Small Amount Of Salt Research Articles

Efficient depolymerization of kraft lignin using zinc chloride based (molten) salts

Lignin is an attractive feed for biofuels and biobased chemicals. We here report the conversion of kraft lignin (Lignoboost) to liquids by hydropyrolysis using a zinc based (molten) salt in a semi-batch reactor. m-Cresol was used to dissolve and inject the lignin into the heated and pressurized reactor containing the molten salt. The liquid yield and fraction of organics in the liquid was optimized by varying the process parameters (hydropyrolysis temperature, pressure, hydrogen gas flow rate and salt to lignin ratio). The highest liquid yield of around 78 wt% was obtained using small amounts of salts (2.5 wt% of salts based on lignin input, 350 °C, 30 bar, 33 wt% lignin in m-cresol, hydrogen flow rate of 160 mL/min). A larger excess of salts gave a lower liquid yield, implying that catalytic amounts of salts are preferred. In addition, small amounts of salts are essential for depolymerization and the formation of lower molecular weight components, as was evident by comparing experiments with and without salts. The liquid product was shown to consist of low molecular weight phenolics like dimethyl- and ethyl-cresol, methyl guaiacol and oligomers (GC-MS, 2DGC-FID, NMR and GPC analysis). The product oil may have potential for biofuel production when coupled with a catalytic hydrotreatment step to obtain hydrocarbons or, after downstream processing and catalytic conversions, to important biobased chemicals like green phenol.

Research on the Rheological Properties and Anti-Aging Mechanism of Paper-Black-Liquor-Modified Bitumen

The production process of the traditional paper making process produces a large amount of waste water, known as paper black liquor. It is needed to explore new ways of reusing this waste and replacing part of the base bitumen to reduce the consumption of non-renewable resources, such as petroleum, thus obtaining better environmental, economic, and social benefits. This paper analyses the feasibility of using paper black liquor, which contains a large amount of lignin, as a modifier for bitumen in the paper industry. Samples of modified bitumen were prepared with 15%, 30%, and 45% of the base bitumen replaced by paper black liquor, and a control group of base bitumen was prepared for testing. The samples were subjected to an 85 min short-term ageing test, FTIR scanning test, thermogravimetric test, frequency scanning test, MSCR test, and LAS test. The analysis of the FTIR and thermogravimetric tests showed that the paper black liquor was mainly composed of lignin and some cellulose, and contained a small amount of salts with Na ions; based on the results of the frequency scan, the compatibility analysis of the vGP curve showed that the modified bitumen was more compatible in the high-temperature range after short-term ageing, thus inferring that the water content of the concentrate had an influence on the compatibility, making it necessary to further investigate different optimum water contents to achieve the best performance and benefit. The incorporation of paper black liquor improved the rutting resistance and fatigue resistance of the modified bitumen, and also gave the paper-black-liquor-modified bitumen a better ageing resistance than the base bitumen. While demonstrating the feasibility of using paper black liquor as an bitumen modifier, this study also helps to provide a basis for theoretical applications of biomass materials in the field of road engineering.

Use of ultrafiltration/diafiltration for the processing of antisense oligonucleotides.

Ultrafiltration/diafiltration (UF/DF) has been the hallmark for concentrating and buffer exchange of protein and peptide-based therapeutics for years. Here we examine the capabilities and limitations of UF/DF membranes to process oligonucleotides using antisense oligonucleotides (ASOs) as a model. Using a 3 kDa UF/DF membrane, oligonucleotides as small as 6 kDa are shown to have low sieving coefficients (<0.008) and thus can be concentrated to high concentrations (≤200 mg/mL) with high yield (≥95%) and low viscosity (<15 centipoise), provided the oligonucleotide is designed not to undergo self-hybridization. In general, the oligonucleotide should be at least twice the reported membrane molecular weight cutoff for robust retention. Regarding diafiltration, results show that a small amount of salt is necessary to maintain adequate flux at concentrations exceeding about 40 mg/mL. Removal of salts along with residual solvents and small molecule process-related impurities can be robust provided they are not positively charged as the interaction with the oligonucleotide can prevent passage through the membrane, even for common divalent cations such as calcium or magnesium. Overall, UF/DF is a valuable tool to utilize in oligonucleotide processing, especially as a final drug substance formulation step that enables a liquid active pharmaceutical ingredient.

Influence of the Electrolyte for CO2 electroreduction on Cu Catalysts

Global warming and climate change due to emission of greenhouse gases such as CO2 have been recently a major threat to all living beings in the world. In this regard, CO2 electroreduction (CO2ER) has attracted considerable attention as it can mitigate the CO2 level in the atmosphere and produce value-added chemicals. Aqueous electrolytes are excellent choices for CO2ER due to non-toxicity, abundance, and low cost. However, the presence of the side hydrogen evolution reaction (HER) and low CO2 solubility in aqueous electrolytes have caused CO2ER to be inefficient. Electrolyte design has been reported as one of the methods to enhance the selectivity and activity. Electrolytes have the ability to enhance the selectivity and activity by altering the CO2 solubility, local CO2 concentration, pH, and conductivity. Additives can be a promising method to overcome the challenges of aqueous solutions. They can stabilize the intermediates on the surface and enhance CO2ER. In this study, the impact of the electrolyte composition on the CO2ER has been investigated by using electrochemical and spectroscopical methods.In order to study the impact of anions and cations in aqueous electrolytes, different salts (10 mM) with sodium (Na+) or 1-butyl-3-methylimidazolium [BMIM]+ as cation and bis(trifluoromethylsulfonyl)imide [NTF2]- or dicyanamide [DCA]- as anion were added to 0.1 M KHCO3. Results showed that a small amount of salts in the electrolyte can have a significant enhance on the selectivity and activity in CO2ER. NTF2-based electrolytes showed a high faradaic efficiency (FE%) for formate at -0.92 V vs. RHE likely due to high hydrophobicity and CO2 absorption capacity of the NTF2-salts. [BMIM][NTF2] showed the maximum FE (38.7%) for formate. This can be due to the interactions of [BMIM]+ with CO2 molecules and stabilizing the intermediates on the surface. On the other hand, [DCA]-based salts showed a high FE for hydrogen and a very low FE for hydrocarbons even at high overpotentials. We attributed this observation to the strongly adsorption of [DCA]- on the surface. X-ray photoelectron spectroscopy (XPS) also confirmed the strong adsorption of the [DCA]- anions on the surface. Strongly adsorbed DCA ions on the surface can promote hydrogen evolution reaction, destabilize the intermediates and suppress CO2ER. In-situ electrochemical quartz crystal microbalance (EQCM) also showed a higher mass loss for DCA-salts probably due to the displacement of water molecules by ions. Electrochemical impedance spectroscopy (EIS) showed that both cations and anions impact the solution resistance and charge transfer resistance. Comparing to [BMIM]+ containing electrolytes, Na-based salts showed a lower solution resistance due to the small size of Na+ ions and their high conductivity. However, the charge transfer resistance is more impacted by the anion nature. DCA salts showed a lower charge transfer resistance compared to NTF2 salts probably due to the enhanced HER which is kinetically faster than CO2ER. This study showed that how a small amount of additives can alter the selectivity and activity in CO2ER in aqueous electrolytes.

Effect of Heating Processes on Physical and Chemical Properties of Syrup from Sap of Nipa Palm (Nypa fruticans Wurmb.)

The purpose of this research was to improve the color quality of syrup production from nipa sap by optimized heating process. The treatment of heating at 100 °C until the sap concentrated to 48 oBrix, followed by reducing temperature to 80 °C until the sap reached 68 oBrix, was a preferred method to syrup production. The browning intensity of syrup was 2.08 and the HMF (5-hydroxymethyl-2-furfural) was 16.28 mg/kg. It was noticed that nipa syrup contained high sugar and small amount of salt (2.38%, db) due to area-based growth. Panelists accepted the syrup product by giving a 9-point hedonic scale of 6.81, 6.80, 7.01, 6.67 and 6.91 for color, odor, viscosity, taste, and overall liking, respectively. After storage for 12 weeks, the pH and acidity were not significantly changed. The viscosity decreased, including L* and b* except a*. Total microbial count as well as yeast and mold were less than 10 CFU/g, and the MPN of Escherichia coli was identified less than 3/g.

Characteristics of Aerosol Formation and Emissions During Corn Stalk Pyrolysis

The inevitable emission of aerosols during pyrolysis can negatively affect the downstream process and even pollute the environment. In this work, the characteristics of aerosols were investigated during corn stalk pyrolysis at 400–900 °C. The effects of other operation conditions on the aerosol emissions were also probed with online and offline instruments. Results show the yield of aerosol presents a regular change with temperature in a wide range ratio of 3.4–8.7 wt.%. The aerosol size distribution reveals a unimodal form mainly in the 1.1–2.1 μm accumulation range and the maximum emission achieved is about 35 mg/g for SR and SP at 500 °C. Nevertheless, SL gives about 34 mg/g at 600 °C. High temperature promotes the decomposition of polymers into partciles with small diameter (less than PM1.0). The microtopography of aerosol presents spherical droplets, elongated-like liquid and solid particles that form heterogenous or homogeneous aggregations, that also happen on account of collisions. Aerosols contain mostly organic matter, a small amount of salt and over 50% of volatile organic carbon molecules (VOCs) in the total organic carbon (OC). Proper gas flow, high vapor concentration and longer path way boost the yield of bio-oil and reduce the emission of aerosols. The direct contact is beneficial for adequate extraction, but also causes additional solvent emissions.

Scaled charges at work: Salting out and interfacial tension of methane with electrolyte solutions from computer simulations

The solubility of methane in water decreases when a small amount of salt is present. This is usually denoted as the salting out effect (i.e., the methane is expelled from the solution when it contains small amounts of salt). The effect is important, for instance the solubility is reduced by a factor of three in a 4 m (mol/kg) NaCl solution. Some years ago we showed that the salting out effect of methane in water can be described qualitatively by molecular models using computer simulations. However the salting out effect was overestimated. In fact, it was found that the solubility of methane was reduced by a factor of eight. This points to limitations in the force field used. In this work we have carried out direct coexistence simulations to describe the salting out effect of methane in water using a recently proposed force field (denoted as Madrid-2019) based on the use of scaled charges for the ions and the TIP4P/2005 force field for water. For NaCl the results of the Madrid-2019 force field significantly improve the description of salting out of methane. For other salts the results are quite reasonable. Thus the reduction of the charge of the ions also seems to be able to improve the description of salting out effect of methane in water. Besides this we shall show that the brine-methane interface exhibits an increased interfacial tension as compared to that of the water-methane system. It is well known that electrolytes tend to increase the surface tension of liquid water, and this seems also to be the case for the interface between water and methane.

Tribological Properties of Si3N4-hBN Composite Ceramics Bearing on GCr15 under Seawater Lubrication.

This paper concerns a comparative study on the tribological properties of Si3N4-10 vol% hBN bearing on GCr15 steel under seawater lubrication and dry friction and fresh-water lubrication by using a pin-on-disc tribometer. The results showed that the lower friction coefficient (around 0.03) and wear rate (10−6 mm/Nm) of SN10/GCr15 tribopair were obtained under seawater condition. This might be caused by the comprehensive effects of hydrodynamics and boundary lubrication of surface films formed after the tribo-chemical reaction. Despite SN10/GCr15 tribopair having 0.07 friction coefficient in the pure-water environment, the wear mechanismsits were dominated by the adhesive wear and abrasive wear under the dry friction conditions, and delamination, plowing, and plastic deformation occured on the worn surface. The X-ray photoelectron spectroscopy analysis indicated that the products formed after tribo-chemaical reaction were Fe2O3, SiO2, and B2O3 and small amounts of salts from the seawater, and it was these deposits on the worn surface under seawater lubrication conditions that, served to lubricate and protect the wear surface.

Uniaxial Compression on Salted Snow

ABSTRACT During snowfall loose snow sticks to the underlying pavement, forming a hard crust that can be difficult to remove. In order to ensure good road traffic safety, winter maintenance personnel use several operations, such as mechanical removal and chemical altering, to keep snow plowable. One chemical, commonly applied on roads, is sodium chloride (salt). Recent studies establish that very small amounts of salt are sufficient to weaken compacted snow substantially, meaning that the mechanical properties of salted snow are different from dry snow. This change in the mechanical properties of salted snow, however, has not been considered when studying tire–pavement interaction in snowy conditions. In an attempt to better understand salt snow as a material, this paper presents an experimental investigation of salted snow under uniaxial compression. The study examines the density and the loss of mass of snow after compression for different solution contents and compression speeds. Samples of snow were mixed with sodium chloride solution at different liquid contents. The snow samples were then compressed by an MTS uniaxial compression machine, up to an applied load of approximately 2 bars, roughly corresponding to the pressure applied by a car. Applied forces and dry density were measured for each test after compression. Based on the results carried out in this study, we found that: Salted snow gets a higher density after compaction compared to dry snow, also flows easier than dry snow, giving a larger loss of mass during uniaxial compression. The dry density after compaction increases with compaction speed for dry snow but decreases with compaction speed for salted snow. The effect of the solution on the compressibility and flowability of the material and its relevance for tire–pavement interaction are discussed.

Survey Research of Convenience Store Usage for Lunch Among College Students and Nutritional Examination of Convenience Store Box Lunches

Convenience stores are popular for quick food such as box lunch and rice ball in Japan. In order to obtain the lunch habit of college students, we conducted questionnaire survey for convenience store usages. Additionally we examined the nutritional values of convenience store box lunches as a part of the study whether student’s diet meet the Dietary Reference Intakes for Japanese. Subjects were 450 college students (male 27, female 422) with two colleges in Tokyo. The questionnaire consisted twelve items concerning lunch including healthy diet awareness and convenience store usage. For box lunch, 37 kinds were examined with its nutritional labeling. For lunch at campus, 58% of students brought the lunches from home, 25% bought at the convenience store, and 14% ate at the cafeteria. The most popular choices at the convenience store were rice balls (66%) and breads (56%). The ratio of male students chose cup-noodles was 22.2%, significantly higher than female. Regarding the side dishes choice of box lunch, 44% picked deep-fried chicken, 23% teriyaki-meat, and 20% hamburger steak, the meat dishes were preferred. The maximum salt amount of box lunches was 7.1g and the mean was 3.7±1.2g, thus some of them contains more than recommended daily intake value. Although the subject students knew vegetable and small amount of salt are important for healthy diet, they chose lunch with less vegetable and much salt. We learned that further consideration is necessary when purchasing lunch at convenience store to correspond with nutritional requirement.

Investigating salt decay of stone materials related to the environment, a case study in the St. James church in Liège, Belgium

Salt crystallization is recognized as a major cause of damage to porous building materials, threatening the sustainable preservation of our valuable built heritage. Unfortunately, the crystallization behavior of the detected salt mixtures is complex and not fully understood. While the deliquescence points of single salts are well documented, this is not the case for salts in a mixture where one is confronted with the presence of different cations and anions. In this paper the salt content of the murals and the limestone tracery of the main entrance porch from the sixteenth century church of St. James in Liège, Belgium is investigated and related to the climatic conditions of its environment. Concerning the salt load, the research consists of hygroscopic moisture content measurements, quantitative ion analyses, and the prediction of phase equilibria using the thermodynamic model ECOS/RUNSALT. This model can predict the salt crystallization sequences of a particular ion mixture. The output is mathematically evaluated with collected temperature and relative humidity data, which enables the calculation of the number of salt crystallization–deliquescence cycles. The results show that even small amounts of salts can cause damage over a long period of time when the environment causes frequent cycles of crystallization–deliquescence over time. It is shown how a mixture of small amounts of (double) salts, including hygroscopic ones, can have a significant effect on the decay of historic building materials in the case of daily changing climatic conditions and periods of extreme drought. As a result, the crystallization of double salts and hygroscopic salts such as calcium nitrate cannot be ignored. The scientific method and the results are described.

Cementation of sand due to salt precipitation in drying process

ABSTRACTSalt in soil can cause cementation effect and increase the shear strength and stiffness of soil during the drying process. In this paper, an experimental study is presented to explore the strength, stiffness, and particle level structure of a salt-cemented sand at the dry state. Unconfined compression tests were carried out on sands with various amounts of precipitated dry salt. Scanning electron microscopic and elemental analysis were also conducted. The study shows that the strength and stiffness of sand can increase significantly with salt content. The strength versus salt content curve displays a convex shape, instead of a concave shape as found in cemented or biocemented sands. This implies that the effect of dry salt on soil strength is strong at low levels of salt content. The microscopic and elemental analysis evidences that salt tends to precipitate at particle contacts and form bridges between particles at relatively low salt content. The results presented in the paper may explain why even small amount of salt can lead to an overestimation of soil strength.

A camera and image processing system for floc size distributions of suspended particles

The observation of floc size distribution (FSD) for quantitative description of its properties over a sufficient size range, from a few microns to a few millimeters, is still a challenge in most marine environments. In this study, an inexpensive image acquisition and processing system is developed for achieving this objective. Images are acquired by using a Sony Alpha NEX-5R camera body with a CMOS sensor, a Sony E-mount to Nikon F-mount adaptor, extension tubes, a Nikon macro lens, and a close-up lens that can identify flocs with a minimum size of 5μm. The light source and camera trigger are controlled by a micro-controller that was assembled for this project. These images are analyzed by using MATLAB Image Processing Toolbox. The processed floc size and their statistical distributions are confirmed with two available sample sets. The validated process is then applied to measure the steady state FSDs of kaolinite suspensions for different shear rates, suspended sediment concentrations, salinities, and a selected organic matter, guar gum. Although the presence of salt promotes flocculation of suspended kaolinite, only a small amount of salt, around 0.5ppt, is needed to reach the saturation status. Thus for the test salinities (0.5, 1, 2, 3, 5, and 9ppt), the measured FSDs show little difference among each other. On the other hand, guar gum affects kaolinite flocculation significantly and the maximum effect happens at a guar gum concentration around 15mg/L when the kaolinite concentration is around 0.52g/L. At this dosage the characteristic floc size is the largest.

Salt influence on MIBK/water liquid–liquid equilibrium: Measuring and modeling with ePC-SAFT and COSMO-RS

In biotechnological processes, salts might be present during reaction steps and in downstream processes. Salts are known to have a strong impact on phase equilibria of aqueous systems.In this work, the liquid–liquid equilibria (LLE) of ternary salt/MIBK/water mixtures were measured at 298.15 K and 1 bar up to the salt solubility limit. The salts studied in this work were NaCl, LiCl, KCl, NaNO3, LiNO3, Na2SO4, CH3COONa, and CH3COOLi. From these LLE measurements it was found that a high amount of salt is dissolved in the aqueous phase whereas only a very small amount of salt was detected in the MIBK phase. Further, the salting-out behavior of MIBK from the aqueous phase upon addition of different salts was investigated to study ion-specific effects.Two ion-specific models, ePC-SAFT and an extended version of COSMO-RS for electrolytes were used for modeling the binary system MIBK/water and ternary salt/MIBK/water systems. In case of the COSMO-RS based approach, the modeling results were fully predictive. In contrast, ion-specific binary interaction parameters between MIBK and ions were fitted to experimental LLE data of the ternary systems salt/MIBK/water when using ePC-SAFT. The results show that the COSMO-RS based approach allows for predicting the salt influence on LLE with acceptable accuracy, whereas ePC-SAFT allows for almost quantitative correlations of experimental data.

Effect of spray-drying process on physical properties of sodium chloride/maltodextrin complexes

The mixture of sodium chloride and maltodextrin was processed by spray-drying with various inlet temperatures (130, 140, 150, 160 and 170°C) or atomization pressure (60, 100, 140, 180 and 220kPa). Physical properties of spray-dried maltodextrin/NaCl powder were characterized such as surface area or morphological images and sensory evaluation was carried out to observe saltiness of maltodextrin/NaCl complexes. At the high atomization pressure produced smallest particle of maltodextrin/NaCl complexes and it was effective to be melted faster and then saltiness was also rapidly recognized compared with bigger complexes. In this study, although inlet temperature was not effective like atomization pressure processing, relatively lower inlet temperature influenced on maltodextrin/NaCl complexes during spray-drying. It was suggested that decrease of salt particle size could improve melting speed and it could be helpful to enhance intensity of saltiness with small amount of salt.

Prebiotic RNA synthesis by montmorillonite catalysis.

This review summarizes our recent findings on the role of mineral salts in prebiotic RNA synthesis, which is catalyzed by montmorillonite clay minerals. The clay minerals not only catalyze the synthesis of RNA but also facilitate homochiral selection. Preliminary data of these findings have been presented at the “Horizontal Gene Transfer and the Last Universal Common Ancestor (LUCA)” conference at the Open University, Milton Keynes, UK, 5–6 September 2013. The objective of this meeting was to recognize the significance of RNA in LUCA. We believe that the prebiotic RNA synthesis from its monomers must have been a simple process. As a first step, it may have required activation of the 5'-end of the mononucleotide with a leaving group, e.g., imidazole in our model reaction (Figure 1). Wide ranges of activating groups are produced from HCN under plausible prebiotic Earth conditions. The final step is clay mineral catalysis in the presence of mineral salts to facilitate selective production of functional RNA. Both the clay minerals and mineral salts would have been abundant on early Earth. We have demonstrated that while montmorillonite (pH 7) produced only dimers from its monomers in water, addition of sodium chloride (1 M) enhanced the chain length multifold, as detected by HPLC. The effect of monovalent cations on RNA synthesis was of the following order: Li+ > Na+ > K+. A similar effect was observed with the anions, enhancing catalysis in the following order: Cl− > Br− > I−. The montmorillonite-catalyzed RNA synthesis was not affected by hydrophobic or hydrophilic interactions. We thus show that prebiotic synthesis of RNA from its monomers was a simple process requiring only clay minerals and a small amount of salt.

Study on Capacitance Evolving Mechanism of Polypyrrole during Prolonged Cycling

A simple model on the evolution mechanism of PPy capacitance during prolonged cycling offers a reasonably description on the rapid increase and decay of PPy capacitance in 1 M 1-ethyl-3-methylimidazolium tetrafluoroborate/propylene carbonate (EtMeImBF4/PC). The capacitance of PPy films reached a very high specific capacitance of 420 F·g(-1) after 15 cycles when they worked in 1 M MeEt3ImBF4/PC. However, the capacitance rapidly decreased to 5% after only 400 cycles. The electronic conductivity and protonation level on the nitrogen site of PPy films rapidly decreased with the increase of cyclic number. The salt of EtMeImBF4 was monitored in PPy matrix by FTIR spectra after 400 cycles. The EQCM results indicated that a lot of 1-ethyl-3-methylimidazolium cations (EtMeIm(+)) were inserted during reduction process and retained in PPy matrix. The detained EtMeIm(+) cations bonded with doped p-toluenesulfonate anions (PTS(-)) in PPy matrix or BF4(-) anions from electrolyte and formed salts. Small amount of salts in PPy matrix can open more channels of ion insertion and resulted in a very high capacitance after 15 cycles. The continuous combination of detained EtMeIm(+) cations with doping anions of PTS(-) resulted in the rapid decrease of PPy protonation level on the nitrogen site and formation of compensate semiconductor state in PPy matrix. This should be responsible for the rapid decay of PPy conductivity and capacitance. The continuous accumulation of salts resulted in the great increase of PPy internal resistance.

Thermodynamics of Block Copolymers with and without Salt

Ion-containing block copolymers are of interest for applications such as electrolytes in rechargeable lithium batteries. The addition of salt to these materials is necessary to make them conductive; however, even small amounts of salt can have significant effects on the phase behavior of these materials and consequently on their ion-transport and mechanical properties. As a result, the effect of salt addition on block copolymer thermodynamics has been the subject of significant interest over the past decade. This feature article describes a comprehensive study of the thermodynamics of block copolymer/salt mixtures over a wide range of molecular weights, compositions, salt concentrations, and temperatures. The Flory-Huggins interaction parameter was determined by fitting small-angle X-ray scattering data of disordered systems to predictions based on the random phase approximation. Experiments on neat block copolymers revealed that the Flory-Huggins parameter is a strong function of chain length. Experiments on block copolymer/salt mixtures revealed a highly nonlinear dependence of the Flory-Huggins parameter on salt concentration. These findings are a significant departure from previous results and indicate the need for improved theories for describing thermodynamic interactions in neat and salt-containing block copolymers.

Controlled Hydrolysis Synthesis and Luminescence Properties of Uniform TiO2 Spheres with Different Titanium Alkoxides

A series of uniform and well-dispersed TiO2 spheres have been successfully synthesized through a controlled hydrolysis route by using different titanium alkoxides as reactants. The types of titanium alkoxides and stirring time have an effect on the uniformity and dispersion of the TiO2 spherical particles. The addition of a small amount of salt also plays a crucial role for the formation of the monodisperse TiO2 spheres. Under ultraviolet excitation, the as-obtained Eu(3+)-doped TiO2 spheres exhibit red emission corresponding to the electric-dipole allowed 5D0-7F2 transition of Eu3+ ions, which is induced by the lack of inversion symmetry at the Eu3+ ions site. The Eu(3+)-doped TiO2 phosphors might find potential applications in the fields such as optical displays, photoelectric devices, and light-emitting diodes (LEDs).

Mass transfer in the wake of non-spherical air bubbles quantified by quenching of fluorescence

Based on planar laser induced fluorescence with inhibition (PLIFI) experiments, the mass transfer behavior in the wake of single rising air bubbles is investigated. Bubbles of equivalent diameters ranging from 0.90 to 2.24mm are studied, exhibiting vertical and zigzagging paths when they rise in the liquid. The transferred mass in the wake of such bubbles, considered as spherical or oblate ellipsoids, is directly visualized and represented in three dimensions for some cases. A specific image processing and mathematical approach are proposed to accurately quantify the mass transfer rate by estimating the liquid side mass transfer coefficient and flux density. After a comparison of liquid side mass transfer coefficients with values of the literature, this approach is tested to evaluate first the influence of bubble diameters and that of the liquid composition on the mass transfer. Liquid media with small amount of salt, glucose and glycerol, inducing surface tension and/or viscosity changes, are considered. A significant decrease in the mass transfer efficiencies, down to 88% depending in the added component, is observed and analyzed for these different liquids.