Fered-Fenton treatment of car wash wastewater using carbon felt cathode: Carbon dissolution and cathodic corrosion

Abstract

The Fered-Fenton (FF) process has the potential to oxidize organic pollutants in car wash wastewater (CWW) nonselectively. As a high-quality gas diffusion cathode, carbon felt (CF) is perhaps one of the most widely used carbon cathodes in FF process. Although thermodynamic instability has been found, there are no clear reports on the negative effects on organics evolution and possible ways of cathodic corrosion of CF. This study first report the carbon dissolution and cathodic corrosion of CF cathode and revealed a possible corrosion pathway. An FF system using carbon felt cathode was constructed that can effectively remove chemical oxygen demand (COD), total organic carbon (TOC) and linear alkylbenzene sulfonate (LAS) of CWW in 120 min. During electrolysis, carbon dissolution of the CF cathode leads to the accumulation of organic carbon. Toxic organic intermediates were detected and negatively affected biodegradability and acute cytotoxicity. The main cause of cathodic corrosion was the electroreduction of carbon species on CF. Hydrogen peroxide indirectly promoted the corrosion process by consuming reducing carbon species. Optimizing the appropriate electrolysis time (such as 60 min) or using a more stable graphite felt (GF) cathode as an alternative is the recommended strategy. This work provides new insight and technical support for the FF process with CF cathode.