Hg⁰ Removal by Straw Biochars Prepared with Clean Microwave/H₂O₂ Modification

Abstract

Biochar is one of the most promising adsorbents for Hg 0 from flue gas due to renewable raw materials. Cotton straw and maize straw biochars prepared by microwave activation and H 2 O 2 modification were used for removing Hg 0 from flue gas. Hg 0 capture efficiency and mechanism on biochars were studied. Cotton straw and maize straw biochars modified with 2 and 10 % H 2 O 2 , respectively, show optimal Hg 0 removal performance exceeding that of activated carbon. Microwave activation and H 2 O 2 impregnation greatly improve the BET surface areas of the biochars. H 2 O 2 impregnation increases the number of O-containing functional groups, i.e., O-H and C-O, on the biochar surface, enhancing Hg 0 removal. Chemisorption dominates the Hg 0 capture on biochars.