Substantially enhanced degradation of nitrobenzene by biosponge iron system: Process and mechanisms

Abstract

Considering the high reactivity, cost-efficiency, environmental friendliness, the zero-valent iron-microbe (bio-ZVI) technology for refractory organic wastewater treatment has obtained worldwide attentions. This paper submerged sponge iron (SFe, a typical ZVI material) in activated sludge to form biological sponge iron (bio-SFe) systems, while the iron sludge and ordinary activated sludge systems were taken as blank control. To study the strengthening effect and degradation mechanism of bio-SFe systems, Nitrobenzene (NB) was chose as a target contaminant. The interaction between SFe and microorganisms improved the NB removal efficiency, prompted the formation of Fe(II)/ROS and facilitated the biodegradation process. Specifically, the Fenton-like effects for NB removal increased from 3.6 % in mono-SFe system to 11.79 % in SFe coupled with iron sludge system. This facilitated the production of OH could constantly attack and eventually mineralize NB. Additionally, biodegradation of NB was the predominant pathway (64.25 %), when iron sludge combined with SFe, the removal of NB could ascend to 92.11 %. SFe created a more favorable environment for certain core functional genera related to recalcitrant pollutants reduction and iron cycle. According to the accumulation of NH4+-N content and the identification of the degradation intermediates of NB in bio-SFe system, the partial reduction biodegradation of NB was finally confirmed.