Elemental mercury adsorption and regeneration performance of sorbents FeMnOx enhanced via non-thermal plasma

Abstract

Recent laboratory experiments and field tests have demonstrated the potential for modified regenerable materials to be a cost-effective alternative to expensive activated carbon for mercury control in coal-fired power plants. To develop a competitive and commercially viable technology, better mercury capture and regeneration performances of regenerable sorbents are required. For this purpose, non-thermal plasma was used to treat the magnetic sorbents FeMnOx synthesized by co-precipitation. The mercury adsorption tests showed that the treated sorbents with non-thermal plasma had higher mercury removal efficiency than raw sorbents, and longer treatment time resulted in higher efficiency. The main reason was that the content of the high valence manganese oxides and lattice oxygen were greatly increased by non-thermal plasma treatment, and this played a significant role in the mercury removal process. Further analysis showed that the lattice oxygen coming from the stepwise reduction of manganese oxide (MnO2→Mn2O3→MnO) served as an oxidant in the reaction with Hg0. The NO, SO2 and H2O inhibited the mercury adsorption while O2 and HCl promoted mercury removal. High valence of manganese oxides and lattice oxygen were consumed during mercury adsorption, while non-thermal plasma treatment could replenish it and increase mercury removal regeneration performance better than without non-thermal plasma treatment. In summary, the combination of magnetic separation, thermal regeneration and plasma treatment makes FeMnOx an excellent recyclable sorbent for mercury emission control.