Boosting the oxidative capacity of the Fe(0)/O2 system via an air-breathing cathode.

The corrosion of Fe(0) in the presence of O2 in nature can lead to the oxidation of organic compounds, but the efficiency is very limited. Herein, attempts were made to establish a galvanic system that separates the anodic Fe(0) oxidation reaction and the cathodic O2 reduction reaction using an air-breathing cathode. Compared with the chemical Fe(0)/O2 system, it exhibited a substantially higher capability of destroying a variety of pollutants, such as organic dyes (12 types), phenol, nitrobenzene, acetaminophen, phenol, and ethylenediaminetetraacetic acid. The degradation rate constant of a model dye (i.e., Rhodamine B) increased from 0.047 min-1 (chemical) to 1.412 min-1 (galvanic) under the passive air-breathing condition. The electric circuit design promoted Fe(0) dissolution to Fe(II) and triggered electron transfer that drives O2 reduction to H2O2, two important species responsible for the generation of HO• at high abundance. In addition, the galvanic Fe(0)/O2 system produces electricity while destroying pollutants. Tests with real Ni plating wastewater further demonstrated the capability of the system to oxidize complexed organics and phosphite. This study provides a new strategy for boosting the oxidative capacity of the Fe(0)/O2 system, which shows promise for acid wastewater treatment.