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Molecular Dynamics Simulations of the Adsorption of Phthalate Esters on Smectite Clay Surfaces

Author(s): Willemsen, Jennifer AR; Myneni, Satish CB; Bourg, Ian C

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dc.contributor.authorWillemsen, Jennifer AR-
dc.contributor.authorMyneni, Satish CB-
dc.contributor.authorBourg, Ian C-
dc.date.accessioned2022-01-25T14:49:34Z-
dc.date.available2022-01-25T14:49:34Z-
dc.date.issued2019-06-06en_US
dc.identifier.citationWillemsen, Jennifer AR, Satish CB Myneni, and Ian C. Bourg. "Molecular dynamics simulations of the adsorption of phthalate esters on smectite clay surfaces." The Journal of Physical Chemistry C 123, no. 22 (2019): 13624-13636. doi:10.1021/acs.jpcc.9b01864.en_US
dc.identifier.issn1932-7447-
dc.identifier.urihttp://arks.princeton.edu/ark:/88435/pr1nk36455-
dc.description.abstractThe partitioning of organic contaminants between water and solid surfaces is a key process controlling their fate and transport in natural environments. A novel methodology was developed to predict the adsorption of organic contaminants by smectite clay minerals (high specific surface area adsorbents abundant in natural soils) using molecular dynamics (MD) simulations. The methodology models a stack of flexible Ca-montmorillonite lamellae in direct contact with a bulk aqueous reservoir and uses the metadynamics technique to facilitate the exploration of the free energy landscape. The methodology was tested and validated in the case of six phthalate esters, widely used chemical plasticizers with endocrine disrupting properties. Simulation predictions reveal strong phthalate adsorption, especially for the larger and more hydrophobic phthalates. Predicted partition coefficients (Kd values) are consistent with collected batch experimental data. Adsorption was observed on both the exterior basal surfaces and within the interlayer nanopore, with phthalate molecules predominately adopting a flat orientation on the clay surface. Intercalation was also detected in complementary X-ray diffraction (XRD) experiments. A strong inverse relationship between extent of adsorption and clay surface charge density was observed, as phthalate molecules preferentially occupied the more hydrophobic uncharged patches on each surface. Detailed analysis of the free energy of adsorption revealed that phthalate affinity for the clay surface results from a small favorable van der Waals contribution and a large favorable entropic contribution. Overall, this research demonstrates the substantial affinity of smectite clays for phthalate esters and establishes a computational methodology capable of predicting the water–clay partition coefficients of organic contaminants, a key parameter in environmental fate and transport models.en_US
dc.format.extent13624 - 13636en_US
dc.language.isoen_USen_US
dc.relation.ispartofJournal of Physical Chemistry Cen_US
dc.rightsFinal published version. This is an open access article.en_US
dc.titleMolecular Dynamics Simulations of the Adsorption of Phthalate Esters on Smectite Clay Surfacesen_US
dc.typeJournal Articleen_US
dc.identifier.doidoi:10.1021/acs.jpcc.9b01864-
dc.date.eissued2019-05-13en_US
dc.identifier.eissn1932-7455-
pu.type.symplectichttp://www.symplectic.co.uk/publications/atom-terms/1.0/journal-articleen_US

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