scholarly journals FORMATION OF MICELLES OF CETYL TRIMETHYLAMMONIUM BROMIDE IN WATER-GLYCEROL SOLUTIONS

1998 ◽  
Vol 6 (7) ◽  
pp. 67-76
Author(s):  
Lavinel G. Ionescu ◽  
Sonia M. Hickel Probst ◽  
Elizabeth F. de Souza
Keyword(s):  
Free Energy ◽  
Aqueous Solutions ◽  
Entire Range ◽  
Cetyltrimethylammonium Bromide ◽  
Pure Water ◽  
Critical Micellar Concentration ◽  
Kcal Mole ◽  
Water Glycerol ◽  
Free Energy Of Micellization ◽  
Surface Tensiometry

The micellization of cetyltrimethylammonium bromide (CTAB) in glycerol and aqueous solutions of glycerol was studied by means of surface tensiometry. The critical micellar concentration (CMC) was determined at 25 °C and 40 Δ C, and thermodynamic parameters such as the free energy of micellization ΔG°mis, enthalpy ΔH and entropy ΔS of micellization were also measured At 40 °C, CTAB forms micelles in pure glycerol and in the entire range of water-glycerol solutions. For 25 °C, the CMC ranged from 9.2 x 10·4 Min pure water to 8.5 x 10·3M for solutions containing 90% glycerol by volume. The corresponding values obtained/or ΔG° were -4.14 and -2.82 kcal/mole; for ΔH° were -1.03 kcal/mole and -3.73 kcal/mole and for ΔS° were + 10.43 and -3.10 e. u. The addition of glycerol decreases the spontaneity of micelles formation of CTAB in water.

scholarly journals PHYSICAL CHEMICAL STUDIES OF THE AGGREGATION AND CATALYTIC PROPERTIES OF THE SURFACTANT CETYLDIMETHYLETHYLAMMONIUM BROMIDE (CDEAB)

1999 ◽  
Vol 7 (8) ◽  
pp. 105-114
Author(s):  
Lavinel G. Ionescu ◽  
Silvia Dani ◽  
Elizabeth Fatima de Souza
Keyword(s):  
Free Energy ◽  
Catalytic Properties ◽  
Activation Parameters ◽  
Critical Micellar Concentration ◽  
Physical Chemical ◽  
Chemical Studies ◽  
Diphenyl Phosphate ◽  
Free Energy Of Micellization ◽  
Surface Tensiometry ◽  
Hydrolysis Of

The micellization of cetyldimethylethylammonium bromide (CDEAB) in water was studied by means of surface tensiometry. The critical micellar concentration (CMC) was determined at 25°, 32°, and 40°C, and thermodynamic properties such as the free energy of micellization (∆G°mic), enthalpy (∆H°mic) and entropy (∆S°mic) of micellization were measured. The CMC at 25°C was 9.05 x 10-4 M and the corresponding values of the thermodynamic parameters were: ∆G°mic = -4.15 kcal/mol; ∆H°mic = -1.37 kcal/mol and ∆S°mic = + 9.33 e.u. Micelles of the surfactant CDEAB were good catalysts for the alkaline hydrolysis of p-nitrophenyl diphenyl phosphate (NPDPP) with a maximum catalytic factor of approximately 80, comparable to that of CTAB. Typical activation parameters measured for 0.005 M NaOH were: Ea = 9.0 kcal/mol; ∆H°≠ = 8.4 kcal/mol; ∆G°≠ = 19.2 kcal/mol and ∆S°≠ = -36.3 e.u. The kinetic results were also analyzed in terms of the pseudo-phase ion-exchange models (PPIE) and showed that the model is applicable and gave reasonable fits

Interaction of cationic surfactant with acid yellow dye in absence/presence of organic and inorganic additives: conductivity and dye solubilization methods

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Md. Ariful Haque ◽  
Shamim Mahbub ◽  
Mohammad Majibur Rahman ◽  
Md. Anamul Hoque ◽  
Dileep Kumar ◽  
...  
Keyword(s):  
Free Energy ◽  
Cationic Surfactant ◽  
Cetyltrimethylammonium Bromide ◽  
Micelle Formation ◽  
Aqueous System ◽  
Nacl Solution ◽  
Solubilization Capacity ◽  
Delta G ◽  
Free Energy Of Micellization ◽  
Dye Solubilization

Abstract In the present study, the conductometric and dye-solubilization techniques have been utilized to investigate the interaction between an anionic dye (acid yellow 23 [AY]) and a cationic surfactant (cetyltrimethylammonium bromide [CTAB]) in presence of organic (ethanol)/inorganic (NaCl) additives. From the conductometric method, two critical micelle concentrations (cmc) were found for AY + CTAB mixture in an aqueous system and the cmc values were found to undergo a change with the variation of AY concentrations. The cmc values of AY + CTAB systems were observed higher in the alcoholic medium, while the same was found to be lower in the NaCl solutions. The change in cmc of AY + CTAB systems shows an U-like curve with an increase of temperature. The negative free energy of micellization ( Δ G m o ${\Delta}{G}_{m}^{o}$ ) for the AY + CTAB systems has indicated a spontaneous micelle formation in all of the cases studied. The enthalpy ( Δ H m o ${\Delta}{H}_{m}^{o}$ ), as well as the entropy of micellization ( Δ S m o ${\Delta}{S}_{m}^{o}$ ) for the AY + CTAB systems, were assessed and discussed with proper reasoning. Additionally, the enthalpy-entropy compensation parameters were also investigated and illustrated. The solubility of AY and C D was observed to rise linearly with an increase in the concentration of CTAB/NaCl solution. The solubilization capacity (χ) of AY, the molar partition coefficient (K M) amongst the micellar and the aqueous phase, and free energy of solubilization ( Δ G S o ${\Delta}{G}_{S}^{o}$ ) were evaluated and discussed in detail. The former parameters undergo an increase with an increase of NaCl concentrations.

Viscosity of Dimethyl Sulfoxide + 1,4 Dimethylbenzene System

2008 ◽  
Vol 59 (1) ◽  
pp. 45-48
Author(s):  
Oana Ciocirlan ◽  
Olga Iulian
Keyword(s):  
Free Energy ◽  
Dimethyl Sulfoxide ◽  
Atmospheric Pressure ◽  
Entire Range ◽  
Polynomial Equation ◽  
Energy Of Activation ◽  
Excess Gibbs Free Energy ◽  
Experimental Measurements ◽  
Gibbs Energy Of Activation ◽  
Free Energy Of Activation

This paper reports the viscosities measurements for the binary system dimethyl sulfoxide + 1,4-dimethylbenzene over the entire range of mole fraction at 298.15, 303.15, 313.15 and 323.15 K and atmospheric pressure. The experimental viscosities were correlated with the equations of Grunberg-Nissan, Katti-Chaudhri, Hind, Soliman and McAllister; the adjustable binary parameters have been obtained. The excess Gibbs energy of activation of viscous flow (G*E) has been calculated from the experimental measurements and the results were fitted to Redlich-Kister polynomial equation. The obtained negative excess Gibbs free energy of activation and negative Grunberg-Nissan interaction parameter are discussed in structural and interactional terms.

Effect of cetyltrimethylammonium bromide on the electrochemiluminiscence and electrooxidation of luminol

1983 ◽  
Vol 48 (2) ◽  
pp. 477-483 ◽  
Author(s):  
Jan Lasovský ◽  
František Grambal
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Linear Sweep Voltammetry ◽  
Critical Micellar Concentration ◽  
Peak Height ◽  
Anodic Peak ◽  
Alkaline Solutions ◽  
Platinum Electrodes ◽  
Micellar Solutions ◽  
Linear Sweep ◽  
Low Concentrations

The electrooxidation of luminol in alkaline solutions in the presence of cetyltrimethylammonium bromide (I) was studied by linear sweep voltammetry on fixed and vibrating platinum electrodes. The presence of I in low concentrations (below the critical micellar concentration) brings about aggregation of the luminol, which is manifested by an increase in the anodic peak height and its shift towards lower potentials. In micellar solutions the peak height decreases owing to the slower diffusion of the bulkier micelles, the shift to lower potentials being preserved. The light-voltage curves correspond with the voltammetric curves, exhibiting identical shifts of the peak potentials in dependence on the concentration of the surfactant.

scholarly journals Effective replacement of cetyltrimethylammonium bromide (CTAB) by mercaptoalkanoic acids on gold nanorod (AuNR) surfaces in aqueous solutions

Nanoscale ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 658-668 ◽  
Author(s):  
Rafael del Caño ◽  
Jose M. Gisbert-González ◽  
Jose González-Rodríguez ◽  
Guadalupe Sánchez-Obrero ◽  
Rafael Madueño ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Gold Nanorods ◽  
Ligand Exchange ◽  
Cetyltrimethylammonium Bromide ◽  
Gold Nanorod ◽  
Experimental Conditions ◽  
Seed Mediated ◽  
The Stability

The highly packed cetyltrimethylammonium bromide bilayer on the surface of gold nanorods synthesized by the seed-mediated procedure hampers the complete ligand exchange under experimental conditions that preserves the stability of the dispersions.

Strongly hindered rotation in α,α,2,6-terrachlorotoluene. Stereospecific five-bond coupling. Hyperconjugative contributions to long-range sidechain-ring proton coupling constants

1968 ◽  
Vol 46 (12) ◽  
pp. 2187-2188 ◽  
Author(s):  
T. Schaefer ◽  
R. Schwenk ◽  
C. J. Macdonald ◽  
W. F. Reynolds
Keyword(s):  
Free Energy ◽  
Resonance Spectrum ◽  
Coupling Constants ◽  
Proton Resonance ◽  
Kcal Mole ◽  
Hindered Rotation ◽  
Ring Proton ◽  
Meta Position ◽  
Proton Coupling ◽  
Free Energy Of Activation

At −40 °C the C—H bond of the dichloromethyl group of α,α,2,6-tetrachlorotoluene lies in the plane of the ring. The proton resonance spectrum demonstrates a stereospecific five-bond coupling between the C—H proton and the ring proton in the meta position. The coupling to the para proton is essentially zero as expected from a hyperconjugative mechanism. The free energy of activation of rotation of the dichloromethyl group is about 15 kcal/mole at 25 °C.

scholarly journals Valorization of Spent Coffee by Caffeine Extraction Using Aqueous Solutions of Cholinium-Based Ionic Liquids

2021 ◽  
Vol 13 (13) ◽  
pp. 7509
Author(s):  
Ana M. Ferreira ◽  
Hugo M. D. Gomes ◽  
João A. P. Coutinho ◽  
Mara G. Freire
Keyword(s):  
Ionic Liquids ◽  
Aqueous Solutions ◽  
Pure Water ◽  
Waste Product ◽  
Weight Ratio ◽  
Extraction Yield ◽  
Operational Conditions ◽  
Coffee Grounds ◽  
Extractable Compounds ◽  
Nutraceutical Products

Spent coffee grounds (SCGs) are a waste product with no relevant commercial value. However, SCGs are rich in extractable compounds with biological activity. To add value to this coffee byproduct, water and aqueous solutions of cholinium-based ionic liquids (ILs) were studied to extract caffeine from SCGs. In general, all IL aqueous solutions lead to higher extraction efficiencies of caffeine than pure water, with aqueous solutions of cholinium bicarbonate being the most efficient. A factorial planning was applied to optimize operational conditions. Aqueous solutions of cholinium bicarbonate, at a temperature of 80 °C for 30 min of extraction, a biomass–solvent weight ratio of 0.05 and at an IL concentration of 1.5 M, made it possible to extract 3.29 wt% of caffeine (against 1.50 wt% obtained at the best conditions obtained with pure water). Furthermore, to improve the sustainability of the process, the same IL aqueous solution was consecutively applied to extract caffeine from six samples of fresh biomass, where an increase in the extraction yield from 3.29 to 13.10 wt% was achieved. Finally, the cholinium bicarbonate was converted to cholinium chloride by titration with hydrochloric acid envisioning the direct application of the IL-caffeine extract in food, cosmetic and nutraceutical products. The results obtained prove that aqueous solutions of cholinium-based ILs are improved solvents for the extraction of caffeine from SCGs, paving the way for their use in the valorization of other waste rich in high-value compounds.

scholarly journals Study on Adsorption of Cu and Ba from Aqueous Solutions Using Nanoparticles of Origanum (OR) and Lavandula (LV)

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Ghadah M. Al-Senani ◽  
Foziah F. Al-Fawzan
Keyword(s):  
Heavy Metals ◽  
Particle Size ◽  
Free Energy ◽  
Aqueous Solutions ◽  
Thermodynamic Parameters ◽  
Solution Ph ◽  
Environment Friendly ◽  
Removal Of Heavy Metals ◽  
Equilibrium Data ◽  
Langmuir And Freundlich Models

Wild herbs (Origanum (OR) and Lavandula (LV)) were used as environment-friendly adsorbents in this study. The adsorbents were used for adsorption of Cu and Ba from water. The adsorption of heavy metals onto OR and LV was dependent on particle size, dose, and solution pH. The diameter of adsorbent particles was less than 282.8 nm. The adsorption follows second-order kinetics. Langmuir and Freundlich models have been applied to describe the equilibrium data, and the thermodynamic parameters, the Gibbs free energy, ∆G°, enthalpy, ∆H°, and entropy, ∆S°, have been determined. The positive value of ∆H° suggests that the adsorption of heavy metals by the wild herbs is endothermic. The negative values of ∆G° at all the studied temperatures indicate that the adsorption is a spontaneous process. It can be concluded that OR and LV are promising adsorbents for the removal of heavy metals from aqueous solutions over a range of concentrations.

scholarly journals Conductivity Study of DTAB in Water and Ethanol-Water Mixture in the Presence and Absence of ZnSO4

2020 ◽  
Vol 17 (4) ◽  
pp. 1207
Author(s):  
Sangita Acharya ◽  
Tulasi Niraula ◽  
Ajaya Bhattarai
Keyword(s):  
Free Energy ◽  
Critical Micelle Concentration ◽  
Volume Fraction ◽  
Standard Free Energy ◽  
Water Mixture ◽  
Dodecyltrimethylammonium Bromide ◽  
Degree Of Dissociation ◽  
Ethanol Content ◽  
Presence And Absence ◽  
Free Energy Of Micellization

The physicochemical behaviour of dodecyltrimethylammonium bromide (DTAB) in water and ethanol-water mixture in the presence and absence of ZnSO4 were studied by measuring the conductivity at 298.15 K. The pre-micellar (S1) and post-micellar slopes (S2) were obtained and calculated the degree of dissociation (α) and the critical micelle concentration (cmc). With an increase in ethanol content, the cmc and α of DTAB increased whereas, in the presence of ZnSO4, the cmc and α decreased. By using cmc and α, thermodynamic properties as the standard free energy of micellization ( ) were evaluated. With an increase in ethanol content, the negative values of  are decreased indicating less spontaneous in the micellization which makes micellization less favourable. The correlation of the pre-micellar and post-micellar slopes with the volume fraction of ethanol were discussed. DTAB micellization was tested in contexts of specific solvent parameters and solvophobic parameter.

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