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Langmuir films of naphthenic acids at different pH and electrolyte concentrations |
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| Authors: | Trond Havre Marit-Helen Ese Johan Sjöblom Anne Blokhus |
| Institution: | Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway, Department of Chemical Engineering, North Carolina State University, Raleigh, NC 27695-7905, USA, Department of Chemistry, University of Bergen, 5007 Bergen, Norway, |
| Abstract: | Langmuir films of naphthenic acids at different pH and electrolyte concentrations are reported. The polydisperse naphthenic acids were commercially available, while two single-component naphthenic acids 5#(H)-cholanoic acid and 1-naphthalenepentanoic acid, decahydro- (9CI)] were synthesized. 1-naphthalenepentanoic acid, decahydro- is too water-soluble to form stable monolayers. 5#(H)-Cholanoic acid and Fluka naphthenic acid form stable films when cations are present in the aqueous subphase. At lower pH the cations are less influential since the naphthenic acids are not protolysed and metal naphthenates cannot be formed. pKas for 5#(H)-cholanoic acid is determined to 5.65. The micellisation of the naphthenates at high pH is described. |
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