Preparation of Modified Kaolin Filler with Cesium and Its Application in Security Paper.

In this study, cesiumwas added intentionally during paper manufacture for protecting the papers against forgery and counterfeiting by sorbing cesium ions (Cs+) on kaolin, used as special filler in papermaking. The sorption of cesium from aqueous solution by kaolin was studied as a function of pH, shaking time, cesium initial concentration, and mass of kaolin using batch technique. The results showed that a solution containing 10mg/L Cs+ and 250mg of kaolin at pH 6 can be used to modify the kaolin. Paper hand sheets were prepared containing various percentages of the modified kaolin. The mechanical and optical properties of paper hand sheets were studied. The prepared paper hand sheets were irradiated by gamma irradiation using different doses. Fourier transform infrared (FTIR) spectroscopy was used to study the effect of kaolin modification by cesium and gamma irradiation on paper hand sheets properties. The results indicated that modified kaolin enhanced the mechanical and optical properties of paper hand sheets. Electron spin resonance (ESR) spectroscopy and laser-induced breakdown spectroscopy (LIBS) were also used. They provided rapid, sensitive and nondestructive techniques in differentiating between different questioned documents. This study presents a new concept in manufacturing security papers and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]