Review of mediated electroscrubbing technologies for gas pollutant removal

This review covers the scientific literature within the field of scrubbers with electrochemical regeneration of the active compounds, i.e. electroscrubbers. In the publications 15 different solvent redox elements are considered as active compounds for electroscrubbing. Electroscrubbing applications are mainly focused on removal of H 2 S or NO x /SO 2 , however, other pollutants such as CH 3 SH, NH 3 or VOCs have also been the focus. In the literature, H 2 S removal receives the most interest and is currently being tested on pilot scale. Key factors for designing an electroscrubber include the redox potential of the active solvent compound, its solubility and reactivity with the target pollutant, and the minimization of unwanted side reactions. Performance indicators such as Faradaic efficiency, current efficiency and removal efficiency can be used to determine the feasibility of the electroscrubbing technologies. Generally, electroscrubbers are found to have a high removal rate and efficient regeneration of the active redox compounds. The electroscrubbing processes also display fast reaction kinetics. Many processes reported removal rates exceeding 99 %, which could limit the necessity for further polishing steps. However, the presence of unwanted side reactions can potentially limit the efficiency of the processes. Future studies should focus on limiting these side reactions and thereby raising the efficiency of the processes. Currently, electroscrubbing is not employed at an industrial scale, and the literature on the subject remains limited. However, it is likely that electroscrubbing will play a bigger role as more and more industries move towards electrification. • Electroscrubbing technologies offer a sustainable alternative to conventional absorption processes • Electroscrubbing consumes only electrical power and generally achieves a high degree of purification • Electroscrubbers exist only on a laboratory and demonstration scale with most interest being in removal of sulfur and NO x • Feasibility of electroscrubbers relies on the oxidation/reduction potential of the active compound compared to the impurity • Unwanted side reactions in electroscrubbing systems can increase the cost of removal by lowering energy efficiency