Gibbs Energies Of Partition Research Articles

Self-organised surfactant assemblies as nanostructured dye carriers: a mixed micellar comparative approach for enhanced dye solubilisation

ABSTRACT The reported work is focused on the solubility of Rhodamine B (cationic dye), as an important methodology to investigate the extent of incorporation or penetration of dye inside the micelles spectroscopically, so the solubilised dye can be filtered via Micellar-enhanced ultrafiltration process to keep our environment safe from toxic effects of industrial effluent. Solutions were prepared by using micellar media of anionic surfactants i.e. Sodium dodecyl sulphate (SDS), Sodium Oleate (SO) as well as mixed micellar media of said anionics with non-ionic surfactant i.e. Triton X-100 (TX-100). The extent of solubilisation has been, quantitatively, calculated using data of differential spectroscopy, in terms of partition coefficient Kx and Gibbs energy of partition, ∆Gp. It has been observed that mixed micellar media has better solubilisation capacity than micellar solution of individual surfactants. A better micellar solubilisation and ultimately the high Gibbs energy of partition, ∆Gp with SO/TX-100 system i.e. −40.89 as compared to SDS/TX-100 system (−37.03) has been observed due to the presence of long carbon chain in SO.

Solubilization of direct dyes in single and mixed surfactant system: A comparative study

Interaction of direct dyes (Direct Orange 26 and Direct Red 9) has been investigated via spectroscopic analysis in single cationic (cetyltrimethylammonium bromide) and cationic-nonionic mixed surfactant media. The solubilization capabilities of surfactants solutions have been assessed in terms of the partition coefficient (Kx) and binding constant (Kb). Critical micelle concentration (CMC) of the surfactant, electrostatic interactions, hydrophobic associations, and polarity of the medium plays important role in the said process. Significant enhancement in the solubility of both dyes was observed on the addition of non-ionic surfactants (Triton X-100 and Tween-20) in the CTAB solution. Solubility was found to be directly related to the extent of mixed micellization. The negative values of the Gibbs energy of binding (ΔGb) and Gibbs energy of partition (ΔGp) are the predictors to prove the feasibility and spontaneity of the process. The results, herein, suggest that the use of mixed micellar media for solubilization of direct dyes is advantageous over that of a single surfactant.

The application of cationic-nonionic mixed micellar media for enhanced solubilization of Direct Brown 2 dye

The present study reports the enhanced solubilizing power of mixed micellar media in comparison to single micellar media. The solubilization of anionic direct dye, Direct Brown 2 (DB-2) has been investigated in micellar media of cationic surfactants; cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC) and in mixed micellar media of each with nonionic surfactant Triton X-100 (TX-100) using UV–visible spectroscopy and conductometry. The UV–visible spectroscopy has been used to evaluate the degree of solubilization in terms of binding constant, Kb, Gibbs energy of binding, ΔGb, partition coefficient, Kx, and Gibbs energy of partition, ΔGp. Furthermore, electrical conductivity data, taken at different temperatures, has been employed to find out critical micelle concentration (CMC) and different thermodynamic parameters like enthalpy, ΔHm, entropy, ΔSm and Gibbs energy of micellization, ΔGm of reported surfactants in presence of dye. Results reveal spontaneous nature solubilization and binding of dye in both micellar and mixed micellar solutions of surfactants. The micellar system of CTAB as well as mixed micellar solutions of CTAB/TX-100 are recommended to be used to achieve higher degree of solubilization.

Solubilization of reactive dyes by mixed micellar system: Synergistic effect of nonionic surfactant on solubilizing power of cationic surfactant

In this manuscript solubilization of reactive dyes i.e. Reactive red 195 and reactive blue 221, by simple and mixed micellar solution, is being reported using UV/visible spectroscopy and electrical conductivity. UV/visible spectroscopy has been used to have quantitative measurement of degree of solubilization in term of partition coefficient (Kx) and Gibbs energy of partition (ΔGp) while electrical conductivity has been employed to detect critical micelle concentration of surfactants and, accordingly, to calculate thermodynamic parameters. It has been concluded that solubilization is exothermic, spontaneous and enthalpy driven process. The partitioning and binding of RB-195 has been found to be more favorable and spontaneous than that of RB-221. The results clearly indicate that the inclusion of TX-100 in micellar media of CTAB has significantly enhanced its solubilizing power.

Relationship between the extracellular polymeric substances and surface characteristics of Rhodopseudomonas acidophila

The relationship between the extracellular polymeric substances (EPS) and surface characteristics of Rhodopseudomonas acidophila in its different growth phases was established. The equilibrium constant of partition (K par) and the Gibbs energies of partition (DeltaG par) between hexadecane and aqueous phases were also calculated according to the microbial adhesion to hexadecane (MATH) testing. The EPS content decreased with cultivation time at the logarithmic phase, but kept almost unchanged around 22.9 mg g(-1) dry cell at the stationary phase. The EPS production of R. acidophila had a significant effect on its surface characteristics. The relative hydrophobicity and the K par values of R. acidophila before EPS extraction were both lower than those after extraction. Both EPS content and ratio of proteins to carbohydrates had a negative effect on the water contact angle of the bacterium, but had a positive influence on the bacterial surface free energy and its polar component. On the other hand, the EPS were not related with MATH% or the Gibbs energy of partition between hexadecane and aqueous phase.