Calorimetric Methods for the Study of Adsorption of Surfactants at Solid/Solution Interfaces

ZOLTA´ N KIRA´ LY Department of Colloid Chemistry, University of Szeged, Szeged, Hungary

I. Introduction 335

II. Classification of Calorimeters 336 A. Isotherm power compensation calorimetry 337 B. Isoperibolic heat flux calorimetry 338

III. Enthalpies of Displacement Obtained with Different Microcalorimetric Methods 339 A. Definition of the enthalpy of displacement 340 B. Immersion microcalorimetry 341 C. Batch sorption microcalorimetry 343 D. Titration sorption microcalorimetry 344 E. Flow sorption microcalorimetry 346 F. Noncalorimetric enthalpies of displacement 349

IV. Literature Survey on Calorimetric Studies of Surfactant Adsorption on Solid Substrates 350

References 354

I. INTRODUCTION The adsorption of surfactants at solid/solution interfaces has long been the subject of extensive experimental and theoretical research. Various aspects have been addressed, among them the composition and structure of the adsorption layer, the mechanism of the adsorption (different stages), the kinetics, the thermodynamics

(driving force), the nature of the solid surface (charged, uncharged, hydrophilic, hydrophobic, modifications, roughness, porosity), the nature of the surfactant (ionic, nonionic, HLB number, chain length, headgroup effect, stereochemistry), and experimental conditions (pH, temperature, salinity).