Solvent Transport Research Articles

Model Studies on Solid Electrolyte Interphase Formation on Graphite Electrodes in Ethylene Carbonate and Dimethyl Carbonate II: Graphite Powder Electrodes

AbstractAs part of a systematic study on the formation and composition of the solid electrolyte interphase (SEI) in lithium‐ion batteries (LIBs), going stepwise from highly idealized electrodes such as highly oriented pyrolytic graphite and conditions such as ultrahigh vacuum conditions to more realistic materials and reaction conditions, we investigated the decomposition of simplified electrolytes (ethylene carbonate (EC)+1 M LiPF6 and dimethyl carbonate (DMC)+1 M LiPF6) at binder‐free graphite powder model electrodes. The results obtained from cyclic voltammetry and ex situ X‐ray photoelectron spectroscopy half‐cell measurements – in particular on the effect of cycling rate, solvent and electrode – are explained in terms of a mechanistic model where electrolyte decomposition occurs at the SEI | electrode interface and where transport of solvent and salt species through the growing SEI plays an important role for explaining the observed change from preferential salt decomposition to solvent decomposition with increasing cycling rate.

Mass Transport Models in Organic Solvent Nanofiltration: A Review

Membrane technology has been gradually used as an alternative to the conventional separation and purification method in various industries. In recent years, solvent-stable nanofiltration or organic solvent nanofiltration has becoming practicable through the development of solvent-stable commercial polymeric membranes. Organic solvent nanofiltration has a great potential to replace the conventional energy-demanding process such as distillation due to its ability of separating organic solvents and solutes on a molecular level without phase change and operation at relatively mild temperature. Predicting the performance of such membrane separations is crucial in the process design. Important performance indicator such as the permeate flux and the rejections are strongly related to the fluid dynamics, mass transfer and solute-solvent-membrane interactions. The aim of this paper is to review and assess the transport models of solute and solvent transport relevant to organic solvent nanofiltration. The link between concentration polarization and the hydrodynamics in various configurations are discussed. The effects of process variables on membrane performance and solute-solvent membrane interactions are also reviewed.

Electropolymerization of robust conjugated microporous polymer membranes for rapid solvent transport and narrow molecular sieving

Pore size uniformity is one of the most critical parameters in determining membrane separation performance. Recently, a novel type of conjugated microporous polymers (CMPs) has shown uniform pore size and high porosity. However, their brittle nature has prevented them from preparing robust membranes. Inspired by the skin-core architecture of spider silk that offers both high strength and high ductility, herein we report an electropolymerization process to prepare a CMP membrane from a rigid carbazole monomer, 2,2’,7,7’-tetra(carbazol-9-yl)-9,9’-spirobifluorene, inside a robust carbon nanotube scaffold. The obtained membranes showed superior mechanical strength and ductility, high surface area, and uniform pore size of approximately 1 nm. The superfast solvent transport and excellent molecular sieving well surpass the performance of most reported polymer membranes. Our method makes it possible to use rigid CMPs membranes in pressure-driven membrane processes, providing potential applications for this important category of polymer materials.

Analysis of non-equilibrium foamy oil flow in cyclic solvent injection processes

Non-equilibrium phase behavior (i.e., solvent dissolution/exsolution) and solvent transport are key recovery mechanisms in many non-thermal post-CHOPS (Cold Heavy Oil Production with Sand) processes, such as cyclic solvent injection (CSI), in western Canada and Venezuela. Foamy oil refers to the non-equilibrium phenomenon where gas bubbles are dispersed in the oil phase during exsolution, resulting in a decrease in oil viscosity. This is a well-recognized behavior in heavy oil primary production (CHOPS) and has implications in recovery during CSI. In this paper, a mechanistic simulation model is constructed based on a set of pressure depletion experiments, and the calibrated model is used to analyze the effects of solvent compositions and operating schedules on recovery efficiency.First, a series of pressure depletion tests are conducted using both bulk fluid systems and porous media to examine the non-equilibrium release of solvent (CO2, CH4 and C3H8) from saturated live oil during the production cycles of CSI. The non-equilibrium live oil viscosity profile is inferred from calibrated NMR measurements. Different combinations of solvent mixtures and pressure depletion rates are tested to examine their impacts of gas exsolution. Next, a detailed mechanistic simulation model is constructed and calibrated against a set of experimental measurements. A fluid model is defined based on equilibrium saturation pressures and gas-oil ratios corresponding to different combinations of solvent and dead oil. A viscosity model is formulated using measurements at different temperatures and solvent-oil mixtures. Reaction kinetics is implemented to represent the non-equilibrium exsolution of gas from solution gas to bubble gas and free gas in foamy oil flow.The simulation model shows the response of viscosity and oil production as a function of pressure for a porous medium saturated with live oil in a single depletion cycle. The model predicts a delay in free gas formation in the sand pack, as observed in the experimental program. Propane-based and carbon dioxide-based solvent mixtures exhibit significant foamy oil characteristics, enabling the oil viscosity to remain close to its live oil value even with pressures that are much lower than saturation pressure. The rates of gas exsolution and oil production are strongly dependent on the pressure depletion schedule, as well as the solvent compositions and properties.Although a number of models were developed in the past to describe the dissolution of solvent and bubble formation, calibration of these models against actual observations remain challenging. The model developed in this study is calibrated and corroborated by detailed experimental observations; hence, it can be further scaled up to study recovery performance at the pilot or field scales. Many existing solvent technologies suffer from low production rates due to limited solvent/heavy oil interaction. Improving our understanding of solvent dissolution/exsolution under different pressure conditions would aid in the design of operating strategies (e.g., pressure depletion and solvent injection schemes) for enhanced solvent/oil mixing and transport.

Molecular Dynamics Simulations of Channelrhodopsin Chimera, C1C2.

Molecular dynamics (MD) simulations have been successfully used for modeling dynamic behavior of biologically relevant systems, such as ion channels in representative environments to decode protein structure-function relationships. Protocol presented here describes steps for generating input files and modeling a monomer of transmembrane cation channel, channelrhodopsin chimera (C1C2), in representative environment of 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) planar lipid bilayer, TIP3P water and ions (Na+ and Cl-) using molecular dynamics package NAMD, molecular graphics/analysis tool VMD, and other relevant tools. MD simulations of C1C2 were performed at 303.15K and in constant particle number, isothermal-isobaric (NpT) ensemble. The results of modeling have helped understand how key interactions in the center of the C1C2 channel contribute to channel gating and subsequent solvent transport across the membrane.

Synthesis and Characterization of ZnO Nanoparticles and Their Natural Rubber Composites

Nanoparticles of zinc oxide were synthesized by a solution combustion method. The average size of these particles was analyzed by using X-ray diffraction. Composites of natural rubber and the ZnO nanoparticles were prepared by a latex blending method. The matrix phase was cured by using the crosslinking agent, pentane-1,5-diylidenediamine. Effects of crosslinking and incorporation of nanoparticles on the tensile and solvent transport properties of the natural rubber were studied in detail. The nature of the dispersion of the nanoparticles was analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). It was observed from the tensile studies that the addition of the curing agent and the ZnO nanoparticles increased the stability considerably. Incorporation of the nanoparticles also considerably increased the solvent resistance of the cured natural rubber. We suggest the addition of ZnO nanoparticles at a low loading level provided better properties compared to other reinforcements, such as carbon black and nano-clay.

Robust numerical solution for the two parameter solute solvent transport model

Prediction of solute and solvent transport in cells is central to developing and testing cryopreservation protocols. As we show here, however, the models used can be difficult to accurately numerically integrate in some key cases, and thus are a challenge to implement when determining the time dependent cell state during cryoprotectant equilibration and cooling. Exact solution techniques exist for overcoming this problem, but their implementation is also challenging: inversion of a nonlinear function is required that negates much of the utility of the approach. This communication describes a simple approach for more robust numerical integration that can be implemented using any numerical differential equation solver, and can facilitate arbitrarily accurate solutions to transport models without the complication of inversion formulae or complicated numerical integration schemes. Further, a simple relevant example of red blood cell equilibration with 40% glycerol is presented with comments on extending the approach to other settings.

The effect of additive supporting electrolytes on transport and electrochemical properties of deep eutectic solvent (DES) applied in non-aqueous redox flow batteries

Although the utilization of deep eutectic solvents (DES) as non-aqueous electrolyte of redox flow batteries has received enormous attention, its properties like high viscosity and low conductivity always remain a matter of concern, due to their negative effect on final battery power performance. Herein, the introduction of two types of additive supporting electrolytes (one: a mixture of dimethyl carbonate (DMC) and ethylene carbonate (EC) and the other: ethyl acetate (EA)) remarkably decreasing the viscosity and impedance of the DES with iron ions is reported, especially for DMC+EC. In addition, the cyclic voltammetry results show that the reversibility of Fe(III)/Fe(II) redox couple, and the reaction kinetics are improved after adding DMC+EC, while EA has little effect on improving the electrochemical performance. From Raman spectroscopy, it is found that a distinct characteristic peak occurs at 895 cm−1 for DMC+EC mixture, whereas the intensity of this peak is weak for EA. It is highly probable that the appearance of this characteristic peak serves to improve the electrochemical properties of DES.

Natural graphite reinforced fluoroelastomer composites: Morphological, mechanical, thermal, dielectric, and solvent transport studies

AbstractFluoroelastomer (FKM) composite embedded with natural graphite (NG) was prepared and its thermal, mechanical, dielectric, and solvent transport properties were explored as a function of NG loading. The morphology of the composites was done by AFM, SEM, and TEM analysis, and XRD provides the structural analysis. The composite with 20 phr of NG content showed the highest tensile properties and thermal stability and was supported by fracture surface SEM analysis. Enhancement in polymer‐filler interaction in the composite was further confirmed by the increase in Tg value obtained from DSC analysis. The dielectric permittivity value showed tremendous increment by 30 phr of NG addition with decreased dielectric loss. The resistance to solvent uptake with increase in NG loading by the formation of tortuous pathway is also a clear evidence for the exfoliation of the graphite flakes in the FKM matrix. Better inclusion of NG in FKM matrix efficiently enhanced the thermal, mechanical, dielectric and the transport properties of the composites.

Functional macroporous amphoteric polyelectrolyte monoliths with tunable structures and properties through emulsion-templated synthesis

HypothesisMacroporous polyampholyte hydrogels, simultaneously bearing both the anionic and cationic groups, demonstrate immense promise over the one-sign charged polyelectrolytes, owing to a unique phenomenon known as the ˝anti-polyelectrolyte˝ effect. Thus, they are extremely promising materials, since they remain solvated and functional even in harsh conditions. Furthermore, macroporous morphology significantly enhances polyampholyte response to external stimuli, since it accelerates the solvent transport through the hydrogel. ExperimentsA new templated-synthesis through “HIPE mixtures” is reported, where the two pre-formed high internal phase emulsions (HIPE) containing the oppositely charged monomers (2-acrylamido-2-methyl-1-propanesulfonic acid and (3-acrylamidopropyl)trimethylammonium chloride) were combined in the same mould, which after polymerization result in the formation of macroporous monoliths of different structures. The resulting frameworks were either copolymer or dual homopolymers in the form of bilayered or mixed porous structures. FindingsThe co– and mixed-amphoteric polyelectrolytes exhibit 'anti-polyelectrolyte' behaviour typical of polyampholytes, while the bilayered-structure behaves like a typical polyelectrolyte. Complete and simultaneous removal of both dyes from a dye mixture was observed for the bilayered- and mixed-amphoteric polyelectrolyte, while copoly-ampholyte showed only partial dye adsorption. These results clearly reveal the benefits of a mutual combination of the HIPE-templated structure and the oppositely charged amphoteric nature in one-piece material as a promising avenue toward advanced materials.

Evaluation of different nebulizers performance on microwave-induced plasma optical emission spectrometry

The choice of an adequate nebulizer reflects directly in the accuracy, especially when a complex matrix is analyzed in plasma techniques. To unveil the effects on fundamental parameters and analytical performance of a microwave-induced plasma optical emission spectrometry, four commercial nebulizers, Concentric, Mira Mist, OneNeb series 1, and OneNeb series 2, were evaluated. Estimated fundamental plasma parameters, excitation temperature (T), and the number of electron density (ne) indicated that the Mira Mist nebulizer afforded a plasma with the highest T and ne, but the lowest solvent transport efficiency. OneNeb series 2 showed the lowest T and ne, nonetheless the highest solvent transport efficiency. The precision was estimated in the middle of nitric acid (1% v v-1), sulfuric acid (1% v v-1), easily ionizable elements (100 mg L-1 of Ba, K, and Na), ethanol (1% v v-1), and carbon content (1000 mg L-1). The OneNeb series 2 presented the lowest RSD and LOD values in all matrices, while the concentric presented the highest RSD. The accuracy was evaluated by certified reference materials and addition and recovery experiments performed in sugarcane spirit. Considering the sensitivity improvement, solvent transport efficiency and analytical precision the OneNeb series 2 achieved superior performance.

Highly sensitive chemosensor for detection of methamphetamine by the combination of AIE luminogen and cucurbit[7]uril

Methamphetamine (METH) abuse has become a global problem, and new strategies for rapid and sensitive detection of METH are in urgent need. Herein, a novel technique is developed for highly sensitive detection of METH in solution with a broad concentration range by the assembly of AIE luminogen of tetrakis(4-(pyridin-4-yl)phenyl)ethene (TPPE) and cucurbit[7]uril (CB[7]). The 1H NMR and isothermal titration calorimetry (ITC) characterizations confirm that TPPE and CB[7] are self-assembled in a ratio of 1:4. While, the interaction of CB[7] with METH exhibits a binding ratio of 1:1 and stronger binding ability than with TPPE. Based on the competitive binding affinity, CB[7]⊃TPPE could be used as a chemosensor to detect METH in solution, which exhibits remarkable advantages such as rapid response, high sensitivity and low limit of detection (LOD). When the concentration of METH solution is larger than 40 μM, the enhancement of fluorescence intensity and change of fluorescent colour could be directly observed upon UV irradiation. When the METH solution concentration is higher than 10 μM, we can use our fabricated test strips to rapidly and visibly detect. If above detections do not work, we can measure the photoluminescence (PL) spectra of the sensing system, which shows a LOD as low as 0.43 μM. This unique CB[7]⊃TPPE based chemosensor is potentially applicable in real-time and visual detection of METH in solution and provides a powerful platform for preventing chemical solvent transport.

Phase separation in swelling and deswelling hydrogels with a free boundary.

We present a full kinetic model of a hydrogel that undergoes phase separation during swelling and deswelling. The model accounts for the interfacial energy of coexisting phases, finite strain of the polymer network, and solvent transport across free boundaries. For the geometry of an initially dry layer bonded to a rigid substrate, the model predicts that forcing solvent into the gel at a fixed rate can induce a volume phase transition, which gives rise to coexisting phases with different degrees of swelling, in systems where this cannot occur in the free-swelling case. While a nonzero shear modulus assists in the propagation of the transition front separating these phases in the driven-swelling case, increasing it beyond a critical threshold suppresses its formation. Quenching a swollen hydrogel induces spinodal decomposition, which produces several highly localized, highly swollen phases which coarsen and are then ejected from free boundary. The wealth of dynamic scenarios of this system is discussed using phase-plane analysis and numerical solutions in a one-dimensional setting.

Highly Ordered and Dense Thermally Conductive Graphitic Films from a Graphene Oxide/Reduced Graphene Oxide Mixture

Summary We report a new approach to making highly dense, oriented, and crystalline graphite films from heat-treated and pressed graphene oxide (G-O). By introducing small-diameter reduced graphene oxide (rG-O) flakes into the graphene oxide starting material, we found that after heat treatment at 3,000°C, the sample density and atomic order substantially improved over a film composed, at the outset, only of pure G-O flakes. A subsequent mechanical press increased the density but reduced the atomic order. A second 3,000°C heat treatment restored the graphitic structure with graphitization metrics exceeding even those of the first heat treatment. The optimized graphitic film with an original concentration of 15 wt % reduced G-O in G-O gave well-oriented graphitic films with a density of 2.1 g cm−3, cross-plane thermal conductivity of 5.65 W m−1 K−1, and in-plane thermal conductivity of 2,025 ± 25 W m−1 K−1.

Fundamental origin of flux non-linearity in organic solvent nanofiltration: Formulation of a thermodynamic/diffusion framework

In this paper we critically discuss the hypothesis of membrane compaction under pressure, which has been invoked to explain solvent flux vs. Δp non-linearity in organic solvent nanofiltration (OSN) experiments with dense polymer membranes. Although physically sound, this hypothesis does not have experimental support. To demonstrate that the molecular origin of flux non-linearity is purely thermodynamic, we propose a thermodynamic-diffusion framework which describes solvent transport in OSN membranes in terms of the concentration gradient produced by the applied pressure across the membrane. Solvent diffusion coefficient in the membrane increases with increasing Δp, which further confirms that flux decline is not related to membrane compaction. The developed framework allows to quantify both frame of reference and non-ideal thermodynamic effects on solvent diffusion coefficients in OSN membranes. This study demonstrates that the solution-diffusion model, if properly corrected for frame of reference (i.e., convection) and non-ideal effects, provides a satisfactory description of small molecule transport in OSN membranes, without the need to resort to more complicated transport models.

Influence of exfoliated graphite inclusion on the thermal, mechanical, dielectric and solvent transport characteristics of fluoroelastomer nanocomposites

Nanocomposites with multifunctional properties are of great interest as they meet the needs of the developing industrial and engineering fields. The present study focus on the development of multifunctional elastomeric nanocomposites with exfoliated graphite (EG) as the reinforcing content and the speciality material fluoroelastomer as the polymer matrix. Morphological analysis of the nanocomposites in terms of TEM, AFM and SEM were done to look at the polymer-filler interactions which in turn lead to the property enhancement. The dispersion of the EG in the nanoscale which resulted in the property enhancement is clear from the TEM images. Nanocomposites exhibited improved thermal stability and higher mechanical strength by the addition of 12 phr of EG nanofiller. Moreover the dielectric performance of the nanocomposites was also enhanced by the addition of conductive EG nanofiller and the nanocomposites showed higher dielectric constant value and AC conductivity with lower dielectric loss. In addition to this the solvent transport features of the nanocomposites were also analyzed to reveal the reinforcement effect of the nanofiller and the effective polymer-filler interactions.

Experimental and theoretical evaluation of mechanical, thermal and morphological features of EVA-millable polyurethane blends

Heterogeneous blends of millable polyurethane (MPU) and ethylene-co-vinyl acetate (EVA) elastomers have been prepared by conventional open mill mixing, and subsequently cured with DCP as curing agent. The prepared blends were characterized by TGA, DSC, XRD and DMA techniques. Mechanical and solvent transport features have been evaluated. Examination of EVA phase crystallization dynamics revealed that the 50:50 blend possessed a higher energy barrier during crystallization. When EVA became the minor or major phase, the system offers similar energy barrier features. Solvent transport mechanism has been found to shift towards non-Fickian for blends with EVA as the major phase. Mechanical properties have been found to be complementary to the observed crystalline features of the blends. A blend with EVA to MPU ratio 80:20 is highlighted as a soft and strong material, with enhanced solvent resistance features suitable as a matrix for different engineering applications.

Spatial light-modulated stimulated Raman scattering (SLM-SRS) microscopy for rapid multiplexed vibrational imaging

High speed imaging is pre-requisite for monitoring of dynamic processes in biological events. Here we report the development of a unique spatial light-modulated stimulated Raman scattering (SLM-SRS) microscopy that tailors the broadband excitation beam with sparse-sampling masks designed for rapid multiplexed vibrational imaging to monitor real-time cancer treatment effects and in vivo transport of drug solvent.Methods: We design an optimal mask pattern that enables selection of predominant windows in SRS spectrum for collective excitation at the highest possible peak power, thus providing an improved signal-to-noise ratio (SNR) without compromise of chemical specificity. The mask pattern generated is applied to the broad excitation beam using a flexible spatial light modulator. The SLM module further offers complementary function whereby rapid scanning of SRS spectrum can be facilitated prior to the mask generation, thereby making the SLM-SRS system a stand-alone imaging platform.Results: We demonstrate that SLM-SRS microscopy permits rapid multiplexed SRS imaging of polystyrene and polymethyl methacrylate beads in Brownian motion in dimethyl sulfoxide (DMSO) at 70 ms intervals without motion artiacts. We further apply SLM-SRS to monitor the therapeautic effect of mild alkaline solution on cancer cells, which shows immediate apoptotic response. Finally, we visualize in vivo penetration of DMSO into the plant tissue and evaluate acute toxicity of DMSO on cellulose and proteins within the tissue.Conclusion: We develop novel SLM-SRS microscopy and affirm its broad applicability for rapid monitoring of dynamic biological processes at the subcellular and molecular level.

Contaminants of Dispersion on Groundwater by Landfill Leachate

The major potential impacts of landfill leachate on the environment are groundwater and surface water contamination.To date, the percolation of bacteria and viruses by landfill leachate into the groundwater table poses a potential risk to public health and the environment and potential risks.This pa per deals with the study of leachate dispersion of contaminants us ing generalized dispersion techniques for solvent transport in por ous media.The porous layer interface, the slip boundary conditio ns of the beavers joseph bj are used, the governing equations are analytically solved and the expressions for speed and dispersion a re obtained and graphically presented

The encouraging improvement of polyamide nanofiltration membrane by cucurbituril‐based host–guest chemistry

AbstractThe considerable performance enhancement of small molecule‐sieving nanofiltration membrane has been achieved by the functional combination between host–guest chemistry and interfacial polymerization (IP) for the first time in this work. First, the water‐insolubility of cucurbit[6]uril (CB6) was ameliorated by constructing host–guest complex (CB6‐PIP) with piperazine. Second, the incorporation of water‐soluble CB6‐PIP in the selective layer via IP leads to the generation of not only the enlarged conventional polyamide network tunnels but also rotaxane tunnels. Such enrichment of solvent transport tunnels contributes to an amazing pure water permeability of 15.5–25.4 Lm−2bar−1h−1, three times higher than that of traditional polyamide membranes, with a high R/MgSO4 of 99.5–92.5%, perfect SO42−/Cl− selectivity due to the electronegative contribution of CB6, as well as untapped potential in organic solvent nanofiltration. This work not only provides a fire‐new strategy to design new type of NF materials but also promotes the application of CBs in many other fields.