Solidification Mechanism of Pb and Cd in S2−-Enriched Alkali-Activated Municipal Solid Waste Incineration Fly Ash

• Published in: Materials Vol. 16; no. 10; p. 3728
• Main Authors: Xue, Qi, Ji, Yongsheng, Ma, Zhanguo, Zhang, Zhongzhe, Xu, Zhishan
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 14.05.2023; MDPI
• Subjects: alkali-activated cementitious material; Blast furnace chemistry; Blast furnace practice; Cadmium; Cement; Chemical bonds; Chemical composition; Dosage; Efficiency; Enrichment; Fly ash; Fourier transforms; GGBS; Granulation; heavy metal solidification; Incineration; Infrared spectroscopy; Landfill; Lead; Metals; MSWI fly ash; Municipal waste management; Particle size; Polymerization; Raw materials; S2−-enriched alkali-activated slag (SEAAS); S2−-enriched modification; Slag; Sodium; Sodium sulfide; Solid waste management; Solid wastes; Solidification; Synergistic effect; Waste disposal; X-ray fluorescence; China
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16103728

S2−-enriched alkali-activator (SEAA) was prepared by modifying the alkali activator through Na2S. The effects of S2−-enriched alkali-activated slag (SEAAS) on the solidification performance of Pb and Cd in MSWI fly ash were investigated using SEAAS as the solidification material for MSWI fly ash. Combined with microscopic analysis through scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR), the effects of SEAAS on the micro-morphology and molecular composition of MSWI fly ash were studied. The solidification mechanism of Pb and Cd in S2−-enriched alkali-activated MSWI fly ash was discussed in detail. The results showed that the solidification performance for Pb and Cd in MSWI fly ash induced by SEAAS was significantly enhanced first and then improved gradually with the increase in dosage of ground granulated blast-furnace slag (GGBS). Under a low GGBS dosage of 25%, SEAAS could eliminate the problem of severely exceeding permitted Pb and Cd in MSWI fly ash, which compensated for the deficiency of alkali-activated slag (AAS) in terms of solidifying Cd in MSWI fly ash. The highly alkaline environment provided by SEAA promoted the massive dissolution of S2− in the solvent, which endowed the SEAAS with a stronger ability to capture Cd. Pb and Cd in MSWI fly ash were efficiently solidified by SEAAS under the synergistic effects of sulfide precipitation and chemical bonding of polymerization products.