TY - JOUR A1 - Hartmann, A. A1 - Petrov, V. A1 - Buhl, J.-C. A1 - Rübner, Katrin A1 - Lindemann, Mathias T1 - Digestion reactions of paper sludge combustion ash in strong alkaline solutions at 60 °C N2 - Alkaline reactions of paper sludge combustion ash at low temperature (60 °C) were performed using a calcite-rich paper ash (PA 1) and a gehlenite-rich ash (PA 2). Strong alkaline conditions (8, 12, 16 M NaOH) were revealed at reaction times of 1–4 h and 12–24 h. Reactions were performed with pure ashes and in the presence of NaAlO2. The products were characterized by XRD, FTIR, SEM/EDX, gravimetry and chemical analysis. The conversion was found to proceed mainly in the period between 1 and 4 h. Portlandite and hydrogarnet were observed from PA 1 in 8 M NaOH. Onset of formation of Ca4Al2O6CO·311H2O beside Ca(OH)2 could be analyzed after reaction of PA 1 in 12 M and 16 M NaOH. Addition of NaAlO2 favored crystallization of hydrogarnet and Ca4-Al2O6CO·311H2O. For PA 2 gehlenite remained stable, but a high portlandite fraction was observed. Addition of NaAlO2 yielded hydrogarnet beside gehlenite in 8 M NaOH. Higher alkalinities favored crystallization of Ca4Al2O6-CO·311H2O and onset of dissolution of gehlenite. Finally transformation of Ca4Al2O6CO·311H2O into sodium aluminum silicate hydrate was observed. All results were discussed with regard to heavy metal distribution of the initial PA between the alkaline digestion solution and the products. In conclusion suitable applications of the products were proposed. KW - Paper sludge combustion ash KW - Alkaline digestion reaction KW - Portlandite KW - Katoite KW - Zeolite PY - 2016 U6 - https://doi.org/10.1007/s10163-014-0320-4 SN - 1438-4957 SN - 1611-8227 VL - 18 IS - 1 SP - 132 EP - 145 PB - Springer CY - Tokyo AN - OPUS4-32827 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -