Document Type

Journal Article

Publisher

American Chemical Society

School

School of Engineering

Comments

This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, as:

Abramov, A., Keshavarz, A., & Iglauer, S. (2019). Wettability of fully hydroxylated and alkylated (001) alpha-quartz surface in carbon dioxide atmosphere. The Journal of Physical Chemistry C, 123(14), 9027–9040.

Copyright 2019 © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see the original publication available here

Abstract

Wettability of alkylated quartz surfaces is of primary importance in several technological applications, including the development of oil and gas reservoirs and carbon geo-sequestration. It is intuitively understood and experimentally confirmed that hydroxylated quartz surfaces are hydrophilic. By gradually saturating a hydroxylated (001) α-quartz surface with pentyl groups, we show using molecular dynamics simulations that the surface can also exhibit extreme hydrophobicity. Within a range of surface pentyl group density from 0.29 to 3.18/nm2, the contact angle of a water droplet under 10 MPa pressure of carbon dioxide at 300 K changes from 10–20 to 180°. This study has shown that a complete description of wettability of alkylated quartz surfaces requires three contact angles—one at the tip level of pentyl groups and two at the level of the quartz surface. The latter two are the contact angle of the spherical droplet and the hidden contact angle of a water “skirt” formed between the tip level of pentyl groups and the quartz surface. Analysis of the hidden contact angle unveils a binary wettability, where the surface relatively abruptly transforms from hydrophilic (the contact angle is less than 90°) to hydrophobic (the contact angle is 180°) with an increase in surface pentyl group concentration.

DOI

10.1021/acs.jpcc.9b00263

Available for download on Saturday, March 14, 2020

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