Diffusion Of Acetic Acid Research Articles

A colorimetric method for quantitative visualization of diffusion and internal circulation in liquid–liquid two-phase flow

Herein, we propose a new method for the quantitative evaluation of mass-transfer characteristics in liquid–liquid two-phase flow during the formation of slug and its progression in a microchannel. The experimental setup included a 0.3-mm square microchannel with a Y junction. Distilled water with pH indicator and cyclohexane containing acetic acid were selected as the probe fluids. The acetic-acid concentrations were 0.05 and 0.1 vol%, while the volumetric velocity of the aqueous and organic phases was 0.03 mL/min. Acetic-acid diffusion and its internal circulation in the aqueous slug were visualized by color changes and recorded as microscopically magnified video images. By adopting a deep-learning algorithm, the aqueous slugs were segmented, and a calibration method converted color information to acetic-acid concentration values. The experimental results were comparable with those of previous studies. The presented method also revealed several new features that could not have been observed quantitatively by established experimental methods.

The Role of Sch9 and the V-ATPase in the Adaptation Response to Acetic Acid and the Consequences for Growth and Chronological Lifespan.

Studies with Saccharomyces cerevisiae indicated that non-physiologically high levels of acetic acid promote cellular acidification, chronological aging, and programmed cell death. In the current study, we compared the cellular lipid composition, acetic acid uptake, intracellular pH, growth, and chronological lifespan of wild-type cells and mutants lacking the protein kinase Sch9 and/or a functional V-ATPase when grown in medium supplemented with different acetic acid concentrations. Our data show that strains lacking the V-ATPase are especially more susceptible to growth arrest in the presence of high acetic acid concentrations, which is due to a slower adaptation to the acid stress. These V-ATPase mutants also displayed changes in lipid homeostasis, including alterations in their membrane lipid composition that influences the acetic acid diffusion rate and changes in sphingolipid metabolism and the sphingolipid rheostat, which is known to regulate stress tolerance and longevity of yeast cells. However, we provide evidence that the supplementation of 20 mM acetic acid has a cytoprotective and presumable hormesis effect that extends the longevity of all strains tested, including the V-ATPase compromised mutants. We also demonstrate that the long-lived sch9Δ strain itself secretes significant amounts of acetic acid during stationary phase, which in addition to its enhanced accumulation of storage lipids may underlie its increased lifespan.

Diffusion of acetic acid, butyric acid, and butanol in compacted montmorillonite

Diffusion of acetic acid, butyric acid, and butanol in compacted montmorillonite

Performance of PV modules using co-extruded backsheets based on polypropylene

Due to the general price pressure PV modules experienced in the last decade, a variety of alternative polymer materials and new backsheet designs were developed and introduced into the market, amongst others also extruded backsheets based on polypropylene (PP). The production of co-extruded films represents a backward integration of backsheet manufacturers, allowing for easy material and design modifications regarding additive formulation, fillers and geometry. The main objective of this paper was to describe the influence of the special properties of PP-based backsheets on the performance and reliability of PV modules. The higher reflectance of the PP backsheet compared to a reference polyester (PET) based laminate led to an increase in power output between 1.5 and 2.5%. Test modules using PP and PET backsheets were exposed to 3000 h of damp heat testing. No changes in power output for either of the test modules was observed. However, the selective permeation properties of PP backsheets prevent humidity from entering the module (similarly to PET based backsheets) but allow for significantly higher diffusion of acetic acid out of the PV module. Therefore, in contrast to test modules using Ethylene Vinyl Acetate (EVA) encapsulants and PET backsheets, no silver grid corrosion was observed for modules using PP backsheets. Co-extruded backsheets based on PP show great potential to be a valid replacement of standard PET based backsheets in PV modules. On the one hand, the PP backsheet so far proved excellent stability, exhibiting no severe material degradation after extended exposure to temperature, humidity and irradiation. On the other hand, its improved functional properties (optical properties; selective permeability) lead to increased performance and improved long-term stability of the tested PV modules.

Durable crystalline silicon photovoltaic modules based on breathable structure

The long-term durability of crystalline silicon (c-Si) photovoltaic (PV) modules was investigated by long-term damp-heat (DH) tests at 85 °C with 85% relative humidity. Breathable module structure using front or rear materials with low-barrier properties markedly improved the long-term DH resistance of c-Si PV modules. No corrosion of finger electrodes on c-Si solar cells occurred by diffusion of acetic acid, which was formed from an encapsulant of a random copolymer of ethylene and vinyl acetate (EVA) towards the outside of the modules by the breathable structure. Raman spectroscopy data indicated that degradation of the EVA encapsulants including additives (e.g. UV absorber) were suppressed by the usage of a breathable front film compared to a front cover glass used for the conventional modules. The breathable modules based on low-barrier components would improve the long-term photochemical and chemical durability of c-Si PV modules further to achieve 40 year operation.

Impact of tumbling operating parameters on salt, water and acetic acid transfers during biltong-type meat processing

This study investigated the impact of tumbling on mass transfer mechanisms occurring in small beef meat pieces during biltong production, by measuring salt, water and acetic acid profiles within the meat for different experimental tumbling conditions. Tumbling conditions significantly impacted the solute concentration profiles, except for that of water. Values of both salt and acetic acid diffusion coefficients obtained clearly showed that tumbling increased solute transfers inside meat, with diffusion coefficient values ranging from 2 to 27 × 10−9 m2 s−1 and from 0.2 to 8.6 × 10−9 m2 s−1, respectively. The tumbling mechanical effect related to the device used impacted the most on mass transfers (p-value<0.01 for salt and acetic acid diffusion), followed by tumbling time (p-value<0.01 for salt and acetic acid diffusion), and to a lesser extent, the use of vacuum (p-value<0.01 for salt diffusion and p-value<0.05 for acetic acid diffusion). Further studies should define the best salt and acid concentration profiles generated when tumbling, so as to obtain the best trade-off between good sanitary protection of meat and a sufficiently tender and organoleptically acceptable end-product after the final drying operation.

Alcohols enhance the rate of acetic acid diffusion in S. cerevisiae: biophysical mechanisms and implications for acetic acid tolerance.

Microbial cell factories with the ability to maintain high productivity in the presence of weak organic acids, such as acetic acid, are required in many industrial processes. For example, fermentation media derived from lignocellulosic biomass are rich in acetic acid and other weak acids. The rate of diffusional entry of acetic acid is one parameter determining the ability of microorganisms to tolerance the acid. The present study demonstrates that the rate of acetic acid diffusion in S. cerevisiae is strongly affected by the alcohols ethanol and n-butanol. Ethanol of 40 g/L and n-butanol of 8 g/L both caused a 65% increase in the rate of acetic acid diffusion, and higher alcohol concentrations caused even greater increases. Molecular dynamics simulations of membrane dynamics in the presence of alcohols demonstrated that the partitioning of alcohols to the head group region of the lipid bilayer causes a considerable increase in the membrane area, together with reduced membrane thickness and lipid order. These changes in physiochemical membrane properties lead to an increased number of water molecules in the membrane interior, providing biophysical mechanisms for the alcohol-induced increase in acetic acid diffusion rate. n-butanol affected S. cerevisiae and the cell membrane properties at lower concentrations than ethanol, due to greater and deeper partitioning in the membrane. This study demonstrates that the rate of acetic acid diffusion can be strongly affected by compounds that partition into the cell membrane, and highlights the need for considering interaction effects between compounds in the design of microbial processes.

Study on snail trail formation in PV module through modeling and accelerated aging tests

In recent years, a defect on the surface of photovoltaic (PV) modules called ‘snail trails’ has become a widespread reliability issue, affecting many modules installed in the field. In this work, silver acetate is identified as one component of snail trails through non-destructive Raman analysis. The chemical reaction between the silver grid line, oxygen and acetic acid on top of the micro-crack is proposed as the mechanism. The generation and/or diffusion of acetic acid released from ethylene vinyl acetate (EVA) encapsulant, oxygen and moisture are modeled using finite element method to predict the formation of silver acetate. The simulation results indicate that the existence of micro-crack plus cell gap are necessary for snail trail formation and act as the pathway for transport. As the source of acetic acid, encapsulant plays an important role in snail trail formation. Oxygen transmission rate of backsheet also has significant influence on snail trail formation. Water vapor transmission rate is shown to have no effect on snail trials over a wide rate of transmission rates. An accelerated aging snail trail test has been developed that can simulate snail trails within days, and is compared to modeling and field results.

Integrated Forest Biorefinery Applied to a CTMP Process: Pre-Extraction of Acetic Acid

Acetic acid is one of the promising bio-products following the Value Prior to Pulping (VPP) concept, which is one of the options for Integrated Forest Biorefinery. In a typical chemi-thermo-mechanical pulping (CTMP) process, the chemical pre-treatment may be retrofitted into the pre-extraction stage. The potential of pre-extraction of acetic acid under the conditions similar to a CTMP process was evaluated in this study. The pre-extraction yield of acetic acid increased with the increase of cooking time and temperature. The maximum acetic acid yield was 31.25% at 150°C and 60 min after the cooking in an M/K digester. The pre-extraction yield increased to 42.05% after the cooked chips were broken down into pulp fibers, indicating that some of the released acetic acid was trapped inside the wood chips and a post-mechanical treatment could enhance the diffusion of acetic acid to the liquid phase. Keywords: Acetic acid, CTMP, Forest biorefinery, Pre-extraction, Sulfuric acid, VPP.

Acetic Acid Fermentation ofAcetobacter pasteurianus: Relationship between Acetic Acid Resistance and Pellicle Polysaccharide Formation

Acetobacter pasteurianus strains IFO3283, SKU1108, and MSU10 were grown under acetic acid fermentation conditions, and their growth behavior was examined together with their capacity for acetic acid resistance and pellicle formation. In the fermentation process, the cells became aggregated and covered by amorphous materials in the late-log and stationary phases, but dispersed again in the second growth phase (due to overoxidation). The morphological change in the cells was accompanied by changes in sugar contents, which might be related to pellicle polysaccharide formation. To determine the relationship between pellicle formation and acetic acid resistance, a pellicle-forming R strain and a non-forming S strain were isolated, and their fermentation ability and acetic acid diffusion activity were compared. The results suggest that pellicle formation is directly related to acetic acid resistance ability, and thus is important to acetic acid fermentation in these A. pasteurianus strains.

Co-adsorption of acetic acid and nitrous acid on ice

The co-adsorption of acetic and nitrous acids was investigated in a packed ice bed flow tube at atmospheric pressure in the temperature range of 213-243 K. The uptake of acetic acid (CH3COOH) on ice was probed by means of a chemical ionisation quadrupole mass spectrometer. For the interaction of HONO with ice, molecules labelled with the short-lived radioisotope 13N (t1/2 = 10 min) were used. First, the retention time of acetic acid in the packed ice beds was measured in the absence of HONO and used to calculate the linear partition coefficient, K(Lin,C,AA) and the dimensionless adsorption partition coefficient, K0(p,AA). The temperature dependence of KLin,C,AA was found to be K(Lin,C,AA)[m] = 1.9 x 10(-14) exp(7.4 x 10(3)/T) in good agreement with previous studies. No evidence of diffusion of acetic acid in the bulk of the ice matrix was observed. The co-adsorption measurements are well reproduced by a competitive Langmuir adsorption model and showed that the partition coefficients derived for single compounds can also be applied to this more complex system. Further, the measurements revealed that the bulk uptake of HONO is not influenced by the presence of acetic acid. The results are discussed in terms of partitioning of trace gases in snowpacks.

Escherichia coli and Salmonella enterica are protected against acetic acid, but not hydrochloric acid, by hypertonicity.

Chapman et al. (B. Chapman, N. Jensen, T Ross, and M. B. Cole, Appl. Environ. Microbiol. 72:5165-5172, 2006) demonstrated that an increased NaCl concentration prolongs survival of Escherichia coli O157 SERL 2 in a broth model simulating the aqueous phase of a food dressing or sauce containing acetic acid. We examined the responses of five other E. coli strains and four Salmonella enterica strains to increasing concentrations of NaCl under conditions of lethal acidity and observed that the average "lag" time prior to inactivation decreases in the presence of hydrochloric acid but not in the presence of acetic acid. For E. coli in the presence of acetic acid, the lag time increased with increasing NaCl concentrations up to 2 to 4% at pH 4.0, up to 4 to 6% at pH 3.8, and up to 4 to 7% (wt/wt of water) NaCl at pH 3.6. Salmonella was inactivated more rapidly by combined acetic acid and NaCl stresses than E. coli, but increasing NaCl concentrations still decreased the lag time prior to inactivation in the presence of acetic acid; at pH 4.0 up to 1 to 4% NaCl was protective, and at pH 3.8 up to 1 to 2% NaCl delayed the onset of inactivation. Sublethal injury kinetics suggest that this complex response is a balance between the lethal effects of acetic acid, against which NaCl is apparently protective, and the lethal effects of the NaCl itself. Compared against 3% NaCl, 10% (wt/wt of water) sucrose with 0.5% NaCl (which has similar osmotic potential) was found to be equally protective against adverse acetic acid conditions. We propose that hypertonicity may directly affect the rate of diffusion of acetic acid into cells and hence cell survival.

Deactivation and regeneration of an activated carbon-supported nickel catalyst for methanol carbonylation in the vapor phase

Abstract The stability, deactivation and regeneration of a Ni/AC catalyst for methanol carbonylation in the vapor phase were studied. The results revealed that deactivation was mainly caused by carbon deposition and an increase in Ni particle size. Limitation of the internal diffusion of acetic acid and/or methyl acetate was confirmed by Py-FTIR, as could explain the slow deactivation observed in the initial stage of the reaction. Further study revealed that the deactivated catalyst was easily regenerated in H2 flow at 400 °C. The deactivation of regenerated catalyst occurred more rapidly due to the bigger Ni particle size.

Diffusion of Acetic Acid Across Oil/Water Interface in Emulsification-Internal Gelation Process for Preparation of Alginate Gel Beads

Abstract Alginate has been widely used in cell microencapsulation and drug delivery systems in the form of gel beads or microcapsules. Although an alternative novel emulsification-internal gelation technology has been established and both the properties and the potential applications of the beads in drug delivery systems have been studied, the mechanism has not been well understood compared with the traditional droplet method (external gelation technology). On the basis of our previous knowledge that the novel technology is composed of complicatedly consecutive processes with multistep diffusion and reaction, and the diffusion of acetic acid across oil/water interface being the prerequisite that determines the occurrence and rate for the reactions and the structures and properties of final produced gel beads, a special emphasis was placed on the diffusion process. With the aid of diffusion modeling and simple experimental design, the diffusion rate constant and diffusion coefficient of acetic acid across oil/water interface were determined to be in the orders of magnitude of 10 −6 and 10 −16 , respectively. This knowledge will be of particular importance in understanding and interpreting the formation, structure of the gel beads and the relationship between the structure and properties and guiding the preparation and quality control of the gel beads.

Preparation of novel composite membranes for the pervaporation separation of water–acetic acid mixtures

Novel composite membranes were prepared involving “class I” and “class II” hybrid materials. The membranes obtained were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Membranes exhibited a remarkable increase in degree of swelling with increasing zeolite loading in “class II” hybrid material. The pervaporation performance of these membranes for the separation of water–acetic acid mixtures was investigated in terms of feed composition and zeolite loading. Both the permeation flux and selectivity increased simultaneously with increasing zeolite content in the membrane matrix. This was explained on the basis of enhancement of hydrophilicity, selective adsorption and the establishment of molecular sieving action. While assessing the membranes’ efficiency, it was noticed that both total flux and flux of water are overlapping each other, signifying that the membranes developed in the present study involving “class I” and “class II” are highly selective towards water. Among the membranes developed, the membrane containing 15 mass% of zeolite exhibited the highest separation selectivity of 2423 with a flux of 8.35 × 10 −2 kg/m 2 h for 10 mass% of water in the feed at 30 °C. Comparison was also made to justify the efficiency of the developed membranes with respect to efficiency of the membranes reported in the literature. From the temperature dependent diffusion and permeation values, the Arrhenius activation parameters were estimated. The resulting activation energy values obtained for water diffusion being lower than those of acetic acid diffusion values, suggest that the composite membranes exhibit higher separation efficiency. The negative heat of sorption values (Δ H s) obtained for all the membranes, suggesting that Langmuir's type of sorption is predominant in the process.

Physical and Chemical Changes in Anchovy (Engraulis anchoita) Flesh During Marination

ABSTRACT In this work the physical and chemical changes promoted by the marinating process in anchovy fillet during brining and marinating stages were studied. During the marinating stage a diffusion of acetic acid and sodium chloride takes place into the tissue of fish flesh until a balanced concentration is reached. Most changes in the components of the fillet occurred in the first 24 hours being called by the authors “variable grade period” in contrast with “constant grade period” that occurred at the end of the marinating process. The sensorial score of full marinating was reached at nine days, when the structural changes had concluded.

Diffusion of electrolytes in hydrolyzable glassy polymers: Acetic acid in poly(vinyl acetate), poly(vinyl alcohol), and polyesters

AbstractEngineering materials containing poly(vinyl acetate) (PVAc) as the key component undergo hydrolytic degradation, which must be minimized or, at least, controlled. To characterize PVAc hydrolysis quantitatively, the diffusion of acetic acid (HAc) in PVAc, poly(vinyl alcohol) (PVA), unsaturated polyester (UPE), and a UPE/PVAc blend was studied in detail. The permeability cell earlier developed by the authors was modified here to reduce experimental error. As the diffusion and solubility coefficients of water and HAc in the above materials were measured at different temperatures, a mathematical model was developed, which takes proper account of the combined water and HAc diffusion in PVAc undergoing partial hydrolysis. The model was further validated by the experimental data obtained at 70°C for UPE/PVAc film, simulating a matrix of sheet‐molding compounds composite materials. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1157–1166, 2002

Acetic Acid Diffusion in Polyisobutylene: Probing Small Molecule Structures

In this study, time-resolved Fourier transform infrared, attenuated total reflectance (FTIR-ATR) spectroscopy was used to characterize the diffusion of acetic acid in polyisobutylene (PIB) at different vapor activities in order to understand complex diffusion mechanisms and probe molecular structures. The relationship between the carbonyl (C=O) stretch at 1715 cm -1 , which represents a cyclic dimer, and an unknown structure at 1726 cm -1 was investigated during the diffusion process to determine the structure of the unknown species. A local equilibrium association model suggested that the unknown species was a linear dimer in equilibrium with the cyclic dimer. A mathematical model for diffusion with isomerization, assuming local equilibrium, predicted that each species would have the same effective diffusion coefficient, but the individual diffusion coefficients could not be separated from the expression for the effective diffusion coefficient. Numerical simulations of the two coupled continuity equations were performed to show that the individual diffusion coefficients can be separated and that they are equal to each other for the acetic acid/PIB system. The values of the individual diffusion coefficients are consistent with the structural hypothesis from the local equilibrium assumption.

Diffusion of acetic acid and water through poly(vinylalcohol) membranes. Coupling effects

Permeation fluxes of water and acetic acid from water-acetic acid mixtures were independently monitored as a function of time in differential permeation with dual detection. Two successive permeation waves were detected for water permeation and only one for acetic acid permeation in the transient regime. The onset of the second permeation wave for water coincides with that of acetic acid permeate whatever the condition. The time delay for the appearance of these waves decreases with increasing temperature and water content in the binary mixtures. The mean diffusion coefficient for different permeation waves and their activation energy were calculated from the permeation rates in the transient regime. The results strongly indicated a coupling of acetic acid flux with the second step of water permeation which probably results from the permeation of water-acetic acid aggregates.

Phospholipid surface density determines the partitioning and permeability of acetic acid in DMPC:cholesterol bilayers.

Relationships between the permeability coefficient (PHA) and partition coefficient (K m/w) of acetic acid and the surface density of DMPC:cholesterol bilayers have been investigated. Permeability coefficients were measured in large unilamellar vesicles by NMR line broadening. Bilayer surface density, sigma, was varied over a range of 0.5-0.9 by changing cholesterol concentration and temperature. The temperature dependence of PHA for acetic acid exhibits Arrhenius behavior with an average apparent activation energy (Ea) of 22 +/- 3 kcal/mole over a cholesterol mole fraction range of 0.00-0.40. This value is much greater than the enthalpy change for acetic acid partitioning between bulk decane and water (delta H degree = 4.8 +/- 0.8 kcal/mole) and the calculated Ea (= 8.0 kcal/mole) assuming a "bulk phase" permeability model which includes the enthalpy of transfer from water to decane and the temperature dependence of acetic acid's diffusion coefficient in decane. These results suggest that dehydration, previously considered to be a dominant component, is a minor factor in determining Ea. Values of 1n PHA decrease linearly with the normalized phospholipid surface density with a slope of kappa = -12.4 +/- 1.1 (r = 0.90). Correction of PHA for those temperature effects considered to be independent of lipid chain order (i.e., enthalpy of transfer from water to decane and activation energy for diffusion in bulk hydrocarbon) yielded an improved correlation (kappa = -11.7 +/- 0.5 (r = 0.96)). The temperature dependence of Km/w is substantially smaller than that for PHA and dependent on cholesterol composition. Values of 1n K m/w decrease linearly with the surface density with a slope of kappa = -4.6 +/- 0.3 (r = 0.95), which is 2.7-fold smaller than the slope of the plot of 1n PHA vs. sigma. Thus, chain ordering is a major determinant for molecular partitioning into and transport across lipid bilayers, regardless of whether it is varied by lipid composition or temperature.