Thermal behaviors of fluorine during (co-)incinerations of spent potlining and red mud: Transformation, retention, leaching and thermodynamic modeling analyses

• Published in: Chemosphere (Oxford) 2020-06, Vol.249, p.126204-126204, Article 126204
• Main Authors: Zhang, Gang, Sun, Guang, Liu, Jingyong, Evrendilek, Fatih, Buyukada, Musa, Xie, Wuming
• Format: Article
• Language: English
• Subjects: Coal Ash - chemistry; Fluorides; Fluorine; Fluorine - chemistry; Hazardous Waste; Incineration; Leaching; Mineral transformation; Models, Chemical; Red mud; Retention; Silicon Dioxide; Solid Waste; Spent potlining; Thermodynamics; Water
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2020.126204

Spent potlining (SPL) as a hazardous solid waste has a high content of inorganic fluorine. This study aimed at characterizing its transformation, retention and leaching behaviors with(out) the addition of red mud (RM) during the SPL incineration. The RM addition positively affected its retention and leaching rates. Its Ca-containing compounds caused Na3AlF6 and NaF to turn into more CaF2. 30% RM converted water-soluble NaF into more stable CaF2 than did SPL at 850 °C, thus reducing the leaching rate by 45.15%. 30% RM captured HF through its Ca content and enhanced its retention rate by 66.96%. 66.01% of the total fluorine was stably retained in the bottom ash, and thus, significantly reduced the toxicity of the SPL incineration products. SiO2 and Al2O3 exerted a thermally positive effect on NaF turning into CaF2. The fluoride retention of the bottom ash was mainly dominated by CaF2 and NaF with(out) RM. Smaller, coarser and more loose structures of the co-incinerated solid particles pointed to a synergistic interaction between SPL and RM. [Display omitted] •Inorganic fluorine behaviors of spent potlining co-incineration were quantified.•Addition of red mud positively affected fluorine transformations. .•30% red mud reduced fluorine leaching rate and enhanced retention rate of bottom ash.•66.01% of the total fluorine of the bottom ash was found to be insoluble fluorine.•SiO2 and Al2O3 positively affected NaF conversion into CaF2.