Reduktive Dehalogenierung von halogenorganischen Verbindungen an SiC und Entwicklung eines Analysengeraetes zur Bestimmung des Gehaltes an organisch gebundenem Halogen in Roh- und Trinkwasser Abschlussbericht

Given the toxicity of halogenated organic compounds (HOV) and their wide use and, hence, presence in the environment, especially in the hydrosphere, continuous monitoring of surface and phreatic waters as well as of the drinking water quality is needed. Recent commercial organic halide analyzer, using separation (adsorption on active carbon, extraction or purging), oxidative combustion and coulometric titration, are not suitable for on-line analysis. Aiming at a new analyzing equipment for a specific and quasi-continuous analysis of organic halides, we developed several modules for a suitable analytic system. Separation module for inorganic halides: Complete precipitation of the inorganic halide content of the samples was achieved at porous silver electrodes in a electrochemical flow-through cell. However, a quasi-continuous operation requires shorter residence times and therefore some modification of the cell design. Module for oxidative VUV-pretreatment (mineralization) of the organic halides: A miniaturized VUV (Vacuum ultraviolett)-reactor has been developed for the on-line mineralization of organic pollutants in aqueous systems with a organic carbon content of up to 20 ppm (DOC). From an analytical point of view, the advantage of using the VUV technique is the complete and exclusive conversion of the organic halogen to dissolved halide ions, while addition of reagents is not required. Electrochemcial detection modul for halide ions: At present, mercury can not substituted by silver as electrode material for the analysis of halide ions. Trace analysis requires electrochemical stripping methods on a hanging Hg-electrode (HMDE), which can be operated in a flow-through cell for enhanced sensitivity. SiC semiconductor electrodes have been tested for a reductive pretreatment module, based on the selective electrochemical dehalogenation of HOV's. UV-irradiation of single cristalline p-doped SiC-electrodes with epi-layers showed higher effiziencies than conventional electrodes. (orig.)SIGLEAvailable from TIB Hannover: F00B803+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman