Solvent Filtration Research Articles

Harnessing plastic waste for sustainable membrane filtration with trimodal structure through acid-catalyzed oxidation

Polyolefin waste is among the most generated yet least recycled. Despite its potential as a feedstock of superhydrophobic membranes for organic solvent filtration, it remains a challenge to achieve high selectivity and permeability for viscous oils. In this study, we valorized polyolefin waste into trimodal water filtration membranes through acid-catalyzed oxidation and a void inducer. This approach enabled the creation of membranes with exceptional wettability and strength, characterized by a combination of micropores, macrovoids (30–70 µm), and cavities (150–200 µm). The acid-catalyzed oxidation introduced oxygen moieties into the membrane structure, resulting in a reduced water contact angle, improved hydrophilicity, and increased permeability. The micropores facilitated capillary action, macrovoids enabled efficient water passage, and cavities acted as oil reservoirs, for optimal oil–water separation. Various membranes were synthesized using low-density and high-density polyethylene (PE), polypropylene (PP), and their blend. The obtained results were compared with commercial membranes, revealing a flow rate of 43 ml/min, a retention capacity of 261 mg, and an oil removal efficiency ranging from 84–94 %. Furthermore, the membranes exhibited recyclability, demonstrating stability over at least 10 cycles. This hybrid process transforms plastic waste into trimodal water filtration membranes, achieving a balance between superoleophilicity and hydrophilicity.

Recycling of homogenous catalyst using organic solvent filtration and electrochemical separation

Homogenous catalyst has great selectivity and kinetic advantages. However, it is quite difficult to recover because it has same phase as the reaction mixture, so their utilization is being limited. A popular method to recover the catalyst is organic solvent nanofiltration, which use the transmembrane pressure and the different composition of the solvents to achieve the catalyst recovery. In recent research, a new method-separation using electrochemistry had been discovered which seems to increase the recovery percentage. In this paper, both strategies with recent developments are summarized, and focused on how the accompanied components such as solvents, electrolytes and electrode usage will influence the catalyst recovery.

Recruitment of efferent lymph during infusion of 20% albumin.

Intravenous infusion of hyper-oncotic 20% albumin expands the plasma volume by approximately twice the infused volume. We investigated whether the recruited fluid stems from accelerated flow of efferent lymph, which would add protein to the plasma, or from reversed transcapillary solvent filtration, where the solvent is expected to be low in protein. We analyzed data from 27 intravenous infusions of 20% albumin (3mL/kg; approximately 200mL) over 30min given to 27 volunteers and patients. Twelve of the volunteers were also given a 5% solution and served as controls. The pattern of blood hemoglobin, colloid osmotic pressure, and the plasma concentrations of two immunoglobulins (IgG and IgM) were studied over 5h. A decrease of the difference between the plasma colloid osmotic pressure and plasma albumin occurred during the infusions and was almost four times greater for 5% albumin than for 20% albumin at 40min (P<0.0036), which indicates that non-albumin protein enriched the plasma when 20% was infused. Moreover, the difference between the infusion-derived dilution of the blood plasma based on hemoglobin and the two immunoglobulins amounted to -1.9% (-6 to +0.2) for 20% albumin and to -4.4% (25th-75th percentile range-8.5 to +0.2) during experiments with 5% albumin (P<0.001). This supports that the plasma was enriched by immunoglobulins, probably via the lymph, when 20% was infused. Between half and two-thirds of the extravascular fluid that was recruited during infusion of 20% albumin in humans consisted of protein-containing fluid consistent with efferent lymph.

Solvent transport model for polyamide nanofilm membranes based on accurate Hansen solubility parameters

Polyamide (PA) nanofilm membranes for solvent filtration are widely used in various industries. However, reliable models that can describe solvent transport in PA membranes have yet to be developed owing to measurement challenges associated with the highly irregular, ultrathin, and crosslinked PA structure which hampers the accurate estimation of solvent−membrane affinity. In this study, we determined the Hansen solubility parameters (HSPs) of crosslinked PA membranes by quantifying the swelling degrees of a molecular layer-by-layer-assembled, model PA nanofilm in various solvents via in-situ atomic force microscopy. The newly determined HSPs of the PA layer, in combination with free volume and Flory–Huggins solution theories, were incorporated into the solution-diffusion model. Our refined solution-diffusion model accurately predicted the permeance of 16 different solvents by faithfully capturing the characteristics of solvent−membrane affinity. Our study reveals practical and fundamental insights into solvent transport in PA membranes along with providing robust tools for characterizing nanofilm properties.

High performance in-situ tuned self-doped polyaniline (PANI) membranes for organic solvent (nano)filtration

Cross-linked polyaniline (PANI) membranes are attractive for organic solvent nanofiltration (OSN). However, inadequate tuneability to cover the full nanofiltration (NF) separation range, prolonged post-treatment cross-linking using hazardous organic chemicals and poor permeance limit their widespread application. This work introduces a new strategy to tune the transport properties of PANI membranes to suit the rejection spectrum of NF membranes without compromising permeance. Incorporating different molecular weight organic acids, metanilic acid (MA) and poly (2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA), facilitated cross-linking during polymer precipitation at different aqueous coagulation bath acidic strength using non-solvent induced phase separation (NIPS). Static ageing tests for PANI membranes immersed in tetrahydrofuran (THF) for 30 days showed no physical or chemical deterioration. All membranes were stable during long-term dynamic crossflow filtration tests over 250 h with sequential feed of methanol, acetonitrile and THF. THF permeance was 2.1–16.4 L m−2 h−1 bar−1 with apparent molecular weight cut off (MWCO) between 250 and 1000 g mol−1. PAMPSA doped membranes were successfully cross-linked but required wet annealing post-treatment to obtain membranes in NF range. The MA doped membranes surpassed the performance of cross-linked PANI membranes with glutaraldehyde (organic cross-linker) showing a 2.5 times higher permeance with better rejection. In comparison to commercial polyimide membranes, PANI membranes prepared in coagulation bath ≥0.5 M HCl(aq) were stable in N,N-dimethylformamide (DMF) whereas the former suffered complete damage. This work represents a simplified technique to in-situ optimise permselective properties of OSN self-doped PANI membranes for various applications in food, pharmaceutical and petrochemical industries.

Highly Selective and pH-Stable Reverse Osmosis Membranes Prepared via Layered Interfacial Polymerization.

Ultrathin and smooth polyamide (PA) reverse osmosis (RO) membranes have attracted significant interest due to their potential advantages of high permeance and low fouling propensity. Although a layered interfacial polymerization (LIP) technique aided by the insertion of a polyelectrolyte interlayer has proven effective in fabricating ultrathin and uniform membranes, the RO performance and pH stability of the fabricated LIP membrane remain inadequate. In this study, a poly(piperazineamide) (PIPA) layer prepared via interfacial polymerization (IP) was employed as an interlayer to overcome the limitations of the prototype LIP method. Similar to the control polyelectrolyte-interlayered LIP membrane, the PIPA-interlayered LIP (pLIP) membrane had a much thinner (~20 nm) and smoother selective layer than the membrane fabricated via conventional IP due to the highly surface-confined and uniform LIP reaction. The pLIP membrane also exhibited RO performance exceeding that of the control LIP and conventional IP-assembled membranes, by enabling denser monomer deposition and a more confined interfacial reaction. Importantly, the chemically crosslinked PIPA interlayer endowed the pLIP membrane with higher pH stability than the control polyelectrolyte interlayer. The proposed strategy enables the fabrication of high-performance and pH-stable PA membranes using hydrophilic supports, which can be applied to other separation processes, including osmosis-driven separation and organic solvent filtration.

Novel synthesis methods and applications of MXene-based nanomaterials (MBNs) for hazardous pollutants degradation: Future perspectives

MXenes are a quickly growing and extended group of two-dimensional (2D) substances that have earned unbelievable analysis credits for various application areas within different manufacturing areas. Due to novel essential architectural and physicochemical properties shows good properties, such as elevated exterior area, living adaptability, strong electrochemistry, and great hydrophilicity. Given the fast progress within the structure and synthesis of MBNs for water treatment, quick updates on this research field are required to remove toxic substances, such as production approaches and characterization methods for the advantages and constraints of MXenes for pollutant degradation. MXenes are determined as a proposed road toward atmosphere-clean-up machinery to identify and decrease a pattern of hazardous resistant pollutants from environmental forms. Here, in this review article, we have been focused on describing the overview, novel synthesis methods, and characteristics of the MXene-based nanomaterials (MBNs) in the field for removing hazardous contaminants from environmental conditions. In the last, the utilizations of MBNs in water sanitization, organic solvent filtration, antibiotics degradation, pesticide degradation, heavy metals degradation, ions removal, bacterial pathogens degradation, along with the conclusion, challenges, and prospects in this field, have been discussed.

Polybenzoxazines in fabrication of separation membranes: A review

• Polybenzoxazine (PBz) use in fabrication of high-performance membranes is reviewed. • PBz is a high thermal, chemical and physical resistance polymer. • Properties and synthesis methods of PBz is introduced and reviewed. • Different types of PBz-based membranes are reviewed. • PBz-based membranes are used in harsh, strong acidic conditions or solvent filtration. The demand on developing new materials for fabricating polymeric membranes is growing progressively in membrane science. Since, novel materials with high chemical, mechanical and thermal resistance are needed to improve membrane separation performance. Low thermal resistance of membrane materials restricts application of polymeric membranes in many industrial separation processes such as membrane distillation or gas separation. Polybenzoxazines (PBzs) could be promising alternatives to fabricate high performance membranes due to outstanding temperature, chemical and physical stability of the resulted membranes. The properties of PBz systems could be easily modified by altering monomers and synthesizing main, side and end chain PBz precursors. In this review, the properties and synthesis methods of PBz is introduced and different types of PBz-based membranes such as ion exchange, electrospun nanofiber, pervaporation, gas separation, solvent resistance and antifouling membranes are reviewed. Most of PBz-based membranes are used in high temperature, harsh, and strong acidic conditions or solvent filtration successfully, approving high performance of these membrane materials. Moreover, the presence of phenolic groups could inherently grant antifouling capacity to these membranes. In addition, the relationship between structure and property of PBZs membranes is surveyed. This review will be beneficial for designing and fabricating membranes from PBz with specific characteristics for applications in harsh conditions.

All-Polymeric Thin-Film Nanocomposite Membrane for Organic Solvent Nanofiltration

The fabrication of chemically stable and high-permeance polymeric membranes, compatible with both polar and nonpolar solvents, for use in solvent filtration is reported. Herein, poly(divinylbenzene...

Cross-Linked Polycarbonate Microfiltration Membranes with Improved Solvent Resistance.

In this study, we report a facile preparation of an organic solvent-resistant membrane through the formation of urethane bonds between polycarbonate and polyethyleneimine groups. The modified membrane was further cross-linked with 1,4-butanediol diglycidyl ether (BDG) to enhance its solvent resistance as well as its thermal and mechanical stability. The cross-linked polycarbonate membranes exhibited improved solvent resistance with various organic solvents, giving a maximum swelling degree of 6%. It also showed better mechanical and thermal stability, as well as excellent permeance and rejection performance. This study demonstrates BDG as an attractive cross-linker for polycarbonate microfiltration membranes to transform them toward organic solvent filtration applications.

Zeolite Composite Membranes with a Nanoporous Fluorinated Carbonaceous Sheath for Organic Solvent Filtration

Inorganic membranes for organic solvent nanofiltration (OSN) inherently rely on the chemical affinity of pores, in particular, hydrophobicity of the pores and pore functionalities, to reject small ...

Creation of highly stable porous polyacrylonitrile membranes using infrared heating

Highly stable porous membranes made of commercial polyacrylonitrile (PAN) were developed for high pressure application in aprotic solvents. The membranes prepared by NIPS method from the casting solution with PAN concentration of 15 or 18 wt% in DMSO demonstrated good mechanical stability towards the transmembrane pressure of 30 bar and MWCO of 22 and 14.5 kg/mol, respectively; whereas the lower polymer concentration (12 wt%) led to collapsing of porous structure based on SEM data. By adjustment of treatment time and temperature, it was shown that the porous PAN membranes became insoluble in aprotic solvents such as DMSO, DMF, DMAc, and NMP after 5 min of infrared heating at 170 °C. The analysis of the data obtained by SEM, liquid-liquid displacement porosimetry, solvent filtration, and MWCO revealed that such IR treatment did not noticeably change the membrane structure and properties originally formed during the membrane casting. Replacement of conventional heating reported in the literature by IR heating allowed to reduce the treatment time from 6 h at 250 °C down to 5 min at 170 °C (estimated energy saving by a factor of 6.5). The mechanism of the transformation of PAN into insoluble form was proposed based on the data of FTIR analysis. The hypothesized role of adsorbed water molecules in accelerating cross-linking of PAN upon the near-IR heating was considered and discussed. IR treated PAN membranes can be employed as porous supports for solvent resistant nanofiltration membranes or directly as ultrafiltration membranes for non-aqueous applications.

Fungal chitin-glucan nanopapers with heavy metal adsorption properties for ultrafiltration of organic solvents and water

Membranes and filters are essential devices, both in the laboratory for separation of media, solvent recovery, organic solvent and water filtration purposes, and in industrial scale applications, such as the removal of industrial pollutants, e.g. heavy metal ions, from water. Due to their solvent stability, biologically sourced and renewable membrane or filter materials, such as cellulose or chitin, provide a low-cost, sustainable alternative to synthetic materials for organic solvent filtration and water treatment. Here, we investigated the potential of fungal chitin nanopapers derived from A. bisporus (common white-button mushrooms) as ultrafiltration membranes for organic solvents and aqueous solutions and hybrid chitin-cellulose microfibril papers as high permeance adsorptive filters. Fungal chitin constitutes a renewable, easily isolated, and abundant alternative to crustacean chitin. It can be fashioned into solvent stable nanopapers with pore sizes of 10−12 nm, as determined by molecular weight cut-off and rejection of gold nanoparticles, that exhibit high organic solvent permeance, making them a valuable material for organic solvent filtration applications. Addition of cellulose fibres to produce chitin-cellulose hybrid papers extended membrane functionality to water treatment applications, with considerable static and dynamic copper ion adsorption capacities and high permeances that outperformed other biologically derived membranes, while being simpler to produce, naturally porous, and not requiring crosslinking. The simple nanopaper production process coupled with the remarkable filtration properties of the papers for both organic solvent filtration and water treatment applications designates them an environmentally benign alternative to traditional membrane and filter materials.

Organic solvent filtration by brush membranes: Permeability, selectivity and fouling correlate with degree of SET-LRP grafting

A novel surface modification technique for polyimide membranes, their characterization and organic solvent filtration performance is described. The process involves treating crosslinked polyimide support membranes with surface initiators followed by Single Electron Transfer - Living Radical Polymerization (SET-LRP) with three alkyl methacrylates. Proof of grafting is established using ATR-FTIR, XPS and FESEM. The degree of grafting (DG) and brush height were a function of monomer type and polymerization time and provide a unifying basis for correlating selectivity and permeability. The permeability of these composite membranes, evaluated with 6 organic solvents (alcohols), correlated with solvent properties and can be tailored with DG. Filtration performance was assessed by measuring the selectivity and fouling of the organic dye Rose Bengal (RB) in ethanol. The polarized wall concentration increased with DG, whereas the RB sieving coefficient decreased with DG. Flux decline during RB filtration was best described by pore blocking and by heterogeneous and Langmuir sorption models. These studies provide a basis for designing polymeric membranes comprising branched brush selective layers with defined microstructure not possible with the widely popular phase inversion process.

Critical flux of colloidal foulant in microfiltration: Effect of organic solvent

As membrane technology becomes more popular for separation and purification in the aqueous phase, the advantages have increasingly attracted attention for organic solvent filtration applications. However, although the knowledge base on the inevitable membrane fouling in water is rich by now, the understanding for organic solvents is limited. Accordingly, this study was targeted at providing insights on the fouling behavior of the same colloidal foulant (namely, silica) and microfiltration membrane (namely, Anopore) in four different solvents (namely, DI water, ethanol, hexane and formamide). The direct observation through the membrane (DOTM) technique was used to characterize critical flux (Jcrit), which affirmed the distinctly different values in the four solvents at various Reynolds numbers. The shear-induced diffusion model predicted well for water and formamide only, indicating the model has to be enhanced to account for solvent effects. To quantify the interfacial interactions, the Derjaguin-Landau-Verwey-Overbeek (DLVO) and extended (XDLVO) models were used. Both models agreed in that silica-membrane and silica-silica interactions were the most attractive in hexane, which underlies the immediate membrane fouling and extensive clumping, respectively. For the other three solvents, the relative DLVO interaction energies agreed with the relative Jcrit values at fixed Re, indicating the greater relevance of the DLVO (rather than XDLVO) model and Re (rather than crossflow velocity). Because the greatest silica-silica repulsion in ethanol was mis-predicted by both DLVO and XDLVO models, the solvation film effect was additionally harnessed to provide an explanation. The understanding gained from this study on membrane fouling in organic solvents are expected to be beneficial in the design and operation of such emerging membrane filtration systems.

Solvent Filtration Performance of Thin Film Composite Membranes based on Polyethersulfone Support

Solvent Filtration Performance of Thin Film Composite Membranes based on Polyethersulfone Support

Organic solvent supported fabrication of transparent free standing graphene oxide membranes

Free standing graphene oxide membranes (FSGOMs) were prepared by evaporation of GO-methanol/GO-water-methanol dispersions on silicon substrate and, subsequent delamination using 2-propanol or by mechanical exfoliation. SEM and XRD studies indicated the influence of methanol-water composition on morphological features and interlayer spacings of FSGOMs. Methanol provides superior surface coverage and fast drying conditions as compared to water-methanol and, surface morphology of FSGOMs can be tuned by providing sufficient duration for the settlement and stacking of GO sheets. Delamination of membranes is largely determined by dispersion composition, hydrophilicity of substrate and thickness of membrane. FSGOMs prepared in this work displayed considerable transmittance in visible region, mechanical flexibility and thermal stability of chemical composition up to 250 °C. These membranes are remarkably stable in 2-propanol, attributed to unimpeded permeation of propanol molecules through intra-layer spacings and introduction of fresh interactions. FSGOMs showed ~63% of methylene blue (MB) removal efficiency from MB-propanol solutions through multiple filtration cycles and the filtration ability may be ascribed to intra-layer entrapment of MB molecules through chemisorption at functional groups of GO. Present work provides quick, facile and economical method for damage-free FSGOM preparation, which has potential applications in the development of membranes for organic solvent filtration.

Preparation of PEEK Membranes with Excellent Stability Using Common Organic Solvents

Poly(ether ether ketone) (PEEK) is one of the most attractive polymers for organic solvent resistance applications because of its high thermal and organic solvent resistance. However, one of the main disadvantages is that PEEK has to be processed by using harsh solvents, such as methanesulfonic and sulfuric acid. Here, we report for the first time the preparation of PEEK membranes for organic solvent filtration by using common organic solvents. The preparation method consists of the conversion of PEEK into a soluble precursor, followed by dissolution in a mixture of tetrahydrofuran and N,N-dimethylacetamide. The resulting solution is used to obtain the membranes by phase inversion. In the second step, we convert the PEEK precursor to PEEK by treating the obtained membranes with an aqueous acid solution. The resulting PEEK membranes have good permeance and rejection, along with high stability in organic solvents and at high temperatures (up to 140 °C). This procedure opens many possibilities for processing PEEK into membranes by using common techniques to obtain flat sheet membranes or hollow fibers for a broad range of applications.

Versatile and High-Throughput Polyelectrolyte Complex Membranes via Phase Inversion.

High-flux filtration membranes constructed through scalable and sustainable methods are desirable for energy-efficient separations. Often, these criteria are difficult to be reconciled with one another. Polymeric membranes can provide high flux but frequently involve organic solvents in processing steps. Solubility of many polymeric membranes in organic media also restricts their implementation in solvent filtration. In the present work, we report a simple and high-throughput aqueous processing approach for polyelectrolyte complex (PEC) membranes with controllable porosity and stability in various aqueous and organic environments. PECs are materials composed of oppositely charged polymer chains that can form solids in aqueous environments, yet which can be dissolved in very specific salt solutions capable of breaking the interpolymer ion pairs. By exploiting the salt-induced dissolution and subsequent reformation of the complex, nano- to microporous films are rapidly synthesized which resemble membranes obtained through conventional solvent-phase inversion techniques. PECs remain stable in organic solvents because of the low dielectric constant of the environment, which enhances electrostatic interactions, making them suitable for a wide range of water and solvent filtration applications. Here, we elucidate how the polymer-phase behavior can be manipulated to exercise morphological control, test membrane performance for water and solvent filtration, and quantify the mechanical stability of PECs in relevant conditions.

Nanoparticle filtration through microporous ECTFE membrane in an alcoholic solution

Abstract Organic solvent filtration is an important industrial process. It is widely used in pharmaceutical manufacturing, chemical processing industry, semiconductor industry, auto assembly etc. Most of the particle filtration studies reported in open literature dealt with aqueous suspension medium. The current work has initiated a study of cross-flow solvent filtration behavior of microporous ethylene chlorotrifluoroethylene (ECTFE) membranes using 12 nm silica nanoparticles suspended in an aqueous solution containing 25% ethanol. In the constant pressure mode of operation of cross-flow microfiltration (MF), permeate samples were collected at different time intervals. The permeate particle size distribution (PSD) results for different experiments were identical. Particle agglomerates having less than 100 nm size can pass through the membrane; some fouling was observed. The governing fouling mechanisms for tests operated using 3.8 × 10−3 kg/m3 (3.8 ppm) at 6.9 × 103 Pag and 1.4 × 104 Pag were pore blocking. For tests conducted using 3.8 × 10−3 kg/m3 (3.8 ppm) at 27.6 × 103 Pag (4 psig) and 1.9 × 10−3 kg/m3 (1.9 ppm) at 6.9 × 103, 13.8 × 103 and 27.6 × 103 Pag (1, 2 and 4 psig), the mechanism was membrane resistance control. Less particles got embedded in membrane pores in experiments operated using suspensions with lower or higher particle concentrations with a higher transmembrane pressure. This is in good agreement with the values of the shear rate in the pore flow and scanning electron microscope images of the membrane after MF. In the dead-end mode of operation of solvent filtration using methanol, ethanol and 2-propanol, the permeate flux behavior follows Jmethanol > Jethanol > J2-propanol at all testing pressures. The values of permeance (kg/m2-s-Pa) determined from the slope of the linear plot of filtration flux vs. the applied pressure difference across the membrane, were 3.9 × 10−4, 2.3 × 10−4 and 3.0 × 10−5 for methanol, ethanol and 2-propanol, respectively. Further exploration was made on solvent sorption results reported earlier. The critical temperature of selected solvents shows a better correlation with solvent sorption rather than the solubility parameter.