Remarkable differences between copper-based sulfides and iron-based sulfides for the adsorption of high concentrations of gaseous elemental mercury: Mechanisms, kinetics, and significance

Qixing Hu; Chang Wang; Yang Geng; Xufan Zhang; Jian Mei; Shijian Yang

doi:10.1016/j.jcis.2020.08.067

Remarkable differences between copper-based sulfides and iron-based sulfides for the adsorption of high concentrations of gaseous elemental mercury: Mechanisms, kinetics, and significance

J Colloid Interface Sci. 2021 Jan 15;582(Pt B):581-590. doi: 10.1016/j.jcis.2020.08.067. Epub 2020 Aug 20.

Authors

Qixing Hu¹, Chang Wang¹, Yang Geng¹, Xufan Zhang¹, Jian Mei², Shijian Yang¹

Affiliations

¹ School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, PR China.
² School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, PR China. Electronic address: jsjhmj@126.com.

PMID: 32916570
DOI: 10.1016/j.jcis.2020.08.067

Abstract

Copper sulfides (CuS_x) and iron sulfides (FeS_x) have been developed to capture gaseous elemental mercury (Hg⁰) originating from the smelting flue gas. However, these compounds exhibit different Hg⁰ adsorption characteristics and Hg species adsorbed on CuS_x can be spontaneously released as gaseous Hg⁰. Following these findings, the adsorption/desorption kinetics of Hg⁰ onto and from FeS_x and CuS_x were determined. After comparing the kinetic parameters, the mechanisms behind some of the remarkable differences between FeS_x and CuS_x with respect to Hg⁰ adsorption were discovered. The Cu-S bond in CuS_x was not completely broken during Hg⁰ oxidation, but the SS bond in FeS_x was. Hence, the activation energy for the oxidation of Hg⁰ physically adsorbed on CuS_x was much lower than that for FeS_x, resulting in a much higher efficiency of CuS_x to oxidize Hg⁰ than FeS_x. However, the bond strength of Hg-S for HgS on CuS_x was weaker due to the sharing of S^2- in HgS with Cu⁺, resulting in a decrease in the thermal stability of HgS on CuS_x. Therefore, HgS adsorbed on Cu-based sulfides was metastable, and could be spontaneously decomposed to release moderate concentrations of gaseous Hg⁰, which was not preferable for capturing high concentrations of Hg⁰.

Keywords: Cu-based sulfides; Fe-based sulfides; Hg(0) adsorption; Hg(0) desorption; Kinetics.