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In our previous work, it was shown that the separation performance of the fixed-site-carrier polyvinylamine (PVAm) composite membrane increases exponentially with increasing relative humidity content in the gas. Through these efforts, it has been important to develop a greater understanding of the relationship between the water, structural, and int...
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Context 1
... at long range, the dispersive forces increase significantly. Figure 9 shows that the H(water)-bond acts as a donor and the H(amine)-bond acts as an acceptor. ...
Context 2
... second peak at 3 Å at low intensity corresponds to the attraction between g N(amine)−O(water) (r), whereas the third peak at 3.20 Å corresponds to the second hydrogen bond from the unprotonated state g N(amine)−H(water) (r). In this unprotonated case, the H(water)-bond acts as electron donor and the H(amine)-bond acts as electron acceptor, see Figure 9. ...
Citations
... Therefore, to simulate the acid−base equilibrium, a series of MD simulations should be performed for different macroscopic protonation states of a macromolecule. 50,62,79−82 Recently, such an approach has been applied to simulate pH-responsive conformation dynamics of single-chain oligomers and their self-assembly for poly(acrylic acid) 50,83 and poly(alkyl acrylic acids), 68,79,80,84,85 poly(ethylenimine), 81 poly(vinylamine), 86 poly(arginine), 46 and poly(dialkylamino)methacrylates, 51 respectively. ...
Silver nanoparticles (AgNPs) coated with pH-responsive polymers have become a very appealing “smart” nanocarrierfor targeted drug delivery. To get a better understanding of the structure of hybrid organic/inorganic nanomaterials, we studied pH-controllable coating of AgNPs by a block copolymer, poly(methyl methacrylate)-block-poly(2-(N,N -dimethylamino)ethylmethacrylate) (PMMA-b-PDMAEMA), by using atomistic molecular dynamics simulations. PMMA-b-PDMAEMA contains apoorly water-soluble nonionic PMMA chain and a pH-responsive PDMAEMA moiety capable of switching its conformation uponaltering pH. We found that the adsorption of a series of PMMA20-b-PDMAEMA20 oligomers onto AgNPs is crucially dependent onthe protonation degree (α) of PDMAEMA, which is defined as a ratio of the numbers of protonated/total N,N-dimethylaminomoieties. The tightly bound polymeric structure was formed around the nanoparticle at α = 0, whereas the loose coating wasobserved upon PDMAEMA protonation at α = 1. At partially protonated PDMAEMA (α = 0.5), the polymer chains segregate andcollapse onto the nanoparticle. In the protonated forms (α = 0.5 and 1.0), PMMA-b-PDMAEMA adsorption onto AgNPs occursprimarily through the hydrophobic PMMA block so that the protonated positively charged PDMAEMA segment favors residing inan aqueous solution. Our results demonstrate that the pH-controllable behavior of PMMA-b-PDMAEMA coating opens up theopportunity for its use as a “smart” polymeric shell for AgNPs.
... The weight of the membranes was measured every 24 h until a steady weight was achieved and finally, the degree of swelling (DoS) was measured using Eq. (2) (Romero Nieto et al., 2017). Where α is the swollen weight (g) and β is the weight of the dry membrane. ...
Biogas up-gradation is a useful method to control CO2 emission and enhance the green process. The demand for renewable sources is increasing due to the depletion of fossil fuels. Thin-film nanocomposites functionalized with tunable molecular-sieving nanomaterials have been employed to tailor membranes with enhanced permeability and selectivity. In this work, the cellulose nanocrystals as a filler in the polyvinyl alcohol matrix are prepared to achieve high-performance facilitated transport membranes for CO2 capture. Considering the mechanical stability, interfacial compatibility and high moisture uptake of the filler, the main objective of this work was to develop a novel aminated CNC (Am-CNC)/polyvinyl alcohol nanocomposite membrane for biogas upgrading. The hydroxyl groups (O–H) on the reducing end of the cellulose nanocrystals were replaced by amino groups (N–H2). It was discovered through Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) that adding Am-CNCs in PVA membranes shows an increment in the CO2 removal and effectively upgrades the biogas. The effect of change in concentration of Am-CNC and feed pressure was investigated. The results showed that with increasing Am-CNC concentration up to 1.5 wt%, the thickness of the selective membrane layer increased from 0.95 to 1.9 μm with a decrease in the moisture uptake from 85.04 to 58.84%. However, the best CO2 permeance and selectivity were achieved at 0.306 m3/m2.bar.h (STP) and 33.55, respectively. Furthermore, there was a more than two-fold decrease in CO2 permeance and a 27% decrease in the CO2/CH4 selectivity when the feed pressure increased from 5 to 15 bar. It was revealed that PVA/Am-CNC membrane is high performing for the biogas upgradation.
... It has been widely used as the fixed-site carrier in PVA membranes (Fig. 7). PVAm is generally synthesized through the Hofmann reaction, but it is also commercially available [14]. As it is water-soluble, it can be blended with PVA solution to form CO 2 selective membranes. ...
Polymeric membranes offer simple operation and high flexibility to be integrated into carbon capture, utilization, and storage (CCUS) strategies, but the solution-diffusion mechanism limits their separation performance. CO2 facilitated transport membranes have been extensively developed to increase the techno-economic potential of CCUS. Polyvinyl alcohol (PVA) membranes can be easily fabricated as the selective layer on porous support through different coating strategies. Recent works focused on various additives such as fixed amine carriers, mobile amine carriers, moiety content promoters, swelling agents, and more to improve CO2 facilitated transport through PVA membranes. The past studies focusing on PVA membranes in carbon capture included the use of different additives, which could be categorized into fixed amine carriers, mobile amine carriers, hydrophilic polymers, carbonaceous materials, inorganic particles and polyether block amide (PEBA). Adding both fixed amine carriers and mobile amine carriers could promote the CO2 separation beyond Robeson upper bound. However, the hydrophilic polymers only improved CO2 separation below Robeson upper bound. Carbon nanotubes enhanced the mechanical properties, while the functionalized graphene oxide facilitated CO2 permeation effectively. Inorganic particles such as zinc oxide, silica, and alumina offered more opportunities to improve the swelling of PVA membranes and promote CO2 separation beyond the Robeson boundary. The CO2 separation performance of PVA membranes could be enhanced by increasing the relative humidity, but severe corrosion could be induced simultaneously. Hence, future works should focus on incorporating inorganic additives with amine functionalization to PVA membranes besides studying the humidity control for promoting facilitated transport of CO2.
... The simulation results are later quantified by developing an empirical model to study gas concentrations in silica/PSF-based MMMs. This work demonstrates the advantages of molecular simulation to determine gas transport properties of sufficient accuracy in a less time-consuming and cost-effective manner, which can be used to screen, evaluate, and develop an appropriate empirical model to describe the separation performance of membranes [36]. ...
Polysulfone-based mixed matrix membranes (MMMs) incorporated with silica nanoparticles are a new generation material under ongoing research and development for gas separation. However, the attributes of a better-performing MMM cannot be precisely studied under experimental conditions. Thus, it requires an atomistic scale study to elucidate the separation performance of silica/polysulfone MMMs. As most of the research work and empirical models for gas transport properties have been limited to pure gas, a computational framework for molecular simulation is required to study the mixed gas transport properties in silica/polysulfone MMMs to reflect real membrane separation. In this work, Monte Carlo (MC) and molecular dynamics (MD) simulations were employed to study the solubility and diffusivity of CO2/CH4 with varying gas concentrations (i.e., 30% CO2/CH4, 50% CO2/CH4, and 70% CO2/CH4) and silica content (i.e., 15–30 wt.%). The accuracy of the simulated structures was validated with published literature, followed by the study of the gas transport properties at 308.15 K and 1 atm. Simulation results concluded an increase in the free volume with an increasing weight percentage of silica. It was also found that pure gas consistently exhibited higher gas transport properties when compared to mixed gas conditions. The results also showed a competitive gas transport performance for mixed gases, which is more apparent when CO2 increases. In this context, an increment in the permeation was observed for mixed gas with increasing gas concentrations (i.e., 70% CO2/CH4 > 50% CO2/CH4 > 30% CO2/CH4). The diffusivity, solubility, and permeability of the mixed gases were consistently increasing until 25 wt.%, followed by a decrease for 30 wt.% of silica. An empirical model based on a parallel resistance approach was developed by incorporating mathematical formulations for solubility and permeability. The model results were compared with simulation results to quantify the effect of mixed gas transport, which showed an 18% and 15% percentage error for the permeability and solubility, respectively, in comparison to the simulation data. This study provides a basis for future understanding of MMMs using molecular simulations and modeling techniques for mixed gas conditions that demonstrate real membrane separation.
... Therefore, the solution pH is fixed during a single MD simulation run, and its value is approximately taken into account by proper assigning of macroscopic protonation states of a macromolecule, which in turn is derived from pK a of its titratable sites. 61,72,83−86 Recently, such an approach has been applied to simulate pH-responsive conformation dynamics of single-chain oligomers and their self-assembly for poly(acrylic acid) 61,87 and poly(alkyl acrylic acids), 83,84,88−90 poly(ethylenimine), 85 poly(vinylamine), 91 and poly(arginine). 54 To simulate the polymer response to changes in pH, the required value of the degree of protonation (α) was achieved by the attachment of a proton to the nitrogen atom of the tertiary dimethylamino side group, which switches its charge from 0 to +1 (Figures 1b and 2). ...
... The latter can form hydrogen bonds but not as readily as hydroxyl groups. This is due to the asymmetric nature of the hydrogen bonding in protonated amines: that is, they are more likely to offer donors, rather than acceptors 37 . Furthermore, the PVAm hydration shell structure is likely to be affected by the net positive charge of the amine group, which contributes to explain why we observe only minimal interaction with the growing ice front for PVAm compared to PVA. ...
Understanding the ice recrystallisation inhibition (IRI) activity of antifreeze biomimetics is crucial to the development of the next generation of cryoprotectants. In this work, we bring together molecular dynamics simulations and quantitative experimental measurements to unravel the microscopic origins of the IRI activity of poly(vinyl)alcohol (PVA)—the most potent of biomimetic IRI agents. Contrary to the emerging consensus, we find that PVA does not require a “lattice matching” to ice in order to display IRI activity: instead, it is the effective volume of PVA and its contact area with the ice surface which dictates its IRI strength. We also find that entropic contributions may play a role in the ice-PVA interaction and we demonstrate that small block co-polymers (up to now thought to be IRI-inactive) might display significant IRI potential. This work clarifies the atomistic details of the IRI activity of PVA and provides novel guidelines for the rational design of cryoprotectants.
... The combination of PolyV (a PVAM based flocculant) and PAM1 or PAM2 showed increase in performance with increase in pH from 4 to 10. The phenomena behind this observation in the behavior of PVAM was investigated by Nieto and co-workers [45]. The potential energy of polyamines are higher at pH 10, due the free space formed in the untangled polymer formation. ...
... This results in high protonation at pH 4 with a high content of crystalline zone, and as pH is increased crystallinity is reduced. At pH 10 optimum partial protonation is achieved, comprising both amorphous and crystalline zones with swelling of the polymer chains [45]. It can therefore be deduced that greater stability of CPAM-PVAM mix at pH 10 was due to the morphology blend between their partially amorphous and crystalline zones, which allows effective attachment of microalgae cells. ...
Background: Dewatering constitutes a major challenge to the production of microalgae, accounting for 20-30% of the product cost. This presents a setback for the applicability of microalgae in the development of several sustainable products. This study presents an investigation into the dynamic dewatering of microalgae in a combined floccula-tion-filtration process. The effect of process conditions on the performance of 12 flocculants and their mixtures was assessed.
Results: The mechanism of flocculation via the electrostatic path was dominated by charge neutralization and subsequently followed bridging in a 'sweep flocculation' process. Cationic polyacrylamide (CPAM) based flocculants recorded the highest biomass retention with PAM1 and PAM2 attaining 99 and 98% retention with flocculant dosages of 10 and 15 mg/L respectively. Polyvinylamine (PVAM) was also found to improve system stability across the pH range 4-10. Alum was observed to be only effective in charge neutralization, bringing the system close to its isoelec-tric point (IEP). Chemometric analysis using the multi-criteria decision methods, PROMETHEE and GAIA, was applied to provide a sequential performance ranking based on the net outranking flow (ф) from 207 observations. A graphical exploration of the flocculant performance pattern, grouping the observations into clusters in relation to the decision axis (π), which indicated the weighted resultant of most favorable performance for all criteria was explored.
Conclusion: CPAM based flocculants and their mixtures demonstrated superior performance due to their viscoelas-tic behaviour under turbulence. The use of PVAM or alum in mixtures with CPAM reduced the required doses of both flocculants, which will provide beneficial financial impact for largescale microalgae dewatering in a flocculant assisted dynamic filtration process. Chemometric analysis based on the physico-chemical properties of the system provides a time saving assessment of performance across several criteria. The study findings provide an important foundation for flocculant assisted dynamic filtration processes.
... However, it reduced the free mobility of carrier but enhanced the overall stability and performance of membranes. Recently, research has been focused to make membrane material more hydrophilic to take the advantage of liquid membranes in highly swollen conditions [12][13][14][15]. The FTM that works under highly swollen conditions facilitate the CO 2 transport as bicarbonate ion (HCO 3 − ) through the membrane [16]. ...
... Day 1 measurement was taken after 24 h in which membranes were subjected from 0% RH to 87% RH. Equation (1) was used to calculate the degree of swelling [14]. ...
A novel crystalline nano cellulose (CNC) and polyvinyl amine (PVAm) based nanocomposite membranes were synthesized and evaluated for biogas upgrading. Different concentrations of CNC was incorporated in 3 wt % PVAm solution on commercial polysulfone (PSf) sheet using dip coating method. The effect of feed pressure (5, 10 and 15 bar) was investigated for the CO2/CH4 separation. The incorporation of CNC increased the crystallinity of membranes. The thickness of selective layer enhanced to 2.16 μm from 1.5 μm with increasing concentration of CNC. However, degree of swelling reduced from 75.88% to 68.93 with CNC concentration at 1.5 wt%. The best results were shown by PVAm membrane with 1 wt % CNC concentration i.e. CO2 permeance of 0.0216 m3(STP)/m2.bar.hr and selectivity (CO2/CH4) of 41.The permeance decreased approximately 1.8 folds for PVAm/1CNC membrane with the increase in pressure from 5 to 15 bar. However, selectivity dropped from 41 to 39 for formulated membranes.
... They evaluated the suitability of FSC for CO 2 transport by examining the effects of feed pressure, relative humidity, acidity of polymer solution (pH), and other factors. They found that the formation of bicarbonate, i.e., reaction (3) or (5), followed by diffusion is crucial for optimal FSC membrane performance [89][90][91][92][93][94]. Apart from their studies, facilitated transport membranes are usually used under humidified conditions. ...
Carbon dioxide capture and storage (CCS) technology is an effective CO2 fixation technology, as documented by the special report produced by Working Group III of the Intergovernmental Panel on Climate Change. Today, this technology has become important due to the threat of global warming and climate change. Furthermore, the development of carbon dioxide capture and utilization (CCU) technology, which reuses the captured CO2, has been prioritized in recent years to accelerate the deployment of “CCUS.” For both utilization and storage, CO2 capture is a key process that determines how efficiently decarbonation is able to meet the global target. Regardless of the maturity of various types of CO2 capture technologies, amines are the most widely used chemical species. This paper contains a brief overview of CCUS followed by a discussion of several aspects of amine-based CO2 capture technologies. Carbon dioxide capture and storage (CCS) technology has become important due to the threat of global warming and climate change. Furthermore, the development of carbon dioxide capture and utilization (CCU) technology, which reuses the captured CO2, has been prioritized in recent years to accelerate the deployment of “CCUS.” Amine-based CO2 capture is a key process for realizing a carbon neutral society.
... From 0 bilayer to 4 bilayers, the water contact angle reduced from 89.5°to 49.3°on stainless steel surface, 80.2°to 56.4°on PVC surface and 49.4°to 33.8°on glass surface respectively (Fig. 4b). Both PVAm and HA-DN are water-soluble polymers with high solubility around neutral pH, and the probable interactions with water molecules of these two polymers would help with confine high levels of water content at the interfacial zone [31,46], which may further improve the hydrophilicity of the surface. In addition, the improved hydrophilicity of the material surface by LbL coatings would provide possibilities for their applications in biomedical scenarios. ...
Layer-by-layer (LbL) assembly technique has been proven to be a convenient and eco-friendly method to obtain multifunctional coatings. In this research we presented a hydrophilic and transparent coating on various types of substrates by layer-by-layer deposition of polyvinylamine (PVAm) and dopamine-modified hyaluronic acid (HA-DN). The successfully constructed multilayers on gold surface were monitored by quartz crystal microbalance (QCM). The coating significantly improved the hydrophilicity of glass, stainless steel, gold, and polyvinyl chloride (PVC) surface as compared with the unmodified ones, which can reduce the water contact angle of the substrates by 30% to 45%. The growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was significantly inhibited on LbL-coated PVC, and 6 bilayers of coating can achieve nearly 100% suppression of bacterial growth. The coating was with no toxicity to mouse lymphocytes in polystyrene (PS) cell culture plate, while it significantly attenuated the viability of Michigan cancer foundation - 7 cells (MCF7) and human acute monocytic leukemia cell line (THP-1) in vitro. Therefore, this hydrophilic, transparent, antibacterial, biocompatible, and tumor-cell-suppressive coating would have broad potential in biomedical applications.
