The impact of methanol-based by-products in chlorine dioxide solution on pulp bleaching

Studies were carried out to determine the fate and effects of the methanol- based byproducts formed during the generation of chlorine dioxide, when tha t ClO2 solution is used for pulp bleaching. It was found that the methanol and formic acid in the ClO2 solution had no effect on delignification effic iency or AOX formation in the first two bleaching stages (DE). The methanol formed by lignin degradation in the both the D0- and E1-stages is signific antly higher than that added with the ClO2 solution. Formic acid is neither created nor destroyed during pulp bleaching delignification. The addition of methanol and formic acid to ClO2 solution produced mixed results with re gard to the BOD5 test. However, even in those experiments where the additio n of methanol and/or formic acid appeared to increase the bleach plant BOD5 load, the results did not follow expected trends, and the changes were not statistically significant.