High Rejection Rate Research Articles

Integrated Approach: Characterization, Application of Alumina Kaolin Membrane for Glycerol Separation in Biodiesel Production, and Flux Recovery Strategies

The transesterification process used for biodiesel production yields glycerol as a prominent byproduct. Given glycerol's adverse effects on engine performance and longevity, regulatory standards, such as those set by SNI and international authorities, restrict free glycerol content in biodiesel to below 0.02 wt.% or 200 ppm. Consequently, the removal of glycerol has become a critical step in biodiesel production. Traditional purification methods are energy-intensive and generate substantial wastewater, prompting the exploration of alternative solutions like membrane separation technology. Ceramic microfiltration membranes, renowned for their exceptional thermal, chemical, and mechanical durability, have emerged as a prominent choice. The development and application of a cost-effective Alumina-Kaolin ceramic microfiltration membrane for glycerol removal in biodiesel signify a promising advancement in water purification processes. The current study was conducted to evaluate the microfiltration performance of the Alumina-Kaolin ceramic membrane, investigate the impact of the membrane’s microstructure on separation performance, and explore cleaning strategies aimed at enhancing flux recovery ratio (FRR). The microstructure analysis through SEM and BET demonstrated pores in the membrane, featuring a 3.375 m2/g surface area, 30.367 % porosity, and 0.18 μm pore size. Several tests employed using different glycerol and water concentration in the feed of 1000 ppm, 5000 ppm and 10000 ppm. The evaluation gave high glycerol rejection rates of 92.07%, 98.52% and 98.94% for the respective feed concentrations with the permeate flux of 65.42 [l/(m2h)], 61.09 [l/(m2h)] and 52.91 [l/(m2h)] respectively. The microstructure of alumina-kaolin membrane could separate the larger particles of glycerol-water droplets and gave high separation performance. As the flux decline ratio increased (from 2.13% to 20.86%) due to rising glycerol concentration (1,000 to 10,000 ppm), cleaning became crucial for flux recovery. Employing various agents, benzalkonium chloride notably enhanced alumina-kaolin flux recovery ratio (FRR) to 98.17%.

Green Synthesis of Nanocomposite Membranes for Sustainable Water Filtration

In order to tackle the worldwide problems of water pollution and shortage, this work explores the green synthesis of nanocomposite membranes for sustainable water filtering. Graphene oxide, cellulose nanocrystals, and silver nanoparticles were used as nanofillers in the fabrication of nanocomposite membranes, which were made using renewable polymer matrix (PES, PVDF, PAN). By including different polymer matrices and nanofillers, the composition analysis demonstrated the adaptability of nanocomposite membrane manufacturing, enabling the customization of membrane characteristics. Improved membrane shape and structural integrity were shown to result from the homogeneous dispersion of nanofillers inside the polymer matrix, according to characterization tests. Nanocomposite membranes demonstrated high flux rates and rejection rates for different pollutants, confirming their excellent performance in filtration experiments. The membranes’ improved fouling resistance also increased their service life and decreased the frequency of maintenance needs. Supporting the eco-friendliness of nanocomposite membrane production, an environmental impact evaluation found that it used less energy and generated less trash than traditional techniques. All things considered, nanocomposite membranes have shown great promise as long-term water treatment solutions due to their superior performance, durability, and environmental friendliness, as well as their effective production and characterisation. More study is needed to perfect membrane characteristics and solve the remaining problems that prevent their broad use in water treatment systems.

High-frequency eddy current measurement for the characterization of graphite anode slurries in battery cell production

The global demand for lithium-ion batteries and their production in large quantities while maintaining high product quality and minimal reject rates poses new challenges for cell manufacturers. Quality control in slurry processing and electrode coating is becoming increasingly important due to high material costs. High-frequency eddy current measurement could enable characterization of the active material and reduce the reject rate by applying an inline quality measurement system. In this paper, the applicability of high-frequency eddy current measurement for characterization of graphite suspensions is investigated and its feasibility confirmed. Process parameters such as solids contents and type of graphite have been analyzed.

Pneumatosis Intestinalis and Pneumoperitoneum After Lung Transplantation: Single-Center Experience and Systematic Review.

Background: Pneumatosis intestinalis (PI) and pneumoperitoneum are some of the complications after lung transplantation (LT). But only limited reports are published. The purpose of this study is to review our experience and perform a systematic review to discuss the possible causes, risk factors, and management. Methods: We reviewed the characteristics, management, and outcome of the patients who developed PI or pneumoperitoneum after LT in our institution from 2013 to 2022. We also performed a systematic review to discuss the management and outcome. Results: PI and pneumoperitoneum were found in 15 out of 729 patients (2.06%) in our institution. We also found 50 patients in the systematic review. Tracheostomy was performed in 40% and gastrointestinal procedures were performed in 55.6%. Laparotomy was performed in 23.4%. A total of 44.6% of patients had benign physical exams or no symptoms. Rejection was seen in 42.9%. A total of 28.6% of patients died during follow-up periods. Conclusions: This report has the largest number of patients so far with PI and pneumoperitoneum after LT. These conditions have a high rejection and high mortality rate. Mechanical ventilation, tracheostomy, gastrointestinal procedure, CMV infection, Clostridium difficile (C. difficile) infection, and immunosuppression can be the risk factors, and the management includes laparotomy or conservative management. It is generally recommended to proceed with laparotomy if patients have portal venous gas, elevated white blood cell count, elevated lactic acid level, decreased bicarbonate level, elevated amylase level, metabolic acidosis, abdominal tenderness, or abdominal distension. Otherwise, most of the patients recover with conservative management with nil per os (NPO), metronidazole, ganciclovir, antibiotics, high-flow oxygen, and holding mycophenolate mofetil (MMF).

Partial exploitation of host egg patches resulting from a high rejection rate of healthy hosts cautions the mechanistic use of functional response models

Abstract The functional response of parasitoids is a main component of models that describe host–parasitoid interactions. When the functional response assumed in a model (e.g., a population model) is inaccurate, predictions by the model based on the functional response also become unreliable. This study reports that conventional functional response models may commonly fail to capture the actual functional response of parasitoids and discuss its implications. To assist the discussion, an experiment was conducted to describe interactions between the pupal parasitoid Dirhinus giffardii (Hymenoptera: Chalcididae) and its host Bactrocera dorsalis (Diptera: Tephritidae) in the laboratory. Results showed that the parasitoids typically interacted with all hosts in the environment but parasitised a small fraction of them (e.g., most encountered hosts were rejected), which deviates from the assumption of mechanistic functional response models. An increasing number of published studies on functional response also suggest (although circumstantially) the rejection of unparasitised hosts is common, suggesting that this behaviour is widespread among parasitoid species. By using the experimental results, the study discusses why existing hypotheses are insufficient for the observed behaviour and the implications of this behaviour within the realm of theories surrounding host–parasitoid interactions.

Preparation of a CPVC composite loose nanofiltration membrane based on plant polyphenols for effective dye wastewater treatment.

The textile industry's high-salinity wastewater presents a significant difficulty for fractioning salts and dyes. To fractionate the dyes and salts, a high-performance CPVC composite loose nanofiltration membrane (LNM) was fabricated by interfacial polymerization. The organic phase was obtained by crosslinking polyethylenimine (PEI) with tannic acid (TA) and gallic acid (GA) using TMC. The resultant composite LNM performance was enhanced by adjusting the coating parameters, which included TA and GA concentrations as well as coating time. The study examined the effects of the total content of TA/PEI and GA/PEI concentrations on the chemical structure, surface roughness, and microstructure of the selective layer of LNM using SEM, AFM, FTIR, and water contact angle measurements. It also investigated the filtration performance of the membrane's selective layer, including pure water flux, PEG800 rejection rate, and membrane fouling analysis. However, the resultant membrane treated simulated reactive black 5 (RB5) dye wastewater. When the total content of TA/PEI is 4 kg L-1, the permeability of pure water flux is high at 7.5 L per m2 per h per bar when the total content of GA/PEI is 14 kg L-1 and the pure water flux is high at 8.8 L per m2 per h per bar. The overall PEG800 rejection rates were 97-98.98%. The optimal TA : PEI ratios reached a good pure water permeability up to 6.4 L per (m2 per h per bar) with a high rejection rate of 99.69% for a ratio 1/3 to dye, and GA : PEI ratios reached a good water permeability at 5.5 and 6.5 L per (m2 per h per bar) with rejection rates of 99.21% and 98.88% for ratio 1/3 and 3.5/10.5 for simulated RB5 dye, and the NaCl retention rate gradually decreased from 4% to 3%. The resultant LNM demonstrated promising applications in dye and salt fractionation.

Quantum dot- β-Cyclodextrin nanofiller decorated thin film nanocomposite membrane for removal of cationic and anionic dyes from aqueous solution

Graphene oxide quantum dots (GOQDs) are finding tremendous attention as nanofillers in separation processes owing to their excellent chemical and mechanical robustness. GOQDs-functionalized thin film nanocomposite (TFN) membranes were fabricated via low pressure mediated interfacial polymerization (IP) over a polysulfone support, where β-Cyclodextrin (β-CD) was taken as an aqueous monomer with a fractional amount of GOQDs and tetraethylenepentamine (TEPA) as the organic monomer. The resultant TFN membranes showed improved hydrophilicity over its pristine polymeric analogue. The best performing membrane was obtained for MPG2, which had a mass loading of 3 % of β-CD, 0.3 % of TEPA and 0.4 % of GOQD during the interfacial polymerization. The membrane showed pure water flux that was two fold higher than that of the pristine polymeric membrane, with a dye rejection of 99.6 % for congo red and 96 % for methyl blue. This excellent rejection for the anionic dye can be attributed to the Donnan exclusion imparted by the negative charges on the membrane surface. The salt rejection properties of the membranes were also analyzed and the MPG2 membrane exhibited a high rejection rate of 96 % and 99.1 % for the salt containing Cl− and NO3− ions, respectively.

What do users and their aiding professionals want from future devices in upper limb prosthetics? A focus group study.

High rejection rates of upper limb prosthetics indicate that current prosthetic devices only partially meet user demands. This study therefore investigated the benefits and challenges with current prostheses, associated services and potential areas for improvement from the perspective of upper limb prosthesis users and various professionals working in the field of upper limb and hand prosthetics. Seven different focus group discussions were conducted with 32 participants. Participants were grouped by prosthesis type, if they were prosthesis users, or professionals. All focus group discussions were transcribed verbatim, and a summarizing content analysis was performed. Three main topic areas to be addressed emerged from the interviews: 1. a properly functioning prosthesis, 2. the infrastructure, and 3. users' psychological and physical prerequisites. The interaction between a well-functioning prosthesis and a well-developed infrastructure was shown to be important for successful use. Our study raises many of the same issues that have been reported in previous qualitative studies, dating back over several decades. This study underlines the need to include users and professionals in the future development of prosthetic devices.

Tailoring ultrafiltration membranes with chemically modified human hair waste for improved permeability and antifouling performance

Human hair, a pervasive waste product, has the potential to pose environmental challenges due to its widespread accumulation. Therefore, exploring of alternatives that repurpose this waste into a valuable raw material aligns with the principles of the circular economy. This study introduces a novel protocol for crafting biohybrid ultrafiltration (UF) membranes with tailored charges, enhanced hydrophilicity, and notable attributes of high flux, rejection rate, and resistance to fouling. These membranes have been engineered by combining sulfonated poly(ethersulfone) (SPES) with chemically modified human hair (HH) filler, referred to as HH-SO3-NH2, utilizing the non-solvent induced phase separation (NIPS) approach. The preparation of HH-SO3-NH2 involved converting of oxidized thiol groups within human hair to sulfonic acid. Subsequently, 1 and 3 wt percent of HH-SO3-NH2 were integrated into the SPES matrix to formulate the biohybrid membranes. After incorporating HH-SO3-NH2, the biohybrid membranes changed in mechanical properties, porosity, and surface morphology, resulting in increased hydrophilicity. The pure water flux exhibited a systematic rise with higher HH-SO3-NH2 content-specifically, the hybrid membrane with 3 wt% HH-SO3-NH2 achieved a water flux of 239 L m−2 h−1 at 1 bar feed pressure, representing a 1.5-fold increase compared to the bare membrane's 175 L m−2 h−1 flux. The anti-fouling performance was assessed using humic acid (HA) and the hybrid membranes demonstrated removal efficiency of HA exceeding 99% without compromising rejection rates.

MOTIVATIONAL FACTOR AND CONSTRAINTS IN ADOPTION OF POTATO CUTIVATION TECHOLOGY BY POTATO GROWERS UNDER CONTRACT FARMING

Most of the farm operators being small and marginal farmers in India, there are problems in getting quality raw material for processing, marketing, and distribution, especially in perishable high value crops but contract farming which was restricted, largely, to seed production earlier, spread to perishable produce and has now become the dominant and growing mode of raw material production and procurement co-ordination among the processors and fresh produce market and exporters. Potato is very important perishable high value crop in North Gujarat Agro-climatic zone of Gujarat state with the cultivating area of 97,204 hector in six districts of North Gujarat (Anon.2014-15). Therefore, the present investigation was conducted in the North Gujarat Agro climatic Zone of Gujarat state. Two districts viz., Banaskantha and Sabarkantha occupy the highest area under potato cultivation in North Gujarat and hence, were selected purposively for study. Ten potato growers were randomly selected from twenty villages. In all, 200 contracting potato growers were selected for the study. Important motivated factors farmers toward contract farming were; assured price, price stability, no tension of marketing, technical advice to control pests and diseases, no cash payment for seed. Majority (78.00%) of the potato growers had medium to high level of adoption regarding potato cultivation technology. Major constraints faced by potato growers in adoption of potato cultivation technology under contract farming were; high rejection rate, low contract price, high cost of inputs given by contracting company, poor quality seed supply by company and manipulation of norms by firm. Important suggestions expressed by the potato growers were; provision of supportive price, quality seed to be provided by company, government intervention for making strict laws to make legal contracts and technical advice to control pests and diseases.

Solar driven thermal responsive polyionic liquid/PDDA semi-IPN hydrogel for near-room temperature membrane-free osmotic desalination

The designed thermally responsive polyionic liquid (TPIL)/ poly (diallyl dimethylammonium chloride) (PDDA) hydrogel with a semi-interpenetrating (semi-IPN) structure, containing highly charged chloride anions, was fabricated to explore the comprehensive capabilities of solar driven membrane-free osmotic desalination. Introducing linear PDDA polyelectrolyte with higher charge density has effectively excluded salt ions from entering the TPIL hydrogel matrix due to the strong charge concentration gradient established between the hydrogel and the saline reservoir. Meanwhile, the thermo-sensitivity of the polyionic liquid/PDDA semi-IPN (PNCl) hydrogel enabled the release of absorbed salt-depleted water at a temperature above the Lower Critical Solution Temperature (LCST). The multiple purification process established by partial submersion of PNCl hydrogel in saline enabled continual reduction of the salt ion concentration during the upwards transportation of water along the polyelectrolyte network. Moreover, a mushroom-shaped hydrogel demonstrated enhanced the effectiveness in long-term cyclic desalination. The “mushroom cap” was loaded with photo-thermal conversion fillers (Ti3C2Tx MXene) to achieve higher photo-thermal conversion efficiency for water recovery. A record high salt rejection rate of more than 93% was obtained for membrane-free osmotic desalination. More importantly the whole desalination/water absorption/release process was solely supported by gently heating the PNCl hydrogel under the illumination of renewable solar energy.

A novel and simple fabrication method for a biomimetic-inspired lath-structured ceramic microfiltration membrane for the treatment of oil-in-water emulsions

Ceramic membranes have been widely explored as competent alternatives to traditional polymeric membranes for treating oily wastewater. Despite the exceptionally high rejection rate (>90 %) of oil–water (O/W) emulsions, membrane fouling is an inevitable phenomenon that limits the separation efficiency of ceramic membranes. Biomimetic technology, known as the lotus effect, has attracted attention as a groundbreaking method for reducing membrane fouling. However, it is difficult to control the nanostructured surfaces of ceramics, while polymer fabrication is facile. In this study, we developed a novel and simple method to fabricate an α-alumina (Al2O3) microfiltration (MF) membrane with a Nepenthes pitcher plant-like microstructure. The surface roughness of the biomimetic membrane was 286 nm, which was approximately twice that of a normal ceramic membrane. Accordingly, the oil contact angle increased from 88.84 to 128.51°. The novel biomimetic membrane showed high efficiency with an emulsion permeability of 44.1 LMH/bar, a flux recovery of 90.91 %, and an oil rejection rate of 99 %.

Are tube fill volumes below 90% a rejection criterion for all coagulation tests?

Rejected samples lead to prolonged turnaround time and delayed diagnosis and treatment of patients. This study was conducted to determine minimum acceptable sample volume in Sarstedt brand coagulation tubes to reduce high sample rejection rate. Blood samples were drawn from 20 participants (10 healthy volunteers and 10 patients receiving oral anticoagulant) into coagulation tubes. Six samples were taken from each participant, with tube fill volumes of 100%, 90%, 80%, 70%, 60%, and 50%. Prothrombin time (PT), active partial thromboplastin time (aPTT), and fibrinogen tests were analyzed. According to quality performance specifications, the tube fill volume must be at least 70% for PT and aPTT and 50% for fibrinogen. There was no statistical difference in samples from healthy volunteers for PT, aPTT, and fibrinogen tests when the minimum tube fill volume was at least 80%, 90%, and 50%, respectively. These percentages were 50%, 70%, and 60%, respectively, in patients receiving oral anticoagulant. Sarstedt tubes meet quality standard specifications at a 70% fill rate for PT and aPTT and a 50% fill rate for fibrinogen. Comprehensive studies with larger populations are needed to accept these values as sample acceptance criteria for the laboratory.

Comparison of 2D and 3D materials on membrane modification for improved pressure retarded osmosis (PRO) process

Pressure retarded osmosis (PRO) is a sustainable process that convert Gibbs free energy to osmotic energy by mixing two solutions of different salinities. The main challenges in the design of PRO membranes are obtaining a membrane with high water permeability and low salt permeability but also very high mechanical strength because the PRO process involves high pressure on the draw solution. Commercially available RO membranes with potential utility in a PRO system exhibit a high salt rejection rate but low water permeability and mechanical stability. Surface modification is a promising strategy for tuning the fundamental properties of the membranes (e.g. hydrophilicity, surface charge and thickness) that can improve the filtration performance of the membranes. The coating layer can also improve the mechanical stability of the membranes. Therefore, in this work, various types of modification materials were applied to the commercial available RO membranes to enhance their performance.With the assistance of hydrophilic materials (e.g. polydopamine – PDA), filtration performance of the membranes can be increased through membrane modification by 2D materials with high charge intensities (e.g. polyelectrolytes and graphene oxides) and by 3D mesoporous materials (e.g. zeolites), which increases the thickness of the membrane that can be beneficial in mechanically reinforcing the membrane. In this work, we modified commercial RO membrane with PDA, polyelectrolytes, graphene oxide and zeolites (ZSM-5). Improved filtration performance (increased water permeability and maintained salt permeability) of the modified membrane was observed. Tensile tests showed enhanced mechanical strength of the modified membranes, especially following 3D zeolites modification (up to 35 % of higher tensile strain was reported). Interestingly, a lower concentration of PDA (2 mg/mL) and zeolites resulted in higher mechanical strength of the modified membranes. Such results were likely due to a more homogenous coating layer when a low modifier concentration was applied. The thin and uniform layer can better absorb energy when membranes are under high pressure.

Direct-coating of cellulose hydrogel on PVDF membranes with superhydrophilic and antifouling properties for high-efficiency oil/water emulsion separation

As a well-known natural and innocuous plant constituent, cellulose consists of abundant hydroxyl groups and can tightly adsorb onto material surfaces hydrogen bonding, resulting in a superhydrophilic surface. In this work, the hydrophobic polyvinylidene fluoride (PVDF) membranes were modified by immersing them in cellulose hydrogel using a simple one-step process. The modified PVDF membrane exhibited excellent resistance to fouling and oil adhesion, making it highly effective in separating various oil-in-water emulsions. The cellulose-modified PVDF membranes achieved a high oil rejection rate (>99 %) and a maximum separation flux of 2675.2 L·m−2·h−1. Furthermore, even an oil-in-water emulsion containing bovine serum albumin maintained a steady permeation flux after four filtration cycles. Additionally, these cellulose-modified PVDF membranes demonstrated excellent underwater superoleophobicity across a wide range of pH levels and high saline conditions. Overall, these cellulose-modified superhydrophilic PVDF membranes are sustainable, environmentally friendly, easily scalable, and hold great promise for practical applications in oily wastewater treatment.

Novel Straightening-Machine Design with Integrated Force Measurement for Straightening of High-Strength Flat Wire.

In a punch-bending machine, wire products are manufactured for a wide range of industrial sectors, such as the electronics industry. The raw material for this process is flat wire made of high-strength steel. During the manufacturing process of the flat wire, residual stresses and plastic deformations are induced into the wire. These residual stresses and deformations fluctuate over the length of the semi-finished product and have a negative effect on the final product quality. Straightening machines are used to reduce this influence to a minimum. So far, the adjustment of a straightening machine has been performed manually, which is a lengthy and complex task even for an experienced worker. This inevitably leads to the use of inefficient straightening strategies and causes high rejection rates in the entire production process. Due to a lack of sensor information from the straightening operation, application of modern feedback control methods has not been practicable. This paper presents a novel design for a straightening machine with an integrated, precise straightening force measurement. By simultaneously monitoring the position of the straightening rollers, state variables of the straightening operation can be derived. Additionally, a tension control for feeding the flat wire is introduced. This is implemented to mitigate the disturbing effects caused by irregularities in the wire-feeding process. In the results of this article, the high precision of the developed force measurement design and its possible applications are shown.

Nanocomposite HKUST-1@polysulfone membrane for the adsorptive removal of tetracyclines in waters

To mitigate the presence of tetracyclines in water, it is essential to implement proper wastewater treatment processes that can effectively remove these compounds. In this work we develop a polymeric filtration membrane functionalized with nanocrystals of a metallic organic framework, designated by HKUST-1. The membrane was evaluated for the remotion of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) in water samples. The membrane was fabricated using polysulfone (PSU), polyethyleneglycol (PEG), MOF (HKUST-1), and N-methyl-2-pyrrolidone (NMP) through the nonsolvent induced phase separation (NIPS) method. The membrane that presents the best antibiotic rejection characteristics was prepared with 15 % (w/w) PSU, 3 % (w/w) PEG, 1 % (w/w) HKUST-1, and 81 % (w/w) N-methyl-2-pyrrolidone (NMP). This membrane exhibited a pure water flux of up to 76.2 L.m−2.h−1, approximately 40 times more than the one achieved for pristine membranes. Once determined the best membrane composition, a physical–chemical characterization of membrane was done. A high antibiotic rejection rate was obtained for OTC, TC, and CTC, around 91 %, 91 %, and 99 % respectively. The pH of solutions has a strong influence on membrane rejection. The results suggest that intermolecular forces such as π-π type interactions and hydrogen bonds exist between the neutral molecules of tetracyclines (pH > pKa1 and < pKa2) and HKUST-1@PSU MMM, which are greater than the electrostatic forces at pH < pKa1 or pH > pKa2. Furthermore, FTIR spectra demonstrate the formation of a Cu-tetracycline complex as another adsorption mechanism. Finally, the interaction of the tetracyclines in the mixture on the removal performance was evaluated. The study revealed that chlortetracycline (CTC) exhibited superior removal performance, even over extended periods of time, despite having a lower initial concentration in the mixture. This innovative membrane represents a new generation of highly efficient filter systems specifically designed for water purification purposes.

Towards sustainable management of end-of-life membranes: Novel transformation of end of life (EoL) reverse osmosis membranes for efficient dye/salt separation

Effective management of end-of-life (EoL) membranes is crucial for addressing environmental and economic concerns. A novel approach has been proposed in this study to transform discarded EoL reverse osmosis (RO) membranes into loose nanofiltration (NF) membranes that exhibit high flux and effective dye/salt fractionation. The proposed method involves oxidative treatment followed by a one-step co-deposition of polydopamine (PDA) and polyethylene glycol (PEG). Rigorous chemical and morphological characterization techniques have verified the successful transformation of the EoL membranes. The study's findings demonstrate the great potential of this method, as the transformed EoL membranes achieved high pure water permeability of 67 LMH/bar after only a 5-hour coating process, representing a remarkable 2.5-fold increase in permeability compared to the uncoated membrane. A 20-hour coating produced a denser film that reduced the permeability to 19 LMH/bar but increased the potential for dye/salt separation. The transformed membranes exhibited high rejection rates of dyes and ultra-low salt rejection, making them highly efficient for dye/salt separation. Moreover, the enhanced hydrophilicity of the transformed membranes inhibited foulant accumulation, resulting in excellent fouling resistance with a flux recovery ratio of 93.6 %. This novel approach offers a promising solution for treating dye-contaminated wastewater and promoting circular economy in membrane technology.

Polyamide nanofiltration membrane fabricated via a metal-chelate strategy for high-flux desalination

Nanofiltration (NF) technology, utilizing polyamide (PA) membranes fabricated through interfacial polymerization (IP), has found extensive application in desalination processes. The pursuit of enhancing water permeance while maintaining high rejection rates of NF membranes has garnered substantial research attention. This study proposed a metal-chelate strategy by incorporating calcium chloride (CaCl2) as an aqueous additive during the IP process and employing EDTA-4Na for post-treatment. In the presence of Ca2+, the EDTA-4Na-soaked membrane achieved suitable swelling to better regulate membrane pores, which benefited water flux enhancement and avoided severe structural defects. Meanwhile, the modified membrane also showed a more hydrophilic and negatively charged surface, leading to a significant performance in removing Na2SO4. As a result, the optimized membrane exhibited a water flux of 24.6 L m−2 h−1 bar−1, nearly 3 folds that of the initial PA membrane, while maintaining a satisfactory Na2SO4 rejection (97.2 %). Moreover, the obtained membrane showed good operation stability and anti-fouling properties during long-term use. This work proves that the metal-chelate strategy can be an efficient modification method and inspires the fabrication of high-performance NF membranes with coupling processing.

Thin film nanocomposite membranes fabricated via 2D ZIF-67 nanosheets and 1D nanofibers with ultrahigh water flux for dye removal from wastewater

Thin-film nanocomposite (TFN) membranes based on metal–organic frameworks (MOFs) have received increasing attention in the field of water treatment. However, TFN membranes with both high permeance and rejection rates are highly desired. In this study, ultra-thin ZIF-67 was synthesized and TFN membranes were fabricated by combining the obtained 2D ZIF-67 with cellulose nanofibers (CNF) and carbon nanotubes (CNTs). The nanofibers not only fill the gaps between the ZIF-67 nanosheets but also form an intercalation layer between the ZIF-67 nanosheets and function as a water transport pathway, leading to a significant enhancement of water permeance. By introducing CNF into the ZIF-67-embedded matrix, the dye rejection rates increase to 96.8 % and 93.3 %, respectively, with water permeance of about 90.0 L⋅m−2⋅h−1⋅bar−1. Further introducing CNT into the CNF/ZIF-67 membrane further improved the water permeance to 207.8 L⋅m−2⋅h−1⋅bar−1, while a dye rejection rate of 95.1 % was documented. The results indicate that the introduction of nanofibers into 2D MOF matrix to form TFN membranes has great potential for wastewater treatment.