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Table 2 Concentration-dependent adsorption constants of \({\text {[Mo]}_{\text{aq}}}\) onto Fh: insights from reactive MD and comparisons with SCM models

From: Probing atomic-scale processes at the ferrihydrite-water interface with reactive molecular dynamics

Species

\(\text {P}_{\textit{o}}\)

FeOH

H+

\({{\text{MoO}_4}}^{2-}\)

\(\text {LogK}_a\)

\((\sigma )\)

Fh-\({\text {[Mo]}_{\text{aq}}}\) (Mo-1)

–

–

–

1

0.864

0.001

Fh-\({\text {[Mo]}_{\text{aq}}}\) (Mo-2)

–

–

–

2

2.543

0.006

Fh-\({\text {[Mo]}_{\text{aq}}}\) (Mo-3)

–

–

–

3

3.785

0.0001

Fh-\({\text {[Mo]}_{\text{aq}}}\) (Mo-6)

–

–

–

6

1.500

0.001

Fh-\({\text {[Mo]}_{\text{aq}}}\) (Mo-8)

–

–

–

8

2.664

0.0009

Weighted average

    

3.169

0.0002

a \({{\text{FeOHMoO}}_4}^{-2}\)

− 2

1

0

1

3.14b

0.039

c \({{\text{FeOHMoO}}_4}^{-2}\)

− 2

1

0

1

2.4

 
  1. Calculated adsorption equilibrium constant (uncertainty) \(\text {LogK}_a\) (\(\sigma\)) of \({\text {[Mo]}_{\text{aq}}}\) on the surface of Fh from free energies of adsorption derived from umbrella sampling PMFs
  2. aFrom diffuse layer model (DLM) (specific surface area: 600 \(\text {m}^2\) \(\text {g}^{-1}\), fixed site density: 0.205 mol \(\text {mol}^{-1}\) Fe, \(\text {P}_{\textit{o}}\) = \(\exp (-F\Psi _{\textit{o}}/RT)\), F: the Faraday constant, \(\Psi _{\textit{o}}\): electrostatic potential in the o-plane, R: gas constant, T: temperature) [23]
  3. bWeighted average of \(\text {LogK}_a\) values (3.05, 3.19, 3.37) from total Fe concentrations (M): 3 × \(10^{-3}\), 1 × \(10^{-3}\), 3 × \(10^{-4}\)
  4. cEstimated values from linear free energy relationships (LFER) [95]