Interaction of NaOH solutions with silica surfaces

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:516

Article

Rimsza, J. M.¹  Jones, R. E.²  Criscenti, L. J.¹ 

[1] Sandia Natl Labs, Geochem Dept, POB 5800, Albuquerque, NM 87185 USA

[2] Sandia Natl Labs, Sci Based Mat Modeling Dept, Livermore, CA 94551 USA

关键词: Adsorption;    Silica;    Molecular simulations;    NaOH;    Molecular dynamics;   

DOI  :  10.1016/j.jcis.2018.01.049

来源: Elsevier

【 摘 要 】

Hypothesis: Sodium adsorption on silica surfaces depends on the solution counter-ion. Here, we use NaOH solutions to investigate basic environments. Simulations: Sodium adsorption on hydroxylated silica surfaces from NaOH solutions were investigated through molecular dynamics with a dissociative force field, allowing for the development of secondary molecular species. Findings: Across the NaOH concentrations (0.01 M 1.0 M) similar to 50% of the Na+ ions were concentrated in the surface region, developing silica surface charges between -0.01 C/m(2) (0.01 M NaOH) and -0.76 C/m(2) (1.0 M NaOH) due to surface site deprotonation. Five inner-sphere adsorption complexes were identified, including monodentate, bidentate, and tridentate configurations and two additional structures, with Na+ ions coordinated by bridging oxygen and hydroxyl groups or water molecules. Coordination of Na+ ions by bridging oxygen atoms indicates partial or complete incorporation of Na+ ions into the silica surface. Residence time analysis identified that Na+ ions coordinated by bridging oxygen atoms stayed adsorbed onto the surface four times longer than the mono/bi/tridentate species, indicating formation of relatively stable and persistent Na+ ion adsorption structures. Such inner-sphere complexes form only at NaOH concentrations of > 0.5 M. Na+ adsorption and lifetimes have implications for the stability of silica surfaces. (C) 2018 Elsevier Inc. All rights reserved.

【 授权许可】

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