Solid Waste Incineration Fly Ash Research Articles

Alkali-Activated Materials with Pre-Treated Municipal Solid Waste Incinerator Bottom Ash

This study presents the results of an experimental campaign on the use of municipal solid waste incinerator bottom ash (MIBA) and fly ash (FA) as precursors for the production of alkali-activated materials. MIBA was subjected to a pre-treatment stage in response to two issues: high metallic aluminum content, which reacts in a high pH solution, releasing hydrogen; and low amorphous content of silica-, aluminum- and calcium-bearing phases, which translates into a limited formation of reaction products. The proposed pre-treatment stage oxidizes most of the metallic aluminum fraction and compensates for the low reactivity of the material via the formation of additional reactants. Different combinations of MIBA and FA were tried—mass-based ratios of 0/100, 25/75, 50/50, 75/25, and 100/0 for MIBA/FA. Two mix designs of the alkaline activator with sodium hydroxide and sodium silicate were evaluated by varying the Na2O/binder and SiO2/Na2O ratios. These mortars were tested in the fresh and hardened state. The results showed that the pre-treatment stage was effective at stabilizing the dimensional variation of MIBA. Despite the lower reactivity of MIBA, mortars with 50/50 of MIBA/FA presented a maximum 28-day compressive strength of 25.2 MPa, higher than the 5.7 MPa of mortars made with MIBA only.

Chemical stabilization of heavy metals in municipal solid waste incineration fly ash: a review

Sufficient attention should be attached to the large amount of fly ash containing high levels of toxic heavy metals generated after municipal solid waste incineration. Because heavy metals could be leached out of the fly ash under specific conditions, it is necessary to stabilize the heavy metals in fly ash before landfill disposal. Processing technologies of incineration fly ash include solidification/stabilization technology, thermal treatments, and separation processes. This study reviewed the current treatment technologies of municipal solid waste incineration (MSWI) fly ash, with the main focus on the treatment of heavy metals in fly ash with chemical stabilization. Chemical stabilization processes involve chemical precipitation of heavy metal and chelation of heavy metals. In multiple studies, chemical stabilization technology has shown practical feasibility in terms of technology, economy, and effect. In addition, the combination of two or more stabilization agents broadens the general applicability of the agents to heavy metals and reduces the cost. The application of joint processing technology realizes the remove of soluble salt from fly ash. To minimize pollutants while increase their usable value, effective use of waste and co-disposal of several kinds of wastes have gradually become the research hotspots. New developments in chemical stabilization are progressively moving towards the sustainable direction of harmlessness and resource utilization of MSWI fly ash.

Benefits of pre-treating MSWI fly ash before alkali-activation

The significant amount of heavy metals and soluble salts contained in municipal solid waste incineration fly ash (MSWI FA) and the corresponding risk of leaching make them classified as hazardous waste. Nowadays, the ashes are usually landfilled, but another application can be the inertization and valorization of MSWI FA in building materials. Geopolymer can be a potential material because it can naturally entrap heavy metals physically and chemically inside its matrix. This research investigated how the use of electrodialytic treatment compared to a water washing procedure, considered as pre-treatments for MSWI FA, influenced a metakaolin-based geopolymer as an encapsulation matrix for MSWI FA. Geopolymers with metakaolin and 5, 10, 20 wt% of raw or pre-treated MSWI FA were compared with a sample containing only metakaolin for environmental, mechanical, and physical properties. The formation of aluminosilicate gel was confirmed for all geopolymers, although with varying degrees of impurities. The results show low compressive strength for the sample with washed ash but good mechanical strength for geopolymers with raw and electrodialytic treated ash compared to metakaolin-based geopolymer or with geopolymer with washed ash. A decrease in leaching for all the metals in the samples confirms the encapsulation capacity of geopolymers. The electrodialytic pre-treatment decreases, particularly the leaching of Cr, Zn and chloride in geopolymers, confirming the potential use of this pre-treatment to improve the environmental and mechanical characteristics of geopolymers with MSWI FA.

Pulsed stirring for energy efficiency improvements during electrodialytic extraction of As, Cd, Cr, Cu, Pb, and Zn from municipal solid waste incineration fly ash and air pollution control residue

Recycling valuable elements from municipal solid waste incineration fly ash and air pollution control (APC) residue has become the focus of research to manage this kind of residual waste. This paper assesses the possibility of energy savings to increase the economic sustainability of the electrodialytic (ED) recovery process by using pulsed stirring during extraction of As, Cd, Cr, Cu, Pb, and Zn from fly ash and APC residue suspensions and analyzing the data with multivariate statistical methods. Fly ash and APC residue in different batches were ED treated using different stirring frequencies of the ash suspensions, i.e., manually, 25%, 50%, 75%, and 100% (constant) stirring. An automatic camera was used to record the effect of pulsed stirring on the distribution of the ash suspensions during ED treatment and revealed three stages of the ash suspension during ED treatment that was presented in a conceptual model. The results showed that applying both pulsed and constant stirring could increase the acidification, the redox potential of ash suspensions, and the contact between ash particles and H+, thus boosting the extraction of metals. The regression coefficients and variable influence on projection values based on partial least squares models show similarity between 50% stirring and 100% stirring, indicating that it is possible to save energy by applying the stirrer only 50% of the time for all ashes, without compromising the extraction of the metals.

Investigation of Mechanochemically Treated Municipal Solid Waste Incineration Fly Ash as Replacement for Cement

Municipal solid waste incineration (MSWI) fly ash has been classified as hazardous waste in China because of the leachable toxic heavy metals and high concentrations of chlorides and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). Currently, the main treatment method is still landfilling after chemical treatment or cement solidification, and an effective approach to realize fly ash utilization is still lacking. In the present work, the fly ash was firstly water-washed to remove the soluble chlorine salts, which can improve the performance of the produced cement mortar in later work. Mechanochemical pre-treatment was adopted to destroy the PCDD/Fs and improve the heavy metals’ stabilization. The results show that 75% of PCDD/Fs can be degraded and that most of the heavy metals are stabilized. After the mechanochemical pre-treatment, the average particle size of the fly ash decreases to 2–5 μm, which is beneficial for promoting the activation energy and accelerating the hydration process in cement mortar production. The compressive and flexural strengths of the fly ash cement mortar improve to 6.2 MPa and 32.4 MPa, respectively, when 35% of the OPC is replaced by treated fly ash. The similarity in the 3-day and 28-day strength with or without the addition of the treated ash shows the light influence of the fly ash addition. Thus, the mechanochemical process can stabilize the heavy metals and activate the fly ash, allowing it to partly substitute ordinary Portland cement in building materials, such as cement raw materials and concrete.

Effect of Si/Al additives on Cl fate during MSWI fly ash thermal treating process

SiO2 and Al2O3 (Si/Al) are proper additives for municipal solid waste incineration (MSWI) fly ash melting. However, Si/Al additives impact the emission of chlorine (Cl), which is harmful to the ecology and environment. In this study, co-thermal treating experiments of fly ash and SiO2 or Al2O3 were carried out to determine chlorine migration and transformation. Results show that the release of HCl is significantly promoted by the addition of SiO2 or Al2O3. Thermodynamic equilibrium calculation shows that the reaction rate between additives (SiO2 or Al2O3) and CaCl2 is the main factor limiting the release of HCl. Besides, SiO2 has an obvious effect on reducing Cl percentage in residues, as the addition of 30% SiO2 raises the Cl removal rate to 99.72% at 1250 °C. Main component in the residuals is Ca-silicate after addition of SiO2. Compared to SiO2, the addition of Al2O3 is more likely to retain Cl in the residues. Al2O3 reacts with fly ash to generate Cl-containing minerals, such as Ca10(SiO4)3(SO4)3Cl2 and Ca12Al10.6Si3.4O32Cl5.4, leading to a lower removal rate of Cl. Moreover, Cl combined with Na and K is transformed to secondary fly ash by volatilization and condensation. Our findings may assist in pollutant discharge control in developing a new melting furnace.

Sustainable alkali-activated binders with municipal solid waste incineration ashes as sand or fly ash replacement

The present study investigates the feasibility of using two types of municipality solid wastes incineration ashes, namely, fly ash and bottom ash in the production of sustainable alkali-activated binder. The ashes are collected from the incineration plant and characterized to determine their particle size distribution, specific gravity, chemical composition, and heavy metals content. The ashes are then used as either fly ash or sand replacement with five replacement ratios 0%, 5%, 10%, 15%, and 20% to produce the binder. The produced binder are characterized in terms of strength, workability, density, water absorption, thermal conductivity and stability, chemical composition, and heavy metals content. The results reflect the ability of producing sustainable alkali-activated binder with small dosage of MSWI ashes as either fly ash or sand replacement without negatively affecting its strength, workability, density, and water absorption. The ashes enhance the thermal insulation capability of the binder.

Sustainable municipal solid waste incineration fly ash (MSWIFA) alkali-activated materials in construction: Fabrication and performance

Sustainable municipal solid waste incineration fly ash (MSWIFA) alkali-activated materials in construction: Fabrication and performance

Synergistic treatment of heavy metals in municipal solid waste incineration fly ash with geopolymer and chemical stabilizers

Municipal solid waste incineration fly ash (MSWI-FA) is globally defined as hazardous waste and needs stabilization treatment. In this paper, synergistic treatment by geopolymerization and chemical stabilizers for the heavy metals in MSWI-FA was proposed, and its mechanism was further investigated. The leaching test showed that the concentration of Cu, Cr, Cd, Ni, Zn and Pb could meet the requirement of disposal standard, with more than 99.8% been effectively stabilized while Cr and Ni were below the quantification limits. The MSWI-FA was activated in geological polymerization process and produced Al/Si-based hydration products, while the chemical stabilizers formed chelates with heavy metals, yielding double effects on the geopolymerization. Therefore, with the co-effectiveness of the two processes, most of the heavy metals were firmly stabilized in the compound structure. The developed geopolymerization procedure had potential applications for treating heavy metals in MSWI-FA.

Preparation of municipal solid waste incineration fly ash-based ceramsite and its mechanisms of heavy metal immobilization

With an increase in municipal solid waste incineration (MSWI) fly ash and its dangerous characteristics, the manner of its disposal has caused widespread concerns. In this study, ceramsite was prepared by using MSWI fly ash, civil sludge, and contaminated soil as the main raw materials; then, a certain proportion of clay was added as an additive. The optimum MSWI fly ash content and sintering conditions were investigated, and the immobilization mechanisms of heavy metals were explored. Based on the obtained results, the optimum preparation conditions were a preheating temperature of 400 °C, a preheating time of 10 min, a sintering temperature of 1150 °C, and a sintering time of 20 min. Moreover, the optimal raw material ratio of MSWI fly ash, civil sludge, contaminated soil, and flint clay was 30%:40%:15%:15%. Under these optimum preparation conditions, the obtained ceramsite showed the following excellent performance parameters: a 1-h water absorption of 0.97%, bulk density of 998.7 kg/m3, and cylindrical compressive strength of 37.84 MPa. Furthermore, the leaching of heavy metals was far less than the standard GB5085.3-2007. The immobilization of heavy metals in the ceramsite was mainly caused by the glass phase encapsulation and the formation of new crystal phase with the heavy metals. In addition, the generation of aluminosilicates played a positive role in the immobilization of heavy metals. Thus, the reuse of MSWI fly ash by preparing fly ash-based ceramsite is one of the effective methods for reducing solid wastes.

Removal of Inorganic Salts in Municipal Solid Waste Incineration Fly Ash Using a Washing Ejector and Its Application for CO2 Capture.

This study investigated the effects of washing equipment for inorganic salts, such as NaCl, KCl, and CaClOH, to decontaminate municipal solid waste incineration fly ash (MSW-IFA). Based on the feature of hydrodynamic cavitation, the device developed in this study (referred to as a ‘washing ejector’) utilizes the cavitation bubbles. A washing ejector was analyzed under a range of conditions, employing as little water as possible. In hydrodynamic cavitation, the increase in fluid pressure with increasing static pressure is mainly attributed to the increase in particle–bubble collisions via the cavitation flow. The results revealed that the fluid pressure influenced the removal of inorganic salts during cavitation in water. This is because during the washing process from the collapse of cavitation bubbles, the release is achieved through the dissolution of inorganic salts weakly bound to the surface. After treatment by a washing ejector, the removal of soluble salts elements such as Cl, Na, and K was reduced by approximately 90%. Removing the inorganic salts in the IFA altered the characteristics of the Ca-related phase, and amorphous CaCO3 was formed as the cavitation flow reacted with CO2 in the ambient air. Furthermore, the washing effluent produced by washing IFA was found to be beneficial for CO2 capture. The washing effluent was enriched with dissolved Ca from the IFA, and the initial pH was the most favorable condition for the formation of CaCO3; thus, the effluent was sufficient for use as a CO2 sequestration medium and substitute for the reuse of water. Overall, the process presented herein could be effective for removing soluble salts from IFA, and this process is conducive to utilizing IFA as a resource.

The Performance Evaluation of Asphalt Mortar and Asphalt Mixture Containing Municipal Solid Waste Incineration Fly Ash.

The aim of the research is to quantify the property of asphalt mortar and asphalt mixture containing municipal solid waste incineration (MSWI) fly ash. The potential of partially replacing mineral fillers with MSWI fly ash in asphalt mixture production was investigated. Five different MSWI fly ash replacement ratios, which include 0%, 25%, 50%, 75%, and 100%, were adopted to assess the influence of fly ash dosage, and the optimum fly ash replacement ratio was proposed. The rheological characteristics of asphalt mortar with MSWI fly ash were assessed with the dynamic shear rheometer (DSR) and bending beam rheometer (BBR). The high temperature properties of the mixture with MSWI fly ash were assessed with the Marshall stability test and the rutting test. The low temperature cracking property was determined with the indirect tensile strength test at low temperatures. The moisture stability property was identified with the immersed Marshall test and the freeze-thaw cycles conditioned indirect tensile strength test. Based on the test results, the addition of fly ash and mineral filler remarkably increased the ǀG*ǀ of the asphalt mortar. The δ of asphalt decreased as the dosage of fly ash and mineral filler increased. The addition of fly ash and mineral filler degraded the low temperature characteristics of the mortar. Fly ash improved the high temperature characteristics of the asphalt mixture. The asphalt mixture with MSWI fly ash was more susceptible to thermal cracking than the control sample. The addition of fly ash weakened the moisture stability of the asphalt mixture. In order to guarantee the low temperature characteristics and the moisture susceptibility of the asphalt mixture, the fly ash replacement ratio was recommended to be set around 25%. With proper mixture design and fly ash dosage, the asphalt mixture would have adequate performance, as well as reduced environmental impact.

Use of new bacterial strain in solidification and stabilisation of municipal solid waste incineration fly ash

The use of microbially induced carbonate precipitation (MICP) is known to be effective in the solidification and stabilisation of fly ash that results as a by-product of municipal solid waste incineration. In the search for more adaptable and applicable bacteria for MICP fly ash treatment, five species of bacteria were isolated from nursery soil. The biochemical characteristics of the five bacteria were tested to assess their adaptation to the environment of fly ash. The geotechnical properties and heavy metal leaching concentrations of the fly ash treated by the five bacteria were also tested to evaluate solidification and stabilisation effects. Results were compared with the commonly used bacteria Bacillus pasteurii. The Ensifer adhaerens strain outperformed other strains, including B. pasteurii, in environmental adaptation, particle solidification and heavy metal stabilisation of fly ash. Further MICP treatment tests under different bacterial concentrations, curing conditions and fly ash void ratios were carried out on this strain to investigate the influence of various factors on MICP efficiency. Both the MICP and the pozzolanic solidifying properties played important roles in the solidification and stabilisation mechanisms, where the best solidification effect occurred at a bacterial concentration of 14.92 × 107 cells/ml and a fly ash void ratio of 0.724.

The Effect of Adjusting Sinter Raw Mix on Dioxins from Iron Ore Co-Sintering with Municipal Solid Waste Incineration Fly Ash

The inhibition effect of calcined lime (CaO) and limestone (CaCO3) on the formation of dioxins during iron ore co-sintering with fly ash was investigated in a sinter pot in the present work. Experimental results indicated that international total toxicity equivalent concentration of dioxins decreased from 1.4335 to 0.2922, 0.1048, 0.4562, and 0.3098 ng I-TEQ Nm−3 under four different experimental conditions. It can be concluded that 5 wt.% calcined lime with 3 wt.% limestone is the optimal addition to reduce the concentration of dioxins in flue gas, with 92.70% inhibition efficiency. Effects on dioxin distribution was also analyzed. The distribution proportion of low-chlorinated dioxins was found to increase, while that of high-chlorinated dioxins decreased, except for octachlorianted dibenzo-p-dioxins (OCDD). The reason is that the consumption of HCl not only inhibits the de novo synthesis, but also dramatically promotes the condensation and dechlorination to produce more tetrachlorianted dibenzo-p-dioxins and octachlorianted dibenzo-p-dioxins through precursors. Finally, condensation, dichlorination, and inhibition mechanisms of dioxins during co-sintering with municipal solid waste incineration (MSWI) fly ash are proposed.

Utilization of municipal solid waste incineration fly ash with red mud-carbide slag for eco-friendly geopolymer preparation

Municipal solid waste incineration fly ash (MSWIFA), as a hazardous solid waste, contains such toxic substances as heavy metals and dioxin, making its disposal a global public health concern. This study aims to comprehensively combine solid waste red mud (RM), carbide slag (CS), and MSWIFA into eco-friendly geopolymer. This experiment used CS slurry and RM slurry without drying and grinding, effectively reducing energy consumption and cost. The mechanical and environmental properties of geopolymer were characterized by strength, chloride ion curing rate, and leaching concentration of heavy metals. The microscopic hydration mechanism of the binder was investigated using XRD, FTIR, TG-DTG, SEM + EDS, and MIP tests. The results show that when RM: CS: MSWIFA = 5: 2: 3, the 28 d compressive strength can reach 11.7 MPa, the chloride ion curing rate is 80.41%, and leaching levels of toxic substances are lower than the limits for landfill disposal regulated by the China standard (GB16889-2008). The Al–O and Si–O chemical bonds in RM were broken in the alkaline environment provided by CS and MSWIFA, and formed hydrate calcium chloroaluminate (HCC) and C–S–H gel with calcium ions and chloride ions. These hydration products can fill pores and reduce porosity, making the pores in the structure mainly gel micropores and mesopores with volume fractions of 10.3 and 68.1% respectively. This study expands the application of a new waste alkaline activator in alkaline activation and provides methods for MSWIFA solidification.

Environmental and economic performances of municipal solid waste incineration fly ash low-temperature utilization: An integrated hybrid life cycle assessment

Detoxification and utilization of municipal solid waste incineration fly ash (MSWIFA) with low temperature pretreatment, low environmental burden and low cost have become more and more popular topics in the world. Based on integrated hybrid life cycle assessment, this study compares the environmental and economic performance of MSWIFA low-temperature utilization with the cement kiln co-processing technique when the scenarios with or without salt recovery were considered. The result shows that the hybrid integrated life cycle assessment captures larger environmental and economic benefits of MSWIFA utilization than traditional method due to extending the system boundary to the entire economy. Especially, the avoiding in global warming, primary energy demand and human toxicity from the economic input-output system account for 15%–53%, 26%–65%, and 93%–96% of total impacts, respectively. Additionally, the hybrid model captures a considerable avoidance of cost for MSWIFA treatment. When adopting salt recovery, except for human toxicity, the environmental credit of low-temperature utilization is 3.19–12.64 times higher than that of cement kiln co-processing. Moreover, because of the saving of chemicals and energy, the environmental and economic credit of scenarios without salt recovery is significantly higher than that of scenarios with salt recovery. Findings of this study provide scientific foundations to promote the low-temperature utilization of MSWIFA, as well as multiple solutions on ash-washing wastewater treatment.

Characteristics of MSWI fly ash and its resource transformation by road engineering: Mechanical and environmental considerations

This research investigated the possibility of resource transformation of municipal solid waste incineration fly ash (IFA) in road engineering. The thermal stabilities, metallic elements, chemical compositions, morphological characteristics and physical properties of IFA were detected by means of simultaneous thermal analyzer, inductively coupled plasma mass spectrometry, X-ray fluorescence spectrometer and scanning electron microscope, the results showed that IFA had the potential to be reused as road substitute material. Based on this, the mechanical properties and heavy metal leaching toxicities of IFA in asphalt mixture and cement stabilized macadam were studied. Results showed that the asphalt mixture with SMA gradation type could digest more IFA than the asphalt mixture with AC or ATB gradation type because of its high strength from skeleton-dense structure, high asphalt content and the toughening and anti-cracking effect of lignin fiber. And the asphalt binder could effectively bond and stabilize the heavy metals of IFA. The applicability of IFA in cement stabilized macadam was stronger and the digestibility was more, and it could promote the increase of compressive strength when the content of IFA was suitable. When the content of IFA was high, the application of IFA could be realized by adjusting the parameters of cement dosage and gradation type. The solidification of heavy metals in cement stabilized macadam was achieved by the hydration products such as C-S-H gels, Ca(OH)2, ettringite and so on, which had a series of physical chemistry effects on heavy metals. The application of IFA in road engineering was technologically sound and environmentally safe.

Carbon reclamation from biogas plant flue gas for immobilizing lead and neutralizing alkalis in municipal solid waste incineration fly ash

Immobilizing heavy metal lead (Pb) and controlling alkalinity are crucial for municipal solid waste incineration fly ash (MSWI-FA) while carbon emission from incineration flue gas has hardly peaked yet. In this study, an actual flue gas from biogas plant was used for stabilizing Pb and neutralizing alkalis in MSWI-FA. Results indicated that carbonation process further incremented the Pb immobilization rate by 58.99%–95.66% based on agent treatment. With increasing carbonation time to 4.5 h, the unstable exchangeable fraction tended to zero, contributing to a leaching decrease of Pb correlated with pH, except in a strongly acidic environment. The formation of calcium carbonate boundary layer made Pb leachability less susceptible to the influence from curing time, while reduced the leaching pH to standard-satisfied 8.80. After the carbonation, 0.13 gCO2/gMSWI-FA was calculated as the theoretical carbon dioxide (CO2) capture capacity, with a cost reduction of 5.5% compared to direct agent treatment. All the results demonstrated that the flue gas carbonation combined with agent stabilization was a promising choice for MSWI-FA treatment due to the upgrade of economy and downgrade of carbon emission.

A CIRCULAR ECONOMY IN WASTE MANAGEMENT CARRYING OUT EXPERIMENTAL EVALUATION OF COMPRESSED STABILIZED EARTH BLOCK USING MUNICIPAL SOLID WASTE INCINERATOR FLY ASH

The proper reuse and treatment Municipal solid waste incinerator fly ash is a is current a global concern. MSWI fly ashes possess a high concentration of SiO2, allowing them to be utilized as a raw material in the production of CSEB. This research looks into compressed stabilized earth blocks (CSEBs) that use municipal solid waste incinerator fly ash (MSWIFA) as an alternative to soil-sand mixture and sand. The experiment was divided into two phases: in the first, the effect of municipal solid waste incinerator fly ash on substituting soil-sand mix without affecting original performance, as well as resistance to sulfate attack, was emphasized. The effect of MSWIFA particle size and replacement ratio on replacing natural sand was then investigated. The analysis reveals that including MSWIFA into a soil-sand mixture considerably improved block performance, particularly under wetting–drying cycles and sulfate attack. MSWIFA particle size and replacement ratio have a significant influence on block strength and water absorption. Compressive and flexural strength are improved by the addition of 20% MSWIFA with a particle size of 0/4.75 mm. As a result, the research establishes a new investigation into the environmental recycling of MSWIFA in the context of the circular economy.

Effects of Chlorides and Sulphates on Heavy Metal Leaching from Mortar with Raw and Electrodialytically Treated MSWI Fly Ash.

Municipal solid waste incineration (MSWI) fly ash could be used as supplementary cementitious material in cement-based materials. However, heavy metal leaching, such as Cd, Cr, Cu, Pb and Zn, both from the MSWI fly ash and cement-based materials containing MSWI fly ash, remains a persistent obstacle. Here, an up-scaled electrodialytic treatment was used as a pre-treatment to remove heavy metals from MSWI fly ash before using the fly ash in mortar. Mortar samples with 10 wt% replacement of cement with either raw or elecrtodialytically treated MSWI fly ash were subjected to monolithic (in-use scenario) and crushed mortar (end-of-life scenario) leaching tests. The environmental conditions (e.g., exposure to chlorides or sulfates) at the surface of cement-based materials can affect leaching. Acidified H2O, NaCl or Na2SO4 solutions were, therefore, used for the leaching tests. Up to 80% heavy metal removal by the up-scaled electrodialytic pre-treatment was feasible. Regulatory limits for disposing of the MSWI fly ash in non-hazardous waste landfills were exceeded, even if the electrodialytic treatment removed heavy metals. However, leaching from monolithic mortar samples complied with the regulatory limits, while Cr leaching exceeded the regulatory limits for all crushed mortar samples when using NaCl or Na2SO4. Both NaCl and Na2SO4 generally increased the heavy metal leaching yield from fly ash and mortar compared to leaching with acidified H2O. The results of the study suggest that environmental conditions should be taken into account when assessing leaching from cement-based materials with MSWI fly ash.Graphical