Liu S, Cao X, Yang W, Liu R, Fang L, Ma R, Peng J, Zheng S, Ji F. Preparation of magnesium potassium phosphate cement from municipal solid waste incineration fly ash and lead slag co-blended: Ca-induced crystal reconstruction process and Pb-Cl synergistic solidification mechanism.
JOURNAL OF HAZARDOUS MATERIALS 2023;
457:131690. [PMID:
37257382 DOI:
10.1016/j.jhazmat.2023.131690]
[Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 04/07/2023] [Accepted: 05/22/2023] [Indexed: 06/02/2023]
Abstract
Higher chlorine (Cl) content than lead (Pb) content in municipal solid waste incineration fly ash (MSWIFA) impeded the practical application of Pb5(PO4)3Cl-derived magnesium potassium phosphate cement (MKPC) preparation strategy. Herein, Pb/Ca-rich lead slag (LS) was co-blended with MSWIFA to prepare MKPC for the synergistic treatment of both two solid wastes and the Pb-Cl solidification. The results showed that the resulting 15-15 (15 wt% MSWIFA and 15 wt% LS incorporation) sample achieved 25.44 MPa compressive strength, and Pb and Cl leaching toxicity was reduced by 99.18 % and 92.80 %, respectively. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses showed that Pb2+, Ca2+, phosphate and Cl- formed PbxCa5-x(PO4)3Cl in samples. The formation of PbxCa5-x(PO4)3Cl was also demonstrated by the high-angle annular dark field scanning transmission electron microscope (HAADF-STEM), while differences in the lattice characteristics of PbxCa5-x(PO4)3Cl and Pb5(PO4)3Cl were found. In-situ XRD indicated that Ca2+ accelerated the transformation of Pb2+ to Pb5(PO4)3Cl. After co-precipitating with Ca2+ to form PbxCa5-x(PO4)3Cl, Pb2+ continuously substituted Ca2+ to eventually transform to Pb5(PO4)3Cl. This work informs the synergistic treatment of MSWIFA and LS and offers new insights into the reaction mechanism between Pb2+, phosphate and Cl- under Ca2+ induction.
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