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Comparison of various chemical compounds for the removal of SO2 and NOx with wet scrubbing for marine diesel engines

Lookup NU author(s): Dr Terence Chin Chin, Dr Ivan CK TamORCiD, Dr Chun Yang Yin



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


© 2021, The Author(s).Seawater, NaOH, NaClO, NaClO2, H2O2, and KMnO4 were used as scrubbing liquids to react with SOx and NOx separately in a customized wet scrubber. The absorption of SO2 in the aqueous phase was influenced by three factors: pH, ionic concentration, and oxidation potential. For NOx removal, the effectiveness of various chemical compounds can be ranked from least to most effective as follows: seawater, NaOH, H2O2 < NaClO < KMnO4 < NaClO2. This effectiveness was influenced by the chemical compound’s ability to oxidize NO to NO2, absorb the NO2 that was formed, and retaining the nitrogen in the aqueous phase. High oxidation potential promoted the oxidation of NO to NO2 but hindered the absorption of NO2. NaClO2 was superior compared to NaClO in all three categories of oxidizing, absorption and retention. NaClO could not retain a significant amount of NO2 which it absorbed in the aqueous phase. The pH around 8 provided a good balance between oxidation versus absorption/retention and reactant utilization for the chlorine-based oxidants. KMnO4 had the lowest reactant consumption rate; only half a mole was consumed for every mole of NO removed, compared to around 2–3 mol of chlorite or 3–5 mol of hypochlorite.

Publication metadata

Author(s): Chin T, Tam IC, Yin C-Y

Publication type: Article

Publication status: Published

Journal: Environmental Science and Pollution Research

Year: 2022

Volume: 29

Pages: 8873-8891

Print publication date: 01/02/2022

Online publication date: 08/09/2021

Acceptance date: 20/08/2021

Date deposited: 22/09/2021

ISSN (print): 0944-1344

ISSN (electronic): 1614-7499

Publisher: Springer Science and Business Media Deutschland GmbH


DOI: 10.1007/s11356-021-16155-9


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Funder referenceFunder name
general research fund of Nanyang Polytechnic under the School of Applied Sciencs (N-OOE08-54041-LHAD-LHLB01-220519).