Hiroki Kitamura’s research while affiliated with National Institute for Environmental Studies and other places

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Publications (10)


Figure 2. Results of batch leaching tests using an APC residue solidified with blast furnace cement or magnesium oxide [12].
Figure 9. Distribution coefficients of lead arranged from JAEA database.
Figure 10. Distribution coefficients of selenium arranged from JAEA database.
Figure 20. Multiphysics.
Figure 21. Concept of how to reduce RC strength; from structure analysis given reduced strength, axial force, 2 and bending moment of RC beams are calculated.
Engineering Measures for Isolation and Sequestration of Heavy Metals in Waste as Safe Final Sink
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April 2022

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40 Reads

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Hiroyuki Ishimori

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Hiroki Kitamura

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The long-term safety management of hazardous substances is essential to the development of an environmentally sound resource circulation society. To achieve this, engineering measures to attenuate environmental risks in the isolation and sequestration of hazardous heavy metals are reviewed. From the standpoint of the isolation and sequestration of heavy metals from resource circulation, we assess the challenges in implementing immobilization technologies, constructing updated isolation structures, and controlling environmental conditions. It is also focused intensively on the (bio) chemical transformation behavior of heavy metals and its effect on the migration of the transformed materials in the environment. The contributions of solubilized and gasified metal components to emission into the environment are considered. The obtained results underscore the necessity of multiple barriers to retard and attenuate the migration of hazardous heavy metals. Innovative schemes for the isolation and sequestration of heavy metals will lead to higher levels of safety and environmentally sound resource circulation.

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Impact of diatomite addition on lead immobilization in air pollution control residues from a municipal solid waste incinerator

March 2022

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268 Reads

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7 Citations

Environmental Science and Pollution Research

Hiroki Kitamura

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[...]

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Air pollution control (APC) residues, which are known to be the byproducts of incineration treatment, exhibit a high leaching potential of toxic metals. Calcium silicate hydrate (C-S–H), which is a major hydration product of hardened cement and immobilizes toxic metal, can be formed by the reaction of Ca with pozzolanic Si in a highly alkaline environment. Toxic metals might be immobilized by the addition of pozzolanic material to APC residues (instead of using cement), which is a Ca source and provides an alkaline condition. In this study, diatomite, which mainly comprises amorphous silica (SiO 2 ·nH 2 O), was investigated as a pozzolanic material for Pb immobilization in APC residues obtained from a municipal solid waste incinerator. APC residues were cured with and without the addition of diatomite at different temperatures. When diatomite was added to APC residues, pozzolanic phases such as C-S–H gel were formed via the consumption of Ca(OH) 2 and CaClOH. Compared to APC residues cured without diatomite, the leaching of Pb decreased by 99% for APC residues cured for 14 days with 10% diatomite at 70 °C. The results of sequential chemical extraction showed that water-soluble Pb in APC residues was reduced from 10.3% to nearly zero by the pozzolanic reaction. Consequently, the leaching amount of Pb dropped below 0.3 mg/L (Japanese criteria for landfill disposal). Overall, these experiments provide promising results regarding the possibility of using diatomite for pretreating APC residues.


Application of micro-scale correlation analysis to estimate metal speciation and the matrix in municipal solid waste incineration fly ash

February 2020

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67 Reads

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5 Citations

Journal of Material Cycles and Waste Management

Micro-scale correlation analysis was applied to estimate metal speciation and the matrix in municipal solid waste incineration (MSWI) fly ash in this study. The results showed that dominant metal speciation and the bonding states with fly ash matrix are different in individual fly ash particle. Micro-scale correlation analysis also suggests metal behaviors in fly ash formation processes. Metal oxides likely react with and/or are trapped in Al/Ca/Si-based matrix such as aluminosilicate in the gas phase and then followed by KCl/NaCl adsorption on the surface. Zinc can possibly form other speciation depending on combustion condition. Zinc chlorides (ZnCl2 and/or K2ZnCl4) and Zn spinels (ZnAl2O4 and ZnFe2O4) are not trapped in Al/Ca/Si-based matrix, however, adsorbed on the surface together with KCl/NaCl-based aggregates. Because metal oxides basically combine with and/or are trapped in Al/Ca/Si-based matrix, metal leachability might be controlled by not only metal oxide leachability but also leachability of Al/Ca/Si-based matrix around metal oxides.


Heterogeneities of fly ash particles generated from a fluidized bed combustor of municipal solid waste incineration

January 2020

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97 Reads

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5 Citations

Journal of Material Cycles and Waste Management

Although municipal solid waste incineration fly ash are fine particles and a priori considered as homogeneous, they have complicated structures inside their bodies. This study quantitatively investigated two categories of heterogeneity of fly ash produced from a fluidized bed combustor. They are the heterogeneity of a single fly ash particle body (intra-particle heterogeneity) and heterogeneity among fly ash particles (inter-particle heterogeneity). In the surface and semi-soluble components, Ca has smaller intra-particle heterogeneity than Al and Si. These results and ternary diagram analysis suggest that semi-soluble components consisted of mainly Ca-based matrices such as CaCO3 and unreacted Ca(OH)2 in which aluminosilicate domains. All major elements, excluding Fe and Ti, are 3–66% higher inter-particle heterogeneities on the surface than semi-soluble and insoluble core components. It shows that the surface component of the fly ash is more heterogeneous than other components of fly ash particles. Fly ash from fluidized bed combustor has intra- and inter-particle heterogeneity similar to stoker combustor. Besides, heterogeneity analysis can explain the fly ash formation process. Heterogeneity analysis suggests that Si plays more critical roles in the fly ash formation process of the fluidized bed combustor than that of the stoker combustor. Fly ash has heterogeneous bodies, and it might give non-negligible impacts on the leaching of metals included in fly ash components.


Intra- and inter-particle heterogeneity of municipal solid waste incineration fly ash particles

March 2019

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58 Reads

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7 Citations

Journal of Material Cycles and Waste Management

This study firstly investigated elemental heterogeneity of municipal solid waste incineration (MSWI) fly ash particles. Two types of heterogeneities were measured quantitatively focusing on three structural components of fly ash particles. They are internal heterogeneity of individual fly ash particles (intra-particle heterogeneity) and inter-particle heterogeneities among fly ash particles. On the surface of fly ash particles, Cl, K, and Na have 0–82% larger intra-particle heterogeneities than Al, Ca, and Si owing to KCl/NaCl-based aggregates. Smaller intra-particle heterogeneity of Ca in semi-soluble component than those of Al and Si suggest that semi-soluble Al/Ca/Si-based matrices around insoluble cores are Ca-based materials including aluminosilicate domains. Inter-particle heterogeneities of Al, Ca, and Si in semi-soluble and insoluble components are 9–40% and 49–352% higher than those of fly ash particle surface, respectively. Inter-particle heterogeneity analysis also suggests that insoluble components mainly consists of Si-, Al-, or Ca-rich cores. MSWI fly ash particles have both internal heterogeneities inside their bodies and also are heterogeneous in inter-particle level. When MSWI fly ash becomes wet during chelate treatment, it changed intra-particle heterogeneity as well as inter-particle heterogeneity. Their variations were contrast depending on element and site (fly ash particle component).


Impact of secondary generated minerals on toxic element immobilization for air pollution control fly ash of a municipal solid waste incinerator

July 2018

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121 Reads

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10 Citations

Environmental Science and Pollution Research

Impacts of secondary generated minerals on mineralogical and physical immobilization of toxic elements were investigated for chelate-treated air pollution control (APC) fly ash of a municipal solid waste incinerator. Scanning electron microscope (SEM) observation showed that ettringite was generated after the moistening treatment with/without chelate. Although ettringite can incorporate toxic elements into its structure, elemental analysis by energy dispersive X-ray could not find concentrated points of toxic elements in ettringite structure. This implies that mineralogical immobilization of toxic element by the encapsulation to ettringite structure seems to be limited. Physical immobilization was also investigated by SEM observation of the same APC fly ash particles before and after the moistening treatment. The transfer of soluble elements was inhibited only when insoluble minerals such as gypsum were generated and covered the surface of fly ash particles. Neoformed insoluble minerals prevented soluble elements from leaching and transfer. However, such physical immobilization seems to be limited because insoluble mineral formation with surface coverage was monitored only one time of more than 20 observations. Although uncertainty owing to limited samples with limited observations should be considered, this study concludes that mineralogical and physical immobilization of toxic elements by secondary minerals is limited although secondary minerals are always generated on the surface of APC fly ash particles during chelate treatment.


GEOCHEMICAL FORM ANALYSIS OF TITANIUM IN CHELATE-TREATED MUNICIPAL SOLID WASTE INCINERATION FLY ASH PARTICLES EMPLOYING CORRELATION ANALYSIS OF ELEMENTAL DISTRIBUTION LINE PROFILES

January 2017

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49 Reads

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3 Citations

Journal of Japan Society of Civil Engineers Ser G (Environmental Research)

A new method to analyze metal species in municipal solid waste incineration (MSWI) fly ash employing correlation analysis of elemental distribution line profiles was investigated. Titanium species in chelatetreated MSWI fly ash were estimated by this method. After treatments of fly ash by leaching experiments with different solvents, it showed that heavy metals were easily observed on semi-soluble and/or insoluble matrix of fly ash particles by SEM-EDX. Correlation analysis of elemental distribution line profiles showed that crystalline titanium species in fly ash were rutile (TiO2) and/or perovskite (CaTiO3). They were incorporated in aluminosilicate phase like gehlenite (Ca2Al2SiO7) and amorphous minerals. In addition, some of non-crystalline titanium seems to combine with aluminosilicate. Correlation analysis of elemental distribution line profiles by SEM-EDX could estimate crystalline and non-crystaline titanium species, which could not be indentifed by XRD analysis.


DIRECT FORMATION OF FLUORAPATITE VIA AMORPHOUS CALCIUM PHOSPHATE MAINLY CONTRIBUTES TO FLUORINE IMMOBILIZATION OF ELECTRIC ARC FURNACE STEELMAKING SLAG BY APATITE TREATMENT

January 2016

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23 Reads

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1 Citation

Journal of Japan Society of Civil Engineers Ser G (Environmental Research)

Fluorine immobilization mechanism of apatite treatment for electric arc furnace steelmaking slag was investigated. Apatite treatment immoboilized fluorine strongly and prevented from secondary leaching of fluornie. This study found that fluorapatite formation mainly contributed to fluorine immobilization. Synchrotron X-ray diffraction analysis showed that fluorapatite was generated directly from amorphous calcium phosphate, not hydroxide/fluorine ion-exchange reaction inside hydroxyapatite. When fluorine was adsorbed to amorphous calcium phosphate, fluorapatite was synthesized soon and encapsulated fluorine inside its crystal structure. On the other hand, fluorine adsorbed to hydroxyapatite could be released easily before slow fluorapatite formation. Sodium alginate and chitosan could generate organic-apatite complex with multi-layer structure and relatively homogeneous surface. When these organic-apatite complexes could be synthesized on slag surface, however, they gave less fluorine immobilization than normal apatite treatment and promoted fluorine leaching. Competitive adsorption between fluorine and alginate/chitosan onto amorphous calcium phosphate might inhibit fluorapatite formation.


Geochemically structural characteristics of municipal solid waste incineration fly ash particles and mineralogical surface conversions by chelate treatment

September 2015

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96 Reads

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26 Citations

Environmental Science and Pollution Research

Leaching behaviors of heavy metals contained in municipal solid waste incineration (MSWI) fly ash have been studied well. However, micro-characteristics of MSWI fly ash particles are still uncertain and might be non-negligible to describe their leaching behaviors. Therefore, this study investigated micro-characteristics of MSWI fly ash particles, especially their structural properties and impacts of chelate treatment on surface characteristics. According to SEM observations, raw fly ash particles could be categorized into four types based on their shapes. Because chelate treatment changed the surface of fly ash particles dramatically owing to secondary mineral formations like ettringite, two more types could be categorized for chelate-treated fly ash particles. Acid extraction experiments suggest that fly ash particles, tested in this study, consist of Si-base insoluble core structure, Al/Ca/Si-base semi-soluble matrices inside the body, and KCl/NaCl-base soluble aggregates on the surface. Scanning electron microscope (SEM) observations of the same fly ash particles during twice moistening treatments showed that KCl/NaCl moved under wet condition and concentrated at different places on the particle surface. However, element mobility depended on secondary mineral formations. When insoluble mineral like gypsum was generated and covered the particle surface, it inhibited element transfer under wet condition. Surface characteristics including secondary mineral formation of MSWI fly ash particles are likely non-negligible to describe trace element leaching behaviors.


IMPACT OF SECONDARY MINERAL FORMATION ON IMMOBILIZING HAZARDOUS ELEMENTS FOR MUNICIPAL SOLID WASTE INCINERATION FLY ASH PARTICLES

January 2015

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14 Reads

Journal of Japan Society of Civil Engineers Ser G (Environmental Research)

Mineralogical and physical immobilization effects of secondary minral formation by chelate treatment for hazardous elements contained in municipal solid waste incineration (MSWI) fly ash particles were investigated. SEM observation showed that ettringite, which can incorporate heavy metals into its structure, was generated on the surface of fly ash particles after chelate treatment. However, SEM-EDX analysis could not find concentrated spots of hazardous elements on ettringite. This means that mineralogical immobilization of hazardous elements by ettringite is negligible. The same MSWI fly ash particles were observed before and after the moistening treatment in order to investigate physical immobilization effect. These observation showed that soluble components transferred on fly ash particle surfaces and such elemental transfer was inhibited by insoluble mineral formation like gypsum. This means that physical immobilization by insoluble secondary mineral formation can contribute to hazardous elements immobilization to some extent. However, such mineralogical and physical immobilization by secondary mineral formation, which is promoted by fly ash moistening owing to chelate treatment, were limited. Therefore, toxic element immobilization by chelate treatment and its stability would depend mainly on the stability of complexation between toxic elements and chelate reagent.

Citations (7)


... When the content of diatomite is more than 5%, the increase in cohesion is relatively low because the cement and soil, cement and diatomite, and diatomite and soil in the specimen fully react. The continuous increase in the content mainly plays the role of filling the pores [39]. ...

Reference:

Experimental Study on the Mechanical Properties of Diatomite-Modified Coastal Cement Soil
Impact of diatomite addition on lead immobilization in air pollution control residues from a municipal solid waste incinerator

Environmental Science and Pollution Research

... The phase is Mantovani et al. (2021). Last, ZnCl 2 was found only in one spectrum (Zn2_1); this compound was found mainly in FA (Cai et al., 2015;Kitamura et al., 2020) but also in BA where its presence can be explained by the encapsulation of chloride within sintered BA particles (Rissler et al., 2020). ...

Application of micro-scale correlation analysis to estimate metal speciation and the matrix in municipal solid waste incineration fly ash
  • Citing Article
  • February 2020

Journal of Material Cycles and Waste Management

... Despite the significant features of MSWI technology in terms of non-hazardousness, minimization, and resource utilization, the process still emits various pollutants [31]. The MSW with complex compositions gradually decreases in size, and eventually forms PM after fracture, pyrolysis, and oxidation in the furnace [32,33]. PM is mostly irregularly shaped aggregates, with relatively few spherical bodies, rod-like aggregates, and flocculent aggregates. ...

Heterogeneities of fly ash particles generated from a fluidized bed combustor of municipal solid waste incineration
  • Citing Article
  • January 2020

Journal of Material Cycles and Waste Management

... Other countries (e.g., Japan) rely on MSWI methods at higher temperatures (> 1200 °C), targeting the complete destruction of organic pollutants (e.g., dioxin, furan) and the vitrification of the incineration residues (Ecke et al. 2000;Tanigaki et al. 2012;Shiota et al. 2017). MSWI represents a heterogeneous treatment process, which is heavily influenced by the waste input and local temperature gradients in the furnace during the incineration, which result in MSWI residues of variable chemical and mineralogical composition (Chang et al. 2001;Kitamura et al. 2019;Huber et al. 2020). ...

Intra- and inter-particle heterogeneity of municipal solid waste incineration fly ash particles
  • Citing Article
  • March 2019

Journal of Material Cycles and Waste Management

... Its primary sources are the combustion and emissions resulting from vehicles powered by fuel, as well as the degradation of automotive components [28]. The primary constituents found in PM 2.5 consist of black carbon, polycyclic aromatic hydrocarbons (PAHs), aryl hydrocarbons, volatile organic hydrocarbons, heavy metals, organic compounds, minerals, inorganic ions, and biological materials [29][30][31][32][33][34][35][36]. Collectively, these components account for a minimum of 79-85% of the total mass [37]. ...

Impact of secondary generated minerals on toxic element immobilization for air pollution control fly ash of a municipal solid waste incinerator

Environmental Science and Pollution Research

... Because SEM-EDX measurement was semi-quantitative owing to no specific calibration, it is noted that comparison of elemental concentrations shown in Fig. 6 still needs careful verification for a solid conclusion. After JLT46 and TCLP, XRD patterns of soluble components such as sylvite and halite disappeared owing to leaching out (see Fig. 7; Kitamura et al. 2017). On the other hand, Al/ Ca/Si-based minerals such as gehlenite (Ca 2 Al 2 SiO 7 ) were identified. ...

GEOCHEMICAL FORM ANALYSIS OF TITANIUM IN CHELATE-TREATED MUNICIPAL SOLID WASTE INCINERATION FLY ASH PARTICLES EMPLOYING CORRELATION ANALYSIS OF ELEMENTAL DISTRIBUTION LINE PROFILES
  • Citing Article
  • January 2017

Journal of Japan Society of Civil Engineers Ser G (Environmental Research)

... Specifically, numerous studies have focused on the leaching behavior of potentially toxic elements (PTEs), factors affecting it, and mitigating approaches [5,12,[14][15][16][17][18]. In addition, quite a few studies have focused on the physical, chemical, mineralogical, and morphological properties of MSWI BA [4,7,[19][20][21][22][23][24][25]. Over the years, many treatments have been suggested to minimize the adverse effects of this material if it is recycled as aggregates, road-base materials (coarse fractions) or cement replacement (fine fractions), such as thermal treatment, metal extraction to reduce the leaching, particle size separation, carbonation, etc. [10,[26][27][28][29][30]. ...

Geochemically structural characteristics of municipal solid waste incineration fly ash particles and mineralogical surface conversions by chelate treatment
  • Citing Article
  • September 2015

Environmental Science and Pollution Research