Surface Modification of Kraft Lignin by Mechanochemical Processing with Sodium Percarbonate

In this article,
we present a novel one-pot mechanochemical reaction
for the surface activation of lignin. The process involves environmentally
friendly oxidation with hydrogen peroxide, depolymerization of fractions
with high molecular mass, and introduction of new carbonyl functions
into the lignin backbone. Kraft lignin was ground with sodium percarbonate
and sodium hydroxide in a ball mill at different time intervals. Analyses
by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy
(NMR), size exclusion chromatography (SEC), dynamic vapor sorption
(DVS), and small-angle X-ray scattering (SAXS) showed significant
improvements. After only 5 min of reaction, there was a 47% reduction
in mass-average molecular weight and an increase in carboxyl functionalities.
Chemical activation resulted in an approximately 2.8-fold increase
in water adsorption. Principal component analysis (PCA) provided further
insight into the correlations between IR spectra and SAXS parameters.