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Numerical Study on Vapor Absorption into Aqueous LiBr Solution in a Liquid-gas Ejector Using Convergent Nozzle  [cached]
Rui Wang,Hongtao Gao
Research Journal of Applied Sciences, Engineering and Technology , 2013,
Abstract: In this study, we have a numerical study on vapor absorption into aqueous LiBr solution in a liquid-gas ejector using convergent nozzle. A model of heat and mass transfer process in absorption of water vapor into a lithium bromide solution in liquid-gas ejector was developed. The model can predict vapor entrainment rate and mass fluxes. The effect of operating condition has been investigated. It has been observed that the absorption mass flux and the vapor entrainment rate increase as the mass flow rate of the inlet solution increases, the inlet solution concentration increases, the inlet solution temperature decreases and the absorber pressure increases. In our results, we get that the mass flux and vapor entrainment rate increases with the mass flow rate, inlet solution concentration, absorber pressure; the mass flux and vapor entrainment rate increases as the inlet solution temperature decreases; the mass flux rapidly decreases at first and slowly to zero value along flow direction.
Determination of lead in water resources by flame atomic absorption spectrometry after pre-concentration with ammonium pyrrolidinedithiocarbamate immobilized on surfactant-coated alumina
Journal of the Serbian Chemical Society , 2007,
Abstract: Arapid, simple, and sensitive procedure based on modified solid phase extraction was developed for the pre-concentration and determination of trace amount of lead in water resources. Lead was reacted with ammonium pyrrolidinedithiocarbamate (APDC) to make a complex. The complex was then collected in a column packed with surfactant-coated alumina. The parameters affecting the collection efficiency and desorption rate of the lead complexes from the column were investigated and optimized. The collection efficiency of the lead complex on the adsorbent was excellent under the optimized conditions. The results obtained from the recovery test showed the capability and reliability of the method for the analysis of trace amounts of lead. The proposed pre-concentration procedure made it possible to apply conventional flame atomic absorption spectrometry (FAAS) for the sensitive determination of trace amounts of lead in water resources.
Solubilization of Hydrophobic Dyes in Surfactant Solutions  [PDF]
Ali Reza Tehrani-Bagha,Krister Holmberg
Materials , 2013, DOI: 10.3390/ma6020580
Abstract: In this paper, the use of surfactants for solubilization of hydrophobic organic dyes (mainly solvent and disperse dyes) has been reviewed. The effect of parameters such as the chemical structures of the surfactant and the dye, addition of salt and of polyelectrolytes, pH, and temperature on dye solubilization has been discussed. Surfactant self-assemble into micelles in aqueous solution and below the concentration where this occurs—the critical micelle concentration (CMC)—there is no solubilization. Above the CMC, the amount of solubilized dye increases linearly with the increase in surfactant concentration. It is demonstrated that different surfactants work best for different dyes. In general, nonionic surfactants have higher solubilization power than anionic and cationic surfactants. It is likely that the reason for the good performance of nonionic surfactants is that they allow dyes to be accommodated not only in the inner, hydrocarbon part of the micelle but also in the headgroup shell. It is demonstrated that the location of a dye in a surfactant micelle can be assessed from the absorption spectrum of the dye-containing micellar solution.
The Nature of Aqueous Solutions of a Cationic Calix[4]arene: A Comparative Study of Dye–Calixarene and Dye–Surfactant Interactions  [PDF]
N. O. Mchedlov-Petrossyan,L. N. Vilkova,N. A. Vodolazkaya,A. G. Yakubovskaya,R. V. Rodik,V. I. Boyko,V. I. Kalchenko
Sensors , 2006, DOI: 10.3390/s6080962
Abstract: Among different types of calixarenes, the water–soluble ones are of especial interestbecause of their possible applications in biochemical research. In order to elucidate the natureof aqueous solutions of a cationic amphiphilic calixarene, substituted tetrapropoxycalix[4]arene bearing hydrophilic choline groups at the upper rim, we studied vis–spectroscopically the influence of the above system on the acid–base behavior of threeindicator dyes, namely, 2,4-dinitrophenol, bromophenol blue, and N,N/-dioctadecylrhodamine,at constant ionic strength of 0.05 M, maintained with NaCl addition. Simultaneously,‘apparent’ ionization constants, Kaa , of the same dyes were determined in the presence ofcommon cationic surfactant micelles. Within the concentration range from 1.0×10–5 to 0.01 M,the aforementioned water–soluble calixarene displays effects similar to those of micelles ofcetyltrimethylammonium bromide (or chloride). The shifts of the absorption and emissionbands in the visible region, as well as the alterations of the Kaa values against the ‘aqueous’ones appeared to be very similar in aqueous solutions of both calix[4]arene and cationicsurfactant. A conclusion can be made about aggregation (or association), i.e., micelleformation of the cationic calix[4]arene under study.
Shear and longitudinal viscosity of non-ionic C12E8 aqueous solutions  [PDF]
Giovanni D'Arrigo,Giuseppe Briganti,Marco Maccarini
Physics , 2006,
Abstract: We present measurements of the steady shear viscosity, the longitudinal elastic modulus and the ultrasonic absorption in the one-phase isotropic liquid region of the nonionic surfactant C12E8 aqueous solutions. The overall results support the presence of two separated intervals of concentration corresponding to different structural properties. In the surfactant-rich region the temperature dependence of the steady shear viscosity follows an equation characteristic of glass-like systems. The ultrasonic absorption spectra show unambiguous evidence of viscoelastic behaviour described by a Cole-Cole relaxation formula. In the water-rich region the behaviour of the measured quantities are more complex and reflect the presence of dispersed aggregates whose size increases with temperature and concentration. An additional low frequency contribution is also observed, which is ascribed to the exchange of water molecules and/or surfactant monomers between the aggregates and the bulk solvent region.
Evolution of ZnS Nanoparticles via Facile CTAB Aqueous Micellar Solution Route: A Study on Controlling Parameters  [cached]
Mehta SK,Kumar Sanjay,Chaudhary Savita,Bhasin KK
Nanoscale Research Letters , 2008,
Abstract: Synthesis of semiconductor nanoparticles with new photophysical properties is an area of special interest. Here, we report synthesis of ZnS nanoparticles in aqueous micellar solution of Cetyltrimethylammonium bromide (CTAB). The size of ZnS nanodispersions in aqueous micellar solution has been calculated using UV-vis spectroscopy, XRD, SAXS, and TEM measurements. The nanoparticles are found to be polydispersed in the size range 6–15 nm. Surface passivation by surfactant molecules has been studied using FTIR and fluorescence spectroscopy. The nanoparticles have been better stabilized using CTAB concentration above 1 mM. Furthermore, room temperature absorption and fluorescence emission of powdered ZnS nanoparticles after redispersion in water have also been investigated and compared with that in aqueous micellar solution. Time-dependent absorption behavior reveals that the formation of ZnS nanoparticles depends on CTAB concentration and was complete within 25 min.
Aqueous Solubility Enhancement of Mirtazapine: Effect of Cosolvent and Surfactant  [PDF]
Kenneth E. Ezealisiji, Chika J. Mbah, Patience O. Osadebe
Pharmacology & Pharmacy (PP) , 2015, DOI: 10.4236/pp.2015.610049
Abstract: The poor aqueous solubility of drugs is a challenging problem faced by pharmaceutical scientists in drug formulation. Cosolvency and micellization techniques have been severally used to enhance the solubility of poorly aqueous soluble drugs. Mirtazapine, a tetracyclic antidepressant used for the treatment of moderate to severe depression and anxiety, has very poor aqueous solubility. The objective of the study was to investigate the effect of solubilizing agents (cosolvents and surfactants) on the aqueous solubility of mirtazapine while envisaging that any significant improvement in its aqueous solubility could contribute towards alleviating the withdrawal symptoms often associated with the drug. The solubility of mirtazapine was determined at room temperature in aqueous mixtures of cosolvents (propylene glycol and polyethylene glycol 400) and surfactants (polysorbate 20, polysorbate 80 and sodium lauryl sulfate). An exponential increase in mirtazapine solubility was observed when total drug solubility in water-cosolvent system was plotted against cosolvent fraction volume. Polyethylene glycol 400 gave larger solubilization capacity (σ) when compared to propylene glycol. With the surfactants, linear relationship between the total solubility of the drug in water-surfactant mixtures and surfactant concentration was noted. Sodium lauryl sulfate showed the largest solubilization power (k) when compared to the nonionic surfactants (polysorbate 20 and polysorbate 80 respectively). A linear relationship between standard free energy and partition coefficient was also observed. The result of the study shows that aqueous solubility of mirtazapine is significantly improved by cosolvency and micellization and therefore there exists the possibility of improving the withdrawal symptoms often experienced with the drug. It also suggests that large free energy is required for drugs with high partition coefficients to permeate the biological membrane.
Spectrophothometric Determination of Gatifloxacin through Complexation with Surfactant
International Journal of Pharma Sciences and Research , 2010,
Abstract: A simple, quick and sensitive U.V spectrometric method has been developed for the quantitative estimation of Gatifloxacin in bulk and pharmaceutical formulation. The method was based on the complexation with neutral surfactant, Tween-20 in aqueous phosphate buffer at PH 7.4 which showed an absorption maximum at 295nm and obeyed Beer’s law in the concentration range 2ìg/ml to 14ìg/ml which was based on the formulation of a U.V sensitive complex known as Europium. The limit of detection and quantification were calculated and relative standard deviation were less than 1.242. The results of analysis for the method has been validated statistically and by recovery studies the results obtained with the proposed method were in agreement with the labeled amounts.
Foam Stability Study of Dilute Aqueous Nonionic Fluorinated Surfactant Systems  [PDF]
S. C. Sharma,L. K. Shrestha,K. Aramaki
Journal of Nepal Chemical Society , 2007, DOI: 10.3126/jncs.v22i0.522
Abstract: Foaming properties of dilute aqueous nonionic fluorinated surfactants, perfluoroalkyl sulfonamide ethoxylate, C 8 F1 7 SO 2 N (C 3 H 7 )(CH 2 CH 2 O) n H (abbreviated as C 8 F 17 EO n, n = 10, 20) has been studied at 25°C. Both the surfactants produced a large volume of foams that are stable for several hours to a few days depending upon the surfactant concentration. The foam stability increases with increasing the surfactant concentration within the studied surfactant concentration limit. The C 8 F 17 EO 10 /water system shows higher foam stability than that of the C 8 F 17 EO 20 /water system. The foaming properties of the present systems show good correlation between dynamic surface tension properties and the dilatational surface elasticity. DOI: 10.3126/jncs.v22i0.522 Journal of Nepal Chemical Society Vol. 22, 2007 pp. 47-54
Influence of amino acids on the micellar behaviour of non-ionic surfactant in aqueous medium  [PDF]
B.S.Bhadane1 and T.J.Patil2*
International Journal of ChemTech Research , 2009,
Abstract: : The phenomenon of micellization in non-ionic surfactant Brij-58 (Bj-58) have been studied by measuring the cloud points (CP) of the pure surfactant and mixed system with Alanine (Ala) and Phenylalanine (PA). The CP of pure surfactant found to be decreased with increased [ Bj-58]. The CP of mixed system also shows same trends with increased [Ala] and [PA]. This is mainly due to increase in micelle concentration. The phase separation results from micelle-micelle interaction. Considering CP as a threshold temperature of the solubility, the thermodynamic parameters of clouding process ( G0cl , H0cl and S0cl ) have been evaluated using “Phase Separation Model”. The findings of the present work supports to made the probable evidence of macromolecule-surfactant interactions in aqueous medium.
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