The Evaluation of the Heavy Metal Leaching Behavior of MSWI-FA Added Alkali-Activated Materials Bricks by Using Different Leaching Test Methods

Abstract

Alkali-activated materials (AAMs) not only have the potential to replace cement applications in architecture and civil engineering, but also have an excellent effect on the stabilization solidification of hazardous industrial wastes. This study used two types of municipal solid waste incineration fly ash (MSWI-FA)—grate firing fly ash (GFFA) and fluidized bed fly ash (FBFA)—as AAMs brick raw materials. It is discovered from this study that AAMs bricks with different weight ratios of GFFA and FBFA can both meet the required standard of GB21144-2007 (Solid concrete brick). From the results obtained from the four leaching tests, the equilibrium pH of the leachate varies, resulting in significant differences in the leaching of heavy metals in Raw GFFA, Raw FBFA, and AAMs bricks with GFFA and FBFA. The AAMs brick with the addition of GFFA and FBFA has an alkali activation system to encapsulate heavy metals. By comparing the results obtained from the CEN/TS 14429 leaching behavior test and the four batch leaching tests, it was found that the most influential factors for the heavy metal leaching concentration are whether the heavy metal has been solidified/stabilized in the samples. GFFA and FBFA tend to have consistent characteristics after being activated by alkali to form AAMs bricks. This can be confirmed by the acid neutralization ability concentrated on a specific pH range. The results obtained from CEN/TS14429 verified that the AAMs bricks with the addition of GFFA and FBFA have excellent environmental compatibility and that it provides a comprehensive evaluation on the environmental compatibility of the test materials and products. This demonstrated that the MSWI-FA is suitable for used as alkali-activated materials and its products have the potential to be commercially used in the future.

Coal Fly Ash–Clay Based Geopolymer-Incorporating Electric Arc Furnace Dust (EAFD): Leaching Behavior and Geochemical Modeling

“…Although the behavior of the elements is similar in different matrices, that range in which the pH is minimal can vary substantially depending on the sorption phases and the complexation reactions that occur with the components of the matrix [55]. In this material, the minimum in the concentrations of Cr is between pH 5-6, for Pb and Cu is 6-7 and for Zn, Cd, and Ni is between 8-9, behaviors similar to those found in [16,23,56].…”

Immobilization of Hazardous Wastes on One-Part Blast Furnace Slag-Based Geopolymers

“…The leaching test results are shown in Table 3. The pH of the leachates varied between 11-12 (highly alkaline), according to the literature [63,64]. The leaching test determined that the reference specimens (R and M) and PG specimens (PG5, PG10 and WPG10) produce leachates with low contents of pollutants, according to the thresholds established in the Directive 2003/33/EC [65], which defines the threshold concentration for non-hazardous (NHM) and hazardous materials (HM).…”

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

“…In addition to traditional cement solidification technology, alkali-activated slag (AAS), a new type of low-carbon and low-pollution cementitious material, also shows application prospects in heavy metal solidification [ 21 ]. AAS is one of the alkali-activated cementitious materials that forms three-dimensional network polymerization products by mineral polycondensation under alkaline conditions [ 22 ].…”