Competitive adsorption between SDS and carbonate on tetrahydrofuran hydrates

Sodium dodecyl sulfate (SDS) has been well known as a promoter for the formation of hydrates. However, the use of SDS to enhance the formation of CO2 hydrates has not been effective. This work will present an idea of competitive adsorption that will provide insights into the nonpromoting effect of SIDS under high carbonate concentrations. The competitive adsorption is studied between DS- monomers and carbonate ions on tetrahydrofuran (THF) hydrates. The adsorption is qualitatively investigated by using pyrene fluorescence measurements. The SDS concentration at which hydrophobic domains occur on the hydrate surface increases with the increased carbonate concentration and this trend is less dependent on the order of addition of these two species. This concentration is 0.17 mM at carbonate concentrations less than 2 mu M and it shifts to 3.47 mM at carbonate concentrations higher than 2.5 mu M. Thus, using carbonate with its concentration higher than 2.5 mu M would be enough to displace the hydrophobic domains formed by SIDS up to the solubility limit. (C) 2009 Elsevier Inc. All rights reserved.