Oxidative degradation of non-recycled and recycled paper

The degradation of paper-based materials involves several and complex mechanisms, such as hydrolysis and oxidation. The behaviour of different types of pulps can be very variable. In this study, the difference upon oxidation of contemporary non-recycled and recycled papers, which now constitute a considerable fibre source, is investigated. A 0.015 M potassium periodate solution is used to oxidise five types of paper, two non-recycled and three recycled, for 0.5, 1, 2 and 4 h. The effects of such oxidation treatments are evaluated in terms of carbonyl content and degree of polymerisation (DP). A modified procedure of the Szabolcs’s method and viscometry are used to measure the carbonyl content and DP, respectively. The carbonyl groups are found to increase more rapidly in the recycled papers than in the non-recycled ones. On the contrary, oxidation causes a larger decrease of the DP values in the non-recycled papers, the paper made of pure cellulose being the most sensitive in terms of depolymerisation. The DP values measured for pure cellulose paper are in line with previously reported data. Moreover, in accordance with the Ekenstam equation, the plots of the reciprocal of DP as a function of oxidation time show good linear correlations for all types of paper investigated. Pseudo rate constants are thus calculated from the slopes of these plots, those of the non-recycled papers being found to be higher than those of the recycled papers. Graphic abstract: [Figure not available: see fulltext.].