Purification of Hg from flue gas by wet oxidation method and its mechanism: a review.

The vast majority of Hg can be removed while elemental mercury (Hg) can hardly be removed due to its characteristic of high volatility and insolubility in water. Till now, how to oxidize Hg to Hg is the key for the purification of Hg, especially when there are others pollutants, such as HCl, SO, and NOx. In this review, the method and mechanism of Hg purification from flue gas by HO, KMnO, NaClO, and O are reviewed comprehensively. It is concluded that the oxidation of Hg mainly depends on the electronic supply efficiency from the solution. The Fenton reagent, composed of HO and metal cations, is superior to O and the solution of KMnO and NaClO. Moreover, HCl, SO, and NOx in the flue gas can influence the oxidation and purification mechanism of Hg. It is found that HCl in flue gas had obvious auxo-action on the oxidation of mercury, and SO and NOx have different effects on the oxidation of Hg with the change of compositions and concentration of pollutants in the flue gas. In general, SO and NOx can slightly promote the oxidation of Hg due to the synergistic effect.