# Charge Effects on the Adsorption of Octanoic Acid and Octanoate at Carbonates

## TL;DR

This study shows how the charge of acids affects their adsorption on carbonate surfaces, emphasizing the need for accurate charge correction methods.

## Contribution

The paper introduces the importance of using SCPC to correct charge effects in adsorption simulations of deprotonated acids on carbonates.

## Key findings

- Coadsorption models underestimate acid–carbonate interactions, leading to inaccurate adsorption predictions.
- Protonated acids form more covalent bonds, while deprotonated acids show ionic interactions with carbonates.
- SCPC improves the accuracy of adsorption energy calculations for charged molecules on mineral surfaces.

## Abstract

In this work, we investigate the adsorption behavior
of protonated
and deprotonated acids on carbonate surfaces, employing density functional
theory (DFT) simulations and the self-consistent potential correction
(SCPC) for the charged deprotonated acid. By comparing the coadsorption
models with the SCPC method, we have observed significant differences
in the adsorption energies, indicating that coadsorption underestimates
the stability of the acid–carbonate interactions, even leading
to changes from favorable to unfavorable adsorption on magnesites.
Our study highlights the distinct chemical interactions of protonated
and deprotonated acids with carbonate surfaces, revealing a more covalent
bonding nature for protonated acids and a predominantly ionic character
for deprotonated acids. Hence, we highlight the importance of employing
charge correction methods, such as the SCPC, for a more accurate representation
of the adsorption of charged molecules on mineral surfaces, which
could be extended to other systems.