Sorption properties of activated carbon derived from used paper and of amorphous 2CaO·Al₂O₃·2SiO₂ from paper sludge ash

Two materials with highly functional sorption properties were prepared from used paper and the paper sludge generated as a by-product of the process of paper production. Activated carbon can be prepared either by chemical activation using various chemical agents or by physical activation using steam. The chemically activated carbons show better porous properties than those obtained by physical activation. The activated carbon prepared using K₂CO ₃ showed the highest specific surface area of about 1700 m ²/g. This activated carbon showed very steep water vapour adsorption at 50 to 70% relative humidity with a maximum adsorption of >1000 ml/g. It also showed superior adsorption of methylene blue dye from solution. These adsorption properties make it a candidate material for humidity control and as a water purifying agent. An amorphous substance with 2CaO·Al ₂O₃·2SiO₂ composition was prepared by mechanochemical and heat treatment of paper sludge at 500-800°C. Since these materials consist of three components with different chemical properties, they are able to take up heavy metal cations, NH₄⁺ and PO ₄^3- ions, which are principally implicated in the eutrophication of lakes and ponds. Amorphous 2CaO·Al₂O ₃·2SiO₂ obtained from paper sludge is therefore a candidate water purifying material and also has potential for soil recovery applications.