A review on fly ash from coal-fired power plants: chemical composition, regulations, and health evidence

Harnessing Ash for Sustainable CO2 Absorption: Current Strategies and Future Prospects

This review explores the potential of using different types of ash, namely fly ash, biomass ash, and coal ash etc., as mediums for CO2 capture and sequestration. The diverse origins of these ash types - municipal waste, organic biomass, and coal combustion - impart unique physicochemical properties that influence their suitability and efficiency in CO2 absorption. This review first discusses the environmental and economic implications of using ash wastes, emphasizing the reduction in landfill usage and the transformation of waste into value-added products. Then the chemical/physical treatments of ash wastes and their inherent capabilities in binding or reacting with CO2 are introduced, along with current methodologies utilize these ashes for CO2 sequestration, including mineral carbonation and direct air capture techniques. The application of using ash wastes for CO2 capture are highlighted, followed by the discussion regarding challenges associated with ash-based CO2 absorption approach. Finally, the article projects into the future, proposing innovative approaches and technological advancements needed to enhance the efficacy of ash in combating the increasing CO2 levels. By providing a comprehensive analysis of current strategies and envisioning future prospects, this review aims to contribute to the field of sustainable CO2 absorption and environmental management.

The association of manganese overexposure and neurobehavioral function is moderated by arsenic: A metal mixture analysis of children living near coal ash storage sites

Manganese is an essential element but can be neurotoxic if overexposed. Our previous study found that a higher level of manganese in nail biomarkers from children living near coal ash storage sites was associated with poorer neurobehavioral function. Children living near this type of pollution may be exposed to other metal neurotoxicants and a better understanding of manganese in the context of multiple exposures is needed. Mixture analyses were completed using nail samples from 251 children aged 6-14 years old. These biomarkers containing metals known to impact brain functioning were investigated to test our hypothesis that a mixture of metals including manganese impacts the development of children living near coal ash sites. Nails collected from children were analyzed using ICP-MS for manganese, arsenic, cadmium, lead, and zinc based on previous research on neurotoxicity. Bayesian kernel machine regression (BKMR) was used while adjusting for age, sex, and maternal education as potential covariates. Children also completed the Behavioral Assessment Research System (BARS) to provide neurobehavioral measures of attention and processing speed as outcomes for mixture analyses. Metal mixture analyses indicated that the relationship of manganese concentration and attention and processing speed was moderated by arsenic.,. When nail biomarkers for arsenic were highest (90th percentile), manganese was associated with poorer neurobehavioral performance on the BARS, measured by CPT hit latency. At low levels of arsenic (10th percentile), there was no evidence of harmful effects from overexposure to manganese on CPT hit latency based on BKMR analysis. Previously reported effects of manganese on neurobehavioral function may be moderated by arsenic exposure. Metal exposures and behavior outcomes can be studied with mixture analyses such as BKMR to evaluate effects of simultaneous exposures on children exposed to pollution.

Exploiting fly ash as an ecofriendly pesticide/nematicide on Abesmoschus esculuntus: Insights into soil amendment-induced antioxidant fight against nematode mediated ROS

Conventional pest control measures, such as chemical pesticides and nematicides, have limited efficacy and raise environmental concerns, necessitating sustainable and eco-friendly alternatives for pest management. Therefore, to find a complementary eco-friendly pesticide/nematicide, this study investigated the role of fly ash (FA) in managing a notorious pest, Meloidogyne javanica and its impact on the growth and physiology of Abelmoschus esculentus. Molecular characterization using SSU and LSU rDNA gene markers confirmed the identity of Indian M. javanica as belonging to the same species. Biotic stress induced by nematode infection was significantly alleviated (P < 0.05) by FA application at a 20% w/v, regulating of ROS accumulation (44.1% reduction in superoxide anions and 39.7% reduction in hydrogen peroxide content) in the host plant. Moreover, FA enhanced antioxidant defence enzymes like superoxide dismutase (46.6%) and catalase (112%) to combat nematode induced ROS. Furthermore, the application of FA at a 20% concentration significantly improved the biomass and biochemical attributes of okra. Fly ash also upregulated the activity of the important osmo-protectant proline (11.5 μmol/g FW) to mitigate nematode stress in host cells. Suppression of disease indices like gall index and reproduction factor, combined with in-vitro experiments, revealed that FA exhibits strong nematode mortality capacity and thus can be used as a sustainable and eco-friendly control agent against root-knot nematodes.

Phytostabilization of fly ash from a coalmine in Botswana and biovalorisation of the recovered Napier grass (Pennisetum purpureum Schumach.)

The disposal of fly ash (FA) from coal power plants polluting the air, soil, and groundwater is a major environmental concern. Phytoremediation to rehabilitate fly ash dumpsites is a promising alternative but has practical concerns about the disposal of harvested biomass. This study investigated the effect of supplementing fly ash with fresh sewage sludge (FSS), aged sewage sludge, food waste, and compost (COM) to enhance the phytoremediation potential of Napier grass and its subsequent utilization for ethanol production. The highest removal of Mn (1196.12 g ha-1) and Ni (128.06 g ha-1) from FA could be obtained when Napier is grown in the presence of FSS and inorganic fertilizer (NPK). In addition, the highest bioethanol yield (19.31 g L-1) was obtained from Napier grown in fly ash with COM + NPK, thus providing additional economic benefits aside from the remediation process. Given the significant levels of heavy metals present in the pulp and bio-slurry after ethanol production, further research is required in this area to determine the best ways to utilize this waste such as converting it into biochar.

Use of Alkaline-Activated Energy Waste Raw Materials in Geopolymer Concrete

Silica fly ash, Certyd aggregate, and an alkaline solution were used to produce lightweight geopolymer concretes. The compressive strength, water absorption, and bulk density results, along with SEM photos showing the structure of the obtained composite, were obtained. Tests conducted on the specifications of lightweight geopolymer concretes have revealed significant chemical interactions between the ash aggregate and the geopolymer mortar, particularly when the coarse aggregate surface has been pre-treated with an alkaline solution. A statistical analysis of the experimental data, which investigated the influence of three key variables on the compressive strength, water absorption, and bulk density of lightweight geopolymer concrete (LBG), identified the following factors as having the most substantial impact: the quantity of alkali used, the curing temperature, and the concentration of alkali in the mixture. The optimal test series exhibited a commendable compressive strength of 20.14 megapascals (MPa), accompanied by a water absorption rate of 14.72%, and a bulk density of 1486.6 kg per cubic meter (kg/m³). These findings underscore the importance of alkali content, curing temperature, and alkali concentration in tailoring the properties of lightweight geopolymer concrete to meet specific performance requirements.

WITHDRAWN: Trace metals translocation from soil to plants: Health risk assessment via consumption of vegetables in the urban sprawl of a developing country

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Ecological and Health Risks Attributed to Rare Earth Elements in Coal Fly Ash

The occurrence and distribution of yttrium and rare earth elements (REYs), along with major elements and heavy metal(loid)s (HMs) in coal fly ash (CFA) from five coal-fired power plants (CFPPs), were analyzed, and the REY-associated ecological and health risks were assessed. The individual REYs in CFA were abundant in the following order: Ce > La > Nd > Y > Pr > Gd > Sm > Dy > Er > Yb > Eu > Ho > Tb > Tm > Lu. The total REY content ranged from 135 to 362 mg/kg, averaging 302 mg/kg. The mean light-to-heavy REY ratio was 4.1, indicating prevalent light REY enrichment in CFA. Significantly positive correlations between the REYs suggested that they coexist and share similar origins in CFA. REYs were estimated to pose low to moderate ecological risks, with risk index (RI) values ranging from 66 to 245. The hazard index (HI) and target cancer risk (TCR) of REYs from CFA, estimated to be higher for children (HIc = 0.15, TCRc = 8.4 × 10-16) than for adults (HIa = 0.017, TCRa = 3.6 × 10-16), were well below the safety limits (HI = 1, TCR = 1.0 × 10-6). However, the danger to human health posed by HMs in the same CFA samples (HIc = 5.74, TCRc = 2.6 × 10-4, TCRa = 1.1 × 10-4) exceeded the safe thresholds (excl. HIa = 0.63). The mean RI and HI attributed to REYs in CFA were 14% and 2.6%, respectively, of the total risks that include HMs.

Spatial Variability of Rare Earth Elements in Groundwater in the Vicinity of a Coal-Fired Power Plant and Associated Health Risk

This study investigated the occurrence and distribution of rare earth elements (REEs), including 14 lanthanoids, scandium (Sc), and yttrium (Y), in groundwater around a large coal-fired thermal power plant (TPP). The ICP-MS technique was used to analyze 16 REEs in groundwater samples collected from monitoring wells. REE concentrations ranged from 59.9 to 758 ng/L, with an average of 290 ng/L. The most abundant was Sc, followed by La, accounting for 54.2% and 21.4% of the total REE concentration, respectively. Geospatial analysis revealed the REE enrichment at several hotspots near the TPP. The highest REE concentrations were observed near the TPP and ash landfill, decreasing with the distance from the plant and the landfill. REE fractionation ratios and anomalies suggested the Light REE dominance, comprising over 78% of the total REEs. Correlation and principal component analyses indicated similar behavior and sources for most REEs. Health risk assessment found hazard indices (HI) of 1.36 × 10-3 and 1.98 × 10-3 for adults and children, respectively, which are far below the permissible limit (HI = 1). Likewise, incremental lifetime cancer risks (ILCR) were all below 1 × 10-6. Nevertheless, ongoing ash disposal and potential accumulation in the environment could elevate the REE exposure over time.

Shifting terrains: Understanding residential contaminants after flood disasters

Flood disasters can induce the mass transport of soils and sediments. This has the potential to distribute contaminants and present novel combinations to new locations - including residential neighborhoods. Even when soil contaminants cannot be directly attributed to the disaster, data on bacterial and heavy metal(loids) can facilitate an environmentally just recovery by enabling reconstruction decisions that fill data gaps to minimize future exposure. These data-gathering interventions may be especially useful in poor, rural, and racially diverse communities where there is a high probability of exposure to multiple hazards and a potential dependency on the financial resources of disaster aid as a means of reducing chronic exposures to other environmental pollutants. At the same time, entering these post-disasters spaces is ethically complex. To acknowledge this complexity, we pilot a framework for work that gathers social-ecological hazard information while retaining a fair-minded approach to transdisciplinary work. Assembled a transdisciplinary team to recruit participants from 90 households subjected to flooding in the southeastern US. Participating households agreed to interviews to elicit flood experience and environmental health concerns, soil sampling for fecal bacteria (E. coli) and soil sampling for selected heavy metals and metalloids (Pb, As, Cd) at their flooded residence. Soil sampling found a wide range of E. coli concentrations in soil (0.4-1115.7 CFU/ dry gram). Heavy metal(loid)s were detected at most residences (As 97.9 %; Ca 25.5 %; Pb 100 %). Individually, heavy metal(loid) concentrations did not exceed regulatory thresholds. Hazard, risk, and mitigation concerns expressed during interviews reveal that integrated human-nature concepts complicate common understandings of how hazard perceptibility (smell, sight, touch, and information) affects research-action spaces. Qualitative analysis of interviews and field notes revealed that soil-related hazards addressed by our biophysical protocols were less salient than changes with direct causal associations with flooding. We conclude by discussing the potential for the social-ecological hazard information that is fair-minded and transdisciplinary (SHIFT) framework to advance environmentally just approaches to research-action spaces after disasters.

Coal waste-derived synthesis of yellow oxidized graphene quantum dots with highly specific superoxide dismutase activity: characterization, kinetics, and biological studies

The disintegration of coal-based precursors for the scalable production of nanozymes relies on the fate of solvothermal pyrolysis. Herein, we report a novel economic and scalable strategy to fabricate yellow luminescent graphene quantum dots (YGQDs) by remediating unburnt coal waste (CW). The YGQDs (size: 7-8 nm; M.W: 3157.9 Da) were produced using in situ "anion-radical" assisted bond cleavage in water (within 8 h; at 121 °C) with yields of ∼87%. The presence of exposed surface and edge groups, such as COOH, C-O-C, and O-H, as structural defects accounted for its high fluorescence with εmax ∼530 nm at pH 7. Besides, these defects also acted as radical stabilizers, demonstrating prominent anti-oxidative activity of ∼4.5-fold higher than standard ascorbic acid (AA). In addition, the YGQDs showed high biocompatibility towards mammalian cells, with 500 μM of treatment dose showing <15% cell death. The YGQDs demonstrated specific superoxide dismutase (SOD) activity wherein 15 μM YGQDs equalled the activity of 1-unit biological SOD (bSOD), measured using the pyrogallol assay. The Km for YGQDs was ∼10-fold higher than that for bSOD. However, the YGQDs retained their SOD activity in harsh conditions like high temperatures or denaturing reactions, where the activity of bSOD is completely lost. The binding affinity of YGQDs for superoxide ions, measured from isothermal calorimetry (ITC) studies, was only 10-fold lower than that of bSOD (Kd of 586 nM vs. 57.3 nM). Further, the pre-treatment of YGQDs (∼10-25 μM) increased the cell survivability to >75-90% in three cell lines during ROS-mediated cell death, with the highest survivability being shown for C6-cells. Next, the ROS-induced apoptosis in C6-cells (model for neurodegenerative diseases study), wherein YGQDs uptake was confirmed by confocal microscopy, showed ∼5-fold apoptosis alleviation with only 5 μM pretreatment. The YGQDs also restored the expression of pro-inflammatory Th1 cytokines (TNF-α, IFN-γ, IL-6) and anti-inflammatory Th2 cytokines (IL-10) to their basal levels, with a net >3-fold change observed. This further explains the molecular mechanism for the antioxidant property of YGQDs. The high specific SOD activity associated with YGQDs may provide the cheapest alternative source for producing large-scale SOD-based nanozymes that can treat various oxidative stress-linked disorders/diseases.

Hydrothermal dewatering of low-grade coal: Product evaluation and primary component analysis of ash deposition

The hydrothermal dewatering (HTD) process was carried out using 16 coal samples obtained from several regions in Indonesia. This research aims to identify the dominant parameters that influence ash deposition during coal combustion in a boiler or gasifier due to the HTD process. This research was conducted due to the lack of clear and comprehensive information regarding this issue. Therefore, to understand the effect of HTD on ash deposition, an analysis of the chemical composition of ash and the ash melting temperature (AFT) was carried out. To verify the data obtained from the experimental analysis, statistical methods such as paired sample t-test and primary component analysis were applied to obtain the dominant parameters influencing ash deposition due to HTD. Eight parameters, namely SiO2, Fe2O3, slagging viscosity index (SR), Babcock index (Rs), initial deformation temperature, softening temperature, hemispherical temperature, and fluid temperature under oxidative conditions, have the greatest influence on ash deposition due to the HTD process. Based on the average values of SR and Rs, raw coal and processed coal samples have the same ash deposition trend. On the other hand, based on AFT under oxidation conditions, processed coal has a higher AFT, indicating that the tendency for ash deposition is lower than raw coal. Therefore, the HTD process can be used to improve the quality of low-grade coal. As an implication, low-grade coal, which has not been widely utilized in Indonesia, due to several constraints regarding its characteristics, through the HTD process can be optimized where coal utilization is a bridge towards the use of green energy which is being intensively pursued.

Assessment of heavy metal contamination in street dust: concentrations, bioaccessibility, and human health risks in coal mine and thermal power plant complex

Coal mining has also been associated with adverse environmental and health impacts including cancer and respiratory disorders, with the presence of thermal power plants exacerbating the problem of heavy metal pollution. Minimal studies have been conducted on the environmental impacts, health risks, and bioaccessibility of heavy metals in coal mine areas. Consequently, samples of street dust were collected from different locations in the Singrauli mine complex and analysed. Heavy metals (Cu, Ni, Zn, Cr, Co, As, and Mo) were found to be higher than the background concentration, with the maximum concentration was found in areas close to the Thermal Power Plants, like Near Vindyachal TPP, Near Shakti Nagar TPP, and Anpara. The highest geo-accumulation index value was found for Co, Mo, Zn, and As, indicating moderate to strong pollution levels. Health risk assessment (for both adults and children) revealed that Cr and Fe posed significantly higher Hazard Quotient and Hazard Index (HI) values, indicating significant non-carcinogenic threats. Moreover, Carcinogenic Risk (CR) values for Cd, Cr, and Ni indicated a risk of carcinogenicity to the public exposed to road dust. The study also examined the bioaccessibility of the metals, which showed that the gastric phase accumulated a higher percentage of Ni (42.52%), Pb (34.79%), Co (22.22%), As (20%) and Cu (15%) than the intestinal phase. Strong positive correlation was observed between metal concentration (Cu, Pb, Cr, Fe, Zn, and Mn), HI, and CR of adult and child, while bioaccessibility of intestinal phase was positively correlated with gastric phase of metals (Cu, Ni, Co, As, and Mn).

Differences in the dynamic evolution of surface crack widths at different locations in the trench slope area and the mechanisms: a case study

Coal seams were buried extremely shallowly in the trench slope area, which is prone to inducing surface cracks, seriously threatening the surface environment and mine safety production. The development of surface mining cracks varies at different locations in the trench slope area. In this research, we aimed to study the dynamic characteristics and laws of surface crack widths at different mining locations in the trench slope area and reveal the evolution mechanism of surface crack widths. Taking the 125,203 working face in Anshan Coal Mine in Shaanxi Province, China, as the geological prototype, we analyzed the full-cycle dynamic change law and planar distribution law of the surface crack widths in the trench slope area by combining the unmanned aerial vehicle remote sensing technology and field actual measurements and revealed the dynamic evolution mechanism of surface mining cracks in the trench area. The research results showed that the dynamic changes of surface crack widths varied at different locations of the slope. The surface crack width in the downslope area increased first and then stabilized with the advance of the working surface; the crack width at the bottom of the trench shows the dynamic change characteristic of increasing-decreasing-slightly increasing-stabilizing with the continuous advance of the working surface. The surface crack width in the upslope area showed the dynamic change of increasing-decreasing-stabilizing with the continuous advance of the working surface. Influenced by the surface morphology, the development mechanisms of surface mining cracks were different. The research results can provide practical guidance for selecting the best treatment time for surface cracks in different areas.

Incorporation of Fly Ash in Flame-Retardant Systems of Biopolyesters

The incorporation of fly ash in polybutyl succinate (PBS) and polybutyl adipate terephtalate (PBAT) in the partial replacement of ammonium polyphosphate and/or melamine polyphosphate is evaluated in the present work. Furthermore, the influence of the surface modification of fly ash with two silanes and titanate coupling agents was also studied. Cone calorimeter experiments, pyrolysis combustion flow calorimeters (PCFCs), and UL94V tests were used to assess the fire performance of the composites. Scanning electronic microscopy, X-microanalysis, and X-ray diffractometry analysis were carried out on cone calorimeter residues in order to access the fire-retardant mode of action. The formation of new components due to the presence of fly ash was highlighted by X-ray diffractometry, indicating the synergistic effects between the flame-retardant system and fly ash. The X-microanalysis results showed that the main fraction of initial phosphorous is present in the cone calorimeter residue, indicating that the proposed system acts in a condensed phase.

Indoor coal ash and school and social competency among children aged 6-14 years

BACKGROUND

A child's ability to succeed in social interactions and in a school setting are important for their development and growth. Exposure to environmental pollutants has been associated with poorer school performance and fewer social interaction in children. Fly ash, a waste product generated when burning coal for energy, is comprised of small glass spheres with neurotoxic heavy metal(loid)s found to be risk factors for learning and social problems in school.

OBJECTIVE

The purpose of this novel study was to assess the association of fly ash in children's homes with school and social competency.

METHODS

We recruited children aged 6-14 years old from communities located within 10 miles of two coal-burning power plants. In homes of the participants, fly ash was collected on polycarbonate filters using personal modular impactors. We measured school competency and social competency using the validated Child Behavioral Checklist. Using Tobit and linear regression we investigated the relationship of indoor fly ash with school and social competency.

RESULTS

Forty-three percent of children in the study had fly ash in their homes. In covariate-adjusted Tobit models, children with fly ash in their homes scored on average 2.63 (95% CI: -4.98, -0.28) points lower on the school competency scale than peers without ash in their homes. We did not observe that fly ash in homes was related with lower social competency.

SIGNIFICANCE

Results from this study suggest that children with fly ash in their homes had poorer performance in the school setting, compared to peers without fly ash in their homes. In the US, coal-fired power plants are being closed, however health concerns about pollution from coal ash storage facilities remains. Findings from this study can provide impetus for creating of public health policy and to highlight the need future research on children's exposure to fly ash.

IMPACT

Children's growth and development are impacted by their social interactions and ability to perform in school settings. Environmental pollutants may impact these essential elements of development. Millions of children are exposed to fly ash which is a waste product generated from burning coal. Fly ash, an environmental health threat throughout the world, is comprised of small glass spheres with trace concentrations of neurotoxic metal(loid)s. Findings from this research show that children with fly ash in their homes are significantly more likely to have poorer school performance than children without fly ash in their homes.

A critical review on mechanochemical processing of fly ash and fly ash-derived materials

Fly ash (FA) is a solid, fine powder that constitutes a by-product obtained when coal, biomass, municipal solid waste or a mixture of these are combusted. This review article focuses on the mechanochemistry of coal fly ash (CFA), as well as highlights the issue of fly ash from municipal solid waste (MSW). In general, FA is regarded as a waste of public concern (since it contains hazardous components), which is primarily consumed in the construction industry, as well as in chemical synthesis and environmental engineering. However, the actual amount of FA recycled is still less than the amount produced, with the reuse rate of only up to 30 %. Due to its relatively low reactivity and heterogeneity, FA is commonly landfilled in huge quantities. Nevertheless, the physical and chemical properties of FA can be tailored, for example, by mechanical forces, ultimately leading to a higher value-added product. Currently, mechanochemistry (MC) is drawing attention in chemical synthesis, pollution remediation and waste management, especially as a possible solution for various drawbacks of conventional syntheses and processes. Mechanochemical processing of FA can be considered eco-friendly, inexpensive and efficient, in particular for processing tons of readily available fly ash already stored in ponds or landfills. With the aim of highlighting the hidden potential and facilitating the favorable use of FA, this article deals with FA as an environmentally challenging material, FA reactivity and recycling through mechanochemical processing, mechanochemical stabilization of heavy metals in FA, as well as up-to-date challenges for life cycle assessment (LCA) in evaluating FA-derived materials. Furthermore, all these full-potential aspects of FA mechanochemistry have not been addressed before, which is a valuable contribution to the existing literature.

An extensive individual particle analysis of solid airborne particles collected in a moderately urbanized area

Detailed individual particle characterization of PM₁₀, in terms of particle size, morphology, and elemental composition, was done using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. The samples were collected in four localities in the Czech Republic (Central Europe), three of which are medium-sized cities, and one is a natural locality in the mountains. More than 1600 particles obtained from each locality were evaluated. During the sampling period (1.9.-8.9.2019), the atmospheric conditions were similar in the localities, which enabled the identification of PM₁₀ characteristics common to all the sampling sites. Some differences in the particles' morphology and composition, arising from site-specific conditions, were observed too. The most abundant elements in the PM₁₀ were C, O, Si, Fe, Al, Ca, Na, K, Mg, and S, but some toxic elements (Cr, Cu, and Ni) were also detected. The main component of the PM₁₀ is carbon, whose multimodal distribution indicates that the particles contain different carbonaceous chemical compounds. The distribution of carbon in the natural locality was different compared to the other sites, suggesting a specific character of the sources of carbonaceous compounds in this region. Last but not least, a relationship between Al, Si, and O concentrations was found, which implies the presence of aluminosilicates and silicon dioxide (possibly sand) of crustal origin in the particles.

Influence of Various Coal Energy Wastes and Foaming Agents on Foamed Geopolymer Materials' Synthesis

The regularities of obtaining foamed alkali-activated geopolymer materials based on different wastes of coal power engineering (fly ash, fuel (boiler) slag, ash, and slag mixture) were considered. The phase composition of the studied waste showed the presence of a significant amount of the amorphous phase, as well as a crystalline phase. mostly in the form of high quartz. The microstructure of studied the waste showed that the fly ash consisted of monodisperse hollow aluminosilicate microspheres, the fuel slag was represented by polydisperse irregular particles, and the ash and slag mixture included both of these materials in different ratios. Blowing agents such as aluminum powder, hydrogen peroxide, and sodium hypochlorite were chosen to achieve the porous structure of the geopolymer materials. The calculations of the geopolymer precursor compositions were carried out. Samples were synthesized, and their physical and mechanical properties, such as density, strength, porosity, and thermal conductivity, were analyzed. The micro- and macrostructure of the samples, as well as the pore distribution of the obtained geopolymers were studied. Conclusions were made on the choice of the most-optimal foaming agent and the optimal coal combustion waste suitable for the synthesis of the geopolymer materials.

Geochemical, mineralogical and toxicological characteristics of coal fly ash and its environmental impacts

Coal and coal-based products (by-products), along with other fossil fuels should be used with caution because of their impact on human health and the global climate. In the light of the environmental impact these fossil fuels cause, it's essential to understand the elemental configuration of coal-derived samples and their impact on the ecosystem. Some reports in past have described, geochemical and mineralogical physiognomies of fly-ash and their impact on the environment. However, a comprehensive investigation of various aspects of fly ash like geochemistry, mineralogy, morphology, and toxicological effects has been very sparse and the present study reports the above aspects. The ICP-OES studies confirm the presence of various elements (Al, Ca, Fe, Mg, Na, P, S, Si, and Ti) in the samples. The XRD analysis exposed the presence of minerals like Quartz, H-Hematite, Anatase, Muscovite, and Rutile, in addition to the various phases such as amorphous and crystalline in the fly-ash. Specific samples also possessed Ilmenite which is uncommon in many other samples. Chromium and lead, the well-known heavy metals to cause soil and water pollution in the neighbourhood were found to be existing in higher concentrations in the fly-ash samples, whereas cadmium was found to be the least among the toxic elements found in the samples. The samples were subjected to FE-SEM analysis, which reveals the presence of irregularly shaped minerals and unburnt carbon known to reduce the burning efficiency of coal, especially in power plants. Toxicology studies reported in the work suggested that fly-ash is toxic to the environment at higher concentrations than at lower concentrations.

Exposure to coal ash and depression in children aged 6-14 years old

BACKGROUND

When coal is burned for energy, coal ash, a hazardous waste product, is generated. Throughout the world, over 1 billion tons of coal ash is produced yearly. In the United States, over 78 million tons of coal ash was produced in 2019. Fly ash, the main component of coal ash contains neurotoxic metal (loid)s that may affect children's neurodevelopment and mental health. The objective of this study was to investigate the association between fly ash and depressive problems in children aged 6-14 years old.

METHODS

Children and their parents/guardians were recruited from 2015 to 2020. Tobit regression and logistic regression were used to assess the association between coal fly ash and depressive problems. To determine fly ash presence, Scanning Electron Microscopy was conducted on polycarbonate filters containing PM10 from the homes of the study participants. Depressive problems in children were measured using the Depressive Problems DSM and withdrawn/depressed syndromic problem scales of the Child Behavior Checklist.

RESULTS

In covariate-adjusted Tobit regression models, children with fly ash on the filter had higher scores on the DSM Depressive Problems (3.13 points; 95% CI = 0.39, 5.88) compared with children who did not have fly ash on the filter. Logistic regression supported these findings.

CONCLUSION

Coal ash is one of the largest waste streams in the U.S, but it is not classified as a hazardous waste by the Environmental Protection Agency. To our knowledge, no studies have assessed the impact of coal ash on children's mental health. This study highlights the need for further research into the effects of coal ash exposure on children's mental health, and improved regulations on release and storage of coal ash.

A Review of the Impact That Healthcare Risk Waste Treatment Technologies Have on the Environment

Health-Care Risk Waste (HCRW) treatment protects the environment and lives. HCRW is waste from patient diagnostics, immunization, surgery, and therapy. HCRW must be treated before disposal since it pollutes, spreads illnesses, and causes harm. However, waste treatment increases the healthcare sector's carbon footprint, making the healthcare sector a major contributor to anthropogenic climate change. This is because treating HCRW pollutes the environment and requires a lot of energy. Treating HCRW is crucial, but its risks are not well-studied. Unintentionally, treating HCRW leads to climate change. Due to frequent climate-related disasters, present climate-change mitigation strategies are insufficient. All sectors, including healthcare, must act to mitigate and prevent future harms. Healthcare can reduce its carbon footprint to help the environment. All contributing elements must be investigated because healthcare facilities contribute to climate change. We start by evaluating the environmental impact of different HCRW treatment technologies and suggesting strategies to make treatments more sustainable, cost-effective, and reliable to lower the carbon footprint.

A Hybrid Method for Prediction of Ash Fouling on Heat Transfer Surfaces

Soot blowing optimization is a key, but challenging question in the health management of coal-fired power plant boiler. The monitoring and prediction of ash fouling for heat transfer surfaces is an important way to solve this problem. This study provides a hybrid data-driven model based on advanced machine-learning techniques for ash fouling prediction. First, the cleanliness factor is utilized to represent the level of ash fouling, which is the original data from the distributed control system. The wavelet threshold denoising algorithm is employed as the data preprocessing approach. Based on the empirical mode decomposition (EMD), the denoised cleanliness factor data is decoupled into a series of intrinsic mode functions (IMFs) and a residual component. Second, the support vector regression (SVR) model is used to fit the residual, and the Gaussian process regression (GPR) model is applied to estimate the IMFs. The cleanliness factor data of ash accumulation on the heat transfer surface of diverse devices are deployed to appraise the performance of the proposed SVR + GPR model in comparison with the sole SVR, sole GPR, SVR + EDM and GPR + EDM models. The illustrative results prove that the hybrid SVR + GPR model is superior to other models and can obtain satisfactory effects both in one-step- and the multistep-ahead cleanliness factor predictions.

Recent advances in removal of Congo Red dye by adsorption using an industrial waste

The Congo Red dye was removed from a simulated textile wastewater solution using fly ash from a local power plant. The characterisation of fly ash was studied in detail by SEM, EDX, XRD, FTIR, BET surface area and TGA techniques. The influence of four parameters (contact time, initial concentration, adsorbent dose, and temperature) was analysed, the results showing that the adsorption capacity depends on these parameters. Thermodynamic and regeneration investigations as well are presented. The fit to pseudo-second-order kinetics models suggests that the removal process is a chemical adsorption. The Langmuir model fitted the experimental data, with a maximum adsorption capacity of 22.12 mg/g. The research is a preliminary case study that highlights that fly ash posed a very good potential as a material for Congo Red dye removal.

The Influence of Fly Ash on the Foaming Behavior and Flame Retardancy of Polyurethane Grouting Materials

Polyurethane (PU) grouting material has been widely utilized to control water inrush in mining fields. However, the application has been limited by its high cost and poor flame retardancy. Here, we use the fly ash (FA), a waste from coal of the iron-making industry and power plants, as a partial replacement of conventional filler in PU grouting materials to reduce the production cost and the environmental pollution of FA. The surface-modified FA-filled PU (PU/FA) composites were prepared by room-temperature curing. The effects of FA contents (φ) on the structure, foaming behavior, thermal stability, mechanical properties, hydrophobic properties, and flammability of PU grouting materials were examined. Results showed that the higher the φ, the more porous the PU/FA composites are, resulting in a lower density and lower mechanical properties. The relationship between the compression modulus E and the density ρ of the PU/FA composites was E ∝ ρ^1.3. In addition, the surface-modified FA improved the compatibility between the hard and soft segment of PU in the PU/FA composite, giving the composites enhanced thermal stability, high hydrophobicity, and flammability resistance.

Remediation of Azure A Dye from Aqueous Solution by Using Surface-Modified Coal Fly Ash Extracted Ferrospheres by Mineral Acids and Toxicity Assessment

The Indian coal fly ash (CFA) is composed of 5-15% ferrous fractions. The variation in percentage depends on the source of coal and the operating conditions of the thermal power plants. The present research work reports the recovery of ferrous particles from CFA by the wet magnetic separation method. The morphological, elemental, and chemical properties of the extracted ferrous fractions were analyzed. In order to achieve surface-modified ferrospheres, the extracted ferrospheres were treated with concentrated HCl followed by sonication. The instrumental analysis reported the ferrous composition is around 16% by weight and belongs to class F. The toxicity of CFA was determined on normal human lung (BEAS-2B) cells using MTS assay. The results showed that CFA’s induced cell toxicity in a dose-dependent manner. The ferrous particles were spherically shaped with various sizes ranging from 200 nm to 7000 nm. It was crystalline in nature and is a mixture of hematite and magnetite. The particles were found to be associated with alumina, silica, oxygen, and traces of Ca, Mg, Ti, and C. The surface-modified ferrospheres were used for the remediation of Azure A dye by batch adsorption study. The removal percentage of dye was 25.03%, within 30 minutes at neutral pH, i.e., 7.2. The surface-modified ferrospheres show potential as an alternate, more economical, and reusable adsorbent for the remediation of Azure A dye in the industries or in common effluent treatment plants. Moreover, the recovery of surface-modified ferrospheres using an external magnet and the reuse of the particles make the material much economical for dye removal at an industrial scale.

Fly Ash as an Ingredient in the Contaminated Soil Stabilization Process

Fly ash is the main by-product of coal combustion characterized by a large specific surface area. In addition to oxides, it also contains unburned coal and trace elements. This study aimed to investigate the possibility of using fly ash from pit-coal combustion (CFA) for the treatment of benzene-contaminated soil (S). The CFA was used as a mixture with Portland cement (PC) (70% PC + 30% CFA). The soil was treated with a PC-CFA mixture in amounts of 40, 60, and 80% of soil mass. During the process, the concentration of benzene was monitored with the flame-ionization detector. Produced monoliths (S+(PC-CFA)x) were tested for compressive strength and capillary water absorption. The experiment confirmed that the PC-CFA mixture limited benzene emission. The highest reduction in benzene concentration (34–39%) was observed for samples treated with the PC-CFA mixture in an amount of 80% (S+(PC-CFA)80). The average compressive strength of monoliths S+(PC-CFA)40, S+(PC-CFA)60, and S+(PC-CFA)80 was 0.57, 4.53, and 6.79 MPa, respectively. The water absorption values were in the range of 15–22% dm.

Polycyclic aromatic hydrocarbons in fine road dust from a coal-utilization city: Spatial distribution, source diagnosis and risk assessment

Coal combustion can release large amounts of polycyclic aromatic hydrocarbons (PAHs), which persist in various environment matrices (e.g., road dust) and hence cause the carcinogenic risk to human health. In this study, an exhaustive characterization of road dust samples coupling their physicochemical characteristics and stable isotope compositions (δ¹³C and δ¹⁵N) was conducted to evaluate the source, level, spatial distribution, and carcinogenic risk of PAHs in a typical coal-utilization city. Concentrations of Σ₁₆ PAHs ranged from 605.5 to 25,374.3 ng/g with a mean concentration of 4083.0 ng/g. Pollution levels of sites around the coal-fired power plant (Zone 1) were significantly higher than those in other zones (p < 0.05). PAH concentration showed significant correlations with both C and N fractions (p < 0.01). Compositions of δ¹³C and δ¹⁵N in road dust coupled to principal component analysis and the partitions and diagnostic ratios of PAHs contributed to associating road dust to several local sources of contamination. Coal combustion and vehicular exhaust were major sources of PAHs around the power plant and urban area. Results of incremental lifetime cancer risk showed 81.5% of all sampling sites suffered potential risk (>10^-6) for both adults and children, while children around the power plant suffered the highest risk. Despite the estimation of only potential risk being posed by PAHs in road dust, human exposure to the various environmental matrices, scientific and systematic assessment of carcinogenic risks by PAHs in the total environment warrants further investigations.

Proximity to coal-fired power plants and neurobehavioral symptoms in children

BACKGROUND

Coal-fired power plants are a major source of air pollution that can impact children's health. Limited research has explored if proximity to coal-fired power plants contributes to children's neurobehavioral disorders.

OBJECTIVE

This community-based study collected primary data to investigate the relationships of residential proximity to power plants and neurobehavioral problems in children.

METHODS

235 participants aged 6-14 years who lived within 10 miles of two power plants were recruited. Exposure to particulate matter ≤10 μm (PM₁₀) was measured in children's homes using personal modular impactors. Neurobehavioral symptoms were assessed using the Child Behavior Checklist (CBCL). Multiple regression models were performed to test the hypothesized associations between proximity/exposure and neurobehavioral symptoms. Geospatial statistical methods were used to map the spatial patterns of exposure and neurobehavioral symptoms.

RESULTS

A small proportion of the variations of neurobehavioral problems (social problems, affective problems, and anxiety problems) were explained by the regression models in which distance to power plants, traffic proximity, and neighborhood poverty was statistically associated with the neurobehavioral health outcomes. Statistically significant hot spots of participants who had elevated levels of attention deficit hyperactivity disorder, anxiety, and social problems were observed in the vicinity of the two power plants.

SIGNIFICANCE

Results of this study suggest an adverse impact of proximity to power plants on children's neurobehavioral health. Although coal-fired power plants are being phased out in the US, health concern about exposure from coal ash storage facilities remains. Furthermore, other countries in the world are increasing coal use and generating millions of tons of pollutants and coal ash. Findings from this study can inform public health policies to reduce children's risk of neurobehavioral symptoms in relation to proximity to power plants.

Fast Screening of Coal Fly Ash with Potential for Rare Earth Element Recovery by Electron Paramagnetic Resonance Spectroscopy

Rare earth elements (REYs) are in increasing global demand, but their mining is costly and environmentally destructive. Coal fly ash (CFA) is a promising alternative source of REYs, but it is necessary to identify CFA with sufficiently high REY concentrations. This study proposes the use of electron paramagnetic resonance (EPR) spectroscopy as part of a simple method to identify CFAs with adequate REY concentrations. The EPR spectra of CFA samples taken from 186 Chinese commercial coal-fired power plants were analyzed. The results suggest that CFAs without evident 6-fold resonances are worth recycling (REY concentrations of 416 ± 108 mg/kg), while those with conspicuous 6-fold resonances are not worth recycling (REY concentrations of 55 ± 26 mg/kg). This is probably due to isomorphic substitution of Ca(II) for Mn(II) and REY(III), resulting in low concentrations of Mn(II) and REY(III) in Ca-rich CFAs. This EPR evaluation method does not require specialized sample preparation, professional skills, or secondary data analysis and has potential global significance in the fast screening of CFAs with REY-recycling potential.

Manganese body burden in children is associated with reduced visual motor and attention skills

Manganese (Mn) is an essential element, however, children with moderate to high Mn exposure can exhibit neurobehavioral impairments. One way Mn appears to affect brain function is through altering dopaminergic systems involved with motor and cognitive control including frontal - striatal brain systems. Based on the risk for motor and attention problems, we evaluated neurobehavioral function in 255 children at risk for Mn exposure due to living in proximity to coal ash storage sites. Proton Induced X-ray Emissions (PIXE) analysis was conducted on finger and toenails samples. Multiple neuropsychological tests were completed with the children. Fifty-five children had Mn concentrations above the limit of detection (LOD) (median concentration = 3.95 ppm). Children with detectable Mn concentrations had reduced visual motor skills (β = -5.62, CI: -9.11, -2.12, p = 0.008) and more problems with sustained attention, based on incorrect responses on a computerized attention test, (β = 0.40, CI: 0.21, 0.59, p < 0.001) compared with children who had Mn concentrations below the LOD. Findings suggest that Mn exposure impacts attention and motor control possibly due to neurotoxicity involving basal ganglia and forebrain regions. Visual-motor and attention tests may provide a sensitive measure of Mn neurotoxicity, useful for evaluating the effects of exposure in children and leading to better treatment options.

Fundamental features of mesoporous functional materials influencing the efficiency of removal of VOCs from aqueous systems: A review

Volatile organic compounds (VOCs) are harmful contaminants that are emitted into the environment as a result of various commercial, industrial, and domestic practices. Their presence in water leads to pollution and poses a huge threat to the ecological environment and human health. They are typically released into the environment through a spill or inappropriate disposal which allows the chemicals to get absorbed into the ground or enter the sewage system. Thus far, several treatment methods have been developed to remove VOCs from water, including steam stripping or air stripping, ion exchange, filtration, adsorption, and application of various types of sorbents. Due to their cost-effectiveness and efficiency, the use of mesoporous materials, especially those synthesized from coal fly ash (FA), is recognized as the most promising strategy for slowing down the impact of VOCs. This study is believed to be the first to assess the advances made in improving the adsorption of VOCs by different functional mesoporous materials (FA, zeolites, mesoporous silica, metal organic frameworks). The impact associated with the properties of these materials is carefully summarized in this paper, in regard to their solid-state characteristics, material synthesis method, and surface modification. In addition, their chemical and physical interactions in solution, the reaction kinetics, and the influence of temperature and pH are described in detail. The aim of this work was to compare the sorption properties of the materials synthesized from FA with more complex mesoporous materials. This overview provides a comprehensive understanding of VOC removal from water systems using various functional materials, as well as helps in identifying the materials that may play a key role in the future.

Evaluation and Integration of Geochemical Indicators for Detecting Trace Levels of Coal Fly Ash in Soils

Coal combustion residuals (CCRs), in particular, coal fly ash, are one of the major industrial solid wastes in the U.S., and due to their high concentrations of toxic elements, they could pose environmental and human health risks. Yet detecting coal fly ash in the environment is challenging given its small particle size. Here, we explore the utility and sensitivity of using geochemical indicators (trace elements, Ra nuclides, and Pb stable isotopes), combined with physical observation by optical point counting, for detecting the presence of trace levels of coal fly ash particles in surface soils near two coal-fired power plants in North Carolina and Tennessee. Through experimental work, mixing models, and field data, we show that trace elements can serve as a first-order detection tool for fly ash presence in surface soils; however, the accuracy and sensitivity of detection is limited for cases with low fly ash proportion (i.e., <10%) in the soil, which requires the integration of more robust Ra and Pb isotopic tracers. This study revealed the presence of fly ash particles in surface soils from both the recreational and residential areas, which suggests the fugitive emission of fly ash from the nearby coal-fired power plants.

Nail Samples of Children Living near Coal Ash Storage Facilities Suggest Fly Ash Exposure and Elevated Concentrations of Metal(loid)s

Children who live near coal-fired power plants are exposed to coal fly ash, which is stored in landfills and surface impoundments near residential communities. Fly ash has the potential to be released as fugitive dust. Using data collected from 263 children living within 10 miles of coal ash storage facilities in Jefferson and Bullitt Counties, Kentucky, USA, we quantified the elements found in nail samples. Furthermore, using principal component analysis (PCA), we investigated whether metal(loid)s that are predominately found in fly ash loaded together to indicate potential exposure to fly ash. Concentrations of several neurotoxic metal(loid)s, such as chromium, manganese, and zinc, were higher than concentrations reported in other studies of both healthy and environmentally exposed children. From PCA, it was determined that iron, aluminum, and silicon in fly ash were found to load together in the nails of children living near coal ash storage facilities. These metal(loid)s were also highly correlated with each other. Last, results of geospatial analyses partially validated our hypothesis that children's proximity to power plants was associated with elevated levels of concentrations of fly ash metal(loid)s in nails. Taken together, nail samples may be a powerful tool in detecting exposure to fly ash.

Protocol for measuring indoor exposure to coal fly ash and heavy metals, and neurobehavioural symptoms in children aged 6 to 14 years old

INTRODUCTION

Fly ash is a waste product generated from burning coal for electricity. It is comprised of spherical particles ranging in size from 0.1 µm to over 100 µm in diameter that contain trace levels of heavy metals. Large countries such as China and India generate over 100 million tons per year while smaller countries like Italy and France generate 2 to 3 million tons per year. The USA generates over 36 million tons of ash, making it one of the largest industrial waste streams in the nation. Fly ash is stored in landfills and surface impoundments exposing communities to fugitive dust and heavy metals that leach into the groundwater. Limited information exists on the health impact of exposure to fly ash. This protocol represents the first research to assess children's exposure to coal fly ash and neurobehavioural outcomes.

METHODS

We measure indoor exposure to fly ash and heavy metals, and neurobehavioural symptoms in children aged 6 to 14 years old. Using air pollution samplers and lift tape samples, we collect particulate matter ≤10 µm that is analysed for fly ash and heavy metals. Toenails and fingernails are collected to assess body burden for 72 chemical elements. Using the Behavioural Assessment and Research System and the Child Behaviour Checklist, we collect information on neurobehavioural outcomes. Data collection began in September 2015 and will continue until February 2021.

ETHICS AND DISSEMINATION

This study was approved by the Institutional Review Boards of the University of Louisville (#14.1069) and the University of Alabama at Birmingham (#300003807). We have collected data from 267 children who live within 10 miles of two power plants. Children are at a greater risk for environmental exposure which justifies the rationale for this study. Results of this study will be distributed at conferences, in peer-reviewed journals and to the participants of the study.

Associations of the Behavioral Assessment and Research System (BARS) neurobehavioral outcomes with attention problems in children living near coal ash storage sites

Environmental exposures have been linked to childhood problems with overactivity, attention, and impulse control, and an increased risk of attention deficit hyperactivity disorder (ADHD) diagnosis. Two approaches to identify these types of exposure-related neurobehavioral problems include the use of computerized tests, such as the Behavioral Assessment and Research System (BARS), as well as the use of behavior rating scales. To assess comparability of these two types of measures, we analyzed data from 281 children aged 6 to 14 years enrolled in a 5-year research study investigating coal ash exposure and neurobehavioral health. All children lived in proximity of coal ash storage sites. We administered six computer tests from the BARS and obtained behavior measures from the parent-completed Child Behavior Checklist (CBCL) ADHD DSM oriented scale. BARS test performance was associated with age indicating that the tests could be used to evaluate neurodevelopmental changes over time or across a wide age range. Tests within the BARS including Continuous Performance (CPT) false alarm (standardized estimate 1.57, 95% confidence interval (CI) (0.67, 2.48), adjusted p = 0.006), Selective Attention (SAT) wrong count (standardized estimate 2.8, 95% CI (1.17, 4.44), adjusted p = 0.006), and SAT proportion correct (standardized estimate -2.45, 95% CI (-4.01, -0.88), adjusted p = 0.01) were associated with attention and impulse control problems on the CBCL after adjustment for multiple comparisons. Findings support that the BARS can contribute to research on environmental exposures by assessing subclinical behaviors related to ADHD such as sustained attention, impulse control, response inhibition, associative learning, and short-term memory. Future research can examine relationships of these BARS measures with biomarkers of neurotoxic exposures related to living near coal ash storage sites to better identify the potential risk for ADHD-related behaviors among children living near coal ash storage sites.