Oxidative degradation of non-recycled and recycled paper
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ORIGINAL RESEARCH
Oxidative degradation of non-recycled and recycled paper Floriana Coppola
. Alberto Modelli
Received: 13 May 2020 / Accepted: 10 August 2020 Ó The Author(s) 2020
Abstract 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 nonrecycled 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 nonrecycled papers being found to be higher than those of the recycled papers.
F. Coppola (&) A. Modelli Dipartimento di Chimica ‘‘G. Ciamician’’, Universita` di Bologna, via Selmi 2, 40126 Bologna, Italy e-mail: [email protected] A. Modelli Centro Interdipartimentale di Ricerca in Scienze Ambientali, via S. Alberto 163, 48123 Ravenna, Italy
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Cellulose
Graphic abstract
Keywords Periodate oxidation of paper Recycled paper Carbonyl content Degree of polymerisation
Introduction Technologies and raw materials for papermaking have radically changed over the centuries (Hunter 1978). While around 1850 wood fibres (softwood and hardwood) started being used to manage the ever-increasing demand for paper and deficiency of rag fibres, currently a growing part of paper manufacturing involves recycled fibres due to economic and environmental issues (CEPI 2017). The 2018 monitoring report published in the context of the European Declaration on Paper Recycling 2016–2020 outlines that the recycling rate in Europe reached 71.6% in 2018, increasing by 47% since 1998 (EPRC 2019). Unlike the well-studied Western historical paper for which significant research has been carried out over the past decades, scientific research on contemporary recycled paper is quite limited. It has previously been reported (Coppola et al. 2018a) that accelerated degradation experiments, carried out exposing recycled and non-recycled papers
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