Determination of design parameters for the cloud point extraction of congo red and eosin dyes using TX-100

A systematic method is outlined to design cloud point extraction process. The aim is to calculate the concentration of non-ionic surfactant required for a desired extraction of dye at various operating conditions (feed dye concentration and temperature). In the course of design calculations, information about the following two characteristics of this system are required: (1) the solubilization isotherm of the dye in the surfactant solution at various operating temperatures and (2) quantification of the variation of the fractional coacervate phase volume with the feed surfactant, dye concentration and the operating temperature. In case of TX-100 and the dye system (congo red and eosin), a Langmuir type solubilization isotherm is fitted using the experimental data. Correlations are developed for the variation of isotherm parameters with temperature. A simple correlation of fractional coacervate phase volume with feed surfactant concentration is proposed in the form of ac(s)(b). From the experimental data, the variations of a and b with feed dye concentration and temperature are evaluated. Using the developed correlations and proposed design method, the concentration of feed surfactant required to achieve 1 ppm dye concentration in the dilute phase is calculated for the two dyes at typical operating temperatures and feed dye concentrations. The developed method will be of immense help for scale up of cloud point extraction process. (C) 2006 Elsevier B.V. All rights reserved.