Ab initio calculation of the adsorption of As, Cd, Cr, and Hg heavy metal atoms onto the illite(001) surface: Implications for soil pollution and reclamation

Chongchong Qi; Xinhang Xu; Qiusong Chen; Hui Liu; Xiaobo Min; Andy Fourie; Liyuan Chai

doi:10.1016/j.envpol.2022.120072

Ab initio calculation of the adsorption of As, Cd, Cr, and Hg heavy metal atoms onto the illite(001) surface: Implications for soil pollution and reclamation

Environ Pollut. 2022 Nov 1:312:120072. doi: 10.1016/j.envpol.2022.120072. Epub 2022 Sep 2.

Authors

Chongchong Qi¹, Xinhang Xu², Qiusong Chen², Hui Liu³, Xiaobo Min³, Andy Fourie⁴, Liyuan Chai³

Affiliations

¹ School of Resources and Safety Engineering, Central South University, Changsha, 410083, China; School of Molecular Science, University of Western Australia, Perth, 6009, Australia; School of Metallurgy and Environment, Central South University, Changsha, 410083, China. Electronic address: chongchong.qi@csu.edu.cn.
² School of Resources and Safety Engineering, Central South University, Changsha, 410083, China.
³ School of Metallurgy and Environment, Central South University, Changsha, 410083, China.
⁴ School of Civil, Environmental and Mining Engineering, University of Western Australia, Perth, 6009, Australia.

PMID: 36064056
DOI: 10.1016/j.envpol.2022.120072

Abstract

Elucidating the mechanisms of heavy metal (HM) adsorption on clay minerals is key to solving HM pollution in soil. In this study, the adsorption of four HM atoms (As, Cd, Cr, and Hg) on the illite(001) surface was investigated using density functional theory calculations. Different adsorption configurations were investigated and the electronic properties (i.e., adsorption energy (E_ad) and electron transfer) were analyzed. The E_ad values of the four HM atoms on the illite(001) surface were found to be As > Cr > Cd > Hg. The E_ad values for the most stable adsorption configurations of As, Cr, Cd, and Hg were -1.8554, -0.7982, -0.3358, and -0.2678 eV, respectively. The As atoms show effective chemisorption at all six adsorption sites, while Cd, Cr, and Hg atoms mainly exhibited physisorption. The hollow and top (O) sites were more favorable than the top (K) sites for the adsorption of HM atoms. The Gibbs free energy results show that the illite(001) surface was energetically favorable for the adsorption of As and Cr atoms under the influence of 298 K and 1 atm. After adsorption, there was a redistribution of positions and reconfiguration of the chemical bonding of the surface atoms, with a non-negligible influence around the upper surface atoms. Bader charge analysis shows electrons were transferred from the surface to the HM atoms, and a strong correlation between the valence electron variations and the adsorption energy was observed. HM atoms had a high electronic state overlap with the surface O atoms near the Fermi energy level, indicating that the surface O atoms, though not the topmost atoms around the surface, significantly influence HM adsorption. The above results show illite(001) preferentially adsorbed As among all four investigated HM atoms, indicating that soils containing a high proportion of illite might be more prone to As pollution.

Keywords: Bader charge; Clay minerals; Density functional theory; Heavy metal pollution; Surface energy.

MeSH terms

Adsorption
Cadmium / analysis
Clay
Environmental Pollution / analysis
Mercury* / analysis
Metals, Heavy* / analysis
Minerals / chemistry
Soil / chemistry
Soil Pollutants* / analysis

Substances

Metals, Heavy
Minerals
Soil
Soil Pollutants
Cadmium
illite
Mercury
Clay