Steric-hindrance Pore Research Articles

Separation of Antibiotics Using Two Commercial Nanofiltration Membranes—Experimental Study and Modelling

The widespread use of antimicrobial drugs has contributed to the increasing trace levels of contaminants in the environment, posing an environmental problem and a challenge to modern-day medicine seeking advanced solutions. Nanofiltration is one such breakthrough solution for the selective removal of antibiotics from wastewater due to their high efficiency, scalability, and versatility. This study examines the separation of antibiotics (sulfamethoxazole (SMX), trimethoprim (TMP), and metformin (MET), respectively) using commercially available membranes with an emphasis on AFC membranes (AFC 30 and AFC 80). Thus, we evaluate their efficacy, performance, and applicability in wastewater treatment processes. The data for characterizing the structural parameters of the NF membranes were determined from an uncharged organic solute rejection experiment, and the effect of various operating conditions on the retention of solutes was evaluated. All experimental data were collected using a laboratory-scale nanofiltration unit and HPLC, and rejection percentages were determined using analytical measurements. The results obtained allowed for the determination of the radius of the membrane pores using the Steric Hindrance Pore (SHP) model, resulting in values of 0.353 and 0.268 nm for the AFC 30 and AFC 80 membranes, respectively. Additionally, higher transmembrane pressure and feed flow were observed to lead to an increased rejection of antibiotics. AFC 30 demonstrated a rejection of 94% for SMX, 87% for TMP, and 87% for MET, while AFC 80 exhibited a rejection of 99.5% for SMX, 97.5% for TMP, and 98% for MET. The sieving effect appears to be the primary separation mechanism for AFC 30, as lower feed-flow rates were observed to intensify concentration polarization, thereby compromising rejection efficiency. On the contrary, AFC 80 experienced less concentration polarization due to its smaller pore sizes, effectively preventing pore clogging. Membrane performance was evaluated using the Spiegler–Kedem–Katchalsky model, based on irreversible thermodynamics, which effectively explained the mechanism of solute transport of antibiotics through the AFC 30 and AFC 80 membranes in the NF process.

Characterization Assessment on Nanofiltration Membrane using Steric-Hindrance Pore (SHP) and Teorell-Meyer-Sievers (TMS) Models

Interfacial polymerization (IP) is a simple process for modifying thin-film composite (TFC) polymers that can be used as separation membranes in water treatment. This work describes the IP process for the preparation of polyester TFC membranes using organic monomers, in particular triethanolamine (TEOA) and trimesoyl chloride (TMC). This work includes an evaluation of monomer concentration and polymerization reaction time as variables to determine the membrane properties and its performance as acid humic removal. The characterization of TFC membranes was investigated using field emission scanning electron microscopy (FESEM), steric hindrance pore (SHP) and Teorell-Meyer-Sievers model (TMS). This IP technique resulted in the membrane (NF-PES8-35) having the lowest contact angle (θ=34.0±0.35) and lower hydrophobicity (θ=62.6 ± 0.33) compared to the unmodified membrane. The rejection of NaCl by NF-PES8-35 membrane showed the highest 0.001 M NaCl (62.42%), while NF-PES4-15 membrane showed the lowest (2.4%). The highest removal of humic acid (97.8%) was achieved when separation was performed with the NF-PES6-35 membrane and the high performance polyester TFC membranes were exhibited in the water purification filtration system.

A Superstructure Based Optimization Approach for Regeneration Reuse of Water Network: Optimal Design of a Detailed Nanofiltration Regenerator Network

Increasing freshwater costs and environmental concerns have necessitated the adoption of strategies for reducing freshwater consumption and effluent water discharge in chemical processes. Regeneration technologies increase opportunities for water reuse and recycle, and nanofiltration has emerged as a competitive wastewater regeneration technology. However, the optimal design of nanofiltration networks has not been extensively investigated. This study presents a framework for the optimal design and synthesis of multicontaminant nanofiltration membrane regenerator networks for application in water minimization problems. Mathematical optimization technique is developed based on a superstructure containing all system components and streams, incorporating nanofiltration units, pumps, and energy recovery devices. A linear approach and the modified Spiegler-Kedem model are explored in modelling the nanofiltration, and the steric-hindrance pore model is used to characterize the membrane. The objective of the optimization is to simultaneously minimize the water consumption and the total annual cost of the network. Furthermore, the optimal size, configuration, membrane properties and operating conditions of the equipment are determined. The applicability of the model is illustrated using a case study of an integrated pulp and paper plant. It was found that detailed models with customized modules are more useful when compared to the linear “black box” approach and approaches using fixed module specifications. The customized, detailed design of the regenerator network increased freshwater savings by 24% when compared to a black-box model, 31% when compared to a detailed model with fixed module specifications and 41% when compared to a reuse-recycle system with no regeneration. Similarly, cost savings of 38, 35 and 36% respectively were obtained. A trade-off was noted between the energy costs and the other components of the objective function since more energy was required to facilitate the reduction of water consumption and capital requirements.

Separation performance and mechanism of the novel modified polyether sulfone composite nanofiltration membrane for the detection on dissolved organic nitrogen

AbstractThe most effective pretreatment method for the detection of dissolved organic nitrogen (DON) is the nanofiltration (NF) by effectively intercepting DON into the concentrated solution, thus increasing the proportion of DON in solution so that achieving accurate detection of DON. The existing NF pretreatment technology for detection of DON has the problem of low accuracy and unclear separation mechanism of mass transfer upon the NF membranes. Based on the problems of NF membrane, the polyether sulfone (PES) composite NF membrane was modified by mesoporous carbon and the basic performance parameters of the modified PES composite NF membrane were characterized by Static contact angle (SCA), Zeta potential, and X‐ray photoelectron spectroscopy (XPS). The results show that the optimum doping amount of mesoporous carbon is in the range of 0.5%–1.0%. Furthermore, the pore size of NF membrane could be controlled effectively by changing doping amount of mesoporous carbon, so as to guide the improvement of membrane pore structure. After the pretreatment of mesoporous material modified PES composite NF membrane, the ratio of dissolved inorganic nitrogen (DIN)/total dissolved nitrogen (TDN) could be reduced to 0.55–0.65 and the pretreatment effect was also affected by screening effect and electrostatic effect. The best retention performance of amino acids is the 1.0%C modified membrane which retention rate of the amino acid is between 32.3% and 94.7%, and the membrane loss of the four amino acids is much smaller than other membranes. The mass transfer process of NF membrane was simulated by steric‐hindrance pore (SHP) model, Teorell–Meyer–Sievers (TMS) model, and Electrostatic Steric‐hindrance (ES) model respectively. According to the simulation software designed by ourselves, the dominant effects of screening and electrostatic effects are simultaneously affected by the pore structure of membranes and the size of the contaminant molecules.Practitioner points The feasibility of mesoporous carbon with modified PES composite nanofiltration membrane pretreatment for DON measurement in comparison to pure NF membranes was investigated. The ability of modified PES composite NF membrane with different molecular weight of DON and the relationship between pore radius of membrane and interception pollutant molecular size was discussed. The influence of screening effect and electrostatic effect on the retention of pollutants was discussed by the SHP model, TMS model and ES model; the simulation software interface is designed and the calculation process of the model is simulated by computer.

Comparison of the performance of three nanofiltration membranes for the reduction of fluoride ions: application of the Spiegler–Kedem and Steric Hindrance Pore Models

Comparison of the performance of three nanofiltration membranes for the reduction of fluoride ions: application of the Spiegler–Kedem and Steric Hindrance Pore Models

Charge Property Modeling of Nanofiltration Hollow Fiber Membranes

The development of models that predict membrane performance has contributed a better understanding of the basic principles and mechanisms of solute rejection and deposition. It also serves as fundamental properties that allow specific characterization determination. This work fabricates hollow fiber membranes using Polyethersulfone (PES). The membranes were fabricated in-house using phase inversion technique by modification with synthesized charged-surface modifying macromolecules (cSMM). The cSMM comprise with end-group component of Hydroxybenzene sulfonate or Hydroxybenzene carboxylate. The electrical properties of the membranes were modeled by utilizing the combination of irreversible thermodynamic model, Steric- Hindrance Pore (SHP) model and Teorell-Meyer-Sievers (TMS) model. The negatively-charged of the modified hollow fiber membranes was calculated based on sodium chloride rejection experimental performance. The analysis of the modeling results revealed that the modification of nanofiltration membrane using sulfonate induce negative 1.61 electrical properties compared to carboxylate that is negative 1.49 for both type modified PES membranes.

Effect of pH on produced water treatment using nanofiltration membranes: artificial neural network for performance assessment and steric hindrance pore model for flux variation evaluation

Effect of pH on produced water treatment using nanofiltration membranes: artificial neural network for performance assessment and steric hindrance pore model for flux variation evaluation

Implementation of Spiegler⁻Kedem and Steric Hindrance Pore Models for Analyzing Nanofiltration Membrane Performance for Smart Water Production.

A predictive model correlating the parameters in the mass transfer-based model Spiegler–Kedem to the pure water permeability is presented in this research, which helps to select porous polyamide membranes for enhanced oil recovery (EOR) applications. Using the experimentally obtained values of flux and rejection, the reflection coefficient σ and solute permeability Ps have been estimated as the mass transfer-based model parameters for individual ions in seawater. The reflection coefficient and solute permeability determined were correlated with the pure water permeability of a membrane, which is related to the structural parameters of a membrane. The novelty of this research is the development of a model that consolidates the various complex mechanisms in the mass transfer of ions through the membrane to an empirical correlation for a given feed concentration and membrane type. These correlations were later used to predict ion rejections of any polyamide membrane with a known pure water permeability and flux with seawater as a feed that aids in the selection of suitable nanofiltration (NF) for smart water production.

Salt rejection behavior of carbon nanotube-polyamide nanocomposite reverse osmosis membranes in several salt solutions

The present paper describes the desalination performance of reverse osmosis (RO) membranes of multi-walled carbon nanotube-polyamide complex (CNT-PA) and commercial polyamide membranes in NaCl, MgCl2, MgSO4 and Na2SO4 aqueous solutions. The permeate flux, salt rejection, and salt flux were determined in a cross-flow experiment. The CNT-PA and commercial RO (PA) membranes (SWC5, Nitto Denko Co.) showed 96.0% and 99.7% salt rejection, respectively, for 0.2% NaCl aqueous solution at 0.7 MPa. The calculated salt flux was 0.38 g·m−2·h−1 (CNT-PA) and 0.07 g·m−2·h−1 (SWC5). The salt rejection increased with increasing running pressure and decreasing salt concentration. The zeta potential measurement of CNT-PA demonstrated that it is negatively charged due to the presence of CNT. Accordingly, it showed salt rejection performances against the four salt solutions (Na2SO4 > MgSO4 > NaCl > MgCl2) that differed from that of the usual PA membranes (Na2SO4 > MgSO4 > MgCl2 > NaCl). These data are explained based on the Donnan model (CNT-PA) and steric hindrance pore model (SWC5), except for the case of chlorides under low-flux or high ionic strength conditions, where the diffusion and molecular size exclusion of the salts dominate over their mas-transport. Positron annihilation lifetime spectroscopy (PALS) enabled the estimation of the pore diameters of these membranes: 0.55 nm (CNT-PA) and 0.58 nm (SWC5).

Interpreting rejection in SRNF across grafted ceramic membranes through the Spiegler-Kedem model

PDMS-grafted alumina membranes have already demonstrated high organic solvent permeabilities; described and modeled in this paper are their retention capabilities. In contrast to pure PDMS polymeric membranes, higher retentions were found in nonpolar solvents than in polar solvents. This is attributed to a solvent-induced pore-constriction behavior: confined swelling of PDMS, grafted into the membrane pores, was found to increase retention. To test this hypothesis, pore sizes were obtained by integrating the Ferry, Verniory and steric hindrance pore (SHP) equations into the Spiegler Kedem Katchalsky (SKK) model in order to predict the retention of dyes. Ultimately, a diffusion pore size was introduced into the SKK model to reflect the ability of the solute to diffuse through the swollen PDMS graft. A better understanding of the transport mechanisms that impact performance was achieved by incorporating the unique pore structure of these ceramic-based hybrid membranes into the SKK model.

Investigating the mechanism of nanofiltration separation of glucosamine hydrochloride and N-acetyl glucosamine

Glucosamine hydrochloride (GAH) and N-acetyl glucosamine (NAG) are chitin derivatives. Owing to their excellent biological activity, they have long been used as pharmaceuticals and nutraceuticals. However, both of them exist simultaneously in chitin hydrolyzate or fermentation production. The aim of this study is to identify the feasibility of separating GAH and NAG by nanofiltration on the basis of appropriate adjustments of physical conditions. One commercial spiral nanofiltration membrane (QY-5-NF-1812) was used. Experiments were carried out in full recycle mode and the membrane separation performance was investigated at various mass ratios (mass ratios of GAH to NAG were from 1:14 to 1:2), pressures (4–22 bar), temperatures (15–35 °C), and electrolytes (NaCl, MgSO4, and MgCl2). The influence of temperature on molecular characteristics that play an important role in the separation process was also studied. Owing to the steric-hindrance effect, electrostatic effect, and different solute permeability, the GAH separation factor increased with increasing GAH concentration. Furthermore, upon temperature increasing, the permeability difference between GAH and NAG decreased, thus decreasing the GAH separation factor. Simultaneously, with increasing temperature, the polarities and calculated molecular diameters for both GAH and NAG increased evidently. The calculated reflection coefficients for both GAH and NAG can be well fitted by the steric-hindrance pore (SHP) model, suggesting that steric-hindrance effect played an important role on the separation process. Furthermore, owing to Donnan repulsion and solute diffusion effects, three electrolytes had noticeable effects on nanofiltration separation efficiency. The nanofiltration separation efficiency of GAH and NAG was significantly affected by their physical properties in this system, and the mechanisms for GAH and NAG separation were elucidated. The current study could provide a certain basis for the nanofiltration separation of GAH and NAG on an industrial scale.

Mechanism underlying the nanofiltration of protein hydrolysates in chitin alkali wastewater

AbstractTo investigate mechanism underlying the nanofiltration (NF) of protein hydrolysates in chitin alkali wastewater, the physicochemical characteristics of the protein hydrolysates were identified by mass spectrometry analysis, and the Teorell–Meyer–Sievers (TMS) and the steric-hindrance pore models were induced to calculate the parameters of the virgin and fouled NF membranes (NFM). Results showed that the peptides with molecular weights (MW) lower than 470 g/mol permeated the NFM except ones whose isoelectric points (pI) were at approximately 4, whereas peptides with MW of 490–1500 g/mol were efficiently rejected regardless of their pIs. The surface charge densities of virgin and fouled NFM to solute concentration ratios were 2.39 and 4.16, respectively. The pore radiuses of the virgin and fouled NFM were 0.52 and 0.48 nm, respectively, indicated that the increase of the rejection of crude proteins during their NF might result from the enrichment of the NFM surface negative charge and the NFM pore b...

Coupled model of extended Nernst–Planck equation and film theory in nanofiltration for xylo-oligosaccharide syrup

This work presents an observed retention ( R obs ) model for xylo-oligosaccharides (XOs) syrup in nanofiltration (NF) process. A commercial-purchased HDS-12-2540 NF membrane was operated in batch recycling model. The volume flux ( J v ), trans-membrane pressure (Δ P), solute concentrations in feed solution ( C b ) and permeate solution ( C p ) were collected and the experimental R obs was obtained. On the basis of the extended Nernst–Planck equation and film theory, a theoretical R obs model was established. The model parameters including solute permeability ( P s ) and reflection coefficient ( σ) for arabinose, xylose and xylobiose were estimated by curving fitting using genetic algorithm (GA) method. It was found that the reflection coefficient ( σ) for arabinose (0.895) was higher than that for xylose (0.776), which indicated that the membrane retention to arabinose was stronger. Membrane structural parameters, such as ratio of solute radius to pore radius ( λ) and ratio of effective membrane porosity to membrane thickness ( A k /Δ x), were also estimated using steric-hindrance pore (SHP) model.

Effect of SPEEK content on the morphological and electrical properties of PES/SPEEK blend nanofiltration membranes

Polyethersulfone (PES)/poly (ether ether ketone) (SPEEK) blends nanofiltration membrane at different SPEEK contents were prepared using a simple dry-jet wet spinning technique. The SPEEK polymer with fixed sulfonation degree was used for membrane preparation and characterized using FTIR and nuclear magnetic resonance (NMR) spectrometer. The morphological and electrical properties of the blends membrane were deduced based on the combination of irreversible thermodynamic model, steric-hindrance pore model (SHP) and Teorell–Meyer–Sievers model (TMS). The modeling results have been analyzed and discussed. The effect of SPEEK content on the blend properties was further studied in detail by FTIR, DSC and TGA and the results were discussed.

The formation and characterisation of an asymmetric nanofiltration membrane for ammonia–nitrogen removal: Effect of shear rate

The focus of this research is to study the potential of nanofiltration membrane technology in removing ammonia–nitrogen from the aquaculture system. One of the major fabrication parameters that directly affect the separation performance is shear rate or casting rate during membrane fabrication. In this study, asymmetric polyethersulfone (PES) nanofiltration membranes were prepared at five different shear rates within the range of 67–400 s −1. Membrane productivity and separation performance were assessed via pure water, salt and ammonia–nitrogen permeation experiments, and their structural properties were determined by employing the combination of the irreversible thermodynamic (IT) model, solution diffusion model, steric hindrance pore (SHP) model and Teorell–Meyers (TMS) model. The study reveals that the alteration of shear rate enormously affects the membrane morphology and structural parameters, hence subsequently significantly influencing the membrane performance. It was found that, membrane produced at the shear rate 200 s −1 or equivalent to 10 s of casting speed during membrane fabrications managed to remove about 68% of ammonia–nitrogen, in which its separation performance is the most favourable by means of highest flux and rejection ability towards unwanted solutes. Besides, from the research findings, nano-membrane technology is a potential candidate for the treatment of aquaculture wastewater.

Theoretical studies on structural and electrical properties of PES/SPEEK blend nanofiltration membrane

AbstractPolyethersulfone (PES) nanofiltration membranes were prepared using a simple dry‐jet wet spinning technique with different contents of sulfonated poly(ether ether ketone) (SPEEK) ranging from 0 to 4 wt %. The structural parameters (rp and Ak/Δx) and electrostatic properties (ξ and X) of the blend membranes were deduced by employing the combination of irreversible thermodynamic model, steric hindrance pore (SHP) model, and Teorell‐Meyer‐Sievers (TMS) model. The modeling results obtained have been analyzed and discussed. The mean pore radius and pore size distribution of the blends were also determined based on the theoretical models. The results showed that pore radius increased with increasing the concentration of SPEEK from 0 to 2 wt % but decreased with a further increase in SPEEK content. The water flux, however, showed a systematically increase with increasing SPEEK content. The SPEEK also showed significant effect on membrane electrical properties. Both effective charge density and ratio of effective charge density to electrolyte solution increased with increasing concentration of SPEEK in the dope solution, reaching a value of −21.02 and −2.29, respectively. The pore radius which was determined by using different transport models has also been analyzed and discussed. It is found that the addition of SPEEK into dope solution is one of the paramount parameters in developing the negatively charged nanofiltration membrane with enhanced water flux while retaining the pore radius in the nanometer range. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Theoretical studies on the morphological and electrical properties of blended PES/SPEEK nanofiltration membranes using different sulfonation degree of SPEEK

Sulfonated poly(ether ether ketone)s (SPEEKs) with different sulfonation degrees (DS) were synthesized and characterized using FTIR and NMR for the preparation of blend nanofiltration (NF) membranes. Blends of polyethersulfone and SPEEK at various SPEEK concentrations and various DS were prepared by a simple dry-jet wet spinning technique. The changes in the morphological and electrical properties of the blend membranes were deduced by employing the combination of irreversible thermodynamic model, Steric-Hindrance Pore (SHP) model and Teorell–Meyer–Sievers (TMS) model and the modeling results have been analyzed and discussed in detail. The results showed that the membrane water flux, pore size and surface charge were dependent on the content and DS of SPEEK used. FESEM–EDX results also provided supporting evidence for the trends observed for the morphological and electrical studies.

Characterization and applications of nanofiltration membranes: State of the art

There is a voluminous literature on the determination of structural and electrical properties of a nanofiltration (NF) membrane and its separation performance. Theories used to characterize a NF membrane usually include: the non-equilibrium thermodynamic model, the pore model, the TMS model, the electrostatic and steric-hindrance pore model, and the semi-emprical model. In the article, we briefly trace the origins or the general ideas of the above-mentioned theories. From there, recent researches on the evaluation of membrane structural and electrical properties are reviewed. We then turn to research on the separation performance of a NF membrane for single component solutions of inorganic electrolytes, neutral organic solutions, and mixture solution of inorganic electrolytes or that of electrolyte and neutral organic solute. Finally, we conclude with suggestions as to the role of models in the contributions to the application of the NF technology in product separation processes.

Influence of membrane, solute and solution properties on the retention of phenolic compounds in aqueous solution by nanofiltration membranes

The objective of this study was to investigate the physico-chemical parameters that determine the retention of phenolic compounds in aqueous solution by nanofiltration membranes. To this purpose, fundamental properties of two membranes (NF90 and NF270) were determined from their observed performance. Molecular weight cut-offs (MWCO) were determined using crossflow filtration of different molecular weights of polyethylene glycol (PEG). Their mean pore size was also estimated by the steric hindrance pore (SHP) model using neutral organic solutes (saccharides). The salt retention sequence of membranes was determined using single aqueous solutions of Na 2SO 4, NaCl and CaCl 2. Retention of phenolic compounds by NF270 was lower than that of NF90, because of its larger pore size. The influence of the solute adsorption upon the NF90 membrane retention was described by the molecular hydrophobicity of organic compounds. Finally, the effect of solution chemistry upon the membrane retention of phenol and resorcinol was investigated at different pH values. Near the isolelectric point of the membranes, minimum organic retention and maximum flux were observed due to membrane electroneutrality.

Modelling of the pore structure variation with pH for pore-filled pH-sensitive poly(vinylidene fluoride)–poly(acrylic acid) membranes

Pore structure variation as a function of pH was investigated for the pore-filled pH-sensitive poly(acrylic acid)-poly(vinylidene fluoride) membranes. The pore radius reduced drastically as the poly(acrylic acid) gel incorporated inside the nascent substrate, which is from 113 nm of nascent substrate to as low as 7.0 nm of pore-filled membranes at pH acidic. For the membranes, the pore radii at pH neutral estimated by the extend Nernst–Planck equation (2.76–4.20 nm) and by the Spiegler–Kedem model with the steric-hindrance pore model (3.4–4.1 nm) are close to each other and comparable with that calculated from the poly(acrylic acid) gel correlation length (1.79–2.93 nm). The calculated pore density at pH neutral (49–258 × 10 14 m −2) is much higher than that at pH acidic (2.8–39.8 × 10 14 m −2). The results are interpreted in terms of the gel structure in the pore-filled membranes.