Facile synthesis of phenolic hydroxyl-rich modified lignin: Evaluation of their applications as an antioxidant and for Cr(VI) removal

In this study, modified aminated lignin derivatives (MALDs) with high phenolic hydroxyl group contents were prepared via a facile reaction between aminated lignin and 3,4-dihydroxyhydrocinnamic acid. Elemental analysis (EA), 1H- and 31P NMR spectroscopy, zeta potential, Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and X-ray photoelectron spectroscopy (XPS) were hired to characterize the impact of the reaction conditions on the specific structural properties and phenolic hydroxyl group level of the MALDs. The reaction mechanism for the MALDs preparation has been proposed based on this analysis. With a 2,2-diphenyl-1-picrylhydrazyl (DPPH) elimination rate of 89.90% recorded at a concentration of 0.5 mg/L, the testing results demonstrated that MALDs with a high phenolic hydroxyl content (2.71 mmol/g) display excellent antioxidant activity. Furthermore, MALDs exhibited an ultrahigh adsorption capacity for hexavalent chromium ion (Cr(VI)) removal (161.5 mg/g) because of enough active sites available. The use of lignin in the wastewater treatment field is now more feasible as a result of this work.