Determination of solubilization of phenol at coacervate phase of cloud point extraction

doi:10.1016/S0927-7757(02)00560-5

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Volume 216, Issues 1–3, 15 April 2003, Pages 207-214

https://doi.org/10.1016/S0927-7757(02)00560-5 Get rights and content

Abstract

When the temperature of a nonionic surfactant solution is over the cloud point, the solution separates into two phases, a dilute phase and a coacervate phase. The solute that originally exists in the solution will unevenly partition into those two phases, which is known as cloud point extraction (CPE). For determination of the solubilization of phenol in micelles of surfactant solution, the concentration of free solute unassociated to micelles in the dilute phase was determined. It was a constant at certain temperature. The result was re-verified by titration experiments. Therefore, the solubilization in the coacervate phase can be determined experimentally. The result was compared with the solubilizaton in micelles, which showed that the solublization in the coacervate phase was different from that in micelles. This can be attributed to different structures of micelles in dilute phase and in coacervate phase.

Introduction

As the temperature of an aqueous nonionic surfactant solution is increased or some additives are added, the solution turns cloudy and phase separation occurs. The solution may separate into a surfactant-rich phase (coacervate phase) and a dilute phase. A solute that originally exists will unevenly partition into those two phases. The temperature at which phase separation occurs is known as cloud point. This technique is known as cloud point extraction (CPE). Recently great attention has been attracted for its great potential in separation of biological material, removal of toxic solutes from polluted water, etc. [1], [2], [3]. Despite numerous reports of practical application of CPE, its mechanism is still unclear. It is needed to develop theories to describe and predict the interactions between surfactant and target solutes, such information would lead to the design of more superior. CPE systems and would increase the use of this technique [3]. Most of reports [4] that manage to predict the solution of cloud point system are based on the general linear solvation energy relationship. To understand the interaction of solute and surfactant in coacervate phase, determination of the concentrations of free solute and associated solute with surfactant is important. CPE system is strongly affected by solute. The solute can alter the cloud point of a surfactant solution system, so that alters the partition of surfactant in two phases [5]. The interaction between solute and micelle is very complicated. The solubilization equilibrium constant should vary with the change of solute concentration [6]. It is difficult to determine the concentration of free solute that is un-associated to micelle. Sakulwongyai et al. determined the coacervate solubilization equilibrium constant with so dilute solution that the influence of solute on the cloud point system can be neglected [7].

In this study, solubilization equilibrium constant of phenol in surfactant micelles, solute concentration and surfactant concentration in dilute phase were determined. Under some assumptions, the concentration of solute existing freely from surfactant was detected, and the solubilization in coacervate phase was determined. The solubilizations in coacervate phase can be compared with that in surfactant solution. The interaction mechanism between solute and surfactant in coacervate phase was discussed.

Section snippets

Materials

Surfactant Brij-35 (purchased from Fluka) was used. The commercial surfactant is a mixture of polydisperse polyoxyethylene glycol monoethers. It is usually abbreviated as C₁₂E₂₃ [1] with 12 indicating the number of carbons in alkyl chain and 23 being the number of ethylene oxide units in the hydrophilic-moiety. All other materials were analysis grade.

Solubilization of phenol in micelles

A series of solutions were prepared with a certain concentration of phenol and increasing concentrations of Brij-35. The absorbance of these

Theory

In aqueous surfactant solution, solubilization, which is the ability to dissolve solute in micelles, is an important parameter of surfactant. It was usually described by a micellar solubilization equilibrium constant (K), which defined by: $K= X C_{w}$ where C_w is free solute concentration, and X is mole fraction of solute in micelles defined by: $X= C_{m} C_{m} +C_{s}$ where C_m is the concentration of solute associated to micelles, and C_s is the concentration of surfactant forming micelles. As the CMC is much lower

Solubilization

The absorbance of phenol solutions as a function of Brij-35 concentration is shown in Fig. 2. In absence of surfactant, the absorbance (A₀) is also shown in Fig. 2. However, when surfactant is present, the expected absorbance increases drastically until it reaches a constant value corresponding to maximum absorbance A_∞. Fig. 3 showed a plot of 1/(A−A₀) versus 1/C_s. According to Eq. (8), A_∞ can be determined as 0.72. Then optimizing the data of Fig. 2 with Eq. (7), the values of q_m and k can be

References (16)

C.L. Liu et al.
Biotechnol. Bioeng.
(1996)
L. Sepulveda
J. Colloid Interf. Sci.
(1974)
K. Kandori et al.
J. Colloid Interf. Sci.
(1989)
J.H. Kim et al.
Colloids Surf. A
(1999)
W.L. Hinze et al.
Crit. Rev. Anal. Chem.
(1993)
F.H. Quina et al.
Ind. Eng. Chem. Res.
(1999)
K. Materna et al.
Environ. Sci. Technol.
(2001)
J. Sjoblom et al.

There are more references available in the full text version of this article.

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Determination of solubilization of phenol at coacervate phase of cloud point extraction

Abstract

Introduction

Section snippets

Materials

Solubilization of phenol in micelles

Theory

Solubilization

Biotechnol. Bioeng.

J. Colloid Interf. Sci.

J. Colloid Interf. Sci.

Colloids Surf. A

Crit. Rev. Anal. Chem.

Ind. Eng. Chem. Res.

Environ. Sci. Technol.