Municipal Solid Waste Incineration Fly Ash Treatment Research Articles

Enhanced geopolymerization of MSWI fly ash through combined activator pretreatment: A sustainable approach to heavy metal encapsulation and resource recovery

With the rapid pace of socioeconomic progress, there has been a continuous rise in the generation of municipal solid waste incineration (MSWI) fly ash. Enhancing the efficiency of MSWI fly ash utilization, minimizing expenses, and developing more cost-effective and environmentally sustainable cementitious materials represent critical scientific challenges that warrant immediate attention. The research commenced with the preliminary treatment of MSWI fly ash using a blend of chemical activators and a water rinsing method. Following this, quicklime and coal fly ash were incorporated to formulate a geopolymer derived from MSWI, aimed at stabilizing the MSWI fly ash. Throughout this investigation, a selection of five chemical activators—calcium hydroxide, sodium hydroxide, sodium silicate, dilute sulfuric acid, and citric acid—was employed in conjunction with a water-washing procedure to condition the MSWI fly ash. Three single factor experiments denoted A, B, and C, were designed, and the corresponding geopolymer samples were prepared. In this research, the analysis focused on the solidified MSWI fly ash-based geopolymer samples, examining their physical and chemical characteristics, compressive strength, levels of heavy metal release, and the structure at a microscopic level. The findings revealed that the B3 series exhibited the most substantial 28-day compressive strength, reaching 1.692 MPa. Concurrently, the concentrations of leached heavy metals, including zinc (Zn), copper (Cu), chromium (Cr), lead (Pb), cadmium (Cd), and nickel (Ni), were all beneath the regulatory thresholds stipulated by the GB16889 and GB18598 criteria, signifying a notably effective solidification outcome. During the geopolymerization process, gel phases such as calcium aluminosilicate hydrate (C-A-S-H) and calcium silicate hydrate (C-S-H) are formed within the geopolymer matrix. This leads to the formation of a compact and cohesive cementitious material, which showcases superior mechanical strength and a robust capacity for heavy metal sequestration. This research contributes to the safe management of MSWI fly ash by not only facilitating its non-hazardous disposal but also enabling the efficient containment and elimination of heavy metals, chloride ions, and elemental aluminum.

Immobilization of heavy metals with chlorine and liquid phase formation during thermal treatment of MSWI fly ash

Due to effective detoxification, thermal treatment is a preferred treatment technology of municipal solid waste incineration (MSWI) fly ash. However, immobilization behavior of heavy metals during thermal treatment is unclear. In this work, a circulated fluidized bed fly ash with SiO2 addition and a grate furnace fly ash with high silica-aluminum coal ash addition were used to investigate combined effect of active chlorine content, liquid polymerization degree, temperature of initial liquid phase formation and liquid phase formation rate on the immobilization ratios of Zn, Pb and Cd by principle component analysis (PCA). The results show that the decrease in active chlorine content favors the immobilization of Zn, Pb and Cd because chlorination volatilization is reduced. Both the increase in liquid polymerization degree and the formation of initial liquid phase at low temperature promote the immobilization of Zn, Pb and Cd for physical encapsulation. However, a rapid formation of liquid phase is not favorable for the immobilization of Zn, Pb and Cd, because transfer of heavy metals between crystals and liquid phase is impeded by high viscosity of liquid phase during fusion. The results can provide a reference for how to achieve the immobilization of heavy metals by adjusting the chemical composition of MSWI fly ash during thermal treatment.

The influence of the pre-addition of semi-dry and dry slaked lime during the purification of flue gas on the subsequent chelation and solidification treatment of MSWI fly ash

Incineration is a main way to dispose the municipal solid waste (MSW) in China, but municipal solid waste incineration (MSWI) fly ash will negatively impact the environment and human health as containing high content of heavy metals. This study aimed to investigate the influence of the pre-addition of dry/semi-dry slaked lime during the purification of flue gas on the subsequent chelation and solidification treatment of fly ash. This study has found that semi-dry slaked lime had more effect on the solidification rate of heavy metals in MSWI fly ash compared to the pre-addition of the dry slaked lime. As the dosage of semi-dry slaked lime increased, the solidification rate of Zn and Ba increased to 100 %, while the solidification rate of Cr decreased to as low as 0 %. However, the effect of the dosage of semi-dry slaked lime on the other heavy metals (Cu, Pb, Cd, Ni) showed a complex trend. This study underscores the importance of the pre-addition of slaked lime during the purification of flue gas in influencing subsequent chelation and solidification treatment of MSWI fly ash. It provides valuable insights into optimizing lime dosage to enhance heavy metal stabilization, contributing to more effective and sustainable waste management practices.

A novel process for the desalination of MSWI fly ash via in-situ leachate concentrate washing and residue solution electrolysis

Desalination of municipal solid waste incineration (MSWI) fly ash is necessary prior to its disposal. Water washing followed by evaporation crystallization for salt extraction is a popular desalination process for MSWI fly ash, while facing large water consumption, high evaporation energy consumption, and difficulties in crystalline NaCl selling. Leachate concentrate is another hazardous waste produced in MSWI plant which is hard to be degraded. In this work, a novel process for the desalination of MSWI fly ash via leachate concentrate washing and residue solution electrolysis was proposed. The effects of liquid-to-solid (L/S) ratio and washing step were discussed. Low-carbon electrolysis strategy for the high-salt washed leachate concentrate was explored. Results showed that leachate concentrate washing displayed the similar desalination performance to water washing and the preferred L/S ratio was 3. The dissolution of Cl in fly ash exceeded 92 % after its twice washing. The desalination capacity of leachate concentrate decreased sharply with increasing using times while its salinity increased steadily. With CO2 injection in a regulating chamber, stable electrolysis of the washed leachate concentrate was achieved. The findings are expected to provide guidance on the treatment of MSWI fly ash, leachate concentrate as well as high-salt wastewater in other fields.

Enhancing sustainable valorization: Harmless synergistic melting treatment for high-value vitreous products from MSWI fly ash and electrolytic manganese residue

The waste-to-energy and manganese industries face significant ecological challenges due to two major risk sources: municipal solid waste incineration (MSWI) fly ash and electrolytic manganese residue (EMR), especially, the MSWI fly is classified as hazardous waste. High temperature melting is a promising method for harmless disposal of solid wastes. However, it has yet to be industrialized due to the high costs and energy consumption. This study proposes using EMR as an additive to co-melt with MSWI fly ash, aiming to develop a method that minimizes energy consumption while producing high value-added products. To this end, the phase evolution and phase-change cooling characteristics during the co-melting process of MSWI fly ash and EMR were experimentally investigated. XRD and SEM analyses revealed that pure vitreous slag can be obtained when mixtures are heated to 1500 °C for 120 min with ≥40 wt% EMR addition under natural air-cooling conditions. Additionally, to produce vitreous slag by air-cooling and increase MSWI fly ash treatment capacity, the molten mixture with 30 wt% EMR addition was adopted in the directional solidification experiments to establish a predictive model relating the average cooling rate to the glass content. The findings ultimately contribute to the advancement of melting-based industrial applications.

The migration and transformation mechanisms of heavy metals during molten salt cyclic thermal treatment of MSWI fly ash

Molten salt thermal treatment has been demonstrated to be effective in dissolving heavy metals in municipal solid waste incineration (MSWI) fly ash. However, the complex thermochemical reactions of various heavy metals during the process remain unclear. This study investigated the migration and transformation mechanisms of typical heavy metals during molten salt (NaCl-CaCl2) cyclic thermal treatment of fly ash at 600–750 °C, as well as the leaching characteristics and recovery methods of heavy metals in the reacted products. Molten chlorides could be recycled to extract heavy metals from fly ash, which reduced the leaching toxicity of heavy metals in the reacted slags. Over 64.3% of Cd, Cu and Pb in fly ash were transferred to molten salt while the migration rate of Zn was restrained to only 32.3% during the cyclic process at 750 °C. Regarding Cd, Cu, and Pb in molten salt, the chlorination and dissolution of their oxides were significant, while the combination of their chlorides with free O2– to form oxides precipitation was weak. However, the above reaction characteristics of Zn were the opposite. Furthermore, Zn2+ could be stabilized into hardystonite (Ca2ZnSi2O7) in molten salt by reacting with Si2O76- generated from the combination of O2– and SiO2. Besides, increasing the reaction temperature facilitated the chlorination and dissolution of heavy metals. For recovery, heavy metals could be concentrated on the insoluble matters of molten salt, with a maximum concentration of approximately 5 times that in fly ash.

Study on low-cost preparation of glass–ceramic from municipal solid waste incineration (MSWI) fly ash and lead–zinc tailings

Municipal solid waste incineration (MSWI) fly ash and lead–zinc tailings contain heavy metals and are detrimental to the environment. However, conventional melt disposal requires high temperatures, resulting in high costs. This study used coal gangue as a flux to reduce the melting temperature, and the one-step process successfully prepared the CaO-SiO2-Al2O3 series glass-ceramics. The results show that the solidification effect of diopside ferrous crystals on heavy metals is higher than that of anorthite and gehlenite, and the leaching concentration of heavy metals conforms to the U.S. Environmental Protection Agency and the Chinese National (GB 5058.3) standard limits. This study provides a reference for the efficient, green, low-cost treatment of MSWI fly ash, lead–zinc tailings, and coal gangue.

Solidification/Stabilization of MSWI Fly Ash Using a Novel Metallurgical Slag-Based Cementitious Material

Four industrial wastes, i.e., blast furnace slag, steel slag, desulfurization ash, and phosphoric acid sludge, were used to prepare a low-carbon binder, metallurgical slag-based cementitious material (MSCM). The feasibility of solidification/stabilization of municipal solid waste incineration (MSWI) fly ashes by MSCM were evaluated, and the immobilization mechanisms of heavy metals were proposed. The MSCM paste achieved 28-day strength of 35.2 MPa, showing its high-hydration reactivity. While the fly ash content was as high as 80 wt.%, the 28-day strength of MSCM-fly ash blocks reached 2.2 MPa, and the leaching concentrations of Pb, Zn, Cr, and Hg were much lower than the limit values of the Chinese landfill standard (GB 16889-2008). The immobilization rates of each heavy metal reached 98.75–99.99%, while four kinds of MSWI fly ashes were solidified by MSWI at fly ash content of 60 wt.%. The 28-day strength of binder-fly ash blocks had an increase of 104.92–127.96% by using MSCM to replace ordinary Portland cement (OPC). Correspondingly, the lower leachability of heavy metals was achieved by using MSCM compared to OPC. The mechanisms of solidification/stabilization treatment of MSWI fly ash by MSCM were investigated by XRD, SEM, and TG-DSC. Numerous hydrates, such as calcium silicate hydrate (C-S-H), ettringite (AFt), and Friedel’s salt, were observed in hardened MSCM-fly ash pastes. Heavy metals from both MSWI fly ash and MSCM could be effectively immobilized via adsorption, cation exchange, precipitation, and physical encapsulation.

Designing novel magnesium oxysulfate cement for stabilization/solidification of municipal solid waste incineration fly ash

Municipal solid waste incineration (MSWI) fly ash is a typical hazardous waste worldwide. In this study, an innovative magnesium oxysulfate cement (MOSC) binder was designed for stabilization/solidification (S/S) of MSWI fly ash, focusing on the interactions between MOSC binder and typical metallic cations (Pb2+)/oxyanions (AsO33-). Experimental results showed that Pb and As slightly inhibited the reaction of high-sulfate 5MS system but significantly suppressed the reaction process of low-sulfate 10MS system. The 5MS binder system exhibited excellent immobilization efficiencies (99.8%) for both Pb and As. The extended X-ray absorption fine structure spectra suggested that Pb2+ coordinated with SO42-/OH- in the MOSC system and substituted Mg2+ ion sites in the internal structure of 5Mg(OH)2·MgSO4.7H2O (5−1−7) phase. In contrast, the AsO33- substituted SO42- sites with the formation of inner-sphere complexes with Mg2+ in the large interlayer space of the 5–1–7 structure. Subsequent MSWI fly ash S/S experiments showed that a small amount of reactive Si in MSWI fly ash interfered with the MOSC reaction and adversely influenced the immobilization efficiencies of Pb, As, and other elements. Through the use of 33 wt% tailored MOSC binder for MSWI fly ash treatment, a satisfying S/S performance could be achieved.

Assessment of heavy metals mobility and correlative recovery and decontamination from MSWI fly ash: Mechanism and hydrometallurgical process evaluation

Fly ash from municipal solid waste incineration (MSWI) enriches many leachable toxic metals which readily migrate into the environment, posing serious risks to the ecosystem and human. In this study, the elements mobility, leaching availability as well as the potential maximum amounts of heavy metals in fly ash were thoroughly evaluated. To decontaminate the toxic elements from resulting fly ash leachates, The aqueous zinc (Zn) was recovered using Cyanex 572, cadmium (Cd) and copper (Cu) were effectively removed through adsorption process by a self-assembled hierarchical hydroxyapatite (HAP) nanostructure. The removal mechanism of Cd, Cu and Zn by leaching, extraction and adsorption was revealed with the results from XRD, ICP-MS and SEM. The results showed that fly ash has a high mobility under maximum availability leaching test (95% of fly ash was dissolved), a recovery rate of 91% for Zn can be obtained using Cyanex 572, and a high adsorption rate (> 95% for both Cu and Cd) was reached using HAP for the pristine fly ash leachate. The outcomes from isothermal and kinetic study revealed that Langmuir isotherm and pseudo-second order model can well describe the Cd and Cu adsorption behavior. Economic assessment suggested that the application of HAP for the removal of Cd and Cu is a technically sound and economically feasible approach. The findings of this study demonstrated that this comprehensive process integrated leaching, solvent extraction and consequential decontamination can be a practical strategy for MSWI fly ash treatment.

The Recovery of Ca and Zn from the Municipal Solid Waste Incinerator Fly Ash

The treatment and disposal of municipal solid waste incineration (MSWI) fly ash containing significant amounts of dissolvable salts and heavy metals is a seriously challenge. At present, the common treatment method for MSWI fly ash in Taiwan is the cement-based stabilization/solidification (S/S) process. In this work, an integrated hydrometallurgical process for the treatment of MSWI fly ash was evaluated. Ca was first recovered by combining water washing and ion exchange sequentially. Meanwhile, Zn in the water-washed fly ash was recovered by combining acid leaching and ion exchange sequentially. Combining the water washing efficiency of 30% on raw ash and the acid leaching efficiency of 40% on pre-washed ash, a total of 58% mass reduction rate of fly ash was achieved. In addition, an 80% Zn and 58% Ca recovery was achieved.

Integrated thermal behavior and compounds transition mechanism of municipal solid waste incineration fly ash during thermal treatment process

Thermal behavior of municipal solid waste incineration (MSWI) fly ash is extremely complicated due to the simultaneously occurred reactive processes and the products with different chemical compositions, therefore, the investigation of chemical compounds transition behavior and mechanism during the integrated thermal process is of great significance. In this study, the macro-thermal treatment of fly ash and thermo-gravimetric analysis via non-isothermal methods were carried out and Málek method was firstly introduced to explore the mechanism of multi-step reaction for fly ash. The mineral transition results suggested that the halite, sylvite in the raw fly ash transformed to more complex crystals in treated samples, such as chlorellestadite, polyhalite and enstatite during the thermal process. And the heavy metals leaching concentration decreased with the temperature increased from 300 °C to 1200 °C, and the leaching values were lower than the standard limitation after thermal treatment. In addition, three major steps of fly ash reactions (300–380 °C, 650–750 °C and 890–1130 °C) during the thermal process were observed and expressed by first order reaction for the first step, three-dimensional diffusion for the second step and three dimensions of limiting surface reaction between both phases for the third step, respectively. The kinetic study revealed that the mineral transition process was in well accordance with the simulated reaction mechanism during the thermal treatment. The obtained results are expected to provide the research basis for studying detailed thermal characteristics and reaction mechanism during the thermal treatment of MSWI fly ash.

Thermal treatment of municipal solid waste incineration fly ash: Impact of gas atmosphere on the volatility of major, minor, and trace elements

Development of thermal processes for selective recovery of Zn and other valuable elements from municipal solid waste incineration (MSWI) fly ash requires comprehensive knowledge of the impact of gas atmosphere on the volatile behaviour of the element constituents of the ash at different reaction temperatures. This study assesses the partitioning of 18 elements (Al, As, Bi, C, Ca, Cd, Cl, Cu, K, Mg, Na, P, Pb, S, Sb, Sn, Ti, and Zn) between condensed and gaseous phases during thermal treatment of MSWI fly ash in both oxidising gas and reducing gas atmospheres, at different temperatures spanning the range 200–1050 °C. The operating atmosphere had major impacts on the partitioning of the following elements: As, Bi, C, Cd, Cu, Na, Pb, S, Sb, Sn, and Zn. The partitioning of these elements cannot be accurately predicted over the full range of investigated operating conditions with global thermodynamic equilibrium calculations alone, i.e. without also considering chemical kinetics and mass transfer. In oxidising conditions, the following elements were predominately retained in condensed phases, even at high temperatures: As, Bi, Sb, Sn, and Zn. All these elements, except As, were largely released to the gas phase (>70%) at high temperatures in reducing conditions. The impact of gas atmosphere on the volatility of Cd and Pb was greatest at low reaction temperatures (below ~750 °C). Results for volatile matrix elements, specifically C, Cl, K, Na, and S, are interpreted in terms of the mechanisms governing the release of these elements to the gas phase.

HCB dechlorination combined with heavy metals immobilization in MSWI fly ash by using n-Al/CaO dispersion mixture

Municipal solid waste incineration fly ash (MSWI-FA) has been strictly controlled as hazardous waste globally because it contains various heavy metals and dioxins. This study prepared a nanometallic Al/CaO (n-Al/CaO) dispersion mixture via ball-milling as a reductive stabilization reagent for the simultaneous immobilization of heavy metals and detoxification of POPs like substance in MSWI-FA. Under optimal conditions, Cu, Zn, Cd, Cr, Ni, and Pb had been significantly immobilized (over 99.9 %) and the leaching concentration of Zn, Cd, Cr, Ni, and Pb were below the detectable limit. Simultaneously, 82.43 % of HCB can be destructed into alkanes and amorphous carbon. The porous structure of the fly ash and alkaline surface of n-Al/CaO promoted the adsorption and cracking of HCB. The highly active n-Al/CaO interacted with water as the hydrogen donor to promote the reductive dechlorination process. Hydrocalumite was a new mineral formed from the adsorption and complexation of heavy metal. Therefore, n-Al/CaO can strengthen the control of heavy metals in the S/S treatment of MSWI-FA, effectively detoxify chlorinated organics, and reduce environmental health risks.

Review of harmless treatment of municipal solid waste incineration fly ash

Incineration is widely adopted in municipal solid waste management, which produces large amounts of municipal solid waste incineration (MSWI) fly ash. The harmless treatment of MSWI fly ash requires the appropriate disposal of heavy metals and dioxins that are enriched in fly ash. This review summarizes recently developed harmless disposal methods for MSWI fly ash including solidification/stabilization, thermal treatment, and separation/extraction. In addition, we discuss heavy metal and dioxin fixation, and the removal capacity of fly ash via solidification/stabilization (including cement solidification, chemical stabilization, hydrothermal processes, and mechano-chemical methods), thermal treatment (including sintering, fuel-burning, or electric melting/vitrification), and separation/extraction (including water-washing, chemical reagent leaching, biological leaching, electrodialysis separation, chemical reagent extraction, and nanomaterials extraction). The advantages and disadvantages of different harmless treatment methods are compared and future research prospects and suggestions are summarized. This review provides general guidelines for the harmless treatment of MSWI fly ash in the future.

Enhanced solidification/stabilization of lead in MSWI fly ash treatment and disposal by gelatinized sticky rice

ABSTRACT Recently, innocent treatment of heavy metals in hazardous waste has become a hot topic in China. In particular, lead (Pb) as a typical heavy metal, is one of the easiest leaching heavy metal elements for municipal solid waste incineration (MSWI) fly ash. In this paper, different dosages of gelatinized sticky rice (SR) as green additives were added into the mixture of MSWI fly ash (FA) and ordinary Portland cement (OPC) to solidify/stabilize Pb in an attempt to optimize cement solidification. The leaching behaviour of Pb, hydration phases and hydration microstructure were determined by Toxicity Characteristic Leaching Procedures (TCLP) leaching test, Tessier sequential extraction method, XRD, BET and SEM. The results showed that Pb leaching concentration significantly decreased when adding 10% OPC and 30% gelatinized SR solution compared to only OPC treatment, and increasing dosage of SR also reduced Pb leaching concentration and met the criteria of landfill after curing 28 days. Additionally, increase of gelatinized SR dosage made Pb in fraction of Fe–Mn oxides more easily transformed into the stable crystal and organic matter structure of FA solidified products, and the growth of hydration products were restricted and particle size became finer. The addition of gelatinized SR also reduced initial/final setting times and increased compressive strength. The data suggest that the addition of gelatinized SR provides a new and clean approach to enhance the FA/OPC solidification/stabilization and reduce the leaching concentration of heavy metals in MSWI fly ash.

Highly efficient recovery and clean-up of four heavy metals from MSWI fly ash by integrating leaching, selective extraction and adsorption

Municipal solid waste incineration (MSWI) fly ash contains significant amounts of heavy metals (e.g., Cd, Cu, Pb and Zn) and is therefore considered to be a hazardous waste requiring proper treatment prior to its disposal. In this work, an integrated hydrometallurgical process for treatment of MSWI fly ash was evaluated. Valuable metals, e.g. Cu and Zn, were first recovered by combining leaching and extraction sequentially. In the next step, the t removal of Cd and Pb from the remaining leachate using four types of iron-based adsorbents was evaluated. The leaching was optimized with respect to pH, leaching time and liquid to solid ratio. A test done under optimal conditions gave metal releases of 100% and 80% for Cu and Zn as well as 100% and 85% for Cd and Pb, respectively. The resulting leachate was contacted with organic phases based on kerosene containing the extractants LIX860N–I for Cu extraction and Cyanex 572 for Zn extraction in two consecutive steps. Efficient extractions were achieved, thus demonstrating that the combination of leaching and extraction can be successfully used for the recovery of Cu and Zn. Adsorption of heavy metal ions on various iron based sorbents to detoxify the aqueous effluent from the extraction showed good removal efficiency (more than 95%) for both Cd and Pb. The results of this study show that the proposed integrated process is a promising tool that can be used in the strategy for metal recovery and detoxification of MSWI fly ash.

Comparison of long-term stability under natural ageing between cement solidified and chelator-stabilised MSWI fly ash

Cement-solidification and chelator-stabilisation of municipal solid waste incineration fly ash (MSWI-FA) are two main treatment techniques to immobilise heavy metals. Differences in the long-term stabilities of those two methods of heavy-metal immobilisation were explored to aid in determining the better MSWI-FA treatment. However, few comparative studies have been conducted on 6-year-old cement-solidified FA (Ce-6-FA) and chelator-stabilised FA (Ch-6-FA). In this study, we compared the physicochemical and heavy metal leaching characteristics of Ce-6-FA and Ch-6-FA. The chemical speciation of heavy metals was modelled using geochemical software to assess long-term stability. The results showed weaker long-term stability in Pb immobilisation under the chelating system. The leaching concentrations of target heavy metals, acetic acid leaching tests, acid neutralising capacity, and pH-dependent leaching results indicated that Ce-6-FA had higher long-term stability than Ch-6-FA. A column experiment indicated that the cumulative release rates of Pb in Ce-6-FA and Ch-6-FA were 2.49% and 4.72%, respectively. The phase-controlled leaching of Pb in Ce-6-FA mainly occurred through Pb2(OH)3Cl and chloropyromorphite (Pb5(PO4)3Cl), whereas that in Ch-6-FA mainly occurred through Pb5(PO4)3Cl. The decomposition of heavy metal chelates in Ch-6-FA and salt generation in this process led to the release of Pb via the inorganic complex.

Review on Cement Stabilization/Solidification of Municipal Solid Waste Incineration Fly Ash

Municipal solid waste incineration (MSWI) fly ash must be treated properly prior to being disposed in the security landfill due to its serious pollution toxicity. Nowadays, lots of studies have demonstrated that cement‐based stabilization/solidification could reduce the toxicity pollution effectively by encapsulating the heavy metals into cement matrix, which leads to greater capacity and weight. This paper compares and discusses the MSWI fly ash treatment with the mostly used matrix materials such as Portland cement, phosphate cement, aluminate cement, and alkaline activated cement. Moreover, immobilization mechanism introduced by the interaction between the MSWI fly ash and hydrated cement matrix materials, such as the physical cementing effect, adsorption, isomorphous replacement, and complex precipitation, was explored in depth. The paper also pointed out some reasonable development directions for cement‐based stabilization/solidification technology to improve the effectiveness and application of cement‐based stabilization/solidification technology.

Production of glass–ceramics using Municipal solid waste incineration fly ash

Municipal solid waste incineration (MSWI) fly ash is a by-product from municipal waste incineration. According to incomplete statistics, each year more than one million tons MSWI fly ash was produced in China. Owing to high heavy elements content, widely used disposal methods of landfill are not suitable for MSWI fly ash treatment. In this study, by using MSWI fly ash as raw materials, glass–ceramics was synthesized for the solidification of heavy metals and waste recycle. Process parameters, including composition, heat treatment temperature and time, were studied and optimized. Under optimizing conditions, the product has good properties of density of 3.42 g·cm−3 and Vickers hardness of 6.91 GPa. Moreover, the leaching concentration of heavy metal elements meets allowable values of toxicity characteristic leaching procedure (TCLP). This study offers an alternative for MSWI fly ash recycle.