Adsorption Mechanism of Lignosulfonate at the Air/Liquid Interface

Lignosulfonate is a type of natural polymer surfactant. Its capability to reduce the surface tension of aqueous solution depends on its adsorption configuration at the air/liquid interface. The dynamic surface tension, the air/liquid interfacial film properties of lignosulfonate at different solution concentrations, pH values and ionic strengths had been measured in the present work. The results showed that the adsorption equilibrium of lignosulfonate at the air/liquid cannot be achieved in a short period; the diffusion coefficient of lignosulfonate from the liquid to the air/liquid interface decreased with the increasing of pH value, while it increased with the increasing of ionic strength. Lignosulfonate could form soluble monomolecular film at the air/liquid interface, whereas the film was unstable. The stability of lignosulfonate monomolecular film became poor with the increasing of solution concentration, ionic strength and decreasing of pH value. Combining with our previous research results, the adsorption mechanism of lignosulfonate at the air/liquid interface was proposed.