Structures and properties of as oh 3 adsorption complexes on hydrated mackinawite fes surfaces a dft d2 study

Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b00107 • Publication Date Web: 24 Feb 2017 Downloaded from http://pubs.acs.org on February 28, 2017 Just Accepted “Just Accepte

Structures and properties of As(OH)3 adsorption complexes

on hydrated mackinawite (FeS) surfaces: A DFT-D2 study

Nelson Y Dzade, Alberto Roldan, and Nora H de Leeuw

Environ Sci Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b00107 • Publication Date (Web): 24 Feb 2017

Downloaded from http://pubs.acs.org on February 28, 2017

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oxide phases or pyrite Their results suggested that the arsenic uptake by freshly prepared

points mesh for bulk and surface calculations, respectively, which ensures electronic and

) (OH water surf As OH As

surf water

(OH As surf water

E − + represents the total energy of the adsorbate-substrate system, E water−surf

157

represents the total energy of the relevant hydrated FeS substrate, and

3 )

(OH As

u bulk relaxed

slab r

A

nE E

relaxed water n slab water

A

nE nE

d d

d

(1)

218

Within this definition, negative values correspond to inward relaxation (contraction) and

Information (Figure S2), whereas the calculated adsorption energies and optimized structural

associated with the lone pair electron density of the As and O atoms as shown in the highest

these bonds, in agreement with the elongated As−O bonds calculated for the As(OH)3

(http://www.archer.ac.uk), the UK’s national supercomputing service via our membership of

24 Mullet, M.; Boursiquot, S.; Ehrhardt, J.J Removal of hexavalent chromium from

51 Dzade, N.Y.; Roldan, A.; de Leeuw, N.H The surface chemistry of NOx on mackinawite

d(As‒O) /Å 1.798 1.811 1.796 1.810 1.829 1.813

1.801 1.818 1.800 1.811 1.829 1.813 1.811 1.841 1.826 1.813 1.829 1.813

d(O‒H) /Å 0.975 0.977 0.967 0.975 0.982 0.970

0.978 0.980 0.969 0.978 0.982 0.970 0.978 0.983 0.970 0.978 0.982 0.970

α(O−As−O) /° 90.17 88.79 90.86 97.25 96.92 97.34

99.84 99.75 99.61 97.48 96.94 97.36 100.94 103.22 100.89 97.57 96.99 97.37

α(As−O−H) /° 108.6 105.33 110.16 108.6 104.87 109.93

110.9 109.83 112.68 110.8 104.98 109.94 111.2 111.77 112.78 111.0 105.02 109.93

616

25

Table 3: Adsorption energies, variation of the total Bader charge, representative geometrical parameters, and interatomic distances of the

Table 4: Molecular vibrational frequencies (in cm-1) of adsorbed As(OH)3 at waterưFeS

639.1 (655)71

638.3 (655)71 3738.1 3711.5 3674.7

FeS(001)

Asưupưouter 695.1 620.7 585.8 3465.9 3182.9 3140.5 FeS(011) FeưAsOưFe 580.2 501.5 488.9 3715.1 3670.9 2829.1

FeS(111) FeưOưFe 673.5 616.5 456.1 3731.2 3204.2 2884.3

27

LIST OF FIGURES

Figure 1: The layered structure of mackinawite, with the tetragonal unit cell highlighted by

dash lines (Colour scheme: Fe = grey, S = yellow)

Figure 2: Side view of the geometry-optimized structures of hydrated FeS (a) (001), (b)

(011), and (111) surfaces (Colour scheme: Fe = grey, S = yellow, O = red, and H = white)

30

F

FF

(bottom) views (Colour scheme: Fe = grey, S = yellow, As = pink, O = red and H = white)

31

FFFFigure igure igure 5: (Right) PDOS for As(OH)3 in the (a) free state and adsorbed in the lowest-energy geometry at the water−FeS interfaces (b−d) (Left) the corresponding isosurfaces of the differential charge density, where the purple and orange contours indicate electron density increase and decrease by 0.02 e/Å3, respectively

Figure

Figure 6: PDOS for the interacting surface Fe d-states before and after the adsorption of

As(OH)3 at the (a) water−FeS(111) and (b) water−FeS(011) interface, and (c) for the

interacting surface S p-states at the water−FeS(001) interface

Adsorption complex of As(OH)3 at water-FeS(001) interface

79x39mm (300 x 300 DPI)