Resource recovery of waste incineration fly ash: Synthesis of tobermorite as ion exchanger

Tobermorite was synthesized successfully from waste incineration fly ash by hydrothermal treatment in the presence of sodium hydroxide solution. The tobermorite synthesis was examined as a function of reaction temperature, time, and NaOH concentration. The formation of tobermorite was identified in all of the fly ash treated with NaOH at 180 °C, followed by the minor generations of sodalite and cancrinite phases with increasing NaOH concentration and extending reaction time. The NaOH-treated fly ash revealed the uptake behaviors for Cs⁺ and NH₄⁺, whereas the fly ash untreated with NaOH solution did not show that. The uptake amounts of resulting products were also determined: 0.40 mmol/g for Cs⁺ and 0.35 mmol/g for NH₄⁺ in the fly ash treated with 2.0 M NaOH at 180 °C for 20 h.