Acetic Water Mixture Research Articles

Solubility measurement, thermodynamic modeling, and molecular dynamic simulation of glycylglycine in five binary solvents

Glycylglycine (Gly–Gly) is a crucial biochemical reagent widely used in cosmetics, food additives, and medicine. Using the equilibrium method, the solubility data of Gly–Gly in four binary solvents (ethanol/isopropanol/ethanediol/acetone + water) were investigated at temperatures over a range of 288.15–328.15 K under 101.3 kPa, as well as in the binary solvent of acetic acid + water from 293.15 to 333.15 K. The solubility data were correlated by Apelblat-Jouyban Acree, Van’t Hoff-Jouyban Acree, and CNIBS/Redlich-Kister models. Additionally, the radial distribution function was obtained through molecular dynamic simulation. It presented the unusual dissolution behavior of Gly–Gly in acetic acid and water mixture. The apparent thermodynamic properties, including standard enthalpy, Gibbs free energy, and entropy change of dissolution, were obtained accordingly. This article could help the industrial crystallization of Gly–Gly.

Mutual Diffusion Coefficients of Ethyl Acetate–Water Mixtures at T = (298.15–368.15 K) Measured by the Taylor Dispersion Method

Mutual Diffusion Coefficients of Ethyl Acetate–Water Mixtures at <i>T</i> = (298.15–368.15 K) Measured by the Taylor Dispersion Method

Supercritical CO2 assisted strategy for acetic acid elimination from industrial cellulose acetate–water mixtures

A critical analysis of the major steps involved in the cellulose acetate industrial process is performed, with the aim of proposing possible improvements using supercritical CO2 based sub-processes. Once highlighted the main weakness of the traditional process, related to the (i) fine modulation of the acetylation reaction to obtain 2.5 acetate, (ii) acetic acid removal from the acetic dope, and (iii) treatment of the diluted acetic acid–water solution, the most attractive alternative resulted the adoption of a supercritical antisolvent extraction (SAE) performed on the acetic dope. Operating in this way, the problems related to the use of large quantities of water to remove acetic acid from the acetic dope are resolved, since it will be directly extracted by supercritical CO2. Micro- and nanoparticles, or filaments, of cellulose acetate can be produced. Finally, an acetic acid residue of 23 ppm, in the supercritical CO2 treated cellulose acetate, confirmed the success of this alternative process configuration.

Selective Oxidation of Crude Glycerol to Dihydroxyacetone in a Biphasic Photoreactor

In this paper, the first biphasic photoreactor was introduced and utilized for the conversion of glycerol to glyceraldehyde (GAD) and dihydroxyacetone (DHA) using water and ethyl acetate as dispersed (active) and continuous (inactive) phases, respectively. Increasing the ethyl acetate content in the reactor improved the DHA yield; however, the optimal DHA selectivity was obtained at an ethyl acetate to water ratio of 90:10 (vol/vol). Compared to a monophasic photoreactor containing only water and identical amounts of glycerol and photocatalyst, the biphasic reactor containing 90 vol % ethyl acetate increased the DHA yield by a factor of 2.9 (from 4.5% to 13%) and the concentration of DHA by approximately 14 times (from 0.08 mM to 1.1 mM) after 240 min. Additionally, photocatalytic conversion of crude glycerol extracted using a 90:10 (vol/vol) ethyl acetate-water mixture showed a similar DHA conversion and yield to that of pure glycerol.

Effect of Pluronic F127 on porous and dense membrane structure formation via non-solvent induced and evaporation induced phase separation

Novel porous and dense membranes based on polysulfone (PSF) modified by poly(ethylene glycol)–b–poly(propylene glycol)–b– poly(ethylene glycol) (Pluronic F127) were developed. The influence of Pluronic F127 introduction to the casting solution on different types of polymer membrane formation via two different phase inversion techniques—non-solvent induced phase separation (NIPS) for porous membranes and evaporation induced phase separation (EIPS) for dense membranes—was investigated. According to the triangular phase diagram obtained, PSF-Pluronic F127-N,N-dimethylacetamide (DMAc) systems feature lower critical solution temperature and have a tendency to micelle formation due to Pluronic F127 self-assembly. The structure, hydrophilic-hydrophobic balance and physicochemical properties of PSF-Pluronic F127 membranes were characterized by water contact angle measurements, scanning electron microscopy, nuclear magnetic resonance, small-angle X-ray scattering, and atomic force microscopy. The performance of dense membranes in pervaporation separation of water-ethyl acetate mixtures was investigated to reveal the effect of Pluronic F127 on the structure and free volume of the PSF-Pluronic F127 membranes. It was shown that Pluronic F127 introduction to the casting solution during membrane formation via two different techniques (NIPS and EIPS) leads to the increase in the pore size of the porous membranes and free volume of the dense membranes, as well as the increase in flux and surface hydrophilicity for both membrane types. Pluronic F127 was found to improve the antifouling performance of porous PSF-Pluronic F127 membranes in the BSA solution ultrafiltration. The introduction of 3 wt% Pluronic F127 into dense PSF membrane improved permeation flux in 1.7 and 2.7 times (15.1 and 27.3 g/(m2h)) at high selectivity level (100 wt% water in the permeate) during the separation of ethyl acetate-water mixtures (2 and 4 wt% ethyl acetate) compared to pristine PSF membrane.

An Eco-friendly Degumming of Apocynum Venetum with Ionic Liquid Pretreatment

ABSTRACT A novel pretreatment process for degumming of apocynum venetum is developed firstly using 1-butyl-3-methylimidazolium acetate-water mixtures. The effect of the four independent parameters on the residue of gum of apocynum venetum fibers was investigated. The results showed that the effect of 1-butyl-3-methylimidazolium acetate concentration on the residue of gum is the most significant, followed by time, temperature, and liquor ratio. The optimal solution of ionic liquid pretreatment for the degumming of apocynum venetum fiber is obtained with a concentration of ionic liquid 80%, liquor ratio 1:20, temperature 90°C, and time 4 h. The residual gum contents for the chemical degummed apocynum venetum fibers were 3.90% with ionic liquid pretreatment. Moreover, the physicochemical properties of the degummed apocynum venetum fibers were also characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Scanning electron spectroscopy (SEM).

PH-Triggered Membrane in Pervaporation Process.

Dehydration of binary methyl acetate–water mixtures under neutral, acidic, and basic conditions was carried out by using PERVAP composite membranes based on polyvinyl alcohol and poly(1-vinylpyrrolidone-co-2-(dimethylamino)ethyl methacrylate) P(VP-co-DMAEMA). The effects of an acid (HCl) and a base (NaOH) on the separation performance of the membrane during the pervaporation process were investigated. The pH-responsive nature of membranes has been confirmed by swelling tests and analysis of the chemical structure of polymeric membranes. In addition, a mechanism of ring-opening of VP units is proposed and correlated to the changes of membrane separation performance.

Experimental investigations on phase separation for different heights of sodium acetate water mixtures under different conditions

Phase separation is a key problem when using sodium acetate trihydrate (SAT) as phase change heat storage material. The formation of phase separation is highly correlated to the composition of SAT based heat storage material, the material height, operation method and environmental condition. This study focus on the phase separation investigation by means of measuring exact water proportions in different layers of SAT samples as well as phase separation mitigation agents. The SAT samples were made with or without different amount of excess water or thickening agents at different heights. Then the samples were tested in supercooled state under different environmental conditions such as short or long term supercooling periods, standing still or shaking from time to time during supercooling, repeated heating and activating and low ambient temperature. The solidification of supercooled samples was activated from top or bottom in order to verify the influence of activation methods. The water proportions in different layers of SAT samples were measured and summarized for comparison. It can be concluded from the experiments that suitable amount of excess water or thickening agents and proper shaking are beneficial to reduce or avoid phase separation. On the other hand, SAT without any additives, repeated heating and activating and low ambient temperature are favourable to forming phase separation for supercooled SAT materials.

Development and Modification of Cellulose Acetate/Carboxy Methyl Cellulose Blend Films for Enhanced Adsorption of Methylene Blue

Herein, we report polysaccharide blend film such as cellulose acetate/carboxymethyl cellulose (CA/CMC) developed using acetic acid and water mixture using solvent casting method. The material prepared here subsequently treated using potassium hydroxide solution in order to remove acetate content from CA/CMC film to make them more active adsorbent. FTIR analysis is carried out to understand the chemical moieties present in CA/CMC films and to confirm the disappearance of acetate group from the blend films. Morphological analysis revealed the surface changing due to the addition of CMC on CA and the deacetylation of CA/CMC. Dye wastewater treatment has been carried out using synthetic methylene blue water solution and found that deacetylated film with higher amount of CMC has more adsorption capacity compared to all other films displayed in this study.

Fabrication of cellulose acetate/chitosan blend films as efficient adsorbent for anionic water pollutants

The aim of this study was to develop a material based on cellulose acetate and chitosan fabricated via a simple non-hazardous solvent casting method and modified them by deacetylation approach. Both the modified and unmodified chitosan/cellulose acetate films were well characterized in terms of their morphology, chemical moieties and wettability using field emission scanning electron microscope, attenuated total reflectance–Fourier transform infrared spectroscope and static water contact angle, respectively. A quantitative analysis such as charge titration experiments was conducted on the films to determine the number of accessible charges in the films which has a significant role in the adsorption phenomenon. Subsequently, the films developed by different compositions of cellulose acetate and chitosan were modified for the first time using deacetylation process under the optimized condition and characterized them using the same above-mentioned technologies. The impact of both unmodified and modified cellulose acetate/chitosan film on freshwater remediation was investigated by adsorbing two known dye such as acid orange 7 and brilliant yellow from the aqueous solution. An enhanced removal efficiency (% R) and adsorption capacity [qe (mg/g)] were observed on both the dyes (99.8% and 9.98 mg/g for acid orange 7, 99.7% and 9.38 mg/g for brilliant yellow) using modified cellulose acetate/chitosan films. The result obtained from this research proved that the modified cellulose acetate/chitosan film was made by acetic acid and water mixture can be used as a potential candidate for anionic dye water treatment.

Energy saving in acetic acid process using an azeotropic distillation column with a side stripper

ABSTRACTDilute acetic acid is obtained primarily from fermentation and synthesis processes and cannot be produced by simple distillation due to relatively low volatility of acetic acid compared to water. Instead, an azeotropic distillation is applied to increase the concentration of dilute acetic acid. When acetic acid is extracted from a dilute aqueous solution using a solvent mixture of ester and alcohol, its recovery requires an energy-intensive azeotropic distillation. In the water stripping process that follows azeotropic distillation, two distillation columns handle the acetic acid and water mixture in similar composition. Therefore, the two columns can be combined as a side stripper connected to the azeotropic distillation column. The energy-saving effect is examined with the HYSYS (Aspentech Corporation) evaluation of the process. Compared to the conventional process, the modified process suggests 39% reduction in heating duty and 24% coolant savings. The economic analysis shows 32% decrease in investment and 36% utility savings. Based on heat utilization analysis, the thermodynamic efficiency is enhanced by 11%.

Electrodeposition of Zinc from 1-ethyl-3-methylimidazolium acetate-water Mixtures: Investigations on the Applicability of the Electrolyte for Zn-Air Batteries

In this paper, the influence of various concentrations of water on the electrochemical and spectroscopic behavior of 1-ethyl-3-methylimidazolium acetate ([EMIm]OAc) and of 1 M Zn(OAc)2/[EMIm]OAc has been investigated. The results show that the added water can reduce the viscosity and improve the conductivity of the employed electrolyte. Spectroscopy results reveal that both [EMIm]OAc and 1 M Zn(OAc)2/[EMIm]OAc interact with water and the extent of interaction varies with the amount of water. Furthermore, the electrochemical behavior of 1 M Zn(OAc)2/[EMIm]OAc is changed with the addition of different concentrations of water. A minimum of 20 vol% water was necessary to electrodeposit Zn from 1 M Zn(OAc)2/[EMIm]OAc at room temperature. Moreover, 1 M Zn(OAc)2/[EMIm]OAc with 20 vol% water was assessed for its possible application as an electrolyte in a Zn-air battery.

Impact of fullerene loading on the structure and transport properties of polysulfone mixed-matrix membranes

Novel mixed-matrix membranes based on polysulfone (PS) and fullerene C60 (up to 5 wt%) have been developed. Two membrane types formed from PS and PS-C60, a dense (diffusive) membrane and a supported membrane, consisted of a thin PS or PS-C60 selective layer (≈5 μm) on the surface of hydrophobic fluorocarbon polymer porous support (MFFC) were studied. The effect of fullerene incorporation on the structure and physical and chemical properties of PS membranes were investigated by scanning electron microscopy, nuclear magnetic resonance, contact angle measurements, sorption experiments, and wide-angle X-ray diffraction. The transport properties of the mixed matrix membranes containing up to 0.5 wt% fullerene were studied for the pervaporation of ethyl acetate–water mixture. The new mixed-matrix membranes, developed in this study, were selective to water, whereas the PS-0.5 % C60/MFFC composite membrane was found to have the best performance.

Thermodynamic screening of lignin dissolution in 1-butyl-3-methylimidazolium acetate–water mixtures

Lignin dissolution in [C4mim]OAc–water mixtures is an exothermal process. Adding water facilitates the mixtures to reach thermodynamic stable state.

Dehydration Pervaporation of Ethyl Acetate-Water Mixture via Sago/PVA Composite Membranes Using Surface Methodology

In the present study hydrophilic sago/polyvinyl alcohol (PVA) blend membranes were used for pervaporation of ethyl acetate-water mixture. The effects of feed concentration, temperature and permeate pressure on the separation factor and permeation flux were studied by using response surface methodology (RSM). The central composite design (CCD) was used to design the experiment and analyze pervaporation performance of homogenous sago/PVA membranes and also to obtain process optimum conditions. It was observed that the permeation flux and selectivity were changed by feed temperature and concentration more than the permeate pressure. The validity of the model was confirmed by the experiments.

SEPARATION OF ETHYL ACETATE FROM WATER MIXTURE USING SAGO/POLY (VINYL ALCOHOL) BLENDED MEMBRANES: EFFECT OF SAGO BLENDED RATIOS

Relatively new Sago/PVA blended membranes were prepared by solution casting technique. Homogenous sago/PVA membranes were prepared with different ratio of sago content in the membrane. The blended membranes were characterized using Fourier Transform Infrared Spectroscopy (FTIR), contact angle measurements, and degree of swelling (DS). The blended membranes were tested for pervaporation of ethyl acetate-water mixture at a range of 1-4wt% of water in the solution. The effects of feed temperature and concentration were investigated. The permeation flux increased around 30% with sago content in the blend membranes from 3wt% to 7wt% at 60oC. However, the separation factor decreased from 433 to 387 for same membrane.

Laboratory Test of a Prototype Heat Storage Module Based on Stable Supercooling of Sodium Acetate Trihydrate

Laboratory test of a long term heat storage module utilizing the principle of stable supercooling of 199.5 kg of sodium acetate water mixture has been carried out. Avoiding phase separation of the incongruently melting salt hydrate by using the extra water principleincreased the heat storage capacity. An external expansion vessel minimized the pressure built up in the module while heating and reduced the risk of instable supercooling. The module was stable supercooled at indoor ambient temperature for up to two months after which it was discharged. The energy discharged after activating the supercooled sodium acetate water mixture was 194 kJ/kg of sodium acetate water mixture in the first test cycles dropping to 179 kJ/kg in the later test cycles. Instability of the supercooling occurred when the charging periods were short and in the last test cycles where the tube connecting the module to the expansion vessel had been blocked by the salt hydrate.

Pervaporation of Ethyl Acetate-Water Mixture through Sago/PVA Blend Membranes Cross-Linked with Glutaraldehyde

Sago composite membrane possesses a microporous polysulfone substrate were prepared and tested for dehydration of ethyl acetate/water mixture. Sago composite membrane has been cross-linked successfully by glutaraldehyde. The membranes were characterized by Degree of swelling (DS) and scanning electron micrographs (SEM). Pervaporation of ethyl acetate –water mixture was conducted over a range of water concentration (1-4wt %) in feed solution at varied temperature from 30°C to 60°C. KeywordsSagostarch:Pervaporation;Ethylacetate;Polyvinylalcohol;CompositeMembrane;

Dissolution enthalpies of cellulose in ionic liquids

In this work, interactions between cellulose and ionic liquids were studied calorimetrically and by optical microscopy. Two novel ionic liquids (1,5-Diazabicyclo[4.3.0]non-5-enium propionate and N-methyl-1,5-diazabicyclo[4.3.0]non-5-enium dimethyl phosphate) and 1-ethyl-3-methylimidazolium acetate–water mixtures were used as solvents. Optical microscopy served in finding the extent of dissolution and identifying the dissolution pattern of the cellulose sample. Calorimetric studies identified a peak relating to dissolution of cellulose in solvent. The transition did, however, not indicate complete dissolution, but rather dissolution inside fibre or fibrils. This method was used to study differences between four cellulose samples with different pretreatment or origins.

Electropolishing of Kovar Alloy for Vacuum Applications

Kovar (53% Fe – 29%Ni - 17% Co) is one of the most commonly used materials in high vacuum applications which quite often require electrical isolation(s). Kovar has thermal expansion coefficient close to that of alumina over the range from brazing to cryogenic temperatures. Therefore, joining problems due to difference in thermal expansion coefficients can be minimized when alumina and Kovar alloy are used together. For the applications that require long vacuum life, Kovar parts should have smooth surfaces to minimize outgas from the surface due to inadequate cleaning. The surface modifications obtained by electropolishing, i.e., preferentially dissolving macroscopic and microscopic surface roughness without grain attack in the depressions, and surface metal oxide layer dissolution [1,2], are indispensable in high vacuum applications. Electropolishing has also long been proven to be a powerful tool for complex parts that are difficult to polish mechanically. Although it is widely used in the vacuum industry, there is very limited information about the Kovar electropolishing in the literature. There is no systematic study known by the authors that aims to reveal the optimum electropolishing conditions for the Kovar alloy.A two-electrode linear sweep voltammetry was conducted in a solution of acetic acid, chromic acid and water mixture, where a copper plate was used as the counter and reference electrode. A plot of current density versus applied potential given in Figure 1 was obtained at 9°C. In the light of almost constant current density, namely limiting current plateau region observed in this plot, some experiments were conducted at 30 V for durations of 30, 60, 90 and 120 seconds. Rectangular Kovar samples of 15x15 mm dimensions having about 0.50 μmRa initial surface roughness were electropolished to final surface roughness of about 0.25 μmRa. The surface roughness profiles and their microstructures before and after electropolishing process (EP) are given in Figures 2 and 3, respectively.Figure Captions:Figure 1: Current density vs. potential graph in acetic acid, chromic acid and water mixture.Figure 2: Surface profiles of samples, (a) before and (b) after EP. The horizontal and the vertical scales are embedded to left hand side.Figure 3: Microstructures of samples, (a) before and (b) after EP.