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Calcium chloride adsorption at liquid-liquid interfaces: A molecular dynamics simulation study

Khiabani, N. P. and Bahramian, A. and Chen, P. and Pourafshary, P. and Goddard, W. A., III and Ejtehadi, M. R. (2017) Calcium chloride adsorption at liquid-liquid interfaces: A molecular dynamics simulation study. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 527 . pp. 70-80. ISSN 0927-7757. http://resolver.caltech.edu/CaltechAUTHORS:20170511-143027738

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Abstract

We carried out molecular dynamics simulations (MD) to investigate the adsorption of calcium chloride (CaCl_2) at n-hexane-water interfaces. We also measured the interfacial tensions (IFT) of the selected systems making use of the pendant-drop method. The histograms of hexane, water, and the ions indicate an electrical double layer (EDL) near the interface. The trend of the EDL indicates that chloride anions intend to adsorb to the interface more intrinsically than calcium cations. The measured interfacial width of the n-hexane-water interfaces decreases with the salt concentration. The average densities of the interfacial and bulk aqueous solutions demonstrate density heterogeneity in the direction perpendicular to the interface. The calculated density profiles enabled us to measure the adsorption values of each component. It is found that the salt particles are repelled from the liquid-liquid interface, resulting in an enriched bulk solution with salt. We, therefore, report negative adsorptions of CaCl_2 and the consequent reproduced increasing IFT with salt concentration. Consistent with the EDL trends, the negative adsorption of calcium cations is higher than that of chloride anions.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.colsurfa.2017.05.019DOIArticle
http://www.sciencedirect.com/science/article/pii/S0927775717304417PublisherArticle
ORCID:
AuthorORCID
Goddard, W. A., III0000-0003-0097-5716
Additional Information:© 2017 Elsevier B.V. Received 19 March 2017, Revised 10 May 2017, Accepted 10 May 2017, Available online 11 May 2017.
Subject Keywords:Molecular Dynamics Simulation; Liquid-Liquid Interfaces; Electrical Double Layer; Confined Aqueous Solutions; Density Heterogeneity; Negative Adsorption
Record Number:CaltechAUTHORS:20170511-143027738
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170511-143027738
Official Citation:N.P. Khiabani, A. Bahramian, P. Chen, P. Pourafshary, W.A. Goddard III, M.R. Ejtehadi, Calcium chloride adsorption at liquid-liquid interfaces: A molecular dynamics simulation study, Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 527, 20 August 2017, Pages 70-80, ISSN 0927-7757, https://doi.org/10.1016/j.colsurfa.2017.05.019. (http://www.sciencedirect.com/science/article/pii/S0927775717304417)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77378
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 May 2017 22:34
Last Modified:02 Jun 2017 20:44

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