Development of a Novel Internal Electrolysis System by Iron Connected with Carbon: Treatment of Nitroaromatic Compounds and Case of Engineering Application

The mixture of scrap iron and particle carbon, termed internal electrolysis, has been used in the pretreatment of industrial wastewater to improve the biodegradability. However, the clogging of fillings reduces treatment efficiency, and filling replacement is inconvenient in engineering application. This study developed a novel internal electrolysis system, in which iron and carbon were separately placed and connected with a wire. Results showed that the removal of paranitrophenol by iron was significantly enhanced by the connection of carbon. The removal by iron connected with carbon was approximately equivalent to that by iron contacted with carbon. The removal of nitrobenzene and the production of aniline proved the reduction in nitro to amino group. The sites for contaminant removal were found to be on iron surface rather than on carbon surface. The connection of carbon to iron facilitated the corrosion of iron and led to the formation of more Fe oxyhydroxide and the release of more electrons from iron, both of which attributed to contaminant removal. The engineering application using the novel internal electrolysis demonstrated an average chemical oxygen demand removal of 60% and a significant increase in wastewater biodegradability. This novel internal electrolysis system was preliminarily proved feasible and convenient.