Molecular Weight Cut-off Membrane Research Articles

Quality of Life of Dialysis Patients: Exploring the Influence of Membrane Hemocompatibility and Dialysis Practices on Psychosocial and Physical Symptoms

Hemodialysis (HD) is a life-sustaining membrane-based therapy that is essential for managing kidney failure. However, it can have significant physical and psychological effects on patients due to chronic or acute consequences related to membrane bioincompatibility. End-stage renal disease (ESRD) patients on hemodialysis have a high incidence of psychiatric illness, particularly depression and anxiety disorders, and poor quality of life has been observed. Dialysis can also lead to physical symptoms of its own, such as fatigue, loss of appetite, anemia, low blood pressure, and fluid overload, in addition to the symptoms associated with kidney failure. Therefore, this critical review aims to comprehensively understand the impact of dialysis membrane bioincompatibility and the use of varying molecular weight cut-off membranes on the physical and psychological symptoms experienced by dialysis patients. We analyzed the latest research on the correlation between major inflammatory biomarkers released in patients’ blood due to membrane incompatibility, as well as the critical influence of low levels of hemoglobin and vital proteins such as human serum albumin due to the use of high-cut-off membranes and correlated these factors with the physical and psychological symptoms experienced by dialysis patients. Furthermore, our study aims to provide valuable insights into the impact of dialysis on critical symptoms, higher hospitalization rates, and the quality of life of First Nations, as well as child and youth dialysis patients, in addition to diabetic dialysis patients. Our goal is to identify potential interventions aiming to optimize the dialysis membrane and minimize its negative effects on patients, ultimately improving their well-being and long-term outcomes.

Mathematical and statistical modeling of glucose permeation through ultrafiltration system

Membrane bioreactors (MBRs) have been recently proposed for enhancing enzymatic hydrolysis of lignocelluloses by simultaneously and selectively removing the produced sugars from the reaction system. An inverted dead-end MBR with polyethersulfone membrane was used to investigate glucose permeation. The effects of glucose concentration, water flowrate, and membrane molecular weight cut-offs (MWCO), were investigated. The developed diffusion-convective model predicted glucose permeation with R2 value of 0.96. The statistical analysis showed that the effects of glucose concentration and water flowrate were significant, with P-value less than 0.05 for both, whereas that of the MWCO was insignificant (P-value of 0.66). This is the first attempt to mathematically describe the behavior of glucose across ultrafiltration membrane, while taking into consideration both molecular diffusion and convective flow. The findings of this work are essential for understanding the behavior and enhancing the performance of solute permeation through ultrafiltration membrane, which is the heart of many processes.

Bovine Serum Albumin Rejection by an Open Ultrafiltration Membrane: Characterization and Modeling.

The classic application of ultrafiltration (UF) is for the complete retention of proteins, and in that situation, the transport behavior is well established. More open membranes with fractional retention are used when separating different proteins. However, protein transport has not been well documented yet in the literature. The bovine serum albumin (∼69 kDa) observed rejection ranges from 0.65 to 1 using a 300 kDa molecular weight cut-off membrane at different pH, ionic strength, and pressure. We demonstrated that, especially with open UF, the transport of proteins through the membrane is dominated by advection, with insignificant diffusion effects (p value > 0.05). We showed that with open UF, retention is not only caused by size exclusion but also to a large extent by electrostatic interactions and oligomerization of the proteins. Mass transfer in the polarization layer was relatively independent of the pH and ionic strength. It was underestimated by common Sherwood relations due to a relatively large contribution of the reduction in the flow turbulence near the membrane by the removal of fluid through the membrane. We propose a model that allows relatively quick characterization of the rejection of proteins without prior knowledge of the pore sizes and charges based on just a limited set of experiments. Therefore, protein rejection with the open UF system can be targeted by tuning the processing conditions, which might be useful for designing protein fractionation processes.

Critical fractions in reclaimed water responsible for membrane fouling: Isolation, fouling characteristics, quantitative and qualitative variations in practical application

Considering the different fouling characteristics between model foulants and organic components in real reclaimed water, it is of great importance to identify the critical foulants responsible for membrane fouling. This study identified and isolated the fraction with molecular weight (MW) > 100 kDa as the critical foulant in secondary effluent by MW cut-off membrane of 100 kDa with high efficiency. This fraction accounted for 92.2% membrane fouling of raw water, including 28.7%, 29.7% and 33.8% fouling contribution by subfractions with MW between 100–300, 300–500 and > 500 kDa. Specifically, the critical fraction with MW > 100 kDa were mainly distributed in two parts: < 0.22 μm and > 0.45 μm, corresponding to 41.9% and 56.9% fouling contribution of this fraction. Furthermore, both total organic carbon (TOC) and fouling potential of fraction with MW > 100 kDa were monitored, presenting about threefold increase from September to January in next year. Membrane fouling contribution of this critical fraction in raw secondary effluent were mainly distributed in 85∼95% throughout the 5 months, demonstrating its predominant fouling propensity. Moreover, the TOC concentration of fraction with MW > 100 kDa presented distinct positive correlation with the fouling potential of raw secondary effluent (R2 = 0.947), which was promising to be a surrogate for predicting membrane fouling in practical application.

Isolation of Polyphenols from Aqueous Extract of the Halophyte Salicornia ramosissima.

Polyphenols from residual non-food grade Salicornia ramosissima have health-promoting effects in feed, food, or nutraceutical applications. Therefore, the isolation of polyphenols is of interest from a series of environmentally friendly isolation methods with recyclable solvents. The isolation of polyphenols from non-food grade S. ramosissima was investigated using sequential membrane filtration with and without acid pretreatment, liquid-liquid extraction, resin adsorption, and centrifugal partition chromatography (CPC); analyzed by the Folin-Ciocalteu assay for total polyphenols; and finally analyzed using UPLC-TQMS in negative ion-spray mode for detection of 14 polyphenols. Sequential membrane filtration and acid hydrolysis indicated the polyphenols forming complexes with other compounds, retaining the polyphenols in the retentate fraction of large molecular weight cut-off membrane sizes. Conventional liquid-liquid extraction using sequential ethyl acetate and n-butanol showed most polyphenols were extracted, apart from chlorogenic acids, indicating a low isolation efficiency of higher polarity polyphenols. Analysis of the extract after resin adsorption by Amberlite XAD-4 resin showed high efficiency for separation, with 100% of polyphenols adsorbed to the resin after 13 bed volumes and 96.7% eluted from the resin using ethanol. CPC fractionations were performed to fractionate the concentrated extract after resin adsorption. CPC fractionations of the 14 polyphenols were performed using an organic or aqueous phase as a mobile phase. Depending on the mobile phase, different compounds were isolated in a high concentration. Using these easily scalable methods, it was possible to comprehensively study the polyphenols of interest from S. ramosissima and their isolation mechanics. This study will potentially lead the way for the large-scale isolation of polyphenols from S. ramosissima and other complex halophytes. The compounds of the highest concentration after CPC fractionation were isoquercitrin and hyperoside (155.27 mg/g), chlorogenic acid (85.54 mg/g), cryptochlorogenic acid (101.50 mg/g), and protocatechuic acid (398.67 mg/g), and further isolation using CPC could potentially yield novel polyphenol nutraceuticals.

Enhancement of water permeability in SiO2-ZrO2 nanofiltration membranes via adding organic solutes into the SiO2-ZrO2 sols

SiO2-ZrO2 nanofiltration membranes were prepared by adding glucose into SiO2-ZrO2 sols, followed by coating on cylindrical alumina porous support and firing at 550 °C. The average pore sizes of the SiO2-ZrO2 membranes by adding glucose in the SiO2-ZrO2 sols were larger than without adding glucose in sols. Water permeabilities of SiO2-ZrO2 membranes, prepared from 1.0 wt% SiO2-ZrO2 sols with and without the addition of 0.5 wt% glucose, were 4.2 × 10−12 m3/ (m2 s Pa) and 2.0 × 10−12 m3/ (m2 s Pa), respectively, while both of SiO2-ZrO2 membranes with and without addition of glucose showed approximately the same molecular weight cut-off (MWCO) of 300 g/mol.After membrane treatment in water at 90 °C, the water permeability of 1 wt% SiO2-ZrO2 membranes increased dramatically, while the MWCO of membranes remained the same as that before the treatment. The water permeability of membranes with and without addition of 0.5 wt% glucose increased from 4.2 × 10−12 to 9.1 × 10−12 m3/ (m2 s Pa) for MWCO of 320 g/mol and from 2.0 × 10−12 to 4.9 × 10−12 m3/ (m2 s Pa) for MWCO of 300 g/mol, respectively. An increase in the water permeability of SiO2-ZrO2 membranes after treatment in water at 90 °C can be explained by increasing in the hydrophilic surface and inner membrane pore and the dissolution of silica into hot water. SiO2-ZrO2 membranes with doping glucose achieved enhancement in the water permeability and hydrothermal stability.

Intramodule pressure profiles and protein accumulation during tangential flow filtration.

Tangential flow filtration (TFF) through a 30 kDa nominal molecular weight cut-off (MWCO) ultrafiltration membrane is widely employed to concentrate purified monoclonal antibodies (mAbs) to levels required for their formulation into injectable biologics. While TFF has been used to remove casein from milk for cheese production for over 35 years, and in pharmaceutical manufacture of biotherapeutic proteins for 20 years, the rapid decline in filtration rate (i.e., flux) at high protein concentrations is a limitation that still needs to be addressed. This is particularly important for mAbs, many of which are 140-160 kDa immunoglobulin G (IgG) type proteins recovered at concentrations of 200 mg/mL or higher. This work reports the direct measurement of local transmembrane pressure drops and off-line confocal imaging of protein accumulation in stagnant regions on the surface of a 30 kDa regenerated cellulose membrane in a flat-sheet configuration widely used in manufacture of biotherapeutic proteins. These first-of-a-kind measurements using 150 kDa bovine IgG show that while axial pressure decreases by 58 psi across a process membrane cassette, the decrease in transmembrane pressure drop is constant at about 1.2 psi/cm along the 20.7 cm length of the membrane. Confocal laser scanning microscopy of the membrane surface at the completion of runs where retentate protein concentration exceeds 200 mg/mL, shows a 50 μm thick protein layer is uniformly deposited. The localized measurements made possible by the modified membrane system confirm the role of protein deposition on limiting ultrafiltration rate and indicate possible targets for improving membrane performance.

Preparation of Nanoemulsions with Low-Molecular-Weight Collagen Peptides from Sturgeon Fish Skin and Evaluation of Anti-Diabetic and Wound-Healing Effects in Mice.

This study aims to isolate collagen peptides from waste sturgeon fish skin, and prepare nanoemulsions for studying their anti-diabetic and wound-healing effects in mice. Collagen peptides were extracted and purified by acetic acid with sonication, followed by two-stage hydrolysis with 0.1% pepsin and 5% flavourzyme, and ultrafiltration with 500 Da molecular weight (MW) cut-off dialysis membrane. Animal experiments were performed with collagen peptides obtained by pepsin hydrolysis (37 kDa) and pepsin plus flavourzyme hydrolysis (728 Da) as well as their nanoemulsions prepared at two different doses (100 and 300 mg/kg/day). The mean particle size of low-MW and low-dose nanoemulsion, low-MW and high-dose nanoemulsion, high-MW and low-dose nanoemulsion and high-MW and high-dose nanoemulsion was, respectively, 16.9, 15.3, 28.1 and 24.2 nm, the polydispersity index was 0.198, 0.215, 0.231 and 0.222 and zeta potential was -61.2, -63.0, -41.4 and -42.7 mV. These nanoemulsions were highly stable over a 90-day storage period (4 °C and 25 °C) and heating at 40-100 °C (0.5-2 h). Experiments in mice revealed that the low-MW and high-dose nanoemulsion was the most effective in decreasing fasting blood glucose (46.75%) and increasing wound-healing area (95.53%). Collectively, the sturgeon fish skin collagen peptide-based nanoemulsion is promising for development into a health food or wound-healing drug.

Ultrafiltration and Nanofiltration for the Removal of Pharmaceutically Active Compounds from Water: The Effect of Operating Pressure on Electrostatic Solute-Membrane Interactions.

The present work investigates nanofiltration (NF) and ultrafiltration (UF) for the removal of three widely used pharmaceutically active compounds (PhACs), namely atenolol, sulfamethoxazole, and rosuvastatin. Four membranes, two polyamide NF membranes (NF90 and NF270) and two polyethersulfone UF membranes (XT and ST), were evaluated in terms of productivity (permeate flux) and selectivity (rejection of PhACs) at pressures from 2 to 8 bar. Although the UF membranes have a much higher molecular weight cut-off (1000 and 10,000 Da), when compared to the molecular weight of the PhACs (253-482 Da), moderate rejections were observed. For UF, rejections were dependent on the molecular weight and charge of the PhACs, membrane molecular weight cut-off (MWCO), and operating pressure, demonstrating that electrostatic interactions play an important role in the removal of PhACs, especially at low operating pressures. On the other hand, both NF membranes displayed high rejections for all PhACs studied (75-98%). Hence, considering the optimal operating conditions, the NF270 membrane (MWCO = 400 Da) presented the best performance, achieving permeate fluxes of about 100 kg h-1 m-2 and rejections above 80% at a pressure of 8 bar, that is, a productivity of about twice that of the NF90 membrane (MWCO = 200 Da). Therefore, NF270 was the most suitable membrane for this application, although the tight UF membranes under low operating pressures displayed satisfactory results.

Antioxidant activities of lupin (Lupinus angustifolius) protein hydrolysates and their potential for nutraceutical and functional foods

Bioactive peptides are the compounds used as medicines, nutraceuticals and food preservatives. In this study, lupin protein hydrolysates were produced by enzymatic hydrolysis using pepsin, pancreatin and flavourzyme and antioxidative activities of the hydrolysates were measured. Protein was isoelectrically isolated from the lupin seed flour and enzymatically hydrolysed. The hydrolysates were ultrafiltered using molecular weight cut-off (MWCO) membranes. Fractions with masses of <2 kDa, 2–3 kDa, 3–5 kDa and 5–10 kDa were separated from the hydrolysates obtained at different hydrolysis times and then subjected to further fractionation by Size Exclusion Chromatography. Radical scavenging activities against DPPH·, ABTS·+, OH· and Fe2+ chelating abilities of these peptide fractions were measured. The best iron chelating, OH•, DPPH• and ABTS•+scavenging activities (IC50) were 30 ± 5.3, 40 ± 3.9, 60 ± 3.9 and 90 ± 8.2 µg/mL respectively. Pancreatin and Flavourzyme have produced more fractions with best scavenging activities after 3–4 h of hydrolysis (IC50 values in the range of 40–110 µg/mL). Generally Size Exclusion purified fractions displayed superior activities than the parent fractions. Several lupin peptide fractions showed comparable antioxidant capacities to those derived from soybean protein and displayed superior activities when compared with chickpea derived peptide fractions. Therefore, lupin protein hydrolysates are a potential source for nutraceuticals and functional foods.

Use of ultrafiltration/diafiltration for the processing of antisense oligonucleotides.

Ultrafiltration/diafiltration (UF/DF) has been the hallmark for concentrating and buffer exchange of protein and peptide-based therapeutics for years. Here we examine the capabilities and limitations of UF/DF membranes to process oligonucleotides using antisense oligonucleotides (ASOs) as a model. Using a 3 kDa UF/DF membrane, oligonucleotides as small as 6 kDa are shown to have low sieving coefficients (<0.008) and thus can be concentrated to high concentrations (≤200 mg/mL) with high yield (≥95%) and low viscosity (<15 centipoise), provided the oligonucleotide is designed not to undergo self-hybridization. In general, the oligonucleotide should be at least twice the reported membrane molecular weight cutoff for robust retention. Regarding diafiltration, results show that a small amount of salt is necessary to maintain adequate flux at concentrations exceeding about 40 mg/mL. Removal of salts along with residual solvents and small molecule process-related impurities can be robust provided they are not positively charged as the interaction with the oligonucleotide can prevent passage through the membrane, even for common divalent cations such as calcium or magnesium. Overall, UF/DF is a valuable tool to utilize in oligonucleotide processing, especially as a final drug substance formulation step that enables a liquid active pharmaceutical ingredient.

The Application of Polyethersulfone Ultrafiltration Membranes for Separation of Car Wash Wastewaters: Experiments and Modelling.

The wastewater generated as a result of car washes is considered a new source of water. However, recovered water must meet the required quality criteria for reuse. For this purpose, the ultrafiltration (UF) process can be successfully used. The main aim of the present work was to investigate the influence of the membrane's molecular weight cut-off (MWCO) on the UF performance in terms of the fouling phenomenon and retention degree of car wash wastewater. Moreover, for a better understanding of the fouling mechanisms, Hermia's model was used. The experimental studies were conducted with the use of two polyethersulfone (PES) membranes (MWCO of 10 kDa and 100 kDa). It has been noted that the used membranes provided a high-quality permeate and excellent turbidity removal, up to 99%. Moreover, it has been noted that the MWCO membrane has a significant impact on the fouling mechanism. Generally, a much greater intensity of fouling for the membrane with MWCO of 100 kDa was observed. Results obtained in the present study showed that both real wastewaters and the clean solutions used for washing cars cause the fouling phenomenon. It has been proven that rinsing the membranes with water is not sufficient to recover the initial membrane's performance. Hence, periodic chemical cleaning of the membranes was required. Fitting the experimental data to Hermia's model allowed us to indicate that membranes with MWCO of 100 kDa are more prone to intermediate blocking. To sum up, the findings suggest that for the UF of the car wash wastewater, the use of membranes with MWCO equal to 10 kDa is recommended.

Controlling Cellulose Membrane Performance via Solvent Choice during Precursor Membrane Formation

Fabrication of cellulose membranes by alkaline hydrolysis of cellulose acetate (CA) membranes is a simple alternative method to preparing cellulose membranes via phase inversion from their ionic liquid solutions. In this study, three different solvent systems were used to fabricate cellulose acetate membranes by phase inversion, which are dimethyl sulfoxide and its mixtures with acetone and acetic acid. Acetone as cosolvent led to an asymmetric morphology with the densest selective layer, whereas acetic acid led to a loose, almost isotropic structure with high porosity and pore connectivity, also reflected in the pure water permeance and molecular weight cutoff (MWCO) of the CA membranes. Comparing the effects of these cosolvents on the phase inversion process, acetic acid decreased the solvent quality, increased nonsolvent–solvent interactions, and in total decreased the polymer solutions’ stability against phase separation. The phase inversion rate when acetic acid was used as cosolvent was also markedly lower, which was attributed primarily to the solvent’s much higher viscosity. After alkaline hydrolysis of the CA membranes, which converted them into cellulose membranes, the permeance and MWCO of large-pore, small-pore, and dense membranes changed in different directions. This was attributed to a changing membrane structure due to partial degradation of cellulose chains in an alkaline medium, which in turn can affect transport through both the pores and the membrane matrix.

Microwave-assisted design of nanoporous graphene membrane for ultrafast and switchable organic solvent nanofiltration

Layered two-dimensional materials can potentially be utilized for organic solvent nanofiltration (OSN) membrane fabrication owing to their precise molecular sieving by the interlayer structure and excellent stability in harsh conditions. Nevertheless, the extensive tortuosity of nanochannels and bulky solvent molecules impede rapid permeability. Herein, nanoporous graphene (NG) with a high density of sp2 carbon domain was synthesized via sequential thermal pore activation of graphene oxide (GO) and microwave-assisted reduction. Due to the smooth sp2 carbon domain surfaces and dense nanopores, the microwave-treated nanoporous graphene membrane exhibited ultrafast organic solvent permeance (e.g., IPA: 2278 LMH/bar) with excellent stability under practical cross-flow conditions. Furthermore, the membrane molecular weight cut-off (MWCO) is switchable from 500 Da size of molecule to sub-nanometer-size molecules depending on the solvent type, and this switching occurs spontaneously with solvent change. These properties indicate feasibility of multiple (both binary and ternary) organic mixture separation using a single membrane. The nanochannel structure effect on solvent transport is also investigated using computation calculations.

Critical minority fractions causing membrane fouling in reclaimed water: Fouling characteristics, mechanisms and control strategies

In regard to membrane-based technologies of wastewater reclamation, the reported key foulants were faced with dilemma that they could not be effectively separated and extracted from reclaimed water for thorough investigation. In this study, the crucial foulants were proposed as “critical minority fraction (FCM)”, representing the fraction with molecular weight (MW) > 100 kDa which could be easily separated by physical filtration using MW cut-off membrane of 100 kDa with fairly high recovery ratio. FCM with low dissolved organic carbon (DOC) concentration (∼1 mg/L) accounted for less than 20% of the total DOC in reclaimed water, while contributed to more than 90% of the membrane fouling, and thus FCM could be considered as a “perfect criminal” causing membrane fouling. Furthermore, pivotal fouling mechanism was attributed to the significant attractive force between FCM and membranes, which led to severe fouling development due to the aggregation of FCM on membrane surface. Fluorescent chromophores of FCM were concentrated in regions of proteins and soluble microbial products, with proteins and polysaccharides accounted for 45.2% and 25.1% of the total DOC, specifically. FCM was further fractionated into six fractions, among which hydrophobic acids and hydrophobic neutrals were the dominant components in terms of DOC content (∼80%) as well as fouling contribution. Regarding to these pronounced properties of FCM, targeted fouling control strategies including ozonation and coagulation were applied and proved to achieve remarkable fouling control effect. High-performance size-exclusion chromatography results suggested that ozonation achieved distinct transformation of FCM into low MW fractions, while coagulation removed FCM directly, thus leading to effective fouling alleviation. Therefore, the investigation of the critical foulants was expected to help glean valuable insight into the fouling mechanism and develop targeted fouling control technologies in practical applications.

Diagnostic Performance of Dengue NS1 and Antibodies by Serum Concentration Technique

Dengue infection has been a public health problem worldwide, especially in tropical areas. A lack of sensitive diagnostic methods in the early phase of the illness is one of the challenging problems in clinical practices. We, herein, analyzed 86 sera of acute febrile patients, from both dengue and non-dengue febrile illness, to study the diagnostic performance of dengue diagnostics. When compared with detection by Polymerase Chain Reaction (PCR), dengue NS1 detection by enzyme-linked immunosorbent assay (ELISA) had the highest sensitivity of 82.4% (with 94.3% specificity), while NS1 by rapid diagnostic test (RDT) had 76.5% sensitivity. IgM detection by ELISA and RDT showed only 27.5% and 17.9% sensitivity, respectively. The combination of NS1 and IgM in RDT yielded a sensitivity of 78.4%, with 97.1% specificity. One of the essential steps in making a diagnosis from patient samples is the preparation process. At present, a variety of techniques have been used to increase the number of analytes in clinical samples. In this study, we focused on the sample concentration method. The sera were concentrated three times with the ultrafiltration method using a 10 kDa molecular weight cut-off membrane. The results showed an increase in the sensitivity of RDT-NS1 detection at 80.4%, with 100% specificity. When combining NS1 and IgM detection, the concentration method granted RDT an 82.4% sensitivity, with 100% specificity. In conclusion, serum concentration by the ultrafiltration method is a simple and applicable technique. It could increase the diagnostic performance of point-of-care dengue diagnostics.

On the edge between organic solvent nanofiltration and ultrafiltration: Characterization of regenerated cellulose membrane with aspect on dendrimer purification and recycling

The performance of commercial cellulose membranes with pore size on the border between ultra- and nanofiltration in selected organic solvents was studied focusing on rejection of small solutes and applicability for dendrimer purification. Organic markers in the MW range 100 – 700 Da and polarity range from nonpolar to polar protic compounds (aliphatics, aromatics, ethers, esters and alcohols) were used for membrane characterization. Transmission experiments in mixtures of methanol and dichloromethane of variable ratio showed the suitability of tested membranes for intended purpose, bringing information on structural factors affecting the rejection. Besides solute molar volume, its polarity type, or affinity, most conveniently expressed by Hansen solubility parameters, was found to be a crucial factor; with increasing size of solute molecule the spatial arrangement becomes also important. Solvent composition influences not only the behavior of solutes, but it also affects the membrane structure: poor solvation of cellulose by less polar solvents causes partial pore collapse, resulting in a decrease of membrane molecular weight cutoff. This effect can be used to improve the retention of a target product, as was shown for the first generation amphiphilic dendron. In addition, a simple mathematical model, allowing to estimate the course of nanofiltration and to optimize its conditions in a semicontinuous dead-end setup, is presented.

Prediction of organic contaminant rejection by nanofiltration and reverse osmosis membranes using interpretable machine learning models.

Efficiency improvement in contaminant removal by nanofiltration (NF) and reverse osmosis (RO) membranes is a multidimensional process involving membrane material selection and experimental condition optimization. It is unrealistic to explore the contributions of diverse influencing factors to the removal rate by trial-and-error experimentation. However, the advanced machine learning (ML) method is a powerful tool to simulate this complex decision-making process. Here, 4 traditional learning algorithms (MLR, SVM, ANN, kNN) and 4 ensemble learning algorithms (RF, GBDT, XGBoost, LightGBM) were applied to predict the removal efficiency of contaminants. Results reported here demonstrate that ensemble models showed significantly better predictive performance than traditional models. More importantly, this study achieved a compelling tradeoff between accuracy and interpretability for ensemble models with an effective model interpretation approach, which revealed the mutual interaction mechanism between the membrane material, contaminants and experimental conditions in membrane separation. Additionally, feature selection was for the first time achieved based on the aforementioned model interpretation method to determine the most important variable influencing the contaminant removal rate. Ultimately, the four ensemble models retrained by the selected variables achieved distinguished prediction performance (R2adj = 92.4 %-99.5 %). MWCO (membrane molecular weight cut-off), McGowan volume of solute (V) and molecular weight (MW) of the compound were demonstrated to be the most important influencing factors in contaminant removal by the NF and RO processes. Overall, the proposed methods in this study can facilitate versatile complex decision-making processes in the environmental field, particularly in contaminant removal by advanced physicochemical separation processes.

Fractionation by ultrafiltration of an aqueous extract of chestnut obtained by pressurized hot water extraction

Different types, ceramic and polyethersulfone, ultrafiltration membranes were evaluated to purify a wood extract obtained in pressurized hot water conditions. Tests were performed at transmembrane pressure (TMP) from 0.4 to 2.0 bars with membrane molecular weight cut-offs ranging from 5 kDa to 100 kDa. The results showed the permeate fluxes were lower than 15 L.h-1.m-², except for the 100 kDa organic membrane, with no influence of the feed flowrate. The retention of total phenolic compounds highly depends on the membrane cut-off but the retention rates of gallic and ellagic acid were not directly link to the cut-off. The retention rate of gallic acid is lower than 10%, when ellagic acid had retention ranging from 75 to 95 % for the membrane 5 kDa. It is suggested that other phenomena could be involved in solute retention, i.e. Donnan effect or solubility, that could explain so large differences.

Composition of Colloidal Organic Matter in Phytoplankton Exudates

The colloidal organic matter (COM) was isolated from the exudates of three cultured phytoplonkters, namely the chlophyte nanoflagellate Tetraselmis sp., the diatom Chaetoceros socialis and the dinoflagellate Prorocentrum minimum, from the Gulf of Trieste (northern Adriatic Sea). The isolation of COM was performed by ultrafiltration with molecular weight cut-off membranes of 5 kDa and final desalinisation by dialysis. The composition of the COM was characterised using C elemental analysis and 1H NMR spectroscopy and compared with COM isolated from a marine sample from the same area (Gulf of Trieste). By using 1H NMR spectroscopy, it was possible to semi-quantitatively determine the concentrations of the main biochemical constituents present in the COM samples. The results showed that the phytoplankton COM was predominantly composed of polysaccharides, with minor contributions from proteins and especially lipids. Therefore, the phytoplankton COM mainly contributes to the marine COM pool in the polysaccharide fraction and less in the protein and lipid fractions.