(319a) Synthesis and Characterization of Water-Soluble Anionic Carboxylic Acid-Terminated Lignin Dendrimer for Metal Chelating

The preparation of high-value and functional materials from renewable and low-cost biowaste (e.g. lignin) has been attracted a lot of interest. Lignin is an aromatic polymer that has usually been reclaimed from biorefinery waste stream. In this study, we aim to synthesize a water-soluble anionic dendrimer starting from lignin, and explore its capabilities for copper chelating. It is known that water-soluble anionic dendrimer has great potential as mimics of anionic micelles or proteins, EDTA similarities, and chelating agents for a spectrum of applications in catalyst, drug delivery, gene transfer, wastewater treatment, and micronutrients. Herein, a water-soluble carboxylic acid-terminated lignin dendrimer structure (LDCA) was successfully synthesized from lignin dendrimer via butyl ester termination approach. At first, the water-soluble lignin-based dendrimeric structure was firstly prepared from the commercial sodium lignosulfonate (LS) through grafting with the epoxy group which was reacted with amines. Then carboxylic acid groups were added as the end group prepared from neutralized lignin-NH₃⁺ and t-butyl acrylate. The ¹H-NMR and FTIR characterization confirms the successful grafting of functional groups and the synthesis of lignin-based dendrimer and LDCA. Furthermore, the absorption of Cu (II) ion on the anionic LDCA complex was under investigation and the results from the FTIR and SEM demonstrate the binding of Cu²⁺on the complex. The adsorption batch experiment was measured through an ultrafiltration method in the pH range of 3-9 as well as several ratio of metal ions and LDCA. The binding equilibrium was also analyzed by potentiometric titration combined with Isothermal titration calorimetry (ITC) which could fit a complexation binding model.