Reduction of Nitro Aromatic Compounds by Zero-Valent Iron Metal

The properties of iron metal that facilitate the remediation of chlorinated solvents may also lead to the reduction of groundwater contaminants such as nitro aromatic compounds (NACs). This study investigates the reduction of nitrobenzene to aniline under anaerobic conditions using zero-valent iron. The research involved examining the reduction rates and product formation to understand the kinetics and mechanisms involved. The results revealed that nitrobenzene is reduced to aniline with nitrosobenzene as an intermediate, while coupling products like azobenzene and azoxybenzene were not detected. First-order rate constants for nitrobenzene and nitrosobenzene were found to be similar, with aniline formation occurring at a slower pace. The nitro reduction rate increased linearly with the concentration of iron surface area, suggesting mass transfer to the metal surface as a controlling factor. Meanwhile, the presence of dissolved carbonate negatively impacted the reduction rate by promoting the precipitation of siderite on the metal. These findings underscore the significance of understanding the interactions between iron and various groundwater contaminants to enhance remediation strategies.