Aqueous Glycerol Solutions Research Articles

Enhance photocatalytic of hydrogen production from water-glycerol solution over RuO2-loaded

Study of hydrogen production from aqueous glycerol solution on RuO2-loaded LaNaTaO3 has been studied. This research aim is to investigate the influence of co-catalyst RuO2 and glycerol as a sacrificial reagent on the photocatalytic process of hydrogen production. La-doped NaTaO3 was prepared via sol-gel route. The RuO2 was loaded onto the LaNaTaO3 surface by impregnation method. The sample was characterization by Scanning Electron microscopy (SEM) and X-ray Diffractometer (XRD). From XRD spectrum shows that the La-NaTaO3 photocatalyst has high crystallinity. The SEM analysis indicates that the size of La-NaTaO3 photocatalyst is ranging from 100 to 250 nm without agglomeration and RuO2 as a co-catalyst is well loaded into the La-NaTaO3 surface. The rate of hydrogen production increased significantly with a glycerol concentration. Loading RuO2 on La-NaTaO3 photocatalyst is proved to increase the rate of hydrogen production of 3.2 times with the addition of glycerol as a sacrificial reagent. The highest hydrogen production activity was obtained for 0.3 wt.% ruthenium loading. The role of co-catalyst RuO2 and glycerol as a sacrificial reagent has enhanced the performance of La-NaTaO3 photocatalyst since both play an active role in the separation efficiency of electrons and holes and the reaction of hydrogen formation.

Hydrogel-based temperature sensor with water retention, frost resistance and remoldability

Conventional hydrogels will be frozen at low temperatures and lose their flexibility. At higher temperatures, hydrogels will lose water more quickly. The inherent property of hydrogels hinders its development in the field of flexible wearable sensors. In this research, we studied the anti-freezing and moisturizing mechanism of glycerol (Gly), ethylene glycol (EG) and CaCl2 aqueous solutions. The Gly solution with excellent antifreeze humectant and friendly to the organism was selected as antifreeze humectant. We introduced Gly into PVA gel to make the gel have anti-freezing and moisturizing properties, and then introduced silver nanofibers (AgNW) into the gel to obtain the temperature sensor with anti-freezing and moisturizing properties. Since the gel uses reversible physical cross-linking, the sensor has excellent remodeling ability. The temperature sensor has the advantages of high sensitivity, short response time to temperature and excellent accuracy. It is expected to be applied to temperature sensors under severe weather conditions.

Preferential Interaction of Chymotrypsinogen in Aqueous Solutions of Polyols at 298.15 K

Preferential interactions of α-chymotrypsinogen in water and aqueous solutions of ethylene glycol, glycerol, erythritol, sorbitol, and inositol were studied from precise density measurements under conditions of constant molality and constant chemical potential; to achieve the last condition, solutions were brought under equilibrium dialysis. The density measurements were performed at 298.15 K and they were used to determine the preferential interaction parameters. The results confirm a significant correlation between the numbers of hydroxyl groups of the polyols with the stability of α-chymotrypsinogen.

Glycerol-Mediated Facile Synthesis of Colored Titania Nanoparticles for Visible Light Photodegradation of Phenolic Compounds.

In this study, we developed a glycerol-mediated safe and facile method to synthesize colored titania nanoparticles (NPs) via solution route. Our method is considerably effective and greener than other options currently available. Colored titania NPs were produced by hydrolyzing TiCl4 precursor in aqueous solution containing different concentrations of glycerol (0.0, 1.163, 3.834, and 5.815 mol/L) and subsequent calcination at 300 °C for 1 h. Our results highlight firstly that glycerol-mediated synthesis is unlikely to affect the anatase crystalline structure of TiO2, and secondly, that it would lead to coloration, band gap narrowing, and a remarkable bathochromic redshift of the optical response of titania. More importantly, the synthesized colored titania have Ti3+ ions, which, at least in terms of our samples, is the major factor responsible for its coloration. These Ti3+ species could induce mid gap states in the band gap, which significantly improve the visible light absorption capability and photocatalytic performance of the colored titania. The photocatalytic experiments showed that the colored TiO2 NPs prepared in 1.163 mol/L aqueous glycerol solution displayed the best photocatalytic performance. Almost 48.17% of phenolic compounds and 62.18% of color were removed from treated palm oil mill effluent (POME) within 180 min of visible light irradiation.

An experimental study of hydrodynamics and heat transfer at fluid filtration through a porous medium

An experimental study of hydrodynamics and heat transfer under conditions of filtering of water and aqueous solution of glycerol through a porous insert in the channel was carried out. The values of the coefficient of hydraulic resistance and heat transfer for a chaotic backfill of balls with a diameter of 3.2 mm for filtering water and 47% glycerol solution have been determined. Three flow regimes were investigated: inertial, transient and turbulent. It has been found that, depending on the filtering mode through the porous insert, there are various laws of heat transfer. Comparison of the obtained results on heat transfer in ball fillings with the available literature data has been carried out. The obtained experimental data are in good agreement with the data of numerical calculations. For the thermal stabilization section at high values of the Reynolds number they are in good agreement with the data obtained by filtering air through a porous medium.

Internal flow during mixing induced in acoustically levitated droplets by mode oscillations

In this paper, we describe a mixing method with mode oscillation on the internal flow field of a levitated droplet. The effect of internal flow on the mixing performance of droplets acoustically levitated via ultrasonic phased arrays remains unclear. To better understand the mixing mechanism of a levitated droplet, clarifying the effect of the internal flow field on droplet mixing from mode oscillation during acoustic levitation is necessary. We used a 50 wt. % glycerol aqueous solution with 6th mode oscillation. We applied particle image velocimetry (PIV) to study the internal flow fields under interfacial oscillation. The PIV results indicated that the visualized flow field enhanced mixing performance with increasing Reynolds number. We demonstrated the nonlinear characteristics of droplet mixing compared to potential flow. The nonlinearity of the droplet oscillation was driven by the nonlinear acoustic field exerted on the levitated droplet. Mode oscillation on the droplet surface induced a pressure gradient and caused internal flow in the droplet. The pressure gradient in the droplet from the interfacial oscillation was quantitatively analyzed. Pressure induced by the interfacial oscillation, which can be roughly ten times larger than the hydrostatic pressure in the droplet, drastically enhanced the mixing performance in the droplet. Our experimental findings provide deeper physical insights into noncontact fluid manipulation for potential lab-in-a-drop applications.

BIOCONVERSION OF CRUDE GLYCEROL INTO REUTERIN BY LACTOBACILLI ISOLATED FROM SILAGE

Heterofermentative lactobacilli were isolated from sorghum and maize silage, and their ability to produce the antimicrobial compound reuterin (3-hydroxypropionaldehyde, 3-HPA) was investigated. Additionally, reuterin production from crude and partially purified biodiesel-derived glycerol was evaluated as an alternative to the utilization of these by-products. Only two out of 148 lactobacilli isolated produced reuterin in the presence of glycerol. The gene encoding a subunit of glycerol dehydratase was detected by PCR in isolates SO8 and SO23, identified as Lactobacillus reuteri by 16S rRNA gene sequence analysis. Levels of reuterin produced by these two isolates and strain L. reuteri DSM 17938, used as control, were different. For each bacteria, the amount of reuterin detected from biodiesel-derived glycerol was comparable with that obtained from aqueous solution of pure glycerol. Among silage isolates, L. reuteri SO23 yielded the highest levels of reuterin production. In addition, cell-free supernatants revealed inhibitory activity against silage spoilage microorganisms like spore-forming bacteria, yeast and mould. L. reuteri SO23 proved to be a valuable candidate for use of crude glycerol and its bioconversion to reuterin. Addition of glycerol together with reuterin-producing lactobacilli strains could represent a good alternative as silage biopreservant and help optimize profit in biodiesel production.

Spherical Particle Formation Mechanism in Pulsed Laser Melting in Liquid under Controlled-Pulse-Number Irradiation using a Slit Nozzle Flow System

A detailed mechanism of pulsed laser melting in liquid (PLML) has remained a controversial issue because of the difficulty associated with tracking and observing particles irradiated with a specific number of pulses in conventional batch-style irradiation. In a previous study, we developed a flow irradiation technique with a new slit nozzle for PLML mass-production. The slit nozzle can precisely control pulse numbers irradiated onto particles flowing through the slit nozzle. In the present study, this unique feature of the slit nozzle was used to clarify the PLML mechanism by a specific pulse number irradiation. According to a numerical analysis of the flow with the slit nozzle, 79% of the particles flowing through the slit nozzle were irradiated with two or three pulses and other particles that were irradiated with three or more pulses upon one passage through the slit nozzle at a 1.1 mL s–1 volume flow rate for a particle suspension in 60 wt % glycerol aqueous solution. Sub-micrometer-sized hollow spher...

Pt/ZrO2 Prepared by Atomic Trapping: An Efficient Catalyst for the Conversion of Glycerol to Lactic Acid with Concomitant Transfer Hydrogenation of Cyclohexene.

A series of heterogeneous catalysts consisting of highly dispersed Pt nanoparticles supported on nanosized ZrO2 (20 to 60 nm) was synthesized and investigated for the one-pot transfer hydrogenation between glycerol and cyclohexene to produce lactic acid and cyclohexane, without any additional H2. Different preparation methods were screened, by varying the calcination and reduction procedures with the purpose of optimizing the dispersion of Pt species (i.e., as single-atom sites or extra-fine Pt nanoparticles) on the ZrO2 support. The Pt/ZrO2 catalysts were characterized by means of transmission electron microscopy techniques (HAADF-STEM, TEM), elemental analysis (ICP-OES, EDX mapping), N2-physisorption, H2 temperature-programmed-reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Based on this combination of techniques it was possible to correlate the temperature of the calcination and reduction treatments with the nature of the Pt species. The best catalyst consisted of subnanometer Pt clusters (<1 nm) and atomically dispersed Pt (as Pt2+ and Pt4+) on the ZrO2 support, which were converted into extra-fine Pt nanoparticles (average size = 1.4 nm) upon reduction. These nanoparticles acted as catalytic species for the transfer hydrogenation of glycerol with cyclohexene, which gave an unsurpassed 95% yield of lactic acid salt at 96% glycerol conversion (aqueous glycerol solution, NaOH as promoter, 160 °C, 4.5 h, at 20 bar N2). This is the highest yield and selectivity of lactic acid (salt) reported in the literature so far. Reusability experiments showed a partial and gradual loss of activity of the Pt/ZrO2 catalyst, which was attributed to the experimentally observed aggregation of Pt nanoparticles.

Do-It-Yourself Pyramidal Mold for Nanotechnology.

The handcrafted fabrication of a pyramidal mold on a silicon wafer for nanopatterning was investigated. This process started with the manual delivery of an aqueous glycerol solution onto the SiO2/Si wafer using a micropipette and subsequent drying to form a hemisphere whose diameter is in the range of hundreds of micrometers. A coating of polystyrene (PS) onto this wafer generates a circular hole caused by dewetting. Subsequently, anisotropic wet-etching with the PS film as a mask produces a pyramidal trench, whose apex approaches hundreds of nanometers. Various elastomeric materials were casted into this pyramidal mold. A pyramidal tip mounted on a simple micropositioner was used for electrochemistry and patterning of a protein. First, an agarose hydrogel was cast with a hydrogel pen for the electrochemical reaction (HYPER). The redox reaction at the HYPER–electrode interface demonstrated the characteristics of an ultramicroelectrode or bulk electrode based on the contact area. Second, the pyramidal polydimethylsiloxane served as a polymer pen for the contact printing of silane on a glass substrate. After the successive immobilization of biotin and avidin with fluorescence labeling, the resulting fluorescence image demonstrated the successful patterning of the protein. This new process for the creation of a pyramidal mold, referred to as a “do-it-yourself” process, offers advantages to nonspecialists in nanotechnology compared to conventional lithography, specifically simplicity, rapidity, and low cost.

Converting glycerol aqueous solution to hydrogen energy and dihydroxyacetone by the BiVO4 photoelectrochemical cell

Replacement of oxygen evolution reaction (OER) by the more readily oxidized biomass derivatives is considered to be a promising strategy for photoelectrocatalytic water splitting hydrogen production. In this work, a biodiesel industrial waste by-product, glycerol, played the critical role for the efficient hydrogen production as well as the highly valuable dihydroxyacetone (DHA) and industrial useful formic acid production. As the glycerol was introduced, a remarkable cathodic shift of the onset potential was observed (∼300 mV) while the current density was 4 times higher compared to the water oxidation. The incident photon-to-current efficiency (IPCE) of BiVO4 photoanode for glycerol oxidation reached about 55%, which was 3 times higher than the system without glycerol. More importantly, during the photoelectrochemical water splitting in glycerol aqueous solution, in addition to the evolved hydrogen gas, glycerol was oxidized to valuable products with 15% dihydroxyacetone (DHA) and 85% formic acid. This strategy not only boosts the hydrogen production efficiency, keeps the photoanode very stable but also makes the biodiesel production more profitable and sustainable.

Surface coverage by impact of droplets from a monodisperse spray

A novel pneumatic monodisperse spray was fabricated to validate the results of a probabilistic model and a stochastic model that were developed to predict surface area coverage of the monodisperse spray. Multiple droplets of a highly viscous 87 wt% aqueous glycerin solution were deposited on a flat, transparent, plexiglass substrate. The uniformly sized droplets (2.5 mm in diameter) impacted, spread, and coalesced on the substrate which led to the creation of a liquid sheet. Using a high-speed camera placed underneath the transparent substrate, droplet impact and resultant area coverage were recorded. When impinging droplets overlapped those already on the surface, surface tension forces pulled impacting droplets towards them, agglomerating the liquid, in a phenomenon known as drawback. The area covered by the liquid was measured from photographs using image analysis software. In the numerical models, droplets were set to impinge at random locations and drawback effects between droplets were accounted for by using a semiempirical correlation. While both models showed good agreement with the experimental results at lower area fractions, the stochastic model gave better estimates at larger area fraction due to its incorporation of drawback effects.

Motion of Newtonian drops deposited on liquid-impregnated surfaces induced by vertical vibrations

We have studied the motion of drops on inclined liquid-impregnated surfaces (LISs) subject to vertical vibrations. The liquid drops comprise distilled water and different aqueous solutions of glycerol of increasing viscosity. The use of weak pinning LISs strongly affects the dynamical phase diagram. First of all, there is no trace of the dominant static region at low oscillating amplitudes reported for oscillating solid surfaces characterized by contact angle hysteresis. On the contrary, at sufficiently low oscillating amplitudes, the drops always move downwards with a velocity that depends only on the drop viscosity. Further increasing the oscillating amplitude may drive the drop upwards against gravity, as reported for dry surfaces. The use of more viscous drops widens this climbing region. Arguably, the main novelty of this work concerns the observation of two distinct descending regimes where the downhill speed differs by a factor of five or more. Fast-rate videos show that the evolution of the drop profile is diverse in the two regimes, likely because the vertical oscillations reduce the effect of the oil meniscus surrounding the drop at high accelerations.

Synthesis and performance evaluation of silica-supported copper chromite catalyst for glycerol dehydration to acetol

Sol-gel technique was used to prepare silica-supported copper chromite catalyst from acid hydrolysis of sodium silicate. The catalyst was characterized by BET surface area, FESEM, XRD, H2-TPR and pyridine adsorption by FTIR. The catalyst was activated in a hydrogen atmosphere based on H2-TPR result. The surface acidity of the catalyst was evaluated by NH3-TPD and pyridine adsorption. XRD result of reduced catalyst showed the presence of Cu0, Cu1+ and Cr2O3 in the catalyst. Glycerol dehydration was carried out at different temperature (180 °C to 240 °C) from aqueous glycerol solution with the reduced catalyst in a batch reactor. The glycerol conversion was reached 100% with maximum acetol selectivity of 70% for highest Copper chromite loaded (40 wt%) on silica at 220 °C in atmospheric pressure. The distilled liquid product was analyzed by high-performance liquid chromatography. Oxidized catalyst and spent catalyst showed lower glycerol conversion with low acetol selectivity than the reduced form of the catalyst. This is due to the cuprous ion in the reduced form of the catalyst, which acts as Lewis acid sites in glycerol dehydration. Glycerol dehydration to acetol with reduced form of silica-supported copper chromite catalyst is reported. The reduced form of copper chromite (cuprous oxide) on silica surface acts as a lewis acid in glycerol dehydration. Cuprous oxide coordinates with terminal hydroxyl group of glycerol and forms low energy six-membered transition state in the dehydration reactions.

Synthesis and pharmacological activity of a silicon—zinc—boron-containing glycerohydrogel

A new pharmacologically active nanostructured silicon—zinc—boron-containing glycerohydrogel was synthesized by the sol—gel method using silicon, zinc, and boron glycerolates as biocompatible precursors. The hydrogel composition and structural features were investigated by transmission electron microscopy, powder X-ray diffraction, IR spectroscopy, atomic emission spectrometry, and elemental analysis; a structural model was proposed. It was found that the 3D framework of the gel is formed by the products of hydrolysis and subsequent (co)condensation of silicon- and boron-containing precursors. Meanwhile, the major part of zinc monoglycerolate does not undergo hydrolytic transformations during gelation, being present in the 3D framework cells as amorphous nano-sized particles. The dispersion medium of the gel is an aqueous glycerol solution of silicon and boron glycerolates, products of their hydrolytic transformations, and water-soluble products of hydrolytic transformations of zinc monoglycerolate. The silicon—zinc—boron gel is nontoxic and possesses wound-healing and antimicrobial activities; it can be considered as a nanostructured dispersed system promising for biomedical applications, which is prepared in a simple and cost-effective way without using catalysts or toxic organic solvents.

Numerical simulation of shock and detonation waves in bubbly liquids

A well-posed mathematical model of nonisothermal, two-phase, two-velocity flow of a bubbly medium with chemically inert liquid and chemically inert or active gas bubbles is proposed. The model is based on the two-phase Euler equations with the introduction of an additional pressure at the gas-bubble surface, which ensures the well-posedness of the Cauchy problem for a system of governing equations, and the Rayleigh–Plesset equation for radial pulsation of gas bubbles allowing solutions of the soliton type that are realized in experiments to be obtained. The model is validated by comparing calculations of detonation wave propagation with experimental data in water or an aqueous solution of glycerin with bubbles of acetylene–oxygen mixture or with bubbles of argon–hydrogen–oxygen mixture for a volume gas content of 1–6%. The model is shown to provide satisfactory results for the detonation propagation velocity and detonation pressure profiles.

Photocatalytic Hydrogen Production from Glycerol Aqueous Solution Using Cu-Doped ZnO under Visible Light Irradiation

Cu-doped ZnO photocatalysts at different Cu loadings were prepared by a precipitation method. The presence of Cu in the ZnO crystal lattice led to significant enhancement in photocatalytic activity for H2 production from an aqueous glycerol solution under visible light irradiation. The best Cu loading was found to be 1.08 mol %, which allowed achieving hydrogen production equal to 2600 μmol/L with an aqueous glycerol solution at 5 wt % initial concentration, the photocatalyst dosage equal to 1.5 g/L, and at the spontaneous pH of the solution (pH = 6). The hydrogen production rate was increased to about 4770 μmol/L by increasing the initial glycerol concentration up to 10 wt %. The obtained results evidenced that the optimized Cu-doped ZnO could be considered a suitable visible-light-active photocatalyst to be used in photocatalytic hydrogen production without the presence of noble metals in sample formulation.

Molecular insights on the microstructures of nanoconfined glycerol and its aqueous solutions: The effects of interfacial properties, temperature, and glycerol concentration

In this work, we conducted molecular dynamics simulations to investigate the effects of rutile–liquid and graphene–liquid interfacial properties, glycerol concentrations (i.e., 10%, 40%, 70%, and 100% molar contents), and temperature (i.e., 180, 273, and 320 K) on the microstructures of nanoconfined glycerol and its aqueous solutions. Results indicated that the effect of interfacial properties on the spatial and orientation distributions of nanoconfined glycerol and water molecules was more prominent than that of temperature. In glycerol aqueous solutions, water and glycerol molecules localized into two distinct layers on the hydrophilic rutile surface but partially mixed with each other near the hydrophobic graphene surface, because water molecules near the hydrophobic surface exhibited more random orientations and formed more hydrogen bonds with glycerol molecules than those near the hydrophilic surface. Moreover, interface introduction and increased temperature drastically reduced the hydrogen bonding ability of water molecules in glycerol aqueous solutions. The addition of glycerol molecules can break hydrogen bonds between water molecules and inhibit water crystallization in glycerol aqueous solutions. Temperature and glycerol concentration exerted limited effects on the hydrogen bonding ability of water molecules on hydrophilic surfaces in glycerol aqueous solutions. Meanwhile, the presence of a hydrophilic surface can effectively decelerate hydrogen bond breakage induced by increasing temperature or by decreasing glycerol contents.

Analysis and experiments on the spreading dynamics of a viscoelastic drop

• Spreading dynamics of a sessile viscoelastic drop on a horizontal surface is studied. • Simplified Phan–Thien–Tanner model represents the rheology of the viscoelastic drop. • Theoretical results are validated with our experimental results. • Elastic nature of the viscoelastic fluids reduces the spreading rate of the drop. We study the spreading dynamics of a sessile viscoelastic drop on a horizontal surface, where a simplified Phan–Thien–Tanner (sPTT) model is considered to represent the rheology of viscoelastic drop. We have adopted a macroscopic approach to obtain the temporal evolution of the spreading drop, while to establish the efficacy of the theoretical model, we have validated the results obtained from the mathematical formulation with the experimental results for both the Newtonian (Si-oil) and viscoelastic (PDMS and aqueous solution of CMC and glycerin) drops. Following the framework of Seaver–Berg approximation, the spherical shape of the drop is assumed as a cylindrical disk here. We observe from this study that an increment in the elasticity of the fluid enhances the velocity gradient and increases the viscous dissipation in the drop volume, leading to a reduction in the spreading rate.

Predictive Framework for the Spreading of Liquid Drops and the Formation of Liquid Marbles on Hydrophobic Particle Bed.

In this work, we have developed a model to describe the behavior of liquid drops upon impaction on hydrophobic particle bed and verified it experimentally. Poly(tetrafluoroethylene) (PTFE) particles were used to coat drops of water, aqueous solutions of glycerol (20, 40, and 60% v/v), and ethanol (5 and 12% v/v). The experiments were conducted for Weber number ( We) ranging from 8 to 130 and Reynolds number ( Re) ranging from 370 to 4460. The bed porosity was varied from 0.8 to 0.6. The experimental values of βmax (ratio of the diameter at the maximum spreading condition to the initial drop diameter) were estimated from the time-lapsed images captured using a high-speed camera. The theoretical βmax was estimated by making energy balances on the liquid drop. The proposed model accounts for the energy losses due to viscous dissipation and crater formation along with a change in kinetic energy and surface energy. A good agreement was obtained between the experimental βmax and the estimated theoretical βmax. The proposed model yielded a least % absolute average relative deviation (% AARD) of 5.5 ± 4.3 compared to other models available in the literature. Further, it was found that the liquid drops impacting on particle bed are completely coated with PTFE particles with βmax values greater than 2.