Characterization of MSWI fly ash through mineralogy and water extraction

A comparative study on the heavy metal solidification/stabilization performance of four chemical solidifying agents in municipal solid waste incineration fly ash

“…Another method of disposal known as municipal solid waste incineration (MSWI) is gaining popularity due to its environment friendliness [6], advantages of hygienic control over solid wastes, and high capacity that can reduce waste material by about 90% in volume and 70% in weight. Besides, energy from incineration can be used to generate electricity [1,5,[7][8][9][10][11]. Thus, it has become http://dx.doi.org/10.1016/j.jhazmat.2015.07.037 0304-3894/© 2015 Elsevier B.V. All rights reserved.…”

“…The latter also contains a high level of potentially toxic metals such as Pb, Cd, and Zn which can be easily precipitated into the surface, leached into the groundwater if not treated properly. This may cause significant harm to the environment and human health [11]. Consequently, MSWI fly ashes are considered as hazardous waste in many countries [11,[18][19][20][21].…”

“…Generally, the various treatment methods for eliminating the harmful impact of these metals in MSWI FA can be grouped into three classes [8,21]: (i) metal isolation using water-extraction and electrodialytic [11,[22][23][24]; (ii) heat treatment, such as sintering, melting, or vaporization [6,[25][26][27][28], in which FA is melted at temperatures around 1300-1400 • C [27]; and (iii) solidification/stabilization (S/S) in which regulated potentially toxic metals are leached and their mobility reduced via physical encapsulation and chemical stabilization [31]. Although many toxic metals and problematic substances can be extracted for recovery and recycling using the isolation method [11], this process is too complex, and requires post-treatment of wastewater.…”

“…Although many toxic metals and problematic substances can be extracted for recovery and recycling using the isolation method [11], this process is too complex, and requires post-treatment of wastewater. In the second method, heavy metals are either incorporated in the vitrified residue or separated from the residue via evaporation [27], but some metals cannot be completely vaporized.…”

“…hydroxide, carbonates [8], H 3 PO 4 [42], phosphates [43], silicates [31,44], geopolymers [10,45]; and organic solidifying agents or chelators [46], such as ethylene diaminetetracetic acid (EDTA) and thiodiglycolic acid (TGA) [47], thiourea [11,15,41,48], sodium diethyldithiocarbamate trihydrate [8], pyrrolidines, imines, carbamates and thiols [49,50] have been used to stabilize such metals. Of the two chemical solidifying agents, organic solidifying agents have received more attention due to their low cost, room temperature hardening, flexibility and capability to immobilize and stabilize hazardous wastes without additional pre-treatment (such as pH control) required [10,51].…”