Self-Sustainable Bioelectrochemical Sulfur Recovery from Hydrogen Sulfide Driven by a Ferric Ion-Mediated Biocathode

Abstract

Bioelectrochemical systems allow the conversion of hydrogen sulfide (H2S) to sulfur resource accompanied by electricity generation, but the low efficiency and poor process stability severely hamper their practical application. In contrast to conventional bioelectrochemical systems with bioanode, here we report an efficient and highly-stable bioelectrochemical sulfur recovery system (BESRS) consisting of an abiotic sulfide oxidation anode with a ferric ion-mediated biocathode. The acidophilic bacterium Acidithiobacillus ferrooxidans was used as a self-renewable biocatalyst, and ferric ions (Fe3+) were used as redox mediators to enhance the oxygen reduction reaction kinetics. Importantly, a stable acidic pH of the catholyte, which is essential to keep the Fe3+ dissolved, was maintained in this system due to spontaneous compensation of acidity by the continuous H2S supply; thus, no pH adjustment is needed. At the anode, H2S was selectively and efficiently converted into elemental sulfur particles at a sulfide oxidizing rate (799 mg L-1 d-1), surpassing all the existing bioelectrochemical systems. The overall system achieved a stable power output of approximately 100 mW/m2 and 100% H2S removal during 50 h of continuous operation. The high process stability, sustainability and easy-scalability of the BESRS make it highly desirable for resource-oriented treatment of H2S-containing gases/wastewaters.

Keywords: bioelectrochemical system, hydrogen sulfide, selective oxidation, Acidithiobacillus ferrooxidans, sulfur recovery, electricity generation