Enhanced reductive transformation of 2,4-dinitroanisole in a anaerobic system: the key role of zero valent iron

Abstract

Accelerated reduction of typical multi-substituted nitroaromatic compounds (NACs), i.e., 2,4-dinitroanisole (DNAN), was achieved in an anaerobic system coupled with zero valent iron (ZVI), with the underlying role of ZVI in this process elucidated. Both removal of DNAN and formation of its final reductive product 2,4-diaminoanisole (DAAN) were notably improved in the ZVI coupled biosystem. In the ZVI coupled biosystem and biotic control system, complete removal of DNAN could be achieved within 4 h and 20 h, respectively. However, only 28.71 ± 5.06% of DNAN could be removed in the ZVI control system after 20 h. Correspondingly, the formation efficiencies of DAAN in the ZVI coupled biosystem, biotic control system and ZVI control system were 99.66 ± 0.70%, 16.99 ± 1.73% and 0.00 ± 0.00%, respectively. The increased DNAN removal and DAAN formation in the ZVI coupled biosystem was linked to the high accumulation of formate, low oxidation–reduction potential (ORP) and great pH self-buffering capability, which was provided by the addition of ZVI. Compared with the biotic control system, the production of CH₄ was significantly accelerated in the ZVI coupled biosystem, indicating that a favorable environment for methanogens was created at the presence of ZVI. Especially, the ZVI coupled biosystem displayed a more stable performance in terms of DNAN reduction with the coexistence of the competitive electron acceptors, such as nitrate and sulfate. Therefore, the ZVI coupled biosystem could be a promising alternative to the conventional anaerobic reduction process for the removal of multi-substituted NACs from wastewater.