Adsorption of Aerosol-OT at the calcite/water interface - Comparison of the sodium and calcium salts

Isabella N. Stocker; Kathryn L. Miller; Rebecca J.L. Welbourn; Stuart M. Clarke; Ian R. Collins; Christian Kinane; Philipp Gutfreund

doi:10.1016/j.jcis.2013.11.046

Adsorption of Aerosol-OT at the calcite/water interface - Comparison of the sodium and calcium salts

Isabella N. Stocker, Kathryn L. Miller, Rebecca J.L. Welbourn, Stuart M. Clarke, Ian R. Collins, Christian Kinane, Philipp Gutfreund

Research output: Contribution to journal › Article › peer-review

22 Scopus citations

Abstract

The adsorption of the surfactant Aerosol-OT (AOT) at the calcite-water interface has been investigated using batch adsorption isotherms and neutron reflection. The adsorption isotherms showed that NaAOT adsorption followed S-type adsorption behaviour with a maximum surface excess of 2.5mgm^-2 but the method could not be used for the investigation of Ca(AOT)₂ adsorption owing to the changes in the bulk phase behaviour of the solution. The surface excess, determined by neutron reflection at the critical micelle concentration (CMC), was 2.5mgm^-2 for Ca(AOT)₂ and 1.8mgm^-2 for NaAOT. The time dependence of the NaAOT adsorption suggests a slow conversion from the sodium to the calcium salt of AOT at the calcite-water interface by binding calcium ions released from the slightly soluble calcite. The layer thickness in both cases was 35Å which indicates adsorption as bilayers or distorted micelles. At higher concentrations of NaAOT (~10× CMC) adsorption of an AOT lamellar phase was evident from Bragg peaks in the specular reflection.To our knowledge, this is the first time that adsorption of a surfactant at the calcite-water interface has been investigated by neutron reflection. The technique provided significant new insight into the adsorption behaviour of AOT which would not have been accessible using traditional techniques.

Original language	English
Pages (from-to)	140-146
Number of pages	7
Journal	Journal of Colloid and Interface Science
Volume	418
DOIs	https://doi.org/10.1016/j.jcis.2013.11.046
State	Published - Mar 5 2014
Externally published	Yes

Funding

We thank BP plc. for financial support for this work, the ILL and ISIS staff and scientists for the allocation of beam time (RB920098, 9-12-257) and technical assistance with NR measurements.

Funders	Funder number
BP plc.
ILL
ISIS	9-12-257, RB920098

Keywords

Aerosol-OT
AOT
Calcite
Calcium carbonate
Neutron reflection

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title = "Adsorption of Aerosol-OT at the calcite/water interface - Comparison of the sodium and calcium salts",

abstract = "The adsorption of the surfactant Aerosol-OT (AOT) at the calcite-water interface has been investigated using batch adsorption isotherms and neutron reflection. The adsorption isotherms showed that NaAOT adsorption followed S-type adsorption behaviour with a maximum surface excess of 2.5mgm-2 but the method could not be used for the investigation of Ca(AOT)2 adsorption owing to the changes in the bulk phase behaviour of the solution. The surface excess, determined by neutron reflection at the critical micelle concentration (CMC), was 2.5mgm-2 for Ca(AOT)2 and 1.8mgm-2 for NaAOT. The time dependence of the NaAOT adsorption suggests a slow conversion from the sodium to the calcium salt of AOT at the calcite-water interface by binding calcium ions released from the slightly soluble calcite. The layer thickness in both cases was 35{\AA} which indicates adsorption as bilayers or distorted micelles. At higher concentrations of NaAOT (~10× CMC) adsorption of an AOT lamellar phase was evident from Bragg peaks in the specular reflection.To our knowledge, this is the first time that adsorption of a surfactant at the calcite-water interface has been investigated by neutron reflection. The technique provided significant new insight into the adsorption behaviour of AOT which would not have been accessible using traditional techniques.",

keywords = "Aerosol-OT, AOT, Calcite, Calcium carbonate, Neutron reflection",

author = "Stocker, {Isabella N.} and Miller, {Kathryn L.} and Welbourn, {Rebecca J.L.} and Clarke, {Stuart M.} and Collins, {Ian R.} and Christian Kinane and Philipp Gutfreund",

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AU - Stocker, Isabella N.

AU - Miller, Kathryn L.

AU - Welbourn, Rebecca J.L.

AU - Clarke, Stuart M.

AU - Collins, Ian R.

AU - Kinane, Christian

AU - Gutfreund, Philipp

PY - 2014/3/5

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N2 - The adsorption of the surfactant Aerosol-OT (AOT) at the calcite-water interface has been investigated using batch adsorption isotherms and neutron reflection. The adsorption isotherms showed that NaAOT adsorption followed S-type adsorption behaviour with a maximum surface excess of 2.5mgm-2 but the method could not be used for the investigation of Ca(AOT)2 adsorption owing to the changes in the bulk phase behaviour of the solution. The surface excess, determined by neutron reflection at the critical micelle concentration (CMC), was 2.5mgm-2 for Ca(AOT)2 and 1.8mgm-2 for NaAOT. The time dependence of the NaAOT adsorption suggests a slow conversion from the sodium to the calcium salt of AOT at the calcite-water interface by binding calcium ions released from the slightly soluble calcite. The layer thickness in both cases was 35Å which indicates adsorption as bilayers or distorted micelles. At higher concentrations of NaAOT (~10× CMC) adsorption of an AOT lamellar phase was evident from Bragg peaks in the specular reflection.To our knowledge, this is the first time that adsorption of a surfactant at the calcite-water interface has been investigated by neutron reflection. The technique provided significant new insight into the adsorption behaviour of AOT which would not have been accessible using traditional techniques.

AB - The adsorption of the surfactant Aerosol-OT (AOT) at the calcite-water interface has been investigated using batch adsorption isotherms and neutron reflection. The adsorption isotherms showed that NaAOT adsorption followed S-type adsorption behaviour with a maximum surface excess of 2.5mgm-2 but the method could not be used for the investigation of Ca(AOT)2 adsorption owing to the changes in the bulk phase behaviour of the solution. The surface excess, determined by neutron reflection at the critical micelle concentration (CMC), was 2.5mgm-2 for Ca(AOT)2 and 1.8mgm-2 for NaAOT. The time dependence of the NaAOT adsorption suggests a slow conversion from the sodium to the calcium salt of AOT at the calcite-water interface by binding calcium ions released from the slightly soluble calcite. The layer thickness in both cases was 35Å which indicates adsorption as bilayers or distorted micelles. At higher concentrations of NaAOT (~10× CMC) adsorption of an AOT lamellar phase was evident from Bragg peaks in the specular reflection.To our knowledge, this is the first time that adsorption of a surfactant at the calcite-water interface has been investigated by neutron reflection. The technique provided significant new insight into the adsorption behaviour of AOT which would not have been accessible using traditional techniques.

KW - Aerosol-OT

KW - AOT

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KW - Calcium carbonate

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JO - Journal of Colloid and Interface Science

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ER -

Adsorption of Aerosol-OT at the calcite/water interface - Comparison of the sodium and calcium salts

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