Enhancing simultaneous desulfurization and denitrification efficiency of cement kiln exhaust gas via co-catalytic Fenton oxidation process

Traditional Fenton reaction can hardly achieve the simultaneous desulfurization (de-SO2) and denitrification (de-NOx) for the cement kiln exhaust gas, due to the low production of free radicals as the limited Fe2+/Fe3+ cycle. Herein, an enhanced Fenton oxidation process was developed to remove SO2 and NOx efficiently, through improved Fe3+/Fe2+ conversion via the co-catalytic effect of metal sulfides and multi-metal oxysulfides. Among them, the WS2/Fe2+/H2O2 system showed the de-SO2 and de-NOx efficiency of 100% and 83.5%, respectively, and nearly no decrease in efficiency after 300 min. The highest initial de-NOx efficiency of 95.3% was achieved when Co-Mo-W-(5-4) served as co-catalyst, and the efficiency and stability were further improved after coupling NaSO3 solution absorption. Moreover, •OH was identified as the primary reactive oxygen species (ROS) for SO2 and NOx oxidation, then a reaction mechanism focusing on the reactive oxygen species (ROS) generation as well as NOx and SO2 removal was proposed based on EPR, XPS, FTIR, and Raman analysis. Thus, the results provide theoretical and technical support for developing de-SO2 and de-NOx technologies of cement kiln exhaust gas within a single process to achieve cleaner production.