Surface Tension Of Pure Water Research Articles

Effect of aging time, airflow rate, and nonionic surfactants on the surface tension of bulk nanobubbles water

• Effects of aging time and airflow rate on the surface tension of bulk NB water are investigated. • Effects of airflow rate on the surface tension of bulk NB water is discussed. • The surface tension of bulk NB water is affected by the presence of NBs in the gas–liquid interface. • The surfactant adsorption affected by NBs in the gas–liquid interface determines the surface tension. Nanobubbles have attracted considerable and ever increasing scientific and commercial interest in the past two decades. The main interest focuses on the observation that they are colloidally stable showing various potential applications including flotation, wastewater treatment, cleaning. Here, we report a systematic study studying the surface tension of bulk nanobubbles (BNBs) in water with respect to the aging time and airflow rate. Further, the interfacial tensions of methyl isobutyl carbinol (MIBC) and 2-octanol solutions in the presence and absence of BNBs has been investigated. This study showed that the surface tension of freshly generated nanobubble water is significantly lower than the surface tension of pure water and gradually increase with time until it reaches 70.5 mN/m. Further, a reduction in surface tension and an increase in nanobubbles size were observed when airflow rate was increased. The surface tensions of mixed nanobubbles with methyl isobutyl carbinol (MIBC) was lower than those without nanobubbles, unlike nanobubbles mixed with 2-octanol solutions which led to an increase in the surface tension compared to those without nanobubbles. A possible mechanism for the change in the surface tension in nanobubbles mixed with nonionic surfactant is discussed.

Discovery of Graphene-Water Membrane Structure: Toward High-Quality Graphene Process.

It is widely accepted that solid‐state membranes are indispensable media for the graphene process, particularly transfer procedures. But these membranes inevitably bring contaminations and residues to the transferred graphene and consequently compromise the material quality. This study reports a newly observed free‐standing graphene‐water membrane structure, which replaces the conventional solid‐state supporting media with liquid film to sustain the graphene integrity and continuity. Experimental observation, theoretical model, and molecular dynamics simulations consistently indicate that the high surface tension of pure water and its large contact angle with graphene are essential factors for forming such a membrane structure. More interestingly, water surface tension ensures the flatness of graphene layers and renders high transfer quality on many types of target substrates. This report enriches the understanding of the interactions on reduced dimensional material while rendering an alternative approach for scalable layered material processing with ensured quality for advanced manufacturing.

Study on the microscopic mechanism and optimization of dust suppression by compounding biological surfactants

In order to solve the problem of reducing the surface tension of pure water used in some spray dust reduction equipment, this study analyzed the action mechanism of the green biodegradable dust suppressant on coal dust from a microscopic point of view. Using orthogonal experiment design and response surface analysis method, the surface tension change of the green biodegradable composite dust suppressant and its influence on the wettability of coal dust is studied, several biological surfactants are added to water in nine groups in different proportions to prepare dust suppressants with the same total concentration. Through nine sets of sedimentation experiments with different configuration ratios, it is concluded that each set of compound dust suppressants can improve the wetting speed of coal dust to varying degrees. In the infrared spectroscopy experiment, we analyze the microscopic interaction mechanism of coal dust, compare the wettability of anthracite coal samples before and after treatment with the same quality dust suppressant through the change of functional groups. The internal mechanism of the biodegradable dust suppressant is explained from a two-dimensional curve, the low hydroxyl transmittance means high content, which effectively increases the hydrophilic groups on the surface of coal dust, thereby accelerating the wetting speed. The surface tension experiment showed that the use of compound reagents had a good synergistic effect. The lowest surface tension of the biodegradable dust suppressant is 28.515 mN/m in nine groups. Through response surface analysis method, the study finds the optimal value of the wetting speed of the dust suppressant, obtains the best ratio of each reagent in this new dust suppressant by using Design Expert 11.0. The optimal ratio is calculated as: 0.129 ml rhamnolipid, 0.044 ml lactone sophorolipid and 0.029 g surfactin per 100 ml of dust suppressant, the shortest wetting time is 31.777 s. • A biological compound dust suppressant with excellent wetting effect was prepared. • The hydrophilic functional groups on the surface of coal dust was changed by the composite dust suppressant. • The lowest surface tension of the biodegradable dust suppressant is 28.515 mN/m. • The optimal ratio of the dust suppressant is rhamnolipid 12.9%, lactone sophorolipid 4.4%, Surfactin 2.9%.

Characterization of seawater and aerosol particle surfactants using solid phase extraction and mass spectrometry

Surface-active organic molecules (surfactants) may influence the ability of an aerosol particle to act as a cloud condensation nuclei by reducing its surface tension. One source of organic mass in aerosol particles, which may also contain surfactants, is bubble bursting on the sea surface. In order to directly compare these molecules in the ocean and aerosol particles, we developed a method using multiple solid phase extractions and high resolution mass spectrometry to characterize surface active organic molecules in both. This method has extraction efficiencies greater than 85%, 75%, and 60% for anionic, cationic, and nonionic surfactant standards, respectively. In this study, we demonstrate the presence of three ionic classes of surface active organics in atmospheric aerosol particles and estuarine water from Skidaway Island, GA. With this extraction method, organic molecules from both estuarine water and atmospheric aerosol particles significantly reduced surface tension of pure water (surface tension depression of ~ 18 mN/m) and had high ratios of hydrogen to carbon (H/C) and low ratios of oxygen to carbon (O/C), indicative of surfactants. While previous work has observed a larger fraction of anionic surface active organics in seawater and marine aerosol particles, here we show cationic surface active organics may make up a large fraction of the total surface active molecules in estuarine water (43%–47%).

Dissolution and Surface Tension Properties of Ethanol-Wash Solute Obtained from Industrial Sunflower Meal

Sunflower meal ethanol-wash solute (SEWS) is one of the products obtained from a procedure for the complete valorization of industrial sunflower meal. The meal was subjected to a 4-step treatment with aqueous ethanol solution (75%) followed by vacuum concentration and lyophilization of spent ethanol wash liquids to generate powdery SEWS. The purpose of this study was to evaluate surface tension and dissolution of SEWS in water in response to two variables, concentration (0.1%, 0.3%, 0.5%) and temperature (20°C, 30°C, 40°C, 50°C). The rate constants of 0.1% and 0.3% SEWS dissolution increased in response to temperature elevations up to 40°C. For both concentrations, the dissolution at 50°C was slowed down, which resulted in deviations of the Arrhenius plot from linearity. No linear fit between rate constants and temperature increase for 0.5% SEWS was established. The addition of SEWS decreased the surface tension of pure water at all three concentrations. The most profound effect was observed at 50°C where water's surface tension (67.14 mN/m) was reduced 1.81-fold (37.35 mN/m) after adding 0.5% SEWS. Acquired characteristics are a valuable part of the SEWS's applicable profile needed for the potential use of the product in the food, nutraceutical, or agricultural industries.

Enhancement of glycolipid production by Stenotrophomonas acidaminiphila TW3 cultivated in low cost substrate

This study aimed to investigate potential biosurfactant production of Stenotrophomonas acidaminiphila TW3 isolated from sediments contaminated with palm oil soapstocks using low cost substrates. The combination of central composite rotatable design (CCRD) and response surface methodology (RSM) was used to optimize biosurfactant production. The highest biosurfactant production (2.31 g/L) was obtained under the optimal conditions of 49.96 g/L used palm oil as a carbon source, 3.00 g/L NaNO 3 as a nitrogen source and medium pH 6.0. RSM increased the yield of biosurfactant up to 2.1 folds however, the productivity is still low further improvement is needed. The biosurfactant obtained from the S. acidaminiphila TW3 was able to lower the surface tension of medium from 72 to 32 mN/m. The biosurfactant was purified by liquid column chromatography and identified as glycolipid using thin layer chromatography, Fourier transform infrared spectroscopy, Mass spectrometer and Nuclear Magnetic Resonance. The biosurfactant could reduce surface tension of pure water to 32 mN/m with a critical micelle concentration of 0.2 g/L. It is an effective biosurfactant over a wide range of temperatures, pH and salt concentrations. Moreover, the biosurfactant showed ability to enhance PAHs solubility and removed used lubricating oil contaminated in sand. • The production of biosurfactant by strain TW3 was optimized by RSM methodology. • The biosurfactant produced by strain TW3 was identified as glycolipid. • Biosurfactant activity was stable under extreme conditions. • This glycolipid increased PAHs solubility and removed ULO.

Correlation and prediction of surface tension in single and mixed aqueous electrolyte solutions based on the mean ionic activity coefficient: A comparative analysis of Pitzer, E-NRTL and E-UNIQUAC models

Li and Lu's model to calculate the surface tension of single and mixed aqueous electrolyte solutions, coupled with Pitzer, e-NRTL and e-UNIQUAC activity coefficient models, is critically evaluated in this paper. Parameters of these activity coefficient models were taken from vapor-liquid equilibrium data available in the literature. The effect of the mean ionic activity coefficient model on the surface tension calculation is investigated in order to obtain low deviations from experimental data with emphasis on salt reservoir applications. An evaluation is made of the magnitude of the percentage surface tension increment relative to the surface tension of pure water, which occurs due to an increase in salt concentration. The feasibility of interpolation and extrapolation of the surface tension model with respect to the temperature was investigated for single electrolyte solutions at several temperatures. A sensitivity analysis of the initial guesses of the Li and Lu's model when adjusting the model parameters was performed. A new approach is also proposed to estimate the Pitzer parameters for some systems. This study explores the Li and Lu's model as never found in the literature before and is generally able to provide more accurate surface tension calculations compared with previous works. The results show that for single electrolyte solutions, the Pitzer and e-NRTL models provide similar deviations with an overall AAPD of 0.49%. For mixed electrolyte solutions, the e-NRTL model performed better than the Pitzer and e-UNIQUAC, providing an overall AAPD of 0.42%. The simulated increments of surface tension due to addition of salt are in accordance with the literature. The sensitivity analysis demonstrates the relevance of well adjusting the initial guesses for parameter estimation. Interpolation and extrapolation analysis yielded quite acceptable deviations with all overall AAPDs lower than 1.40% and also indicated that e-NRTL model is the most accurate. The proposed approach to fit the Pitzer model parameters provided an average deviation of 0.75%.

Surface tension in bulk and bounded liquids

The paper is aimed at theoretical studying the following problems and its relation to the available experimental data: 1) the coefficient of surface tension and capillary constant in bulk and spatially bounded liquids in a wide range of thermodynamic parameters (temperature, density, pressure, etc.), including the critical region; 2) influence of size effects on surface tension and capillary constant in liquids with a varying spatial dimensionality, namely from the “surface” 2D-state to the “bulk” 3D-state, and then to regular 4D-state where the fluctuation effects may be neglected in liquids like water with the Ginzburg number, Gi < 1; 3) comparison the obtained results and empirical approach to the water surface tension in a wide intervals of thermodynamic variables, including confined supercooled water; 4) medical application of results for surface tension, using similarity between processes of carcinogenesis and nucleation.The theoretical formulas are proposed for dependence of surface tension and capillary constant in bulk and confined liquids on temperature, density, pressure, and size variables in a wide vicinity of the critical region. The agreement of theoretical and experimental data for the temperature dependence of surface tension and capillary constant appears to be quite satisfactory. The 2D↔3D dimensional crossover for surface tension and capillary constant is analyzed. The surface tension of liquids with a relatively small Ginzburg number, including bulk water, is studied with taking into account the dimensionality crossover from 3D-systems to 4D-systems, where the Landau mean-field theory is valid. The empirical formula for surface tension of pure water is discussed together with the Tolman correction and the fluctuation theory of phase transitions. The consequences of the similarity hypothesis of nucleation and carcinogenesis are discussed.

Magnetic Field Effects on Aqueous Anionic and Cationic Surfactant Solutions Part II: Surface Tension

Magnetic Field (MF) effects on water and dispersed systems have been studied for more than half of century. However, so far there is no complete understanding of the observed changes in the properties of studied systems if it is solely based on the classical theories of magnetic field action. In Part I of this paper we presented results of MF influence on the evaporation rate of aqueous solutions of anionic surfactant Sodium Dodecyl Sulphate (SDS) and cationic one Dodecyl Trimethylammonium Bromide (DoTAB). In this paper static magnetic field effects on the surface tension of the above-mentioned surfactants are presented. The concentrations of the solutions used were both below and above their Critical Micelle Concentration (CMC). The solutions were under the MF action for 60 min in a closed vessel and were stirred by hand every 15 min. Previously it was found that the surface tension of pure water (distilled in a quartz apparatus) decreased by 2.1 mN/m after similar the MF treatment. Moreover, the memory effect lasted longer than 60 min. In case of the surfactant solutions the surface tension changed depending both on the kind of surfactant and its concentration. Bigger changes were observed for cationic DoTAB. In the solutions below their CMC the surface tension was lower after MF treatment. However, the surface tension of DoTAB solution at CMC increased several mN/m after the MF treatment. In the solutions concentrated above the CMC, respectively, the MF effects were practically vanishing. The observed changes are discussed in detail considering the structure of the surfactant adsorbed layers and acceleration force acting on the ions which was calculated from the Lorentz equation. To our knowledge, such results are published in the literature for the first time and they should be considered as preliminary ones. More systematic experiments are needed to better understand the observed changes.

Surface tension of seawater at low temperatures including supercooled region down to – 25 °C

The experimental apparatus used for the measurement of surface tension of supercooled water using a capillary rise technique [Hrubý et al. J. Phys. Chem. Lett 5 (2014) 425 and Vinš et al. J. Phys. Chem. B 119 (2015) 5567] was modified for the measurements with seawater. New data for the surface tension of IAPSO seawater standard were collected for a salinity range from 10 g/kg to 38 g/kg and at temperatures from 30 °C down to −25 °C. The reported measurements are relative to the surface tension of pure water at the reference temperature of 15 °C. The combined standard uncertainty of the relative surface tension is better than 0.30%. The new data do not indicate any anomaly in the temperature trend of the surface tension of low-temperature and supercooled seawater down to temperature of −25 °C. The data agree with other literature data measured at stable conditions above 0 °C. Recent correlation by Nayar et al. [J. Phys. Chem. Ref. Data 43 (2014) 043103], considered as a potential standard for the surface tension of seawater, shows a very good agreement with the new data both in the stable region and under the metastable supercooled conditions. The differences between the correlation and the experimental data are entirely within the experimental uncertainty. Consequently, the recommended range of validity of the correlation by Nayar et al. can be extended into the supercooled region down to −25 °C for salinity up to 38 g/kg. In addition, an alternative correlation for the surface tension of seawater compatible with the recent correlation by Pátek et al. [J. Chem. Eng. Data 61 (2016) 928] for pure water is introduced. The new correlation has the same form as that by Nayar et al., however with slightly modified coefficients. Both correlations for seawater provide comparable results over the temperature and salinity ranges of the available experimental data.

Cloud droplet activation properties and scavenged fraction of black carbon in liquid-phase clouds at the high-alpine research station Jungfraujoch (3580 m a.s.l.)

Abstract. Liquid clouds form by condensation of water vapour on aerosol particles in the atmosphere. Even black carbon (BC) particles, which are known to be slightly hygroscopic, have been shown to readily form cloud droplets once they have acquired water-soluble coatings by atmospheric aging processes. Accurately simulating the life cycle of BC in the atmosphere, which strongly depends on the wet removal following droplet activation, has recently been identified as a key element for accurate prediction of the climate forcing of BC. Here, to assess BC activation in detail, we performed in situ measurements during cloud events at the Jungfraujoch high-altitude station in Switzerland in summer 2010 and 2016. Cloud droplet residual and interstitial (unactivated) particles as well as the total aerosol were selectively sampled using different inlets, followed by their physical characterization using scanning mobility particle sizers (SMPSs), multi-angle absorption photometers (MAAPs) and a single-particle soot photometer (SP2). By calculating cloud droplet activated fractions with these measurements, we determined the roles of various parameters on the droplet activation of BC. The half-rise threshold diameter for droplet activation (Dhalfcloud), i.e. the size above which aerosol particles formed cloud droplets, was inferred from the aerosol size distributions measured behind the different inlets. The effective peak supersaturation (SSpeak) of a cloud was derived from Dhalfcloud by comparing it to the supersaturation dependence of the threshold diameter for cloud condensation nuclei (CCN) activation measured by a CCN counter (CCNC). In this way, we showed that the mass-based scavenged fraction of BC strongly correlates with that of the entire aerosol population because SSpeak modulates the critical size for activation of either particle type. A total of 50 % of the BC-containing particles with a BC mass equivalent core diameter of 90 nm was activated in clouds with SSpeak≈0.21 %, increasing up to ∼80 % activated fraction at SSpeak≈0.50 %. On a single-particle basis, BC activation at a certain SSpeak is controlled by the BC core size and internally mixed coating, which increases overall particle size and hygroscopicity. However, the resulting effect on the population averaged and on the size-integrated BC scavenged fraction by mass is small for two reasons: first, acquisition of coatings only matters for small cores in clouds with low SSpeak; and, second, variations in BC core size distribution and mean coating thickness are limited in the lower free troposphere in summer. Finally, we tested the ability of a simplified theoretical model, which combines the κ-Köhler theory with the Zdanovskii–Stokes–Robinson (ZSR) mixing rule under the assumptions of spherical core–shell particle geometry and surface tension of pure water, to predict the droplet activation behaviour of BC-containing particles in real clouds. Predictions of BC activation constrained with SSpeak and measured BC-containing particle size and mixing state were compared with direct cloud observations. These predictions achieved closure with the measurements for the particle size ranges accessible to our instrumentation, that is, BC core diameters and total particle diameters of approximately 50 and 180 nm, respectively. This clearly indicates that such simplified theoretical models provide a sufficient description of BC activation in clouds, as previously shown for activation occurring in fog at lower supersaturation and also shown in laboratory experiments under controlled conditions. This further justifies application of such simplified theoretical approaches in regional and global simulations of BC activation in clouds, which include aerosol modules that explicitly simulate BC-containing particle size and mixing state.

Production and Application of Biosurfactant Produced by &lt;i&gt;Agrobacterium rubi&lt;/i&gt; L5 Isolated from Mangrove Sediments

An effective biosurfactant-producing bacteria, isolate L5, was isolated from mangrove sediments from both east coast and west coast of Southern of Thailand. Analysis of the 16S rRNA gene sequence confirmed that isolate L5 was Agrobacterium rubi with 100% homology. The biosurfactant production was performed using a mineral salt medium (MSM) with molasses as a carbon and commercial monosodium glutamate (MSG) as nitrogen sources. Under optimized conditions, A.rubi L5 was able to grow and produce biosurfactant with the yield of 4.62 g/l at 54 h of cultivation. It could reduce the surface tension of pure water from 72.0 to 25.5 mN/m and exhibit emulsification activity toward palm oil with 65.4%. The biosurfactant found to be stable even under extreme pH, temperature and salinity conditions. The results revealed the potential use of a biosurfactant produced by A. rubi L5 to enhance mobilization sorbed motor oil from environment in comparison with those of synthetic surfactants, i.e. a nonionic surfactant Tween 80 and anionic surfactants sodium dodecyl sulfate.

Production of sophorolipids by Starmerella bombicola yeast using new hydrophobic substrates

Sophorolipids (SLs) are surface active compounds that have excellent surface-lowering properties. Typically, SLs are produced using different hydrophobic substrates, such as alkanes, vegetable oils, and industrial effluents. The properties of the SLs are highly dependent on the hydrophobic substrate used for their production. The aim of the present study is to investigate the properties of SLs produced using three new hydrophobic substrates: Tapis oil, Melita oil, and Ratawi oil. The structures of the SLs were determined by Fourier transform infrared spectroscopy. The SLs yields using Tapis, Melita, and Ratawi oil were 26, 21, and 19gL−1, respectively. The SLs produced using Tapis, Melita, and Ratawi oil reduced the surface tension of pure water to 36.38, 37.84, and 38.92 mN/m, respectively, corresponding to critical micelle concentrations (CMCs) of 54.39, 55.68, and 58.34mgL−1. These values are comparable with SLs produced using palm oil (surface tension 35.38 mN/m and CMC 48.76mgL−1). The SLs produced using Tapis oil show a maximum emulsification activity of 71.2%. The produced SLs are active over the pH range 2–10 and for salinity up to 20% (w/v) NaCl. Thus, they show potential for various applications, including microbial enhanced oil recovery and oil spill remediation.

Molecular dynamics simulations of the surface tension of oxygen-supersaturated water

In this work, non-reactive molecular dynamic simulations were conducted to determine the surface tension of water as a function of the concentration of the dissolved gaseous molecules (O2), which would in turn help to predict the pressure inside the nanobubbles under supersaturation conditions. Knowing the bubble pressure is a prerequisite for understanding the mechanisms behind the spontaneous combustion of the H2/O2 gases inside the nanobubbles. First, the surface tension of pure water was determined using the planar interface method and the Irving and Kirkwood formula. Next, the surface tension of water containing four different supersaturation concentrations (S) of O2 gas molecules was computed considering the curved interface of a nanobubble. The surface tension of water was found to decrease with an increase in the supersaturation ratio or the concentration of the dissolved O2 gas molecules.

Adsorption of C14EO8 at the interface between its aqueous solution drop and air saturated by different alkanes vapor.

The dynamic and equilibrium surface tension for drops of aqueous C14EO8 solutions at the interface to pure air or pentane, hexane, heptane and toluene saturated air, and the dynamic surface tension of pure water at these interfaces are presented. Two theoretical models were employed: both assuming a diffusion controlled adsorption of the surfactant, and either a diffusion or kinetic barrier governed adsorption of the alkanes. The experimental results are best described by the model which implies a diffusion control for the C14EO8 molecules and the existence of a kinetic barrier for the alkane molecules. The desorption of alkanes from the surface layer after equilibration and their subsequent removal from the measuring cell was studied as well. The desorption process was shown to be slow for heptane and hexane. However, for the pentane vapor the desorption is quite rapid, and after the desorption commences the surface tension becomes equal to that at the interface with pure air.

Solid Flocculation and Emulsifying Activities of the Lipopolysaccharide Produced by Trichosporon mycotoxinivorans CLA2

The objective of this study was to evaluate the capability of a lipopolysaccharide, produced by Trichosporon mycotoxinivorans CLA2 using residue of biodiesel processing, to flocculate two different solids in suspension. In addition, the emulsifying activity and the stability of this lipopolysaccharide in response to pH and temperature variations and in the presence of some electrolytes were evaluated. The lipopolysaccharide was used in concentrations ranging from 20 to 80mgL-1 to flocculate 100 gL-1 of kaolin and 50 gL-1 of charcoal. The results indicated that the flocculating capability for each suspended particles reached 80% and 78.79% after 14min, respectively. Other tests indicated that the emulsifying activity is weakly affected by temperature, pH and NaCl. In addition, the surfactant activity was assessed by the droplet diameter method and tension surface measurement. The surface tension of pure water decreased gradually with an increase in the biopolymer concentration until a minimum of 52mNm-1 with a CMC value of 4.54mgL-1. These findings demonstrated a potential use of the bioemulsifier in flocculation and emulsification processes, which are also favored by its reduced toxicity compared to those of widely used commercial polymers.

Some properties of xanthan gum in aqueous solutions: effect of temperature and pH

The properties of xanthan gum (XG) aqueous solutions were investigated by using viscometric, electrokinetic and surface tension measurements. The effects of polymer concentration, temperature and pH on the viscosity of the XG solutions were evaluated and discussed. Zeta potential data determined for XG solutions in water in the temperature range of 15–45 °C corroborated with the results obtained from the viscometric investigations suggest the occurence of conformational changes above 36 °C. The activation energy of flow and that associated with the electrophoretic migration of the charged particles were estimated for XG solutions in water. In acid medium, xanthan gum determines a slight decrease of the surface tension of pure water at all investigated temperatures.

Optimization of iron chelating biosurfactant production by Stenotrophomonas maltophilia NBS-11

Abstract The biosurfactants are microbially produced amphiphilic molecules having unique surface active properties and gaining worldwide attention due to their wide scope applications. Cost competitiveness is the major concern associated with biosurfactant production and its applicability indicating scope for searching potent biosurfactant producers and optimization of a production process. The biosurfactant producing strain Stenotrophomonas maltophilia NBS-11 was isolated and identified, effect of growth conditions and nutritional parameters on biosurfactant production was studied, the production process was optimized using response surface methodology, the biosurfactant was identified chemically by FTIR and NMR analysis and the iron chelation capacity of biosurfactant was determined. The biosurfactant production was higher at pH 7.0, 37 °C, after 120 h of incubation and in presence of 2% dextrose, 1% peptone and 100 mM of ZnCl 2 and MgSO 4 respectively. Based on optimization, biosurfactant production by NBS-11 was increased to 2.1 fold over initial conditions with pH, dextrose, ZnCl 2 and MgSO 4 as critical control factors. The biosurfactant was a rhamnolipid and able to reduce surface tension of pure water from 71±0.5 mN/m to 29.3±0.9 mN/m with a critical micelle concentration of 0.25 mg/ml. The 65% iron chelating effect was observed at 2 mg/ml indicating its possible role in development of novel iron chelators.

Cloud droplet activation of mixed model HULIS and NaCl particles: Experimental results and κ-Köhler theory

Significant amounts of humic-like substances (HULIS) are present in marine submicrometer particles. The cloud condensation nuclei (CCN) activation was investigated for marine model particles comprised of Nordic Aquatic Fulvic Acid Reference (NAFA) and sodium chloride (NaCl) in mass ratios of 100:0, 80:20, 50:50, 20:80 and 0:100 respectively. The CCN activity of NAFA was found to be represented by a κ value of 0.028. The CCN activities of the mixed particles were overestimated by volume weighted addition of the κ values of the pure compounds, which indicates that synergistic effects of the mixtures tend to lower the CCN activity. Parameterizations of water activity (aw) and surface tension (σ) versus solute concentration were obtained from measurements on aqueous solutions. The CCN activity was modeled on the basis of the parameterizations of aw and σ using Köhler theory. For the particles containing 50% or more NAFA the model overpredicted the CCN activity compared to observations. Reasonable model results were obtained by assuming a surface tension of pure water.

Utilization of palm oil decanter cake as a novel substrate for biosurfactant production from a new and promising strain of Ochrobactrum anthropi 2/3

A biosurfactant-producing bacterium, isolate 2/3, was isolated from mangrove sediment in the south of Thailand. It was evaluated as a potential biosurfactant producer. The highest biosurfactant production (4.52g/l) was obtained when the cells were grown on a minimal salt medium containing 25% (v/v) palm oil decanter cake and 1% (w/v) commercial monosodium glutamate as carbon and nitrogen sources, respectively. After microbial cultivation at 30°C in an optimized medium for 96h, the biosurfactant produced was found to reduce the surface tension of pure water to 25.0mN/m with critical micelle concentrations of 8.0mg/l. The stability of the biosurfactant at different salinities, pH and temperature and also its emulsifying activity was investigated. It is an effective surfactant at very low concentrations over a wide range of temperatures, pH and salt concentrations. The biosurfactant obtained was confirmed as a glycolipid type biosurfactant by using a biochemical test, fourier-transform infrared spectroscopy, MNR and mass spectrometry. The crude biosurfactant showed a broad spectrum of antimicrobial activity and also had the ability to emulsify oil and enhance polyaromatic hydrocarbons solubility.