Electrochemical and bioelectrochemical sulphide removal: A review

The increased demand for energy worldwide and the focus on the green shift have raised interest in renewable energy sources such as biogas. During biogas production, sulphide (H₂S, HS⁻ and S²⁻) is generated as a byproduct. Due to its corrosive, toxic, odorous, and inhibitory nature, sulphide is problematic in various industrial processes. Therefore, several techniques have been developed to remove sulphide from liquid and gaseous streams, including chemical absorption, chemical dosing, bioscrubbers, and biological oxidation. This review aims to elucidate electrochemical and bioelectrochemical sulphide removal methods, which are gaining increasing interest as possible supplements to existing technologies. In these systems, the sulphide oxidation rate is affected by the reactor design and operational parameters, including electrode materials, anodic potential, pH, temperature and conductivity. Anodic and bioanodic materials are highlighted here, focusing on recent material developments and surface modification techniques. Moreover, the review focuses on sulphide generation and inhibition in biogas production processes and introduces the prospect of removing sulphide and producing methane in one single bioelectrochemical reactor. This could introduce BESs for combined biogas upgrading and cleaning, thereby increasing the methane content and removing pollutants such as sulphide and ammonia in one unit.