Fly Ash Samples Research Articles

Influence of Fly Ash Properties on Characteristics of Manufactured Angular Fly Ash Aggregates

This paper presents the influence of fly ash properties on angular fly ash aggregate (AFAA) and its manufacturing process to be used as a replacement of natural aggregate in concrete. Characteristics of fly ash play an important role in quality of AFAA as fly ash is the major constituent of the raw materials that are used in manufacturing of AFAA. Ample of studies have already been done on production and utilization of round fly ash aggregate (FAA) by pelletization process, but this study deals with innovative work of manufacturing of AFAA by crushing sintered briquettes into required sizes. Unlike round fly ash aggregate, AFAA possesses rough surface that enhance interlocking of these aggregate with paste in concrete. Four different types of AFAA were manufactured in laboratory by using two different samples of fly ash and two different binders. Performance of AFAA showed that specific surface area and chemical composition of fly ash affects sintering behavior of ash and as a result internal microstructure of aggregate also gets affected. Later, eight types of concrete were produced using four types of manufactured FAA at two different water cement ratio 0.45 and 0.50. It was concluded that strength of concrete depends on properties of manufactured AFAA and nature of bond between cement and aggregate at Interfacial transition zone. AFAA used concrete is found to be lighter in weight compared to the concrete of natural aggregate and is economical for use in construction purposes which in turn can save our depleting natural resources and environmental pollution.

Characteristics of fly ash from waste-to-energy plants adopting grate-type or circulating fluidized bed incinerators: a comparative study

ABSTRACT Although the pressure of waste siege was reduced by the development of waste-to-energy (WTE) plants, every year million tons of toxic municipal solid waste incineration (MSWI) fly ash is produced which is regarded as a hazardous waste. In this paper, ten MSWI fly ash samples were collected to analyze the composition, physical properties, leachability of heavy metals, and toxicity of dioxins to obtain a comprehensive evaluation, which has not been discussed in the previous studies. The analysis and comparison of fly ash is based on the main type of incinerators applied nowadays. Due to differences in the incinerator types, there were significant differences observed in the size distribution, microstructure, element content, and crystalline structure of fly ash, which are related to the heavy metal leachability and dioxin toxicity. The heavy metal leaching toxicity of nine fly ash samples failed to meet the requirements of the landfill regulations. The main heavy metals above an unacceptable level are Pb (4.271 mg/L) in the grate-type fly ash and Cd (1.035 mg/L) in the circulating fluidized bed (CFB) fly ash. Furthermore, the I-TEQ concentrations of dioxins of two CFB fly ash (3.207 and 3.212 ng I-TEQ/g) exceeded the limit value. The main contribution to the dioxin concentrations of the fly ash is from OCDD (18.7–64.3%), and the main contributor to the I-TEQ (international toxicity equivalent quantity) value is 23478-PeCDF (range 33.0 to 43.2%). In addition, correlation between compositional analysis and toxicity indexes was discussed carefully. The findings in this work can provide directions for the disposal and utilization of the fly ash from different incinerators, which can be beneficial for MSWI fly ash management.

Mössbauer and X-ray Studies of Phase Composition of Fly Ashes Formed after Combustion of Ekibastuz Coal (Kazakhstan)

Mössbauer spectroscopy and X-ray diffraction have been used to study samples of fly ashes formed after combustion of coal from the Ekibastuz basin at the thermal power plants TPP-2 and TPP-3 in Almaty (Kazakhstan). It has been established that the fractions of fly ashes contain iron in the form of magnetite Fe3O4 and hematite α-Fe2O3. The mixed valence of iron Fe3+ ↔ Fe2+ in the octahedral sublattice of magnetite is destroyed by isostructural substitution impurities. Maghemite γ-Fe2O3 is additionally present in the fly ash of TPP-3 as a product of magnetite slow oxidation. It was shown that at T ≥ 1400 °C the proportion of magnetite in fly ashes increases due to decomposition of hematite, maghemite, hercynite and the drop of iron content in mullite. It was concluded that the amount of iron in magnetite is a temperature indicator of fly ashes formation. The parameters of hyperfine interactions have been determined in the iron-containing minerals of fly ashes. It was identified that formation of the fly ashes structure occurs in oxidizing atmosphere, since no traces were revealed of reducing environment effect on the phase composition.

Cr(VI) Leached from Lignite Fly Ash—Assessment of Groundwater Contamination Risk

The leaching of Cr(VI) from lignite fly ash was investigated by means of experimental standards and theoretical simulations. Two lignite fly ash samples with different calcium oxide concentration were examined. Acid extraction of fly ash and batch leaching tests were performed at various liquid (water) to solid (fly ash) ratios (L/S) for the estimation of Cr(VI) leaching rate. The mobility of Cr(VI) in soil and soil’s hydraulic conductivity at different temperatures was also examined. The results indicate that chromium in fly ash occurs mainly in its trivalent form and that Cr(VI) can be leached, but at lower degree. Along with Cr(VI), the strong reducing agent Fe(II) is also leached. A portion of the Cr(VI) is readily leached, while several hours are needed for reaching Cr(VI) equilibrium concentration in leachate. The fly ash hydraulic conductivity is greatly affected by its pozzolanic characteristics, decreasing from around 10 mm/h (2.78 × 10−6 m/s) to values lower than 1 mm/h (2.78 × 10−7 m/s) in few hours. In continuous leaching tests, relatively low Cr(VI) concentrations (< 20 μg/L) were detected, while in batch leaching tests with higher water/fly ash contact time, leachate Cr(VI) concentrations up to 700 μg/L were detected depending on the applied L/S ratio. However, for low L/S (0.5–1) ratios, no leachate was obtained. Theoretical calculations were performed in order to estimate the L/S ratios at real conditions (by taking into account the volume and the surface of an ash disposal, the density of ash, the hydraulic conductivity of ash, rainfall rate, and rainfall duration). It was found that in real conditions, high L/S can be obtained only when various specific conditions are fulfilled. Experiments with soil showed that only a small portion (approximately 4%) of the leached Cr(VI) can pass through a relatively thin (12–15 cm) layer of soil, even at low temperatures. Based on the experimental results and the groundwater and surface water quality data of a studied basin, a low contamination risk due to Cr(VI) leaching from lignite fly ash is assessed.

Characterization of feed coals and coal combustion byproducts from the Wyodak-Anderson coal zone, Powder River Basin, Wyoming

The U.S. Geological Survey (USGS) determined the physical and chemical properties of more than 260 feed coal and coal combustion byproducts from two coal-fired power plants. These plants utilized a low-sulfur (0.23-0.47 wt. % S) and low ash (4.9-6.3 wt. % ash) subbituminous coal from the Wyodak-Anderson coal zone in the Tongue River Member of the Paleocene Fort Union Formation, Powder River Basin, Wyoming. Fifty-three samples of bituminous coal were collected and analyzed from a Kentucky power plant, which used several sources of bituminous coals from the Appalachian and Illinois Basins. Based on scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses of feed coal samples collected and analyzed from 1996 through the late 2000s, two mineral suites were identified: (1) a primary or detrital suite consisting of quartz (including beta-form grains), biotite, feldspar, and minor zircon; and (2) a secondary authigenic mineral suite containing alumino-phosphates (crandallite and gorceixite), kaolinite, carbonates (calcite and dolomite), quartz, anatase, barite, and pyrite. The detrital mineral suite is interpreted, in part, to be of volcanic origin, whereas the authigenic mineral suite is interpreted, in part, to be the result of the alteration of the volcanic minerals. The mineral suites have contributed to the higher amounts of barium, calcium, magnesium, phosphorus, sodium, strontium, and titanium in the Powder River Basin feed coals in comparison to eastern US coals. XRD analysis indicates that (1) fly ash is mostly aluminate glass, perovskite, lime, gehlenite, quartz, and phosphates with minor amounts of periclase, anhydrite, hematite, and spinel group minerals; and (2) bottom ash is predominantly quartz, plagioclase (albite and anorthite), pyroxene (augite and fassaite), rhodonite, and akermanite, and spinel group minerals. Microprobe and SEM analyses of fly ash samples revealed quartz, zircon, and monazite, euhedral laths of corundum with merrillite, hematite, dendritic spinels/ferrites, wollastonite, and periclase. The abundant calcium and magnesium mineral phases in the fly ash are attributed to the alteration of carbonate, clay, and phosphate minerals in the feed coal during combustion. The calcium- and magnesium-rich and alumino-phosphate mineral phases in the coal combustion byproducts can be attributed to volcanic minerals deposited in peat-forming mires. Dissolution and alteration of these detrital volcanic minerals occurred either in the peat-forming stage or during coalification and diagenesis, resulting in the authigenic mineral suite. The presence of free lime (CaO) in fly ash produced from Wyodak-Anderson coal acts as a self-contained “scrubber” for SO3, where CaO + SO3 form anhydrite either during combustion or in the upper parts of the boiler. Considering the high lime content in the fly ash and the resulting hydration reactions after its contact with water, there is little evidence that major amounts of leachable metals are mobilized in the disposal or utilization of this fly ash.

Hydraulic conductivity of fly ash as a barrier material: some problems in determination

Recently, researchers have conducted investigations with the possibility of utilising fly ash as a barrier material, which is justified by its chemical, physical and mechanical properties. The mean necessary characteristic, which should be tested is coefficient of permeability. The diversification of test methods and sample preparation techniques can significantly change test results. The purpose of the article is to describe the fly ash permeability in dependence on compaction and moisture content at compaction, as a material embedded into the sealing layer of storage yards. The impact of sample saturation on hydraulic conductivity is shown too. The hydraulic conductivity was investigated for unsaturated and fully saturated fly ash samples, which had been compacted by the Standard and Modified Proctor methods at various water contents, ranging over optimum water content ± 5%. The lowest values of hydraulic conductivity were obtained at the highest moisture contents w = wopt + 5%, for both compaction methods. It is proven that compacted fly ash, in spite of its likeness to non-cohesive soils, must be assessed while considering water content during compaction, as in the case of compacted cohesive soils.

Effect of Additive Material on Controlling Chromium (Cr) Leaching from Coal Fly Ash

Coal fly ash contains a considerable number of toxic elements that can be leached into the environment, such as chromium (Cr), thereby quickly leading to severe contaminations. In this research, the leaching behaviors of Cr were analyzed from 14 kinds of coal fly ash samples collected from the electrostatic precipitators of coal-fired thermal power plants in Japan. The level of Cr concentration found in the samples varied from 0.00 to 82.93 μg/L. However, Cr toxicity depends on its valence state; Cr6+ is more toxic than Cr3+. Additive materials containing high calcium content were used to control the leaching concentration of Cr, such as Ca(OH)2, paper sludge ash, and blast furnace cement. This research used several instruments. An X-ray fluorescence was adopted to measure the major chemical composition of the fly ash samples and the additive materials. A thermogravimetric analyzer was used to examine the calcium compounds in the additive materials. Inductively coupled plasma was used to determine the Cr leaching concentrations from the fly ash samples. Findings showed that the three-additive mixture had a promising effect on controlling the Cr leaching concentrations. These results were also supported by FactSage 7.2 simulation.

Assessment of natural radioactivity and radiation hazards owing to coal fly ash and natural pozzolan Portland cements

The natural radioactivity in coal fly ash and natural pozzolan Portland cement samples produced in Spain was measured by gamma spectrometry. Activity concentrations of 226Ra, 232Th and 40K ranged from 15.7 to 88.3 Bq kg−1, from 12.8 to 81.0 Bq kg−1 and from 37.0 to 678.0 Bq kg−1, respectively. The radiological hazards samples owing to the mentioned natural radioactivity were inferred from determinations of the activity concentration index, I, absorbed dose rate, Dext, and annual effective dose, Ep, which falls within 0.20 mSv to 0.87 mSv (coal-cement) and 0.18 mSv to 0.50 mSv (pozzolan-cement) (≤ 1 mSv, threshold criterion). Therefore, these cements are proper to be used for building purposes as result of their radiological assessment.

Coal Fly Ash Characterization from Cement Industry “X” as an Initial Study in Its Utilization

The discharge of fly ash from the coal combustion process has become a matter of concern over the last few decades. Most of the fly ash will be disposed of in the landfill. This disposal gives a negative impact on the environment through the heavy metal contained in fly ash. Coal fly ash characterization is needed to be done to get proper information about coal fly ash before it could be utilized. In this research, coal fly ash characterization from one of cement industry in Indonesia has been done by a qualitative and quantitative method. This research carried out some instrumentation such as Scanning Electron Microscopy (SEM), X-ray fluorescence spectrometer (XRF) and SEM – Electron Dispersive X-ray spectroscopy (SEM-EDX) to analyze the coal fly ash sample. The result showed that the main component in this coal ash sample is SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, and MgO. This information will be used as an initial study in coal fly ashes utilization research in the next research.

Assessment and Characterization of Mine Waste and Fly Ash Material for Effective Utilization in Opencast Coal Mines

Coal is a major source of nonrenewable energy in India. Most of the Industries depend on the coal to meet the energy demand of the country. Coal mining is invariably associated with the generation of voids. The voids so generated are often filled with overburden (OB) and waste materials. To enhance the utilization, fly ash (FA) is also being used for filling the voids. However, these operations inevitably require excessive planning and control to minimize the environmental impact of mining. In order to evaluate the impact of backfilling the voids with coal mine wastes and fly ash, Overburden and fly ash materials have been collected from Talcher coalfield. The geotechnical characterization study of overburden (OB) sample and OB+30% fly ash samples have been carried out separately for backfilling. After addition of fly ash, it is observed that the permeability is increased but liquid limit, plastic limit, and plasticity index (PI) of the OB are decreased. The maximum dry unit weight of OB mixture decreases while optimum water content increases with the fly ash. The angle of internal friction of OB decreases after addition of the fly ash. Cohesion value of OB sample has not changed much after addition of the fly ash. The grain size analyses results show OB sample is poorly graded. The OB soil type is found to be poorly graded sand of low compressible clay (SP-CL). Similarly, the OB+30% fly ash soil type is of poorly graded sand of low compressible silty (SP-ML) type. The OB and OB+ 30% fly ash contain heavy metals such as Fe and Al in high quantity, mild concentrations of Zn, Cr, and Mn and low amounts of Cu, Co, As, and Se. B and Pb are found below the detection level. The decreasing order of heavy metals in the leachate samples observed to be Fe&gt;Mn&gt;Ni&gt;Cu&gt;Zn&gt;Se&gt;Co&gt;Cd&gt;Cr&gt;As. The major mineral phases in OB and OB+30% fly ash samples are found to be quartz, kaolinite, muscovite, dickite, zinnwaldite, and illite.

Influence of mercury retention on mercury adsorption of fly ash

Estimating mercury adsorption capability plays a vital role in verifying whether fly ash could act as a good sorbent for mercury removal. In this work, mercury retention in fly ash is considered to study its effect on mercury adsorption capacity. Six fly ash samples are collected from six different full-scale coal-fired power plants. The mercury adsorption ratio is measured by adsorption tests to characterize mercury adsorption capability of fly ash. The mercury retention in coals and their corresponding fly ashes are also examined. The results show that there is no linear correlation for fly ash between mercury retention ratio and mercury adsorption ratio Such phenomenon results from the fact that mercury retention ratio is determined by mercury adsorption properties of fly ash and mercury concentration of flue gas. The mercury species adsorbed from flue gas occupy the active sites of fly ash, which decrease the adsorption capability of fly ash. However, each as-received fly ash is surrounded with different mercury concentrations of flue gas. Even though two fly ashes have the same active sites for adsorbing mercury, they have different number of occupied active sites for mercury adsorption after flowing along with flue gas. Hence, evaluating the intrinsic mercury adsorption properties of fly ash should pretreat the fly ash samples before adsorption tests by removing out the adsorbed mercury to recover the occupied active sites, with which it may be reasonable to truly manifest the mercury adsorption properties of fly ash.

Geochemical and magnetic data on anthropogenic ashes from municipal solid waste incineration (MSWI).

This paper reports supplementary information to “Understanding room-temperature magnetic properties of anthropogenic ashes from municipal solid waste incineration to assess potential impacts and resources” [1]. The sample-set is composed of 47 samples of bottom (BA) and fly (FA) ashes from Municipal Solid Waste Incineration (MSWI), including eight magnetic extracts of selected BA and FA materials. The sampling relies on a simple random sampling strategy at four different MSWI sites in Northern Italy [2]. X-Ray Fluorescence (XRF) analysis on pressed powder pellets, microscopic observations on thin sections and stubs, and magnetic analysis were carried out.Various magnetic measurements are presented: the magnetic susceptibility measured at two different frequencies (0.47 and 4.7 kHz); the mass-specific susceptibility of ARM (χARM), expressed in m3/kg, calculated after mass-normalization and bias DC field correction; experiments for isothermal remanent magnetization (IRM) experimented were also conducted. The latter measurement allowed the calculation of additional parameters, such as the coercivity of remanence (B0cr) and the S-ratio [3]. The IRM acquired in a field of 1.0 T was regarded as the saturation IRM (SIRM). Mass-specific magnetic susceptibility (χ) was calculated by dividing the volume susceptibility by the sample mass. Finally, hysteresis loops and backfield curves at room temperature were measured on selected samples and are available. Data can be reused as groundwork information in future studies on MSWI residues. It would be essential to produce new data on geochemical and magnetic characteristics of MSWI residues to assure good coverage of data for enhanced sustainability of these heterogeneous streams of anthropogenic materials. This combination of methods will contribute to paving the way for quick and reliable resource assessment as well as to promote environmental sustainability.

A stoichiometric approach to find optimum amount of fly ash needed in cement concrete

This study aimed to find the optimum amount of fly ash that can be replaced with cement using a stoichiometric approach. For this purpose, the balanced chemical reactions between cement, water and fly ash were studied. This new proposed methodology uses information like chemical composition of cement, elemental composition and crystallinity in fly ash sample, and can easily find the optimum amount of fly ash that can replace cement. Considering the chemical composition analysis and percentage crystallinity in fly ash sample, the quantity of fly ash that can replace cement came out to be 30%. To assess the performance of control group and partially replaced cement (PRC) samples, specimens were casted and different tests like compressive strength, split-tensile strength, density and sorption were conducted. The experimental results showed that PRC samples gained almost 95% compressive strength as that of control group at 90 days. The resistance to water intrusion as measured with sorption test showed that PRC samples had almost 50% less depth as compared to control group. The improvement in mechanical and durability properties of PRC samples supports the outcome of studied chemical reactions. The fly ash consumed the cement hydration product i.e. calcium hydroxide for producing binder gel; which enhanced the strength, lowered permeability and made the concrete denser. The development of compressive strength and density with time shows good agreement with an R2 value of 0.96.

Review of the Reuse Possibilities Concerning Ash Residues from Thermal Process in a Medium-Sized Urban System in Northern Italy

This review paper reports a detailed characterization of some combustion or incineration residues and by-products produced in a medium-sized city in Northern Italy. The municipal solid waste incineration (MSWI) generates fly ash, which is a toxic waste. Coal fly ash (CFA) and flue gas desulfurization (FGD) derive from the thermoelectric coal plant located in the same city. Along with these ashes, silica fume and rice husk ash are also considered for the stabilization of fly ash based on their amorphous silica content with the aim to convert them into an inert material. The characterization of all the investigated ashes was performed using different techniques: X-ray diffraction, total reflection X-ray fluorescence, scanning electron microscopy, and transmission electron microscopy. The aim of this work is to describe the reuse possibilities that were proposed for these ashes, which were determined also on the basis of their structural properties. Several possible applications of the investigated ashes are proposed, and the most suitable reuse of stabilized fly ash samples seems to be the production of sustainable plastic composites. This paper shows that the reuse of the by-product materials can allow natural resources to be preserved following the principles of a circular economy.

Geopolymerization of Fly Ashes From 6 Indonesian Power Plants Using A Standardized Recipes

Geopolymers were synthesized using fly ash as raw material from six steam power plants, Adipala (FA1), Indramayu (FA2), Paiton 9 (FA3), Asam-asam (FA4), Pulau Pisang (FA5), and Sanggau (FA6). Fly ash was tested for several characteristics using XRF, XRD, and SEM. XRF analysis showed FA1, FA4, and FA5 included in class C fly ash while FA2, FA3, and FA5 included in class F. The XRD analysis results showed that there were typical peaks of quartz, mullite, calcite, magnetite, and hematite in the fly ash samples. SEM analysis shows the morphology of the fly ash FA1, FA2, FA3, and FA4 spherical with different particle sizes, but in the fly ash FA5 and FA6, the morphological shape is irregular. The highest compressive strength test results obtained by geopolymers made from FA3 after 28 days with compressive strength values of 36.62 MPa. The intensity of the crystalline geopolymer phase decreases when compared to its fly ash. Geopolymer morphology shows the presence of unreacted fly ash particles.

Characteristics of ash and slag from four biomass-fired power plants: Ash/slag ratio, unburned carbon, leaching of major and trace elements

The utilization of biomass energy is attracting worldwide attention due to the worsening energy crisis and the concerns on carbon dioxide emission. However, the rapidly development of biomass-fired power plants generate enormous amount of slag and ash. At present, the main treatment method of biomass slag and ash is landfill, which not only requires high cost, but also causes a series of environmental issues. Aiming at this problem, the slag and fly ash from four biomass power plants were sampled and characterized. The major/trace element composition and leaching characteristics of slag and fly ash are analyzed, and the effect of volatile mineral in these solid residues on furnace efficiency is also evaluated. The results indicate that for biomass-fired grate furnaces, in the generated solid residues, the slag accounts 60 ~ 70% while the fly ash accounts for 30 ~ 40%. The volatile elements in slag are much lower than those in fly ash, and the unburned carbon content of fly ash is generally lower than that of slag. Due to the enrichment of volatile minerals in fly ash, instead of 815 °C, 550 °C is suggested to measure the unburned carbon content in fly ash. When the measuring temperature of unburned carbon decreases from 815 °C to 550 °C, the measured energy loss from the incomplete combustion of solid fuels decreases by one third, which affords a more reasonable evaluation on combustion efficiency. The contents of cadmium and lead in certain fly ash samples exceed the standard, however, all fly ash samples have a high leaching rate of potassium but low leaching rates of copper, zinc, cadmium, lead, chromium and arsenic. It indicates that the fly ash from biomass-fired grate furnace is suitable for producing potassium fertilizer by leaching instead of direct soil fertilization or landfill. The leaching rate of most minerals in slag is much lower than that in fly ash and the contents of heavy metals are far below the prescribed upper limit in standard, which indicates that the slag from biomass-fired grate boiler is more suitable for direct use in soil improvement due to the low contents of hazardous elements.

ANALISIS KANDUNGAN LOGAM BERAT ABU BATUBARA PLTU BANGKO BARAT KAB. MUARA ENIM SUMATERA SELATAN

Coal combustion product (CCP) from Bangko Barat Power Plant is used as landfill material in acidic overburden layers. CCP is categorized as hazardous and toxic waste (PP No.101/2014) from specific sources and is known to contain heavy metals. This study aims to analyze the heavy metal content of coal combustion product from Bangko Barat Power Plant, Muara Enim Regency, South Sumatra Province. Heavy metal content of CCP includes Hg, Cd, Cu, Ag, Ni, Pb, As, Cr, Sn, Zn dan Mn. Heavy metal content analysis to ensure overburden piling by utilizing CCP, either with a long-term safe coating or mixing scheme. The analysis was carried out by using ICP-MS test, XRF test, XRD test, analysis of grain size and grain morphology. Samples of fly ash and bottom ash were categorized as non- hazardous and toxic waste based on the results of the ICP-MS test compared to the values of TK-A, TK-B and TK-C. Heavy metal content that needs attention from coal ash is As (4.4-20 ppm), Cr (26-43 ppm), Cu (30.7-42.6 ppm), Pb (22,2-29,3 ppm), Zn (77.5-128 ppm), Ni (10,6-24,8 ppm) and Mn (144-396 ppm). The content of other heavy metals is relatively low (Hg, Cd, Ag and Sn) and the threshold is not exceeded. Monitoring the quality of runoff water from landfill area using CCP to be controlled so that the heavy metal content does not endanger the health of living things.

Experimental Study of Rare Earth Element Enrichment from Indonesian Coal Fly Ash: Alkaline Leaching

Rare Earth Element plus Yttrium (REY) is an critical element in green technology and consumer goods. Due to its limited supply, it is necessary to look for alternative sources of REY which one of the potential candidates is coal fly ash. Two samples of coal fly ash which originated from Indonesia were leached in an alkaline solution in order to remove Si and increase REY content. Samples were collected from pulverized coal power plant in East Java (sample T) and West Java (sample I). Leaching conditions were studied including concentration of NaOH, ratio of volume of liquid (L) to weight of solid (S) and leaching time. It was found that the optimum condition was reached at NaOH concentration of 8M, L/S ratio (10 mL: 1 g) and leaching time of 120 min. At this condition, percent removal of Si and REY enrichment were respectively 56.22% and 30% for sample I, and 33.75% and 24% for sample T.

Synthesis of activated carbon from high-carbon coal fly ash and its hydrogen storage application

Activated carbons (ACs) have desirable characteristics that make them attractive for many industrial applications. In order to reduce their production cost, there is always a need to find alternative low-cost feedstock precursors. Nowadays zero-waste technologies play an important role in sustainable development, therefore using of coal by-product as source of AC is strongly recommended. In this study, coal fly ash (CFA) sample with a high unburned carbon content was used to synthesize ACs. The effect of acid pre-treatment of the CFA sample using HF and HCl prior to thermochemical activation using KOH was also investigated. The acid washing was found to be effective since it removed most of the inorganic components found in the CFA, as was confirmed by EDS and XRF. The resulting carbon-rich feedstock had relatively high content of meso-/macropores as well as with relative increase in specific surface area (46.19 m2/g - 81.20 m2/g). The obtained AC sample was found to exhibit high specific surface (946.77 m2/g) that was dominated by high microporosity and was tested for hydrogen storage. The H2 uptake (1 bar, 77 K) was found to be 1.35 wt% and with a predictable potential for even higher capacity when measurements are conducted at high pressures.

Crystal Morphology Analysis for Heavy Elements in Municipal Solid Waste Incineration Fly and Bottom Ash by X-ray Characterization Techniques.

The elemental and crystalline phase compositions of fly ash collected before and after spraying of the ash with slaked lime (first and second fly ash) and the bottom ash of municipal solid waste collected at an incineration plant were analyzed using powder briquette by X-ray fluorescence spectrometry and Rietveld refinement by X-ray diffraction. The crystalline and amorphous phase contents were quantified by adding 10% corundum as an internal standard. In the first fly ash, SiO2, Cl, and CaO were the main components, and several thousand ppm (μg/g) of Zn and Pb were detected. Anhydrite, gehlenite, and amorphous phases were the main phases in the first fly ash samples. The components of the first fly ash originated exclusively from the incineration of municipal solid waste in a furnace. The crystal morphologies of the heavy elements in the ash samples were estimated by determining the correlations among the concentrations of all the elements. The heavy elements in the bottom ash showed no strong correlations with other elements; therefore, the heavy elements in the bottom ash were present in an amorphous phase.