Silicate Framework Research Articles

Nonlinear dynamics and instability of aqueous dissolution of silicate glasses and minerals

Aqueous dissolution of silicate glasses and minerals plays a critical role in global biogeochemical cycles and climate evolution. The reactivity of these materials is also important to numerous engineering applications including nuclear waste disposal. The dissolution process has long been considered to be controlled by a leached surface layer in which cations in the silicate framework are gradually leached out and replaced by protons from the solution. This view has recently been challenged by observations of extremely sharp corrosion fronts and oscillatory zonings in altered rims of the materials, suggesting that corrosion of these materials may proceed directly through congruent dissolution followed by secondary mineral precipitation. Here we show that complex silicate material dissolution behaviors can emerge from a simple positive feedback between dissolution-induced cation release and cation-enhanced dissolution kinetics. This self-accelerating mechanism enables a systematic prediction of the occurrence of sharp dissolution fronts (vs. leached surface layers), oscillatory dissolution behaviors and multiple stages of glass dissolution (in particular the alteration resumption at a late stage of a corrosion process). Our work provides a new perspective for predicting long-term silicate weathering rates in actual geochemical systems and developing durable silicate materials for various engineering applications.

Sunlight assisted synthesis of silver nanoparticles in zeolite matrix and study of its application on electrochemical detection of dopamine and uric acid in urine samples

Sunlight assisted reduction of silver ions were accomplished for the synthesis of silver nanoparticles incorporated within the mesoporous silicate framework of zeolite Y. The zeolite-Y and AgNP/Zeo-Y were characterized by field emission scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption BET isotherm and X–ray diffraction techniques. The incorporation of silver nanoparticles within the porous framework was further confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. An enhanced electrocatalytic oxidation of biologically important molecules like dopamine and uric acid using AgNP/Zeo-Y modified glassy carbon electrode has been developed. A simultaneous oxidation of DA and UA peaks were obtained at +0.31V and +0.43V (vs. Ag/AgCl) using AgNP/Zeo-Y/GCE under the optimum experimental condition. A well-resolved peak potential window (~120mV) for the oxidation of both DA and UA were observed at AgNP/Zeo-Y/GCE system. The calibration curves for DA and UA were obtained within the dynamic linear range of 0.02×10−6 to 0.18×10−6M (R2=0.9899) and 0.05×10−6 to 0.7×10−6M (R2=0.9996) and the detection limits were found to be 1.6×10−8M and 2.51×10−8M by using differential pulse voltammetry (DPV) method. The proposed method was successfully applied for the determination of both DA and UA in human urine samples with a related standard deviation was <3%, and n=5 using the standard addition method.

Physical and numerical simulations of the presence of a forsterite transitional zone at high temperature and pressure: insight for scCO2 geological storage

ABSTRACTGeological sequestration is one of the most effective ways to reduce greenhouse gases, such as carbon dioxide (CO2). The deep oceanic crust dominated by ultrabasic rock could store CO2 permanently. However, the storage mechanism has not been thoroughly understood because of the limited amount of research and experiments conducted. This study explored the reactive mechanisms of water–rock–gas in an ultrabasic system under different conditions. Forsterite, the most dominant mineral found in ultrabasic reservoirs, was used to conduct laboratory physical simulation experiments. Two experimental systems were designed including an scCO2–forsterite–water system and an N2–forsterite–water system. All experiments were performed for 1000 h at an experimental temperature of 150°C and a pressure of 150 bar, respectively, to mimic the geological conditions. The liquid products from the experiments were analysed by inductively coupled plasma-optical emission spectrometry, whereas the solid samples were analysed by scanning electron microscopy with energy disperse spectroscopy. Results showed that: (1) in the early stage during scCO2/N2–forsterite–water interaction, forsterite was dissolved with a reactive transitional zone forming on the surface, which caused H+ to enter into the silicate framework and accelerated the reaction; (2) in the N2 system, the dissolution of forsterite was inhibited by the Mg2+ concentration after reaching its saturation in the late stage; and (3) in the scCO2 system, magnesite was precipitated as a secondary mineral during the late stage, which promoted the dissolution of forsterite. As a result, the degree of dissolution of forsterite in the scCO2 system was far higher than in the N2 system. The experimental results are consistent with the numerical simulation using TOUGHREACT, a geochemical simulation procedure, which showed that CO2 promotes the dissolution of forsterite greatly at high temperature and pressure.

Defects in sodalite-group minerals determined from X-ray-induced luminescence

The luminescence spectra of a suite of natural sodium framework silicates including four different sodalite variants and tugtupite have been collected during X-ray irradiation as a function of temperature between 20 and 673 K. The origin of the emission bands observed in these samples is attributed to F-centres (360 nm), paramagnetic oxygen defects (400 and 450 nm), S2 − ions (620 nm) and tetrahedral Fe3+ (730 nm). Luminescence in the yellow (550 nm) is tentatively attributed to Mn2+, and red luminescence in Cr-rich pink sodalite is possibly from Cr3+ activation. Sudden reduction in luminescence intensities of emission centres was observed for all minerals in the 60–120 K range. Since it is common to all the sodalite-group minerals, we infer it is a feature of the aluminosilicate framework. Sodalite luminescence has responses from substitutions on the framework (e.g. paramagnetic oxygen defects, Fe3+) which give sodalite properties akin to other framework silicates such as feldspar and quartz. However, the presence of the sodalite cage containing anions (such as F-centres, S2 − ions) imparts additional properties akin to alkali halides. The possibility of coupling between Fe3+ and S2 − is discussed. The overall luminescence behaviour of sodalite group can be understood in terms of competition between these centre types.

Sol-gel synthesis of mesoporous aluminosilicates with a narrow pore size distribution and catalytic activity thereof in the oligomerization of dec-1-ene

Porous aluminosilicates with Si/Al ratio of 80 have been prepared by the sol-gel synthesis using tetraethyl orthosilicate (TEOS) and aluminum nitrate (Al(NO3)3*9H2O). It has been shown that the precipitation pH value and the gelation conditions strongly affected characteristics of the porous structure, the incorporation of aluminum into the silicate framework, and the surface acidity. It has been found that the implementation of the sol-gel synthesis initially in the acidic medium followed by the alkaline one allowed producing the mesoporous aluminosilicate with the specific surface area SBET of 660 m2 g−1, the mesopore volume V of 0.74 cm3 g−1, and the pore size distribution within the range of 2–5 nm. The high activity and selectivity of synthesized aluminosilicates in the oligomerization of dec-1-ene have been revealed.The conversion of dec-1-ene reached 92%. The formation selectivity of dec-1-ene oligomers with the oligomerization degree n = 2–3 amounted 87%.

XANES and micro-Raman spectroscopy study of the barium titanosilicates BaTiSi2O7 and BaTiSi4O11

The coordination environment around Ti4+ in the photoluminescent compound BaTiSi2O7 and in BaTiSi4O11 was investigated with X-ray absorption near-edge structure spectroscopy and micro-Raman spectroscopy. The presence of VTi in TiO5 pyramidal units with one short Ti–O bond involving the apical oxygen was detected in both compounds. Interpretation of the vibrational signal from the silicate framework suggested that BaTiSi4O11 is a metasilicate containing building units of SiO4 tetrahedra, which are larger than in other barium titanosilicates. These results confirmed the same structural environment of Ti4+ as recently disclosed by structure refinement of BaTiSi2O7 and provided new insights into the unknown structure of BaTiSi4O11 in the light of the study of its physical properties as potential functional material.

N-Heptane isomerization over mesostructured silica nanoparticles (MSN): Dissociative-adsorption of molecular hydrogen on Pt and Mo sites

Mesostructured silica nanoparticles (MSN) were mixed physically with Pt and MoO3 to prepare Pt/MSN and MoO3/MSN for n-heptane isomerization. The XRD, N2 physisorption and 2,6-lutidine-adsorbed infrared (IR) spectroscopy studies showed that the introduction of Pt did not change the properties of MSN much due to lack of-interaction between Pt and the silicate framework of the MSN. However, MoO3 significantly altered the pore distribution, surface area and acidity of MSN. 2,6-Lutidine adsorbed IR showed the formation of new doublet absorbance bands at 1638 and 1631cm−1 corresponding to the presence of permanent acidic Brønsted sites. The isomerization of n-heptane distinguished the low catalytic activity of MSN, MoO3, and Pt/MSN in the presence of either hydrogen or nitrogen gas. High activity of n-heptane isomerization was observed on MoO3/MSN in the presence of hydrogen with yield of mono- and di-branched isoheptane reached 36.6 and 6.8%, respectively. No deactivation was observed on MoO3/MSN after 100h of the reaction. ESR and IR studies indicated that the high activity and stability of MoO3/MSN could be attributed to the dissociative-adsorption of molecular hydrogen to form atomic hydrogen, which subsequently formed active (MoOx)−(Hy)+. Although Pt sites have better ability to interact with hydrogen than Mo sites, the electrically neutral charge of the silicate framework was not able to form active protonic acid sites on the Pt/MSN, which only yield less than 1% isoheptane. It is plausible that the interaction of Pt/MSN and molecular hydrogen formed Pt-H which was not active in n-heptane isomerization.

Rietveld refinement of the crystal structures of Rb2 XSi5O12 (X = Ni, Mn).

The synthetic leucite silicate framework mineral analogues Rb2 XSi5O12 {X = Ni [dirubidium nickel(II) penta-silicate] and Mn [dirubidium manganese(II) penta-silicate]} have been prepared by high-temperature solid-state synthesis. The results of Rietveld refinements, using X-ray powder diffraction data collected using Cu Kα X-rays, show that the title compounds crystallize in the space group Pbca and adopt the cation-ordered structure of Cs2CdSi5O12 and other leucites. The structures consist of tetra-hedral SiO4 and XO4 units sharing corners to form a partially substituted silicate framework. Extraframework Rb(+) cations sit in channels in the framework. All atoms occupy the 8c general position for this space group. In these refined structures, silicon and X atoms are ordered onto separate tetra-hedrally coordinated sites (T-sites). However, the Ni displacement parameter and the Ni-O bond lengths suggest that for the X = Ni sample, there may actually be some T-site cation disorder.

From Helixes to Mesostructures: Evolution of Mesoporous Silica Shells on Single-Walled Carbon Nanotubes

Constructing a novel nanoplatform by integrating single-walled carbon nanotubes (SWCNTs) and mesoporous silica is of considerable interest due to their combined advantages. However, it is difficult to coat SWCNTs with mesoporous silica shells (MSS). Conventional mechanisms used in the formation of mesostructured materials can not be simply applied in this coating process because the diameter of SWCNTs is smaller than the size of surfactant micelles. Here we report the formation mechanism of MSS on SWCNTs (SWCNTs@MSS), which involves the structural evolution from helixes to mesostructures for the first time. The evolution process mainly includes four stages. The first stage is the transition from tight surfactant helix to loose silica–surfactant composite helix, followed by a second stage of gap filling process on the silica-uncovered surfaces. Afterward, the surfactant/silicate composite micelles further self-assemble onto nanotubes with the increase of diameter in the third stage. Finally, the silicate frameworks further condense to obtain stable mesostructures. The obtained SWCNTs@MSS with outstanding features exhibit high potential for cancer treatment and also promise future applications in other various fields.

Synthesis of Porous and Mechanically Compliant Carbon Aerogels Using Conductive and Structural Additives.

We report the synthesis of conductive and mechanically compliant monolithic carbon aerogels prepared by sol-gel polycondensation of melamine-resorcinol-formaldehyde (MRF) mixtures by incorporating diatomite and carbon black additives. The resulting aerogels composites displayed a well-developed porous structure, confirming that the polymerization of the precursors is not impeded in the presence of either additive. The aerogels retained the porous structure after etching off the siliceous additive, indicating adequate cross-linking of the MRF reactants. However, the presence of diatomite caused a significant fall in the pore volumes, accompanied by coarsening of the average pore size (predominance of large mesopores and macropores). The diatomite also prevented structural shrinkage and deformation of the as-prepared monoliths upon densification by carbonization, even after removal of the siliceous framework. The rigid pristine aerogels became more flexible upon incorporation of the diatomite, favoring implementation of binderless monolithic aerogel electrodes.

Cu and Co modified beta zeolite catalysts for the trichloroethylene oxidation

In this work we have studied for the first time the catalytic activity for the oxidation of trichloroethylene (TCE) of Cu and Co beta zeolites. The results show that they are active and selective towards CO2, obtaining a better selectivity than that reached with conventional H-zeolites. The copper and cobalt zeolites have been prepared by different methods. It was found that their activity depends on the metal and on the preparation procedure. The most active catalyst was the Cu-BEA prepared by ion exchange (T50%=310°C and T90%=360°C). This catalyst has the highest ammonia adsorption capacity (as a measurement of the acidity) and it was the only tested material in which the Me2+ was completely reduced in a standard H2-TPR experiment (indicative of its important redox properties). Thus, the enhanced activity of the Cu-exchanged zeolite was associated to the presence of strong acid sites in the zeolite and to the redox properties of the copper ion exchanged. The catalyst was stable at 300°C for almost 70h without any important deactivation. This was related to the oxidative properties of the copper that avoid the formation of coke on the strong acid sites of the zeolite. On the other hand, zeolites with the transition metal incorporated into the zeolite framework by hydrothermal synthesis showed lower catalytic activity, probably because the formation of small oxide particles with much less interaction with the silicate framework, that results in a lower redox activity of the transition metals. It has been shown that a proper combination of acidity, redox properties and metal-zeolite interaction is necessary in order to prepare an active and selective zeolite catalyst for the TCE oxidation.

Wollastonite ceramics with bimodal porous structures prepared by sol–gel and SPS techniques

In this work, we suggest a novel synthetic route combining sol–gel and SPS for the fabrication of porous ceramics based on wollastonite with bimodal pore size distributions (100–500 nm and 1–500 μm) and high mechanical strength (Young's modulus from 72.5 to 172 MPa). We studied peculiarities in the formation of the biporous silicate framework using two types of pore forming additives (templates) of various natures, shapes and sizes, introduced during different stages of sol–gel and SPS synthesis: organo-nonorganic (polymer latex of “core–shell” type) and nonorganic (carbonaceous filler). The influence of carbonaceous template content (5% or 25%) on the structural and mechanical properties of ceramics synthesized by spark plasma current was described. The original approach presented here provides formation of wollastonite ceramics with high mechanical strength and a biporous structure that is similar to the texture of bone tissue and is capable of executing its main functions. The obtained ceramics meet all the requirements of the bioceramics class demanded by modern medicine.

Structure and properties of ITQ-8: a hydrous layer silicate with microporous silicate layers.

ITQ-8 is a new hydrous layer silicate (HLS) with a chemical composition of [C4H8(C7H13N)2]8 [Si64O128(OH)16]·48H2O per unit cell. The synthesis of ITQ-8 was first described in 2002 by Díaz-Cabañas et al., the structure of this material, however, remained unsolved at that time. Physico-chemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and FTIR spectroscopy confirmed that ITQ-8 is a layer silicate. The XRD powder pattern was indexed in the monoclinic system with lattice parameters of a0 = 35.5168(5) Å, b0 = 13.3989(2) Å, c0 = 16.0351(2) Å, β = 106.74(2)°. The crystal structure was solved by simulated annealing. Rietveld refinement of the structure in space group C2/c converged to residual values of RBragg = 0.023, RF = 0.022 and chi(2) = 2.3 confirming the structure model. The structure of ITQ-8 contains silicate layers with a topology that resembles a (11-1) section of the framework of zeolite levyne. So far, this layer topology is unique among layer silicates. The layer can be regarded as made up of 4-, 6-, double-six and 8-rings which are interconnected to form cup-like "half-cages". Unlike other HLSs, which possess impermeable silicate layers, ITQ-8 contains 8-rings pores with a free diameter of 3.5 Å × 3.4 Å and can be regarded as a "small-pore layer silicate". In the crystal structure, the organic cations, 1,4-diquiniclidiniumbutane, used as structure directing agents during synthesis are intercalated between the silicate layers. Clusters (bands) of water molecules which are hydrogen bonded to each other and to the terminal Si-OH/Si-O(-) groups are located between the organic cations and interconnect the silicate layers. ITQ-8 is a very interesting material as precursor for the synthesis of microporous framework silicates by topotactic condensation or interlayer expansion reactions leading to 3D micro-pore systems which may be useful in applications as e.g. catalysts, catalyst supports and adsorbents of for separation.

Evidence of technetium and iodine release from a sodalite-bearing ceramic waste form

Sodalites have been proposed as a possible host of certain radioactive species, specifically 99Tc and 129I, which may be encapsulated into the cage structure of the mineral. To demonstrate the ability of this framework silicate mineral to encapsulate and immobilize 99Tc and 129I, single-pass flow-through (SPFT) tests were conducted on a sodalite-bearing multi-phase ceramic waste form produced through a steam reforming process. Two samples made using a steam reformer samples were produced using non-radioactive I and Re (as a surrogate for Tc), while a third sample was produced using actual radioactive tank waste containing Tc and added Re. One of the non-radioactive samples was produced with an engineering-scale steam reformer while the other non-radioactive sample and the radioactive sample were produced using a bench-scale steam reformer. For all three steam reformer products, the similar steady-state dilute-solution release rates for Re, I, and Tc at pH (25 °C) = 9 and 40 °C were measured. However, it was found that the Re, I, and Tc releases were equal or up to 4.5x higher compared to the release rates of the network-forming elements, Na, Al, and Si. The similar releases of Re and Tc in the SPFT test, and the similar time-dependent shapes of the release curves for samples containing I, suggest that Re, Tc, and I partition to the sodalite minerals during the steam reforming process.

Cerasomes: Soft Interface for Redox Enzyme Electrochemical Signal Transmission.

Anionic cerasomes, which consist of a liposomal lipid bilayer and a ceramic surface, were used as a soft interface for the construction of an integrated modified electrode to achieve the transmission of chemical information from a redox enzyme through electrical signals. The morphological properties of the cerasomes were systematically compared with those of two structural analogues, namely, liposomes and silica nanoparticles. The results indicated that the cerasomes combined the advantages of liposomes and silica nanoparticles. The lipid bilayer gave excellent biocompatibility, as in the case of liposomes, and high structural stability, similar to that of silica nanoparticles, was derived from the silicate framework on the cerasome surface. The performance at the electrochemical interface created by means of a combination of cerasomes and horseradish peroxidase on a glassy carbon electrode was much better than those achieved with liposomes or silica nanoparticles instead of cerasomes. The potential use of cerasomes in the construction of supramolecular devices for mediator-free biosensing was evaluated.

Interlayer expansion using metal-linker units: Crystalline microporous silicate zeolites with metal centers on specific framework sites

Interlayer expansion using silylating agents to connect layer silicates to 3D framework structures has shown to be a versatile synthesis route to new crystalline, microporous frameworks. We demonstrate here that also Me cations can be introduced on the linker sites applying the same synthesis procedure. An acidic aqueous Fe-chloride solution was used in a hydrothermal reaction to convert the layered hydrous silicate precursor RUB-36 into an interlayer expanded zeolite, containing Fe at the linker sites, Fe-IEZ-RUB-36, Si19.14Fe0.86O38(OH)4. Structure analysis from powder X-ray data using the Rietveld technique confirmed that the porous framework is stable upon calcination and contains Fe on T-sites at the linker position. SEM–EDX analysis is in agreement with the analysis of the electron density maps showing that almost every other linker T-position is occupied by Fe-ions. The material crystallizes in the monoclinic space group Pm with a = 12.200(9) Å, b = 13.981(8) Å, c = 7.369(2) Å, and β = 106.9(1)°. Applying a similar synthesis procedure, the Sn-analog, Sn-IEZ-RUB-36, Si38.6Sn1.4O76(OH)8, has been obtained and structurally characterized. Despite its limited crystallinity, Rietveld analysis of the PXRD data set confirmed the materials framework topology and chemical composition (a = 23.856(14) Å, b = 14.103(7) Å, c = 7.412(7) Å, in SG Pnm21). We conclude, that the synthesis procedure is flexible and, meanwhile, has been extended to other metal cations such as Ti, Zn, Eu and Al leading to microporous materials with potentially active metal cations on well defined sites of the silicate framework.

The Strength of Brønsted Acid Sites in Microporous Aluminosilicates

Ensemble-averaged deprotonation energies (DPE) derived from periodic density functional theory models are insensitive to the location of isolated Al atoms and associated protons and similar among microporous aluminosilicates (i.e., zeolites) with different crystalline frameworks (MFI, BEA, FER, MOR, CHA, FAU). These DPE values are 1201 ± 11 kJ mol–1 after correcting for systematic artifacts of periodic DFT methods, which vary with framework density, and averaging over the four distinct proton locations at each Al atom. These energies rigorously reflect the strength of the acid sites in these important catalytic solids. Thus, the stability of the conjugate anions and the acid strength of these materials merely reflect the presence of Al atoms within the silicate framework, and not their specific siting or local confining environment. DPE values did not show any systematic trends with the vibrational frequency or length of O–H bonds, with Si–O–Al bond angles, or with NH3 adsorption enthalpies, properties th...

Hybrid Mesoporous Silicas and Microporous POSS-Based Frameworks Incorporating Evaporation-Induced Self-Assembly.

We fabricated a series of mesoporous silicas and mesoporous organosilicates with hierarchical porosity through evaporation-induced self-assembly using Pluronic F127 as a template in this study. We could tailor the mesophase of each mesoporous silica sample by varying the weight ratio of its two silica sources: tetraethyl orthosilicate (TEOS) and triethoxysilane hydrosilylated octavinyl polyhedral oligomeric silsesquioxane (OV-POSS-SILY). The mesophases ranged from an ordered body-centered cubic (bcc) structure (TEOS alone) to ordered face-centered cubic (fcc) structure (10 and 20 wt.% of OV-POSS-SILY) and finally to disordered spherical pores (≥30 wt.% of OV-POSS-SILY). We used small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) to study the transformations of these mesophases, while N2 isotherm sorption curves revealed the porosities of these mesoporous silicate samples. Moreover, 29Si CP/MAS solid state nuclear magnetic resonance spectroscopy allowed us to analyze the compositions of the POSS-containing silicate frameworks. Such functional mesoporous silica samples incorporating microporous POSS building units have potential applications in various systems, including optical and electronic devices.

Aggregated clumps of lithistid sponges: a singular, reef-like bathyal habitat with relevant paleontological connections.

The advent of deep-sea exploration using video cameras has uncovered extensive sponge aggregations in virtually all oceans. Yet, a distinct type is herein reported from the Mediterranean: a monospecific reef-like formation built by the lithistid demosponge Leiodermatium pfeifferae. Erect, plate-like individuals (up to 80 cm) form bulky clumps, making up to 1.8 m high mounds (1.14 m on average) on the bottom, at a 760 m-deep seamount named SSS. The siliceous skeletal frameworks of the lithistids persist after sponge death, serving as a complex 3D substratum where new lithistids recruit, along with a varied fauna of other sessile and vagile organisms. The intricate aggregation of lithistid mounds functions as a “reef” formation, architecturally different from the archetypal "demosponge gardens" with disaggregating siliceous skeletons. Leiodermatium pfeifferae also occurred at two additional, close seamounts (EBJ and EBS), but, unlike at SSS, the isolated individuals never formed accretive clumps. The general oceanographic variables (temperature, salinity, dissolved nutrients, chlorophyll, and oxygen) revealed only minimal between-seamount differences, which cannot explain why sponge abundance at SSS is about two orders of magnitude higher than at EBJ or EBS. Large areas of the dense SSS aggregation were damaged, with detached and broken sponges and a few tangled fishing lines. Satellite vessel monitoring revealed low fishing activity around these seamounts. In contrast, international plans for gas and oil extraction at those locations raise serious concerns over the need for protecting urgently this unique, vulnerable habitat to avoid further alteration. Modern lithistids are a relict fauna from Jurassic and Cretaceous reefs and the roots of the very genus Leiodermatium can be traced back to those fossil formations. Therefore, understanding the causes behind the discovered lithistid aggregation is critical not only to its preservation, but also to elucidate how the extraordinary Mesozoic lithistid formations developed and functioned.

Leachability of heavy metals from lightweight aggregates made with sewage sludge and municipal solid waste incineration fly ash.

Lightweight aggregate (LWA) production with sewage sludge and municipal solid waste incineration (MSWI) fly ash is an effective approach for waste disposal. This study investigated the stability of heavy metals in LWA made from sewage sludge and MSWI fly ash. Leaching tests were conducted to find out the effects of MSWI fly ash/sewage sludge (MSWI FA/SS) ratio, sintering temperature and sintering time. It was found that with the increase of MSWI FA/SS ratio, leaching rates of all heavy metals firstly decreased and then increased, indicating the optimal ratio of MSWI fly ash/sewage sludge was 2:8. With the increase of sintering temperature and sintering time, the heavy metal solidifying efficiencies were strongly enhanced by crystallization and chemical incorporations within the aluminosilicate or silicate frameworks during the sintering process. However, taking cost-savings and lower energy consumption into account, 1100 °C and 8 min were selected as the optimal parameters for LWA sample- containing sludge production. Furthermore, heavy metal leaching concentrations under these optimal LWA production parameters were found to be in the range of China’s regulatory requirements. It is concluded that heavy metals can be properly stabilized in LWA samples containing sludge and cannot be easily released into the environment again to cause secondary pollution.