Retention of silica nanoparticles on calcium carbonate sands immersed in electrolyte solutions

Type
Article

Authors
Li, Yan Vivian
Cathles, Lawrence M.

KAUST Grant Number
KUS-C1-018-02

Date
2014-12

Abstract
© 2014 Elsevier Inc. Understanding nanoparticle-surface adhesion is necessary to develop inert tracers for subsurface applications. Here we show that nanoparticles with neutral surface charge may make the best subsurface tracers, and that it may be possible to used SiO2 nanoparticle retention to measure the fraction of solid surface that has positive charge. We show that silica nanoparticles dispersed in NaCl electrolyte solutions are increasingly retained in calcium carbonate (calcite) sand-packed columns as the solution ionic strength increases, but are not retained if they are injected in pure water or Na2SO4 electrolyte solutions. The particles retained in the NaCl experiments are released when the column is flushed with pure water or Na2SO4 solution. AFM measurements on calcite immersed in NaCl solutions show the initial repulsion of a silica colloidal probe as the surface is approached is reduced as the solution ionic strength increases, and that at high ionic strengths it disappears entirely and only attraction remains. These AFM measurements and their interpretation with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory shows the calcite surface charge is always negative for Na2SO4 solutions, but changes from negative to positive in a patchy fashion as the ionic strength of the NaCl solution increases. Since mixed-charge (patchy) surfaces may be common in the subsurface, nanoparticles with near-zero charge may make the best tracers.

Citation
Li YV, Cathles LM (2014) Retention of silica nanoparticles on calcium carbonate sands immersed in electrolyte solutions. Journal of Colloid and Interface Science 436: 1–8. Available: http://dx.doi.org/10.1016/j.jcis.2014.08.072.

Acknowledgements
This publication is based on work supported by Aramco Services Company (Project ID: ASC #660022190) and by Award No. KUS-C1-018-02 from the King Abdullah University of Science and Technology. Support was also provided by a general fund contribution to L. Cathles from The International Research Institute of Stavanger. The authors appreciate Prof. Tracy Bank at SUNY at Buffalo for her priceless discussion on DLVO modeling.

Publisher
Elsevier BV

Journal
Journal of Colloid and Interface Science

DOI
10.1016/j.jcis.2014.08.072

PubMed ID
25259754

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