Hg0 removal performance of magnetic raffinate slag-based sorbents: Mechanism study on oxidation modification

Abstract

The sulfur-containing carbon-based sorbent was regarded as potential sorbent for the removal of toxic elemental mercury (Hg0). However, due to its lower reaction temperature and the stronger Hg0 oxidation capacity of oxides at higher temperature, oxidation modification on sulfur-containing raffinate slag-based sorbents was proposed in the study. The effects of O2, H2O2 and KMnO4 oxidation modification on Hg0 removal performance and physicochemical properties of sorbents were investigated. The oxidation modification had little effect on pore structure of sorbents, but mainly affected the content and valence state of sulfur and oxygen elements. Compared with H2O2 oxidation, KMnO4 oxidation was more conducive to forming active lattice oxygen (Oα). The valence state of manganese bound with Oα influenced Hg0 capture a lot, and Oα in MnO2 showed strong oxidation capacity to Hg0. Active S22−and Oα in A850-0.1KMnO4-12h sorbent could both promote the Hg0 removal with HgS and HgO formed in used sorbent. The saturated magnetization of A850-0.1KMnO4-12h sorbent was 5.39 emu·g−1, making it possible to separate mercury-containing sorbents from fly ash. It showed good resistance to low concentration of SO2, and NO could promote its Hg0 removal ability. Meanwhile, KMnO4 oxidation successfully improved the Hg0 removal performance at higher reaction temperature and gas hourly space velocity.