Ceramic Nanofiltration Membranes Research Articles

Construction of TiO2-ZrO2 composite nanofiltration membranes for efficient selective separation of dyes and salts

The ceramic nanofiltration (NF) membrane exhibits excellent potential for textile wastewater treatment due to its efficient selective separation of dyes and salts. In this study, a high-performance TiO2-ZrO2 composite nanofiltration membrane was fabricated via a sol–gel method. Stable sols with an average particle size of approximately 2 nm were obtained. The addition of TiO2 effectively inhibits the phase transformation of ZrO2 during heat treatment, thus improving the integrity and ensuring separation accuracy of the membrane. Moreover, an optimal balance between membrane integrity and thickness was achieved, promoting efficient selectivity towards dyes and salts. The optimized NF membrane exhibited a MWCO of 1 kDa, a membrane thickness of 100 nm, and pure water permeance of 44 L∙m−2∙h−1∙bar−1. Additionally, the NF membrane demonstrated exceptional performance in dye/salt separation as evidenced by rejection rates exceeding 97.71% for Reactive Blue 19 while maintaining rejections below 5% for NaCl/Na2SO4 solutions. A stable permeance of 21.65 L∙m−2∙h−1∙bar−1 was achieved during the separation process. In conclusion, this study presents a high-performance ceramic NF membrane which exhibits significant potential for treating dye/salt containing wastewater.

Compact SiOC ceramic composite nanofiltration membranes by slow dip coating for water purification

In this work, novel silicon oxycarbide (SiOC) ceramic composite nanofiltration membranes with high performance were successfully synthesized at low sintering temperatures by gradual dip-coating approach for the first time. The slow dip-coating process facilitated improved wetting and even spreading of the precursor solution across the substrate. This controlled method ensured the formation of uniform and continuous SiOC ceramic membranes without the introduction of substantial defects or irregularities. Consequently, the systematic approach minimized the occurrence of pinholes, cracks and other structural imperfections in the SiOC ceramic membranes. The synthesis of the SiOC separation layer involved the sintering of polymeric polysilicon as precursor, which caused a lower decomposition temperature in contrast to the conventional method employing silicon carbide powder for sintering. The specific feature enabled a sharp decrease in the sintering temperature which was required for the formation of the separation layer. The prepared SiOC ceramic composite nanofiltration membranes exhibited good permeability with high rejection of dye molecules (>95%) and maintained stable water flux for at least 24 h, showing good long-term stability during cross-flow filtration. This progress provides new approach for the fabrication of compact ceramic nanofiltration membranes with low sintering temperatures, high separation efficiency and enhanced stability.

Nanofiltration Ceramic Membranes as a Feasible Two-Pronged Approach toward Desalination and Lithium Recovery.

Ceramic membranes are taking center stage for separation technologies in water treatment. Among them, ceramic nanofiltration membranes are at the forefront of membrane technologies. The desalination of seawater using ceramic nanofiltration membranes is a potential application toward increasing the global water supply and tackling water scarcity. However, while the high fabrication cost poses a challenge to their large-scale applications, high-value separation applications can help to offset the overall cost. In this regard, ceramic nanofiltration membranes can also be explored as a viable option for high-value lithium extraction from the waste seawater brine. In order to determine the potential of nanofiltration ceramic membranes for desalination and lithium recovery from seawater, the current efficiency of salt rejection across various operation parameters must be thoroughly evaluated. Specifically, the interactions between the Donnan exclusion, steric exclusion, zeta potential, and salt concentration play an important role in determining the salt rejection efficiency. Several strategies are then proposed to guide ceramic nanofiltration membranes toward potentially practical applications regarding desalination and lithium recovery.

Tuning Nanopores in Tubular Ceramic Nanofiltration Membranes with Atmospheric-Pressure Atomic Layer Deposition: Prospects for Pressure-Based In-Line Monitoring of Pore Narrowing

Atomic layer deposition (ALD) is known for its unparalleled control over layer thickness and 3D conformality and could be the future technique of choice to tailor the pore size of ceramic nanofiltration membranes. However, a major challenge in tuning and functionalizing a multichannel ceramic membrane is posed by its large internal pore volume, which needs to be evacuated during ALD cycling. This may require significant energy and processing time. This study presents a new reactor design, operating at atmospheric pressure, that is able to deposit thin layers in the pores of ceramic membranes. In this design, the reactor wall is formed by the industrial tubular ceramic membrane itself, and carrier gas flows are employed to transport the precursor and co-reactant vapors to the reactive surface groups present on the membrane surface. The layer growth for atmospheric-pressure ALD in this case proceeds similarly to that for state-of-the-art vacuum-based ALD. Moreover, for membrane preparation, this new reactor design has three advantages: (i) monolayers are deposited only at the outer pore mouths rather than in the entire bulk of the porous membrane substrate, resulting in reduced flow resistances for liquid permeation; (ii) an in-line gas permeation method was developed to follow the layer growth in the pores during the deposition process, allowing more precise control over the finished membrane; and (iii) expensive vacuum components and cleanroom environment are eliminated. This opens up a new avenue for ceramic membrane development with nano-scale precision using ALD at atmospheric pressure.

Catalytic pre-coat on ceramic nanofiltration membranes for segregation and Fenton cleaning of high-resistance colloids in direct surface water treatment

Ceramic nanofiltration (NF) is a promising alternative for direct surface water treatment, but is hampered for full-scale applications by fouling and a lack of eco-friendly cleaning regimes. In this work, an innovative reactive pre-coat layer, consisting of an iron oxychloride catalyst, was constructed on top of commercial ceramic NF membranes, for segregating a large-sized colloid fraction in canal water and Fenton cleaning with a hydrogen peroxide (H2O2) solution. The large-sized colloids (3−30 μm) were identified as dominant substances fouling the TiO2 separation layer of the pristine membranes, leading to a fast increase in their filtration resistance, in contrast to the small-sized colloids (<0.04 μm) and natural organic matter (NOM). As a consequence, the catalyst pre-coat layer with a pore size of 0.1–0.5 μm was able to segregate the large-sized colloids from the TiO2 separation layer during direct filtration of the raw water. Moreover, filtration under an acceptable flux of around 23 L m−2 h−1 did not cause pore clogging in the catalyst pre-coat. In addition, Fenton oxidation initiated by the catalytic pre-coat efficiently restored the filtration resistance, whereas sole H2O2 flush of the pristine membrane was not effective. In the meantime, the TiO2 separation layer of the membrane exerted a high NOM rejection of approximately 90%, measured as dissolved organic carbon, while the catalyst pre-coat on the membrane remained active in Fenton cleaning, over five one-day cycles. The findings of this work may provide guidance on the structural and functional design of a catalytic pre-coat layer for a dual purpose of foulant segregation and oxidative removal, particularly in response to key fouling-causing substances, during membrane-based treatment of real water matrices.

Mxene-based ceramic nanofiltration membranes for selective separation of primary contaminants in semiconductor wastewater

Ceramic membranes, known for their exceptional chemical stability, have found practical applications in the treatment of semiconductor wastewater. In this study, we have developed an innovative ceramic nanofiltration membrane featuring a nanochannel network created by two-dimensional (2D) nanomaterials, enabling high-performance separation and permeation. This accomplishment is realized through precise control of the size and thickness of MXene nanomaterials, which can be tailored using various coating conditions. The repeated stacking of MXene nanosheets onto the ceramic membrane substrate resulted in the formation of additional nanochannels and surface chemistry modifications, leading to significant enhancements in pollutant removal. These MXene-coated ceramic nanofiltration (NF) membranes significantly improved the removal efficiency of representative organic contaminants in semiconductor wastewater when compared to the pristine ceramic membrane. It enhanced the removal efficiencies by 4.2 times for dissolved silica, 3.7 times for dimethyl sulfoxide (DMSO), and 2.5 times for isopropyl alcohol (IPA). Furthermore, the MXene ceramic NF membrane exhibited exceptional fluoride removal capability, achieving approximately 99.1% removal, in addition to organic solvents. These findings not only help meet regulatory standards for wastewater discharge but also provide valuable insights into the transport behaviors of contaminants and their separation mechanisms. This innovative approach brings us one step closer to efficient and sustainable solutions for semiconductor wastewater treatment.

Adsorption and cake layer fouling in relation to Fenton cleaning of ceramic nanofiltration membranes

Catalytic ceramic nanofiltration (NF) is a promising technology for direct wastewater reclamation, given its high separation selectivity and reactive surfaces for oxidative removal of fouling. A better understanding of the relation between fouling types and oxidative cleaning efficacy under high organic loading conditions is of practical importance for realizing stable filtration/cleaning performance in long-term water reclamation operations. In this work, Fenton cleaning, using a hydrogen peroxide solution and an iron oxychloride catalyst pre-coat layer on top of commercially available ceramic NF membranes, was studied with respect to high organic loaded fouling, simulated by a concentrated sodium alginate solution in the presence of calcium. Adsorption (in the absence of a permeate flow) and constant-pressure filtration (with a permeate flow) experiments were performed to distinguish between permeance decreases as a result of either adsorptive or cake layer fouling. The results show that the flux evolution could be divided into an initial sharp flux decline, due to rapid adsorption of the foulants, and a subsequent gradual flux decrease, resulting from progressive cake build-up on the membrane. The two-stage flux decrease was enhanced during the constant-pressure filtration experiments, because they start at a high flux with a high fouling rate, while the flux gradually decreases as fouling proceeds. During multiple adsorption/cake filtration/Fenton cleaning cycles, the cake layer fouling was sufficiently removed by Fenton cleaning in contrast to the adsorptive fouling. However, the total permeate production during ceramic NF was not influenced by the remaining adsorptive fouling (after cleaning), since the adsorptive fouling always only occurs at the beginning of each cycle. The findings provide new insights into the criteria for evaluating and optimizing the efficacy of oxidative (Fenton) cleaning during ceramic NF in water treatment.

Investigating the efficiency of a ceramic-based thin-film composite nanofiltration membrane for dyes removal

This study focuses on producing polyamide thin-film composite (TFC) ceramic membranes using interfacial polymerization, resulting in a polyamide layer on ceramic tubular substrates (Al2O3). These Al2O3 substrates possess robust mechanical and physical traits, featuring a porous surface structure. TFC membranes exhibit a thin, dense structure with root-like nanostructures on the ceramic base, with a thickness of around 260 nm. Atomic force microscopy confirms the smoother surface of TFC membranes with an average roughness value of 18 nm compared to ceramic tubular substrates. TFC membranes exhibit negative zeta potentials within a pH range of 4.7–10, while ceramic tubular substrates show more complex zeta potential behavior. Both substrate and TFC membranes are hydrophilic, with the TFC membrane having a slightly higher water contact angle (approximately 43 ± 1°). Zeta potential analysis reveals a negative potential of around −23 mV for the TFC membrane. In water permeability tests, the ceramic tubular substrate membrane demonstrates high permeability, whereas the TFC membrane displays slightly lower permeability (28 ± 0.8 L/m2 h bar) due to the presence of the polyamide selective layer. Importantly, the TFC membrane significantly enhances organic dye rejection compared to the ceramic tubular substrate, with rejection rates of 95% for CR, 92% for BTB, and 86% for MB. Rejection performance is mainly influenced by size exclusion and dye molecular charge. These novel TFC ceramic nanofiltration membranes offer improved water permeability while maintaining selectivity, holding promise for effectively removing organic pollutants in water treatment applications.

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

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

Experiment on and modeling of purification of fructooligosaccharides using ceramic nanofiltration membranes

High-purity fructooligosaccharides (FOS) with high economic value have been widely used in the food and medical fields. The use of ceramic nanofiltration (NF) membranes with narrow pore-size distributions have been proven to be a promising strategy for purifying FOS. The preliminary screening of membranes according to the retention rate of each membrane itself is more scientific than basing it only on the molecular weight cut-off. In addition, the yield, purity, membrane flux, and washing water volume of the product should be considered comprehensively. Here, the concentration of FOS feed should be controlled within 100 g·L−1, with the suggested settings for transmembrane pressure, cross-flow velocity, and operating temperature being 0.7 MPa, 1.2 m·s−1, and 60 °C, respectively. The model analysis showed that the NF membrane with a high separation factor and low non-prebiotic sugar rejection rate can obtain a high FOS yield and purity with less leachate addition. Moreover, the ceramic NF membrane can maintain a stable separation performance during the separation process, and the pure water flux can be recovered after cleaning, which has good application prospects in the FOS purification industry.

Preparation and dye separation performance of ZIF-67/mesoporous silica ceramic nanofiltration membrane by liquid phase epitaxy (LPE) growth method

Ceramic membrane plays an important role in separation process with advantages of high thermal and chemical resistances, but its applications on the nanofiltration are restricted because of the limitation of pore size. In this study, a commercial tubular ceramic membrane with pore diameter of 0.1 μm was firstly coated with mesoporous silica substrates, in which ZIF-67 nanocrystals were generated layer-by-layer inside the mesochannels via liquid phase epitaxy growth method. The open pore size of ceramic membrane can be precisely controlled by increasing the growth cycles of ZIF-67 nanocrystals. The influence of preparation conditions on the dye separation was investigated, including growth cycles, precursor concentration, and molar ratio of Co2+/2-methylimidazole (Co2+/Hmim). Under the optimized conditions, the rejection of methylene blue, methyl orange, chromium black T, rhodamine B, acid fuchsin, and Congo red were in the range of 92–99 % with membrane fluxes of 0.45–0.73 L m−2 h−1. Bovine serum albumin solution was used to evaluate the anti-fouling abilities of the ceramic membrane. The flux recovery ratio, which was calculated according to the ratio between the water permeance after washing and before filtration, was 52.3 % with the flux decline rate of 66.3 %.

Role of co-existing ions in the removal of dissolved silica by ceramic nanofiltration membrane

Even low concentrations of nano-sized silica particles should be effectively removed from chemical mechanical polishing (CMP) wastewater as they can corrode the pipes in semiconductor manufacturing processes. In this study, we systematically investigated the factors affecting the silica removal efficiency using ceramic nanofiltration (NF) membranes under different conditions to remove nano-sized dissolved silica, which is difficult with conventional microfiltration (MF) or ultrafiltration (UF) membranes. A tubular ceramic NF membrane with an average pore size of approximately 946 Da (≈1.3 nm) was strongly negatively charged at pH values above 4.0, indicating the existence of repulsive forces between the membrane and monoanionic silica (H3SiO4−) under basic pH conditions. As the pH level increased from 4 to 12, retention increased from 10.6 % to 62.0 %, and it also increased with increasing concentration of dissolved silica and applied pressure. We also investigated the effect of combined salt solutions (KCl, K2SO4, CaCl2, or CaSO4) on the removal efficiency for dissolved silica to better understand the mechanism for underlying the operating conditions. When dissolved silica was the only contaminant in the solution, 61.6 % was removed however, the presence of cations such as Ca2+ with higher valence reduced the removal efficiency by up to 20.5 %. The presence of calcium compounds that bonded to higher-valence anions had a greater impact on the removal efficiency for dissolved silica. Our findings can serve as guidance for the selection of suitable coagulants and the improvement of the membrane performance through fine control strategies in semiconductor wastewater treatment processes.

A Facile Way to Fabricate GO-EDA/Al2O3 Tubular Nanofiltration Membranes with Enhanced Desalination Stability via Fine-Tuning the pH of the Membrane-Forming Suspensions.

Pristine graphene oxide (GO)-based membranes have proven promising for molecular and ion separation owing to efficient molecular transport nanochannels, but their separation ability in an aqueous environment is limited by the natural swelling tendency of GO. To obtain a novel membrane with anti-swelling behavior and remarkable desalination capability, we used the Al2O3 tubular membrane with an average pore size of 20 nm as the substrate and fabricated several GO nanofiltration ceramic membranes with different interlayer structures and surface charges by fine-tuning the pH of the GO-EDA membrane-forming suspension (pH = 7, 9, 11). The resultant membranes could maintain desalination stability, whether immersed in water for 680 h or operated under a high-pressure environment. When the pH of the membrane-forming suspension was 11, the prepared GE-11 membrane showed a rejection of 91.5% (measured at 5 bar) towards 1 mM Na2SO4 after soaking in water for 680 h. An increase in the transmembrane pressure to 20 bar resulted in an increase in the rejection towards the 1 mM Na2SO4 solution to 96.3%, and an increase in the permeance to 3.7 L·m-2·h-1·bar-1. The proposed strategy in varying charge repulsion is beneficial to the future development of GO-derived nanofiltration ceramic membranes.

Elucidating the role of interlayer structure in the permeance-selectivity trade-off of ceramic nanofiltration membrane

Reasonable design of a rational interlayer in an asymmetric ceramic nanofiltration (NF) membrane facilitates water transport as well as solute retention. Nevertheless, the inherent relationship between the microstructure of the interlayer and the permselectivity in ceramic NF membrane remains to be unclear. In this study, a quantitative model is developed to predict the influence of the factors (i.e., particle diameter and layer thickness) controlling the structure of interlayer on the permselectivity by integrating the cake filtrated theory and Donnan-Steric Pore model with the Dielectric Exclusion model. The simulations demonstrate that interlayer thickness dominates the solute rejection rather than particle diameter that constitutes the interlayer when an appropriate top-layer structure is applied. However, the enhancement of water permeance requires simultaneous regulation of the microstructures of both interlayer and top layer. For negatively charged ceramic NF membranes, the comprehensive effect of diffusion, convection, and electro-migration is the transport mechanism of positively charged counter-ion (i.e., Na+), whereas the transport of negatively charged co-ion (i.e., SO42-) is merely dominated by diffusion. This study thereby elucidates the role of the interlayer in terms of improving the permeance-selectivity trade-off relationship, which is of great significance to the future development of a high-performance ceramic NF membrane.

Studies in nanofiltration of dyes industry effluent

ABSTRACT A large number of chemicals are being produced in the industries, which resulted in accumulation in the effluent stream. The impact of these effluents on the environment is very adverse, if it released directly without treatment. Nowadays, the treatment of the effluent before discharge is very important due to strict norms imposed by various government agencies. In our study, the effluent from a local effluent treatment plant (effluent from dyes factory) was procured and treated with hydrophilic polymeric and ceramic nanofiltration membranes. The membrane characterisation was done based on flux, permeability, flux recovery ratio, and flux decline ratio. The effluent received from ETP and treated effluent was characterised in terms of pH, total dissolved solids (TDS), Chemical Oxygen Demand (COD), Conductivity, Turbidity, and Osmolality. From our experimental study, more encouraging results were obtained. More than 50% COD reduction was observed in the process. The membrane flux was recovered by the physical (by using backwashing) and chemical process (by using sodium hypochlorite solution). The different range was used for optimising the appropriate process for recovery of membrane flux. About 95% membrane flux was recovered by physical process on both ceramic and polymeric membranes.

Brackish water treatment by Ceramic TiO2 Low-Pressure Nanofiltration Membranes

&lt;p&gt;The application of ceramic Nanofiltration (NF) membrane in brackish water treatment is increasing due to strict water quality standards. Ceramic NF is a widely used membrane process and has replaced reverse osmosis (RO) membranes in many applications due to lower energy consumption and higher flux rates. This work aims to study the separation performance of tubular ceramic TiO2 Nanofiltration membrane at low-pressure (2 bar) for single and tertiary salt mixture separation. The results showed that the rejection of ions is ordered as follows: R (Cl1-) ion size &amp;gt; R calcium (Ca2+) ion size &amp;gt; R sodium (Na1+) ion size &amp;gt; R magnesium (Mg2+) ion size. Moreover, the highest Cl1- rejection was about 46%, the highest Ca2+ and Mg2+ rejection was about 44%, and the highest Na1+ rejection was about 37%. The pure water flux through the investigated ceramic NF membrane for distilled water was calculated to be 5.29 x 10-7 m3 s-1 m-2 bar-1, and this flux was dropped down for the salt mixture feed to 2.56 x 10-7 m3 s-1 m-2 bar-1 due to the presence of salt particles in the feed.&lt;/p&gt;&#x0D;

Recovery of dyes and salts from highly concentrated (dye and salt) mixed water using nano-filtration ceramic membranes

In this study, a higher concentration of (reactive dyestuff and salt) mixed water was used to verify the feasibility of separation by membrane techniques. The commercial nano filtration ceramic membrane (MWCO 200 Da) has been used in cross flow mode for separation of dyes and salts from highly concentrated mixed water solution. NF ceramic membrane presents good permeability (pure water flux 54.15 Lm−2 h−1, TMP 8 bar), 8% dye rejection and reduced salt rejection of NaCl (<8%) and Na2SO4 (<25%). Consequently, the operation parameters (TMP, temperature) and solution environment (solution pH, salt concentration and dye concentration) have been intensively evaluated for separation efficiency in the NF ceramic membrane process. Significantly, the NF ceramic membrane has performed less rejection to chloride ions than sulphate ions due to the Donnan effect. Solution pH, concentration of salt and dye concentration have shown significant effects on ceramic membrane separation performance. In addition, pollutant removals were achieved with noteworthy values for the chemical oxygen demand for permeate solution also color difference between concentrate and permeate. In conclusion, the strong rejection of dyes by the NF ceramic membranes proves that it can be suitable alternatives for textile wastewater treatment process.

Novel TiO2/GO-Al2O3 Hollow Fiber Nanofiltration Membrane for Desalination and Lignin Recovery.

Due to its greater physical–chemical stability, ceramic nanofiltration (NF) membranes were used in a number of industrial applications. In this study, a novel NF membrane was prepared by co-depositing a titanium dioxide (TiO2) and graphene oxide (GO) composite layer directly onto a porous α-Al2O3 hollow fiber (HF) support. An 8 µm-thick TiO2/GO layer was deposited to the surface of α-Al2O3 HF support by vacuum deposition method to produce advanced TiO2/GO-Al2O3 HF NF membrane. Scanning electron microscope (SEM) micrographs, energy dispersive spectrometer (EDS), X-ray powder diffraction (XRD), thermogravimetric analyzer (TGA), porosity, 3-point bending strength, zeta potential analysis, and hydrophilic properties by water contact angle are used for TiO2/GO-Al2O3 HF NF membrane characterization. The results show that the developed membrane’s MWCO ranged from 600 to 800 Da. The water flux, rejection of lignin, and sodium ions were 5.6 L/m2 h·bar, ~92.1%, and ~5.5%, respectively. In a five-day NF process, the TiO2/GO-Al2O3 HF NF membrane exhibits good lignin permeation stability of about 14.5 L/m2 h.

Ceramic nanofiltration membranes for efficient fouling mitigation through periodic electrolysis

Ceramic membranes are gaining importance in several mainstream membrane applications. Their high chemical and thermal resistance stability make them ideal candidates for oil/water separation, dye rejections, in dairy production, catalyst recovery and in treating a variety of wastewater effluents. Although ceramic microfiltration and ultrafiltration membranes are a predominant research area, there is still limited research on ceramic nanofiltration membranes, especially on controlling its fouling propensity. High flux values in such membranes can cause rapid fouling which lead to a compromise in membrane performance. In this work, we have modified commercial ceramic TiO2 NF membrane by coating it with titanium through an e-beam deposition process. Coating with titanium did not bring about any change in the inherent membrane properties such as its thermal resistance, structure and hydrophilicity. The superhydrophilic membrane showed good electrical conductivity, which enabled us to test the membrane for its self-cleaning ability through periodic electrolysis. Sodium alginate, yeast, humic acid and their mixtures were used as model foulants. A cross-flow filtration setup was used where the membrane acted as a cathode and a potential of 2–4.5 V was applied periodically depending upon the type of foulant. Without membrane cleaning, a sharp decline in flux to even till 10 % of its original value was noticed during some filtration tests. However, a high flux recovery from 88 to 98 % was achieved when the membrane was subjected to intermittent cleaning. The Ti-coated NF ceramic membrane showed efficient surface cleaning. The generation of hydrogen bubbles helped in sweeping away the cake layer formed as a result of concentration polarization. These electro-ceramic NF membranes allow us to address critical problems associated with such pressure driven processes where biofouling is a major problem.

Functionalized boron nitride ceramic nanofiltration membranes for semiconductor wastewater treatment

Boron nitride (BN) nanomaterials were used to enhance the separation performance of membranes due to their ability to create more nanochannels with excellent chemical stability. Two different functionalization methods, including strong acid oxidation and a tannic acid (TA)-assisted exfoliation process, were explored to introduce hydroxyl groups on BN surfaces. We also propose a novel method for the fabrication of ceramic nanofiltration (NF) membranes with optimal functionalized BN loadings on ceramic ultrafiltration (UF) membrane substrates. The functionalized BN-coated ceramic NF membrane exhibited a promising separation performance for both particulate and organic contaminants by modifying the surface chemistry of the ceramic membrane and reducing membrane pores by adding nanochannels. Compared to the performance of the ceramic UF membrane alone, filtering ceramic UF membrane permeate through the functionalized BN-coated ceramic NF membrane increased an additional rejection of 20.4% for dissolved silica and 59.8% for humic acid, respectively. Collectively, the results provide a basis for the optimization of membrane-based semiconductor wastewater treatment by creating a hybrid of the ceramic UF and NF membrane processes. In turn, our findings not only facilitate the achievement of national regulatory standards for wastewater discharge but also provide crucial insights into the transport dynamics of particulate and organic contaminants.