Surface chemistry of deinked pulps as analysed by XPS and ToF-SIMS

The surface chemistry of recycled deinked pulps made from old newspaper (ONP) and mixed office waste (MOW) was investigated by XPS and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The short and the long fibre fractions of the pulps were separated and their differences in surface chemistry were assessed. The amount of surface anionic groups (SAG) and the surface coverage by carbohydrates, lignin and extractives were calculated from the XPS measurements. Metal traces were observed on feed pulps and the fines fractions of both ONP and MOW, some of them exposed after extraction. Only fines of ONP showed a quantifiable amount of surface extractives. The amount of surface lignin did not differ significantly between the ONP fractions. The method presented high values of surface lignin on MOW, especially fines fraction, which was considered, in fact, a measure of other surface contamination. There were no remarkable differences between the SAGs in the different fractions. Residual chemicals from paper converting, printing and deinking were detected on the fibre surfaces by ToF-SIMS spectrometry. The distributions of trace metals (e.g. Fe, Al and Mg), pulp components and some common contaminants were assessed using ToF-SIMS imaging. It was discovered that the fibre surfaces were covered by patchy ink residuals at raster sizes of 200 pm x 200 pm. A uniform layer of siloxanes and phthalates was also detected on every sample. The residual paper and printing chemicals can affect interactions in papermaking and reduce the fibre-to-fibre bonds in the recycled paper. Copyright (C) 2010 John Wiley & Sons, Ltd.