Removal of H₂S using a new Ce(IV) redox mediator by a mediated electrochemical oxidation process

Abstract

Abstract BACKGROUND: Hydrogen sulfide (H 2 S) from industrial activities and anaerobic manure decomposition in commercial livestock animal operations is an offensive malodorous and toxic gas even in small concentrations, causing serious discomfort and health and social problems. The objective of this study was to employ for the first time a novel, attractive, low cost, environmentally benign mediated electrochemical oxidation (MEO) process with Ce(IV) as the redox catalyst for H 2 S gas removal from an H 2 S–air feed mixture. RESULTS: The influence of liquid flow rate ( Q L ) from 2–4 L min −1 , gas flow rate ( Q G ) from 30–70 L min −1 , H 2 S concentration in the H 2 S–air feed mixture from 5–15 ppm, and Ce(III) pre‐mediator concentration in the electrochemical cell from 0.1–1 mol L −1 on H 2 S removal efficiency were investigated. Both liquid and gas flow rates influenced the removal efficiencies, but in opposite directions. Nearly 98% H 2 S removal was achieved when the concentration of Ce(IV) mediator ion in the flowing scrubbing liquid reached 0.08 mol L −1 . CONCLUSIONS: The new MEO method proved promising for H 2 S removal, achieving high removal efficiency. Integration of the electrochemical cell with the scrubber set‐up ensured continuous regeneration of the mediator and its repeated reuse for H 2 S removal, avoiding use of additional chemicals. Since the process works at room temperature and atmospheric pressure utilizing conventional transition metal oxide electrodes more commonly used in industrial applications, it is also safe and economical. Copyright © 2008 Society of Chemical Industry