrial wastewater

The ceramic microfiltration membrane which composed of membrane body having macro pore and active layer having micro pore was fabricated successfully by the process including the sintering of tape-casted and laminated mixture of zirconia and polyvinyl butyral binder, and re-sintering after screen coating of zirconia. The average pore size and porosity of the fabricated membrane were 0.1855 μm and 40 %, respectively. A novel membrane microfiltration system adopting the fabricated ceramic membrane was also devised for the treatment of agro-industrial wastewater, and the effects of external air sparging and internal air injection were investigated. A significant improvement of permeability by external air sparging was not observed, and the permeate flux was about 20 L/m2/h. Despite the abnormal biomass status resulted from low water temperature and poor maintenance of facility, however, the system operated at the initial TMP of 0.4 bar and internal air injection intervals of 5 min showed excellent permeability of 100 L/m2/h. In addition, although several periodic internal air injections with inverse pressure was carried out, structural defects of fabricated ceramic membrane were not observed. Thus, it confirmed that the anti-fouling effect by optimum back-flushing strategy in fabricated ceramic membrane was effective for stability enhancement of agro-industrial complex wastewater treatment process suffering from maintenance.

Determination of the Optimal Conditions for the Purification of Water from Iron and Manganese by Microfiltration Ceramic Membranes, Based on Theoretical Calculations

Determination of the Optimal Conditions for the Purification of Water from Iron and Manganese by Microfiltration Ceramic Membranes, Based on Theoretical Calculations

Preparation of microfiltration ceramic membranes

The main factors affecting the physicochemical properties of microfiltration ceramic membranes based on natural quartz sand were studied. It was found that samples of large-porous ceramics with a content of 11.0 wt. % of the aluminosilicate binder and 10.0 wt. % of the burning additive are characterized by average pore size of 22±3.02 µm, water capacity of 54±5.0 m3/(h×m2×bar), and tensile strength of 9.0±0.6 bar. The optimal conditions for membrane layers coating were determined, which allowed obtaining microfiltration ceramic membranes with average pore size of 2.3±0.2 µm, water capacity of 26±1.0 m3/(h×m2×bar) and tensile strength of 6.5±0.3 bar.

Changing the conventional clarification method in metal sulfide precipitation by a membrane-based filtration process

The metal sulfide precipitation process is a widely studied technology used to recover metals or remove pollutants from different aqueous sources. However, the conventional clarification stage used to separate the generated precipitates cannot effectively remove them from recovered solutions. Taking this into account, the current study focuses on developing a new separation method applied in metal sulfide precipitates, based on a membrane filtration process. Different operating conditions and metal concentration in the feed solution were evaluated for the separation of copper sulfide precipitates formed from synthetic cyanide solutions in ceramic microfiltration membranes. Results showed attractive values of flux and copper recovery. Flux results ranged between 0.9 L/m2s and 1.2 L/m2s for copper concentrations above 500 mg/L, and copper recoveries resulted closer to 100% at the determined optimal operating conditions (4.5 pH, 120% NaHS stoichiometric dosage, and 2 bar feed pressure). These flux values decreased up to one order of magnitude for diluted copper concentrations, due to a change of aggregation capacity of precipitates. This study has demonstrated that the membrane filtration process can be a suitable alternative for the conventional gravitational clarification, promoting better performance results in terms of equipment capacity, metal recovery, and process safety.

Comparison of Polypropylene and Ceramic Microfiltration Membranes Applied for Separation of 1,3-PD Fermentation Broths and Saccharomyces cerevisiae Yeast Suspensions.

In recent years, microfiltration (MF) has gained great interest as an excellent technique for clarification of biological suspensions. This paper addresses a direct comparison of efficiency, performance and susceptibility to cleaning of the ceramic and polymeric MF membranes applied for purification of 1,3-propanediol (1,3-PD) fermentation broths and suspensions of yeast Saccharomyces cerevisiae. For this purpose, ceramic, titanium dioxide (TiO2) based membranes and polypropylene (PP) membranes were used. It has been found that both TiO2 and PP membranes provide sterile permeate during filtration of 1,3-PD broths. However, the ceramic membrane, due to the smaller pore diameter, allowed obtaining a better quality permeate. All the membranes used were highly susceptible to fouling with the components of the clarified broths and yeast suspensions. The significant impact of the feed flow velocity and fermentation broth composition on the relative permeate flux has been demonstrated. Suitable cleaning agents with selected concentration and duration of action effectively cleaned the ceramic membrane. In turn, the use of aggressive cleaning solutions led to degradation of the PP membranes matrix. Findings of this study add to a growing body of literature on the use of ceramic and polypropylene MF membranes for the clarification of biological suspensions.

Harvesting of Microalgae Biomass Using Ceramic Microfiltration at High Cross-Flow Velocity.

This study aimed to investigate the harvesting of microalgae by microfiltration (MF) on a ceramic membrane at relatively high cross-flow velocity (CFV) of interest for commercial processes. Pilot-scale harvesting was conducted with algal suspensions (Chlorella vulgaris and Tisochrysis lutea (T-Iso)) and algal supernatants (Porphyridium cruentum) to assess the effect of feedstock characteristics and understand flux decline mechanisms. In total recycle mode (C. vulgaris, 1g/L), high steady-state permeation flux around 200L/m2/h was achieved. Total filtration resistance was mainly due to cake resistance (Rc, 57%) and pore adsorption and blocking (Ra, 40%). The process hydrodynamic conditions seemed to have relatively little effect on Chlorella cell integrity. In concentration mode, average permeate flux decreased from 441 to 73L/m2/h with increasing feed concentration (C. vulgaris, 0.25-1g/L); the contribution of Rc decreased (82 to 57%), while that of Ra rose (7 to 40%). With T-Iso suspensions and P. cruentum supernatants at 1g/L, average permeate flux was 59 and 49L/m2/h, respectively, with predominance of Rc and Ra, respectively. Distinct fouling mechanisms were inferred to explain the superior filterability of C. vulgaris. The results show that ceramic membrane MF at relatively high CFV could be a suitable option for harvesting certain microalgae including C. vulgaris.

Fabrication of a Cost Effective Ceramic Microfiltration Membrane by Utilizing Local Kashmir Clay

ABSTRACT In this work, we have reported the preparation of a flat circular ceramic membrane (53 mm diameter and 5 mm thick) by paste casting method from locally available Kashmir clay. The membrane was obtained by sintering the clay disc at 850oC for 5 h. The raw material and the membrane were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), porosity, and pure water permeability. The XRF and XRD analysis of the clay confirmed the presence of components required for ceramic membrane preparation. Average pore size, apparent porosity, and pure water permeability of the membrane was obtained as 5.88 µm, 24.30%, and 0.9865 l.m–2.h–1.kPa–1, respectively. Chemical stability was carried out by keeping the membrane in HCl (pH=1) and NaOH (pH=14) solutions for one week. The prepared membrane showed excellent chemical resistance in both the media. The overall fabrication cost of the membrane was estimated as 301 $/m2. These results indicate that the clay used in this work could serve as an alternative raw material to kaolin based ceramic microfiltration membranes for cheaper use in different chemical and biochemical processes.

Purification of Alkaline Solutions from Dyes by Microfiltration Ceramic Membranes Made of Clay Minerals Modified by Montmorillonite

We determined the physicochemical regularities of the process of purification of an alkaline solution of a cationic dye (Methylene Blue) and anionic dyes (Direct Brown and Direct Red) using a microfiltration ceramic membrane based on clay minerals, which is dynamically modified with montmorillonite. This membrane retained 99.6% of Methylene Blue at specific productivity of 0.08 m3/(m2 h) at an initial concentration of the dye of 50 mg/dm3, pH0 12.5, P 1.0 MPa, and a permeate selection factor of 80%. The high retention capacity of the ceramic membrane to Methylene Blue is due to the presence of a modifying layer of montmorillonite on its surface, ensuring the adsorption of dyes in the form of an additional retention gel-like layer of dye associates. The modified microfiltration ceramic membranes made of clay minerals, developed at the Dumansky Institute of Colloidal Chemistry and Water Chemistry, National Academy of Sciences of Ukraine, are comparable to modified microfiltration membranes of oxide ceramics from Rauschert (Germany) in the efficiency of water purification from cationic dyes but are much more productive and cheaper than the latter. Under similar conditions, the modified membrane of clay minerals also showed a high retention capacity to Direct Brown and Direct Red anionic dyes. The mechanism of their retention is associated with the electrostatic repulsion of like-charged anions of dyes and montmorillonite particles. A clay-based ceramic membrane modified with montmorillonite is proposed for the pretreatment of alkaline washing solutions of banknote factories.

Low-cost ceramic microfiltration membranes made from Moroccan clay for domestic wastewater and Congo Red dye treatment

Low-cost ceramic microfiltration membranes made from Moroccan clay for domestic wastewater and Congo Red dye treatment

Preparation and characterization of ceramic membrane using waste almond shells as pore forming agent

In this work, a kaolin based ceramic microfiltration membrane prepared by uniaxial compaction method using locally available waste almond shells as a natural pore-forming agent is reported. The powder (60ASTM Mesh) prepared from waste almond shells was added to the raw mix as a pore-forming agent. The disc prepared from the raw mix at 150 MPa was sintered at 850℃ for 4 h to obtain the membrane. The raw material and the membrane were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy and field emission scanning electron microscopy (FE-SEM). The pore diameter and porosity of the membrane were obtained as 0.290 μm and 46.45% with good chemical stability. The fabrication cost of the membrane based on the cost of raw material was estimated to be Rs. 2083.33/m2. These results show that the almond shells can be utilized as an economical and green material in the fabrication of low-cost ceramic membranes.