Degradation of cellulosic materials under the alkaline conditions of a cementitious repository for low and intermediate level radioactive waste: Part I: Identification of degradation products

Abstract

In order to assess the potential role of cellulose degradation products as metal-binding chelates in a repository for radioactive waste, different cellulosic materials (pure cellulose, cotton, tissues and recycling paper) were degraded under the chemical conditions of cement pore water (pH 13.3). The degradation products formed were characterised using different separation techniques (HPIEC, HPAEC, GC-MS, MS/MS) and by high resolution 1H-NMR spectroscopy. The main degradation products of pure cellulose are the diastereomeric α-isosaccharinic acid (α-ISA) and β-isosaccharinic acid (β-ISA), which accounted for ∼80% of total dissolved organic carbon formed. Minor components are short chain aliphatic acids such as formic acid, acetic acid, lactic acid and threonic acid comprising less than 10% of total dissolved organic carbon. The degradation of the other cellulosic materials resulted in lower amounts of α-ISA and β-ISA and in higher yields of small organic acids (acetic acid) and of unidentified compounds. The combination of the different MS and NMR techniques unequivocally shows the structural identity of β-ISA.