Molecular Weight Cut-off Values Research Articles

Cleaning of Ultrafiltration Membranes: Long-Term Treatment of Car Wash Wastewater as a Case Study.

Car wash wastewaters (CWWs) contain various pollutants with different contents. Hence, selecting an appropriate process for their treatment is a great challenge. Undoubtedly, the ultrafiltration (UF) process is one of the most interesting and reliable choices. Therefore, the main aim of the current study was to investigate the performance of the UF membranes used for the long-term treatment of real CWWs. For this purpose, two polyethersulfone (PES) membranes with molecular weight cut-off (MWCO) values equal to 10 and 100 kDa were applied. As expected, a significant decrease in the permeate flux during the UF run was observed. However, it was immediately demonstrated that the systematic cleaning of membranes (every day) with Insect agent (pH = 11.5) prevented a further decline in the process's performance. In addition, this study focused on the relative flux during the process run with breaks lasting a few days when the UF installation was filled with distilled water. The results of this research indicated that aqueous media favor microorganism adherence to the surface which leads to the formation of biofilms inside processing installations. As a consequence, many attempts have been made to restore the initial membrane performance. It has been found that the application of several chemical agents is required. More precisely, the use of an Insect solution, P3 Ultrasil 11 agent, and phosphoric acid increases the relative flux to a value of 0.8. Finally, it has been indicated that the membranes used in this work are resistant to the long-term exposure to bacteria and chemical agents. However, during the separation of CWWs for the membrane with an MWCO of 10 kDa, a lesser fouling influence and higher effectiveness of cleaning were obtained. Finally, the present study demonstrates a novel analysis and innovative implications towards applying the UF process for the CWW treatment.

Construction of ultrathin and microporous polyesteramide nanofilms for efficient organic solvent nanofiltration (OSN) using diacyl chloride

The integration of high permeability and exceptional selectivity, thereby overcoming the conventional “trade-off” effect, remains a persistent challenge for the practical implementation of organic solvent nanofiltration (OSN) membranes. Herein, at the molecular level of design, we utilized the 5,5′-diamino-2,2′-biphenol (amino-BIPOL) and diacyl chloride as IP monomers to prepare OSN membranes with high perm-selectivity. The amino-BIPOL, a contorted biphenol molecule with four reactive sites, serves as a molecular-level unit to hinder efficient packing of polymer chains and induce the formation of interconnected micropores in the resulting polyesteramide layers. By employing diacyl chloride terephthaloyl dichloride (TPC) and isophthaloyl dichloride (IPC) as the oil-phase cross-linker, two kinds of TFC membranes were prepared. The resulting membranes both present smooth surface morphology, with ultrathin and high microporous selective layer allowing for efficient mass transfer. Specifically, the methanol permeance of amino-BIPOL/TPC and amino-BIPOL/IPC membrane reaches up to 15.1 and 15.6 LMH/bar, while maintaining a molecular weight cut-off (MWCO) value of 300 and 373 Da, respectively. Overall, this work illustrates the different oil-phase cross-linkers will result in diverse nanofilm microstructure and thus with distinct perm-selectivity properties, offering new insights for the design and modification of advanced OSN membranes.

Membrane-Based Preparation Process and Antioxidant and Anti-AGEs Activities of a Novel Propolis Ultrafiltrate.

Propolis is one functional supplement with hundreds of years of usage. However, it's rarely consumed directly for its resinous property. Herein, a pre-treated process which can remove the impurity while preserve its bioactivities is needed to maximise its therapeutic opportunities. In the present study, a membrane-based ultrafiltration process was developed on a KM1812-NF experimental instrument. Using Brazilian green propolis as testing material, all experimental steps and parameters were sequentially optimized. In addition, a mathematical model was developed to fit the process. As a result, the optimum solvent was 60 % ethanol adjusted to pH 8-9, while the optimum MWCO (molecular weight cut-off) value of membrane was 30 KDa. The membrane filtration dynamic model fitted with the function y=(ax+b)/(1+cx+dx2 ). The resulting propolis ultrafiltrate from Brazilian green propolis, termed P30K, contains the similar profile of flavonoids and phenolic acids as raw propolis. Meanwhile, the ORAC (oxygen radical absorbance capacity) value of P30K is 11429.45±1557.58 μM TE/g and the IC50 value of inhibition of fluorescent AGEs (advanced glycation end products) formation is 0.064 mg/mL. Our work provides an innovative alternative process for extraction of active compounds from propolis and reveals P30K as an efficient therapeutic antioxidant.

Richer than previously probed: An application of 1H NMR reveals one hundred metabolites using only fifty microliter serum

The classical approach restricts the detection of metabolites in serum samples by using nuclear magnetic resonance (NMR) spectroscopy; however, the presence of copious proteins and lipoproteins emphasize and necessitate the development of a contemporary, high-throughput tactic. To eliminate the lipoproteins and proteins from sera to engender filtered sera (FS), the study was executed with 50 μl serum obtained from five healthy individuals with 5 years of age difference from 25 to 45 years old and the application of a unique mechanical filter with molecular weight cut-off value of 2KDa. The 10 μl FS from each individual was pooled to make 50 μl final volume filled in a co-axial tube for acquisition of a battery of 1D/2D investigations at 800 MHz NMR spectrometer and the assigned metabolites was confirmed through mass spectrometry as well as by comparing 1H NMR spectra of individual metabolites. This innovative tactic is commissioning to reveal more than 100 metabolites. In contrast to the protein precipitation method, 24 new metabolites were recognized in the present study. The present innovative approach characterizes nucleosides, nitrogenous bases, and volatile metabolites that possibly produce a landmark for the delineation of a comprehensive metabolic profile applicable for detection of the molecular cause of pathogenicity, early-stage disease detection and prognosis, inborn error of metabolism, and forensic investigations exerting the least volume of FS and NMR spectroscopy. The assignment of 100 metabolites using 1H NMR-based FS is described for the first time in the present report.

Swift fabrication of thin-film composite membranes with azine-linked covalent organic framework for high-temperature organic solvent nanofiltration

Covalent organic frameworks (COFs) belong to a class of crystalline and porous solids that are generated by the self-assembly of reactive monomers via covalent linkage. Most existing methods for fabricating COF membranes are tedious, and they focus on quality control challenges associated with thickness uniformity, pore size, and mechanical properties. In this study, TraHz and TpaHz COF-based thin-film composite (TFC) membranes were prepared via the swift interfacial polymerization (IP) of hydrazine and aldehyde monomers on a polyacrylonitrile (PAN) support. Hydrazine played a dual role in one-pot synthesis, where PAN was crosslinked and IP was initiated. Varying the polymerization time allowed for fine-tuning the membrane thickness and performance. The membranes displayed robust high-temperature separation performance in polar aprotic solvents at temperatures of up to 80 °C. The toluene permeance of the membranes was remarkable. The permeance was highly dependent on both the applied pressure and temperature; however, the rejection performance was less dependent on these parameters. Based on the results of the nanofiltration performance evaluated using different molecular-weight dyes, a molecular-weight cut-off value of ∼650 g mol−1 and a rejection higher than 98 % for the Congo red and Chicago blue dyes in water, THF, and ethanol were observed. The dye rejection in toluene was higher than 98 % for Rhodanile blue, while maintaining high toluene permeances of 47 and 33 L m−2 h−1 bar−1 using TraHz-30 and TpaHz-30, respectively. In addition, both membranes exhibited stable separation performance. Our TFC membranes demonstrate a new approach for designing robust and high-flux nanofiltration membranes for precise molecular sieving even at high temperatures.

Investigating bromide incorporation factor (BIF) and model development for predicting THMs in drinking water using machine learning

Many disinfection byproducts (DBPs) in drinking water can pose cancer risks to humans while several DBPs including trihalomethanes are typically regulated. Although trihalomethanes are regulated, brominated fractions (bromodichloromethane, dibromochloromethane and bromoform) are more toxic to humans than the chlorinated ones (chloroform). To date, >100 models have been reported to predict DBPs. However, models to predict individual trihalomethanes are very limited, indicating the needs of such models. Various factors including natural organic matter (NOM), bromide ions (Br−), disinfectants (e.g., chlorine dose), pH, temperature and reaction time affect the formation and distribution of trihalomethanes in drinking water. In this study, NOM was fractionated into four groups based on the molecular weight (MW) cutoff values and their respective contributions to dissolved organic carbon (DOC), trihalomethanes and bromide incorporation factors (BIF) were investigated. Models were developed for predicting chloroform, bromodichloromethane, dibromochloromethane, bromoform and trihalomethanes. Three machine learning techniques: Support Vector Regressor (SVR), Random Forest Regressor (RFR) and Artificial Neural Networks (ANN) were adopted for training and testing the models. The normalized BIFs were in the ranges of 0.08–0.16 and 0.07–0.15 per mg/L of DOC for pH 6.0 and 8.5 respectively. The BIFs were higher for lower pH and MW values while increase of bromide to chlorine ratios increased BIFs. The models showed excellent predictive performances in training (R2 = 0.889–0.998) and testing (R2 = 0.870–0.988) datasets. The SVR and RFR models showed the best performances with lower RMSE and MAE in most cases. These models can be used to better control different trihalomethanes in drinking water to maintain regulatory compliance, and to minimize the risks to humans.

Solution-processable poly(ether-ether-ketone) membranes for organic solvent nanofiltration: from dye separation to pharmaceutical purification

Through polymer engineering, the membrane properties can be considerably changed and its performance can be improved. Organic solvent nanofiltration (OSN) membranes require polymers with good solution processability to facilitate membrane preparation. However, the resultant membranes should have excellent solvent resistance. Poly(ether-ether-ketone) (PEEK) is a potential polymer for OSN applications because of its high thermal stability and excellent solvent resistance. However, commercial PEEK has limited solution processability, and its fabrication requires a harsh acidic environment. Herein, two customized PEEKs were synthesized by incorporating methyl (–CH3) and sulfonyl (SO2) groups into the polymer backbone. The membranes were prepared by phase inversion using N-methyl-2-pyrrolidone (NMP) and TamiSolve as a green alternative. The effects of the polymer structure, green solvent, and crosslinking on the membrane morphology, chemical and mechanical stability, as well as separation performance have been examined. The molecular interaction between organic solvents and PEEKs were investigated through molecular dynamic simulations and density functional theory. The molecular weight cutoff (MWCO) values of the membranes were 540–768 g mol−1, with a high corresponding permeance of 8.2–20 L m−2 h−1 bar−1 in acetone. The long-term stability of membranes was successfully demonstrated over two weeks through a continuous crossflow filtration using acetone under a pressure of 30 bar. The membranes demonstrated excellent active pharmaceutical ingredient purification through the removal a 2-methoxyethoxymethyl chloride (125 g mol−1) carcinogenic impurity from roxithromycin (837 g mol−1).

#3270 TRANSPORT AND HYDROLYSIS OF ICODEXTRIN DURING PERITONEAL DIALYSIS

Abstract Background and Aims α-amylase, an enzyme present in plasma and peritoneal tissue, takes part in the process of starch digestion. During peritoneal exchange with icodextrin-based solution, polysaccharide chains are hydrolysed to shorter oligosaccharide chains, influencing osmotic properties of peritoneal dialysate. We estimated peritoneal transport parameters and compared them with hydrolytic clearances using a new model that takes into consideration absorption of icodextrin from the peritoneal cavity and its degradation by α-amylase. Method Frequent dialysate and blood samples were taken in 11 patients (8 icodextrin-naïve, 3 icodextrin-exposed) undergoing 16-hour dwell studies with icodextrin-based dialysis solution and labeled serum albumin (RISA) added as a volume marker. Using data on the intraperitoneal volume and dialysate and blood concentrations of glucose, urea, creatinine, and 7 icodextrin molecular weight (MW) fractions (glucose polymer size classes) and dialysate concentrations of α-amylase the extended three-pore model was applied to estimate individual parameters related to the peritoneal transport induced by dialysis and to hydrolysis of icodextrin by α-amylase. The following MW cut-off values were assumed for icodextrin fractions: up to 1.08, 4.44, 9.89, 21.4, 43.5, 66.7 and over 66.7 kDa, called Fractions 1–7, respectively. The hydrolytic clearances were defined as rate at which dialysate volume is cleared of the fraction by hydrolysis. The time-dependent hydrolytic clearances of icodextrin fractions were calculated and compared with diffusive ones. For the first time the extended three-pore model was validated not only with respect to the peritoneal transport of water and small solutes but also regarding concentration of icodextrin fractions. Results Mean measured and simulated dialysate to plasma concentration ratios for glucose, urea and creatinine are presented in Figure 1, left panel. The peritoneal kinetic of icodextrin (dialysate concentrations of each fraction over its initial concentration) is presented for mean measured data and numerical simulation results in Figure 1, right panel. The results showed that the model provides accurate (mean relative error less than 7%) description of individual patient peritoneal transport kinetics including that of icodextrin fractions in peritoneal dialysate. The comparison of hydrolytic clearances (H) with diffusive transport parameters for icodextrin fractions (PS, reflecting the maximal rates of their clearance by diffusion) showed that in case of shorter polymers (Fractions 1–3) diffusive clearances were higher or similar to hydrolytic ones over the whole dwell time. In case of Fractions 4 and 5, the initial domination of PS slowly decreased during the dwell time, being dominated by hydrolysis processes at the end of the exchange, at least partly due to the changes of intraperitoneal volume and α-amylase concentration. In case of polysaccharides from Fractions 6 and 7, their hydrolytic clearances remained higher than the diffusive ones during whole dwell time. Interestingly, the obtained values of H in icodextrin-exposed patients typically remained below 1.2 mL/min except for Fraction 6, for which H increased from initial value of 0.83±0.30 to 1.43±0.64 mL/min at the end of the peritoneal dwell. On the other hand, the estimated final values of H in icodextrin-naïve patients were on average higher than 1.2 mL/min in all fractions except Fractions 4 and 5. Conclusion The model provided accurate description of peritoneal transport and icodextrin hydrolysis during long icodextrin dwells. The model showed that hydrolytic processes dominate over diffusive ones during whole dwell time in case of Fractions 6 and 7, whereas diffusive processes dominate for Fractions 1–3.

Intestinal absorption of DHA microcapsules with different formulations based on ex vivo rat intestine and in vitro dialysis models.

Intestinal permeability is a key factor affecting the bioavailability and physiological efficacy of docosahexaenoic acid (DHA) encapsulated in microcapsules. However, how the DHA microcapsules are transformed and the components absorbed across the small intestinal membrane has seldom been examined previously. In this study, an ex vivo absorption model based on the permeability of the rat small intestine was established to evaluate the intestinal absorption of DHA microcapsules with five formulations after gastrointestinal digestion in vitro. For pure glucose solutions, the apparent permeability coefficient (Papp) increased from 5.70 ± 0.60 × 10-6 cm s-1 at 5 mg mL-1 to 20.25 ± 0.88 × 10-6 cm s-1 at 30 mg mL-1 and decreased to 15.73 ± 0.91 × 10-6 cm s-1 at 100 mg mL-1. The Papp values obtained using the ex vivo model are comparable to those reported in the human jejunum. For algal oil DHA microcapsules with whey protein as the wall material (A-WP-DHA) after in vitro digestion, the Papp of glucose released was 3.81 × 10-6 cm s-1 with an absorption ratio of 59.55% in the ex vivo model, significantly lower than that from the in vitro porcine casing model. The Papp and absorption ratio varied little among the in vitro dialysis models with different molecular weight cut-off values. A similar trend was observed for the absorption of amino acids. However, the absorption ratio (26.6%) was the highest in the ex vivo model for free fatty acids (FFAs) released from the microcapsules due to the rapid accumulation of compounds on the inner wall of the intestinal sac. In addition, the DHA microcapsules with algal oil as the DHA source (36.40%) exhibited a higher absorption ratio of FFAs than that from tuna oil (14.26%) in the ex vivo model. The wall material compositions seemed to have little effect on FFA absorption. The present study is practically meaningful for the future formulation of DHA microcapsules with enhanced absorption.

2D conjugated microporous polymer membranes for organic solvent nanofiltration

Two-dimensional conjugated microporous polymer (CMP) membranes have gained increasing attention in the nanofiltration field owing to their tunable pore structure and solvent stability. Nevertheless, fabricating freestanding thin films with accessible porosity is challenging. In this study, we fabricated four freestanding CMP membranes based on the benzobisoxazole linkage and investigated their performance for organic solvent nanofiltration (OSN). The effect of pore size on the OSN performance was studied by investigating three CMP structures (B-BOP, TPPy-BOP, and TPB-BOP)-based membranes with various theoretical pore sizes (1.4, 1.6, and 2.8 nm, respectively). The effect of pore functionalization on the molecular sieving properties was evaluated by comparing two otherwise equivalent CMP structures with and without fluorine functionalization (TPB-BOP and TPB-F-BOP, respectively). The inherent control on the membranes’ molecular sieving properties is evidenced by the proportionality between the pore sizes of the CMP structures and their filtration performances. The molecular weight cutoff (MWCO) values for B-BOP, TPPy-BOP, TPB-BOP, and TPB-F-BOP were 676, 760, 1759, and 1402 g mol−1, respectively, which were consistent with the expected trend based on theoretical pore sizes. The experimental results are consistent with pore flow model predictions, indicating that the pore structure remains intact despite the materials lack long-range order. All the CMP membranes demonstrated long-term stability, exhibiting a constant acetone flux (212 L m−2 h−1 for B-BOP and 879 L m−2 h−1 for TPB-BOP) and Rose Bengal rejection (100 % for B-BOP and 67 % for TPB-BOP) over 120 h of continuous operation at 30 bar.

Solvent-resistant polyimide aerogel film as ultrapermeable support for thin-film composite and covalent organic framework nanofiltration membranes

Organic solvent nanofiltration (OSN) membranes require robust selective layers and support materials. In this study, polyamide and polyester thin-film composites (TFCs) and covalent organic frameworks (COFs) were fabricated as selective layers on a polyimide aerogel support. The ultrapermeable support was stable in various organic solvents including harsh polar aprotic solvents such as N,N-dimethylformamide (DMF), dimethylsulfoxide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone for more than six months. The support enabled fabricating both amorphous and crystalline selective layers at both room and higher temperatures. Moreover, the polyimide aerogel support had 85% porosity, facilitating high solvent flux. The compatibility of the selective layers and support was excellent, and as low molecular weight cutoff values (MWCO) as 356 and as high as 591 g mol−1 were obtained in methanol at 10 bar for the COFs and polyester TFC membranes, respectively. Both experimental MWCO and permeance values of the COF membrane agreed with those predicted using the pore flow model. The effect of the operating temperature on the OSN performance was examined in DMF at 20 and 100 °C. Both membranes demonstrated constant permeance and rejection for more than nine days of continuous filtration.

Antibacterial Activity of Silver Nanoflake (SNF)-Blended Polysulfone Ultrafiltration Membrane

The aim of this research was to study the possibility of using silver nanoflakes (SNFs) as an antibacterial agent in polysulfone (PSF) membranes. SNFs at different concentrations (0.1, 0.2, 0.3 and 0.4 wt.%) were added to a PSF membrane dope solution. To investigate the effect of SNFs on membrane performance and properties, the water contact angle, protein separation, average pore size and molecular weight cutoffs were measured, and water flux and antibacterial tests were conducted. The antimicrobial activities of the SNFs were investigated using Escherichia coli taken from river water. The results showed that PSF membranes blended with 0.1 wt.% SNFs have contact angles of 55°, which is less than that of the pristine PSF membrane (81°), exhibiting the highest pure water flux. Molecular weight cutoff values of the blended membranes indicated that the presence of SNFs does not lead to enlargement of the membrane pore size. The rejection of protein (egg albumin) was improved with the addition of 0.1 wt.% SNFs. The SNFs showed antimicrobial activity against Escherichia coli, where the killing rate was dependent on the SNF concentration in the membranes. The identified bacterial colonies that appeared on the membranes decreased with increasing SNF concentration. PSF membranes blended with SNF, to a great degree, possess quality performance across several indicators, showing great potential to be employed as water filtration membranes.

TEMPO-mediated oxidation as surface modification for cellulosic ultrafiltration membranes: Enhancement of ion rejection and permeability

In membrane technology, rejection of dissolved salts often requires the use of nanofiltration or reverse osmosis membranes due to their sufficiently dense structure and favourable charge effects. In this work, the concept of charge-based salt rejection is extended to the more open ultrafiltration class. Surface charge of a commercial regenerated cellulose acetate ultrafiltration membrane is enhanced with TEMPO-mediated oxidation. With the modification, a membrane whose properties lie between the traditional nanofiltration and ultrafiltration classes is obtained. Moreover, a purely charge-based salt rejection mechanism is introduced to an ultrafiltration membrane.Increasing hypochlorite exposures are found to induce successively increasing surface carboxylate densities, negative zeta potentials, permeabilities and molecular weight cut-off values. In the low exposure region, the treatment mostly affects surface charge, whereas high exposures begin to open the membrane pores. Ultimately, the pH 7 zeta potential is increased from −30 up to −100 mV, and 500 ppm Na2SO4 rejections increase from an initial 4% to 36%. At the same time, pure water permeability is doubled, and cut-off value increased from 2.8 to 8.0 kDa. The reactions causing the change in membrane performance seem to take place almost exclusively on the membrane surface, while the bulk material appears unchanged.

Fabrication of sustainable organic solvent nanofiltration membranes using cellulose–chitosan biopolymer blends

Membrane technologies have emerged as a promising alternative to energy-intensive separation processes in various industrial sectors. To address the sustainability challenge associated with the fabrication of separation membranes, a paradigm shift from the use of petrochemical-based raw materials to greener biobased sources is highly desired. In this study, blends of cellulose — as a plant-based material — and chitosan — obtained from shrimp farming waste and used as a biomass material — were investigated for the fabrication of oil and solvent-resistant nanofiltration membranes. The structural, thermal, mechanical, and morphological properties of the prepared membranes were characterized. Molecular simulations were performed to study the fractional free volume and interaction energy among membrane constituents. Adjusting the cellulose–chitosan ratio allowed fine-tuning the molecular sieving properties of the membranes, which exhibited outstanding separation performance and chemical stability even in harsh solvents, such as polar aprotic solvents, at the maximum temperature of 100 °C. Cellulose membranes containing 25 wt% chitosan achieved the lowest molecular weight cutoff value of 413 g mol−1 and a permeance of 24 L m−2 h−1 bar−1 in acetonitrile. The membranes showed stable separation performance over 7 days of continuous cross-flow nanofiltration. Moreover, the cellulose membranes blended with 10–25 wt% chitosan showed decreased water permeance from 52 to 38 L m−2 h−1 bar−1 and increased oil-removal efficiency from 73.8% to 98.6%. Furthermore, the membranes successfully underwent biodegradation, confirming their potential to close the loop of the sustainable lifecycle of membranes from cradle to grave.

Antipathogenic upcycling of face mask waste into separation materials using green solvents

The use of disposable face masks has considerably contributed toward waste generation, particularly during the current COVID-19 pandemic. Little attention has been dedicated to the actual examination of recycling strategies for increasing the life cycle of this biomedical waste, as the most common treatment for disposing used masks is incineration. In this study, we screened green solvents for the recycling of face masks by taking advantage of their antipathogenic nature for sterilization purposes. This work is timely and unique because it presents for the first time the successful recovery of polypropylene from face masks, and upcycle of the masks into either a microbead or free-standing membranes as separation materials. Owing to their excellent chemical stability, the membranes are well-suited for organic solvent nanofiltration. The fabricated membranes exhibited molecular weight cut-off values between 665 and 964 g mol−1, which were fine-tuned by adjusting the coagulation bath temperature from 20 °C to 60 °C. The membranes demonstrated long-term stability over 5 days of continuous filtration at 30 bar, with rejection values exceeding 98% for roxithromycin and rose bengal. This scalable methodology for upcycling used face masks into high-value products has the potential to reduce a crucial environmental threat associated with the global rapid growth of the face mask market.

Development and Industrial-Scale Fabrication of Next-Generation Low-Energy Membranes for Desalination

Spiral-wound modules have been the most common configuration of packing flat-sheet membranes since the early development of polyamide (PA) membranes for water treatment applications. Conventional spiral-wound modules (SWMs) for desalination applications typically consist of several leaf sets, with each leaf set comprising feed spacers, membranes, and a permeate carrier (PC) wrapped around a permeate-collecting tube. The membrane area that can be packed into a given module diameter is limited by the overall leaf set thickness, restricting module productivity for a given membrane permeability. We describe here a novel industrial-scale method for successfully coating the polysulfone (PSf) ultrafiltration (UF) support layer directly onto a permeate carrier, instead of conventional non-woven fabric, as a precursor to the polyamide TFC coating, resulting in twofold benefits: (a) drastically simplifying the membrane fabrication process by eliminating the use of non-woven fabric and (b) increasing the throughput of each membrane module by facilitating the packing of a larger membrane area in a standard module housing. By combining the permeate carrier and membrane into a single sheet, the need for the non-woven support layer was eliminated, leading to a significantly reduced leaf set thickness, enabling a much larger membrane area to be packed in a given volume, leading to lower energy consumption per cubic meter of produced water. Molecular-weight cutoff (MWCO) values in the range of 36–96 kDa were found to be dependent on PC thickness and material. Nevertheless, the reinforced membranes were successfully fabricated with a ~9% reduction in membrane leaf thickness compared to a conventional membrane. Preliminary trials of coating a thin-film composite PA layer resulted in defect-free reverse osmosis (RO) membranes with a salt rejection of 94% and a flux of 40 L m−2 h−1 when tested against a 2000 mg/L NaCl feed solution at an operating pressure of 15 bar. Results from the testing of the 1812 and 2514 elements validated the novel concept and paved the way for further improvements towards full-scale RO membranes with the potential to be the next low-energy workhorse of the water industry.

Monoamine‐modified thin film composite nanofiltration membrane for permselective separation of fermentation bioproducts

AbstractOne process involved in biorefinery for generation of value‐added products is fermentation. After fermentation, the downstream bioproduct purification process is conventionally performed by organic solvent extraction, which is environmentally‐hazardous and costly. Membrane‐based separation is a cost‐efficient and environmentally‐benign method for bioproduct separation and purification. In this study, a thin film composite (TFC) nanofiltration (NF) membrane was prepared and the pore size and charge of the polyamide layer were controlled by introducing iminodiacetic acid (IDA), a charged monoamine monomer, with piperazine (PIP) during interfacial polymerization (IP). The newly‐developed NF membrane was found to have a molecular weight cut‐off (MWCO) of 500 to 1350 Da, allowing the permeation of the fermentation product, while rejecting other higher molecular weight compounds. IDA addition in the aqueous amine solution during IP effectively engineered the MWCO values and pore sizes of TFC NF membranes for specific applications, such as separation of fermentation bioproducts. This study successfully showed that IDA reduced the diffusivity of PIP during IP, which negatively affected the polyamide formation and membrane performance. The optimal PIP:IDA concentration ratio was determined by MWCO and effective pore diameter for effective bioproduct separation and purification, which could not be performed by the current commercially‐available NF membranes.

Development and Optimization of a Silica Column-Based Extraction Protocol for Ancient DNA.

Rapid and cost-effective retrieval of endogenous DNA from ancient specimens remains a limiting factor in palaeogenomic research. Many methods have been developed to increase ancient DNA yield, but modifications to existing protocols are often based on personal experience rather than systematic testing. Here, we present a new silica column-based extraction protocol, where optimizations were tested in controlled experiments. Using relatively well-preserved permafrost samples, we tested the efficiency of pretreatment of bone and tooth powder with a bleach wash and a predigestion step. We also tested the recovery efficiency of MinElute and QIAquick columns, as well as Vivaspin columns with two molecular weight cut-off values. Finally, we tested the effect of uracil-treatment with two different USER enzyme concentrations. We find that neither bleach wash combined with a predigestion step, nor predigestion by itself, significantly increased sequencing efficiency. Initial results, however, suggest that MinElute columns are more efficient for ancient DNA extractions than QIAquick columns, whereas different molecular weight cut-off values in centrifugal concentrator columns did not have an effect. Uracil treatments are effective at removing DNA damage even at concentrations of 0.15 U/µL (as compared to 0.3 U/µL) of ancient DNA extracts.

Effect of Dope Flow Rate and Post-Treatment on the Morphology, Permeation and Metal Ion Rejection from PES/LiBr-Based UF Hollow Fiber Membranes.

This study investigated the influence of dope extrusion rate (DER) and post-treatment effect on the morphology, permeation, and metal ion rejection by polyethersulfone/lithium bromide (PES/LiBr)-based hollow fiber (HF) membranes. HF fibers were spun with 2.25, 2.5, and 3.1 ratios of DER to bore fluid rate (BFR), wherein DER varied from 11.35, 12.5, to 15.6 mL/min with a fixed BFR (5 mL/min). Molecular weight cutoff (MWCO), pore size, water flux, and flux recovery ratio were determined, whereas lake water was used to observe the rejection rate of dissolved metallic ions. Results showed that with the increase of the DER wall thickness (WT), HFs increased from 401.5 to 419.5 um, and furthermore by the post-treatments up to 548.2 um, as confirmed by field emission scanning electron microscope (FESEM) analysis. Moreover, MWCO, pore size, and the pure water permeation (PWP) of the HF membranes decreased, while the separation performance for polyethylene glycol (PEG) solute increased with increasing DER. Post-treated HFs from 11.35 mL/min of DER showed 93.8% of MWCO value with up to 90% and 70% rejection of the arsenic and chromium metallic ions, respectively, in comparison with all other formulated HFs.

Solvent-Resistant Thin-Film Composite Membranes from Biomass-Derived Building Blocks: Chitosan and 2,5-Furandicarboxaldehyde

To address the increasing interest in environmental issues, green and sustainable material-based membranes have attracted significant research interest with the promise to replace fossil-based membranes and to reduce waste generation. In this work, more sustainable thin-film composite (TFC) membranes are designed and fabricated via interfacial polymerization of green building blocks, namely, shrimp farming waste chitosan in the aqueous phase and plant-based 2,5-furandicarboxaldehyde in the organic phase, on an upcycled polyethylene terephthalate porous support. The TFC membranes showed excellent acetone permeance up to 12 L m–2 h–1 bar–1 with a molecular weight cutoff value of approximately 317 g mol–1. The membrane separation performance was optimized by fine-tuning the building block concentrations, which provided a new upper-bound in the plot of acetone permeance versus styrene dimer rejection. In addition, for the first time, TamiSolve was employed as a green solvent to activate the selective layer of the chitosan-based TFC membrane, resulting in a significant enhancement in the permeance of diverse pure solvents including ethanol, methyl ethyl ketone, acetone, and acetonitrile with no remarkable defects and high solute rejections. Our proposed green TFC fabrication platform enables the replacement of toxic and fossil-based solvents and reagents in developing high-performance and solvent-resistant nanofiltration membranes.