Behavior of graphitized carbon blacks in the electrodegradation and sorption of chlorophenoxyacetic acids

Abstract

This paper compares the properties of two graphitized carbon blacks in the sorption and first stage of electrodegradation (dechlorination) of chlorophenoxyacetic acids and discusses the influence of surface area on the electrochemical behavior of these carbon materials. Two carbon blacks with ten-fold different surface areas (100 and 10 m2/g) were used as sorbents and electrode materials as received. Two chloroorganics with various numbers of Cl atoms in the molecule, 4-chlorophenoxyacetic acid and 2,4-dichlorophenoxyacetic acid, were adsorbed on the carbon samples from neutral aqueous electrolyte solutions containing low concentrations of adsorbate. Cyclovoltammetric studies of the graphitized carbon blacks were performed using powdered electrode techniques, and the drop in organics concentration during cyclization was measured using HPLC. For carbon black with a smaller surface area, the presence of faradaic reactions was not masked by capacitive currents, and well-shaped faradaic couple peaks characteristic of a quinine/hydroquinone-like adsorbed system were observed. This indicates that these materials are active in chloroorganics electrodegradation (by dechlorination). The extent of electrodegradation (a four-fold drop in organics concentration) observed for carbon black with a larger surface area indicates the dominant role of surface (porosity) development in these processes.