Production and characterization of a novel lignin-based biopolymer from Ulex europaeus

Abstract

Invasive plant species are a global environmental threat since they affect native species and may modify ecosystems, which negatively impact human health and world economics. The aim of this study was to synthesize and characterize a new lignin-based biopolymer from gorse (Ulex europaeus), a globally widespread invasive plant. The lignin extraction was carried out through acid-base and solvent-based methodologies to compare the reaction yield. Subsequent polymerization of the extracted lignin was performed by glycine condensation in a 70% 1,4-dioxane solution with H2O2 and CaCl2 as catalysts. The extraction and polymerization products were characterized by Fourier-transform infrared spectroscopy. Thermal and stability properties of the new biopolymer were determined by thermogravimetric analysis, differential scanning calorimetry, and analysis of biodegradation rate. The alkaline extraction process of lignin resulted in higher yield than the one by organic solvent. In comparison to the extracted lignin, the novel biopolymer showed differently absorption bands that are characteristic of tensions and flexions of alkenes, amine, and amide groups. Additionally, thermal properties revealed peaks corresponding to decomposition and dehydration reactions, endothermic processes and a melting point of 258.71°C. Total biodegradation was reached after ten hours. A new polymeric, possibly cross-linked, thermally stable material with a potentially high degree of crystallinity was synthesized from a renewable raw material, which might contribute to the gorse management according to the concept of novel ecosystem, besides the reduction in contamination by other polymeric materials.