STUDIES ON ADSORPTION BEHAVIOR OF SULFONATE SURFACTANTS ON A LEAD ELECTRODE IN SULFURIC-ACID

The electrochemical behavior of a lead electrode was studied in 5 M su lfuric acid with various sulfonate surfactants, viz. amine perfluoroit lkylsulfonate (FC-99), sodium dodecylbenzenesulfonate (SDBS) and sodiu m lignosulfonate (SLS), and also in relation to the structural charact eristics and the adsorption state of the additives on different surfac es of the electrodes. The results indicate that FC-99 molecules adsorb on the metallic lead surface by their hydrophilic heads whereas they adsorb on lead sulfate by their hydrophobic chains vertically, but the SDBS molecules adsorb on metallic lead and lead sulfate flat or partl y flat, with their hydrophilic heads oriented toward the electrode. Fo r SLS, the adsorption state is different from those of the other two s urfactants. At lower concentrations (similar to 5 ppm), the SLS molecu les adsorb on the metallic lead and lead sulfate with a partly flat or ientation by their sulfonate groups, just as SDBS molecules do. At hig her concentrations (greater than or equal to 10 ppm), the SLS molecule s adsorb on the lead and lead sulfate perpendicularly with their hydro philic heads oriented toward the bulk solution.