Loss of volatile organics from kraft filtrates in the evaporation /drying phase of the analysis for dissolved total solids (DTS) and dissolved volatile solids (DVS)

DVS was chosen as the most useful measurement for describing dissolved organic matter to calibrate a bleached kraft process model. The method required careful evaluation because of the extreme variability of the chlorine dioxide bleaching filtrates. Measurements before and after evaporation/drying and redissolution demonstrated that 17-37 per cent of DOC escaped from acid filtrates. Gas chromatography showed alcohols, carboxylic acids, aldehydes and ketones accounted for most of the losses, with methanol and formic acid the most important components. Losses in alkaline bleaching stage filtrates were only 4-9 per cent. The sum of all the identified escaped volatile organics represented 4-5 kg per air dry tonne of bleached pine pulp in the reference process. The carbon content of the identified lost volatiles covered 63 per cent of the escaped DOC.