Electricity generation from iron EDTA-based liquid redox sulfur recovery process with enhanced stability of EDTA

• A sustainable and stable liquid redox process was proposed to recover electricity and sulfur from waste pollutant H2S.
• The fuel cell was employed into iron EDTA-based liquid redox sulfur recovery technique.
• The optimal pH, which was turned out to be 9, maximally produced electricity as well as effectively captured H2S.
• Fuel cell provides an innovative way to enhance the stability of EDTA.

In this study, an innovative iron EDTA-based H2S capture technology was proposed. Just like currently available approaches, this system allows to capture H2S and convert it into element sulfur. It does so, however, with net energy production and without absorbent degradation. The system, consisting of an absorber and a fuel cell units, absorbs gaseous H2S and oxidize it to elemental sulfur in the absorber compartment, and in the fuel cell unit converts the reduced form of the absorbent [Fe(II)EDTA]2− back to [Fe(III)EDTA]−, generating electricity. When solution pH was raised from 7 to 10, more gaseous H2S was absorbed into [Fe(III)EDTA]−, resulting in increased production [Fe(II)EDTA]2−. This reduced form of the absorbent, which should be subsequently regenerated for continuous operation, serves as a fuel in a Fe(II)-based fuel cell. Fuel cell performance was also found to be strongly affected by solution pH, and the highest maximum power density of 0.832 mW cm−2 was achieved at pH 9 and 60 °C. At this condition, more than 80% of [Fe(III)EDTA]− was recovered from [Fe(II)EDTA]2− in 2 h without any noticeable degradation of EDTA, amounted to the oxidation rate of 147 g Fe h−1 m−2 anode surface area. This study provides demonstration of many desirable aspects for field implementation, such as electricity generation, sulfur recovery and long-term stability of the absorbent.

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