A novel method of calcium dissolution-crystallization-polymerization for stabilization/solidification of MSWI fly ash. (June 2023)

• Record Type: Journal Article
• Authors: Chen, Jie; Zhu, Wanchen; Shen, Yizhe; Fu, Congkai; Li, Minjie; Lin, Xiaoqing; Li, Xiaodong; Yan, Jianhua
• Is Part Of: Chemosphere. Volume 326(2023)
• Publication Date: 2023-06
• Subjects: Carbon dioxide -- Carbonation -- Heavy metals -- pH-dependent leaching -- Polymers -- Geochemical model; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2023.138465
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Municipal solid waste incineration fly ash (MSWI FA) stabilization/solidification using calcium carbonate (CaCO3 ) oligomer is an efficient, low-carbon disposal method. The insoluble Ca in FA was converted to free-Ca, utilizing for CaCO3 oligomer preparation, which was crystallized and polymerized by thermal induction to develop continuous cross-link or bulk structures for stabilization/solidification of potentially toxic elements (PTEs, e.g., lead (Pb) and zinc (Zn)). Experimental results showed that the weakly alkaline acid-leaching suspension provided an excellent condition for the generation of CaCO3 oligomers, with Pb and Zn immobilization reaching over 99.4%. With the acid strengthening of the suspension, H + took the lead in protonating with TEA and limiting the capping action of TEA, which was harmful to the synthesis of CaCO3 oligomers. Ethanol with a low dielectric constant was considered an ideal solvent for oligomer production, and triethylamine (TEA) as a capping agent established hydrogen bonds (N⋯ H) with protonated CaCO3 . H2 O molecules competed with the protonated CaCO3 molecules for TEA with ethanol concentration decreasing, resulting in erratic precipitation of CaCO3 molecules and significantly elevated leaching risk of Pb and Zn. The sequential extraction procedure, pH-dependent leaching, and geochemical analysis results revealed that the dissolution/precipitation of Ca, Pb, and Zn in treated FA was mostly controlled by the carbonate mineral phases. Moreover, the low boiling points of ethanol and TEA can be recovered for recycling. The gel-like, flexible combination of CaCO3 oligomers and FA particles formed by FA offers great resource utilization potential via a controlled crystallization polymerization process. Graphical abstract: Image 1 Highlights: Stabilization/solidification efficiency of Pb and Zn in treated FA is above 99.4%. Excessive H2 O promotes the agglomeration and precipitation of CaCO3 molecules. TEA tends to protonate with H +, thus inhibiting its capping effect. CaCO3 oligomers thermally induced uncapping for cross-linked crystallization. Carbonate mineral controls the leaching of Pb and Zn in TFA by LeachXs analysis.