Adsorption from Dextran solutions: influence of stainless steel substrates

Abstract The present work concerns the adsorption of Dextran from pure water or scaling water solutions on various substrates. Three types of 304 2R stainless steel substrates have been investigated having respectively hydrophilic properties (argon plasma treatment), weakly hydrophobic (weakly contaminated) and pronounced hydrophobic properties (covered by an hydrophobic layer). Measurements of interfacial tension and contact angles evolution in the various situations were used to calculate the Dextran adsorptions. In case of pure Millipore ® water a standard behaviour has been observed: the Dextran adsorption was found to increase with: • The hydrophobic character of the substrate (starting from negative values on hydrophilic substrate to positive values on hydrophobic substrate). • The concentration of Dextran of the polymer solution. On the contrary, in the case of scaling water solution (i.e. water containing salts and carbonate ions), the Dextran adsorption was found to be very important on the hydrophilic substrate. This behaviour was attributed to a non-equilibrium situation induced by the presence of ions in water. A thermodynamic analysis of the calculated values of the Gibbs adsorption allows extracting structural information, in particular on the size of the adsorbed train. In the present case, this analysis has confirmed the non-equilibrium character of the Dextran adsorption from scaling water solution on hydrophilic substrate.