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1.
Waste Manag ; 105: 425-432, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-32126370

RESUMO

In this study, the feasibility of using municipal solid waste incineration fly ash (MSWIFA) as additive for the strengthening of pretreated cement-stabilized soil was evaluated. Results indicated that the leaching concentrations of chromium and lead in MSWIFA after the water washing process and addition of 4% ferrous sulphate were reduced by 67% and 89%, respectively, which was lower than the limit value of Identification standard for hazardous waste (GB 5085.3-2007). After pretreatment, MSWIFA samples with ratios of 5% and 10% were blended into cement-stabilized soil with ordinary Portland cement (OPC) content of 10%, 15% and 20%. The unconfined compressive strength (UCS), internal friction angle and cohesion of the cement-stabilized soil increased with OPC and pretreated MSWIFA (PFA) content. The same effect was observed on UCS after the addition of 10% PFA as replacement of 5% OPC. In the subsequent X-ray powder diffraction test, scanning electron microscopy and leaching tests, the leaching concentrations of heavy metals in cement-stabilized soil became far lower than the limit value under the synergistic effects of the physical encapsulation of hydration products and stabilization of chemical agents. The incorporation of PFA as a supplementary material can effectively accelerate the formation of hydration products and can thus provide cleaner options for foundation reinforcement.


Assuntos
Cinza de Carvão , Metais Pesados , Carbono , Materiais de Construção , Incineração , Material Particulado , Solo , Resíduos Sólidos
2.
Waste Manag ; 105: 575-585, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-32171156

RESUMO

We investigated the distribution of 18 elements including non-volatiles (Al, P, Ca, Fe, Mg, K, Mn, Cu, Na, Cr, and Ni), semi-volatiles (Zn, Pb, Ag, As, and Cd), and volatiles (Hg and S) and compared their behaviors in two types of full-scale sewage sludge mono-incinerators, namely, a step-grate stoker (GS) and two fluidized bed incinerators (F-types), with the same feed sludge. Most of the non-volatile elements were enriched five-fold in all incinerated sewage sludge ash (ISSA), while the volatile S and Hg were barely enriched in ash due to the combustion components generated in the gas phase. While the semi-volatile elements were also enriched five-fold in the F-types, a different enrichment behavior was observed in the GS. Boiler and multi-cyclone dust in the GS showed higher enrichments of Pb and Cd compared to ash due to the combined effects of lower temperature and smaller particle size. Compared to the F-types, the GS generated ashes with lower toxicity as the major component (99.7%) and hazardous dust as the minor component. In the future, more attention should be paid to grate stokers in terms of recycling ISSA.


Assuntos
Metais Pesados , Esgotos , Cinza de Carvão , Incineração
3.
Waste Manag ; 105: 8-17, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-32007733

RESUMO

When it comes to the combustion of biomass, per ton of solid biofuel will generate 70 kg ash on average. Additionally, these ashes have a high specific surface area, especially fly ash, which may adsorb harmful substances and damage to human health. This work was aimed to reutilize biomass power plant fly ash to produce silica material, to reduce the hazard of ash landfill for environment. The ash underwent acid leaching with 1.5 M HCl after proper heating pre-treatment. Then, 2 M NaOH was direct to react with residue to obtain sodium silicate. Finally, acid titration of solution was used to precipitate silica. The results showed that the amorphous silica has been produced from fly ash successfully with the purity from 44.41% to 93.63% and yield of 20.45%, and the optimal calcination conditions for amorphous transformation of silica in fly ash were temperature of 611 °C with time of 5 h and the minimum crystallinity was 17.41%, modeled with response surface methodology. Spectroscopy analysis revealed that the three-dimensional network silica was hydroxylated to form the linear structure. Thermal analysis indicated that the decomposition of silanol groups tend to be stable at 400 °C, but the ash was decomposing up to 1000 °C. Morphological analysis demonstrated that BET surface area ranged from 24 m2/g to 115 m2/g, agglomerate particle size from 380.9 nm to 178.8 nm, when the ash was conversion to spherical silica. Consequently, it is possible to turn blend biomass fly ash into amorphous silica nanoparticles.


Assuntos
Cinza de Carvão , Nanopartículas , Biomassa , Carbono , Incineração , Centrais Elétricas , Dióxido de Silício
4.
Waste Manag ; 105: 61-72, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-32028102

RESUMO

Bottom ash from municipal solid waste incineration is usually treated in order to recover valuable materials like metals and to generate a mineral material for utilisation in construction industry or disposal. At present, different technologies and combinations thereof are used for bottom ash treatment resulting in different quantities and qualities of the final products (metals and minerals). So far, a comparison of these technologies is hardly possible based on the available literature. Hence, the present paper presents and applies a modelling approach that allows predicting the quantities and qualities (in terms of composition) of the final outputs of bottom ash treatment plants. In particular, material flow analysis models of five different bottom ash treatment plants were established on goods, material and element level and the mass and composition of the output flows of these plants were calculated based on an input of 118,000 Mg/a of bottom ash dry matter. The highest recovery of metals (up to 8640 ± 820 Mg/a iron, 1530 ± 220 Mg/a aluminium, 627 ± 73 Mg/a stainless steel and 608 ± 70 Mg/a heavy non-ferrous metals) can be achieved in plants that apply comminution before any ageing processes and are equipped with jiggers, inductive sorting systems and/or a high number of eddy current separators. The iron scrap fractions separated from bottom ash are contaminated by up to 114 ± 44 mg/kg Cd and up to 9900 ± 3300 mg/kg Cu, which might impair their suitability for recycling. Only minor differences in the composition of mineral material generated by different treatment plants could be observed.


Assuntos
Metais Pesados , Eliminação de Resíduos , Cinza de Carvão , Incineração , Metais , Reciclagem , Resíduos Sólidos
5.
Waste Manag ; 105: 289-298, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-32092534

RESUMO

A novel heavy metal chelating agent, dithiocarboxylate-functionalized polyaminoamide dendrimer (PAMAM-0G-DTC), was evaluated for the stabilization of heavy metals from municipal solids waste incineration (MSWI) fly ash. PAMAM-0G-DTC achieved overall stabilization performance at a lower dosage (3% w/w) and a wider pH range (2-13) compared to conventional chelating agents such as sodium dimethyl dithiocarbamate (SDD) and dithiocarboxylate-functionalized tetraethylenepentamine (TEPA-DTC). The leaching toxicity of Pb and Cd in the MSWI fly ash by PAMAM-0G-DTC stabilization met the landfill requirements but could not be achieved by SDD and TEPA-DTC even at a 10 wt% concentration. Sequential chemical extraction of fly ash before and after stabilization shows that PAMAM-0G-DTC can be combined with active heavy metals in water-soluble, interchangeable, and carbonate states to form more stable heavy metals in organic and residual states. Mechanistic studies show that multiple PAMAM-0G-DTC molecules can combine with multiple heavy metals to form three-dimensional network-like super-molecular compounds with an infinite extension of space size. This makes the heavy metals more stable and embedded in the network-like super-molecular structure, thus minimizing the potential risk of leaching. Overall, by forming more geochemically stable phases, the treatment of fly ash with PAMAM-0G-DTC has a strong ability to reduce the toxic leaching of heavy metals at a lower dosage and suppress the risk of secondary pollution in a landfill at a wide range of pH values (2-13).


Assuntos
Dendrímeros , Metais Pesados , Eliminação de Resíduos , Carbono , Cinza de Carvão , Incineração , Material Particulado , Resíduos Sólidos
6.
Environ Monit Assess ; 192(3): 185, 2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-32072314

RESUMO

Acid mine drainage/lakes (AMD/AMLs) have a low pH with high concentrations of metals and sulfate and have been a major environmental problem in the Can Coal Basin, in northwestern Turkey. In this study, metal removal from Hayirtepe AML by using fly ash (FA) and modified fly ash (MFA) was investigated in batch experiments. The effects of various parameters, such as ultrasonic frequency, dose, contact time, pH, and temperature, were examined to determine the optimum conditions for metal removal from AML. This study also focused on the application of ultrasound-assisted modification by using a 20-kHz ultrasonic probe and a 40-kHz ultrasonic bath to increase the FA surface and improve its adsorption capacity for metal removal. FA modification at 20 kHz showed better results than that at 40 kHz because it produced rapid bubble implosion with acoustic cavitation. The FA and MFAs selectivity for metal removal was 98%-99% for Fe, 96%-99% for Al, 94%-97% for Zn, 90%-95% for Co, 88%-94% for Ni, 77%-92% for Cu, and 74%-92% for Mn according to the determined optimum parameters. Scanning electron microscopy coupled with the energy-dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffractometry of the solid residues (SRs) identified gypsum as a new mineral phase from sulfate removal from the AML. Inductively coupled plasma mass spectrometry and SEM/EDX analysis revealed that the metal content of the SRs increased. The adsorption process fitted the pseudo-second order kinetic model. Thermodynamic parameters showed that the process was exothermic and the randomness of the solid/solution interface increased during adsorption. Reuse experiments indicated that the MFAs were reused more effectively for metal removal from AML compared with the FA. This study showed that the use of MFAs with a high adsorption capacity and surface area is economic and efficient for metal removal from AML.


Assuntos
Cinza de Carvão , Metais , Poluentes Químicos da Água , Adsorção , Monitoramento Ambiental , Concentração de Íons de Hidrogênio , Lagos , Mineração , Turquia , Purificação da Água
7.
Chemosphere ; 243: 125454, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31995894

RESUMO

In this study, fly ash (FA) and biochar (BC), two common industrial byproducts, were activated and surface-modified with polyethyleneimine (PEI) to enhance their capacities to remove natural organic matter (NOM) from water via adsorption. Different fluorescent components were identified using fluorescence excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC) to explore the individual adsorption behaviors of different organic constituents in a bulk NOM. The NOM adsorption was quantitatively examined via adsorption isotherm and kinetics models. Compared to the pristine adsorbents, the functionalized adsorbent with increased surface area and positive surface charge achieved higher NOM adsorption. By evaluating the adsorptive behaviors of UV-absorbing and fluorescent moieties, it was concluded that the operative mechanism of adsorption included electrostatic attraction, hydrogen bonding, and π-π interaction. At the optimal pH of 3, the surface-modified FA and BC (i.e., FA-PEI and BC-PEI) had adsorption capacities for NOM that were ∼3 times higher than the capacities of the pristine materials. Due to its aromatic features, π-π interaction may have enhanced BC and BC-PEI selective adsorption of aromatic NOM components compared to FA and FA-PEI. Kinetic modelling showed that the mesopores of FA-PEI were available for NOM adsorption and diffusion of NOM molecules into the mesoporous structures was rate-limiting. On the other hand, PEI-modification may have further reduced NOM diffusion through the narrow micropores in BC such that external adsorption primarily occurred on BC-PEI. The modified adsorbents showed a faster adsorption kinetics than the pristine counterparts and a high durability in repeated adsorption-desorption cycles.


Assuntos
Carvão Vegetal/química , Cinza de Carvão/química , Polietilenoimina/química , Purificação da Água/métodos , Adsorção , Cinética , Água/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação
8.
Ecotoxicol Environ Saf ; 190: 110120, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31896475

RESUMO

Air particulate matter (PM) can lead to extrapulmonary adverse reactions in organs such as liver and heart either by particle translocation from the lung to the systemic circulation or by the release of lung mediators. Young BALB/c mice were intranasal instilled with 1mg/BW of Urban Air Particles from Buenos Aires or Residual Oil Fly Ash. Histopathology, oxidative metabolism and inflammation on lungs and extrapulmonary organs and the systemic response were evaluated. Lung histophatological analysis supported the rise in the number of inflammatory cells in the bronchoalveolar lavage from PM-exposed animals. Also, both PM caused recruitment of inflammatory cells in the liver and heart parenchyma and IL-6 and transaminases augmentation in serum. We have shown that despite morphochemical differences, both urban air PM altered the lung and extrapulmonary organs. Therefore, exposure to urban air PM may distress body metabolism which, in turn could lead to the development and progression of multifactorial diseases.


Assuntos
Poluentes Atmosféricos/toxicidade , Material Particulado/toxicidade , Poluentes Atmosféricos/análise , Animais , Cinza de Carvão/análise , Coração/efeitos dos fármacos , Inflamação/induzido quimicamente , Fígado/efeitos dos fármacos , Pulmão/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Tamanho da Partícula , Material Particulado/análise
9.
Ecotoxicol Environ Saf ; 190: 110116, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31911387

RESUMO

Exposure to outdoor concentrations of fine particulate matter (PM2.5) is a leading global health concern. Waste incineration emission has been recognized as a potential major contributor of ambient PM2.5. Respiratory inflammation is a central feature induced by PM2.5 exposure by inhalation. However, the molecular mechanisms are not fully understood. Dual-specificity phosphatase 1 (Dusp1) plays an instrumental role in the regulation of airway inflammation. In this study, fly ash particles (20 mg/kg BW) collected from a municipal waste incinerator in China were given to BALB/c wild-type (WT) and Dusp1-/- mice by intranasal administration daily for three consecutive days. While these particles induced mild inflammation in both genotypes, a significantly higher level of serum interleukin-6 (665 pg/ml) was measured in Dusp1-/- mice challenged with fly ash particles than in their WT counterparts. Genome-wide transcriptome profiling of pulmonary coding genes in response to the exposure were performed in both genotypes by RNA sequencing. We identified 487 differentially-expressed genes (DEGs) in fly ash-challenged Dusp1-/- mice versus their WT counterparts with a log2fold-change >1.5 and p < 0.05. Functional enrichment and molecular pathway mapping of the DEGs specific to Dusp1-/- mice exposed to the particles revealed that the top 10 perturbed molecular pathways were associated with the immune response. Our study demonstrates the anti-inflammatory role of Dusp1 in protecting the lung against insults by fly ash particles, suggesting that Dusp1 might be a therapeutic target for the treatment of PM2.5-induced respiratory diseases.


Assuntos
Fosfatase 1 de Especificidade Dupla/metabolismo , Material Particulado/toxicidade , Animais , Carbono/análise , China , Cinza de Carvão/análise , Perfilação da Expressão Gênica , Incineração , Pulmão/química , Camundongos , Camundongos Endogâmicos BALB C , Material Particulado/análise , Transcriptoma
10.
Ecotoxicol Environ Saf ; 190: 110132, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31918253

RESUMO

Exposure to combustion-derived nanoparticles is recognized as a major health hazard, but the molecular responses are still insufficiently described. The transcription factor erythroid 2-related factor 2 (Nrf2, also known as NFE2L2) is a master regulator of the pulmonary defense system against insults by particulate matter. However, its downstream molecular processes are not fully characterized. In the current study, BALB/c wild-type (WT) and Nrf2-/- mice were exposed by intranasal administration to fly ash particles (F3-S; 20 mg/kg BW), which were collected from a municipal waste incinerator in China, for three consecutive days. Using a comparative transcriptomics approach, the pulmonary global gene expression profiles to F3-S exposure were characterized for both genotypes. The preponderance of the differentially-expressed genes (DEGs) in WT mice induced by the fly ash particles, was related to inflammation. Functional enrichment and molecular pathway mapping of the DEGs specific to Nrf2-/- mice exposed to the particles revealed that all of the top 10 perturbed molecular pathways were associated with the inflammatory response. Our study identified a transcriptional signature related to the initial pulmonary injury in mouse upon fly ash exposure, and suggests an anti-inflammatory role of Nrf2 in protecting the lung against such exposure.


Assuntos
Fator 2 Relacionado a NF-E2/metabolismo , Material Particulado/toxicidade , Animais , Carbono , China , Cinza de Carvão/análise , Perfilação da Expressão Gênica , Incineração , Pulmão/química , Camundongos , Camundongos Endogâmicos BALB C , Transcriptoma
11.
Waste Manag ; 104: 192-197, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31981820

RESUMO

The article presents the results pertaining to granulation of two types of fly ash from (1) coal (hard coal) incineration and (2) lignite (brown coal) combustion. The physical, chemical and mechanical properties of granules were compared to obtain the good quality of aggregates. Three types of binders were added to the ash blends: hydrated lime, Portland cement and phosphogypsum. The experimental technological line was used for pelletizing the fine mixtures; then, the obtained granules were tested immediately after their manufacturing (in fresh state) as well as after curing. The addition of binder improved their mechanical properties. Granulation of powders regimented with strictly defined shares of grains fraction. The axial compression test was conducted to find the best toughness, with consideration of the curing time of granules. Granules in the diameter of 15-18 mm were obtained using a disc granulator. The comparison revealed that the granulation of coal fly ash was more effective because of the processing conditions, and the obtained bodies were characterized by better mechanical properties then those made of the lignite fly ash.


Assuntos
Cinza de Carvão , Carvão Mineral , Materiais de Construção , Incineração
12.
Waste Manag ; 104: 213-219, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31982784

RESUMO

Incineration bottom ash (IBA) of municipal solid waste is a potential construction material for civil engineering. However, the possible leaching of trace heavy metals from IBA is a concern. Water washing is a simple and economic method to remove heavy metals from IBA. In order to optimize the water washing process of IBA, this study investigated the pH evolution during washing and its effect on the removal of several heavy metals, including lead (Pb), zinc (Zn), nickel (Ni), cadmium (Cd), copper (Cu), and chromium (Cr), through a small-scale laboratory experiment. The results show that the pH of washing water increases quickly in the first 1-3 h mainly due to the dissolution of quicklime and portlandite, and then decreases with the increasing of washing time might be due to consumption of OH- by precipitation of metal hydroxides. The concentrations of Pb, Zn, and Ni in the washing water show a similar trend as that of the pH with time, whilst the concentrations of Cd, Cu, and Cr increase with the increase of washing time. Hence, the optimum washing time should be determined accordingly based on the most concerned metal(s), as well as the pH evaluation during washing.


Assuntos
Incineração , Metais Pesados , Cinza de Carvão , Concentração de Íons de Hidrogênio , Água
13.
Waste Manag ; 104: 60-73, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31962218

RESUMO

Application of municipal solid waste incineration (MSWI) products - fly ash (MSW-FA) and bottom ash (MSW-BA), is increasingly popular, mostly due to the need to reintroduce it in the industrial chain, but also because its technical performance is constantly enhanced by a growing research effort. This paper deals with the less popular application of these wastes without the addition of a more competent precursor. Several pastes based on MSW-FA, MSW-BA or MSW-FA+MSW-BA were prepared, using sodium silicate or sodium hydroxide. Their overall performance was then assessed through mechanical (uniaxial compressive strength - UCS and seismic wave velocity), environmental (leaching) and durability tests (freeze-thaw and wetting-drying). Cement stabilised MSW-BA pastes were also tested, for reference. Results showed that a preliminary mechanical activation, achieved by milling, is fundamental; the activation with silicate is more effective than with hydroxide, especially in the case of the MSW-BA pastes, when the UCS values are more than triplicated (3-10 MPa); the MSW-BA is a more competent precursor than the MSW-FA and the durability and leachability of the alkali activated pastes is similar to that obtained with cement. The most performing paste, in terms of UCS, was obtained with BA activated exclusively with sodium silicate, with an activator/precursor weight ratio of 0.5. In general, the low-cost solidification/stabilisation proposed in this study showed competitive with the alternative use of up to 30% cement and should be regarded as a valid alternative for simple storage or low-range applications, in substitution of Portland cement.


Assuntos
Cinza de Carvão , Incineração , Materiais de Construção , Reciclagem , Resíduos Sólidos
14.
J Environ Manage ; 258: 110037, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31929072

RESUMO

The purpose of this research is to examine the neutralization performances of CaO-rich industrial waste products (IWPs) in the sulphide-rich environment of cemented paste backfill (CPB). A total of 205 CPB samples were prepared by using four different IWPs (type-C fly ash (C-FA), blast furnace slag (BFS), calcitic limestone (CL) and dolomitic limestone (DL)) as 5, 10 and 15 wt% substitute for sulphide-rich tailings. These CPB samples were cured and subjected to the acid (pH) and sulphate (SO42-) tests during 7-360 days of curing periods. MIP and XRD tests were also carried out to understand the generation of acid and sulphate and their effect on CPB stability at 28 and 180 days. The findings indicated that the utilisation of IWPs in CPB mixtures mitigated the acid (up to 58.9% higher pH values) and sulphate (up to 72.1% lower SO42- ion release) production, and enhanced the microstructure (12.43% lower total porosity) of CPBs owing to the neutralization potential, pore-filling effect, pozzolanic and partially binding characteristics of IWPs. It can be inferred from these findings that the IWPs can be suitably utilised as neutralization materials in CPB of sulphide-rich tailings. This in turn allows the mitigation of potential disposal/pollution problems associated with these IWPs.


Assuntos
Materiais de Construção , Resíduos Industriais , Cinza de Carvão , Sulfatos , Sulfetos
15.
J Environ Manage ; 260: 110042, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-31941624

RESUMO

Generally, Fly ashes (FAs) in Municipal Solid Waste Incinerator (MSWI) are classified as hazardous waste and commonly managed in a mixed way even though distinct FA in incineration flows have different characteristics. Thus, it can cause improper management of fly ashes and an increase in cost as well as the volume of residual ashes sent to the hazardous landfill. In this study, Bottom ash (BA), Secondary furnace ash (SFA), Superheater ash (SHA), Boiler chamber ash (BCA), Economizer ash (EA), and Baghouse Filter Ash (BHFA) have been sampled separately from different locations at an MSWI plant. An integrated approach involving physical, chemical, mineralogy, and leaching behavior was used to characterize the residual ashes. Results point out that the average diameter of ash particles varies from 4.87 µm for BHFA to 6825 µm for BA, with three distinct zones. The Blaine fineness value increases when the median size of ash particles decreases. All values of Loss on Ignition (LOI) at 550 °C are less than 3%, indicating a suitable burning. The main mineralogical crystalline phases in ashes were KCl, NaCl, Mg.6Al1.2Si1.8O6, CaCO3, CaSO4, CaSO3, and SiO2. Among the considered heavy metals, leaching tests identified high levels of hazardous waste for Pb, Cd, Cu, and Zn in BHFA as well as for Pb and Zn in SHA. BA, SFA, BCA, and EA are categorized as non-hazardous according to the TCLP (USEPA-1311). In terms of EN 12457-2 test, BA and SFA are inert waste; but SHA, BCA, and EA are classified as hazardous waste due to a significant level of Cl. The results show that the characteristics of ash in the separate location of the MSWI process is essential to have an economical and proper solution for ash management.


Assuntos
Metais Pesados , Eliminação de Resíduos , Carbono , Cinza de Carvão , Incineração , Dióxido de Silício , Resíduos Sólidos
16.
Chemosphere ; 241: 125107, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31683450

RESUMO

The disposal of the hazardous municipal solid waste (MSW) incineration fly ash is a critical environmental issue in China and the high contents of salts in the fly ash make the ash disposal extremely difficult. The present study proposes a novel method for the salts removal from MSW incineration fly ash using molten carbonates and chlorides at moderate temperatures from 773 K to 1073 K. The results showed that molten salts could effectively extract alkali and alkaline earth metals chlorides and sulfates from the fly ash. Other ash components, like Si/Al-compounds, were precipitated from the molten salts and concentrated in residues. By comparison, molten carbonates showed greater capability in the salts extraction while molten chlorides showed better selectivity in chlorides removal from MSW incineration fly ash. These findings suggest that the optimization of molten salts system could further prove the potential applicability of molten salts thermal treatment method for the salts removal from MSW incineration fly ash.


Assuntos
Cinza de Carvão/química , Temperatura Alta , Sais/isolamento & purificação , Álcalis , China , Cloretos/isolamento & purificação , Incineração , Eliminação de Resíduos/métodos , Resíduos Sólidos/análise , Sulfatos/isolamento & purificação
17.
Waste Manag Res ; 38(1): 27-34, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31709930

RESUMO

This research investigated the heavy metal leaching property and cementitious material preparation by treating municipal solid waste incineration fly ash through the molten salt process. The results indicated that the heavy metal thermal evaporation of fly ash in the molten salt was related to molten salt composition, heat treatment temperature and atmosphere. After treatment with sodium chloride molten salts (contains 10-50 wt% calcium chloride) from 900°C to 1000°C for 2 h, the leaching concentrations of lead, cadmium, copper, zinc and other heavy metals in fly ash were decreased more than 90% and they could fully meet with the landfill standard. Moreover, after molten salt treatment, the weight fraction of fly ash was reduced by 50 wt% than the original one, and the fly ash has been changed as a kind of cementitious material, which has excellent cementitious property. The X-ray diffraction result indicated that the main crystal mineral composition of cementitious materials obtained was alite, belite, alinite and calcium sulphate.


Assuntos
Metais Pesados , Eliminação de Resíduos , Carbono , Cinza de Carvão , Incineração , Material Particulado , Cloreto de Sódio , Resíduos Sólidos
18.
Chemosphere ; 242: 125148, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31669995

RESUMO

Modified fly ash was prepared through low-temperature roasting method using NaOH as activator. The techniques of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and the X-ray diffraction (XRD) were introduced to analyze the chemical and physical performance of samples, respectively. It was found that a significant improvements in activity and specific surface area of adsorbent. This work systematically reported the uptake performances of modified materials for single and two mixed toxic cations Pb(II) and Cd(II). The results unveiled that pseudo-second-order model was suitable to analyze the adsorption process. The adsorption process were better fitted by Langmuir model and the maximum uptake capacities were 126.55 and 56.31 mg g-1 for Pb(II) and Cd(II) in single system at 298 K, respectively. Additionally, in mixed solution, the maximum uptake capacity reduced to 120.48 and 36.10 mg g-1 under the same adsorption conditions. Competitive adsorption results demonstrated that adsorption ability was restricted by other metal ions, as while as, the binding affinity of two cations followed the order of Pb(II)>Cd(II). Meanwhile, the co-existed cations as Ca(II), Mg(II) Na(I) and K(I) had antagonistic effects on the uptake of Cd(II) and Pb(II). The results indicate that the modified fly ash was a low-cost and effective adsorbent for the cleaning up metal ions in wastewater, which has a promising application prospect.


Assuntos
Cádmio/química , Cinza de Carvão/química , Chumbo/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Adsorção , Cádmio/análise , Concentração de Íons de Hidrogênio , Íons , Cinética , Chumbo/análise , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de Fourier , Águas Residuárias , Poluentes Químicos da Água/análise , Poluição da Água , Difração de Raios X
19.
Waste Manag ; 102: 677-685, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31790926

RESUMO

Bottom ash from waste incineration is heterogeneous and contains different materials. Previous studies on the material composition of bottom ash provide only limited information as to composition, because large pieces present in bottom ash were not investigated nor were all materials were separated and analysed. The objective of the present study is to provide the complete and detailed composition of bottom ash encompassing and extensive range of different materials. Altogether, nine bottom ash samples with a mass of 3000 kg each were sieved to eight size fractions, whereby small particles adhering to larger pieces were separated by water and added to the respective size fractions. In the sorting analysis of all size fractions, the materials enclosed in molten mineral material and materials present as composites (e.g. transformers and batteries) were considered. The material characterisation revealed that the size fraction > 50 mm contains most of the iron (up to 50% of the total iron) and copper (about 20% of the total copper), while batteries, coins, silver and gold are almost exclusively present between 16 and 50 mm. The fractions between 8 and 16 mm show the highest share of aluminium (up to 50% of the total aluminium) and glass (up to 60% of the total glass). While the metal content is underestimated, if large pieces of material are disregarded, the multi-step approach applied in this study enables a complete determination of materials in bottom ash, which is essential for optimising material recovery in bottom ash treatment.


Assuntos
Incineração , Resíduos Sólidos , Alumínio , Cinza de Carvão , Metais
20.
Waste Manag Res ; 38(2): 122-133, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31793381

RESUMO

Agglomeration that occurs during municipal sewage sludge (MSS) fluidized bed co-combustion might affect heavy metal distribution and the transformation of bottom ash. A study on the mobility and speciation of heavy metals that accompanies agglomeration behavior and phosphorus addition should be examined during MSS co-combustion. Meanwhile, the aim of this study was to evaluate the total content and speciation of heavy metals during the MSS fluidized bed co-combustion by the chemical sequential extraction procedure (SEP). The risk assessment code (RAC) and individual contamination factor (ICF) are calculated to evaluate the mobility of heavy metals and their environmental risks in agglomerates. Moreover, identification of agglomerates is established by both characterization (scanning electron microscopy/energy-dispersive spectroscopy, X-ray photoelectron spectroscopy) and thermodynamic simulation (HSC chemistry software). The experimental results indicated that P and Na would form the lower melting-point compounds such as NaPO3 and Na2O in the bottom ash, which promoted agglomeration during MSS fluidized bed co-combustion. According to the simulation, Na and P have a stronger affinity than Si and Cr, and this reaction is not only influenced by particle agglomeration, but also by heavy metal distribution during modified MSS co-combustion. Nevertheless, the results of ICFs and RACs obtained from the SEP indicated that for heavy metals trapped in agglomerates, a weaker binding such as physical covering by eutectics might be considered as the dominant reaction compared with chemical binding to form a metal complex.


Assuntos
Cinza de Carvão , Metais Pesados , Incineração , Fósforo , Esgotos
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