Chemical Treatment of Lignosulfonates Under DBD Plasma Conditions. I. Spectral Characterization

A new method for chemical modification of lignin product under dielectric barrier discharge (DBD) plasma at atmospheric pressure is proposed. The motivation of this study is to obtain from ammonium lignosulfonate powder (ALS) and carboxylic acids (oleic acid, OA and lactic acid, LA) and butyrolactone (BL), new products with improved functionalities (ALS-LA, ALS-OA and ALS-BL), which may be used in manufacturing of biocomposite materials. The chemical transformations on the surface of ALS were evaluated by elemental analysis, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), near-infrared (NIR) spectroscopy and near-infrared chemical imaging (NIR-CI), as well as nuclear magnetic resonance (1H-NMR and 13C-NMR), UV–VIS and fluorescence spectroscopies. The attachment of the monomeric chains to the macromolecular network of ALS was proved by the values of atomic ratios (C/H, C/O and O/C), calculated from elemental analysis, reveal. The spectral results confirmed that the grafting reaction of ammonium lignosulfonate took place under cold plasma conditions and various compounds with special structures and functionalities have been obtained. Moreover, the recorded NIR-CI images (RGB and PCA components) provide information about ALS product homogeneity.