Talanta ELSEVIER Talanta 43 (1996) 1 I-20 Potentiometric study of the protonation and distribution equilibria of 2-chlorophenol in N&l medium at 25°C. Construction of a thermodynamic model Ainoa Rios, Gorka Arana*, Nestor Etxebarria, Luis A. Fernhdez Kimika Analitikoarrn Saila, Euskal Herriko Unihrrfsitutea (UPV/EHU). P.K. 644, E-48080 Bilbao, Basque Cnunrry, Spain Received 14 April 1995: revised I4 July 1995: accepted I7 July 1995 Abstract The potentiometric determination of the protonation constant of 2-chlorophenol in NaCl media at different ionic strengths and its distribution coefficient between these media and two organic solvents at 25°C are presented. An automated potentiometric system was used, and the determination of the constants was carried out using both graphical and numerical methods. A thermodynamic model using the modified Bromley methodology has been constructed for the prediction of protonation constants and distribution coefficients in NaCl media. The relevance of this study to the development of supported liquid membrane recovery systems is discussed. Keywords: Protonation equilibria; Distribution equilibria; Potentiometry: Thermodynamic model; 2-Chlorophenol 1. Introduction 2-Chlorophenol is a priority pollutant phenol and, like many other phenols, may be found in the wastewaters of some manufacturing industries, such as coke production, paper and pulp process- ing, oil refining, coal gas liquefaction, etc. Some of the consequencesof the uncontrolled disposal of this kind of compound are toxicity to water-life, increase in chemical and biological oxygen de- mand, and bad taste and smell in water [l-4]. As the toxicity of chlorophenols is high they are used as disinfectants; however, some of them * Corresponding author are suspected of being carcinogenic, and a con- centration of phenols of higher than 2 mg drn-’ is dangerous to water-life. For the reasons, chlorophenols containing wastewaters have to be controlled [4]. By improving analytical methods, these pollutants have been detected and reported in industrial and city wastes. There are several methods for treating phenolic wastes and their choice depends on the concentra- tion levels of the phenols. For high concentrations, recovery and reuse or disposal by incineration is possible. Intermediate concentrations can be treated biologically or by adsorption onto active surfaces. In more diluted wastes chemical oxida- tion can be used. Apart from these methods, 0039-9140/96i$l5.00 c 1996 Elsevier Science B.V. All rights reserved SSDI 0039-9140(95)01696-l