Tubular Ceramic Membrane Research Articles

Effective separation of water-DMSO through solvent resistant membrane distillation (SR-MD)

The treatment of organic waste or wastewater with high organic solvent content has been challenging in industries as it cannot be done effectively using conventional wastewater treatment technologies such as biodegradation and advanced oxidation process. Solvent resistant membrane distillation (SR-MD) was proposed as an energy-efficient alternative to treat these waste streams but its application is hampered by the lack of solvent-resistant membranes, and there is a research gap in studying the feeds with water-solvent mixtures. In this work, ceramic tubular membranes with different pore sizes and structures were molecularly grafted with 1H,1H,2H,2H-perfluorodecyltriethoxysilane to obtain hydrophobic ceramic membranes for SR-MD. The modified membranes exhibited excellent hydrophobicity and solvent resistant properties, and they were tested for SR-MD performance with a wide range of dimethyl sulfoxide (DMSO) feed concentrations, from 3.5 to 85 wt%. The membranes exhibited a high DMSO rejection of >98% and the separation factor of >170, with permeation flux >4.4 kg m−2 h−1 when the DMSO concentration in feed was below 65 wt%. The separation performance was found strongly dependent on the evaporation step and the vapour-liquid equilibrium near the interface. The DMSO rejection was also comparable to pervaporation while the permeation flux was much higher at the feed concentration of 50 wt%. This study establishes the strategy of using SR-MD as a promising membrane process in treating complex industrial wastes with high organic solvent content.

Modeling of fouling mechanisms in the biodiesel purification using ceramic membranes

Since membrane fouling is well acknowledged to be one of the key impediments to more widespread implementation of membrane-filtration processes, this study aimed to assess the fouling mechanisms in the biodiesel separation and purification process using ceramic membranes. The analysis of fouling mechanisms was performed using a model proposed in the literature applied to cross-flow filtration and constant pressure. The experiments were carried out with tubular ceramic membranes with average pore size of 0.2 µm, 0.1 µm, 0.05 µm, and 20 kDa at 1.0, 2.0, and 3.0 bar transmembrane pressures. After transesterification, the reaction mixture was directly processed, eliminating the conventional previous decantation step. It was evaluated the influence of acidified water addition (10, 20 and 30 wt%) on the glycerol retention efficiency and the fouling mechanism. The results obtained demonstrated that the amount of water added influences the formation of the phases and, consequently, the separation performance. The permeate flux profile over time made it possible to determine the predominant fouling mechanism in each evaluated condition. Thus, the predominant fouling mechanisms were complete pore blocking, cake filtration and internal pore blocking when using 10, 20 and 30% water concentration, respectively. It was possible to conclude that the fouling mechanism dominant in each experimental condition is dependent upon the size of aqueous phase droplets and the membrane pore diameter. The results demonstrated that it would be possible to predict the efficiency of glycerol separation by identifying the fouling mechanism, so that the condition of complete pore blocking is the most recommended in this biodiesel purification process, since it indicates a greater retention of glycerol by the membrane, and the stabilization of fluxes at higher rates.

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.

Biodiesel wastewater treatment using nanofiltration membranes

Water reclamation and reuse are economically and environmentally important issues for industries. Costly and ineffective treatments such as coagulation, flocculation, and/or biological treatment are the most widely used technologies for these processes. The aim of this paper is to study membrane separation to treat biodiesel wastewater as an alternative. To achieve this goal, two commercial nanofiltration membranes were used to treat medium-high strength wastewater. An Inopor Nano tubular ceramic membrane was used in a cross-flow module and a NF99HF Alfa Laval polymeric flat sheet membrane was used in a dead-end filtration cell. Wastewaters were prepared and treated with these membranes achieving maximum fluxes of permeate of 53.1 L h-1 m-2 for the ceramic membrane and 12.2 L h-1 m-2 for the polymeric membrane at 20 bar and 30 °C. The results shows a chemical oxygen demand retention between 80–85 % were obtained for both membranes, while the retention of ionic species due to changes in electrical conductivity was 76–89 %. Transmembrane pressure, organic load, hydraulic permeability, cross-flow velocity, wastewater characterization and fouling resistance-in-series analysis were also made and analyzed in detail in order to explore the actual use of nanofiltration.

New Insights into the Microbial Diversity of Cake Layer in Yttria Composite Ceramic Tubular Membrane in an Anaerobic Membrane Bioreactor (AnMBR).

Cake layer formation is an inevitable challenge in membrane bioreactor (MBR) operation. The investigations on the cake layer microbial community are essential to control biofouling. This work studied the bacterial and archaeal communities in the cake layer, the anaerobic sludge, and the membrane cleaning solutions of anaerobic membrane bioreactor (AnMBR) with yttria-based ceramic tubular membrane by polymerase chain reaction (PCR) amplification of 16S rRNA genes. The cake layer resistance was 69% of the total membrane resistance. Proteins and soluble microbial by-products (SMPs) were the dominant foulants in the cake layer. The pioneering archaeal and bacteria in the cake layer were mostly similar to those in the anaerobic bulk sludge. The dominant biofouling bacteria were Proteobacteria, Bacteroidetes, Firmicutes, and Chloroflexi and the dominant archaeal were Methanosaetacea and Methanobacteriacea at family level. This finding may help to develop antifouling membranes for AnMBR treating domestic wastewater.

Modulation of carotenoid/flavonoid profiles and sugar content of a potential functional citrus-based food through crossflow microfiltration

Crossflow microfiltration was implemented to enrich a clementine/pink grapefruit juice in carotenoids, flavonoids and pectins modulating its sugar content thanks to an added diafiltration step. Using tubular ceramic membrane with pore diameter of 0.2 μm at 30–40 °C, a crossflow velocity of 5 m‧s−1 and a transmembrane pressure of 2.6 bar, the impact of the process was assessed focusing on bioactive compounds and physical characteristics of the concentrates. With permeate flux above 30 kg‧h−1‧m−2, the process resulted in an increase of 8–10 times in the content of provitamin A carotenoids (33 mg‧kg−1 in the final products), lycopene (43 mg‧kg−1), hesperidin (3.2 g‧kg−1) and pectin (5.5 g‧kg−1) giving a unique and interesting composition profile. Moreover, diafiltration divided the sugar content by 3. This can be relevant for the product to be recommended as part of a reduced sugar diet for diabetic people. By modelling the retention of bioactive compounds, we showed that it was possible to modulate sugar, flavonoids, carotenoids and pectin contents in the concentrate that could be a key issue for the biological activity of this potential functional citrus-based food.

Assembly of multidimensional MXene-carbon nanotube ultrathin membranes with an enhanced anti-swelling property for water purification

Severe stacking and swelling properties are critical issues in two-dimensional (2D) lamellar membrane fabrication and separation processes that can result in low flux and poor rejection. Herein, we propose the assembly of multidimensional MXene-carbon nanotube (CNT) ultrathin membranes by loading a MXene intercalated with CNTs onto a tubular ceramic membrane. Benefiting from the modes of van der Waals interactions (hydrogen bond) and repulsion forces between the MXene and functionalized CNTs, the one-dimensional (1D) CNTs are well dispersed and intercalated into the 2D MXene nanosheets, forming a uniform network and continuous three-dimensional (3D) labyrinthine short mass transfer channels, which can considerably improve the permeability and rejection performance of the membranes. Furthermore, the membranes exhibit a distinct suppressed swelling property via a facile thermal crosslinking process (-OH + -OH = -O- + H2O and -COOH + -OH = -COO + H2O), accompanied by the formation of new chemical bonds (Ti-O-C and Ti-COO-C) due to dehydroxylation between the neighboring MXene nanosheets and CNTs. Additionally, 50 h long-term operation studies also indicate the promising anti-swelling property and stability of the MXene-CNT membranes. This multidimensional (1D and 2D) assembly and thermal crosslinking strategy represents a new avenue for the facile and scalable development of MXene-based and other 2D material-derived high-performance membranes for water purification.

Tube-in-tube membrane photoreactor as a new technology to boost sulfate radical advanced oxidation processes

This work proposes a tube-in-tube membrane photoreactor, operated in a continuous-mode, to boost the efficiency of peroxydisulfate (PDS), through the photolytic (UV-C radiation) and photocatalytic (TiO2-P25) processes. This new technology can efficiently facilitate the transportation of PDS to the catalyst surface and water to be treated. The ultrafiltration tubular ceramic membrane was used as support for the TiO2-P25 and oxidant-catalyst/water contactor. Tests were performed using a synthetic solution and a municipal secondary effluent, both spiked with a pharmaceutical mix solution (paracetamol (PCT), furosemide (FRS), nimesulide (NMD), and diazepam (DZP); 200 μg L−1 of each). At steady-state regime, the UVC/S2O82−/TiO2 system, with radial PDS addition, showed the highest removal of pharmaceuticals in both matrices. Furthermore, twenty-two transformation products (TPs) were identified by applying LC-QTOF MS technique. Hence, the transformation pathways including hydroxylation in aromatic moiety by an electrophilic attack, electron transfer reactions, cleavage of C−O, C−N bond, H−abstraction and ring opening were proposed. TPs chemical structures were evaluated by in silico (Q)SAR approach using TOXTREE and EPI Suite™ software.

Preparation and Application in Crude Oil-Water Separation of Clay-Based Membranes

In this study, tubular ceramic membranes were prepared from a mixture of ball clay, talc and alumina. The mixture was characterized by the following techniques: particle size analysis, X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD) and thermal analysis. Tubular membranes were produced by extrusion process and thermal treated at temperatures between 1025 °C and 1175 °C. The membranes were characterized by XRD, linear shrinkage, apparent porosity, flexural strength, mercury porosimetry, scanning electron microscope (SEM) and contact angle. To evaluate the efficiency of the membranes, permeability tests with distilled water and oil-in-water emulsion were conducted in a tangential flow system. The results showed that the sintering of the specimens promoted the formation of α-cordierite phase and directly influenced the physical and mechanical properties such as linear shrinkage, porosity and flexural strength. Separation tests revealed that these membranes promoted high oil-water separation efficiency with values above 99.0%.

In situ growth of a tubular MoS2 membrane on a ceramic tube with improved organic solvent nanofiltration performance

A MoS2 tubular ceramic membrane was prepared successfully via a straightforward in situ hydrothermal method and demonstrated excellent organic solvent nanofiltration properties and high stability.

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.

A New Design of Tubular Ceramic Membrane Module for Oily Water Treatment: Multiphase Flow Behavior and Performance Evaluation.

Petroleum has been extracted from oil reservoirs using different techniques. This activity is accompanied for a large amount of water and sometimes mixed with gas. This produced water has a high oil concentration and other toxic chemical compounds, thus, it must be treated to be reused or released to environment according to environmental protection regulations. Currently, ceramic membrane technology has been employed in the wastewater treatment, due to its high benefit–cost ratio. In this sense, this work aims to study the oil–water mixture separation process using a new configuration of tubular ceramic membrane module by computational fluid dynamic (ANSYS Fluent software). The proposed model is composed of mass and linear momentum conservation equations coupled to Darcy’s law and SST k-ω turbulence model. Results of the volumetric fraction, pressure, and velocity distribution of the oil and water phases are presented and discussed. The results indicated that the proposed model and new device both have great potential to be used on the water/oil separation process and that the transmembrane pressure remains constant in the axial direction and decreases radially through the membranes, indicating an efficient system that favors the transport of clean water and oil retention.

The use of whey in products for school nutrition

The article provides an assessment of the prospects of using whey protein for school nutrition. Whey protein has unique characteristics and, unlike vegetable protein, is a complete protein with a high degree of hydration, which allows it to be used for rapid entry into the body. Since whey proteins are better absorbed than casein, they are used for such purposes as infant formula production and for increasing the nutritional value of dairy and other products. A method for obtaining whey proteins by cross flow ultrafiltration through ceramic tubular membranes is considered. To eliminate the problems of contamination of ceramic tubular membranes, an automated system has been developed that provides for their regeneration in continuous operation of the ultrafiltration unit.

Radiation stability of ceramic tubular membranes containing ammonium molybdophosphate (AMP) for the application of radio-cesium recovery from radioactive wastes

In order to develop radiation resistant membranes for the treatment of high level waste (HLW), ceramic tubular membranes were prepared by incorporating varying amounts of ammonium molybdophosphate (AMP), known for efficient Cs(I) uptake from acidic feeds, for the recovery of radio-caesium. The sorption of Cs(I) onto the membrane increased linearly with increasing the AMP content (10%–40%). Radiation stability of the membranes was evaluated by exposing them to gamma radiation obtained from a 60Co source. The composite ceramic material showed excellent radiation stability without any morphological change up to 1100 kGy, indicating its potential application in radioactive waste treatment. For 10% AMP loaded ceramic membrane, the Cs(I) sorption decreased linearly with radiation dose. However, Cs sorption was not altered up to 1100 kGy dose for 20% and 40% loaded AMP.

Fabrication of Bentonite-Silica Sand/Suspended Waste Palm Leaf Composite Membrane for Water Purification.

In this study, a method for fabricating tubular ceramic membranes via extrusion using economical and locally available bentonite–silica sand and waste palm leaves was developed as a tool for conducting the necessary task of purifying water polluted with oil and suspended solid materials produced via various industrial processes. The developed tubular ceramic membranes were found to be highly efficient at separating the pollutants from water. The properties of the fabricated membrane were evaluated via mechanical testing, pore size distribution analysis, and contact angle measurements. The water contact angle of the fabricated membrane was determined to be 55.5°, which indicates that the membrane surface is hydrophilic, and the average pore size was found to be 66 nm. The membrane was found to demonstrate excellent corrosion resistance under acidic as well as basic conditions, with weight losses of less than 1% in each case. The membrane surface was found to be negatively charged and it could strongly repulse the negatively charged fine bentonite particles and oil droplets suspended in the water, thereby enabling facile purification through backwashing. The obtained ceramic membranes with desirable hydrophilic properties can thus serve as good candidates for use in ultrafiltration processes.

Concentration and purification by crossflow microfiltration with diafiltration of carotenoids from a by-product of cashew apple juice processing

This work aimed to further investigate microfiltration with diafiltration to obtain a rich carotenoid extract from the solid by-product of cashew apple (Anacardium occidentale L.) juice processing. This solid residue called cashew fibers is rich in bioactive compounds, especially carotenoids. After mixing with water and pressing, an aqueous suspension was obtained and processed by crossflow microfiltration (40 °C) using tubular ceramic membrane with 0.2 μm pore diameter. Permeate flux, which increased with transmembrane pressure, could be maintained above 100 L·h−1·m−2 at high volume reduction ratio by coupling mechanical extraction with enzyme liquefaction. The concentration step led to an increase of the carotenoid content by up to 19-fold and the diafiltration step allowed the carotenoid purity to be multiplied by 5. The impact of the process on the retentate characteristics was assessed using a model based on simple assumptions. This calculation tool can easily be implemented and is helpful for choosing the operating conditions, to minimize water consumption as well as effluent production.

Toluene removal from gas streams by an ionic liquid membrane: Experiment and modeling

Ionic liquids (ILs) are promising alternative solvents for traditional organic compounds using selective separation. However, some environmental risks of ILs, resulting in a limitation of their applications in industry. In this work, the stability of ILs into multi-channel tubular ceramic membranes (ILM) provides a promising way to realize the use of ILs with environmental damages reducing. This novel process has been investigated for toluene removal from a toluene/air gas mixture based on 1-butyl-3-imidazolium bis(trifluoromethylsulfonyl)amide ([Bmim][NTf2]) as a liquid sorbent. In addition, the effects of operating conditions on toluene separation were studied and discussed by experiment and modeling. The absorption capacity of toluene by the ILM on proposed operating conditions was around 224.74 mg per gram of the ionic liquid. The support ceramic membrane can effectively prevent ILs leakage from causing secondary waste and ensure longtime operation. Regeneration of polluted ILM was available.

Recovery of lignin from water and methanol using low-cost kaolin based tubular ceramic membrane

This study investigated the performance of low-cost tubular ceramic membranes fabricated using kaolin, quartz and calcium carbonate as inexpensive raw materials following the extrusion method for lignin recovery from water and methanol. The effect of different concentrations of carboxymethyl cellulose (CMC) as a binder along with the raw materials on the membrane properties such as porosity, pure water permeability, flexural strength and chemical stability was first studied. The increase in CMC concentration resulted in enhancement of chemical stability, flexural strength and pure water permeability alongside a decrease in porosity of the membrane. Based on the characterization results, membrane prepared using 3 wt% CMC was found suitable for microfiltration applications, which showed porosity of 36 %, flexural strength of 38 MPa and average pore size of 0.18 μm. The prepared membrane was further tested for the recovery of lignin - a key value-added component in biorefinery operation - from water and methanol. Cross-flow microfiltration experiments performed using the membrane at five different applied pressures (34−172 kPa) showed maximum lignin rejection values of 82.5 % and 80 % with lignin-water and lignin-methanol solutions, respectively, at an applied pressure of 34 kPa.

Performance Evaluation of Tubular Ceramic Membrane for Palm Oil Mill Effluent Treatment

Palm oil industry is one of the most important agriculture sectors in Malaysia. However, this industry produces a huge amount of palm oil mill effluent (POME) which contains impurities that will pollute the environment. Hence, POME has to be treated before it can be safely discharged to the environment. This study aims to evaluate the effectiveness of tubular ceramic membranes with different pore sizes (0.2 μm, 450 Da, and 200 Da) for the removal of turbidity and chemical oxygen demand (COD) in POME. It was found that all of the ceramic membranes were capable to achieve more than 99% of turbidity removal through size exclusion mechanism since the particles were larger in size as compared to membrane pores. On the other hand, the reduction of COD was ineffective since the dissolved organic substances in POME could penetrate the membrane and thus resulted in low removal efficiency. Flux decline was recognisable only when treated with the 0.2 μm membrane. It was attributed to its higher initial flux (16 Lm-2h-1) that imposed larger permeation drag and brought more impurities to quickly cover the membrane surface and clog the membrane pores during the initial filtration process. Chemical cleaning was able to recover 77-83% of the flux and this shows that some of the impurities were still persisting in the membrane. The tested membranes were capable to fully remove the suspended solids and could serve as a good pre-treatment process for subsequent COD reduction treatment process.

Fractionation of hydrolysates from concentrated lecithin free egg yolk protein dispersions by ultrafiltration

A membrane process for the recovery of ≥ 90 % of the soluble peptides (with antioxidant activity) found in concentrated lecithin-free egg yolk hydrolysates (LFEYH) was established. Hydrolysis of concentrated free lecithin egg yolk protein dispersions (10 and 20 %) was conducted with Alcalase 2.4L, an endoprotease from Bacillus Licheniformis. The obtained hydrolysates were fractionated by ultrafiltration (UF), where the effect of the membrane material and molecular weight cut-off (MWCO) was studied. Two flat sheet regenerated cellulose membranes and three tubular ceramic membranes with different MWCOs (50, 10 and 5kDa) were tested. Different hydrodynamic operating conditions were established in all membranes to work under sustainable flux during UF. The 50kDa ceramic membrane was found to be the most efficient in terms of flux (78.45 and 47.84kgm−2h-1 for 10 and 20 % protein dispersions, respectively) and showed lower fouling. The use of diafiltration (DF), allowed recovering more than 90 % of soluble and heat-stable peptides, which also showed high antioxidant activity, from hydrolysates produced in both concentrated (10 and 20 %) egg yolk protein dispersions.