Aqueous Isopropanol Solution Research Articles

Fabrication of large Pt nanoparticles-decorated rGO counter electrode for highly efficient DSSCs

This study describes the radiolytic fabrication of large Pt nanoparticles (NPs)-decorated reduced graphene oxide (L-Pt/rGO) and its use as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). A homogenous aqueous solution of GO in 10wt% isopropyl alcohol (IPA) aqueous solution containing Pt precursor was irradiated with γ-ray at room temperature to prepare the L-Pt/rGO. The analytic results from TEM, EDX, XPS, and Raman revealed that the rGO decorated with 100nm Pt NPs was successfully formed by the γ-ray irradiation-induced reduction of both the GO and Pt precursor in aqueous IPA solution. Based on the results of the DSSCs performance test, the energy conversion efficiency of the DSSCs with the L-Pt/rGO-based CE outperformed that with the rGO-based one due to the lower sheet resistance, and even was comparable to that of the Pt-based CE. This L-Pt/rGO fabricated by a simple, room temperature and scalable radiolytic method can be used as a promising CE material for low-cost and high-performance DSSCs.

Bioenergy production from sweet sorghum stalks via a biorefinery perspective.

Besides free sugars, sweet sorghum stalks contain cellulose and hemicellulose that can be used for biofuel production. The pretreatment of stalks without the extraction of free sugars is more complicated than typical lignocelluloses, because of the degradation of free sugars during most pretreatment processes. In this study, the bioconversion of sweet sorghum stalks into biogas and bioethanol was studied using an improved organosolv pretreatment within a biorefinery framework. The organosolv pretreatment was developed using an aqueous solution of ethanol (EtOH) and isopropanol (IPOH). The process was optimized to obtain a liquor containing free sugars with the least sugar degradations together with a highly degradable solid fraction. The liquor was subjected to anaerobic digestion for biomethane production, while the solid was used for ethanol production via simultaneous saccharification and fermentation (SSF). The most influencing pretreatment parameters, i.e., temperature, time, alcohol to water ratio, EtOH to IPOH ratio, and the presence or absence of sulfuric acid (as a catalyst), were adjusted to achieve the highest yields of bioconversion. The maximum methane and ethanol production yields of 271.2mL CH4/g VS and 87.8% (equal to the gasoline equivalent of 0.170 and 0.241L/kg, respectively) were achieved from the liquor and pretreated solid, respectively; however, they were obtained at different optimum conditions. Considering the biorefinery perspective, the highest gasoline equivalent of 0.249L/kg was efficiently obtained from the whole process after pretreatment at 140°C for 30min using 60:20 EtOH/IPOH ratio in the presence of 1% sulfuric acid. Further analyses, including enzymatic adsorption/desorption, compositional analysis, FTIR, and SEM, were conducted to investigate the effects of this newly developed pretreatment on the substrate.

Integrated polyamide thin-film nanofibrous composite membrane regulated by functionalized interlayer for efficient water/isopropanol separation

A novel polyamide thin film nanofibrous composite (TFNC) membrane was fabricated by interfacial polymerization (IP) with a modified graphene oxide interlayer on highly porous electrospun polyacrylonitrile (PAN) nanofibrous substrate for isopropanol dehydration by pervaporation. Benefiting from the utilization of ethylenediamine modified graphene oxide (eGO) lamellae, which provided thin and relatively smooth surface but also reaction sites (amine groups) for interfacial polymerization, the resultant TFNC membranes exhibited an integrated structure with a compacter and thinner polyamide (PA) selective skin layer. Significantly, the skillful regulation of interfacial polymerization by the control of deposition amount of eGO on nanofibrous substrate enabled the strong interfacial interaction and the formation of compact selective layer, determining the augment of selectivity of TFNC membranes. The optimized PA/eGO/PAN integrated TFNC membranes exhibited an excellent separation performance for dehydrating 90 wt% aqueous isopropanol solution with remarkably enhanced separation factor (1866) and high permeate flux (4150 g/m2 h) at 70 °C. This result was markedly superior to those of TFC membranes prepared by IP reported so far, suggesting an efficient and facile approach to fabricate high performance pervaporation membrane with unique structures.

Solubility and Modeling of Hesperidin in Cosolvent Mixtures of Ethanol, Isopropanol, Propylene Glycol, and n-Propanol + Water

Equilibrium solubility of hesperidin in aqueous solutions of ethanol, isopropanol, propylene glycol, and n-propanol was determined by static technique at temperatures ranging from 293.15 to 333.15 K under p = 101.1 kPa. The hesperidin solubility increased monotonously with the increase in mass fraction of ethanol isopropanol, propylene glycol, and n-propanol and temperature. At the same composition of alcohol and temperature, the mole fraction solubility of hesperidin was largest in propylene glycol + water among the four cosolvent mixtures. The solubilities of hesperidin were correlated with Jouyban–Acree model, Apelblat–Jouyban–Acree model, and van’t Hoff–Jouyban–Acree model. The obtained average relative deviations were less than 2.38%.

Preparation of polyamide/polyacrylonitrile composite hollow fiber membrane by synchronous procedure of spinning and interfacial polymerization

In this investigation, a new concept for fabrication polyamide (PA)/polyacrylonitrile (PAN) composite hollow fiber membrane by using a triple orifice spinneret was explored. Tetraethylenepentamine (TEPA) and trimesoyl chloride (TMC) were used as the monomers of aqueous solution and acid chloride solution, respectively. The PAN dope, TEPA solution and TMC solution were pumped into the outermost, middle and inner channel of the triple orifice spinneret, respectively, and then co-extruded into water from the outlet of the spinneret simultaneously. The PA layer then was formed on the lumen surface of the synchronous wet-spun PAN hollow fiber membrane. SiO2 was added into the dope to increase the hydrophilicity of the dope. The resultant PA/PAN composite hollow fibers were characterized by using FTIR-ATR, SEM, light transmission, contact angle and positron annihilation spectroscopy (PAS). The effects of SiO2 content, TEPA concentration, as well as the TEPA solution flow rate on the properties and pervaporation performances of resultant PA/PAN composite hollow fibers were investigated. The PA layer was completely attached to the lumen surface of the resulted hollow fibers through the spinning and interfacial polymerization synchronous procedure. The pervaporation performances with 419 g/m2h of permeation flux and 96.6 wt% of water content in permeate of the 90 wt% aqueous isopropanol solution at 25 °C can be obtained through the synchronous fabricated PA/PAN composite hollow fiber membrane which was fabricated by the 18 wt% PAN dope containing 5 wt% SiO2, 1 ml/min of 14 wt% TEPA solution and 2 ml/min of 1 wt% TMC solution.

Rate-based simulation of a high pressure counter-current packed column for supercritical CO2 extraction of alcohol from dilute aqueous mixtures

In this work, the modeling and simulation of a fractionation packed column for the recovery of isopropanol from dilute aqueous mixtures using supercritical CO2 is presented. The model is based on the numerical resolution of differential mass balances for each component over the column height. The multicomponent mass transfer between phases is described using a “rate-based” approach and the concept of local mass transfer coefficients. The model was validated by reproduction of experimental steady-state results for the fractionation of 5% isopropanol aqueous solutions obtained in a bench scale counter-current column. The effect of process conditions on the separation performance was satisfactorily described by the model calculations, showing that operation pressure and CO2 flow rate enhance IPA recovery and extract purity, while operation temperature has a negative effect. Model deviations (AARD) were in all cases lower than 20%.

Options for refractive index and viscosity matching to study variable density flows

Variable density flows are often studied by mixing two miscible aqueous solutions of different densities. To perform optical diagnostics in such environments, the refractive index of the fluids must be matched, which can be achieved by carefully choosing the two solutes and the concentration of the solutions. To separate the effects of buoyancy forces and viscosity variations, it is desirable to match the viscosity of the two solutions in addition to their refractive index. In this manuscript, several pairs of index matched fluids are compared in terms of viscosity matching, monetary cost, and practical use. Two fluid pairs are studied in detail, with two aqueous solutions (binary solutions of water and a salt or alcohol) mixed into a ternary solution. In each case: an aqueous solution of isopropanol mixed with an aqueous solution of sodium chloride (NaCl) and an aqueous solution of glycerol mixed with an aqueous solution of sodium sulfate ( $$\hbox {Na}_2\hbox {SO}_4$$ ). The first fluid pair allows reaching high-density differences at low cost, but brings a large difference in dynamic viscosity. The second allows matching dynamic viscosity and refractive index simultaneously, at reasonable cost. For each of these four solutes, the density, kinematic viscosity, and refractive index are measured versus concentration and temperature, as well as wavelength for the refractive index. To investigate non-linear effects when two index-matched, binary solutions are mixed, the ternary solutions formed are also analyzed. Results show that density and refractive index follow a linear variation with concentration. However, the viscosity of the isopropanol and NaCl pair deviates from the linear law and has to be considered. Empirical correlations and their coefficients are given to create index-matched fluids at a chosen temperature and wavelength. Finally, the effectiveness of the refractive index matching is illustrated with particle image velocimetry measurements performed for a buoyant jet in a linearly stratified environment. The creation of the index-matched solutions and linear stratification in a large-scale experimental facility are detailed, as well as the practical challenges to obtain precise refractive index matching.

Effect of protonation on the photocatalytic activity of the K2La2Ti3O10 layered oxide in the reaction of hydrogen production

The K2La2Ti3O10 layered oxide was synthesized by high-temperature technique. Ion exchange properties of K2La2Ti3O10·H2O were investigated by continuous potentiometric titration of its suspension in KOH with HCl. The shape of the titration curve indicates that the ion-exchange reaction of interlayer K+ to H+ proceeds at pH 7.5–8.5 at the rate as high as 5% min−1. Samples obtained during the titration experiment at pH 9.8, 4.8, and 1.4 were examined by XRD, TG, ICP-AES, and SEM–EDX. Protonation already occurs at pH > 9.8, while at pH 4.8 a substitution degree of 76% is observed. K2La2Ti3O10 was found to be unstable against K+ leaching, which results in irreversible ion-exchange even when the sample is washed with distilled water. The protonation of the layered oxide significantly suppresses its photocatalytic activity in the reaction of hydrogen production from aqueous isopropanol solution, which correlates with the decreasing amount of intercalated water.

Study on the components of isopropanol aqueous solution

Isopropanol is thought to play a significant part in industrial production. In this work, we study the components of the isopropanol aqueous solution based on Time-Correlated Single Photon Counting (TCSPC) and Density Functional Theory (DFT). The experimental results show that the components in the isopropanol aqueous solution are related to the concentration of the solution. New structures are formed more easily when the concentration of isopropanol is small. In addition to concentration, these solutions are also affected by the excitation wavelength. The fluorescence lifetimes, relative concentrations, and the relative emission intensity of different emitting components in the solution at various concentrations are obtained. The theoretical calculations are performed on the structures of (CH3)2CHOH(H2O)n (n=1∼6) clusters. By comparing the structural parameters, we find that (CH3)2CHOH(H2O)4 is more stable. The results suggest that (CH3)2CHOH(H2O)4 clusters are more probable in the isopropanol aqueous solution. This work may shed light on the further theoretical and experimental study on the isopropanol aqueous solution.

Ultrasonic-assisted fabrication of high flux T-type zeolite membranes on alumina hollow fibers

Ultrasonic-assisted pretreatment prior to hydrothermal synthesis is employed for the first time in the preparation of T-type zeolite membranes on α-Al2O3 hollow fibers by secondary growth. The synthesis time can be shortened from 40h to 24h with only 0.5h ultrasonic pretreatment of the synthesis solution. Elongating ultrasonic treatment time to 1.0h has no further improvement for the formation of dense membrane. Typically, the pure phase T-type zeolite membrane synthesized in 24h with 0.5h ultrasonic pretreatment has a separation factor of > 10,000 and a flux of 12.2kgm−2h−1 for 90.0wt% isopropanol aqueous solution at 75°C. When the porosity of the hollow fiber support is 68%, the flux is as high as 14.3kgm−2h−1, which is the highest flux ever reported. The high flux of the membrane can be mainly ascribed to the special structure and porosity of the α-Al2O3 hollow fiber support. Finally, a mechanism for ultrasonic-assisted membrane preparation is proposed.

Interactions of superhydrophobic carbon soot coatings with short alkyl chain alcohols and fluorocarbon solutions

Carbon soot is a nanomaterial, whose extreme water repellency determines its potential industrial applicability in anti-fouling coatings, anti-icing systems, chemical sensors and drag reducing surfaces. The wettability and mechanical durability of the soot can be adjusted through an appropriate chemical treatment, but the underlying mechanism is yet unknown. In this paper, we provide new insights regarding the missing link between the fundamentals of soot-alcohol-fluorocarbon interactions and the derivative physicochemical features/properties of the coating. This is achieved by immersion of three types of superhydrophobic soot coatings in aqueous solutions of methanol, ethanol and isopropanol with variable concentration, and subsequent functionalization with fluorocarbon emulsion. The detailed structural and chemical analysis using scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, reveals that the thickness, porosity and ratio of chemical bonds in the soot alter proportionally to the quantity of oxygen functional groups and point defects in the coating, as well as the alkyl chain length of alcohols. Moreover, the chemical treatment with fluorocarbon causes the formation of a thin fluoropolymer film on top of the soot that reinstates its superhydrophobicity and imparts oleophobicity of the surface. These findings are fundamental for further synthesis of soot coatings with controllable surface properties.

Crosslinked polybenzoxazine based membrane exhibiting in-situ self-promoted separation performance for pervaporation dehydration on isopropanol aqueous solutions

The performance of pervaporation dehydration of a crosslinked polybenzoxazine membrane (CR-PBz-M) on isopropanol (IPA) aqueous solutions has been studied. Compared to the feature showing in dry state, CR-PBz-M exhibits a change in micropore size distribution from a single distribution to a bimodal pattern in wet state being swollen with the feeding solutions. The presence of two groups of micropores in different sizes attributes to the high pervaporation dehydration performance of the membrane, in which the small micropores resist to the permeation of IPA molecules so as to contribute to the high membrane selectivity and the large micropores and high micropore volume fraction contribute to the high permeation fluxes. This feature of CR-PBz-M demonstrates an in situ self-promoted characteristic for pervaporation dehydration membranes. A permeation flux of 330gh−1m−2 and a 100% of water in the permeate side has been recorded on pervaporation dehydration on a 70wt% IPA aqueous solution.

Examination of a New Desorption Method for Solid Adsorption Method of Working Environment Measurement －Attempt to Improve Desorption Efficiency of Organic Solvents from a Coconut-Shell-Activated Carbon Using Surfactant Solutions－.

For a new desorption method development for working environment measurement, desorption efficiency of organic solvent vapors from an activated carbon was examined using desorption solutions that consisted of anionic and nonionic surfactants. Ten μl of an aqueous solution of isopropyl alcohol or methyl ethyl ketone diluted with distilled water was spiked into a 10 ml vial with a coconut-shell-activated carbon (100 mg). The vial was left for 24 h, and 5 ml a desorption solution was added. Afterwards, the vial was put into an incubator at 60°C and left for 24 h, then the desorption efficiency was determined by analyzing the headspace gas in the vial with a gas chromatograph equipped with flame ionization detector. By adding one or four kinds of nonionic surfactants to the aqueous solution containing two kinds of anionic surfactants, the effect adding nonionic surfactant to the desorption efficiency was investigated, but improvement of desorption efficiency was not observed. On the other hand, desorption efficiency varied depending on the production lot of the coconut-shell-activated carbon tube used as the adsorbent.

Self-healing polymeric materials for membrane separation: an example of a polybenzimidazole-based membrane for pervaporation dehydration on isopropanol aqueous solution

The demonstration of a self-healing material based separation membrane for pervaporation dehydration on liquid–liquid mixtures.

A green and efficient photo-driven route for the selective oxidation of aqueous isopropanol solution to pinacol (C6) with hydrogen peroxide

The proposed strategy provides a green solution for the synthesis of aliphatic pinacol and offers a new design for the construction of C–C bonds with alphatic alcohol.

Optical microinterferometry method for evaluation of phase state and diffusion in ternary systems: phase separation in cellulose/N-Methylmorpholine-N-oxide/non-solvent mixtures

Microinterferometry technique was used to evaluate the phase state and diffusion of cellulose solutions N-Methylmorpholine-N-oxide upon contact with non-solvents (water and aqueous solutions of isopropyl alcohol). The method was helpful in visualization of the structure of the forming cellulose film in connection with the diffusivity of the components of the systems. The interdiffusion coefficient were determined. Isopropyl alcohol addition to water slows down the diffusion of the coagulant into the cellulose solution thus delaying cellulose precipitation. Increase of temperature leads to formation of less dense cellulose film morphology with large vacuoles.

(Invited) Solar Synthesis of C1-C4 Chemicals from Carbon Dioxide and Water

There is renewed interest in the photoelectrochemical conversion of CO2 into value-added chemicals using various semiconductor particles and electrodes. Common CO2 reduction products are C1 chemicals (CO, HCOOH, CH3OH, and CH4) in aqueous media, while the production of C2-C4 hydrocarbons (e.g., C2H6 and C3H8) has also been reported. A number of solar-active materials have been reported, but they still suffer from low selectivity, poor energy efficiency, and instability, while failing to drive simultaneous water oxidation. This talk presents our recent studies on the solar CO2 conversion to value-added chemicals while using water as an electron donor in various photo-systems [1-5]. [1] S.K. Choi, U. Kang, S. Lee, D.J. Ham, S.M. Ji, and H. Park, Sn-coupled p-Si nanowire arrays for solar formate production from CO2, Advanced Energy Materials 4 (2014) 1301614. [2] H. Park, H.-H. Ou, A.J. Colussi, and M.R. Hoffmann, Artificial photosynthesis of C1 to C3 hydrocarbons from water and CO2 on titanate nanotubes decorated with nanoparticle elemental copper and CdS quantum dots, Journal of Physical Chemistry A 119 (2015) 4658. [3] U. Kang, S.K. Choi, D.J. Ham, S.M. Ji, W. Choi, D.S. Han, A. Abdel-Wahab, and H. Park, Photosynthesis of formate from CO2 and water at 1% energy efficiency via copper iron oxide catalysis, Energy & Environmental Science 8 (2015) 2638. [4] H. Park, H.-H. Ou, U. Kang, J. Choi, and M.R. Hoffmann, Photocatalytic conversion of carbon dioxide to methane on TiO2/CdS in aqueous isopropanol solution, Catalysis Today 266 (2016) 153 [5] N.C.D. Nath, S.Y. Choi, H.W. Jeong, J.-J. Lee, and H. Park, Nano Energy, revised.

Hydrothermal express synthesis of CNT/MnO2 composite for asymmetric supercapacitor

A hydrothermal technique for the express synthesis of a composite based on carbon nanotubes (CNTs) and manganese dioxide by means of the direct reduction of potassium permanganate from an aqueous isopropanol solution is proposed in this work. The synthesis conditions (time, temperature, ratios between reagents) are optimized; the primary and secondary processes taking place in the system are considered in detail. The synthesized CNT/MnO2 composite is studied with the help of a wide range of physicochemical and electrochemical methods to assess the possibility of its use as a positively charged electrode of an asymmetric supercapacitor (SC). The assembled SC cell based on this composite and an activated carbon (AC) electrode has fairly high power typical of conventional electric double-layer capacitors (0.82 kW/kg) with a twofold increase in the energy density (12.14 W h/kg).

Novel pH-Sensitive Poly(Vinyl Alcohol) Based Polyampholyte as Pervaporation Membrane

Sodium acrylate (NaAA) and acrylamide (AM) were grafted onto poly (vinyl alcohol) (PVA) using potassium persulfate as an initiator, Graft copolymerization namely poly (vinyl alcohol)-g-poly (acrylamide/sodium acrylate) (PVA-g-PAM/SAC). The poly (vinyl alcohol)-g-poly (vinylamine/sodium acrylate) (PVAMC) was prepraed by Hofmann rearrangement.The PVAMC homogeneous membrane was characterized by fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM).The water resistance of the PVAMC membranes is the best when pH of the PVAMC solutions was 4, at that time the numbers of-NH3+ and-COO- groups trended to be equal, so the isoelectric point was pH=4. At 90 °C the pervaporation of PVAMC composite membrane was tested and showed that the separation factor and the permeate flux were about 1001 and 1341 g/(m2·h) for 90wt% ethanol aqueous solution, and they were about 1297 and 1040 g/(m2·h) for 90wt% isopropanol aqueous solution.

Microwave synthesis of zeolite CHA (chabazite) membranes with high pervaporation performance in absence of organic structure directing agents

Thin and compact zeolite chabazite membranes were prepared by microwave heating using symmetric stainless steel tubular supports. The microstructures (crystal size and membrane thickness) and separation performances of supported chabazite layers were strongly affected by heating method, synthesis time and synthesis temperature. The best membrane prepared by microwave heating under optimized conditions showed fluxes of 7.3 and 9.1 kg/(m2 h) and separation factors of 2000 and 2500 for 90 wt.% ethanol and isopropanol aqueous solutions at 348 K, respectively. These fluxes were twice as high as those of the chabazite membranes prepared by conventional heating due to the thinner zeolite layers and lower resistance of the support layer in the microwave heating system. The membrane prepared on the 3-time-reused stainless steel support showed comparable separation performance with the membrane on the fresh support, suggesting that the stainless steel supports had a good reuse prospect for chabazite membrane preparation. Synthesis reproducibility and hydrothermal stability of chabazite membranes by microwave heating were also investigated.