Elucidating the role of carbon shell in autotrophic denitrification driven by carbon-coated nanoscale zerovalent iron

Iron-carbon micro-electrolysis (IC-ME) can promote Fe-0 corrosion to provide H-2 or e(-)& nbsp;as electron donors for autotrophic denitrifier under organic-limited wastewater, but also stimulate the chemical reduction of NO3-N to undesired NH4-N. Therefore, it is still a challenge to optimize the eletron pathways provided by Fe-0 to improve its eletron selectivity for biodenitrification. Herein, a Carbon-coated Iron (Fe-0@C) Autotrophic Denitrification (CCIAD) system was first established to achieve higher removal efficiency of NO3-N (95%) and TN (84%) without NO2-N accumulation, and the role of carbon shell (CS) in Fe-0@C was systematically evaluated. Hydrophobic CS could prevent iron oxidation from oxygen and isolate Fe0 from NO3-N to alleviate the competition of biological and chemical processes for reducing nitrate. In addition, the CS promoted e(-)& nbsp;generation, while inhibited the adsorption of NO3-N, thereby increasing the H-2 production. Therefore, the assembly of carbon coated Fe0 regulated the electron pathway so that H-2 became the main electron donor and dominated the autotrophic denitrification, thereby improving the electron efficiency of Fe-0 (82.7%). The sustained electron release of Fe-0@C improved its TN removal capacity (78 mg N/g Fe). This study shed light on the electronic pathways provided by Fe-0@C and advanced our understanding of Fe-0@C-based bio-denitrification for the purpose of next generation Fe-0 design.

Automated summary

A Carbon-coated Iron Autotrophic Denitrification (CCIAD) system was established to achieve higher removal efficiency of NO3-N and TN by optimizing electron pathways provided by Fe-0.