Ceramic Microfiltration Membranes Research Articles

Low-cost ceramic membrane made from alumina- and silica-rich water treatment sludge and its application to wastewater filtration

Drinking water treatment sludge (DWTS) was used for the preparation of ceramic microfiltration membrane. The DWTS powder was firstly characterized to determine its chemical and mineralogical composition, and to understand its thermal behavior. DWTS powder was mixed with clay as binder and starch as porosity agent, then pressed to shape flat membrane, and sintered at different temperatures from 950 to 1150 °C. The optimal sintering temperature (1050 °C) provides ceramic membrane with a porosity of 46.7%, a pore size of 0.92 μm, a mechanical strength of 14.5 MPa and a permeability of 724.5 L/h.m2.bar. This membrane was successfully used to clarify a synthetic baking powder suspension and an textile effluent. DWTS-based membrane was able to remove completely the turbidity from feeds, to reduce significantly the chemical oxygen demand (COD), and to discolor completely textile wastewater. Furthermore, four empirical models were applied to describe the fouling mechanism occurred during filtration experiments.

Synthesis, characterization and performance studies of kaolin-fly ash-based membranes for microfiltration of oily waste water

The present study deals with the synthesis, characterization, and performance evaluation of low-cost porous ceramic microfiltration membranes for separation of oily waste water. Ceramic membranes were synthesized following paste-casting method using three different ratios of kaolin to coal fly ash, in combination with a few selected suitable pore - formers and binders like calcium and sodium carbonate, boric acid, and sodium metasilicate. The synthesized membranes were characterized using the field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and water permeation tests with the objective of investigating the influence of sintering temperature (750 °C–900 °C) and precursor ratio on the microstructural evolution of the fabricated membranes. Three varying concentrations of oil-in-water (O/W) emulsions (100, 200, and 300 mg/L) prepared using a typical crude oil collected from an oil field located in Digboi, India was used as a representative sample and tested for the microfiltration studies. A fabricated membrane with a porosity (~34.36–39.0%), pore size (~0.65–1.81 μm) showed an excellent separation efficiency of 96.7–99.5% with a permeate flux around ~ 24.3 × 10−5 m3 m−2 s−1. The flux decline mechanism was analyzed using the pore blocking models, and it was observed that the cake filtration model followed by the intermediate pore-blocking model were the best - fitted models as compared to others to describe the permeate flux data. The fabricated kaolin-fly ash-based membranes exhibited good permeability and separation efficiency characteristics, which suggest its suitability for microfiltration of oily waste water from oil exploration and refinery industries.

Fabrication and Characterization of Ice Templated Membrane Supports from Portland Cement.

Porous ceramic membranes for aqueous microfiltration and ultrafiltration processes suffer from the high-costs of material and processing. The latter is mainly due to the high-temperature sintering step. In this work, cement-based membrane supports from ultrafine Portland cement are studied as a low-cost alternative to traditional oxidic ceramic supports. An environmentally friendly freeze-casting fabrication route is applied for the fabrication of porous membrane supports. Cement membrane supports are becoming mechanically stabile after hydration reaction of cement with water, which does not require any high-temperature sintering step as in a conventional ceramic membrane fabrication process. This fabrication route, which is sintering-free, decreases the cost and environmental impact of the membrane fabrication process by eliminating extra energy consumption step during sintering. The Archimedes method, scanning electron microscopy (SEM), micro-computed tomographic (µCT), and mercury porosimetry characterize the membrane supports in respect to open porosity, pore size distribution, morphology, and connectivity. The flexural strength of the 3 mm thick membranes is in the range from 1 to 6 MPa, as obtained by the ring-on-ring tests. The obtained membrane supports possess porosity in the range between 48 and 73% depending on fabrication conditions (cooling rate and the solid content, as determined by Archimedes method enabling water flux in the range between 79 and 180 L/(h·m2) at 0.5 bar transmembrane pressure difference and 3 mm membrane thickness.

Synthesis and Characterization of Microfiltration Ceramic Membrane Based on Fly Ash and Clay Mixture Using Sintering Method

Ceramic membranes made from low-cost materials have increasingly been developed. Fly ash is a waste from cement industries, while clay is a natural resource that can be easily found to be used as economical mixed materials in the production of ceramic membrane. The manufacture of microfiltration ceramic membrane from fly ash - clay mixture has been carried out using the sintering method for 4 hours at low sintering temperatures variations at 750 °C (M1), 800 °C (M2), 850 °C (M3) and 900 °C (M4), respectively. The results showed that the ceramic membrane that was sintered at a temperature of 900 °C (M4) had the optimum characteristics with a porosity of 40.82%, a density of 1.0026 gr/cm3. From scanning elctron microscopy (SEM) analysis showed that the M4 membrane was classified as a microfiltration membrane with an average pore size of 0.64 μm. The energy diepersive x-ray (EDX) analysis showed that the composition of the M4 membrane was dominated by elements O, Si, and Al. Moreover, the x-ray diffraction (XRD) analysis showed that the fraction patterns of the membranes (M1, M2, M3, M4) were dominated by the quartz phase (SiO2) and illite phase ((KH3O)Al2Si3AlO10(OH)2).

Premix membrane emulsification using flat microfiltration inorganic membranes with tailored structure and composition

Uniform oil-in-water emulsions were prepared using MCT (medium-chain fatty acid triglyceride, 10 wt%) as the oily dispersed phase and polysorbate 80 as the surfactant (1 wt%). The emulsification process was performed via premix membrane emulsification (PME) using 3 flat microfiltration ceramic membranes with different mean pore sizes (dm): borosilicate (symmetric, commercial, dm: 1.39 μm); SiOC (symmetric, manufactured, dm: 1.76 μm); and mullite (asymmetric, manufactured, dm: 1.18 μm). The droplets size and their distribution varied according to the membrane type and number of permeation cycles (up to a limit of 2 passes). All prepared emulsions presented a tendency to monomodal droplet distribution with span values in the range of 0.82–0.97. The coarse emulsion (premix) droplets were reduced from 6.30 to 4.50–2.17 μm. The asymmetric membrane (mullite) exhibited the highest permeation fluxes at constant relative pressure for both water (43.1 × 10−3 m3 m−2 s−1) and premix (Pass 1: 4.6 × 10−3 m3 m−2 s−1; Pass 2: 5.3 × 10−3 m3 m−2 s−1), still maintaining satisfactory emulsification results.

Cross-Flow Microfiltration of Glycerol Fermentation Broths with Citrobacter freundii.

This paper reports the study of the cross-flow microfiltration (MF) of glycerol fermentation broths with Citrobacter freundii bacteria. A single channel tubular ceramic membrane with a nominal pore size of 0.14 µm was used. It has been demonstrated that the MF ceramic membrane has been successfully applied to bacteria cell removal and to effectively eliminate colloidal particles from glycerol fermentation broths. However, due to fouling, the significant reduction of the MF performance has been demonstrated. In order to investigate the impact of transmembrane pressure (TMP) and feed flow rate (Q) on MF performance, 24 experiments have been performed. The highest steady state permeate flux (138.97 dm3/m2h) was achieved for 0.12 MPa and 1000 dm3/h. Fouling analysis has been studied based on the resistance-in series model. It has been found that the percentage of irreversible fouling resistance during the MF increases with increasing TMP and Q. The permeate flux regeneration has been achieved by membrane cleaning with 3 wt % NaOH and 3 wt % H3PO4 at 45 °C. The results of this study are expected to be useful in industrially employing the MF process as the first step of glycerol fermentation broth purification.

New low-cost ceramic microfiltration membrane made from natural magnesite for industrial wastewater treatment

This paper mainly focuses on the preparation of new low-cost ceramic microfiltration membrane made from natural magnesite. Firstly, local Moroccan magnesite was deeply characterized in order to understand its chemical and mineralogical composition, and its thermal behavior. It was confirmed that used natural magnesite exhibits high purity degree in terms of magnesite mineral. Next, flat magnesite membrane was fabricated via uniaxial pressing and sintering methods. The effect of sintering in the range 900−1200 °C on morphology, porosity, pore size, permeability and mechanical strength was investigated. Based on experimental results, the optimized membrane (sintered at 1100 °C) has a porosity of 48.15 %, a pore size of 1.12 μm, a water permeability of 922 L h−1 m-2 bar-1 and a mechanical strength of 6.1 MPa. Finally, the optimized magnesite membrane was subjected to filtration of industrial textile wastewater in order to evaluation its performance as microfiltration membrane. Importantly, experimental results are clearly demonstrated that magnesite membrane effectively clarifies textile wastewater. It was showed that turbidity and chemical oxygen demand removals could achieve 99.9 and 69.7 %, respectively.

Utilization of LD slag from steel industry for the preparation of MF membrane

This work is focused on utilizing the solid waste generated from steel industry for the fabrication of porous ceramic membrane from Linz Donawitz (LD) slag. Membranes were fabricated using uniaxial method sintered at three different temperatures like 650 °C, 850 °C and 950 °C. Membranes fabricated with raw LD slag gave a highly basic filtrate. In contrast with this issue, LD slag was modified using acetic acid and CO2 purging to convert calcium oxide which is present in the slag to calcium carbonate. The membranes fabricated from modified LD slag showed a filtrate pH of 8.4 and 8.5. Porosity, pore size distribution, flexural strength, chemical stability was determined and pure water flux experiments were conducted to evaluate the efficiency of the prepared membranes. Considering the raw materials cost, the cost of the fabricated membranes was estimated in the range of 32.55–55.7 USD/m2. This work gives a potential path to develop microfiltration ceramic membrane with, high porosity and great quality in terms of strength and chemical stability. The fabricated membranes were utilized in a hybrid technique (flocculation followed by microfiltration) for the treatment of cold roll mill (CRM) wastewater generated from steel industry. Use of LD slag for the fabrication of ceramic membrane is not only an appealing option towards the commercialization of membrane, yet also great option to reduce the solid waste which is dumped to the environment.

Effect of Porogenic Agent Type and Firing Temperatures on Properties of Low-Cost Microfiltration Membranes from Kaolin

ABSTRACTThe present work is focused on the development and characterization of low-cost flat microfiltration ceramic membranes from West Cameroonian kaolin, cassava starch and bovine bone ash as pore-forming agents, and comparative study of porogens’ influence on membranes properties. These materials were chosen due to their abundance in the country and their beneficial properties. The proportion of porogens varied from 0% (CM0) to 20% and all samples were treated at 1000o-1150oC; membranes without porogenic agent (CM0) gave good results. Linear shrinkage and weight loss values were <7% and <30%, respectively. SEM pictures revealed that inter-granular contacts were formed at 1150oC for all the samples and thus materials densification was more important. Porosity varied between 31% and 52% at 1150oC, and flexural strength increased from 1.07 to 7.79 MPa. Samples containing bovine bone ash contributed to the improvement of membrane microstructure, mechanical and corrosion resistance. Filtration tests through CM04 and CM34 gave turbidity rejection factors of 97.70% and 99.26%, respectively. Decisively, good and low-cost microfiltration ceramic membrane can be developed by using cassava starch and bovine bone ash as porogenic agents.

Innovative Eco Biofilter/Membrane Bioreactor (MBR) Technology for Community Wastewater Recycling

Eco Biofilter/Membrane Bioreactor (MBR) has been developed in this research as a compact wastewater treatment for community wastewater recycling. The system installs the baked clay filter as eco-friendly biomedia in order to replace plastic media that can cause plastic pollution to aquatic environment. Ceramic microfiltration membrane (MF) with the pore size of 0.4 micron is submerged inside the Eco Biofilter/Membrane Bioreactor. The system received wastewater from a community area in Chiang Rak Yai, Pathumthani province, that is located in the east of Chaophraya River. The community consists of 350 households, who regularly use water from the Chaophraya River. It is a very urgent issue to develop the appropriate wastewater treatment to protect the river water quality for water supply production. At present, the overall water quality of the Chaophraya River is falling into category 4, which is in poor water quality level. In this research, the developed Eco biofilter/MBR technology can significantly reduce BOD, oil&grease, TSS and FCB. It also could achieve stable treatment performance as above 70% removal efficiencies for Total Phosphorus and Kjeldahl Nitrogen. Moreover, the effluent quality after the treatment meets international standard for agricultural water reuse purpose for food crops, processed food crops and non-food crop.

Preparation of high-permeance ceramic microfiltration membranes using a pore-sealing method.

A pore-sealing method for preparation of high-permeance alumina microfiltration (MF) membranes free of any intermediate layers is presented. It involves sequential coating of a polyvinyl butyral (PVB) layer and an alumina membrane precursor on the surface of the macroporous alumina support. An alumina MF membrane with no intermediate layers can be obtained on the support after pyrolysis of the PVB interlayer. The interlayer-free membrane prepared by this method has an average pore diameter of 0.26 μm and a water permeance of 1468 ± 81 L m−2 h−1 bar−1 which is prominently higher than that of the ceramic membranes prepared with other techniques. The conspicuous increase of water permeance is speculated mainly due to the filtration resistance decrease of the interlayer-free ceramic membrane.

Fabrication of flat ceramic microfiltration membrane from natural kaolinite for seawater pretreatment for desalination and wastewater clarification

The aim of this work is the manufacturing of flat microfiltration membrane made from Moroccan natural kaolinite clay and corn starch as porosity agent. The membrane was prepared by uniaxial pressing technique and sintering at 1,100 degrees C. The effect of starch on membrane features was investigated from 0 to 15 wt.%. The membrane has a diameter of 37.8 mm and a thickness of 2.3 mm. In order to optimize its properties, prepared membrane was characterized in terms of apparent porosity, water absorption, apparent density, mechanical strength, pore size, microstructure, and water permeability measurements. Experimental results showed that the membrane prepared with 10 wt.% of starch is considered as an optimized membrane which has an average pore size of 2.3 mu m, the mechanical strength of 20.2 MPa, and permeability of 2,129 L h(-1)m(-2) bar(-1). The optimized membrane was applied for pretreatment of raw seawater for desalination and clarification of agro-food effluent using dead-end filtration under pressure of 0.12 bar. Filtration results showed that turbidity rejection achieves 73% and 99%, respectively for raw seawater and agro-food model effluent.

Preparation and characterization of ceramic microfiltration membranes for removal of Cr (VI) and Pb from electroplating effluent

Present work deals the removal of Cr (VI) and Pb from electroplating effluent (EPE) using ceramic membrane MD-1 (ceramic membrane without coating) and MD-2 (ceramic membrane with chitosan coating). Uniaxial compaction followed by sintering process has been applied to prepare the membrane from locally available clay. Results indicate that maximum removal of 65% Cr (VI) and 68% Pb has been achieved by use of MD-1 membrane, while, MD-2 removed 81% Cr (VI) and 93% Pb, from the initial feed concentration of 55.3 mg/dm3 Cr(VI) and 3.5 mg/dm3 Pb at optimum operating condition pH 3.5 and applied pressure 300 kPa.

Development of highly porous mullite whisker ceramic membranes for oil-in-water separation and resource utilization of coal gangue

To realize the recycling of coal gangue and obtain high value-added products, highly porous mullite whisker ceramic microfiltration membranes for the treatment of emulsified oily wastewater were prepared using Al(OH)3 and coal gangue as primary materials and MoO3 as the additive. By a comparative study on the ceramic membranes with and without MoO3 addition, the sintering reaction process, thermal shrinkage behavior, microstructure, open porosity, flexural strength, pore size distribution, and pure water permeate flux of the ceramic membranes were illuminated. The MoO3 addition enhances mullitization reaction and promotes mullite whisker growth. Through changing the sintering temperature so as to control mullitization reaction and mullite whisker growth, the satisfactory porosity and pore size are achieved for the mullite whisker ceramic membrane sintered at 1400 °C. The mullite whisker ceramic microfiltration membrane, possessed a high open porosity of 47.21 ± 0.48%, the average pore size of 185.3 nm and flexural strength of 34 ± 2.5 MPa, shows the highest permeability of 35.8 mL·m−2·s−1 and above 97% oil rejection when operating at 0.1 MPa trans-membrane pressure in oil-in-water separation experiments.

High turbidity water treatment by ceramic microfiltration membrane: Fouling identification and process optimization

Abstract Ceramic membranes have been introduced in various fields; however, research on ceramic membranes in high-turbidity environments has been rarely performed. In this study, the fouling characteristics of a ceramic microfiltration membrane in a high-turbidity environment were examined. First, the factors affecting the ceramic-membrane fouling were investigated through filtration tests in various feed-water conditions. Next, as a pretreatment to the membrane process, three types of coagulant were compared, and the optimum coagulant and coagulation concentration were selected. Finally, the ceramic and polymeric membranes’ treating of high-turbidity water was compared, with and without coagulation. The results indicated that the turbidity was the major influential factor of irreversible fouling on the ceramic membrane. When the turbidity increased, irreversible fouling occurred rapidly, which may be caused by small particulates entering the membrane, and resulting in standard pore blocking. Therefore, the coagulation experiment was conducted using feed water with high turbidity, which causes the most irreversible fouling. As a result, poly-aluminum chloride was selected as the optimum coagulant. In the comparison between the ceramic and polymer membranes, there was no significant difference in removal efficiency; however, the ceramic membrane had a better water flux and lower membrane-fouling potential. Moreover, the efficiency increased when a coagulation process was used as the pretreatment. Thus, ceramic membranes are more efficient for treating high turbidity water.

Membrane Filtration of Effluent from a One-Stage Bioreactor Treating Anaerobic Digester Supernatant

A challenge in side-stream treatment of anaerobic digester supernatant is that the effluent does not meet discharge standards. To address this challenge, this study tested tubular multichannel ceramic microfiltration (MF) and ultrafiltration (UF) membranes for the post-treatment of anaerobic digester supernatant. Pollutant rejection (total suspended solids (TSS), COD, total nitrogen (TN), and total phosphorus (TP)), color removal, and membrane susceptibility to fouling were determined at various transmembrane pressures (TMPs) (0.2, 0.3, 0.4, 0.5 MPa). Both methods completely removed TSS. In MF, COD was removed with 48–76% efficiency at 0.2–0.4 MPa. In UF, COD removal efficiency was slightly higher, reaching 83.7% at 0.4 MPa. With both methods, pollutant removal did not increase at TMP of 0.5 MPa. With both MF and UF, color was reduced by 54–100%, irrespective of the TMP. At 0.2–0.4 MPa, membrane resistance was lower and permeate flux was much higher with MF than UF. At 0.5 MPa, the methods differed only slightly from each other. Due to the larger cut-off, flux decline was slower in MF (0.7 h−1) than in UF (1.1 h−1), as the larger pore-size favors less foulant deposition. Thus, taking into account rejection efficiency, capacity, washing frequency, and cost (pressure), these results indicate that MF at 0.4 MPa is the most effective variant for post-treatment of anaerobic digester supernatant. With this variant, the almost colorless permeate contained 25 mg COD/L, no TSS, 55 mg TN/L (75% in the form of nitrites and nitrates), and 8.5 mg TP/L, thus meeting criteria for water to be used in irrigation or algae cultivation.

Preparation of low-cost ceramic membranes for microfiltration using sugarcane bagasse ash as a pore-forming agent

Abstract Ceramic membranes are of great industrial interest in separation processes. They are characterized by high chemical and thermal stabilities and filtration capacity at high temperatures (&gt;500 °C) in a wide range of pH values. However, the major disadvantage of ceramic membranes is the high-cost of production involving synthetic raw materials, usually alumina and zirconia. In this work, low-cost ceramic membranes were prepared by solid-state reactive firing using a mixture of kaolinite clay and sugarcane bagasse ash. Particle size distribution, thermal, mineralogical, and chemical composition analyses were carried out to study the raw materials. Technological properties and water permeability were investigated in samples fired between 800 and 1000 °C. The filtration efficiency was measured by comparative analyses between the raw water and the filtrate. The mean pore size ranging from 2.5 to 6.0 μm makes the sugarcane bagasse ash derived ceramic membranes suitable for microfiltration processes.

Semi-industrial high-temperature ceramic membrane clarification during starch hydrolysis

Semi-industrial ceramic microfiltration (MF) membrane has been developed for clarifying maltodextrin solution resulted from cassava starch hydrolysis. In the laboratory test, the influence of transmembrane pressures (TMP 1, 1.5, and 2 bar) on permeate flux and degree of clarification were studied. At lower TMP (1 and 1.5 bar), the Jss of the ceramic membrane was approximately 12 L⋅m−2⋅h−1, while it was doubled at TMP 2 bar. The degree of clarification was improved by the change of TMP from 1 to 1.5 bar and then decreased by increasing the TMP to 2 bar. In the semi-industrial scale experiment, the influence of volume concentration ratio (VCR) on the degree of clarification was investigated. The degree of clarification values was decreased from 85% to 65% by the increase of VCR from 1 to 50. In economic point of view, the plant capacity of 1.0 m3 h−1 (7000 m3 year−1) was reasonably feasible with the production cost of maltodextrin of 1.73 US$ m−3. The MF membrane process offered annual cost savings of US$ 292,549 per year in comparison to RVPF process with pay pack period of 2.62 month and IRR at 6th month of 31.6%.

Preparation of novel porous ceramic microfiltration membranes from fly ash, kaolin and dolomite mixtures

In the present work, low-cost ceramic membranes were prepared by using kaolin (KA), fly ash (FA) and dolomite. The effects of sintering temperature and raw materials composition (i.e., 0–100 wt% of KA in the mixture of KA + FA) on the membrane properties (strength, porosity, pore size, permeability, etc.) were studied. The raw material mixtures were subjected to TGA and the prepared membranes were characterized by SEM, XRD, liquid permeation, mechanical strength and chemical stability tests. The SEM analysis evidenced that the membranes were free of defects and had homogeneous surface structure with evenly distributed pores of similar sizes. A sintering temperature of 900 °C was found to be optimum for both kaolin-based and fly ash based membranes. Addition of 20% dolomite provided sufficient porosity to all membranes (28–51%). The porosity, strength and stability increased, while the pore diameter decreased with an increase in the kaolin content (M0–M100). The sintered mixture with a kaolin content of 75% (M75) was identified as the best membrane among others based on the pore characteristics (mean pore diameter 0.62 μm and porosity 46.3%). When applied to oil-water separation, M75 showed excellent filtration performance with good separation efficiency (up to 97.4% for 100 mg/L oil and up to 98.8% for 200 mg/L oil). The average permeate quality obtained at 1.03 bar pressure difference was found to be within the safe discharge limit (<10 mg/L). Although, the permeate flux declined steadily with time, it has been recovered through membrane regeneration. Model fitting to the flux data indicated the formation of a cake layer because of concentration polarization at the membrane surface during dead-end filtration.

Chemical-grafting of graphene oxide quantum dots (GOQDs) onto ceramic microfiltration membranes for enhanced water permeability and anti-organic fouling potential

In this work, graphene oxide quantum dots (GOQDs) with an average size of around 3.8 nm were prepared by facile hydrolysis of citric acid. Subsequently, GOQDs were immobilized onto the (3-aminopropyl) triethoxysilane (APTES) functionalized alumina membrane surface by covalent bonding. The effects of GOQDs on the surface properties including the pore size, hydrophilicity and surface roughness, as well as water permeability and anti-organic fouling properties of ceramic membranes were systematically studied. The ceramic membranes modified by GOQDs could remain a porous structure with reduced surface roughness and improved hydrophilicity. Notably, the surface modification by GOQDs slightly decreases the average pore size from 200.8 nm to 191.3 nm, and the uniformity in pore size is improved at the same time. As a result, the GOQDs modified ceramic membranes show improved water permeability with an enhanced pure water flux (~30%) and reduced membranes resistance (~15%). Importantly, GOQDs modified ceramic membranes show much higher pure water flux and lower filtration resistance both before and after the static adsorption experiment, which compare favorably with those unmodified ones. In addition, the GOQDs modified ceramic membranes also show improved fouling resistance in HA solution under submerged conditions.