Effects of Additives on Absorbable Organic Halide Reduction in Elemental Chlorine-Free Bleaching of Bagasse Kraft Pulp

In order to further reduce absorbable organic halide (AOX) formation in the bleaching effluent, NH2SO3H and DMSO were added during the elemental chlorine-free (ECF) bleaching (D0EpD1) of bagasse kraft pulp. In the D-0 stage, AOX formation decreased by 10% with 0.1% NH2SO3H, and a reduction of 11.2% with 1.0% DMSO, respectively. Ultraviolet (UV) spectra, Fourier transform infrared spectroscopy (FTIR), and gas chromatography-mass spectroscopy (GC-MS) were adopted in characterizing changes of lignin degradation and the main functional groups of bleached pulp. The UV spectrum showed that the quantity of polyphenols decreased after adding the additives. The FTIR spectrum showed that both the content of phenolic-type lignin and the degradation degree of lilac-type lignin decreased after adding NH2SO3H. If was found that DMSO was beneficial in retaining C-O-C and C=O structures in cellulose and hemicellulose, while NH2SO3H decreased the content of beta-glycosidic bonds and C-O-C structures in cellulose and hemicellulose. The composition of lignin degradation products in the bleaching effluent was analyzed by GC-MS. The contents of chlorobenzene and chlorophenol decreased notably when additives were added. Compared with DMSO, NH2SO3H exhibited poor inhibition on the formation of some phenols.