The degrading action of iron and copper on paper - A FTIR-deconvolution analysis

Samples of FeCl3 and CuCl2 treated cellulose paper were analysed by FTIR before and after accelerated ageing at 90±10°C (sealed tube technique). The main mechanism of Fe(III) degradation appeared to be a strong hydrolysis and dehydration of cellulose chains, with formation of a C4-C5 double bond, and C6 oxidation. Cu(II) oxidized the C2-and C3-OH groups to aldehydes and carboxyls, thus opening the pyranose ring, and hydrolyses and oxidized the C4-OR group with the formation of a C4-C6 β-ketoaldehyde or β ketoacid. Among the FTIR-deconvolution bands in the 1250-1850 cm-1 region, the ∼ 1660 cm-1 signal is attributed to the unsaturated C=C-CO, and the 1612-1622 cm-1 signal to CO-C-CO group (chelate form of the enol tautomer). These bands, which can only be detected by the deconvolution technique, appear more significant than those of unconjugated CO groups above 1700 cm-1.