Simultaneous deSOx and deNOx of marine vessels flue gas on ZnO-CuO/rGO: Photocatalytic oxidation kinetics

Marine Pollution Convention has been updated to prevent the excessive emissions from diesel machine. For high concentrated, large fluxed SO2 and NO photocatalytic oxidation, a novel dual stages oxidation-scrubbing process was proposed. The p–n junction ZnO-CuO/rGO ternary catalysts were prepared via the co-precipitation route and supported on reduced graphene oxide (rGO). The UV–vis spectra showed that the bandgap Eg of ZnO-CuO/rGO was notably narrowed to 2.3–2.6 eV for facilitating electron transfer, and its flat band potential of was −0.54 V versus Ag/AgCl. The PL spectra and photocurrent curves revealed that the formation of heterojunctions and the introduction of graphene promoted an efficient separation of the photo-induced charge carriers. The photocatalytic activity of the ZnO-CuO/rGO with 5 wt% GO was evaluated for simultaneous DeSOx and DeNOx, and 97% desulfurization rate and 64% denitration rate could be reached under GHSV 2000 h−1 for 270 min. In seawater scrubber, ZnO-CuO/rGO(5%) addition made SO32− conversion was 80.72%. The radical scavenging experiments demonstrated that holes (h+) and superoxide radicals (•O2−) contributed most to SO32− photocatalytic oxidation. Kinetic studies showed that SO32− oxidation on ZnO-CuO/rGO fitted the L-H model. The mechanism of photocatalytic oxidation in gas and liquid phases were also proposed to address the reaction pathway.