Stable Permeance Research Articles

Nacre-inspired graphene oxide/polyethyleneimine-based ultra-thin heterogeneous superwetting membrane for highly stable separation of oil-in-water emulsions

Since the massive discharge of oily wastewater seriously affects both humans and natural development, the performance of conventional membrane materials in terms of interfacial stability and antifouling in the treatment of surfactant-containing emulsified oily wastewater is a major challenge. In this work, a novel nacre-inspired graphene oxide/polyethyleneimine-based ultra-thin chemically heterogeneous superwetting membrane was fabricated through vacuum-assisted self-assembly and post-modification methods for oil-in-water emulsion separation. The nacre-inspired heterogeneous membrane exhibited superhydrophilicity, underwater superoleophobicity (underwater oil contact angle was 157.7°), excellent crude oil adhesion resistance, high acid/alkaline stability, outstanding salt resistance, and good mechanical properties (Young’s modulus 1391.7 MPa). The heterogeneous membranes showed separation efficiencies of more than 99.9 % for a range of oil-in-water emulsions. The high-value membranes could achieve the permeances of 917–1256 L m−2h−1 bar−1 for pure water and 339.7–577 L m−2h−1 bar−1 for emulsion through a dead-end filter device, with the optimal long-term stable permeance only decreasing by 30.0 % compared to the initial value. After six test cycles, the membrane’s antifouling and self-cleaning properties were enhanced by constructing heterogeneous superwetting properties, and the flux recovery rate remained at 96.5 %. All of these results indicated that this method provides new ideas for the design and fabrication of highly stable and antifouling membrane materials.

From single tube to multi-channel configuration: Constructing nanofiltration membranes with superior adhesion strength on the ceramic support by interfacial polymerization

Ceramic membranes with multi-channel configurations exhibit superior mechanical strength, high packing density, and high separation efficiency, making them more suitable for industrial applications than single tube and hollow fiber membranes. However, the preparation of thin-film composite (TFC) membranes on multi-channel ceramic supports remains a challenge because of the poor compatibility between organic and inorganic materials and their special configuration. In this study, nanofiltration membranes with a stabilized structure supported by 19-channel ceramic membranes were successfully prepared with improved adhesion strength and dynamic interfacial polymerization. TFC membranes with different channels exhibited uniform microstructure and stable performance. Specifically, polyethyleneimine, which served as a polymerization reactant, can be tightly wound on the surface of ceramic membranes via hydrogen bonding and van der Waals forces during interfacial polymerization. Owing to the enhanced cross-linked network interactions between the support and separation layers, the adhesion strength was significantly improved. Consequently, the optimized membranes maintained excellent rejection to MgCl2 of ∼94 % after the back-flush test under the pressure of 4 bar. Additionally, the multi-channel TFC membranes exhibited stable performance, with a pure water permeance of ∼14.9 LMH/bar and a molecular weight cut-off of 450 Da. When filtering sunset yellow for 10 h, the prepared membranes exhibited stable permeance and excellent rejection performance.

Construction of asymmetric ceramic membranes with identical source interlayer on fly ash support by dip-coating

As a highly efficient separation technology, ceramic membranes have been widely applied. The use of fly ash to prepare low-cost ceramic membranes has garnered significant attention in recent years. However, challenges remain in the preparation of asymmetric ceramic membranes with high performance. This study presents an efficient approach to fabricating asymmetric ceramic membranes with an identical source interlayer on fly ash supports using the dip-coating method. The alumina selective layer was co-sintered with the optimized interlayer at 1000°C. The average pore size of the asymmetric ceramic microfiltration membrane was approximately 120 nm, and the pure water permeance reached 870 L·m−2·h−1·bar−1. The ceramic microfiltration membrane demonstrated high efficiency in separating oil-in-water emulsions, achieving a stable permeance of 130 L·m−2·h−1·bar−1 and a TOC removal rate above 99 %. This work provides an efficient and effective construction method for producing fly ash-based ceramic membranes with high performance.

Influence of initial powders morphology on structural-dimensional characteristics of porous ceramic materials based on SiC/MgO–SiO2

Synthesis of porous ceramic materials based on fine SiC with sintering silicon oxide and magnesia binders at T = 800–1300 °C is considered. Special attention is paid to the influence of the shape and morphology of the initial powder particles on structural parameters and characteristics of porous ceramic materials. The SiC membranes sintered at 1000–1300 °C had average pore sizes of 0.5–1 μm, open porosity - up to 50 %, bending strength - up to 48.5 MPa and high water permeance - up to 7890 l⋅m−2⋅h−1⋅bar−1. The established filtration efficiency was ∼99 % in the case of screening out model particles of D50 = 0.5 μm in size with maintaining stable permeance and physico-mechanical characteristics after multiple filtration-regeneration cycles.Comprehension of the initial powders morphology impact on the synthesized porous ceramics parameters makes it possible to forecast and ensure the preset structural, dimensional and physico-mechanical parameters of the materials under study properly. This work can be used for practical low-cost production of highly efficient SiC membranes for micro- and ultrafiltration processes, as well as base for catalysts.

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.

Superhydrophilic fluorinated heterogeneous membranes with boosting antifouling property and high stable permeance for efficient emulsion separation

It is yet a query that whether chemically heterogeneous superwetting surface is able to enhance the permeability and anti-fouling capability of membrane contemporaneously, heretofore which is lacking and well worth creating. Here, we propose a bio-adhesion coupled with self-assembly strategy, to construct superhydrophilic fluorinated heterogeneous membranes, through in-situ biomimetic adhesion of the hydrophilic polyphenol-silane coating (TAT) on the porous PVDF membrane, as a secondary reaction platform, and subsequently self-assembly of amphoteric fluorocarbon surfactant (FS-50). Unsurprisingly, we find that introducing FS-50 not only significantly strengthens the permeability, but also improves the anti-fouling self-cleaning, thanks to the formation of robust hydration layer and slippery micro-domains with low friction, to realize the dual anti-fouling effects of pollution resistance and release. The champion PVDF/TAT/FS-2.0 % composite membrane exhibits superhydrophilic and underwater superoleophobic (oil contact angle above 162.3°) property with very low oil-adhesion. This composite membrane possesses an ultrahigh water permeance of 29214.6 L m−2 h−1 bar−1, which is 2.8 times larger than that of pristine PVDF membrane. The PVDF/TAT/FS-2.0 % composite membrane presents the high separation efficiencies (above 99.5 %) for various surfactant-stabilized oil-in-water emulsions and high permeances of 3193.2–4212.3 L m−2 h−1 bar−1. Especially, the membrane at continuous operation for 1.0 h can reach a high stable permeance of 2505.1 L m−2 h−1 bar−1. Moreover, this composite membrane shows strong chemical stability and robustness. This research answers the initial question, and provides the insight for further design and production of chemically heterogeneous superwetting membranes with high permeability, selectivity and antifouling ability.

Chitosan-modified fly-ash/kaolin ceramic membrane for enhancing FOG-water separation performance

Ceramic membranes with efficient construction can save costs and simplify the wastewater treatment process. The price of raw materials and the amount of energy used during the sintering process are the two key factors that affect the final cost of ceramic membranes. This work used kaolin and fly ash recovered from power plants as the support membrane and chitosan as selective layer of composite ceramic membranes. Rigid alumina particles were added to the supports to bring them into alignment with the sintering temperature of the fly-ash/kaolin support. Additionally, the chitosan layer coating increased the supports' bending strength. By simple surface coating, chitosan with different molecular weights was spread over the fly-ash/kaolin supports. The membranes' average pore size radius and porosity were 20 nm and 49%, respectively. The oil removal rate was over 99.8% and the stable permeance was close to 20.5 Lm2h1 when treating oil-water emulsions with 400 mg/L oil content. This is most likely because of the super-hydrophilic performance of kaolin and the electrostatic repulsion between the membrane and oil droplets. The fabricated membranes also demonstrated high antifouling performance by enhancing FRR up to 88% and reduced the reversible fouling ratio. This study suggests that modified membrane has great potential for practical application in oily wastewater treatment.

Chiral gold nanoparticles/graphene oxide membranes with ultrahigh and stable permeance for sieving and enantioseparation

In accurately balancing membrane permeability and separation coefficient, effectively preventing membrane collapse in separation process is the core to improve the efficiency of membrane separation for two-dimensional materials. Here, we used L-cysteine (L-Cys) functionalized gold nanoparticles as scaffolds and spacers and fabricated a multi-effect separation membrane with GO nanosheets. The as-prepared membrane performed the following as a separation membrane: (1) As a robust spacer, the gold nanoparticles, prevented the collapse of the GO sheet and thus the membrane showed stability; (2) The existence of amphiphilic L-cysteine enabled the possibility of regulating the GO sheets layer spacing between 16.9 and 17.8 Å by pH, which achieves controllable ultrahigh permeance for size sieving. The maximum permeation rate of the membrane can reach 216.6 L m−2 h−1 bar−1, which is much greater than that of pure GO membrane; (3) Further, we demonstrate the following properties of the as-prepared membranes embedded with amphiphilic chiral gold nanoparticles for the enantiomer separation. The membrane has high enantioselectivity for Pen racemates, and its chiral separation factor and permeation rate can reach 1.83 and 21.7 L m−2 h−1 bar−1, respectively.

Design of hybrid g-C3N4/GO/MCE photocatalytic membranes with enhanced separation performance under visible-light irradiation

Photocatalytic membranes with concurrent catalytic oxidation and separating functions possess promising potentials for the degradation of organic pollutants in wastewater treatment. Herein, we designed a hybrid photocatalytic membrane (viz., g-C3N4/GO/MCE) by vacuum-filtration-assisted assembling method, consisting of graphitic carbon nitride (g-C3N4) nanosheets as a top layer, graphene oxide (GO) nanosheets as an interlayer, and commercial mixed cellulose ester (MCE) as a substrate layer. The microstructures, chemical compositions, and physicochemical properties of the designed g-C3N4/GO/MCE membranes were systematically characterized by a series of characterization techniques. Particularly, photocatalysis-filtration reactor cells were designed for the evaluation of the simultaneous separation and photocatalytic degradation performance in a single unit using both organic dyes and antibiotics as modeling pollutants in wastewater. Four parameters were adopted to represent the integrated photocatalysis-filtration performance of our designed photocatalytic membranes, including permeance (P), rejection (R’, filtration alone), removal (R, combined photocatalysis-filtration under light-irradiation), and degradation rate (D). The hybrid membranes showed superior permeance and solute removal under visible-light irradiation (300 W, λ > 420 nm), in which the permeance was 20% higher than that of no-irradiation conditions. In addition, 10 consecutive cycling tests and light-on/off cycles of the as-prepared g-C3N4/GO/MCE membrane toward RhB showed quite stable permeance in the range of 268.9 to 352.9 L h−1 m−2 bar−1, and the removal was maintained in the range of 88.4% to 95.4%, indicating excellent long-term stability. Remarkably, it also exhibited good removal performance of antibiotics (e.g., ofloxacin, norfloxacin, sulfamethoxazole, erythromycin, and roxithromycin). Accordingly, the designed hybrid g-C3N4/GO/MCE photocatalytic membranes with excellent photocatalytic activity and photocatalysis-filtration performance are promising for wastewater treatment and water purification applications.

Fabrication of Organic Solvent Nanofiltration Membrane through Interfacial Polymerization Using N-Phenylthioure as Monomer for Dimethyl Sulfoxide Recovery

To recover dimethyl sulfoxide, an organic solvent nanofiltration membrane is prepared via the interfacial polymerization method. N-Phenylthiourea (NP)is applied as a water-soluble monomer, reacted with trimesoyl chloride (TMC) on the polyetherimide substrate crosslinked by ethylenediamine. The results of attenuated total reflectance-fourier transform infrared spectroscopy and X-ray electron spectroscopy confirm that N-Phenylthiourea reacts with TMC. The membrane morphology is investigated through atomic force microscopy and scanning electronic microscopy, respectively. The resultant optimized TFC membranes NF-1NP exhibited stable permeance of about 4.3 L m−2 h−1 bar-1 and rejection of 97% for crystal violet (407.98 g mol−1) during a 36 h continuous separation operation. It was also found that the NF-1NP membrane has the highest rejection rate in dimethyl sulfoxide (DMSO), and the rejection rates in methanol, acetone, tetrahydrofuran, ethyl acetate and dimethylacetamide(DMAc) are 51%, 84%, 94%, 96% and 92% respectively. The maximum flux in the methanol system is 11 L m−2 h−1 bar−1, while that in acetone, tetrahydrofuran, ethyl acetate and DMAc is 4.3 L m−2 h−1 bar−1, 6.3 L m−2 h−1 bar−1, 3.2 L m−2 h−1 bar−1, 4.9 L m−2 h−1 bar−1 and 2.1 L m−2 h−1 bar−1, respectively. It was also found that the membrane prepared by N-Phenylthiourea containing aromatic groups has lower mobility and stronger solvent resistance than that of by thiosemicarbazide.

Binary nanofibrous membranes with independent oil/water transport channels for durable emulsion separation

Oil fouling threatens the stability of water permeability for oil-water separation membrane. Homogeneous hydrophilic surface modification provided an opportunity to prevent oil pollution, but failed to maintain stable water traverse due to oil accumulation. Here we report a binary nanofibrous membrane (BNM) through co-electrospinning technique and Michael addition reaction, where hydrophilic polyacrylonitile (mPAN) and hydrophobic poly (vinylidene fluoride) (mPVDF) nanofibers with certain ratio constructed independent water/oil transport channels respectively. The fabricated binary nanofibrous membrane provides stable permeance and high separation efficiency (>99.5%) for viscous oily emulsions in continuous cross-flow filtration. The oil droplets transport experienced deposition, migration, coalescence and removal to significantly alleviate fouling. The binary nanofibrous membrane with heterogenous wetting property provides durable permeation and separation efficiency for durable emulsion separation, which sheds light on a new approach for the development of ideal oil/water separation membranes.

Construction of ZrO2-CeO2 composite UF membranes for effective PVA recovery from desizing wastewater

Ceramic ultrafiltration membranes play an important role for the PVA recovery from desizing wastewater. In this study, an integrated and thin (approximately 300 nm) ZrO2-CeO2 composite UF membrane was constructed, with a MWCO of 16 kDa and a water permeance of 116 L·m−2·h−1·bar−1. Nano ZrO2 particles were introduced to optimize the particle size distribution of the CeO2 dispersion, therefore improve its compatibility with the intermediate layer. The membrane also exhibited outstanding chemical stability in both acid (pH = 1) and alkali (pH = 14) solutions. In addition, the membrane exhibited excellent PVA separation performance under harsh conditions (operation temperature = 80 °C, and the solution pH = 13), with a nearly 100 % recovery rate of PVA and a stable permeance of 67 L·m−2·h−1·bar−1. Subsequently, the membrane showed outstanding efficiency for chemical cleaning, with the flux recovery ratio reaching 95.1 % under optimized cleaning conditions. Meanwhile, the pore structure and integrity of the membrane layer maintained stable during the whole process. Overall, this study provides a high-performance UF membrane from new material, which exhibits great potential for PVA recovery from desizing wastewater.

Construction of high-performance Ce-doped TiO2 tight UF membranes for protein separation

The membrane structure and properties have a significant influence on its anti-fouling performance during the separation process. In this study, Ce was introduced to inhibit the phase transformation of TiO2 to obtain a tight ultrafiltration (UF) membrane with a more uniform pore size, a more integrated membrane layer as well as to strengthen the membrane surface charge to provide superior anti-fouling performance for the membrane during protein separation. Single anatase phase of the material proves that the introduction of Ce effectively inhibited the phase transformation of TiO2 and prevented the occurrence of cracks. The prepared Ce-doped TiO2 membrane exhibited excellent performance, with a membrane thickness of 700 nm, water permeance of 175 L·m−2·h−1·bar−1 and molecular weight cut-off of approximately 18 kDa. Additionally, it showed excellent BSA separation performance, as the stable permeance and rejection rate could be maintained at 120 L·m−2·h−1·bar−1 and 100 %, respectively. Meanwhile, Ce-doped TiO2 membrane showed superior anti-fouling performance compared to pure TiO2 membrane due to its strengthened surface charge and uniform pore size, with the J/J0 maintained a value of 0.69. Based on the obtained results, the Ce-doped TiO2 membranes prepared in this study exhibit good potential for protein separation.

Robust PVDF/PSF hollow-fiber membranes modified with inorganic TiO2 particles for enhanced oil-water separation

HPollow-fiber (HF) membranes with high tensile strength and water permeance and composed of poly(vinylidene fluoride) (PVDF) and polysulfone (PSF) were prepared using phase inversion to enhance separation of oil-in-water (O/W) emulsions. Hydrophilic inorganic particles of titanium dioxide (TiO2) were coated onto PVDF/PSF membrane surfaces with the aid of Pluronic and polydopamine (PDA). The pore structure, hydrophilic properties, and tensile strength of HF membranes can be finely tuned by varying the TiO2 concentration in the coating solution. Pluronic or PDA-assisted TiO2 coating enhanced the adhesion between TiO2 and membrane surface as revealed by X-ray photoelectron spectroscopy and stability tests. These HF membranes achieved enhanced O/W emulsion separation in a crossflow filtration process. A Pluronic-stabilized HF membrane achieved a higher rejection rate (above 99.5%) and stable permeance (∼650 Lm-2 h−1 bar−1) in a micro-sized emulsion (soybeans-in-water) at a TiO2 concentration of 0.75 wt% compared with a pristine HF membrane. Meanwhile, PDA-stabilized HF membranes exhibited 99% rejection and stable permeance of 410 Lm-2 h−1 bar−1 toward nano-sized emulsion (hexane-in-water) when the PDA@TiO2 composite concentration was 0.75 wt%, while a pristine HF membrane achieved a rejection rate of only ∼90% and a permeance <200 Lm-2 h−1 bar−1. The enhanced hydrophilicity and decorated pore structure produced by hydrophilic TiO2 with the aid of polymers (Pluronic or PDA) enhanced the separation performance of both micro- and nano-sized O/W emulsions through HF membranes.

Fabrication of a dual-layer ceramic mesoporous membrane with high flux via a co-sintering process

The application of ceramic mesoporous membranes is mainly limited by the trade-off between separation performance and fabrication cost. Here, a co-sintering technique is employed to fabricate ZrO 2 dual-layer ceramic mesoporous membranes with high separation precision and water permeance. Based on a coarse ceramic substrate, dual layers that could effectively decrease the fabrication cost and time were co-sintered. By doping zirconia nanoparticles in the sublayer, the sintering temperature could be decreased, and a high bonding strength was achieved between the dual layers. It is demonstrated that the permeance can be finely tuned by controlling the thickness of the sublayer. The resulting membrane exhibited a high water permeance of 280 L m −2 h −1 bar −1 and a molecular weight cut-off of 40–50 kDa. The zirconia mesoporous membrane was employed for sol separation, affording a 100% rejection rate toward SiO 2 nanoparticles. The cost-effective ZrO 2 mesoporous membrane exhibits significant application potential for the separation of industrial SiO 2 sols. • A dual-layer ceramic mesoporous membrane was prepared by the co-sintering process. • ZrO 2 nanoparticles were doped in the sublayer to increase the bonding strength of the membrane. • The resulting mesoporous membrane exhibited a 100% retention rate and highly stable permeance for SiO 2 sol separation.

Solar-catalytic membranes constructed by graphene oxide and prussian blue@covalent triazine framework “active mega cubes” for ultrafast water transport

Two-dimensional membranes are drawing utmost interest owing to outstanding molecular/ion sieving. However, membrane fouling literally restricts stable permselectivity during continuous filtration. Here we first report ultrafast water transport and solar-cleaning graphene oxide (GO) membranes, which integrate with Prussian Blue@Covalent Triazine Framework (PB@CTF) as “active mega cubes”. The intercalated PB@CTF expands the boundary between GO and mega cube crystal face and endows the membrane with photothermal intensified photocatalytic activity. The membrane exhibited a high and stable permeance for organic molecules (>170 L m −2 h −1 bar −1 , >95% rejection to dyes and antibiotics, ∼40-fold higher than GO membrane) during continuous flow through filtration under 1-sun illumination. The heterogeneous catalytic kinetics confirm the photothermal intensified photocatalytic contribution to foulants degradation. The apparent reaction rate constant ( k ) of GO/PB@CTF-3 membrane reaches 0.140 min −1 , 29-fold higher than GO membrane. The work provides a practical solution to maintaining the stable permselectivity and solar cleaning performances of GO membranes by “active mega cubes”. • PB@CTF “active mega cubes” are first introduced to GO membranes. • The membrane shows ultrafast water/molecules transport and solar-cleaning properties. • “Mega cubes” provide straightforward pathways for fast water transport. • “Active cubes” offer photothermal intensified photocatalytic degradation. • The membrane achieves high permeance and molecules removal continuously.

Liquid-Infused Membranes Exhibit Stable Flux and Fouling Resistance.

Antifouling membranes that offer excellent operational lifetimes are critical technologies needed to meet the growing demand for clean water. In this study, we demonstrate antifouling membranes featuring an ultrathin oil layer that stayed immobilized on the surface and in the pore walls of poly(vinylidene fluoride) membranes for multiple cycles of operation at industrially relevant transmembrane pressures. An optimized quantity of a commercial Krytox oil with either a low (K103) or a high viscosity (K107) was infused onto the active surface and into the pores of membranes with a 0.45 μm pore size. The presence of the oil layer was qualitatively confirmed using crystal violet staining and variable pressure scanning electron microscopy. Using a dead-end stirred cell, a consistent pure water permeance value of 3000 L m-2 h-1 bar-1 was achieved for the K103 liquid-infused membranes for at least 10 operation cycles, which was expectedly lower than the permeance of bare control membranes (∼16 000 L m-2 h-1 bar-1), suggesting that a stable oil layer was formed on all membrane-active sites. To quantify if oil was lost during membrane operation, extensive thermogravimetric analysis was conducted on both the as-prepared and used membranes. When challenged with the microorganism, Escherichia coli K12, the liquid-infused membranes statistically reduced microbial attachment by ∼50% versus the control membranes. For the first time, we have demonstrated that by forming an immobilized, robust, and stable oil-coated membrane, we can generate high-performance membranes with stable permeance values that can be operated at relevant transmembrane pressures and provide long-lasting antifouling properties.

Preparation and characterization of CeO2@high silica ZSM-5 inorganic-organic hybrid polyamide nanofiltration membrane

Nanofiltration with high stable permeance is of great significance for wastewater treatment. Herein, we reported the novel polyamide thin-film composite (PA TFC) nanofiltration membranes prepared for the first time by blending nanometer cerium doped high silica ZSM-5 zeolites (CeO2@HSZSM-5, CHZ) in the aqueous phase followed by the classic interfacial polycondensation. The structural morphology of these membranes and their performance had been characterized. SEM and XPS characterizations clearly revealed the presence of inorganic CHZ in the PA layer. The results also showed that the CHZ-integrated inorganic-organic PA TFC membranes with a higher fraction of CHZ had a thinner PA active layer (28.3 ± 3.6 nm) and slightly enlarged pore size with lower crosslinking degree. The optimized membranes exhibited 1.65-folds pure water permeability of the traditional membrane, 20.3 L/(m2.h.bar) with comparable Na2SO4 and MgSO4 rejection of 95.8% and 91.1%, respectively. The rejection of dyes stayed stable above 96.0% with boosted permeance, and the membrane almost completely removed CR and RB as well as natural organic matters. The composite membrane also sustained superior stability and excellent antifouling performance. The as-prepared CHZ-integrated PA TFC membranes with regulatable structural morphology and superior separation properties enables the potential practical application in wastewater treatment.

Effective and efficient fabrication of high-flux tight ZrO2 ultrafiltration membranes using a nanocrystalline precursor

The use of membrane technology in protein purification is limited by the subsequent membrane fouling. In this study, tight ZrO2 ultrafiltration (UF) membranes with narrow pore size distributions, which effectively reduced the pollution of ceramic membranes, were prepared using a nanocrystalline precursor. The pore size distribution and permeance of the fabricated membranes were controlled by adjusting the sintering temperature. The molecular weight cut-off of the membranes increased from 25 kDa (7 nm) to 66 kDa (10.9 nm) as the sintering temperature increased from 400 °C to 800 °C, while their permeance increased from 135 to 225 L m−2 h−1 bar−1. The ZrO2 UF membrane sintered at the range of 400–600 °C was tested for the BSA molecules solution separation, which showed almost 100% of BSA molecules retention and demonstrated a stable permeance of approximately 80–95 L m−2·h−1 bar−1. Moreover, the sintering temperature of 500 °C was identified as the optimal temperature in terms of the removal of organic additives and energy consumption. The obtained results indicate that the prepared ZrO2 UF membranes can be potentially used for protein separation.

One-step engineering of low-cost kaolin/fly ash ceramic membranes for efficient separation of oil-water emulsions

Efficient construction of ceramic membranes can decrease the cost and ease the process of wastewater treatment. The total cost of ceramic membranes is mainly determined by the cost of raw materials and energy consumption during sintering process. In this work, fly ash particles recycled from electric plant and kaolin materials were respectively employed as the support and membrane layer of composite ceramic membranes. To match the sintering temperature of the kaolin material and fly ash support, rigid alumina particles were introduced into the supports (AFA supports). Also, the bending strength of the supports was improved when adding alumina particles. The kaolin/fly ash ceramic membrane was obtained by spraying the kaolin dispersion on the AFA supports and co-sintering. The mean pore diameter and water permeance of the membranes were 320 nm and 3650 Lm−2h−1 bar−1. When treating oil-water emulsions with oil content of 400 ppm, the oil removal rate was above 98.5% and the stable permeance was close to 530 Lm−2h−1 bar−1, likely due to the super-hydrophilic performance of kaolin and the electric repulsion between the membrane and oil droplets. The raw materials cost, sintering energy consumption, and fabrication time were successfully decreased. This work demonstrates the feasibility of low-cost ceramic membranes for efficient wastewater treatment in chemical industries.