• Journal of the Korean Applied Science and Technology
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• v.18 no.4
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• pp.325-331
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• 2001

The critical micelle concentration (CMC) at which micelles start to form from a surfactant solution is usually measured in terms of conventional concentration units. However, the thermodynamic potentials are expressed in terms of mole fraction $X_{CMC}$ and $X_{CMC}$ cannot be directly measured experimentally. The Gibbs free energy, ${\Delta}G^{\ast}_{mic}$, in particular is related to $X_{CMC}$ through ${\Delta}G^{\ast}_{mic}$ = $RTlnX_{CMC}$. When it comes to CMC, the molar CMC, $C_{CMC}$, differs only by the proportionality $C^{-1}_{w}$ with $C_{w}$ being the molarity of water. Hence, $C_{CMC}$ is found to be a proper representation of CMC. However, in calculation of ${\Delta}G^{\ast}_{mic}$ and other thermodynamic potentials from the CMC, $X_{CMC}$ or $C_{CMC}/C_{w}$ should be used.

• Membrane Journal
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• v.18 no.1
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• pp.7-25
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• 2008

Sodium dodecyl sulfate, which was anionic surfactant, at a concentration higher than its critical micellar concentration was added to calcium solution for forming micelles. Then aggregates were formed by adsorption or binding of calcium ions on the surface of micelles, and gathering between them, and then rejected by two kinds of ceramic membranes to remove calcium ions. As result, rejection rates of calcium were higher than 99.98%. And in our experimental range the higher TMP trended to increase the resistance of membrane fouling ($R_f$), total permeate volume ($V_T$), dimensionless permeate flux ($J/J_o$) and permeate flux (J) because TMP was driving force. And we investigated effects of $N_2$-back-flushing time and filtration time, that was back-flushing period, during periodic $N_2$-back-flushing on ceramic membranes. As result, optimal BTs for NCMT-623l ($0.07{\mu}m$ pore size) and NCMT-7231 membrane ($0.10{\mu}m$) were 10 sec and 15 sec, respectively. Also, optimal FT was 5 min for both membranes, and the frequent $N_2$-back-flushing could decrease membrane fouling effectively. Then, the optimal conditions resulting from our experiments for synthetic calcium solution were applied to groundwater using as washing process of soymilk package. As result, rejection rates of calcium were higher than 99.98%.

• Journal of the Korean Applied Science and Technology
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• v.37 no.3
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• pp.438-447
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• 2020

The critical micelle concentration (CMC) values of the mixed surfactant systems and the solubilization conatant (K_s) values of 4-ethylaniline in those solutions were measured and analyzed by the UV-Vis method. As a result, the mixed surfactant systems of TTAB/LSB and TTAB/TX-100 did not deviate significantly from ideal mixed micellization. However, the mixed systems of SDS/LSB and SDS/TX-100 showed great negative deviations from ideal mixed model. These differences showed that the intensity of the interaction between two components in the mixed micelle was different for each mixed system and that these differences greatly influenced the solubilization of 4-ethylaniline by a mixed surfactant system. Among pure surfactants, an anionic surfactant such as SDS showed a greater K_s value than other ionic surfactants, and the K_s value by each surfactant system decreased in the order of SDS≫TTAB≧LSB>TX-100. In addition, the K_s values of all the mixed surfactant systems were higher than those of the pure surfactants constituting the mixed systems.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.4
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• pp.419-429
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• 2014

Recent studies have been reported the presence of Endocrine Disrupting Compounds, Pharmaceuticals and Personal Care Products (EDC/PPCPs) in surface and wastewater, which could potentially affect to the complicate behavior in coupled presence of nano-colloid particles and surfactants (adsorption, dispersion, and partitioning). In this study, the adsorption of EDC/PPCPs by Single Walled Carbon Nanotubes (SWNTs) as a representative of nano-particles in cationic surfactant solutions were investigated. Hydrophobic interactions (${\pi}-{\pi}$ Electron Donor-Acceptor) have been reported as a potential adsorption mechanisms for EDC/PPCPs onto SWNTs. Generally, the adsorptive capacity of the relatively hydrophobic EDC/PPCPs onto SWNTs decreased in the presence of cationic surfactant (Cetyltrimethyl Ammonium Bromide, CTAB). This study revealed that the competitive adsorption occurred between CTAB cations and EDC/PPCPs by occupying the available SWNT surface (CTAB adsorption onto SWNTs shows five-regime and maximum adsorption capacity of 370.4 mg/g by applying the BET isotherm). The adsorption capacity of $17{\alpha}$-ethinyl estradiol (EE2) on SWNT showed the decrease of 48% in the presence of CTAB. However, the adsorbed naproxen (NAP) surely increased by forming hemimicelles and resulted in a favorable media formation for NAP partition to increase SWNTs adsorption capacity. The adsorbed NAP increased from 24 to 82.9 mg/g after the interaction of CTAB with NAP. The competitive adsorption for EDC/PPCPs onto SWNTs is likely to be a key factor in the presence of cationic surfactant, however, NAP adsorption showed a slight competition through $CH_3-CH_3$ interaction by forming hemimicelles on SWNT surface.

• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.379-386
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• 2015

The solubilization of p-chlorobenzoic acid in aqueous solutions of pure cationic, nonionic, amphoteric, and their mixed surfactant systems have been measured by the UV-Vis spectrophotometric method. The effects of hydrophobic tail-group with different chain length and the hydrophilic head-group on the solubilization of p-chlorobenzoic acid have been studied and also thermodynamic parameters have been calculated from the dependence of K_s values on the temperature. The results show that the values of ΔG^o for the solubilization by all surfactant systems are negative and the values of ΔH^o and ΔS^o are all positive.

• Journal of the Korean Chemical Society
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• v.54 no.4
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• pp.374-379
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• 2010

The interaction of dichlorophenol isomers with the micellar system of TTAB (tetradecyltrimethylammonium bromide) was studied by the UV/Vis spectrophotometric method. The solubilization constants ($K_s$) of dichlorophenol isomers into the micellar system have been measured with the change of temperature and the various thermodynamic parameters have been calculated and analyzed from these changes. The results show that the values of ${\Delta}G^{\circ}_s$ and ${\Delta}H^{\circ}_s$ are all negative within the measured temperature range. The effects of additives (n-butanol and NaCl) on the solubilization of dichlorophenol isomers have been also measured. There was a great change on the values of $K_s$ and CMC simultaneously with these additives. From these changes we can postulate the solubilization sites of each isomers in the micellar system of TTAB.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.473-478
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• 2011

The interaction of para-halogenated benzoic acid isomers with the micellar system of tetradecyltrimethylammonium bromide was studied by the UV/Vis spectrophotometric method. The solubilization constants ($K_s$) of benzoic acid isomers into the micellar system of TTAB and the critical micelle concentration (CMC) of TTAB have been measured with the change of temperature. Various thermodynamic parameters have been calculated and analyzed from those measurement. The results show that the values of ${\Delta}G^{\circ}{_s}$ for the solubilization of all isomers are negative and the values of ${\Delta}H^{\circ}{_s}$ and ${\Delta}S^{\circ}{_s}$ are all positive within the measured temperature range. The effects of additives (n-butanol and NaCl) on the solubilization of benzoic acid isomers have been also measured. There was a great decrease on the values of $K_s$ and CMC simultaneously with these additives. From these changes we can postulate that the solubilization sites of each isomers in the TTAB micellar system are the surface or the palisade region of the micelle.

• Analytical Science and Technology
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• v.20 no.6
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• pp.483-487
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• 2007

Electrochemistry of 1.0 mM bis(1,10-phenanthroline)copper(II) $(Cu(ph){_2}^{2+})$ in 100 mM NaCl solution including 27 mM $MgCl_2$ with and without sodium dodecyl sulfate (SDS) is studied. In the presence of SDS, $E_{pa}$ and $E_{1/2}$ of $Cu(ph){_2}^{2+}$ by adding $Mg^{2+}$ shifts to a positive direction compared to the SDS free. The intersection of two lines on ${\Delta}E_p$ vs -log[SDS] plot is determined as a critical micelle concentration (CMC). When $Mg^{2+}$ is added, it seems that the double layer became more compact. And the formation of micelles is retarded.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.834-841
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• 2005

Polyethylene glycol esters (PEG-esters) were synthesized by condensation reaction of dicarboxylic acid such as adipic acid and sebacic acid and several PEGs. The PEG-esters were analyzed by FT-IR, $^1H-NMR$ and HPLC for structure analysis, and by GPC for molecular weight. Through the analysis of surface tension, critical micelle concentration (CMC), aluminum contact angle of water solution containing the PEG-ester, the synthetic PEG-esters are proven to exhibit surfactant properties. The surface tension ranged from 45 to 50 dyn/cm depended on the concentration and structures of the PEG-esters. The surface tension of PEG-esters with sebacic acid moiety and short polyoxyethylene unit resulted in lower value than that of PEG-ester with adipic acid moiety and long polyoxyethylene unit. The CMC of water solution containing 2.5 wt% PEG-ester with sebacic acid moiety estimated at $0.9{\times}10^{-5}{\sim}5.3{\times}10^{-3}mol/L$ depended on the structures of PEG-esters. The CMC of PEG-esters with long polyoxyethlene unit showed a higher value than that of PEG-esters with short polyoxyethylene unit. Meanwhile, the CMC of PEG-esters with adipic acid moiety was not distinct due to their high hydrophilic character. As the results of contact angle and cutting time aginst aluminum, the contact angle ranged from $45^{\circ}$ to $53^{\circ}$ depended on the concentration of PEG-esters. The cutting time of aluminum showed the shortest value at CMC, but the longest value above CMC. This fact indicates that the CMC of PEG-esters is a very important factor in drilling aluminum.

• KSBB Journal
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• v.17 no.3
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• pp.302-306
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• 2002

The chemical analysis and surface chemical properties of biosurfactant formed by Rhodococcus sp. strain IGTS8, which is widely used in biodesulfurization process, in hexadecane/water mixture have been studied. For the chemical analysis, TLC technique was employed. The surface tension, CMC, and emulsion stability of biosurfactant solution were also investigated. The major components of biosurfactant formed by Rhodococcus sp. strain IGTS8 were glucose mycolate and trehalose monomycolate. The CMC of aqueous biosurfactant solution was 0.1 ~0.15 g/100 mL of Water at pH 6.0-6.5 and pH 10~10.5. But the demulsification was faster at pH 10 than at pH 6.3.