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This is an article in the field of ceramics and composites.To explore the feasibility of using coal waste to replace cement for concrete preparation, the activated coal slag powder and coal gangue powder were used to replace cement at a ratio of 0%, 10%, 20%, 30%, and 40% to prepare concrete samples and prepare concrete samples. The slump, compressive strength, flexural strength and high-temperature performance were tested, and the results show that: as the substitution ratio increases, the slump, compressive strength and flexural strength all increase first and then decrease; The optimal substitution ratio is 20%～30%. The early strength growth rate of the activated coal slag powder sample is large; while the long-term strength growth rate of the activated coal gangue powder sample is large. When the water-cement ratio=0.45, the compressive strength of the sample increases first and then decreases with the increase of temperature, and reaches the maximum at 100 ℃; when the water-cement ratio=0.5, the compressive strength of the concrete sample increases with the temperature; the hydration cement structure in the interface area of the activated coal slag powder sample is the most, followed by the control group, and the activated coal gangue powder sample is the least. With the increase in temperature, the pores and cracks on the surface of the sample increased significantly and the degree of fracture of the damaged surface gradually increased.

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This paper aims at synthesizing the scientific research on coal fly ash and agriculture using bibliometric analysis. The research on fly ash and agriculture has grown at 6.7% annually during 1973–2022, where much attention has been received after 2007. The number of publications on coal fly ash and agriculture reached above 100 in the year 2010, which further increased to 299 by 2020. The research productivity has been assessed as the most influential countries, journals, and documents in terms of a number of publications and citations on fly ash and agriculture. India is the most productive country in terms of knowledge on coal fly ash and agriculture with 38% of the global publications, while Environmental Science and Pollution Research is the leading journal with 19 publications. The article on assessing the impact of fly ash incorporation in soil systems by Pandey and Singh (2010), having 349 citations with 26.85 citations per year is one of the leading publications globally. Further, science mapping has been conducted to comprehend the current research focus and discover the emerging themes for future research. The finding of the thematic map based on the level of development and importance indicate that FA can be effectively explored as soil-additive for improved physical, chemical and biological properties and enhanced plant nutrients. The findings provide several aspects of fly ash and suggest future research directions to study the potential of using coal fly ash in agriculture to gain an agronomic advantage. [ABSTRACT FROM AUTHOR]

Coal waste contains few macro-and micronutrients, which makes it less likely to become a growth site for microorganisms. One way to screen coal waste resources is to identify the diversity of microbes in them to study the relationship between these microbial communities in contributing to improving environmental pollution using metagenomics to determine microbial diversity. The purpose of this research is to study the diversity of microorganisms in areas contaminated with heavy metals using a metagenomic method. This study was performed using next-generation sequencing techniques, including DNA extraction, 16S rRNA amplification, and gene sequencing analysis. The results of this research found that the 10 most commonly found species were Baekduia soli, Nocardioides iriomotensis, Nocardioides mesophilus, Nocardioides pakistanensis, Propionibacterium cyclohexanicum, Solirubrobacter ginsenosidimutans, Gemmatirosa kalamazoonensis, Roseisolibacter agri, Kosakonia sacchari, and Dickeya fangzhongdai. Based on this research, it can be concluded that most of the microbial communities from coal waste are dominated by the phylum Actinobaceria. The results of this study can be used as an adaptive microbial germplasm for industrial waste management strategies. [ABSTRACT FROM AUTHOR]

To reduce the environmental damage caused by coal waste landfills, it is necessary to look for rational methods for their management. One method for their development is the creation of soil-like substrates. This study aimed to assess the properties of soil-like substrates from coal mining waste, combined with a varied sample of sewage sludge and waste mineral wool. The properties of the substrates were evaluated in a pot experiment. The properties of the substrates and their yield potential were determined. Coal mining waste as a substrate, compared to anthropogenic soil, was characterized by a significantly higher sorption capacity; the content of alkaline cations and pH; significantly higher contents of organic carbon, nitrogen, and available forms of K and Mg; and a lower content of available P. The substrates enriched with sewage sludge showed a significant increase in content of organic carbon, nitrogen, and assimilable forms of P and Mg, as well as the optimization of sorption properties. Extending the composition of substrates with mineral wool resulted in further improvement of their properties. The yields of plants grown on coal mining waste were significantly lower than those of those grown on anthropogenic soil. Substrates with sewage sludge and mineral wool had a significantly higher yield potential. [ABSTRACT FROM AUTHOR]

A simple mixing-pressing followed by thermal curing and pyrolysis process was used to upcycle coal waste into high-value composites. Three coal wastes of different physicochemical properties were investigated. The hypothetical mechanisms of bonding between the coal particles and the preceramic polymer are presented. The textural properties of the coals indicated that the lowest volatile coal waste (PCD) had a dense structure. This limited the diffusion and reaction of the preceramic polymer with the coal waste during pyrolysis, thereby leading to low-quality composites. The water contact angles of the composites up to 104° imply hydrophobic surfaces, hence, no external coating might be required. Analysis of the carbon phase confirmed that the amorphous carbon structure is prevalent in the composites compared to the coal wastes. The dc volume resistivity of the composites in the range of 22 to 82 Ω-cm infers that the composites are unlikely to suffer electrostatic discharge, which makes them useful in creating self-heating building parts. The leached concentrations of heavy metal elements from the composites based on the end-of-life scenario were below the Toxicity Characteristic Leaching Procedure regulatory limits. Additionally, the release potential or mobility of the metals from the composites was not influenced by the pH of the eluants used. On the basis of the reported results, these carbon/ceramic composites show tremendous prospects as building materials due to these properties. [ABSTRACT FROM AUTHOR]

The spatial heterogeneity of vegetation cover in coal waste pile suggests that the geochemical and biological properties of coal waste are spatially heterogeneous, which contributes to vegetation colonization on tailings. However, whether and how altering the organic matter components and microbial community of coal waste via weathering affects biogeochemical characteristics and vegetation establishment mechanisms remain unclear. Thus, we explored the characterization of dissolved organic matter in coal waste and its biogeochemical implications. Our results highlight coal waste as primary succession for bacterial communities and provide new insights into the bacterial community assembly response to dissolved organic matter and geochemical properties at such sites. Biogeochemical parameters including pH, EC, nutrients, particle size, and enzymatic activities were affected differently by organic components. The electrical conductivity (EC) decreased after decades of natural weathering, whereas pH, moisture, available N and P, urease, phosphatase, soluble microbial byproduct‐like material, humic acid‐like organics, bacterial diversity, and richness increased significantly. Further taxonomical and co‐occurrence network analyses indicated that the primary succession of bacterial communities was strongly influenced by biogenically formed organic components, particle size, and available nutrients. Our results revealed that the humic‐like components facilitated the improved biogeochemical properties and succession of composition and structure of the bacterial community. It demonstrated that weathering‐induced organic matter degradation trigger biogeochemical property improvement and bacterial community succession, and further facilitate the transformation of coal waste into a plant growth substrate. Our results provide a reference for engineering and application practice of utilization and in‐situ remediation ecological reconstruction in coal waste deposits. [ABSTRACT FROM AUTHOR]

Coal waste composed of naturally occurring minerals is applicable as a reactive medium to permeable reactive barriers due to its reactivity to heavy metals. In this study, we evaluated the longevity of coal waste as PRB media to control heavy metal-contaminated groundwater considering variable groundwater velocity. Breakthrough experiments were conducted using coal waste-filled column by injecting artificial groundwater, 10 mg/L of cadmium solution. The artificial groundwater was fed to the column at different flow rates to mimic a wide range of porewater velocities in the saturated zone. The reaction between cadmium breakthrough curves was analyzed using a two-site nonequilibrium sorption model. The cadmium breakthrough curves showed a significant retardation, which increased with decreasing porewater velocity. The greater the retardation, the longer the longevity of coal waste could be expected. The greater retardation under a slower velocity environment was due to the higher fraction of equilibrium reaction. The nonequilibrium reaction parameters could be functionalized with respect to the porewater velocity. The simulation of contaminant transport using the reaction parameters could be used as a method to evaluate the longevity of the pollution-blocking material in an underground environment. [ABSTRACT FROM AUTHOR]

Processing of coal waste to produce concentrates of rare and rare earth metals is considered. These metals are in high demand for fifth-generation sectors such as microelectronics and green technology and sixth-generation sectors such as biotechnology and smart technologies. Given the need for rapid development of these sectors and the need for 100% recycling of Russian coal waste, the extraction of valuable metals from coal waste is of particular importance. Accordingly, the metal content of Siberian and Far East coal wastes is analyzed. They are compared with the exceptional metal content of Shubarkol coal (Kazakhstan). The metal content of coal from the Pavlovsk deposit (Primorsky Territory) is particularly striking. The extraction of rare and rare earth metals from coal ash and cake ash at enrichment plants in the Kuznetsk Basin, Khakassia, Buryatia, and Khabarovsk Territory is very promising. The factors affecting the metal content of coal may be ranked as follows (in descending order): epigenetic, endogenous, metamorphic, and syngenetic factors. Rare metals whose content matches and even exceeds the limiting permissible concentration are identified. Price analysis confirms the excellent prospects for the extraction of rare metals from coal waste. [ABSTRACT FROM AUTHOR]

Energy and environmental protection are two major problems that are faced by the current generation. Coal has been utilized traditionally as a source of electricity globally. However, more ash is generated from the combustion of coal which is carried by gases and precipitated into fly ash. The main problem with fly ash is that, if it is not properly disposed it may cause pollution(s) in the water and soil, which in turn disturb ecological cycle and have negative impact on the environment. Based on the above statement(s), more efforts have been done to recycle fly ash or its utilization for advanced applications. One of the preferred methods for recycling fly ash, is to incorporate it in polymer matrices in order to improve the strength of polymer matrices for advanced applications. Fly ash has been utilized as a reinforcing filler for various polymer matrices due to its high strength and low cost. This review paper discusses different fabrication methods for fly ash/polymer matrices composites. The effect of particle size, modification, synergy of fly ash with other fillers reinforced polymer matrices on the mechanical properties are discussed. Furthermore, there is an in-depth discussion about the specific applications of fly ash reinforced with different polymer matrices. There is also a discussion based on the fly ash/fiber/polymer hybrid composites in relation to the preparation method and mechanical properties, since hybrid systems are known for better properties than single fillers.

This study assessed the viability of the combined use of coal processing waste (CPW), rice processing waste (RPW), poultry agro-industry sludge (PAS), synthetic gypsum (SG), topsoil (TS), and B horizon soil (BH) to reclaim areas degraded by coal mining. A Classification, Potentiality, Quantity/viability, and Application (CPQvA) systematic was employed to assess the feasibility of using these waste and materials to construct technosols. An experiment consisting of five technosols (T-1–T-5) was replicated four times in a completely randomized block design. Technosols fertility was analyzed 12 months after the establishment of the experiment. The mean fertility parameters, presented as mean ± 1 SD, were subjected to one-way analysis of variance, and the differences were tested using Tukey's test (P

Recent attempts to produce effective adsorbents for wastewater treatment purposes have led to development of multiphase nanocomposite consisting of a bed, nanoparticle enhancer(s) and one or more polymeric modifiers. However, availability and final price have been always prohibitive factors challenging the wide application of many of multiphase adsorbents. In this research work, a novel bipolymeric/Fe3O4 nanocomposite loaded on coal tailings was synthesized using a two-step procedure and evaluated as a potential low-cost adsorbent for treating synthetic wastewater polluted by heavy metals. Starting material and synthesized quadriphase nanocomposite were characterized using different instrumental analysis techniques. The adsorptive capacity of the nanocomposite was assessed using response surface methodology (RSM) by considering the nanocomposite-to-cadmium ratio (7–233) and initial pH of solution (3–11) as operating factors and cadmium removal as process response. The significance of the effect of operating variables on removal efficiency was assessed and confirmed using analysis of variance (ANOVA) method. The maximum cadmium removal of 99.30% was obtained under optimum conditions including pH of 10 and quadriphase nanocomposite/cadmium ratio of 40 after 2 h of adsorption. Kinetics and multistep adsorption studies showed that an optimum adsorption of 97% could be obtained only after 1.2 min following a first-order single-step process. Isotherm plots revealed that cadmium adsorb as monolayer on the surface of synthesized quadriphase nanocomposite based on Temkin model with the highest correlation coefficient of 97.67% and the least relative error of 16.15%. [ABSTRACT FROM AUTHOR]

Abstract—The processing of coal waste is considered. There is a clear need to increase the recycling of coal waste in Russia, on the basis of innovative technology. The content of nonferrous metals, rare metals, and rare-earth metals is analyzed at three levels: in coal; in coal ash, coal slag, and cake; and in fly ash and cake ash. The concentrations of some noble metals (silver), rare metals (cadmium, selenium, titanium, rubidium, and tantalum), and rare-earth metals (lanthanum, neodymium, and gadolinium) are found to be close to the values recommended for further evaluation in coal. Elevated concentrations in coal waste are noted for other metals: molybdenum (nonferrous metal), lithium, niobium, germanium, and scandium (rare metals); and praseodymium, yttrium, ytterbium, and samarium (rare-earth metals). The need to extract valuable metals from coal waste is confirmed, especially for fly ash and cake ash. Price analysis of rare and rare-earth metals establishes that their extraction from coal waste is promising. The case is made for assessing the overall impact of processing coal waste, taking account of economic, social, environmental, and indirect effects. By comprehensive processing of coal waste, metal concentrates and associated products may be derived on the basis of innovative methods. [ABSTRACT FROM AUTHOR]

Leveraging natural waste materials for inorganic contaminant removal in solution offers a novel approach to boost resource recycling and foster sustainable development by enhancing waste use. This research advanced the modest arsenite (As[III]) removal capacity of raw coal gangue through a magnesium-soaking and calcination-based surface modification. Batch experiments showed As(III) removal efficiency was improved from 39.8% to 89.9% after modification, independent of initial pH levels. The Langmuir model estimated the maximum sorption capacity of 0.979 mg/g for the modified coal gangue. Physicochemical analyses confirmed that the modification increased the surface area, pore volume and size of the coal gangue. Furthermore, SEM, and subsequent TEM and SAED analyses identified acicular arsenic trioxide (As 2 O 3) on the modified gangue, enhancing As(III) removal. Variations in sorption kinetics hinted at precipitation, likely due to AsO 3 polymer chains formed by As(III)'s sorption onto Mg(OH) 2 , created from MgO hydration in aqueous conditions. Our findings show that coal gangue has potential applications in the development of sustainable methods for waste recycling. [Display omitted] • Granular coal gangue (GCG) can be used as a recycling waste resource for effective As(III) removal. • As(III) removal can be enhanced by surface modification of GCG with Mg sorption and calcination. • Increased sorption sites and facilitated precipitation enhanced As(III) uptake by modified GCG. [ABSTRACT FROM AUTHOR]

Iron removal via jarosite precipitate formation is a commonly used technique in various hydrometallurgical processes. Excess iron removal often becomes essential to an overall metal recovery circuit. This is particularly important to processes involving iron-bearing minerals. A technique, which involved the use of pyrite to generate acid for leaching, for iron removal is critical to enabling the process. Iron removal using CaO or similar reagents is expensive and often results in lost product. In the present study, various compounds that facilitate jarosite formation, namely Na2SO4, NH4OH, KCl, and KOH, were utilized and their effect in precipitation was observed. Visual Minteq assisted simulations were run in order to evaluate favorable conditions for iron removal. Morphology and elemental composition of precipitates were analyzed using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, and the phase purity was identified using X-ray diffraction analysis.

Energy and environmental protection are two major problems that are faced by the current generation. Coal has been utilized traditionally as a source of electricity globally. However, more ash is generated from the combustion of coal which is carried by gases and precipitated into fly ash. The main problem with fly ash is that, if it is not properly disposed it may cause pollution(s) in the water and soil, which in turn disturb ecological cycle and have negative impact on the environment. Based on the above statement(s), more efforts have been done to recycle fly ash or its utilization for advanced applications. One of the preferred methods for recycling fly ash, is to incorporate it in polymer matrices in order to improve the strength of polymer matrices for advanced applications. Fly ash has been utilized as a reinforcing filler for various polymer matrices due to its high strength and low cost. This review paper discusses different fabrication methods for fly ash/polymer matrices composites. The effect of particle size, modification, synergy of fly ash with other fillers reinforced polymer matrices on the mechanical properties are discussed. Furthermore, there is an in-depth discussion about the specific applications of fly ash reinforced with different polymer matrices. There is also a discussion based on the fly ash/fiber/polymer hybrid composites in relation to the preparation method and mechanical properties, since hybrid systems are known for better properties than single fillers. [ABSTRACT FROM AUTHOR]

Cake ash from the Chernogorskaya (Khakassia), Tugnuiskaya (Buryatia), and Chegdomyn (Khabarovsk Territory) enrichment facilities is analyzed, as well as ash from the coal sent to those enterprises. Numerous rare and rare-earth metals are present in elevated concentrations in the ash of the coal and the ash of the coke. The coal waste contains the metals previously observed in waste from Kuznetsk Basin coal. In addition, the samples of coal ash and coal cake analyzed here have concentrations of other rare metals (rubidium and scandium) and rare-earth elements (yttrium and cerium) that are close to the values recommended for industrial assessment in coal. Promising technologies for the extraction of rare and rare-earth elements from coal and coal waste are considered. Potential applications are identified for the metals of practical interest. Indices are proposed for economic assessment of projects aimed at extracting rare and rare-earth metals from coal waste. [ABSTRACT FROM AUTHOR]

The aim of this research was to evaluate the technoeconomic prospect of hydrochar production through co-hydrothermal carbonization of coal waste (CW) and food waste (FW). A process flow diagram was developed that considered seven reactors, six pumps, and other necessary equipment for producing 49,192 kg/h hydrochar. Three different cases were considered for the economic analysis. Case II considered both CW and FW transportation cost while cases I and III considered only FW and only CW transportation, respectively. The economic analysis revealed the break-even costs to be $62.24 per ton for case I, $69.90 per ton for case II, and $60.26 per ton for case III. The fixed capital investment (FCI) was $11.4M for all the cases while total capital investment (TCI), working capital (WC), and manufacturing costs were higher for case II compared to cases I and III. A sensitivity analysis examined the effect of nine different variables on the break-even cost. The raw materials' cost as well as their transportation costs significantly affected the corresponding break-even cost. Additionally, increasing the hydrochar production capacity has drastically decreased the break-even cost. However, the analysis also revealed that excessive increase of production capacity can have negative impact on the process economics. [ABSTRACT FROM AUTHOR]

The goal of this study was to upgrade fuel properties of two different bituminous coal wastes (CW) by reducing their ash, sulfur, and chloride content through co-hydrothermal carbonization (co-HTC) with food waste (FW). CW and FW were mixed in 1:1 (dry wt. basis), ratio and co-HTC experiments were performed at three different temperatures of 180, 230, and 280 °C for 30 min. Mass yield, proximate and ultimate analyses, energy content, and combustion indices of hydrochars were evaluated for the fuel properties. Results showed that co-HTC at 230 °C produced hydrochar with maximum fixed carbon, elemental carbon, and higher heating value (HHV), as well as minimum sulfur and ash for both CW samples. At 230 °C, the elemental carbon of co-HTC hydrochar was increased to a maximum of 46.7 and 49.5%, and the energy content increased to 22.4 MJ/kg and 23.0 MJ/kg for CW1FW (co-HTC hydrochar of CW1 and FW) and CW2FW (co-HTC hydrochar of CW2 and FW), respectively. Additionally, the presence of FW in the treatment process reduced the sulfur content to 2.1 and 1.4% compared with the raw CW values of 9.6 and 8.5% for CW1 and CW2, respectively. Combustion indices also indicated that CW2FW-H230 hydrochar had combustion indices similar to bituminous coal. [ABSTRACT FROM AUTHOR]

Iron removal via jarosite precipitate formation is a commonly used technique in various hydrometallurgical processes. Excess iron removal often becomes essential to an overall metal recovery circuit. This is particularly important to processes involving iron-bearing minerals. A technique, which involved the use of pyrite to generate acid for leaching, for iron removal is critical to enabling the process. Iron removal using CaO or similar reagents is expensive and often results in lost product. In the present study, various compounds that facilitate jarosite formation, namely Na2SO4, NH4OH, KCl, and KOH, were utilized and their effect in precipitation was observed. Visual Minteq assisted simulations were run in order to evaluate favorable conditions for iron removal. Morphology and elemental composition of precipitates were analyzed using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, and the phase purity was identified using X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

This paper focuses on the experimental study and comparative analysis of characteristics, boundary conditions and ignition behavior of slurry fuels prepared from peat, coal processing waste (slime and filter cake), and lignite. Waste turbine oil (with a fraction of 10%) was an additional combustible component. The use of waste oils in waste-derived blends can provide a significant increase in the integral characteristics of fuel ignition as well as increase its calorific value. We measured the ignition delay times, duration of burning, ignition temperatures, peak combustion temperatures, and emissions of sulfur and nitrogen oxides. These characteristics are fundamental for designing the production areas involving fuel supply, atomization, and combustion, as well as flue gas treatment. The experiments were conducted using a lab-scale furnace and small fuel portions. The relative efficiency ratios (considering energy, environmental, and cost criteria) of waste-derived blends were evaluated relative to conventional fuels, such as coal and fuel oil. We established that the most promising fuel slurries have a heterogeneous composition and consist of milled coal, slime, and peat. The averaged efficiency indicator of the studied mixtures varies in the range of 1.6–9.5 (versus coal) and 3.9–30.2 (versus fuel oil). In accordance with experimental data and calculations, the fuel consisting of 30% filter cake, 20% coal slime, and 50% water has the greatest potential in terms of a combination of energy, environmental, and cost criteria. The data obtained can be used to develop waste-to-energy technologies as well as to rationalize the involvement of low-rank fuels and wastes into the energy sector. [ABSTRACT FROM AUTHOR]

This article provides information about the method of obtaining potassium humate obtaining from brown coal of the Lenger deposit, and also describes the elemental and mineralogical composition of potassium humate determined with SEM (JSM-6490l V, Jeol). Kinetic data on the decomposition of brown coal with solutions of potassium hydroxide are presented. The area of chemical reactions and the activation energy is determined. To determine the accuracy of the process of obtaining potassium humate from Lenger coal waste with the accuracy of experimental data, methods of mathematical planning were used, quadratic functions were established. The advantage of obtaining potassium humate is that they are environmentally safe and have high bioactivity. They are also characterized by a high content of humic substances that are involved in the structure formation of the soil, accelerate biochemical processes, and increase the physical and chemical characteristics in the soil. Under the influence of humate-containing substances, the function of microflora elements in the soil is activated, and the number of beneficial microorganisms increases. [ABSTRACT FROM AUTHOR]

Coal processing waste is generated annually in large volumes by the coal exporting countries. More than 70% of run-of-mine coal is enriched. At the same time, typical coal processing waste (slime, flotation waste, mid-coal and tailings) make up at least 10–15% of the raw coal mass. Approximately 220–300 million tons of coal processing waste is generated annually at coal-preparation plants in Russia and China. The results of experimental researches in recent years illustrate the growing interest in such wastes as promising energy components. In this paper, we performed a comparative analysis of the main physical properties, ignition and combustion characteristics of several types of coal processing waste. The comparison is made for typical flotation waste (filter cakes or coal slime) generated in Russia and China. It is shown that for wastes from different countries the ignition delay times differ by no more than 50% and the heat of combustion by 9–15%. Concentrations of main anthropogenic emissions were determined. Generalization is made using criterion expressions to illustrate the advantages and disadvantages of coal processing waste incineration in comparison with pulverized coal combustion. [ABSTRACT FROM AUTHOR]

Stabilization of the soil on the site is one of the methods used to improve the mechanical properties of soils. On the other hand, the replacement of cement by other materials for reducing the environmental issues has always been of interest to engineers. The soil is compacted after mixing with the stabilizing agent. The application of compaction energy can cause the grains to fail. By performing the standard compaction and subsequent soil grading tests, this study investigated the effects of different factors such as compaction moisture, cement percentage, percentage of coal waste, and grading method on the grain failure after compaction. The results of this study showed that increasing the cement weight ratio increases the maximum dry density and reduces the optimum moisture content. The increase in the weight ratio of coal waste for the sample with 3% cement increases the maximum dry density. However, for the sample with 6% cement, the addition of coal waste up to 10% increases the dry density and then reduces the density. All percentages of moisture in the compaction test result in a smaller size of sand grains due to the grain failure. On the other hand, up to the near optimum moisture, increasing the moisture will reduce the failure of grains. The grain failure rate increase is in the primary moisture contents. Also, increasing the moisture content for a mixture with 3% cement reduces the grain size, and for the mixture with 6% cement, it increases the grain size (reducing the rate of grain failure). Finally, it could be stated that the addition of coal waste has a significant effect on the change in the behavior of soil stabilized with cement in the area of grain failure. [ABSTRACT FROM AUTHOR]

The formulation of coal waste (4 million t year-1) and market waste (175.000 t year-1) is a potential development of alternative ameliorant for marginal and swamplands. The purpose of this study was to examine ameliorant formulations from coal and market waste to improve pH, available P, and CEC of Ultisols and Peat. The step I of the study used a completely randomized design with 3 replications, namely A = coal waste (100 g); B = market waste (100 g); C = 1:1 (50 g : 50 g); D = 2:1 (66.7 g 33.3 g-1) and E = 1:2 (33.3 g 66.7g-1). The step II of the study used a completely randomized design with 3 replications in 3 formulations namely: A = best formulation (100 g); B = best formulation + 10% [Ca(OH)2] (10 g 100 g-1) and C = best formulation + 10% [CaMg(CO3)2] (10 g 100 g-1). The step III of the study used a completely randomized design with 3 replications namely: A = 0 t ha-1 (0 g 500 g-1 soil); B = 10 t ha-1 (2.5 g 500 g-1 soil); C = 20 t ha-1 (5.0 g 500 g-1 soil); D = 30 t ha-1 (7.5 g 500 g-1 soil); E = 40 t ha-1 (10.0 g 500 g-1 soil) and F = 50 t ha-1 (12.5 g 500 g-1 soil). The results of the study showed that application of ameliorant formulations from coal and market waste with 10% [CaMg(CO3)2] at 50 t ha-1 increased pH, available P and CEC of Ultisols and peat, respectively by 0.60 units, 2.11 ppm P and 10.83 cmolc kg-1 on Ultisols, and 0.33 units, 2.64 ppm P and 68.86 cmolc kg-1 in peat, compared to control.

It is necessary to determine an environmentally friendly method of reusing the vast amount of coal waste that is generated during coal preparation. This study evaluates the applicability of using weathered coal waste in a permeable reactive barrier to prevent groundwater contamination. Coal waste, with different weathering degrees, was obtained from two coal mining sites in South Jeolla Province, Korea. The reactivities of the coal waste with inorganic contaminants, such as copper, cadmium, and arsenic, were examined in batch and column experiments. The batch experiment results indicate that the coal waste removal efficiencies of copper (99.8%) and cadmium (95.4%) were higher than those of arsenic (71.0%). The maximum adsorption capacities of coal waste for copper, cadmium, and arsenic calculated from the Langmuir isotherm model were 4.440 mg/g, 3.660 mg/g, and 0.718 mg/g, respectively. The equilibrium of adsorption was attained within 8 h. The column experiment results reveal that the coal waste effectively removed inorganic contaminants under flow-through conditions. Faster breakthrough times were observed in single solute system (As(V) = 19.3 PV, Cu(II) = 47.6 PV) compared with binary solute system (As(V) = 27.8 PV, Cu(II) = 65.4 PV). To confirm the applicability of using coal waste in a groundwater environment, its decontamination ability was analyzed at low concentrations and under various pH conditions. To examine the potential ecological risks in the subsurface environment, a test to determine acute toxicity to Daphnia magna and a toxic characteristic leaching procedure (TCLP) test were conducted. The coal waste was found to satisfy appropriate standards. The acute toxicity test also confirmed the ecological safety of using coal waste in a groundwater environment. The acceptably high capacity and fast kinetics of inorganic contaminant sorption by the coal waste indicate it could potentially be employed as a reactive material. The recycling and application of this abundant waste material will contribute to solving both coal waste disposal and water pollution problems. [ABSTRACT FROM AUTHOR]

Pyrite-bearing coal wastes are responsible of the formation of acid mine drainage (AMD), and their management to mitigate environmental impacts is a challenge to the coal mine industry in Europe and worldwide. The European CEReS project sought to develop a generic co-processing strategy to reuse and recycle coal wastes, based on removal of AMD generating potential through bioleaching. Chemolitoautotrophic iron- and sulfur-oxidizing microbial consortia were enriched from a Polish coal waste at 30 °C and 48 °C, but not 42 °C. Pyrite leaching yield, determined from bioleaching tests in 2-L stirred bioreactors, was best with the 48 °C endogenous consortium (80%), then the 42 °C exogenous BRGM-KCC consortium (71%), and finally the 30 °C endogenous consortium (50%). 16S rRNA gene-targeted metagenomics from five surface locations on the dump waste revealed a microbial community adapted to the site context, composed of iron- and/or sulfur-oxidizing genera thriving in low pH and metal rich environments and involved in AMD generation. All together, the results confirmed the predisposition of the pyritic coal waste to bioleaching and the potential of endogenous microorganisms for efficient bioleaching at 48 °C. The good leaching yields open the perspective to optimize further and scale-up the bioleaching process. [ABSTRACT FROM AUTHOR]

Cylinder-shaped fuel pellets that were 3 mm in diameter and 3 mm in height, with a mass of 20 mg, were produced by compressing dry coal processing waste under the pressure of 5 MPa. The first group of pellets from coal dust with a particle size less than 140 µm did not contain any additives. The pellets of the second group of fuel compositions contained an oil-impregnated porous polymer material particle with a size of 0.5 mm in the central part of the experimental sample. The particle was surrounded by coal dust from all sides. The ratio of components was 90:10% for coal dust: polymer particle. The latter value almost completely corresponds to the fraction of oil in the fuel composition, since the mass of a porous polymer material particle is negligible. The third group of compositions was a 70:30% mixture of coal dust with wood sawdust with a particle size less than 45 µm, or 45–100, 100–200 and 200–500 µm. The ignition and combustion of single fuel pellets were studied under radiant heating in an air medium while varying the temperature from 800 to 1000 °C. The processes during the fuel combustion were recorded by a high-speed video camera, and the concentrations of the main anthropogenic emissions in flue gases were measured by a gas analyzer. The main characteristics were established—ignition delay times (2–8 s) and duration of burnout (40–90 s)—at different heating temperatures. A difference was established in the combustion mechanisms of the pellets, when adding various components to the fuel mixture composition. This has a direct influence on the induction period duration and combustion time, other conditions being equal, as well as on the concentration of nitrogen and sulfur oxides in the flue gases. Adding an oil-impregnated porous polymer particle to the fuel composition intensifies ignition and combustion, since the times of ignition delay and complete burnout of fuel pellets under threshold conditions decrease by 70%, whereas adding wood sawdust reduces the content of nitrogen and sulfur oxides in the flue gases by 30% and 25%, respectively. [ABSTRACT FROM AUTHOR]

The paper presents the results of research on the influence of compaction on the shear strength of fly ash, unburnt and burnt coal wastes, and a composite (a mixture of unburnt coal waste and 30% of fly ash). The tests were carried out in a triaxial compression apparatus on samples with a diameter and height of 10 and 20 cm, respectively. In order to verify usability of the tested waste materials for earthworks, stability calculations of the road embankment made of these materials were carried out. It was shown that the tested materials were characterized by high values of shear strength parameters, which significantly depended on compaction. The most favorable values of the angle of internal friction and cohesion were obtained for the burnt coal waste, slightly lower for the composite, and the lowest for the fly ash. Stability calculations for the road embankment model showed that the slope inclination and the load on the embankment have a significant influence on the factor of safety. It was also shown that a decrease in cohesion causes significant decrease in the factor of safety. The tests and the stability calculations showed that the tested waste materials are useful for earth construction purposes. [ABSTRACT FROM AUTHOR]

The effectiveness and longevity of permeable reactive barriers (PRBs) depend on the performance of the reactive materials and the subsurface environment. The relationship of the groundwater velocity on performance of coal waste for the heavy metal removal was reported in our previous study. In this study, we investigated the performance and longevity of coal waste as a PRB material for the removal of Cd considering subsurface environmental conditions such as contamination level and groundwater velocity. The artificial groundwater contaminated by Cd were prepared with various concentrations ranging from 10 to 100 mg L−1. Lab-scale column experiments were conducted using coal waste filled columns by injecting the artificial groundwater. The breakthrough curves were analyzed advection dispersion equation coupled with equilibrium sorption model to determine the retardation factor. The Cd breakthrough curves exhibited different retardation with respect to the contamination levels. The Cd transport was more retarded as the contamination level lowered. The relationship between the retardation factor and the contamination levels could be explained with empirical equations based on non-linear sorption isotherms. By adopting the velocity dependency of sorbent performance in our previous study, transport of Cd within coal waste was simulated under various subsurface environmental conditions to construct the longevity function. The function could be used for the longevity prediction of coal waste as a PRB material considering groundwater velocity and contamination level in subsurface environment. [Display omitted] • Performance of coal waste for removal of Cd is dependent to subsurface environment. • High contamination level reduce the longevity of coal waste as a reactive material. • High pore-water velocities induced non-equilibrium sorption of Cd on coal waste. • Empirical functions of sorption parameters on contaminated groundwater environment. • Expectation of longevity as a reactive material in permeable reactive barrier. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) are of great importance to modern society and their reliable supply is a major concern of many industries that utilize them in metal alloys, semiconductors, electrical equipment, and defense equipment. REEs in the coal waste have been revealed to be an alternative resource for REEs production. In this study, the extraction, recovery, and upgrading of the REEs from coal waste has been realized with the bioleaching and precipitation processes. Reliable and sustainable acid and oxidant production from the oxidation of the pyrite with Acidithiobacillus ferrooxidans to generate acid for leaching were realized in this research. The acidified bioleaching solution was used to extract REEs from coal waste, with 13–14% yields for most REE elements (~72 h of leaching). However, recovery for longer duration tests was significant higher (varies from 40–60% for individual REEs). After extraction, precipitation and separation processes were designed with the aid of Visual Minteq calculations and modeling to concentrate the REEs. With the procedures designed in this research, a final REEs precipitate product containing 36.7% REEs was produced.

The paper presents the results of research on rare earth elements (REY) and selected radionuclides in barren rocks deposited on a heap at a mine belonging to the Polish Mining Group (the largest producer of hard coal in EU countries). The maximum concentration of REEs determined in silstones was 261.6 mg/kg and in sandstones 221.2 mg/kg. The average uranium and thorium content in silstones was 6.8 mg/kg and 11.6 mg/kg, respectively. On the other hand, the samples of burnt coal shales contain on average 3.5 mg/kg of uranium and 9.7 mg/kg of thorium. In all coal waste samples, the REE values are higher than in hard coal (15.7 mg/kg). Carriers of REY, uranium, and thorium in coal waste are detritic minerals: monazite and xenotime, which are part of the grain skeleton of barren rocks. Coal waste samples are characterized by a variable distribution of REY concentrations as well as a variable content of radionuclides. The 226Ra, 228Ra, and 40K measurements in the investigated samples were performed using the gamma spectrometry technique. The concentrations of the analyzed isotopes differed depending on the mineralogical composition of the investigated samples. The present study results may be important in determining the possibility of utilization of wastes of barren rocks stored in the mine heap and in assessing environmental and radiological hazards.

The β- and 15R-sialons were obtained from coal waste (carbonaceous rocks) at the Institute of Fossil Fuels (IGI) for the first time in the world. Ceramics based on β-sialon powder made from carbonaceous rock by compression sintering possessed increased cracking resistance, as compared to that of known analogues, even when heated in a plasma flow at 2000°C. In this case, other characteristics of the ceramics, such as strength and thermal coefficient of linear expansion, are also in the acceptable ranges of characteristics for such materials. The full-scale tests of odd-shaped products at temperatures to 1420–1450°C did not cause destruction and cracking; this fact demonstrates the applicability of carbonaceous rocks of a certain composition as raw materials for the production of heat-resistant refractory nitride ceramics based on β-sialon. Technical requirements imposed on the composition of carbonaceous rocks suitable for the production of β-sialon found in the course of this study and technical characteristics of β- and 15R-sialon ceramics obtained from carbonaceous rocks are reported. [ABSTRACT FROM AUTHOR]

Technologies for the conversion of coal mining and processing wastes into commercial products depending on the characteristics of raw materials are considered. It is shown that the production of construction materials from coal wastes can be most popular. The production of rare earth element (REE), aluminum, and iron concentrates; coagulants for water purification; fuel additives (energy generation coals); and additives for the metallurgical industry from coal wastes was studied. The concept of a technological complex, which makes it possible to obtain a wide range of marketable products from coal wastes in a single cycle, is proposed for the first time. The basic configuration of integrated technology was developed, and the basic equipment for technological processes was selected. The possible results of the implementation of this technology in industry are shown. [ABSTRACT FROM AUTHOR]

The main coal seams explored in the coal region of Santa Catarina are Barro Branco (BB) and Bonito (BO). Owing to the association with the mineral matter, the tailings generated in the beneficiation are arranged in disposal areas, and subject to the generation of acid mine drainage (AMD). The objective of this study was to evaluate the use of pyrite present in the coal rejects of the BB and BO seams and the environmental gains with desulfurization. For this purpose, densimetric separability test, ash, sulfur, and AMD generation analyses were performed. In addition, the amount of pyritic concentrates and sulfuric acid were estimated considering the current level of production. Three densimetric fractions were obtained: less than 2.2 (energetic material), between 2.2 and 2.7 (low sulfur material), and greater than 2.7 g cm-3 (pyrite concentrate). The results revealed that the two seams could be beneficiated by gravimetric processes, obtaining pyrite concentrates with approximately 60% pyrite. By converting pyrite to sulfuric acid would represent an increase of 500,000 tons per year in the Brazilian production of this material and, in environmental terms, a reduction of up to 90% of the acidity potential to be disposed in the environment in the case of the BB seam and 65% for the BO seam. It was also observed that the "desulfurized" fraction of the BO had higher levels of pyrite and a higher potential for acidity generation than the BB seam, implying greater risks of environmental contamination and higher acid water treatment costs. [ABSTRACT FROM AUTHOR]

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More than 200 dumps serving the disposal of waste produced by hard coal mines are situated in the Upper Silesian region. The material found in the dumps is mainly coal mining waste (i.e., overburden rocks obtained in the production and processing of hard coal). Volumetric and bulk densities are important physical parameters when it comes to recording the amount of waste disposed at the dumps. A possibility of determining this parameter during field studies was analysed. The method applied consisted of excavations performed in dump areas, weighing the excavated material and a precise determination of the volume of a selected space. A study carried out in this way allowed for testing a much larger sample, as the mass of the sample was only limited by the carrying capacity of the vehicle transporting the material to be weighed using industrial-grade scales. This had a positive impact on the accuracy of determining density. The precise determination of density was achieved by using the photogrammetric method, which guaranteed high accuracy. Two alternative photogrammetric techniques were used to ensure the control of calculations, i.e., close range terrestrial photogrammetry and low-altitude photogrammetry using unmanned aerial vehicles. Photographic equipment with high-resolution matrices was used. The processing of photographic documentation was conducted using professional software: Pix4d Mapper and AutoCad Civil 3D. Based on the mass and volume results obtained using the method described above, the bulk density of three coal mining waste samples was obtained for the actual conditions of the dump. The in-situ testing allowed us to consider the actual density of the waste material found in the dump. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the use of ceramic and coal waste powders as partial replacement of cement in roller compacted concrete pavement mixture was investigated. The mixtures were produced with the ceramic waste powder contents at 5% and 10% of total cementitious material (by weight). In addition, mixtures containing ceramic and coal waste powders were prepared simultaneously. Five different concrete mixes were prepared, and the unit weight, VeBe time, compressive, splitting tensile, and flexural strengths of mixture were measured for all the specimens. All tests were performed after 7, 28, and 90 days of curing. The results indicated that the use of the ceramic and coal waste powders as a partial replacement of cement decreased the unit weight and VeBe time. According to the results, the application of ceramic and coal waste powders reduced the splitting tensile, compressive and flexural strengths than control specimens. The lowest loss in strengths was found in specimens containing 5% ceramic waste powder, that after 28-day curing, it was observed that the average compressive, splitting tensile and flexural strengths decreased by 4%, 5%, and 2%, respectively. In addition, the 28-day compressive strength of the mixture containing 5% ceramic waste powder was higher than the minimum value proposed by the guide. Furthermore, the loss of strength in specimens containing only ceramic waste powder was lower than the specimens containing ceramic and coal waste powders. It could be concluded that using ceramic and coal waste powders in roller compacted concrete pavement not only is it effective in reducing the cost and preventing waste from entering the environment but also it can be considered as a step toward sustainability.Graphical abstract: [ABSTRACT FROM AUTHOR]

Activated carbon as an adsorbent has been widely used to remove toxicity from wastewater, but its high cost causes restrictions in its use. For this reason, this study investigated at lab-scale the raw coal waste, namely fly ash and bottom ash, by being a potential source of pollution to be recycled and used as adsorbents. Besides coal waste, the adsorptiontes reclaim natural adsorbents materials, particularly clay soil and sea sand. The adsorbents were compound in different layers to form a filter Matrix in order to perceive the performance of those adsorbents toward heavy metals removal. The result shows that an efficient simultaneous decrease of heavy metals has taken place due to the proprieties of the filter matrix that interact with wastewater molecules and consequently enhance its quality, the highest removal efficiency of heavy metals achieved 83% for cadmium in the matrix compound of Fly ash, bottom ash and clay. The novelty of this research lies in applying raw materials with no recourse to chemical or biological treatment to the adsorbent materials. The main objective is to reclaim a low cost efficient adsorption process based on raw materials to be applied in a wastewater pretreatment plant where wastewater samples were picked out. [ABSTRACT FROM AUTHOR]

Abstract A sample coal waste activated by rhamnolipid biosurfactants was used as an efficient adsorbent for the adsorption of cadmium from aqueous solution. The effects of three factors, namely, initial solution pH (3–11), absorbent to cadmium ratio (12.5–162.5) and contact time (3–31 h), on cadmium removal were studied and optimized using a central composite type response surface methodology. The two factors that play a key role in the adsorption process are pH and absorbent dosage. Optimum adsorption conditions achieved at pH 9, absorbent to cadmium ratio of 125 and equilibrium contact time of 10 h, resulted in more than 99% cadmium removal. Kinetic studies revealed that a maximum removal can be achieved before 10 min of adsorption process following a pseudo-second order model. The selectivity study in bimetal aqueous systems using copper, lead and zinc metals showed the adsorption order of Cu2+ > Cd2+ > Zn2+ > Pb2+. The cadmium adsorption on activated coal waste was also found to follows the Temkin isotherm model with a correlation coefficient of 92.43%. Graphical abstract Image 1 Highlights • Cadmium removal from aqueous solution by rhamnolipid-activated coal waste was investigated. • Adsorption conditions for maximum Cd removal have been studied. • Cd was successfully removed (>99%) with activated coal waste. • Cd adsorption followed the pseudo-second order kinetics and Temkin isotherm model. [ABSTRACT FROM AUTHOR]

• Coal waste used as aggregate replacement in concrete. • Thorough assessment of sulfuric acid resistance. • Higher CW contents lead to more water absorption. • Strength enhanced by 5% and 10% CW, but decreased with higher CW contents. • Formation of harmful Ca(OH)2 crystals, ettringite needles, and gypsum observed in SEM images. The vulnerability of concrete to sulfuric acid attack requires much attention in both design and maintenance. Taking the waste management approach into account, this study utilized coal waste (CW) as a partial replacement for fine and coarse aggregates. The use of CW as aggregate replacement materials in concrete is a novel topic. Regarding the literature, concrete mixtures with CW aggregates showed relatively similar strength properties to conventional concrete. However, the effects of aggressive environments on the concrete containing CW aggregate have not been addressed. Here, the effects of sulfuric acid attack on the key properties, such as split tensile strength (STS), compressive strength (CS), weight loss, and ultrasonic wave velocity (UWV), were thoroughly assessed. Moreover, scanning electron microscope (SEM) images have been captured to discern the morphology changes. Various CW dosages (0%, 5%, 10%, 15%, and 20% by weight of dry aggregates) were used. The results revealed that higher CW contents led to more water absorption and stiffer mixtures with lower workability. The weight loss of the samples showed an increasing trend with increasing CW contents. The split tensile strength and compressive strength of samples without sulfuric acid attack were enhanced by using 5% and 10% CW. After exposure to the sulfuric acid solution, the strength of CW-concrete samples was continuously decreased by increasing CW contents. The UWV values were decreased by increasing CW contents, which induce more porosity and lower integrity in concrete elements. SEM images show that the use of CW led to the formation of Ca (OH) 2 crystals that were not wet, needles of ettringite, and gypsum, which severely hurt the properties of permeability, durability, and strength. [ABSTRACT FROM AUTHOR]