Electrochemistry in media organized by surfactants: Detection and dehalogenation of organohalide pollutants

Date of Completion

January 1997

Keywords

Chemistry, Analytical

Degree

Ph.D.

Abstract

The aim of this doctoral research was the development of new, safe, effective methods for the electrochemical detection and degradation of organohalide pollutants. The major focus was on the use of cationic surfactants, particularly didodecyldimethylammonium bromide (DDAB), to influence the course of electrochemical reactions.^ Bicontinuous DDAB microemulsions were compared to organic solvents as media for the electrocatalytic reduction of benzal chloride and benzyl bromide. Microemulsions made from water, oil and DDAB behaved similar to organic solvent + proton donor for the mediated reactions. The reductive dehalogenations involve competition between radical and anion formation. Radical formation favors dimerization products, as were obtained cleanly using vitamin B$\sb{12}$ as catalyst. The results suggested that C-C bond formation can be controlled by changing the electrolysis conditions, especially potential. These and related compounds might be reductively dehalogenated in toxic wastes materials using microemulsions, which are less toxic and less expensive than organic solvents.^ A reversed-phase liquid chromatography with electrochemical detection was used for the separation and detection of haloacetic acids (HAAs). The detector contained a Nafion-DDAB coated PG electrode. The signal-to-noise ratio was decreased, the reduction potential was shifted to more positive values and the reduction current was increased for most of the acids, giving a higher sensitivity for Nafion-DDAB-PG compared to bare PG electrodes. The method is less sensitive than gas chromatography with electron capture detector but analysis of real water samples is possible. However, a better preconcentration method or more sensitive detection is required for routine analysis. ^

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