Potential of sulphoaluminate cement to solidify fluorine-containing sludge

• Sulfuraluminate cement could effectively solidify heavy metal ions in fluorinated sludge at both 20 °C and 5 °C. • Fluorine-containing sludge prolonged the setting time of sulfoaluminate cement at different temperatures. • 3% of fluorine-containing sludge could still make the system meet 42.5 MPa at 20 °C. Fluorine-containing sludge was a dangerous solid waste with heavy metal ion leaching risk. The annual output was increasing significantly. Its negative impact on environmental organisms was attracting scholars attention. How to effectively and reasonably treat fluorine-containing sludge has become a research hotpot. The effect of sulphoaluminate cement on the solidification of fluorine-containing sludge and composite performance were evaluated. The results showed that fluorine-containing sludge could reduce the heat release of hydration and prolong the setting time. Low temperatures had a greater effect on the above properties. For 7 days, added 3% fluorine-containing sludge at 20 °C could achieve strength grade of more than 42.5 MPa, and other specimens could reach a strength grade of 32.5 MPa. More than 32.5 MPa of strength can be achieved in 7 days with less than 9% FS contents at 5 °C. Sulphoaluminate cement could solidify heavy metals well at both temperatures without leaching and resource utilization of fluorine-containing sludge.