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.木质素磺酸盐（Lignosulfonate）是一类天然高分子表面活性剂。其降低水溶液表面张力的能力，取决于它在气/液界面的吸附构型。本研究测定了不同溶液浓度、pH值与离子强度下，木质素磺酸盐的动态表面张力及其气/液界面膜性质。结果表明，木质素磺酸盐无法在短时间内达到气/液界面的吸附平衡；其从体相溶液向气/液界面扩散的扩散系数随pH值升高而降低，随离子强度升高而增大。木质素磺酸盐可在气/液界面形成可溶性单分子膜，但该膜稳定性较差。木质素磺酸盐单分子膜的稳定性会随溶液浓度、离子强度升高以及pH值降低而变差。结合本团队前期研究成果，本研究提出了木质素磺酸盐在气/液界面的吸附机理。