Multimedia Mercury Recovery from Coal-Fired Power Plants Utilizing N-Containing Conjugated Polymer Functionalized Fly Ash

Abstract

To recover multimedia mercury from coal-fired power plants, a novel N-containing conjugated polymer (polyaniline and polypyrrole) functionalized fly ash was prepared, which could continuously adsorb 99.2% of gaseous Hg 0 at a high space velocity of 368,500 h −1 and nearly 100% of aqueous Hg 2+ in the solution pH range of 2−12. The adsorption capacities of Hg 0 and Hg 2+ reach 1.62 and 101.36 mg/g, respectively. Such a kind of adsorbent has good environmental applicability, i.e. good resistance to coexisting O 2 /NO/SO 2 and coexisting Na + /K + /Ca 2+ /Mg 2+ /SO 4 2−. This adsorbent has very low specific resistances (6 × 10 6 −5 × 10 9 Ω•cm) and thus can be easily collected by an electrostatic precipitator under low-voltage (0.1−0.8 kV). The Hg-saturated adsorbent can desorb almost 100% Hg under relatively low temperature (<250 °C). Characterization and theoretical calculations reveal that conjugated-N is the critical site for adsorbing both Hg 0 and Hg 2+ as well as activating chlorine. Gaseous Hg 0 is oxidized and adsorbed in the form of Hg X Cl X (ad), while aqueous Hg 2+ is adsorbed to form a complex with conjugated-N, and parts of Hg 2+ are reduced to Hg + by conjugated-N. This adsorbent can be easily large-scale manufactured; thus, this novel solid waste functionalization method is promising to be applied in coal-fired power plants and other Hg-involving industrial scenes.