MODELING AND EXPERIMENTAL STUDY OF ELECTROCHEMICAL OXIDATION OF ORGANICS ON BORON-DOPED DIAMOND ANODE

Abstract

Electrochemical oxidation on Boron-Doped Diamond (BDD) electrodes is reportedly more effective than conventional chemical or electrochemical oxidation methods for the removal of recalcitrant organic contaminants from aqueous effluents This work investigated the electrochemical oxidation of acetic acid and nuclear process effluents containing representative recalcitrant chlorinated and nitrogenated organics on a BDD anode using a DiaCell® apparatus The removal of organic carbon mostly depended on applied current density, mass transfer effects, and the properties of organic compounds The total organic carbon (TOC) concentrations in the solutions were reduced to as low as 05 g·m-3 , achieving mineralization of up to 99 % of organic carbon Dissolved oxygen significantly contributed to the removal of organic carbon at low concentrations In particular, the BDD anodic oxidation system was capable of destroying organic carbon representing a mixture of mineral oil, and carboxylic, aromatic, chlorinated, and nitrogenated organics Complementing the experimental work, an electrochemical oxidation model was developed for simulating the reaction process on the BDD anode and for improving simpler literature-reported models This model considered effects of fluid dynamic and operating parameters, and introduced a retardation factor, gk that addresses the effect of charges on the organic moieties on mass transfer, and subsequently on the anodic oxidation rate An expression for the retardation factor was formulated in terms of the ionization fraction of an organic compound, the charges on organic ions, the number of electrons transferred per organic carbon atom oxidized, and the effect of heteroatoms such as oxygen, nitrogen, and chlorine Model predictions were verified with the experimental data obtained by varying pH, temperature, current density, volumetric flow, and dissolved oxygen This model can be further exploited for optimization and design of improved BDD anodic oxidation processes (author)