Issue 4, 2024

Molecular mechanisms of dimethylarsinic acid adsorption onto aluminum substituted ferrihydrite surfaces

Abstract

Dimethylarsinic acid (DMA) is a common organic arsenic pollutant in the environment, and its distribution, migration, and transformation are greatly controlled by various active minerals. However, the bonding mechanisms of DMA on aluminum (Al)-substituted ferrihydrite is rarely explored. Here, ferrihydrite samples with Al substitution amounts of 0.00 ± 0.00 mol%, 3.02 ± 0.01 mol%, 6.71 ± 0.11 mol%, 12.89 ± 0.34 mol%, and 20.50 ± 0.76 mol% were prepared, characterized, and used to test DMA adsorption behaviors and mechanisms. With the increase of Al amount, the particle size and specific surface area of ferrihydrite particles slightly decrease, and the point of zero charge gradually increases. The reaction pH has a significant impact on the DMA adsorption onto mineral surfaces. When the pH is 3–6, the DMA adsorption density is almost unchanged being 0.74–0.77 μmol m−2; while pH > 6, the DMA adsorption density significantly decreases. With the increase in ionic strength, the DMA adsorption density onto Al-substituted ferrihydrite is almost unaffected at pH 6, but is greatly increased at pH 9. Isothermal adsorption experiments show that Al substitution significantly improves the DMA adsorption density on ferrihydrite by 46–61%, with a maximum enhancement at an Al substitution level of 6.70 mol%. Ionic strength effect test, Fourier transform infrared spectroscopy and As K-edge extended X-ray absorption fine structure spectroscopy analysis show that DMA forms bidentate binuclear inner-sphere complexes on ferrihydrite surfaces through As–OH rather than the –CH3 group at pH 6, but predominantly forms outer-sphere complexes at pH 9. With the increase of the Al substitution level in the mineral, DMA also forms monodentate mononuclear and outer-sphere complexes on solids at pH 6. These results provide deep insights into the interaction mechanisms and fates of organoarsenicals with natural Fe (hydr)oxide minerals.

Graphical abstract: Molecular mechanisms of dimethylarsinic acid adsorption onto aluminum substituted ferrihydrite surfaces

Supplementary files

Article information

Article type
Paper
Submitted
20 Sep 2023
Accepted
22 Feb 2024
First published
01 Mar 2024

Environ. Sci.: Nano, 2024,11, 1713-1723

Molecular mechanisms of dimethylarsinic acid adsorption onto aluminum substituted ferrihydrite surfaces

Y. Ge, J. Wang, F. Guo, M. Yuan, W. Wang, J. Li, J. Zhang, X. Feng, W. Tan, Y. Wu and H. Yin, Environ. Sci.: Nano, 2024, 11, 1713 DOI: 10.1039/D3EN00664F

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements