Surfactant Concentration In Water Research Articles

Laser diagnostics of self-organization of amphiphiles in aqueous solutions on the example of sodium octanoate

In this study, a method of non-contact laser diagnostics of self-organization processes of surfactants in aqueous solutions is proposed. The study of solutions of sodium octanoate using laser Raman and near-IR spectroscopy has shown that spectral bands of stretching vibrations of CC-, CH- and OH-groups (including second overtone of the OH-vibrations) of the surfactant molecules and water, as well as bands of intermolecular vibrations of hydrogen bonds O-H⋯O are sensitive to the change the conformation of the hydrocarbon radical of the surfactant and the dynamics of hydrogen bonds during self-organization of surfactants in solution. It was found that the dependence of the spectral characteristics of these bands on concentration of surfactants has peculiarities in the region of critical premicelle concentration (CPMC), first critical micelle concentration (CMC1) and second critical micelle concentration (CMC2). A method of determining the critical concentrations of surfactants in water based on the revealed peculiarities is proposed. A comparative analysis of the obtained CMC values using laser Raman and IR spectroscopy and those measured by independent contact methods – pH-metry, conductivity, surface tension measurement – has shown a good match of the determined parameters. Advantages of the method of laser diagnostics of surfactant self-organization in water were discussed.

Enhancement of Nucleate Pool Boiling Heat Transfer with Sodium Oleate

In this study saturated nucleate pool boiling of water with sodium oleate surfactant on a horizontal cylindrical heater surface has been investigated experimentally and compared with that of demineralized water. The concentration of sodium oleate in water was 100-300 ppm. The experimental results show that a small amount of surfactant enhances the heat transfer coefficient significantly. At low surfactant concentrations, heat transfer coefficient increases with increasing surfactant concentration in water. The maximum heat transfer enhancement is found to be at 250 ppm of sodium oleate solution. By adding more surfactant to water, heat transfer coefficient is found to be lowered. Surface tension of different concentration of sodium oleate solutions is measured. It is observed that the maximum heat transfer coefficient is obtained at a surfactant concentration that corresponds to the critical micelle concentration (cmc) of the sodium oleate solution.Journal of Chemical Engineering, Vol. 29, No. 1, 2017: 44-48

Measurement of Surfactant Concentration Using Light Scattering Method

A method for measuring the concentration of surfactant in water was developed. In this technique, microbubbles were used as light scatterers. The polarization change of light scattered by microbubbles was analyzed by Mueller matrix analysis. M₁₁, one of the Mueller matrix elements, was found to be a key parameter inferring the surfactant concentration within the concentration range of 0 ppm to 60 ppm. The best results for this measurement were obtained when the scattering angle was 150° and the extinction ratio was 56.2. This experimental result shows that the EPLS can be effectively used as a real time inspection method for water quality monitoring in lakes or rivers. Key words: Light Scattering, Micro-Bubble, Polarization, Mueller Matrix, Surfactant Concentration

Characteristics of micro-nano bubbles and potential application in groundwater bioremediation.

Content of oxygen in water is a critical factor in increasing bioremediation efficiency for contaminated groundwater. Micro-nano bubbles (MNBs) injection seems to be an effective technique for increasing oxygen in water compared with traditional air sparging technology with macrobubbles. Micro-nano bubbles have larger interfacial area, higher inner pressure and density, and lower rising velocity in water, superior to that of macrobubbles. In this paper, MNBs with diameters ranging from 500 nm to 100 microm are investigated, with a specific focus on the oxygen mass transfer coefficient from inner bubbles to surrounding water. The influence of surfactant on the bubbles formation and dissolution is studied as well. The stability of MNBs is further investigated by means of zeta potential measurements and rising velocity analysis. The results show that MNBs can greatly increase oxygen content in water. Higher surfactant concentration in water will decrease the bubbles size, reduce the dissolution rate, and increase the zeta potential. Moreover, MNBs with greater zeta potential value tend to be more stable. Besides, the low rising velocity of MNBs contributes to the long stagnation in water. It is suggested that micro-nano bubble aeration, a potential in groundwater remediation technology, can largely enhance the bioremediation effect.

Experimental Determination of Bubble Size in Solution of Surfactants of the Bubble Column

This paper focuses on the effect of surfactants on the bubble size. Bubble size in Sodium dodecyl sulfate /water system were investigated at various superficial gas velocities (0.13, 0.26 and 0.5 cm/s). On the other hands, Bubble diameter was determined for different values of Sodium dodecyl sulfate surfactant concentration. Surfactant concentration in water were 0.05, 0.02 and 0.1 vol.%. Tap water and aqueous solutions with surfactants (anionic, non-ionic and zwitterionic) are used as liquid phases. The bubbles size in this phase is determined at Cs=0.05%vol and ug=0.13 cm/s. The bubbles are generated into a small-scale bubble column making of Plexiglas with height of 1.2 m. High speed photography techniques are used to measure the bubble size. The experimental results were shownthat bubble diameter in Sodium dodecyl sulfate /water system is larger than other systems. In solution of Sodium dodecyl sulfate, Sauter mean bubble diameter (Location A and D) decreases when superficial gas velocity increased.

Structural Investigation of Nonionic Fluorinated Micelles by SANS in Relation to Mesoporous Silica Materials

In an attempt to answer the question if there is dependence between the pore ordering of the mesoporous silica, obtained through the cooperative template mechanism, and the shape of the micellar aggregates of the surfactant solutions, the micellar structures of two nonionic fluorinated surfactant based-systems are studied by SANS. By fitting the experimental spectra with theoretical models, the structural evolution of the molecular aggregates can be described, and some important parameters can be obtained, such as the water and eventually oil penetration into the surfactant film, the aggregation number, the area per polar head of the surfactant, and the surfactant chain conformations. We have shown that for the C(8)F(17)C(2)H(4)(OC(2)H(4))(9)OH system, the micelles are prolate spheroids. The increase of the surfactant concentration in water does not change the characteristics of the interfacial film, but the aggregation number raises and the particles become more elongated. By contrast, the experimental curves of C(7)F(15)C(2)H(4)(OC(2)H(4))(8)OH cannot be fitted considering a small particle model. However, progressive incorporation of fluorocarbon induces a change of size and shape of the globules, which become smaller and more and more spherical. Regarding the material mesopore ordering, it appears that the micelles that lead to hexagonal mesoporous silica materials are described with a model of quasi-spherical globules. On the contrary, when large micelles are found, only wormhole-like structures are obtained.

The processes of dissolution and hydrate forming behind the shock wave in the gas–liquid medium with gas mixture bubbles

The processes of dissolution and hydrate forming behind the front of the shock wave, propagating in liquid with bubbles of carbon dioxide and nitrogen mixture, have been experimentally studied under various initial pressures, medium temperatures and surfactant concentrations in water. The theoretical model of this process is presented for the gas–liquid medium with bubbles of multicomponent gas mixture with consideration of accompanying heat effects. Numerical solutions to this problem were found. Close fit of calculation results and experimental data was achieved. Experimental data on profiles of gas content, times of dissolution and hydrate forming were generalized on the basis of the suggested model.

Study of the formation of micro and nano-droplets containing immiscible solutions

There is currently significant interest in the multiple resistance to treatment using drugs (MDR), developed by bacteria and malignant tumors. One of the alternatives to the existing medicines and treatment procedures in fighting MDR is strengthening the effects of cytostatics by improving their delivery methods. Such a method is represented by the generation, transport and use of micro-/nano-droplets which contain medicines. This approach can reduce the medicines consumption by generating micro-droplets which contain drugs incorporated in solvents substances; the micro-/nano-droplets can favour a faster delivery to the targets and a higher drug concentration in them. This paper reports first, results concerning the generation of single micro-droplets containing an inner core (medicine solution in water) and a thin layer of oily liquid covering it. This generation is made one by one and it is, at the moment, not conceived as a method for mass production, or in other words for high population of such droplets. We have generated and measured stratified micro-droplets, each of them containing a solution of Vancomycin in ultrapure water as a core and a surrounding layer of Vitamin A in sunflower oil; the micro-droplets generation was made using a double capillary system. Secondly, micro-/nano-droplets were produced by mixing two immiscible solutions in particular conditions (high rotating speed and/or high pressure difference). For this we have studied the generation of emulsions of Vitamin A diluted in sunflower oil and a solution of Tween 80 surfactant in distilled water. The concentration of surfactant in water was, typically, 4 × 10 −5 M. We have studied the dependence of the droplets dimensions in emulsion on the mixing rotation speed, agitation time and components ratio. The droplets diameters were measured using a light scattering method. It is found that at high enough energy input (high rotation speed, large pressure drop) and relatively small oil/water ratio, droplets diameters smaller than 100 nm were obtained.

Aggregation of Perfluoroctanoate Salts Studied by 19F NMR and DFT Calculations: Counterion Complexation, Poly(ethylene glycol) Addition, and Conformational Effects

The aggregation of perfluoroctanoate salts in H(2)O is studied by (19)F NMR on solutions of LiPFO, NaPFO, and CsPFO, without and with the addition of two poly(ethylene glycol) (PEG) oligomers of molecular weight 1500 and 3400 Da, respectively, and with the addition of suitable crown ethers. The (19)F chemical shift (cs) trends are monitored, at 25 °C, in a concentration range including the critical micellar concentration (cmc) or, in the presence of PEG, the critical aggregation concentration (cac). The cac values in the samples with PEG are lower than the cmc values of the corresponding samples without PEG; moreover, the (19)F cs trends above the cac and above the polymer saturation concentration reveal and help to explain some peculiarities of the aggregation process of PEG on PFO micelles, which, in the first step, seems to occur while the surfactant concentration in water is still increasing. Also in LiPFO/H(2)O or NaPFO/H(2)O solutions containing 12-crown-4 or 15-crown-5 ethers, suitable to complex Li(+) or Na(+) ions, respectively, the cmc decreases. On the other hand, the micellization process in the presence of crown ethers does not show other peculiarities. The prevailing conformations of the PFO chain are discussed on the basis of quantum-mechanical calculations. The theoretical chemical shifts were computed at the DFT level of theory, taking into account the effects of the environment by means of the IEF-PCM method. The helical structure is the most stable one, but anti conformations are easily accessible, in both the aqueous and fluorinated environment. The comparison between computed and experimental chemical shifts indicates that anti conformations are more important in the micelles than in water and in CsPFO micelles than in LiPFO or NaPFO ones.

Granulation Process for Producing Spherical Particles of a Rubber Antioxidant in a Water Cooling Tower

A new granulation technology for producing spherical particles of a rubber antioxidant and its key factors were studied. The granulation is based on the interfacial tension and immiscibility of the rubber antioxidant in water. Melted antioxidant was ejected from nozzles to form drops in air that fell into a water tower where they were cooled and solidified into spherical particles as they fell. After dewatering and air drying, spherical particles with a uniform size were obtained. Experiments performed on the granulation of antioxidant 4020 are described and the key factors, including falling height, drop temperature and surfactant concentration in water were studied. The mechanism of drop entrancement in water was analyzed and the stable operating conditions were investigated. The technology produces spherical particles with a uniform size using smaller equipment and is also suitable for producing spherical particles from other melted materials with similar physical properties.

Sorption of methyl-parathion and carbaryl by an organo-bentonite

The modification of bentonite clays by cetyltrimethylammonium bromide (CTMAB) surfactant via cation-exchange produces materials (“organo-clays”) with an increased capacity for sorbing organic compounds such as pesticides. The sorption from solutions of two nonionic pesticides, methyl-parathion and carbaryl, by an organo-bentonite has been investigated. The pesticides are partitioned into the surfactant. The distribution coefficients, K ss, show a strong dependence on surfactant loading of the bentonite. The surfactant configuration at the clay surface has a marked influence on the effective volume and density of the bound surfactant. At low surfactant loadings, the K ss values increased, reached a maximum, and then decreased as the extent of loading increased. At low loading levels, the surfactant appears to form a monolayer (organic film) that effectively adsorbs the pesticides, resulting in very high K ss values. At high loadings, the sorbed surfactant appears to form a bulk-like medium that behaves essentially as a distribution phase. As a result, the K ss values decreased appreciably, and became less dependent on the CTMAB loading. Moreover, when the surfactant concentration in water was greater than the critical micelle concentration, the surfactant uptake on the clay reaches a plateau and an increasing fraction of the micelles remain in solution, together with the pesticides which bound to them. The competition for the pesticides between the aqueous micelles and the sorbed surfactant leads to a decrease in distribution coefficients.

Unconventional vesicle-to-ribbon transition behaviour of diacyl glycerol amino acid based surfactants in extremely diluted systems induced by pH-concentration effects

A vesicle-to-ribbon transition has been observed in extremely dilute 1-O-(L-arginyl)-2, 3-O-di-decanoyl-sn-glycerol dichlorohydrate (1010R) surfactant systems by means of static light scattering. At concentration as low as 0.005 mM the solutions scattered significantly. From the angular dependence and molecular weight of the aggregates a vesicular structure is suggested. Increasing surfactant concentration in water induces the vesicle-to-ribbon transition at concentrations as low as 0.5 mM. This transition is accompanied by a strong decrease of scattered intensity and change in angular dependence. Lowering the pH at a fixed concentration can induce the same transition. Both parameters change the protonation of the surfactant, inducing an increase in preferred surfactant head-group area. Those findings are congruent with the observed surface tension behaviour as a function of surfactant concentration and suggests an explanation for the widely different critical micellar concentration (c.m.c.) as determined by different techniques.

Liquid crystals and microemulsions formed by mixtures of a non-ionic surfactant with palm oil and its derivatives

The phase behaviour of palm olein (PO) and its derivative oils (palm oil methyl esters and medium chain triglycerides) with Imbentin coco 6.9EO, an ethoxylated C 12–14 alcohol, in water has been investigated to identify compositions where microemulsions occur. The techniques used were the optical microscope phase penetration scan and small angle X-ray diffraction (SAXS). Mixed surfactant/oil samples were prepared at wt. ratios of 0.1:1, 0.25:1, 0.5:1 and 1:1 for the phase penetration scan. For SAXS analysis, the initial concentration of surfactant in water ( W) was fixed at 38% (w/w), which forms a hexagonal mesophase ( H 1). Palm oil methyl esters (POME) and medium chain triglycerides (MCT) were added to this at 0.04:1 (or 0.05:1 for MCT), 0.1:1, 0.2:1 (or 0.25:1 for MCT), 0.5:1 and 1:1 ratios of oil to surfactant. Schematic phase diagrams were constructed to document the changes of phase structures using both bulk samples and phase penetration scans techniques. The extent of microemulsion formation (or solubilisation) decreases in the sequence POME>MCT>PO, and increases substantially with temperature, particularly for POME and MCT. All of the oils destabilise the hexagonal phase; for POME and MCT there is an increase in the surfactant cloud point temperature by ca. 10 °C or more, but the temperature for the onset of the lamellar ( L α ) phase dispersion region ( W+ L α ) is hardly affected. There was a pronounced tendency for the lamellar phase formed in the presence of high oil concentrations and low water levels to have a reduced melting point. With the highest MCT levels a bicontinuous cubic phase (probably V 2) is present at 25 °C, although this phase is not present in the binary surfactant/water system. The X-ray diffraction results show that the average area per head group ( a o) at the micelle surface is decreased by the addition of the oils, consistent with the observation of a V 2 phase. Possible molecular mechanisms for this observation are discussed.

Genotoxicity and Cytotoxicity of 4-Nonylphenol Ethoxylate on Lymphocytes as Assessed by the Comet Assay

Surfactants, which are prevalent at industrial sites and in the environment generally, are potential risk factors in human carcinogenesis. The widespread industrial use of surfactants such as 4-alkylphenol ethoxylates and their prevalence in many cleaning products have provoked studies about surfactant concentrations in water and their toxicity levels. Up to now, these substances have mainly been tested on aquatic organisms. Though tests on human cell lines are rare. The alkaline Comet assay was performed to evaluate the genotoxicity of 4-nonylphenol ethoxylate, a biodegradable product of 4-alkylphenol ethoxylate, in human lymphocytes. Concentrations tested ranged from 0.15 to 150 µg/mL. Test concentrations of 10 to 15 µg/mL caused an increase level of DNA migration in human cells, but without inducing excessive toxicity (viability > 80%). Though induced levels of DNA migration starting at concentrations of 30 µg/mL may have been due to excessive levels of cytotoxicity (viability < 70%). Based on these data, 4-nonylphenol ethoxylate can induce DNA damage in human lymphocytes but at higher concentrations than are normally found in river or drinking water. However, considering the prevalence of surfactants, the measured genotoxicity of these substances is of concern. Further investigations on human target cells are necessary to evaluate the carcinogenic impact of surfactants and reconsider their environmental acceptance.

Assessment of polycrystalline graphites as sorbents for solid-phase microextraction of nonionic surfactants

Two polycrystalline graphites (pencil lead and glassy carbon) were used as sorbents for solid-phase microextraction of a nonionic alkylphenol ethoxylate surfactant (Triton X-100). Analyses were performed by reversed-phase HPLC-fluorescence detection. The presence of the benzene ring in the congeners of Triton X-100 also allowed their direct detection at λ ex=230 nm and λ em=310 nm. Variables such as time of adsorption, time of desorption and concentration of surfactant in water were evaluated. The method limit of detection was found to be 0.5 μg/l for Triton X-100, with a linear dynamic range of 0.5–150 μg/l. Results were compared to those obtained using polymeric fibers such as PDMS/DVB and Carbowax/TPR. The chemical resistance and low cost of the polycrystalline graphites are advantageous over commercially available SPME fibers.

Emulsion homo- and copolymerization of vinyl acetate in the presence of maleic-modified and unmodified silica

The emulsion homo- and copolymerization of vinyl acetate in the presence of maleic-modified and unmodified silica were investigated. The formation of surfactant admicelles onto the silica surface induces a decrease of the surfactant concentration in water. It was shown that an increase of the functionalization degree of the inorganic support led to a decrease of the initiator conversion during homopolymerization. The same effect, along with the increase of the initiator productivity, was caused by the enhancement of the amount of unmodified silica during the copolymerization of vinyl acetate with bis(2-ethylhexyl)maleate. Vinyl acetate copolymerization with the maleic-modified support was suggested by the oxidation phenomenon taking place during the heating of the formed polymers in air and by T g measurements.

Determination of a non-ionic surfactant by solid-phase microextraction coupled with high-performance liquid chromatography and on-line derivatization

Solid-phase microextraction coupled with high-performance liquid chromatography (SPME–HPLC) and fluorescence detection was used to determine an alcohol ethoxylate (Brij 56) and 1-hexadecanol in water samples. Determinations were achieved by extraction with polydimethylsiloxane–divinylbenzene (PDMS–DVB) SPME fibers and pre-column derivatization with 1-naphthoyl chloride in the presence of 4-(dimethylamino)pyridine (DMAP) as catalyst. Variables such as time of reaction and concentration of surfactant in water were evaluated. The limit of detection of the method was found to be 0.1 mg/l of Brij 56.

Molecular Association of Water-Soluble Calixarenes with Several Stilbene Dyes and Its Application to the Facile Determination of Cationic Surfactant Concentrations

Abstract The molecular association of water-soluble p-sulfonatocalix[n]arenes (1n; n = 4, 6, and 8) with several stilbene dyes (D) has been studied by spectrophotometric and 1H NMR methods. It was found that 1n reacts in 1 : 1 stoichiometry with, D such as 4-[(4-dimethylamino)styryl]-1-methylpyridinium (St–4Me), 2-[(4-dimethylamino)styryl]-1-methylpyridinium (St–2Me) and 2-[(4-dimethylamino)styryl]-1-ethylpyridinium (St–2Et) iodides to form their complexes (1nD). The apparent association constants for 18-complexes are larger by about ten times than those of 14- and 16-complexes. Examinations of the CPK molecular models and the spectrophotometric studies suggested that 14 complexes D mainly with its 1-methyl- or 1-ethylpyridinium group, whereas 16 complexes D either with its pyridinium ring or with its protonated dimethylamino group in a similar probability, and in 18-complexes the molecule is wholly incorporated into the cavity of 18. The absorbance of D, which was decreased by association with 1n, was regenerated by the addition of other colorless cationic surfactants (A) such as cetylethyldimethylammonium ion. Studies on the substitution reaction of 1nD with A indicated that a 1 : 1 complex (1nA) is formed by releasing a free dye molecule (D). This was applied to a convenient determination of the cationic surfactant concentration in water.

Surfactant Recovery from Water Using Foam Fractionation

The purpose of this study was to investigate the use of foam fractionation to recover surfactant from water. A simple continuous mode foam fractionation was used and three surfactants were studied (two anionic and one cationic). The effects of air flow rate, foam height, liquid height, liquid feed surfactant concentration, and sparger porosity were studied. This technique was shown to be effective in either surfactant recovery or the reduction of surfactant concentration in water to acceptable levels. As an example of the effectiveness of this technique, the cetylpyridinium chloride concentration in water can be reduced by 90% in one stage with a liquid residence time of 375 minutes. The surfactant concentration in the collapsed foam is 21.5 times the feed concentration. This cationic surfactant was easier to remove from water by foam fractionation than the anionic surfactants studied.

Bioavailability of sediment‐sorbed and aqueous surfactants to Chironomus riparius (midge)

AbstractThe bioavailability of sediment‐sorbed and soluble fractions of three surfactants were compared in egg hatchability and partial life cycle chronic bioassays with the midge Chironomus riparius. The chemicals tested were linear alkyl (dodecyl) benzene sulfonate (LAS), dodecyl trimethyl ammonium chloride (TMAC) and distearyl dimethyl ammonium chloride (DSDMAC). Midge eggs exposed to ranges of surfactant concentrations in water were monitored for hatching success and posthatch survival. No significant reductions in egg hatching were observed at the highest concentrations tested: 18.9 mg/L LAS, 21.5 mg/L DSDMAC and 15.4 mg/L TMAC. Newly hatched larvae were more sensitive than eggs; respective 72‐h LC50 concentrations (48‐h for TMAC) were 2.2, 11.3 and 14.6 mg/L. In partial life cycle chronic bioassays in sediment/water test systems, percentages of winged adults emerging after continuous exposure of larvae and pupae to doses of each surfactant were determined. Exposure concentrations in sediment, interstitial water and overlying water were monitored by 14C liquid scintillation counting. Lowest observed effect concentrations (LOECs) of sediment‐spiked surfactants were 319 to 993 μg/g (dry weight) LAS, 876 to 2,708 μg/g DSDMAC and &gt;3,084 μg/g TMAC (highest concentration tested). Corresponding no observed effect concentrations (NOECs) were 319 μg/g LAS, 876 μg/g DSDMAC and 3,084 μg/g TMAC. The NOECs are approximately 100, 1,000 and 10,000 times greater than respective NOECs of the solubilized materials, and exceed levels of these materials measured in the environment. The results indicated that adsorption onto sediment significantly mitigates surfactant bioavailability to Chironomus.