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A computational study of the interaction of organic surfactants with goethite alpha-FeO(OH) surfaces

Santos-Carballal, D; Du, Z; King, HE; de Leeuw, NH; (2016) A computational study of the interaction of organic surfactants with goethite alpha-FeO(OH) surfaces. RSC Advances , 6 (94) pp. 91893-91903. 10.1039/c6ra12377e. Green open access

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Abstract

We have studied the adsorption of three organic molecules onto different surfaces of goethite α-FeO(OH) using atomistic simulation techniques. New interatomic potentials for the interaction between goethite and the organic molecules were developed. In the majority of cases the organic molecules were found to be capable of forming a coordinate bond via their carbonyl oxygen atom with a surface iron ion. In addition, weaker hydrogen bonds were formed between the organic molecules and the surfaces. The largest adsorption energies were obtained for the modes of adsorption where the organic molecules bridged or spanned the periodic grooves or dips present on the goethite surfaces, thus forming several interactions between the molecule and the surface. Among all adsorbates studied, the hydroxamic acid molecule in the eclipsed conformation releases the largest adsorption energy when it interacts with goethite surfaces, followed by the staggered conformations of hydroxyethanal and methanoic acid molecules. The adsorption energies are in the range of −60.0 to −186.4 kJ mol−1. Due to the surface structure, as well as the flexibility and size of hydroxamic acid and hydroxyethanal, in most cases these adsorbate molecules lose their planarity with respect to the structure of the isolated molecules. We found that the replacement of pre-adsorbed water by the organic adsorbates is an exothermic process on all the goethite surfaces studied. The removal by sorption onto iron particles of humic and fulvic acids, the major substituents of natural organic matter (NOM) that pollutes aquifers and soils, is corroborated by our calculations of the adsorption of surfactants with the same functional groups as the surfaces of oxidised iron particles.

Type: Article
Title: A computational study of the interaction of organic surfactants with goethite alpha-FeO(OH) surfaces
Open access status: An open access version is available from UCL Discovery
DOI: 10.1039/c6ra12377e
Publisher version: http://dx.doi.org/10.1039/c6ra12377e
Language: English
Additional information: This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (http://creativecommons.org/licenses/by/3.0/)
Keywords: Science & Technology, Physical Sciences, Chemistry, Multidisciplinary, Chemistry, Density-functional Theory, Zero-valent Iron, Atomistic Simulation, Computer-simulation, In-situ, Competitive Adsorption, Enhanced Remediation, Contaminated Soil, Unique Properties, Calcium-fluoride
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/1526378
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