Ceramic Filters Research Articles

Removal of Copper Ions from Aqueous Solutions Using a Nanomembrane Ceramic Filter Doped with Magnetic Zeolite

This study investigates the removal of copper ions from aqueous solutions using a nanomembrane ceramic filter doped with magnetic zeolite. The filter was designed using indigenous materials quartz, clay, and CaCO3 each selected for its unique functional properties. Characterization via Scanning Electron Microscopy revealed a well-distributed porous structure that enhances the filter's adsorption capacity. XRD patterns confirmed the crystalline nature of the ceramic filter and the successful incorporation of magnetic nanoparticles into the membrane matrix. VSM analysis showed that the magnetic properties of the zeolite were superparamagnetic, with a maximum saturation magnetization of 0.08emu/g. Additionally, zeta potential measurements indicated a strong negative charge of -60.9mV on the material. The filter’s copper removal efficiency was tested under various conditions (pH, initial concentration, and contact time), achieving a maximum removal efficiency of 99% at pH 9 and an initial concentration of 60mg/L. Optimization of operational parameters using Response Surface Methodology (RSM) with a Box–Behnken design resulted in a satisfactory coefficient of determination (R² = 0.80), indicating a good fit between experimental data and predicted results. Overall, the comprehensive characterization and optimization results highlight the potential of nanomembranes filter as an effective and economical solution for copper removal water.

Advanced oxide-stabilized zirconia ceramics for flue gas filtration in air purification systems

Air pollution, largely driven by industrial activities and fossil fuel combustion, poses a critical threat to both the environment and public health. Addressing emissions, particularly from factories operating at extremely high temperatures, demands advanced filtration technologies capable of withstanding such severe conditions. Ceramic filters have emerged as a promising solution due to their superior thermal stability, chemical resistance, and mechanical durability. Among these, oxide-stabilized zirconia (OSZ) ceramics have garnered significant attention for their potential in high-temperature flue gas filtration. OSZ ceramics enhance the intrinsic properties of zirconia, such as its high melting point and mechanical strength, while stabilizing its phases to prevent performance-degrading phase transformations. This review comprehensively examines the role of phase transformations in ZrO2 materials, alongside the fabrication methods, structural characteristics, and advantages of ZrO2 ceramics in air filtration applications. The review examines various stabilizing agents used to maintain phase stability and optimize material performance under extreme conditions, highlighting the benefits of OSZ in flue gas filtration. Additionally, it covers recent advancements in OSZ synthesis and application, addressing critical limitations such as production challenges and the environmental impacts of large-scale use. The discussion emphasizes the move toward sustainable development in air filtration technologies. Finally, the review provides a forward-looking perspective on future research needs, aiming to further optimize OSZ ceramics for more effective and widespread industrial air pollution control, with a focus on improving performance, scalability, and environmental sustainability.

Low-cost filtering materials for domestic water treatment

The article investigates certain low-cost filtering materials and their filtration efficiency for open well sources in terms of economic access to clean water in Anakapalle, a suburb of Visa-khapatnam, India, during the pre-monsoon period of 2022. The corresponding research aimed to study a selection of filter materials including coconut shell activated carbon, rice husk ash, manganese modified sand, and graphene oxide, as well as assess their performance against selected physico-chemical parameters of water. Considering the basic idea of slow sand and gravity-based filtration, a setup was arranged with a cartridge filled with layers of filtering materials and a ceramic candle filter. Adsorption turned out the most pronounced removal mechanism that took place when utilizing the aforementioned filter materials. The main focus of the study was to reduce pH, TDS, hardness, alkalinity, chlorides and iron content by applying dif-ferent filtration removal mechanisms. The study results show a significant drop in turbidity, pH, TDS and chlorides, and small reduction in hardness when coconut shell activated carbon and rice husk ash were used as filtration media. Whereas the chemically coated medium – manga-nese modified sand – demonstrated a considerable fall in iron concentrations, graphene oxide sand was observed to reduce alkalinity for any sample source.

Employing miniaturized test methods to determine high-temperature strength of carbon-bonded alumina

The Brazilian disc test (BDT) and the ball-on-three-ball (B3B) test, both adapted for utilizing miniaturized specimens, are used to characterize the strength of ceramic filter materials made from carbon-bonded alumina (Al2O3-C) at temperatures up to 1500 °C. Conventionally manufactured Al2O3-C and environmentally friendly coal tar pitch-free variations of filter materials are investigated. To determine the fracture stresses and the Weibull distribution of the material’s strength, finite element models and the maximum likelihood method are used. Scanning electron microscopy of fracture surfaces gives insight into the microstructure of tested samples. The material strength of the pitch-free Al2O3-C was found to be inferior to the conventional alternative. The volume-related Weibull stress distributions revealed that the uniaxial strength of the conventional filter materials exhibited an increasing trend as temperature increased, which was contrary to the biaxial strength.

Predicting removal of arsenic from groundwater by iron based filters using deep neural network models

Arsenic (As) contamination in drinking water has been highlighted for its environmental significance and potential health implications. Iron-based filters are cost-effective and sustainable solutions for As removal from contaminated water. Applying Machine Learning (ML) models to investigate and optimize As removal using iron-based filters is limited. The present study developed Deep Learning Neural Network (DLNN) models for predicting the removal of As and other contaminants by iron-based filters from groundwater. A small Original Dataset (ODS) consisting of 20 data points and 13 groundwater parameters was obtained from the field performances of 20 individual iron-amended ceramic filters. Cubic-spline interpolation (CSI) expanded the ODS, generating 1600 interpolated data points (IDPs) without duplication. The Bayesian optimization algorithm tuned the model hyper-parameters and IDPs in a Stratified fivefold Cross-Validation (CV) setup trained all the models. The models demonstrated reliable performances with the coefficient of determination (R2) 0.990–0.999 for As, 0.774–0.976 for Iron (Fe), 0.934–0.954 for Phosphorus (P), and 0.878–0.998 for predicting manganese (Mn) in the effluent. Sobol sensitivity analysis revealed that As (total order index (ST) = 0.563), P (ST = 0.441), Eh (ST = 0.712), and Temp (ST = 0.371) are the most sensitive parameters for the removal of As, Fe, P, and Mn. The comprehensive approach, from data expansion through DLNN model development, provides a valuable tool for estimating optimal As removal conditions from groundwater.

Development of sol-gel synthesis and characterization of meso porous SiO2 nanopowder for improvement of nanomullite/SiC ceramic filter

The study investigates the synthesis of mesoporous SiO2 nanoparticles with uniform spherical morphology via the sol-gel method. A strategic approach of this research was to control the particle size within the sol, achieved by incorporating ammonium polycarboxylate (APC) as an additive. The primary objective of this paper is to utilize these modified particles in the fabrication of ceramic filters for metal melt filtration, aiming to enhance their functional properties. Various analytical methods, including DLS, XRD, FTIR, DTA/TG, XPS, SEM, and TEM/EDS, were employed to evaluate the product formation mechanism during the sol-gel process. It was demonstrated that by controlling the pH within an acidic range of 3, precursor particles containing the Si source formed in sizes below 10 nm within the sol, a phenomenon that is fundamental in controlling the final product size to be under 50 nm. The addition of APC, through an electrosteric mechanism, contributed to the stability of the precursor particles within the sol. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images revealed that the silica nanoparticles possess a spherical shape with a uniform size of approximately 25 nm. Nitrogen adsorption/desorption porosimetry indicated that the nanoparticles have mesoporous with an average pore size of 2.5 nm and a specific surface area of 120 m2/g. This method can be conveniently used to prepare silica nanoparticles with desirable morphology and mesostructure. Polyurethane foam filters were impregnated with nanosilica particles using a slurry casting method. Subsequently, the effects of varying percentages of nanosilica particles in the slurry on the compressive strength, density, and porosity of the ceramic foam filters were examined. Additionally, the impact of silica nanoparticles on the slurry's viscosity was studied using rheometry. The optimal sintering temperature was reported to be 1250 °C. XRD results indicated the formation of mullite phase alongside silicon carbide and alumina phases at 1250 °C. SEM microstructural analysis showed that the mullite phase formed in nanometric dimensions within the ceramic foam bodies. The emergence of the mullite phase in nanometric dimensions within the filter microstructure is one of the factors contributing to the reinforcement and enhancement of refractoriness.

FEM Analysis on Isotropic Consolidation of Unsaturated Soils Using Ceramic Disks and Microporous Membrane Filters for Suction Control

Abstract Microporous membrane (MM) filters with a significantly thin thickness have recently been used as an alternative to ceramic disks for matric suction control in the axis-translation technique for element tests on unsaturated soils. Although researchers have highlighted some discrepancies in test results when ceramic disks and MM filters are used, the mechanism leading to these discrepancies has not yet been clarified. In this study, suction-controlled triaxial tests were first conducted on unsaturated completely decomposed granite using two filters. Then, it is natural to believe that the different thicknesses of ceramic disk and MM filters may significantly influence the suction equilibrium process of specimens. To clarify this issue, soil-water-air coupled finite element modeling was performed to simulate the consolidation process in triaxial tests as an initial/boundary value problem. In the numerical calculation, the influence of the void ratio on the water retention curve (WRC) of soil was properly considered by adopting a deformation-dependent WRC model. In particular, the ceramic disk and MM filter, along with the specimens, were modeled, and their differences in thickness were considered. The calculated results show that a nonuniform distribution of suction occurred in the ceramic disk, leading to greater drainage discharge of the specimens. In other words, the influence of the thickness difference between the MM filter and ceramic disk cannot be neglected. However, regardless of whether ceramic discs or MM filters are used, the uneven distribution of the state variables in the specimens may occur in the triaxial tests for unsaturated soils, which emphasizes the importance of assessing the soil tests using the present axis-translation technique as initial/boundary value problems.

Ceramic foam filters with concentrated carbon binder surfaces for copper melt filtration

In this study, the impact of coal tar pitch coatings on carbon-bonded alumina samples were investigated. The coal tar pitch coating had no effect on the bending strength of bar samples compared with an uncoated reference but a reduction of the median pore size was observed for samples coated with the coal tar pitch and coked 1x. Furthermore, differences in the measured contact angles were detected. The highest contact angles under low atmospheric pressure (<1.8 × 10−5 mbar) were measured for 2x coked coal tar pitch-coated (Carbores P) samples (152°). A liquid coal tar pitch coating (Carbores T10) showed the lowest contact angle at 126°.Strong gas bubbling during the sand-casting trial showed the formation of a gas resulting in large pores in the cast copper samples.The strong oxidation of the carbon at the surface of the filters is regarded as the reason for the gas formation, with the oxygen originating from both the air within the filter before priming, the sand mold around it and from the oxygen dissolved in the melt.

Deposition of Imidazole into Mesoporous Zirconium Metal-Organic Framework for Iodine Capture.

Efficient capture of radioiodine is essential for the protection of the ecological environment and the sustainable development of nuclear energy generation. Metal-organic frameworks (MOFs) and their derivatives provide alternative potential for overcoming the limitations of traditional iodine adsorbents. Herein this work, imidazole (Im) is dispersed into a robust mesoporous zirconium MOF PCN-222 by the heat deposition method, forming a high-uniformity composite Im@PCN-222. The large pore size and marked chemical resistance skeleton of PCN-222 allow the incorporation of Im to reach 43 wt % while surviving the chemical corrosion of activated Im. The nearly saturated loading of Im significantly benefits the sorption capability toward iodine and gives rise to an exceptional adsorption capacity of 10.04 g g-1 and excellent recyclability. This value is higher than that of most of the MOFs and their derivatives. Further, Im was also successfully deposited onto the PCN-222 functionalized porous Al2O3 ceramic filtration membrane, which endowed the hybrid membrane with efficient iodine sorption and separation properties. This work highlights a new strategy for the fabrication of the MOF-based radioiodine adsorption composite as well as MOF composite-based filters.

Sintered Clays: Application in the Removal of Arsenic from Water by Filter Beds

Objectives: The main objective of the research was to build a ceramic filter bed, using red clay and diatomite, for the removal of arsenic in aqueous media and to propose an environmentally friendly and low-cost technique for rural communities in Peru that consume water contaminated with arsenic. Theoretical framework: Arsenic is a common contaminant in the drinking water of many rural communities in Peru, exceeding the limits allowed by the WHO. Prolonged exposure to arsenic can cause serious health problems. The use of low-cost non-metallic materials, such as thermally activated clay and diatomite, is proposed for its adsorption. Method: A filter bed composed of 5 cm layers of red clay and diatomite with particle sizes of 0.81, 0.31 and 0.20 mm was used. Both materials were thermally activated at 900°C and placed on a stainless steel support. The arsenic removal process was evaluated by passing a synthetic solution with 13.99 ppm of arsenic through the bed. Material characterization analyses were performed before and after the adsorption process, using techniques such as ICP-OES, SEM, FTIR, among others. Results and discussion: The filter bed composed of diatomite (83.31% SiO2) and red clay (8.23% Fe2O3) achieved an arsenic removal of up to 99.99%, highlighting the efficiency of particles with a size of 0.20 mm. This shows that the combination of these materials can be highly effective in removing arsenic in water, which is promising for its implementation in rural areas. Research implications: This research has important implications for water treatment in rural communities facing arsenic contamination problems. The technique developed is low-cost and uses abundant resources, which facilitates its application at the local level and promotes sustainable solutions for access to safe drinking water. Originality/Value: The research provides a novel approach through the use of red clay and diatomite, accessible resources, thermally activated for the removal of arsenic in water. In addition, the high removal effectiveness achieved provides a potentially scalable and replicable solution in other rural communities with similar problems.

Sustainable recycling of pure aluminum from waste chips under supergravity-enhanced separation: A cleaning process

Large quantities of chips containing high levels of aluminum are always inevitably produced during machining process of aluminum products, which is a valuable renewable resource. In this paper, an environmental-friendly method for direct and continuous recovery of same-level recycled Al from waste chips under supergravity-induced was proposed. The oxide film covering the surface of the molten Al-chips was easily disrupted under super-gravity, and subsequently almost all of Al melt detached from the oxide film and flowed rapidly through the microporous ceramic foam filter, with a yield ratio of more than 97 %. During this process, all fine broken oxide-film particles and large amounts of primary iron-rich particles in the melt were captured in the complex channels of the filter, resulting in clean 1xxx series recycled Al with free inclusions and impurity iron content of less than 0.28 wt%. In addition, a sustainable process and a continuous centrifugal unit for recycling aluminum chips were designed, the economic and environmental advantages of which demonstrate the feasibility of sustainable regeneration of aluminum chip resources on an industrial scale via supergravity technique.

Efficiency of Ceramic Composite Filter Produced Using Nano Particulate Carbonaceous Material

Millions of people have no access to safe water. This has led to continued incidence of waterborne diseases with severe cases of complications and sometimes death. Attempts to use silica sand-based materials for the production of filters by researchers are still evolving. In this study a novel hybrid clay-nanoparticulate agro-waste blend water filter with appropriate pore size and flow rate for contaminant-free water filtration was produced. The composite filters were produced using hydraulic pressing and sintering process. Four different ratios of clay, activated carbon and nanoparticle coconut shell (60:30:10, 60:20:20, 60:10:30, and 60:0:40 wt %) were mixed and fired at 700 °C, 750 °C, 800 °C, 850°C, 900 °C, 950 °C, and 1000 °C respectively at the rate of 75 °C/hr. E. Coli, Total Coliform, and turbidity tests were carried out on the influent water collected from Lagos Lagoon, and effluent water samples were filtered using the produced samples. The result of water tests revealed that all the filters produced removed between 86.81 % to 99% Escherichia Coliform (E. coli), and 81.81% to 93.31%% total coliform in the water sample. The blend of 60:10:30 fired at 850 °C and 900 °C showed improved properties with a flow rate value of 2.83 l/hr and 2.77 l/hr. In conclusion, the study established that synthesis of nanoparticle coconut shell and activated carbon is a suitable material for producing clay composite filters that can purify water to Nigerian Standards for Drinking Water Quality (NSDWQ) acceptable level.

The Concept of Using 3D Printing Technology in Ceramic Foundry Filter Manufacturing

The article presents the concept of using 3D printing technology in ceramic foundry filter manufacturing. They are a crucial component for obtaining an acceptable quality of nickel superalloys by carrying out the process using the precision casting method. Commonly used filters of this type have a number of disadvantages. They are characterized by irregularity of the filtering structure, high brittleness, lack of resistance to mechanical shocks, and impacts of a stream of liquid metal. All these factors create a risk of introducing the material from the damaged filter into the casting mold, which translates into contamination of the casting alloy, and thus the occurrence of casting defects such as nonmetallic inclusions. The hope for a change in this state of affairs is the use of additive manufacturing technology in their production, which by assumption will allow to obtain a product with a repeatable shape, high mechanical resistance, and a specially designed structure regulating the flow of liquid metal into the mold during casting. The suitability of robocasting and binder jetting technology for producing filtration structures was initially assessed. The results have presented the selection of ceramic powder, as well as the development of the composition of the ceramic paste. The parameters of paste preparation and 3D printing individual processes were described. Moreover, the representative microstructures and basic mechanical properties of samples obtained by both of the compared technologies were presented. Furthermore, the final effect of prototype casting filters with a repeatable shape, manufactured with the use of both technologies, was presented, which were transferred for further technological research in a foundry producing critical aircraft engine parts. The possibilities of using each technology in various applications were also discussed.

Monolithic ceramic waveguide filter using a transition between GCPW feed and ceramic waveguide for 28 GHz

AbstractIn this letter, a mm‐wave monolithic ceramic waveguide filter using a transition between a grounded coplanar waveguide (GCPW) feed and a ceramic waveguide has been proposed. The published studies on monolithic ceramic waveguide filters with wideband properties for the mm‐wave are lacking. A desired external quality factor, satisfying wide bandwidth, is achieved using both inductive and capacitive couplings in the transition. The inductive coupling is realized with a waveguide's hole directly connected to the microstrip line probe of the GCPW. The capacitive coupling is employed with the slots of both GCPW and ceramic waveguide, which are placed facing each other. Adopting the presented transition, the inline monolithic ceramic waveguide filter for a fourth‐order Chebyshev response was designed. The fabricated filter provided the insertion and return losses of lower than 1.2 dB and higher than 10 dB, respectively, at frequencies from 26.43 to 29.76 GHz, with a fractional bandwidth of 11.85%.

Enhancement of strength and thermal shock resistance of MgO‐MgAl2O4 ceramic filters with microporous MgO powder: Effect of α‐Al2O3 micro‐powder content

AbstractIn this work, MgO‐MgAl2O4 ceramic filters were fabricated from microporous MgO powder and α‐Al2O3 micro‐powder, in which microporous MgO powder was prepared using Mg(OH)2 as initial raw material. With the α‐Al2O3 micro‐powder content increased from 0 to 15 wt%, the tight packing and reaction sintering between MgO microparticles and Al2O3 microparticles promoted the formation and growth of magnesium aluminate spinel necks, reduced the apparent porosity of ceramic filter skeletons, decreased the pore size, and improved the strength of the filters. When the α‐Al2O3 micro‐powder content further raised to 20 wt%, the thermal mismatch between MgO microparticles and spinel microparticles caused a small amount of crack generation, which lowered the strength of the filter. Besides, after introducing the α‐Al2O3 micro‐powder, more spinel necks were produced due to a small amount of MgO solid dissolved in the spinel lattice during the thermal shock test, which enhanced the thermal shock resistance of the filters. When the α‐Al2O3 micro‐powder content was 15 wt%, the filter had excellent comprehensive performance, the bulk density and apparent porosity of the filter skeleton were 3.09 g/cm3 and 10.7%, and the compressive strength before and after thermal shock test was 3.48 and 3.70 MPa, respectively.

Assessment of an Advanced Water Filtration System for Enhanced Water Purification

The study confirms the effectiveness of a state-of-the-art water filtration system in purifying urban tap water, river water, and groundwater. The system, which uses activated carbon, ceramic, and reverse osmosis (RO) filtration, significantly improved water quality by removing physical, chemical, and biological contaminants. Key results include: The system achieves a turbidity reduction of up to 99.5%, adhering to WHO standards. The system removes over 96% of volatile organic compounds (VOCs) and chlorine, and more than 99% of heavy metals like lead and arsenic. The water is completely free of harmful bacteria, guaranteeing its microbiologic safety. There has been a 98.2% reduction in total dissolved solids (TDS) in groundwater. The study highlights the system's adaptability to diverse environments, including urban, rural, and industrial settings. Future research could focus on improving the system's energy efficiency and sustainability.

High-Performance monolithic ceramic waveguide filter with isosceles Right-Angled triangular resonator for base station applications

This paper presents a high-performance integrated monolithic ceramic dielectric waveguide (DW) filter featuring isosceles right-angled triangular (IRAT) resonators. The fabrication process of the filter involves embedding a specific number of blind holes (BHs) or through holes/slots (THs/TSs) in a hexagonal ceramic dielectric block, fully metallizing the dielectric surface, and forming a monolithic ceramic DW filter. To achieve magnetic coupling, four THs and a BH are introduced in the oblique edges of two IRAT resonators; alternatively, a TS and BH are introduced in their right-angled edges. Electrical coupling is realized through a deep BH on the right-angle side of the resonators. Two non-adjacent resonators initiate weak cross-coupling by cascading a T-shaped rectangular TS, shallow BHs, and deep BH, creating two transmission zeros (TZs) outside the band. The filter was fabricated to ensure theoretical correctness and process reliability. The measured results show an insertion loss between 0.5 – 1 dB and a return loss greater than 18 dB at a bandwidth of 3.4 – 3.6 GHz. Two steep out-of-band TZs occur at 3.26 GHz and 3.72 GHz, aligning with simulation results. Therefore, the filter not only exhibits excellent performance but is also convenient for mass production and manufacturing, offering significant potential for future applications in 5G / 6G communication base stations.

Mullite effect on the ceramic filters effectiveness in the removal of arsenic from borehole water from Burkina Faso

In recent years, porous ceramics have been widely studied because of their excellent technological properties. The intrinsic technological characteristics depend on the forming process and the application for which the materials are intended. A clay raw material (75 mass%) which is rich in melting oxides and waste peanut shells (25 mass%) were used to manufacture porous ceramics for the removal of arsenic from borehole water in Burkina Faso. A borehole water analysis shows a concentration of arsernic of 39 μg L−1 above the WHO standard. The porous ceramics were obtained from samples shaped by unidirectionnal pressing and after sintering at 900 °C (MKOR9) or 1100 °C (MKOR11). Unlike MKOR9 materials, MKOR11 materials consist of 27 % mullite phases. MKOR9 and MKOR11 porous materials presented a diametrical compression stress to rupture greater than 0.15 MPa, as recommended in the literature for ceramic filters. The obtained permeability value of MKOR11 ceramic materials (53,802 L/h.m2.bar) is much higher than that of MKOR9 (18596 L/h m2 bar), although its open porosity (61 %) is lower than that of MKOR9 materials (65 %). The removal rate obtained with MKOR9 is 24 % compared to 95 % for MKOR11. MKOR11 filters almost completely reduce arsenic concentration below the WHO limit values, which is not the case for MKOR9 materials. The adsorption kinetics and thermodynamic parameters showed that the adsorption process is the chemisorption. This work has shown that MKOR11 ceramic filters have a very impressive effectiveness, and they could be manufactured for the benefit of the remote population.

SNAIL CONSUMPTION AND SNAIL SHELL UTILIZATION: PERCEPTION OF UISHOPWEL AND MEAT SHOP CUSTOMERS

The increasing demand for snails, driven by their high protein content and medical value, has led to heightened interest in both domestic and foreign markets. However, the shells of these snails often face neglect during processing, posing environmental challenges. To address this, a study was conducted at the University of Ibadan, UishopweL, and meat shops in Ibadan metropolis. Seventy-four structured questionnaires were administered to gather insights into factors influencing snail consumption, methods of processing snail shells, and their potential uses. The findings highlighted that 45.9% of respondents attributed snail consumption to allowances, while 12.2% considered family background, 32.4% mentioned environment, 13.5% focused on taste, 6.8% took health conditions into account, 8.1% noted a nonchalant attitude, 12.2% considered age, and 47.3% emphasized the availability of snail meat. Additionally, 86.5% recognized the snail shell as an excellent calcium source, with 81.1% acknowledging its use as a ceramic filter, 63.5% in paint, 74.3% in animal feeds, 66.2% in construction, 39.2% in paper industries, 74.3% for enhancing product hardness, and 78.4% for strengthening materials. Regarding snail shell processing, 10.9% burned shells for calcium extraction, 2.7% ground and crushed them, 78.4% discarded them, and 8.1% did not specify. The study concluded that respondents were generally aware of the various uses of snail shells, particularly their role as a natural source of calcium and their potential in animal feeds.

Open-cell ceramic foam filters for melt filtration: Processing, characterization, improvement and application

Open-cell ceramic foams are widely used as filters for the purification of molten metals due to their high permeability and high efficiency for capturing non-metallic inclusions. With the consideration of manufacture and filtration behaviour, most filters are produced by replica methods. The intrinsic multiscale porous structure requires the ceramic foams to have sufficient strength. As a consequence, different processing approaches, material compositions and characterizations are investigated. Meanwhile, to further enhance the filtration performance, the functionalization of ceramic foam filters is often conducted with surface coating. This review summarizes the processing and characteristics of ceramic foam filters (CFFs), the nature and formation of non-metallic inclusions (NMIs), the filtration mechanism and applications of CFFs. The characterization of mechanical and filtration performance, as well as the corresponding strengthening and functionalization methods are also presented.