Development of CuInS2/g-C3N4 nanolayer for efficient adsorption of elemental mercury from coal combustion flue gas

Abstract

The flue gas with high concentration of mercury is often encountered in coal combustion flue gas treatment, so sorbents with sufficient adsorption capacity is urgently required to capture and immobilize mercury. CuInS2/g-C3N4 (CIS/GCN), synthesized by one step hydrothermal method, was developed as a suitable candidate sorbent to replace current commercial sorbents to remove Hg0 from flue gas, as a co-benefit of electrostatistic precipitator (ESP). Due to the abundance of surface metal cation vacancies and sulfur sites, compared to most sorbents, CIS/GCN exhibited excellent Hg0 adsorption capacity reaching upto 27.48 mg g−1, and its removal efficiency arrived at 100% at 120 °C. Besides, CIS/GCN depicted outstanding Hg0 removal capabilities in simulated flue gas (SFG) and a wide temperature range (40–160 °C). A long-term evaluation of 10 h was carried out on an optimal sorbent, and the sample adsorption capacity remained superb. Furthermore, gas-phase Hg0 was firstly captured by metal cation vacancies and diffused along the surface, the surface diffusion rate constant was calculated as 2.54 × 10−32 s−1, and then combined with S22− over the sulfur sites to form α-HgS and β-HgS, which were the most stable mercury compounds, XPS analysis and TPD experiment further demonstrated this process. With above outstanding Hg0 adsorption performance, CIS/GCN sorbents were authenticated to be a forceful candidate for current commercial activated carbon for Hg0 immobilization. This work is to provide methods for controlling the emission of Hg0 from coal combustion flue gas in industrial application.