Electrochemical Decolorization Of Reactive Blue 19 On ACF

Dye wastewater is characterized by complicated components, strong color, highly fluctuating pH, high COD, TOC concentration and suspend solids, low biodegradability, and widely varied quality and quantity, so it has been rather difficult to be treated. As an eco-friendly technology, electrochemical method added little or no additional chemicals without secondary pollutants for wastewater treatment. In recent years, there has been increasing interest in the use of electrochemical methods for the treatment of dye wastewater.Most study on dye wastewater treatment with electrochemical method was conducted with cell voltage or current constantly controlled and the parameters of voltage, current density, wastewater conductivity, pH, current efficiency and energy consumption were evaluated. However, there are few reports on the relationship between the decolorization and the potential and current density. It is known that potential and current density are the fundamental factors for the electrochemical process. So it is necessary and important to evaluate the effect of potential and current density on the decolorization of dye wastewater. Besides, a great number of experiments were performed in a single compartment electrolytic cell. As a result, it is difficult to make sure the pure contribution of electrooxidation and electroreduction for the decolorization of dye wastewater because of the cross- interference of the anode and cathode.The objective of this study is to investigate the effect of the potential and current density on the decolorization of Reactive Blue 19, one of anthraquinone dyes. Activated carbon fiber (ACF) was used as anode or cathode under potentiostatic and galvanostatic model, respectively. The electrolytic cell was designed as a two-compartment cell separated by cation selective membrane. The linear sweep voltammograms of ACF in dye solution were measured; the effects of potential and current density on the decolorization kinetics, color, total organic carbon (TOC) and chemical oxygen demand (COD) removal ratio were investigated, and the energy consumptions of experimental processes were calculated, too.The results obtained were shown as: (1) the onset reduction potential and the onset oxidation potential of Reactive Blue 19 are about -0.7V and 0.5V respectively, and the optimal oxidation potential is 1.1V.(2) In the range of -0.6V ~ 0.4V and -0.875 ~0.0625mA · cm-2, the decolorization results from the adsorption of Reactive Blue 19 on ACF and the adsorption behavior is insignificantly affected by polarization; (3) In the range of -0.7V~--1.5V and -0.938~-1.12mA · cm-2, the electroreduction plays an important role in the decolorization. Furthermore, the decoloring process follows pseudo-first order kinetics; (4) In the range of 0.5V~ 1.6V and 0.125~0.5mA · cm-2, the electrooxidation results in the decolorization and the decoloring process also follows pseudo-first order kinetics; (5) Energy consumptions of electrooxidation and electroreduction of the dye on ACF are lower than that of adsorption, and energy consumptions of the electrooxidation are higher than that of the electroreduction.