Micro-nanobubbles can spontaneously generate hydroxyl free radicals (• OH). Urea is a cheap reductant and can react with NOx species, and their products are nontoxic and harmless N 2 , CO 2 and H 2 O. In this study, a Wet Direct Recycling Micro-nanobubble Flue Gas Multi-pollutants Removal System (WDRMRS) was developed for the simultaneous removal of NO, SO 2 and Hg 0 . In this system, a micro-nanobubble generator (MNBG) was used to produce a micro-nanobubble gas-liquid dispersion system (MNBGLS) through recycling the urea solution from the reactor and the simulated flue gas composed of N 2 , NO, SO 2 and Hg 0 . The MNBGLS, which has a large gas-liquid dispersion interface, was recycled continuously from the MNBG to the reactor, thus achieving cyclic absorption of various pollutants. All of the investigated parameters, including the initial pH and temperature of the absorbent as well as the concentrations of urea, NO and SO 2 had significant effects on the NO removal efficiency but did not significantly affect the SO 2 removal efficiency, whereas only the initial solution pH and NO concentration affected the Hg 0 removal efficiency. The analysis results of the reaction mechanism showed that • OH played a critical role in the removal of various pollutants. After the treatment by this system, the main removal products were HgO sediment, SO 4 2− and NH 4+ which could be easily recycled.

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Micro-nanobubbles can spontaneously generate hydroxyl free radicals (*OH). Urea is a cheap reductant and can react with NOx species, and their products are nontoxic and harmless N2, CO2 and H2O. In this study, a Wet Direct Recycling Micro-nanobubble Flue Gas Multi-pollutants Removal System (WDRMRS) was developed for the simultaneous removal of NO, SO2 and Hg0. In this system, a micro-nanobubble generator (MNBG) was used to produce a micro-nanobubble gas-liquid dispersion system (MNBGLS) through recycling the urea solution from the reactor and the simulated flue gas composed of N2, NO, SO2 and Hg0. The MNBGLS, which has a large gas-liquid dispersion interface, was recycled continuously from the MNBG to the reactor, thus achieving cyclic absorption of various pollutants. All of the investigated parameters, including the initial pH and temperature of the absorbent as well as the concentrations of urea, NO and SO2 had significant effects on the NO removal efficiency but did not significantly affect the SO2 removal efficiency, whereas only the initial solution pH and NO concentration affected the Hg0 removal efficiency. The analysis results of the reaction mechanism showed that played a critical role in the removal of various pollutants. After the treatment by this system, the main removal products were HgO sediment, and which could be easily recycled.