Multi functional uptake behaviour of materials prepared by calcining waste paper sludge

This study concerns with the utilization of waste paper sludge, which contains mainly cellulose fibers and inorganic fillers together with coating materials such as calcite, kaolinite and talc. Paper sludge was fired at 500-900°C for 6 h. The crystalline phases originally present decomposed at increasing temperatures (up to 800°C) in the order kaolinite < calcite < talc. Gehlenite was formed at 800°C in increasing amounts above this temperature together with small amounts of magnesium aluminum silicate and anorthite. The uptake of these fired samples of Ni²⁺, PO ₄^3- and NH₄⁺ was investigated at room temperature. Paper sludge fired at 700°C showed the highest uptake of Ni²⁺, PO₄^3- and NH₄^- (3.93, 1.28 and 0.49 mmol/g, respectively). The main process responsible for the sorption of these ions is the ion change along with precipitation with higher solution pH. From an economic point of view, paper sludge is the cheapest raw material for preparing adsorbents with high uptake ability for heavy metal, phosphate and ammonium ions.