X-ray absorption and diffraction analysis for determination of the amount of calcium carbonate and porosity in paper sheets

Papers are mostly made with lignocellulose and additives among which calcium carbonate has a primarily importance. Calcium carbonate as a filler provides specific properties to the paper like brightness, porosity, etc. Because of low retention, calcium carbonate remains in large quantities in the waste water when at the final stage, the paper is couched and pressed. It is therefore interesting to develop some methods to analyze in a nondestructive way the content of calcium carbonate that remains in the paper. We report in this article an X-ray study of paper sheets with the aim to determine not only the content of calcium carbonate in a nondestructive way but also the porosity of the paper sheets. The analysis is carried out in a quantitative way by refining the wide angle X-ray diffraction patterns using the Rietveld method and by modeling the absorption of the direct beam through paper sheets.