Aggregation and adsorption behaviors of carboxymethylated lignin (CML) in aqueous solution

Carboxymethylated lignin (CML) as a water-soluble lignin derivative is a multipurpose adsorbent and dispersant. In this article, the aggregation and adsorption behaviors of CML have been investigated in aqueous solution using fluorescence spectroscopy, dynamic light scattering, and a quartz crystal microbalance combined with dissipation monitoring techniques. It was found that CML forms aggregates when its concentration exceeds the critical aggregation concentration (CAC). The CAC of CML1 with a carboxylic (COOH) group content of 2.8 mmol g(-1) was 0.022 g l(-1), and that of CML2 with a COOH group content of 2.0 mmol g(-1) was 0.026 g l(-1). The adsorption behavior of CML on the gold surface was strongly dependent on the pH and ionic strength of the solution. At low pH and ionic strength, more CMLs were adsorbed at the gold/water interface, and the layers were rigid. The results could be used not only from the theoretical but also from the application point of view.