Gaseous Elemental Mercury Adsorption to Alcohol-Enhanced Molybdenum Disulfide: Kinetics and Mechanism

Abstract

Heterogeneous absorption is a potential technology for Hg⁰ contamination control in flue gas, in which the gas-liquid mass transfer of Hg⁰ (GLMT-Hg⁰) is a key problem that needs to be solved. In this work, an alcohol-enhanced MoS₂/H₂O system was proposed and investigated for Hg⁰ removal. The results showed that adding alcohol can improve Hg⁰ removal efficiency. Especially, adding 60 mM butanol can reach 94% of Hg⁰ removal efficiency. In addition, the effect of adding long carbon chains and monohydric alcohols is better than adding short carbon chains and polyhydric alcohols. The kinetics of Hg⁰ removal revealed that adding butanol increases E and K_G(Hg0)/k_G(Hg0), which can enhance GLMT-Hg⁰. The fate of Hg⁰ and the mechanism of its removal were revealed as Hg⁰ first being oxidized by Mo⁴⁺ to form a [Hg-Mo] complex, which reacts with an adjacent S site to form stable HgS. Most of the removed Hg was absorbed on MoS₂, which is more favorable to be separated from the solution for recycle and reuse.