Characterization of effluents from TCF bleaching of softwood kraft pulp

Organic material dissolved during the different stages of a totally chlorine-free (TCF) mill-scale bleaching of pine (Pinus sylvestris) kraft pulp was characterized. The TCF bleach sequence was XZ(EOP)(AZ)(EP)S. the amount of carbohydrates, lignin, carboxylic acids, and total organic carbon (TOC) varied in the liquor samples from each stage in the range 0.5-3.8, 0.1-2.8, <0.1-5.7, and 0.6-11.7 kg/air-dry ton of bleached pulp, respectively. The high content of xylose moieties in dissolved carbohydrates indicated that xylan fragments were the major hemicellulose constituents present. The most abundant aliphatic carboxylic acids were formic, acetic, glycolic, and 3-hydroxypropanoic acids.