Removal of gaseous elemental mercury using corn stalk biochars modified by a green oxidation technology

Abstract

Straw biochars are the widely used carbon materials for adsorbing gaseous Hg0 due to developed porous structure. However, its application is restricted by scarcity of active sites on carbon surface. Existing modification methods such as acids, halides, sulfides, metal oxides, etc. have problem of secondary pollution. In this work, a corn stalk biochar modified with UV/H2O2 green modification technology was prepared to capture gaseous Hg0 for the first time. The physicochemical properties of the adsorbent and the effect of several key parameters containing H2O2 concentration, adsorption temperatures and common gas components on gaseous Hg0 capture were studied. The kinetic process and mechanisms of gaseous Hg0 adsorption were also expounded. Research indicated that through producing ·OH free radicals with high activity, UV/H2O2 green modification technology could not only improve pore structure of corn stalk biochar, but also make containing-O functional group more abundant on carbon surface, promoting gaseous Hg0 adsorption. Optimal H2O2 modification concentration and adsorption temperature are 3 wt% and 120 °C, respectively. The capture process of gaseous Hg0 accorded with quasi second-order kinetic equation. Chemisorbed oxygen (O*) and CO functional group show pivotal roles in the capture processes of gaseous Hg0.