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Rare earth elements (REE) have been recognised as critical raw materials, crucial for many clean technologies. As the gap between their global demand and supply increases, the search for their alternative resources becomes more and more important, especially for the countries which depend highly on their import. Coal fly ash (CFA), which when not utilised is considered waste, has been regarded as the possible source of many elements, including REE. Due to the increase in the energy demand, CFA production is expected to grow, making research into the use of this material a necessity. As Poland is the second biggest coal consumer in the European Union, the authors have studied different coal fly ashes from ten Polish power plants for their rare earth element content. All the fly ashes have a broadly similar distribution of rear earth elements, with light REE being dominant. Most of the samples have REE content relatively high and according to Seredin and Dai (Int J Coal Geol 94: 67–93, 2012 ) classification can be considered promising REE raw materials.

Exposure to coal and coal ashes can cause harmful effects in in vitro and in vivo systems, mainly by the induction of oxidative damage. The aim of this work was to assess cytotoxic and genotoxic effects using the V79 cell line treated with coal and coal fly ash particles derived from a coal power plant located in Santa Catarina, Brazil. Two coal samples (COAL11 and COAL16) and two coal fly ash samples (CFA11 and CFA16) were included in this study. COAL16 was co-firing with a mixture of fuel oil and diesel oil. The comet assay data showed that exposure of V79 cells to coal and coal fly ash particles induced primary DNA lesions. Application of lesion-specific endonucleases (FPG and ENDO III) demonstrated increased DNA effects indicating the presence of high amounts of oxidative DNA lesions. The cytokinesis-block micronucleus cytome assay analysis showed that exposure of V79 cells to high concentrations of coal and coal fly ash particles induced cytotoxic effects (apoptosis and necrosis) and chromosomal instability (nucleoplasmic bridges, nuclear buds, and micronucleus (MN) formation). These results may be associated with compounds contained in the surface of the particles as hazardous elements, ultrafine/nanoparticles, and polycyclic aromatic hydrocarbons (PAHs) which were detected in the samples. Graphical abstract ᅟ

Present study evaluated the susceptibility of essential nutrients available in thermoelectric coal fly ash (CFA) for the cultivation of screened microalgae maintained in demineralized water − CFA (DMW + CFA) as culture medium. Different concentration of CFA culture medium was prepared from 0.5 to 4.0 g/L of CFA, but the low nitrate and phosphate content in culture medium was not plausible for growth of cells; therefore, additional NaNO 3 and KH 2 PO 4 were added. Culture mediums were inoculated with characterized microalgae chlorococcum sp. and placed in ambient dark/light period for growth study which was measured with time by optical density. Max. OD @ 680 and @750 nm observed as 0.396 ± 0.073 and 0.306 ± 0.072 for 0.5 g/L culture medium, respectively. Max. biomass yield was 562.21 ± 95.54 mg/L for 0.5 g/L culture medium; however, yield was 40.00% low as compared to BG-11 culture. Max. sp. growth rate observed was 0.253 ± 0.007 d −1 for 0.5 g/L. The max total lipid was 139.0 ± 7.5 mg/L for 1.0 g/L culture, which was comparable with BG-11. NO 3 -N and PO 4 -P concentration reduced > 90% whereas Na + , K + and Ca + content was reduced > 75.00–90.00%. ORP was also intriguingly measured for oxidative state of culture medium during growth phase and found to be maintained between + 350 and  + 25 mV. Max. total chlorophyll analysed was 4.64 ± 0.56 µg/ml. The results support that CFA may be used as culture medium for chlorococcum sp. for biomass and lipid production and subsequent nutrient recovery from CFA.

Globally, millions of tons of coal fly ash (CFA) are generated per year, and the majority of this material is usually stored in stock piles or landfills, and in a long-term, it can be an environmental hazard if rainwater infiltrates the ashes. Long-term leaching studies of Brazilian ashes are scarce. The purpose of this study was to evaluate arsenic, cadmium, molybdenum, lead, and zinc leaching behavior from a Brazilian CFA by a column experiment designed to simulate field conditions: slightly acid rain considering seasonality of precipitation and temperature for a long-term leaching period (336 days). All elements were leached from CFA, except lead. Elements leaching behavior was influenced by leaching time, leaching volume, and temperature. Higher leachability of As and Cd from CFA during warm and wet season was observed. Results indicate a potential risk to soil and groundwater, since ashes are usually stored in uncovered fields on power plants vicinity.

In order to realize the high value-added reuse of coal fly ash, a reusable Fe-modified fly ash catalyst was synthesized for ozone catalysis degradation of chemical oxygen demand (COD) in wastewater. Through enhancement of the pretreatment procedure and FeOx modification, the resulting fly ash with Fe modification demonstrated increased specific surface area and porosity. The presence of Fe loading significantly enhances the reactivity of surface oxidizing reactive species, particularly oxygen vacancy, leading to improved adsorption and activation properties towards ozone molecules. Sodium acetate is chosen as a probe for contaminants due to its status as a small organic substance that remains resistant to further direct oxidation by ozone. This makes it suitable for evaluating the catalyst’s effectiveness in degrading chemical oxygen demand (COD). The quantitative detection of free radicals revealed the generation of •O2− was nearly 10 times that of •OH and dominated the reaction. This study showcases the potential of fly ash, an industrial byproduct, to be utilized as a cost-effective and easily prepared catalyst with consistent physical and chemical characteristics.

Two magnetic supports with different morphologies and particle sizes were designed and prepared for cellulase immobilization based on chitosan and industrial by-product magnetic coal fly ash (MCFA). One was prepared by coating chitosan onto spherical MCFA particles to form non-porous MCFA@chitosan gel microcomposites (Support I) with a size of several micrometers, and the other was prepared using the suspension method to form porous MCFA/chitosan gel beads (Support II) with a size of several hundred micrometers. Cellulase was covalent binding to the support by glutaraldehyde activation method. The morphology, structure and magnetic property of immobilized cellulase were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and a vibrating-sample magnetometer. The cellulase loading on Support I was 85.8 mg/g with a relatlvely high activity recovery of 76.6%, but the immobilized cellulase exhibited low thermal stability. The cellulase loading on Support II was 76.8 mg/g with a relative low activity recovery of 51.9%, but the immobilized cellulase showed high thermal stability. Cellulase immobilized on Support I had a glucose productivity of 219.8 mg glucose/g CMC and remained 69.9% of the original after 10 cycles; whereas the glucose productivity was 246.4 mg glucose/g CMC and kept 75.5% of its initial value after 10 repeated uses for Support II immobilized cellulase. The results indicate that the two supports can be used as cheap and effective supports to immobilize enzymes.

Characteristics of ZSM-5 synthesized from H2SO4-treated coal fly ash and fused coal fly ash extracts are compared in this study. In the synthesis process, fused coal fly ash extract (without an additional silica source) was used in the synthesis of ZSM-5. The effect of the structure-directing agent (tetrapropylammonium bromide, 1,6-hexanediamine or 1-propylamine) on the properties and methanol-to-olefins (MTO) effectiveness of the fly ash-based ZSM-5 was also investigated. A pure ZSM-5 synthesized from the fused coal fly ash extract led to a methanol conversion higher than 90% after 5 h on stream. The template 1,6-hexanediamine led to the synthesis of the most stable fly ash-based catalyst keeping a 44% methanol conversion after 24 h on stream.

● Better packing density and higher early strength of SS-rich geopolymer. ● C-S-H and portlandite as the main hydration phase in SS-rich geopolymer. ● Increased Si/Al of geopolymer gel and better long-term performance of SFA-rich geopolymer. ● Low cost of SFA-SS geopolymers concrete. Geopolymer is a material with high early strength. However, the insufficient durability properties, such as long-term strength, acid-base resistance, freeze–thaw resistance, leaching toxicity, thermal stability, sulfate resistance and carbonation resistance, restrain its practical application. Herein, a long-term stable geopolymer composite with high final strength (ASK1) was synthesized from shell coal gasification fly ash (SFA) and steel slag (SS). Additionally, a geopolymer composite with high early strength (ASK2) was also synthesized for comparison. The results showed that ASK1 exhibited better performance on freezing-thawing resistance, carbonization resistance and heavy metals stabilization compared to the ASK2 at long-term curing. Raising the curing temperature could accelerate the unconfined compressive strength (UCS) development at initial curing ages of 3 to 7 d. Both ASK1 and ASK2 exhibited excellent acid-base and sulfate corrosion resistance. An increase for UCS was seen under KOH solution and MgSO 4 solution corrosion for ASK1. All leaching concentrations of heavy metals out of the two geopolymers were below the standard threshold, even after 50 freezing-thawing cycles. Both ASK1 and ASK2 geopolymer concrete exhibited higher sustainability and economic efficiency than Portland cement concrete. The result of this study not only provides a suitable way for the utilization of industrial solid waste in civil and environmental engineering, but also opens a new approach to improve the long-term stabilities of the geopolymers.

The fundamental purpose of this study was to evaluate the technical feasibility of incorporating fly ash (FA) and dyeing sludge (DS) in the production of brick. An attempt was taken to replace 10% to 100% clay by DS and FA in brick-making by volume. A brick firing kiln was used to burn the uniform-shaped bricks after replacing clay with DS and FA. Size and shape, hardness, soundness, water absorption, efflorescence, dry density, loss of ignition, firing shrinkage, specific gravity, compressive strength, and leaching tests were carried out to study the properties of these bricks. The compressive strength of the brink ranged from 6.25 MPa to 0.33 MPa and indicates a decreasing pattern in strength with the increase in the volume of DS and FA. Only 18.8% water absorption capacity was found in control bricks without DS and FA, while a maximum absorption of 40.19% was found for a particular combination of DS and FA. Similarly, dry density decreased with the increase in the volume of DS and FA. Besides, efflorescence in bricks was found within the allowable limits for certain combinations of DS and FA, which exceeded the allowable limits for other combinations. The presence of heavy metals (Ni, Zn, Cr, Cu, and Pb) in the extraction solution was insignificant. Based on the results of this study, we recommend that up to 10% clay can be substituted with DS and FA without substantially affecting the quality of bricks.

In this study, the silanized coal fly ash (CFA) and silanized nano-/micro-glass fiber (nGF) were simultaneously embedded in vinyl ester resin for improvement in both mechanical properties and mode I interlaminar fracture toughness of carbon fiber-based composite material. The used CFA particles have thermal power plant origin and were grinded with the help of ball mill to obtain the uniform size. The methacryloxy groups were attached to surface of both ground CFA and pristine nGF via silanization process. The homologous mixtures of S-nGF and S-CFA in vinyl ester resin were obtained with the help of high-speed mechanical stirrer and ultrasonic technique. The sheet molding compound method and hot curing process were applied to fabricate the carbon fiber-filled vinyl ester resin-based composite. Many techniques such as FTIR, EDS, rheological testing, mode I interlaminar fracture toughness, tensile strength and SEM were used to investigate the characteristics of silanized additives, the uncured matrices as well as the carbon fiber-based composite materials. The incorporation of both 0.1 wt% S-nGF and 1 wt% S-CFA into VE resin helps to improve the tensile strength, tensile modulus and the mode I interlaminar fracture toughness ( G IC ) of carbon fiber-based composites (CFRP) by 61.39%, 39.83% and 48.61%, respectively, when compared with pristine composite material. The fracture toughness surface of modified VE was tougher and rougher as a result of higher fracture toughness, while the pristine VE exhibited the smooth surface.