Abstract
Al-substituted tobermorite has been successfully synthesized by hydrothermal treatment at 180°C in the presence of NaOH solution, using waste incineration fly ash as a starting material, pretreated with repeatedly washing and heating at 800°C. The relation between Al-substituted tobermorite yield and synthetic conditions has been also examined. The pretreatment was essential to convert fly ash into Al-substituted tobermorite with reproducibility, and the Al-substituted tobermorite yield was found to reach a maximum in the fly ash treated with 2M (mol·dm-3) NaOH for 20-30h. The order of Al-substituted tobermorite yield was 2M>>3.5M≅1M>0.5M>>6M, with respect to NaOH concentration. With increasing the NaOH concentration and extending the reaction time, sodalite and cancrinite generated as minor phases. The fly ash treated with 2M NaOH for 30h showed the best removal characteristics and took up about 0.5mmol·g-1 for both Cs+ and NH4+ ions. The uptake amounts of resulting products were found to depend on the Al-substituted tobermorite yield.
