Pb(II) Adsorption on Isostructural Hydrated Alumina and Hematite (0001) Surfaces: A DFT Study

Abstract

The persistence of lead (Pb) in contaminated topsoil is ranked as one of the most serious environmental issues in the U.S. and other countries. Adsorption of Pb at the aqueous interface of nanoscale metal oxide and metal (oxy)hydroxide particles is perhaps the most significant process responsible for controlling contaminant sequestration and mobility, but the process is poorly understood at the molecular level. Experimental studies of absorption of Pb onto bulk minerals have indicated significant differences in reactivity, but the molecular basis for these differences has remained elusive due to the challenges of observing and modeling the complex chemistry that exists at the water-oxide interface. In this work, we present a detailed ab initio theoretical investigation aimed at understanding the fundamental physical and chemical characteristics of Pb adsorption onto the (0001) surface of two common minerals, R-Al 2 O 3 and R-Fe 2 O 3 . The results of our periodic density functional theory (DFT) calculations show that the adsorption energy of Pb(II) on hematite is more than four times the value on isostructural alumina with the same fully hydroxylated surface stoichiometry due to bonding interactions enabled by the partially occupied Fe d-band. Site preference for Pb(II) adsorption on alumina is shown to depend strongly on the cost to disrupt highly stable hydrogen bonding networks on the hydrated surface, but is less of a factor for the stronger Pb-hematite interaction. † Part of the special section "Physical Chemistry of Environmental Interfaces".

In silico approach to investigating the adsorption mechanisms of short chain perfluorinated sulfonic acids and perfluorooctane sulfonic acid on hydrated hematite surface

“…It was believed that the surface was fully hydroxylated in aqueous conditions (Liu et al, 1998). We noticed that there several different hydrated hematite (0 0 0 1) surfaces are known (Mason et al, 2009;Souvi et al, 2013;Wasserman et al, 1997), and in the consideration of our model and the ambient environment, the surface model was built symmetrically so that there is no net surface dipole. The construction of hydrated hematite (0 0 0 1) surface is presented detailedly in Support Information, Text S2 and Fig.…”

“…S1. After geometry optimization, we obtained a surface relaxed structure that was similar to the structure found in a previous study (Kerisit, 2011;Mason et al, 2009). The next consideration is the models of the PFSA and hydrated hematite (0 0 0 1) surface in environment for MD simulation.…”

Surface complexation of Pb(II) by hexagonal birnessite nanoparticles

“…Our principal objective is to examine whether Pb-DES is the only stable surface complex that can occur on the lateral edges of these nanoparticles. First-principles techniques such as DFT can be applied to reduce ambiguities and guide the interpretation of EXAFS spectra by providing complementary electronic structure and bonding information about metals adsorbed on mineral surfaces (Zhang et al, 2006;Sherman et al, 2008;Hattori et al, 2009;Mason et al, 2009;Kwon et al, 2009). In particular, spinpolarized DFT (i.e., electron densities are calculated separately for spin-up and spin-down electrons) accurately predicts crystal structures and electronic properties of Mn oxides (Singh, 1997;Mishra and Ceder, 1999;Pask et al, 2001), including birnessite (Kwon et al, 2009).…”

Experimental and Theoretical Study of Low-Dimensional Iron Oxide Nanostructures

“…Many DFT studies have emphasized on the structural, electronic, catalytic, and magnetic properties of metal-oxide, such as Fe 2 O 3, and Al 2 O 3 (Alvarez-Ramirez et al, 2004;Ma et al, 2006;Mason et al, 2009;Rohrbach et al, 2004;Rollmann et al, 2004;Zhong et al, 2008;Mason et al, 2010). It has been extended into other systems, e.g., carbon nanotubes or graphene (Li et al, 2010;Chattaraj et al, 2009), transition metals (Cramer et al, 2009), semiconductors (Jin et al, 2011), and metals (e.g., Pd, Au, Cu) (Yang et al, 2007).…”