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In this work, a zwitterion adsorbent which consists of crosslinked chitosan-benzil/algae/coal fly ash (CS-BZ/Alg/FA) was developed for the removal of two structurally different anionic dye (remazol brilliant blue R (RBBR)) and a cationic dye (thionine (THN)). The physicochemical characteristics of CS-BZ/Alg/FA were investigated by several analytical techniques including specific surface area, XRD, FTIR, FESEM and EDX analyses. Moreover, response surface methodology and Box–Behnken design (RSM–BBD) was adopted as a statistical tool to optimize the adsorption operational parameters for THN and RBBR dyes removal. Thus, the optimal adsorption conditions were determined as follows: CS-BZ/Alg/FA dose of 0.1 g/100 mL, solution pH 10 for THN, and solution pH 4 for RBBR. Adsorption equilibrium isotherm data for RBBR and THN dyes by CS-BZ/Alg/FA were well described by Freundlich (multilayer adsorption) and Langmuir (monolayer adsorption) isotherm models respectively. Thus, the maximum adsorption capacities of CS-BZ/Alg/FA towards THN and RBBR were found to be 69.0 mg/g and 259.9 mg/g, respectively at 25 °C. Moreover, the pseudo second order model accurately represents the kinetic data for the adsorption of both THN and RBBR dyes. The adsorption thermodynamic functions indicate the adsorption process of THN and RBBR was spontaneous and endothermic in nature. Ultimately, this research presents the CS-BZ/Alg/FA as an eco-friendly amphoteric adsorbent with preferable capability for capturing anionic and cationic dyes from aqueous environment. [ABSTRACT FROM AUTHOR]

The effects of class-F coal fly ash (CFA) as cement replacement in the paste and mortar formulation at different CFA-to-binder ratios (CBR) with varying water-to-binder ratios (WBR) were investigated and further evaluated using multivariate nonlinear regression to elucidate their influence on consistency, setting time, and water requirement. It was found that the required WBR for achieving normal consistency of formulated paste and mortar can be predicted using the obtained regression models. Water requirements for mortar formulation could also be predicted, given that the water requirement for paste formulation is known. The influence of partially replacing cement in mortar formulations on hardened mortar properties while ensuring formulations were at normal consistency was also investigated with replacements of up to 20 wt.% resulted in a mortar with improved strength, especially after curing for 28 and 56 days, as the CFA exhibits its inherent pozzolanic activity. [ABSTRACT FROM AUTHOR]

This study delves into a comprehensive review of coal mining, production, and consumption in India, focusing on thermal power plants and the generation of coal fly ash (CFA). It assesses CFA’s physicochemical properties and potential applications, as well as its environmental and technological management aspects. CFA, an industrial by-product, has gained importance due to increasing disposal challenges and environmental concerns. Reviewing global trends, the study highlights the economic, environmental, and sustainability implications of CFA utilization, emphasizing both opportunities and challenges. CFA has valuable properties for use in construction materials, agriculture, water purification, wastewater treatment, metal recovery, ceramics, and paint, contributing to environmental pollution mitigation and waste recycling. However, challenges such as metal leaching variability and logistical barriers hinder its widespread adoption. Regulatory support, including preferential recycling policies, is identified as critical to promoting CFA utilization. The future of CFA utilization in India looks promising, bolstered by initiatives like the “Swachh Bharat Mission” and the “National Clean Energy Fund.” Recommendations include optimizing CFA’s agricultural applications by studying long-term effects on soil health and productivity. Emerging technologies, such as blending CFA with organic and industrial wastes, biosolids, and innovative materials, hold the potential for enhancing sustainability, highlighting the need for further research. [ABSTRACT FROM AUTHOR]

Abstract\nNOVELTY STATEMENTIn the current study, coal fly ash contaminated soil was collected in and around Mettur Thermal Power Station, Salem district, Tamil Nadu. The metal concentrations present in the coal fly ash soil samples were analyzed and also used for the isolation of bacteria. The isolates were screened for their multi-metal resistance against three heavy metals (Cu, Ag and Pb) and plant growth-promoting traits (siderophore, phosphate solubilization, IAA, cellulase, HCN, and ammonia production). Among the 12 isolates, the WA4 strain revealed promising results for both metal-resistant and plant growth-promoting activity. In the in vitro pot experiment, Spinacia oleracea (Palak), Red amaranth (Red spinach), Capsicum annum (Green chilly) and Solanum melongena (Brinjal) plants were grown in ash-contaminated soil treated with different concentrations of selected bacterial inoculum (25%, 50%, 75% and 100%) along with a control pot. The results of the study indicated that the ash-contaminated soil treated with bacterial inoculum distinctly increased the growth of plants when compared to untreated soil (control). Thus, the best-performing strain WA4 could be utilized as a good bio-stimulant for promoting the growth of selected plants in the re-vegetation programs of ash-contaminated soil.The novelty of the experimental work relies on the phytoremediation of heavy metals in coal fly ash-contaminated soil from Mettur Thermal Power Station, Salem District, Tamil Nadu. A significant prospect for phytoextraction of heavy metals (Cu, Ag and Pb) was seen by utilizing potent bacteria Stutzerimonas stutzeri in association with common food crops (Red amaranth, S. oleracea, C. annum, S. melongena). The plants had optimum protein, sugars, biomass, chlorophyll, flavonoids, and phenolic content implying their effectiveness in heavy metal cleanup. Furthermore, there was an upsurge in CAT and POD enzymes which reduces ROS in plants. The maximum absorption of heavy metals was observed in Red amaranth with Ag (0.38 ± 0.09 mg/kg), Pb (0.20 ± 0.30 mg/kg), and Cu (0.45 ± 0.64 mg/kg) followed by S. oleracea with Ag (0.22 ± 0.16 mg/kg), Pb (0.10 ± 0.44 mg/kg), and Cu (0.24 ± 0.08 mg/kg). [ABSTRACT FROM AUTHOR]

Coal fired power plants are significant contributors to CO2 emissions and produce solid waste in the form of coal fly ash, posing severe environmental challenges. This study explores the application of dry-impregnated coal fly ash for CO2 capture from gas stream. The modification of coal fly ash was achieved using alkaline earth metal oxides, specifically CaO and MgO, to alter its physical and chemical properties. Characterization techniques like X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and BET (Brunauer–Emmett–Teller) analysis were employed for physio-chemical changes in the adsorbent. Breakthrough experiments were conducted using a laboratory-scale fixed packed-bed reactor to assess the influence of temperature and gas flow rate on CO2 adsorption. Among the synthesized sorbents, calcium oxide-impregnated ash showed the highest CO2 uptake capacity, achieving 9.41 mg/g at 30 °C and a flow rate of 20 L/hr under atmospheric pressure. Isotherm modeling indicated a heterogeneous adsorbent surface, with the data best fitting the Sips isotherm model. Furthermore, the adsorption data conformed well to the Yoon-Nelson and Thomas kinetic models, affirming their relevance in characterizing the adsorption process under varying conditions. This research emphasizes the potential of coal fly ash—an abundant, cost-free material—as an effective CO2 adsorbent, contributing to both CO2 mitigation and landfill waste reduction. [ABSTRACT FROM AUTHOR]

The coal-fired power plant fly ash (FA) and bottom ash (BA) are gradually used as alternative materials in the concrete. However, knowledge of the leaching characteristics of using both incinerator ashes in concrete production is lacking. This work aimed to evaluate the leaching behavior of the FA and BA used in concrete production by employing batch and tank leaching tests. The outcomes of both leaching tests showed that there was no considerable leaching of any trace elements to the environment, and it remains much lower than standard limitations for utilization as construction materials. The results of cumulative mass discharge showed that the slope of flux time for all elements was less than 0.4 and because of that, primary surface wash-off was the main discharge process of all the heavy metals. Strength test results revealed that there was not much difference between coal ash concrete (CAC) and the control mix at the initial age of curing time. Despite that, at a long period of curing time (180 days), the compressive strength of CAC containing 20% FA as cement replacement and 100% BA as fine aggregate replacement increased by 76% due to the pozzolanic reaction of BA and FA in comparison to the normal concrete, while, due to the high porosity of BA, the workability of CAC decreased by 50%. The outcomes of the current work revealed that the combined use of FA and BA can be counted as a promising alternative in the production of sustainable concrete for structural applications toward sustainable development. [ABSTRACT FROM AUTHOR]

AbstractDye contamination of water is a global issue with significant environmental and health risks. This research explores the use of metal organic framework-5 (MOF-5) adsorbents modified with coal fly ash to effectively remove malachite green (MG) dye from water, addressing global dye pollution. Preliminary batch adsorption experiments showed that the addition of CFA to MOF-5 significantly increased the removal efficiency of MG dye (77.90 ± 1.74%) compared to using pristine MOF-5 (30.00 ± 2.14%). Batch adsorption studies showed that MG adsorption efficiency increased with shaking rate and contact time but decreased with adsorbent dosage. Temperature study reveals exothermic behavior of adsorption process. MOF-5/CFA adsorbents can be regenerated for up to four cycles. The results demonstrated that the highest adsorption efficiency of 80.32 ± 0.90% was achieved under the following conditions: a stirring speed of 300 rpm, a dosage of 0.3 g of MOF-5/CFA adsorbent, a temperature of 27 °C, 2 h contact time, and an initial dye concentration of 100 mg/L. Analysis of adsorption isotherms and kinetics revealed that the Langmuir isotherm and pseudo-second-order kinetic models provided the most accurate fit to the experimental data. FTIR analysis revealed significant functional groups in the prepared adsorbent and only minor spectral changes in the spent adsorbents. SEM analysis showed a rough, porous MOF-5/CFA surface before dye adsorption, becoming smoother and less porous afterwards. This study demonstrates the promise of MOF-5/CFA as an alternative adsorbent for the removal of MG dyes from water, paving the way for advances in wastewater treatment and the sustainable use of industrial waste materials. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) have been identified as valuable and critical raw materials, vital for numerous technologies and applications. With the increasing demand for and supply gap in REEs, many research studies have focused on alternative sources of REEs. This study involved an elemental and mineralogical characterisation of discarded coal from a coal plant and coal fly ash (CFA) from a power station in South Africa for REE presence. XRD results revealed that the discard coal sample consisted mainly of kaolinite, pyrite, siderite, quartz, calcite, gypsum, and muscovite, whereas CFA contained abundant glassy amorphous phases, alumina silicates, quartz, gypsum, calcite, and minute levels of muscovite and hematite. SEM-EDAX showed REE-carrying grains containing phosphorus in both discard coal and CFA samples. This was followed by investigating the leaching potential of REEs using hydrochloric acid from discard coal and CFA. This research's potential impact is possibly providing a new and sustainable source of REEs. For that purpose, multiple batch leaching tests were performed to investigate the effects of temperature and acid concentration on the leaching efficiencies of REEs from discard coal and CFA. The experimental results indicated that temperature strongly influences REE leaching efficiency, while acid concentration has a lesser impact. This study identifies the best leaching conditions for the total REE recovery as 1 M HCl and 80 °C for discard coal and CFA. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) provide a promising alternative to traditional solar technologies, as they offer a unique mix of cost-effectiveness, adaptability, and the possibility of achieving high efficiency. This study aims to investigate the effect of SiO2 purity obtained from coal fly ash on the photoelectric performance of DSSCs. The study focuses on varying the purity of extracted SiO2 from coal fly ash as a counter-electrode material and examining its impact on the efficiency of DSSCs. The efficiency of DSSCs was assessed by evaluating the performance of several various SiO2 purity materials for counter-electrode materials. The performance testing of DSSCs revealed that the counter electrode material, consisting of artificial SiO2 with a purity of 99.9%, achieved the highest efficiency of 0.0113%. Subsequently, DSSCs were fabricated using counter-electrode materials derived from coal fly ash with a purity of 52.91%. These DSSCs demonstrated an efficiency of 0.0076%. DSSCs utilizing SiO2 with a purity of 91.20% exhibited an efficiency of 0.0062%. Dye-sensitized solar cells utilizing a counter electrode material composed of SiO2 with a purity level of 72.54% demonstrated an efficiency of 0.0061%. The results showed that the level of SiO2 purity obtained from coal fly ash has a substantial impact on the photoelectric performance of DSSCs, since higher purity of SiO2 is associated with improved efficiency. [ABSTRACT FROM AUTHOR]

Combustion of coal at thermal power plants generates enormous amounts of coal fly ash (CFA). Proper disposal of CFA is an important issue today because environmental problems are considered a burning issue worldwide. On the other hand, groundnut shells (GNS), regarded as agricultural waste in general, litter landfills everywhere and create soil degradation. Since both CFA and GNS contain abundant silica, this work focuses on extracting amorphous silica from these materials through a total dissolution–precipitation process. The silica was extracted from it and used to prepare titanium oxide (TiO₂) hybrids. The GNSS were extracted from GNS, and the CFAS was extracted from the CFA. The methods used were based on sol–gel. These hybrids were further tested for the performance of their solar cells in dissolving dyes. The overall results of the obtained physical properties of CFAS and GNSS are similar to those of conventional silica. More importantly, TiO₂/GNSS and TiO₂/CFAS hybrids showed enhanced photocatalytic efficiency compared to the pure TiO₂. Therefore, it is evidence of repurposing CFA and GNS, which have high potential for use as sustainable applications in renewable energy and environmental remediation. [ABSTRACT FROM AUTHOR]

The properties of coal fly ash vary significantly depending on factors such as coal type, combustion conditions, and flue gas emission reduction methods. This study investigates the influence of particle size fractionation on the chemical composition, mineralogical structure, and thermal behaviour of two types of fly ash: high calcium ash derived from lignite (S1) and silica-rich ash from bituminous coal (S2). Dry aerodynamic separation was used to obtain distinct size fractions, which were then subjected to a comprehensive characterisation including X-ray fluorescence, X-ray diffraction, scanning electron microscopy, and thermal analysis. The results reveal notable differences between the S1 and S2 ashes and between their size fractions. The finer fractions (< 20 μm) of S1 showed an increased calcium and sulphur content, while the coarser fractions (> 100 μm) contained more silica and alumina. The S2 ash exhibited a higher overall silica content, with alkali metals concentrated in finer fractions. Thermal analysis demonstrated distinct behaviours for each type and fraction of ash. Fine fractions of S1 ash showed SO2 emission at elevated temperatures, while S2 ash exhibited greater CO2 gas emission. After thermal treatment, the recrystallisation of the glassy phase was observed for S1, while the S2 ashes were more prone to melting and agglomeration. The study highlights the potential for the customised utilisation of specific ash fractions in various applications, such as geopolymer synthesis, adsorbent materials, and refractory products. This comprehensive characterisation contributes to a better understanding of fly ash properties and their dependence on particle size, providing valuable insights to optimise fly ash utilisation in various industries. The findings suggest strategies for a more efficient use of fly ash resources, particularly relevant in the context of decreasing fly ash availability due to the phase-out of coal power plants. [ABSTRACT FROM AUTHOR]

Zeolites have been increasingly applied in various fields such as energy conversion, environmental remediation, chemical production, and so on, being used as membranes, catalysts, and supports due to their large specific areas and strong gas adsorption. And, developing low-cost strategies for the preparation of zeolites has attracted the extensive attention of researchers. Coal fly ash, waste glass, discard zeolites, and slags are typical industrial wastes and rich in Si and Al, indicating that these industrial wastes can be utilized as alternative raw materials of zeolite synthesis. Firstly, the chemical composition and properties of these industrial wastes are summarized. Then, the strategies involved in synthesizing different zeolites from various industrial wastes are discussed. In addition, the applications of these zeolites are comprehensively reviewed. [ABSTRACT FROM AUTHOR]

Zeolite adsorbents were synthesized through an alkali fusion-hydrothermal process, using coal fly ash as a raw material. Firstly, the coal fly ash was mixed with sodium hydroxide at a mass ratio of 1∶1.2 and then roasted at 850 ℃ for 2 h to obtain the alkali-fused ash. The effects of the Si/Al molar ratio of the precursor, reaction time, temperature, and liquid/solid ratio on the structure of the zeolite adsorbents derived from coal fly ash were investigated through single-factor experiments conducted during the hydrothermal reaction. The synthesized zeolite adsorbents derived from coal fly ash were systematically characterized using X-ray diffractometer (XRD), scanning electron microscope (SEM) and specific surface area and pore size analyzer (BET). Under the optimized conditions of a Si/Al molar ratio of the precursor set at 1.5, a reaction time of 16 h, a reaction temperature of 70 ℃, and a liquid/solid ratio of 8 mL/g in hydrothermal reaction, the relative mass fraction of type X zeolite in the synthesized product was 96.3%, the specific surface area was 489.9 m2/g, and the pore volume was 0.28 cm3/g. Subsequently, the gas adsorption performance of benzene, a typical volatile organic compound, by zeolite adsorbent derived from coal fly ash was investigated and compared with commercial activated carbon. The results showed that at an initial pollutant concentration of 800 μg/L, an adsorption temperature of 100 ℃, a gas flow rate of 200 mL/min, and an adsorbent loading of 0.1 g, the zeolite adsorbents derived from coal fly ash exhibited a saturated adsorption capacity of benzene at 41.5 mg/g, which was higher compared to commercial activated carbon (31.3 mg/g). This study provides a reference for the resource utilization of coal fly ash.

Abstract Zeolite molecular sieves are potential adsorbents for wastewater treatment, characterized by high efficiency, simple process, easy regeneration, and low treatment cost. In this study, zeolite A molecular sieves were prepared using coal fly ash (CFA), which is an effective method for the utilization of CFA. The results showed that the CFA-based zeolite molecular sieves synthesized under optimized conditions exhibited excellent adsorption and removal rates (> 40%) for ammonia–nitrogen in wastewater of different concentrations and properties. The analysis of adsorption kinetics revealed that the adsorption process followed pseudo-second-order kinetics model, indicating that the adsorption of ammonia–nitrogen on zeolite is primarily controlled by chemisorption rather than physisorption. The adsorption process can be divided into two stages, with a higher adsorption rate and a smaller diffusion boundary layer thickness in the first stage, and a lower adsorption rate and an increased diffusion boundary layer thickness in the second stage. This indicates that as the adsorption proceeds, the internal diffusion resistance within the particles gradually increases, leading to a decrease in the adsorption rate until reaching equilibrium, where both the diffusion and adsorption become stable. The adsorption isotherms of ammonia–nitrogen on zeolite A conformed to the assumptions of the Langmuir model, suggesting that the adsorption mechanism primarily involves uniform monolayer adsorption on the surface without intermolecular interactions.

Abstract This study examines the influence of different grain size fractions of coal fly ash on the properties of clay-cement mortars used in flood levee construction. Dry aerodynamic separation and mesh sieving were used to obtain ultrafine, fine, and medium fractions of high-calcium and silica fly ash. The experimental results reveal that the rheological properties of fresh mortars are significantly influenced by these fractions. High-calcium fly ash mortars exhibit high reactivity and rapid increase in viscosity, with finer fractions showing the highest reactivity. Silica ashes show increased reactivity in the later stages of suspension hardening. Their spherical shape contributes to reducing internal friction during flow in initial technological operations. Furthermore, the compressive strength of hardened mortars improves as the particle size decreases for both ashes, resulting in a dense and uniform microstructure. The separation and fractionation of fly ashes contribute to the obtaining of fractions that influence the parameters of clay-cement suspension application on different scales. The results show the potential benefits of ash separation, which can bring advantages in terms of economic viability, engineering performance, and ecological sustainability.

This study examines the influence of different grain size fractions of coal fly ash on the properties of clay-cement mortars used in flood levee construction. Dry aerodynamic separation and mesh sieving were used to obtain ultrafine, fine, and medium fractions of high-calcium and silica fly ash. The experimental results reveal that the rheological properties of fresh mortars are significantly influenced by these fractions. High-calcium fly ash mortars exhibit high reactivity and rapid increase in viscosity, with finer fractions showing the highest reactivity. Silica ashes show increased reactivity in the later stages of suspension hardening. Their spherical shape contributes to reducing internal friction during flow in initial technological operations. Furthermore, the compressive strength of hardened mortars improves as the particle size decreases for both ashes, resulting in a dense and uniform microstructure. The separation and fractionation of fly ashes contribute to the obtaining of fractions that influence the parameters of clay-cement suspension application on different scales. The results show the potential benefits of ash separation, which can bring advantages in terms of economic viability, engineering performance, and ecological sustainability. [ABSTRACT FROM AUTHOR]

Conditioning process intensification is necessary for improving the fly ash flotation effect. Understanding the relationship between conditioning parameters and flotation results is crucial for optimizing the conditioning-flotation process. This study developed a machine learning framework for predicting the yield, loss on ignition, and removal rate of unburned carbon using data from conditioning-flotation experiments. Feature variables of conditioning speed, impeller type, stirred tank diameter, collector dosage, and frother dosage were employed to develop five machine learning models. After tuning the hyper-parameters with GridSearchCV technique, it was found that Random Forest Regression model, eXtreme Gradient Boosting Regression model, and Gradient Boosting Regression model demonstrated good agreements between the predicted data and test data for the yield, loss on ignition, and removal rate of unburned carbon. The maximum R2 values were 0.9184, 0.8339, and 0.9434, respectively, while the minimum MSE values were 3.30, 5.82, and 20.59, respectively. The interpretable analysis using SHapley Additive exPlanations (SHAP) method indicated that conditioning speed was the most significant feature variable affecting the yield, loss on ignition, and removal rate of unburned carbon, while impeller type had a secondary impact. This investigation is expected to reveal the important role of conditioning process intensification in optimizing fly ash flotation. [ABSTRACT FROM AUTHOR]

• The ash melting temperature decreased on the influence of Na2O. • An appropriate ratio of MBA and MFA can effectively reduce the Cr leaching level. • The stabilization of heavy metals was enhanced when vitreous content exceeded 97.7%. • The solidification effect on Mn and Zn was readily apparent. Medical waste incineration ash (MWIA) has significant concentrations of heavy metals, dioxins, and chlorine that, if handled incorrectly, might cause permanent damage to the environment and humans. The low content of calcium (Ca), silicon (Si), and aluminum (Al) is a brand-new challenge for the melting technique of MWIA. This work added coal fly ash (CFA) to explore the effect of melting on the detoxication treatment of MWIA. It was found that the produced vitrification product has a high vitreous content (98.61%) and a low potential ecological risk, with an initial ash solidification rate of 67.38%. By quantitatively assessing the morphological distribution features of heavy metals in ashes before melting and molten products, the stabilization and solidification rules of heavy metals during the melting process were investigated. This work ascertained the feasibility of co-vitrification of MWIA and CFA. In addition, the high-temperature melting and vitrification accelerated the detoxification of MWIA and the solidification of heavy metals. [ABSTRACT FROM AUTHOR]

Utilizing calcium-based adsorbents for CO2 adsorption through cyclic calcination/carbonization is one of the most cost-effective methods for carbon emission reduction. In order to improve the cycle stability of the adsorbents and the capture efficiency of CO2, this study used industrial solid waste coal fly ash for the hydration treatment of calcium-based adsorbent to explore the variations in the cyclic adsorption performance of the adsorbent under different doping ratios and hydration conditions. By means of various characterization techniques, the microscopic mechanism for improving the performance of the modified adsorbent was analyzed from the perspectives of chemical composition, physical structure, and surface functional groups of the adsorbents. The results demonstrated that the modification of coal fly ash could significantly enhance the carbonation performance and cycle stability of the adsorbent in multiple CO2 capture processes. The modified material doped with 5% coal fly ash had the highest total CO2 adsorption capacity, which increased by 13.7% compared to before modification. Additionally, the modified material doped with 10% coal fly ash exhibited the strongest cyclic adsorption capacity, which was 14.0% higher than that before modification, and the adsorption attenuation rate decreased by 32.2%. The characterization results showed that the reaction between calcium oxide and coal fly ash formed CaSiO3 and Ca12Al14O33 during the modification process, which was the primary reason for the improvement in the CO2 capture performance of the modified materials. This study provided a new perspective on the resource utilization of solid waste fly ash and efficient CO2 capture. [ABSTRACT FROM AUTHOR]

Zeolite molecular sieves are potential adsorbents for wastewater treatment, characterized by high efficiency, simple process, easy regeneration, and low treatment cost. In this study, zeolite A molecular sieves were prepared using coal fly ash (CFA), which is an effective method for the utilization of CFA. The results showed that the CFA-based zeolite molecular sieves synthesized under optimized conditions exhibited excellent adsorption and removal rates (> 40%) for ammonia–nitrogen in wastewater of different concentrations and properties. The analysis of adsorption kinetics revealed that the adsorption process followed pseudo-second-order kinetics model, indicating that the adsorption of ammonia–nitrogen on zeolite is primarily controlled by chemisorption rather than physisorption. The adsorption process can be divided into two stages, with a higher adsorption rate and a smaller diffusion boundary layer thickness in the first stage, and a lower adsorption rate and an increased diffusion boundary layer thickness in the second stage. This indicates that as the adsorption proceeds, the internal diffusion resistance within the particles gradually increases, leading to a decrease in the adsorption rate until reaching equilibrium, where both the diffusion and adsorption become stable. The adsorption isotherms of ammonia–nitrogen on zeolite A conformed to the assumptions of the Langmuir model, suggesting that the adsorption mechanism primarily involves uniform monolayer adsorption on the surface without intermolecular interactions. [ABSTRACT FROM AUTHOR]

The compound p-Nitrophenol (p-NP) is widely recognized as a highly toxic nitro-aromatic substance that urgently requires emission control. Reducing p-NP to p-aminophenol (p-AP) not only decreases its toxicity and mineralization properties in nature but also provides a key raw material for the chemical and pharmaceutical industries. The study used coal fly ash (CFA) as a catalyst carrier for synthesizing the p-NP reduction catalyst. Using CFA as an alternative option not only reduces costs but also achieves the objective of treating waste with waste compared to utilizing commercial solid materials for synthesizing catalysts. By employing hydrochloric acid and sodium hydroxide pretreatment methods, the physicochemical properties of CFA are significantly improved, enhancing the dispersion of palladium (Pd) nanoparticles. The structural features of the prepared samples were characterized using various surface analysis techniques, and both intermittent and continuous modes were experimentally tested for the model catalytic reaction involving the sodium borohydride (NaBH4)-mediated reduction of p-NP. The results demonstrate that CFA has potential in wastewater treatment. [ABSTRACT FROM AUTHOR]

With the increasing output of coal fly ash (CFA) and garden waste, it is of great significance for environmental protection and resource utilization to establish if it can be recycled. The saline soil is widely distributed in the coastal areas of northern China, with high salt content and poor physical and chemical properties, which seriously affects the development of local agriculture and forestry and causes the waste of arable land. If CFA and garden waste compost (GWC) can be applied to saline soil improvement, it not only improves the local soil problem, but also helps environmental protection. Leaching salt is an important measure to reduce salt content in saline-alkali soil. The purpose of this study was to explore the effect of CFA and GWC on salt leaching of coastal saline-alkali soil through a soil column simulation test. The use of CFA and GWC promoted leaching and reduced leaching time. The addition of CFA and GWC to the soil suppressed the increase of HCO3- and CO32- during leaching, but increased the salt ion content of the soil after leaching. The addition of CFA to the soil reduced the ion retention of GWC in the soil, but the application of CFA and GWC had no significant effect on the leaching sequence of salt ions. CFA and GWC added to the soil improved the physicochemical properties and the quality of saline soils, but GWC was less effective than CFA in improving soil physicochemical properties. Application of CFA reduced the leaching time of soil salt ions by about 25%, as well as reduced the pH, EC, SAR, and total salt ion content of the soil by 2.18%, 20.83%, 56.63%, and 38.95%, respectively. [ABSTRACT FROM AUTHOR]

Fly ash carbonation is an effective method to achieve carbon reduction and stabilize the heavy metals. Supercritical CO2 can facilitate the carbonation process due to its strong diffusivity, but the effect of parameters on the stabilisation characteristics under supercritical conditions is unclear. In this paper, the heavy metal leaching characteristics of carbonized fly ash under supercritical CO2 conditions were comprehensively investigated. The experimental results showed that, increasing the pressure, applying mechanical force, increasing the rotational speed, raising the temperature, increasing the liquid-to-solid ratio, and adding calcium oxide all reduced the heavy metals leaching concentration. Compared with the original ash, Pb decreased by 38.65%, Cd by 31.66%, Hg by 47.06%, and As by 4.91% under supercritical conditions. After the fly ash carbonation, the influence of environmental factors such as the acid–base value, temperature, moisture, reaction time, and additives on the release characteristics were investigated. It was found that carbonized fly ash had good stability. At 30 °C, that leaching rate of Ni, Cr, Cd, Pb, Hg, and As after carbonation were 28.80%, 8.62%, 26.60%, 22.19%, 100.00% and 17.47%, respectively, lower than those of the original sample. The leaching rate of heavy metals increased with increasing temperature, and moisture aggravated the precipitation of heavy metals, which also increased with the reaction time. The addition of gypsum decreased the heavy metals leaching. The extraction experiments showed that after carbonation the heavy metals changed from active forms to stable residue states, except for Hg and As. Supercritical CO2 carbonation has a good effect on the stabilization of heavy metals. [ABSTRACT FROM AUTHOR]

The counter electrode in DSSCs must be made of a material with various advantageous chemical and physical characteristics to guarantee the cell's efficient functioning and cost efficiency. Coal fly ash is recognized for its substantial silicon dioxide (SiO2) content and other minerals and metals. This paper provides a detailed analysis and description of extracting and characterizing SiO2 from coal fly ash. This extraction aims to utilize SiO2 as a material for the counter electrode in DSSCs. The extraction procedure of SiO2 from coal fly ash involves a multi-step process that entailed the utilization of acid leaching using hydrochloric acid 1 M at 90°C for 4 h, which was subsequently followed by precipitation using NaOH 3 M at 90°C for 4 h to separate SiO2. The SiO2 gel was cleaned of contaminants with hot distilled water and dried at 110°C for 12 h. The SiO2 that was obtained was analyzed utilizing a range of analytical techniques to evaluate its structural, morphological, chemical, and optical properties. The X-ray diffractometer (XRD) examination revealed that the crystal structure of coal fly ash consisted of quartz, corundum, hematite, lime, and periclase. The SiO2 that was obtained exhibited a crystal structure that was both cubic and triclinic. The morphology is visualized using a scanning electron microscope (SEM). The study using atomic absorption spectroscopy revealed that the coal fly ash contained 52.91% SiO2, whereas the extracted SiO2 had a purity of 91.20%. The UV-Vis spectrophotometry investigation revealed that the SiO2 exhibited absorbance spectra with a wide band gap of 4.17 eV, whereas the coal fly ash had absorbance spectra of 3.37 eV. [ABSTRACT FROM AUTHOR]

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Coal fly ash (CFA) presents environmental challenges due to its abundance from coal combustion and difficult disposal issues, necessitating effective utilization strategies. This study explored the potential of combined microwave heating and silicon fusion as a pretreatment method for CFA, followed by zeolite molecular sieve synthesis. The aim is to enhance CFA activation, facilitate mullite transformation, and then extract valuable elements like silicon and aluminum. The synthesized zeolite molecular sieves exhibited a diamond-like structure with rich pore formations. XRD and XRF analysis identified that the predominant crystalline phases of the molecular sieves were Na6Al6Si10O32 (approximately 95.3%) with minor Na3.6Al3.6Si12.4O32, indicating NaP-type zeolites with a silicon-to-aluminum ratio of 1.78. In contrast, CFA's ratio was 1.24, suggesting that waste silicon powders served both as an activator and a supplementary silicon source. This innovative approach offered sustainable utilization of CFA, addressed environmental challenges, and promoted waste utilization. It exhibited tremendous potential in the environmental field with the advantages of low cost and environmental friendliness. [ABSTRACT FROM AUTHOR]

Using fly ash to synthesize zeolite molecular sieves can improve the reuse value of coal fly ash resources, reduce the synthesis cost of the zeolites, and protect the ecology. A novel approach was proposed to prepare zeolite socony mobil‐5 (ZSM‐5) zeolite via one‐pot hydrothermal synthesis. The mesoporous ZSM‐5 synthesized by adjusting the molar ratio of chemical reagents has higher crystallinity, larger specific surface area, and more adsorption sites. An analysis of methylene blue (MB) adsorption on mesoporous ZSM‐5 was conducted at many different adsorption parameters, including solution concentration, temperature, and duration of adsorption. The Langmuir model can objectively describe the adsorption behavior of MB on ZSM‐5, and the adsorption characteristics of MB on ZSM‐5 are better described by the pseudo‐second‐order kinetic model. The thermodynamic model provides the adsorption behavior as an endothermic reaction. [ABSTRACT FROM AUTHOR]

Lithium, a critical material for the global development of green energy sources, is anomalously enriched in some coal deposits and coal by-products to levels that may be considered economically viable. Recovering lithium from coal, particularly from coal gangue or coal ashes, offers a promising alternative for extracting this element. This process could potentially lead to economic gains and positive environmental impacts by more efficiently utilizing coal-based waste materials. This review focuses on lithium concentrations in coal and coal by-products, modes of lithium occurrence, methods used to identify lithium-enriched phases, and currently available hydrometallurgical recovery methods, correlated with pretreatment procedures that enable lithium release from inert aluminosilicate minerals. Leaching of raw coal appears inefficient, whereas coal gangue and fly ash are more feasible due to their simpler composition and higher lithium contents. Lithium extraction can achieve recovery rates of over 90%, but low lithium concentrations and high impurity levels in the leachates require advanced selective separation techniques. Bottom ash has not yet been evaluated for lithium recovery, despite its higher lithium content compared to feed coal. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Coal is used in most of the power and chemical plants to meet energy needs which produce various waste ashes. Reuse of these ashes as electroactive materials has great importance for sustainable development. In this study, it was detected that the main components of coal fly (CFA) and bottom ashes (CBA) were oxides of silica (SiO2), iron (Fe2O3), aluminium (Al2O3), and magnesium (MgO), besides carbon. These are well-known electrorheological (ER) active materials. The aim of this study is to reveal dielectric and electroactive vibration damping capabilities of CFA and CBA. According to the dielectric and ER flow tests carried out in insulating silicone oil (SO), the optimum concentration of particles was determined to be 35 wt.% for both ashes. Higher ER yield stress (τy = 135 Pa), higher ER efficiency (32.8), and better viscoelastic properties (τc = 128 Pa, G' = 680 kPa) under 3.0 kV mm-1 applied electric field were obtained for 35CFA/SO suspension system compared to 35CBA/SO (τy = 125 Pa, EReff = 24.0, τc = 55 Pa, G' = 260 kPa). Although it was concluded that both ashes can be upcycled to sustainable and smart vibration damping alternative materials, better performance was observed for CFA particles. [ABSTRACT FROM AUTHOR]

In this article, a novel method for SiC production from a residue of coal fly ash (CFA) after high-pressure leaching with a mixture of NH 4 HSO 4 + H 2 SO 4 is proposed. A thermodynamic analysis showed that SiC can be obtained at >1500 °C, and titanium carbide (TiC) and ferrosilicon (FeSi) can form as byproducts. Carbothermal reduction of the CFA residue with carbon in the range 1300–1500 °C with holding time 1–3 h was investigated. X-ray phase analysis (XRD) indicated that SiC forms at >1425 °C. Iron compounds in the form of Fe 3 Si and Fe 5 Si 3 were detected by Mössbauer spectroscopy in a sample sintered at 1500 °C. The possibility of SiC production by a two-step procedure was demonstrated. First, a SiC powder was obtained from the CFA residue and carbon at 1500 °C, then SiC was mixed with yttrium aluminum garnet Y 3 Al 5 O 12 and processed by spark plasma sintering at 1750–2000 °C, holding time 5 min, and pressure 50 MPa. Ceramic samples obtained at 1850 and 1900 °C with compressive strength of 350 ± 17.5 & 416 ± 20.8 MPa and Vickers hardness of 17.89 ± 0.89 & 15.97 ± 0.79 GPa, respectively, proved to be comparable to the best reported SiC + yttrium aluminum garnet ceramics. Thus, this study presents an original method for ceramics production from solid waste of coal-fired power plants; this approach will allow to create a comprehensive technology for utilizing 100 % of CFA. [ABSTRACT FROM AUTHOR]

Coal fly ash (CFA), a by-product of coal combustion, is a valuable raw material for various applications. However, the heterogeneous nature of the composition and properties of CFA provides challenges to its effective usage and utilisation. This study investigates the thermal behaviour of the fly ashes of lignite (FA1) and brown coal (FA2) and their fractions obtained by dry aerodynamic separation. Thermal analysis techniques, including thermogravimetry (TG), differential scanning calorimetry (DSC), and evolved gas analysis (EGA), were used to characterise the behaviour of the fly ash fractions while heating up to 1250 °C. The results reveal distinct differences in the thermal behaviour between ash types and among their different size fractions. For the FA1 ashes, the concentration of calcium-rich compounds and the level of recrystallisation at 950 °C increased with the decrease in particle size. The most abundant detected newly formed minerals were anhydrite, gehlenite, and anorthite, while coarser fractions were rich in quartz and mullite. For the FA2 ashes, the temperature of the onset of melting and agglomeration decreased with decreasing particle size and was already observed at 995 °C. Coarser fractions mostly remain unchanged, with a slight increase in quartz, mullite, and hematite content. Recrystallisation takes place in less extension compared to the FA1 ashes. The findings demonstrate that the aerodynamic separation of fly ashes into different size fractions can produce materials with varied thermal properties and reactivity, which can be used for specific applications. This study highlights the importance of thermal analysis in characterising fly ash properties and understanding their potential for utilisation in various applications involving thermal treatment or exposure to high-temperature conditions. Further research on advanced separation techniques and the in-depth characterisation of fly ash fractions is necessary to obtain materials with desired thermal properties and identify their most beneficial applications. [ABSTRACT FROM AUTHOR]

Melting is an efficient method to turn municipal solid waste incineration (MSWI) fly ash (FA) into non-hazardous material. Coal fly ash (CFA) was selected as the silica-alumina source to carry out co-melting research with MSWI FA in this work. The effects of the temperature and the CFA content on mineral transformation and the migration characteristics of heavy metals were analyzed. The results showed that the mixtures of MSWI FA and CFA reacted at high temperatures to mainly generate Ca2Al2SiO7, Ca2SiO4, and CaAl2Si2O8 primarily and then melted and formed the amorphous-phase vitreous body when the CFA content was more than 40% and the temperature was higher than 1300 °C. During the melting process, Cd and Pb were almost volatilized, while Cr, Mn, and Ni were almost retained. Besides, the volatilization rates of Cu and Zn fluctuated with the temperature and the CFA content. Suitable treatment temperature and CFA content were conducive to the transformation of the heavy metals in the FA into stable forms, and the melting products were no longer hazardous wastes because the vitreous body could effectively encapsulate heavy metals. This study aims to help reuse the FA and CFA collaboratively and be more environmentally friendly. [ABSTRACT FROM AUTHOR]

In this work, single-phase ZSM-5 zeolite was synthesized using solid waste coal fly ash (CFA) as raw material, providing a potential alternative for creating high-value-added products from this waste. X-ray diffraction (XRD), scanning electron microscopy, X-ray fluorescence, Fourier transform infrared spectroscopy, N2 physisorption, and other techniques were used to evaluate the crystallization and morphology of the ZSM-5 obtained. The results indicated that ZSM-5 can be synthesized by the simple method of mixing, stirring, and heating. A well-defined hexagonal shape of ZSM-5 with a specific surface area of 162 m2/g and mesoporous structure was obtained at the temperature of 160 °C during hydrothermal treatment for 72 h. Theoretically, the mechanism of crystal growth of ZSM-5, i.e. the liquid phase nucleation and step growth models, was clarified. These results open the possibility of exploring the crystallization of ZSM-5 and the utilization of CFA. Simultaneously, the critical roles of silicon in framework formation and crystallization control during the formation and growth of zeolites were elucidated. [ABSTRACT FROM AUTHOR]

Indian coal fly ash generally comprises 50–60% $Si{O_2}$ Si O 2 , and 25–35% $A{l_2}{O_3}$ A l 2 O 3 can potentially replace bauxite as an aluminum resource. Aluminum recovery from coal fly ash is highly dependent on removing amorphous silica, activating the inactive mullite phase, and increasing the $Al/Si$ Al / Si ratio. This work thoroughly investigated and compared the alkali-desilication operation by two widely used alkalis, $KOH$ KOH and $NaOH$ NaOH , based on four operational parameters: liquid-to-solid ratio, $KOH$ KOH or $NaOH$ NaOH concentration, leaching time and temperature. Using SEM, EDX, and XRD, the morphology and phase of fly ash and solid byproducts were analyzed. $NaOH$ NaOH was more effective than $KOH$ KOH in $Si{O_2}$ Si O 2 dissolution at all operational parameters. A 20 wt% concentration, 5:1 liquid-to-solid ratio, 2hrs leaching time, and 100°C temperature were the optimum removal conditions for silica from fly ash using $NaOH$ NaOH. With $KOH$ KOH , the ideal desilication conditions were obtained at 28 wt% concentration, 3hrs leaching time, and 150°C temperature. The highest $Al/Si$ Al / Si ratios were obtained under the same optimal desilication conditions. Using $KOH$ KOH and $NaOH$ NaOH , the $Al/Si$ Al / Si ratio was enhanced from 0.58 to 1.26 and 1.45, respectively. The main zeolitic products obtained were Hydroxysodalite in $NaOH$ NaOH -treated fly ash and Linde F zeolite and Kalsilite in $KOH$ KOH -treated fly ash. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Coal fly ash, an industrial solid waste product, and natural sand, a commonly available and inexpensive natural material, were used to fabricate ceramic membranes that are both affordable and sustainable. These ceramic membranes were fabricated by the uniaxial compaction technique using a manual hydraulic pressing machine. The effects of various fabrication parameters such as the sintering temperature and the amount of natural sand utilized, on the properties of the resulting ceramic membranes were extensively evaluated. X-ray fluorescence (XRF) analysis of the starting materials confirmed the presence of SiO2 and Al2O3, two key inorganic materials required for the fabrication of ceramic membranes. Heavy metals present in the raw coal fly ash were leached out prior to the fabrication process. The coal fly ash and natural sand were mixed in different proportions and the fabricated ceramic membranes were characterized using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), and Thermogravimetric analysis (TGA). The properties of the optimized membranes were further studied to ascertain their mechanical strength, chemical stability, porosity, water absorption, water permeability, and shrinkage behaviour. The membrane fabricated with 20 wt% sand content and at 1000 °C sintering temperature had pore size of 0.64 µm and 34.7 % porosity, exhibited good mechanical strength (7.71 MPa), and exceptional chemical stability. The membrane also showed a remarkable water permeability of 32.23 L/m2/h. This study showed that natural sand and coal fly ash can be efficiently employed to develop a multifunctional filtration membrane with adjustable properties that can be utilized in water purification.

Coal fly ash (CFA) is a predominant waste by-product of coal combustion which is disposed of in open ash dams that utilize large pieces of land. This waste material is classified as a hazardous substance in South Africa as well as in other countries due to its fine particles that are easily blown to the atmosphere and the unacceptable levels of heavy metals and persistent organic pollutants. Contaminants in CFA can pollute surface and ground water, agricultural sites, soil and therefore pose risks to the health of humans and the environment. More than 500 million tons of CFA is produced yearly and over 200 million tons remain unused globally. The production will continue due to high consumer energy demands, especially in countries with heavy reliance on coal for power generation. Despite a significant progress made on the application of phytoremediation approach for decontamination of polluted sites, there is very limited evidence for its potential in the rehabilitation of CFA dumps. Low organic carbon, microbial activities and availability of nutrients including nitrogen contribute to restricted plant growth in CFA, and therefore converting ash dumps to barren lands devoid of vegetation. Leguminous plant species can fix atmospheric nitrogen through symbiotic association with bacteria. Therefore, their intercropping mixture development can improve the chemistry of the substrate and facilitate nutrients availability to the companion plants. This approach can enhance the performance of phytoremediation and promote sustainable practices. The paper provides an overview of the ongoing burden of CFA disposal and discusses the ecological and economic benefits of using legumes, aromatic and bioenergy plants. We identify knowledge gaps to establishing vegetation in ash dumping sites, and provide insights to encourage continued research that will enhance the applicability of phytoremediation in restoration programs.

In this study, the production of an eco-friendly curcumin based nanocomposite fingerprint labeling powder is reported for the first time. This powder was prepared from thermal power plant waste known as coal fly ash. 3-aminopropyltrimethoxysilane (APTMS) was covalently interacted with coal fly ash (CFA/APTMS) and curcumin (CUR) was encapsulated onto CFA/APTMS to give a novel and eco-friendly CFA/APTMS/CUR nanocomposite for LFPs detection with the powder dusting method. Several instrumental techniques including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV–visible spectroscopy, fluorescence spectroscopy (FL), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), and transmission electron microscopy (TEM) were used to characterize this nanocomposite. The CFA/APTMS/CUR nanocomposite was applied as a forensic powder for the development of latent fingerprint (LFPs) images on various porous and non-porous substrates. Level 2 (island, origination, bifurcation, termination, fork, dot, and bridge) and Level 3 (sweat pores and shape of triangles, round, and irregular) were the features of the LFP images. Under visible light conditions, the aging LFPs images were clearly detected on an aluminum foil surface using the nanocomposite powder, which had good sensitivity and minimal background interference. Additionally, LFPs images were developed using CFA/APTMS/CUR nanocomposite on leather substrates for belts and shoes in order to confirm the benefits of the nanocomposite's high sensitivity. This nanocomposite improved LFPs images with unique patterns and showed excellent performance on a variety of surfaces for the development of LFPs. These findings therefore proved that the powdered CFA/APTMS/CUR nanocomposite can be effectively utilized for the development of LFPs images at important crime scenes and for the biometric identification of criminal suspects through fingerprint comparison.

Abstract CO2 mineralization plays a critical role in the storage and utilization of CO2. Coal fly ash (CFA) and red mud (RM) are widely utilized as CO2 mineralizers. However, the inert calcium species in CFA limit its carbonation capacity, meanwhile the substantial Ca2+ releasing of RM is hindered by a covering layer of calcium carbonate. In this study, CO2 mineralization in a composite system of CFA and RM was investigated to enhance the carbonation capacity. Multiple analyzers were employed to characterize the raw materials and resulting mineralization products. The results demonstrated that a synergistic effect existed in the composite system of CFA and RM, resulting in improving CO2 mineralization rate and efficiency. The produced calcium carbonate was ectopically attached the surface of CFA in the composite system, thus slowing down its coverage on the surface of RM. This phenomenon facilitated further releasing Ca2+ from the internal RM, thereby enhancing CO2 mineralization efficiency. Meanwhile, the inclusion of RM significantly improved the alkalinity of the composite system, which not only promoted the dissolution of Ca2+ of the inert CaSO4(H2O)2 in CFA, but also accelerated CO2 mineralization rate. The investigation would be beneficial to CO2 mineralization using industrial solid wastes.

Abstract Background Hundreds of millions of tons coal fly ash are produced annually to support economic development and industrial production. However, directly applying coal fly ash to agricultural production can decrease the land productivity and pose a threat to the ecosystem due to the poor physicochemical properties and seriously heavy metal pollution. Methods In this study, a field experiment to investigate the effects of coal fly ash as a soil amendment was conducted in Hebei province, China. The coal fly ash (CFA) soil field was mixed with the carrier soil (CS, without containing coal fly ash) at different rates (0–40% mass content) in the 0–20 cm layer of top soil and then mixed with a rotovator. The soil was then amended with 0.45–1.80 kg·m− 2 of G1 soil amendment for planting corn. Purpose The purpose of this study is to investigate the response mechanism of soil microbial community activities, and soil physicochemical properties to soil amendment and carrier soil in coal fly ash soil. Key results The study found that the G1 amendment, which consisted of humic acid, polyacrylamide, zeolite powder, and FeSO4·7H2O, improved the soil chemical properties and physical structure by increasing soil bulk density and macroaggregates. The highest corn yield was observed in B5 (20% CS and 1.3500 kg·m− 2 G1). Meanwhile, the abundance of microorganisms that facilitate the circulation of soil nutrients such as Acidobacteria (77.05%), Sphingomonas (25.60%), Nitrospira (20.78%), Streptomyces (11.32%), and Gaiella (10.20%) was increased. Conclusions Overall, our results indicate that the use of coal fly ash soil as a amendment can enhance soil sustainability by improving soil microbial functions. These findings provide a reference for the development and application of coal fly ash soil amendments.

The feasibility of preparing non-sintered lightweight aggregate using textile sludge and coal fly ash as the main raw materials was investigated. Extensive experiments were conducted to analyze the effects of different coal fly ash/sludge ratio, sodium silicate addition and curing time on the performance of non-sintered lightweight aggregates (NSLWAs). The optimal preparation parameters were determined as follows: coal fly ash/cement ratio of 2.2, textile sludge addition of 20%, sodium silicate addition of 10%, and curing time of 28 days. Under these optimal preparation conditions, the cylindrical compressive strength of NSLWAs was relatively high. The test results of Zn leaching toxicity test and S content all met the relevant standards and environmental safety requirements. NSLWA has a dense internal structure with uniformly distributed grains. By analyzing the hydration reaction mechanism during the NSLWAs preparation, it can be obtained that part of Zn2+ was stabilized by conversion into insoluble Ca(Zn(OH)3)2.2H2O, while the remaining part was solidified and stabilized through encapsulation and adsorption of hydration products. Furthermore, it was discovered that pozzolanic admixtures played a crucial role in the hydration and hardening process of NSLWAs, and the presence of C-S-H gel and Mullite contributed to the increase in cylinder compressive strength of NSLWAs. [ABSTRACT FROM AUTHOR]

Coal fly ash (FA), an aluminum silicate by-product and environmental pollutant which is generated during the combustion of coal in coal-fired power stations, was used as an electrode modifier for the determination of Cd(II) in aqueous solutions. In this work, graphite/polyurethane-based composites containing different amounts of FA were prepared and characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) thermogravimetry (TGA), and derivative thermogravimetry (DTG). The graphite/polyurethane composite electrodes (GPUE), with and without FA modifier, were evaluated with regard to their performance as voltammetric electrodes in the determination of metallic cations, using Cd(II) as a probe. After optimizing solution and instrumental parameters affecting the peak current, a differential pulse anode stripping voltammetry (DPASV) procedure was developed for GPUE modified with 5% FA (m/m), resulting in a linear response for Cd(II) from 2.0 x 10−7 to 1.0 x 10−6 mol L−1 with a detection limit (LOD) of 6.6 x 10−8 mol L−1. Cd(II) was added to natural water samples and determined at the 10−7 mol L−1 level with a mean recovery of 99%. It was also extracted from exhausted rechargeable Ni-Cd batteries and diluted to ca. 0.2 µmol L−1 and determined with the same electrode, with recoveries of 98.7% when compared to FAAS. These results serve as a proof of concept that FA is a useful electrode modifier. [ABSTRACT FROM AUTHOR]

CO2 mineralization plays a critical role in the storage and utilization of CO2. Coal fly ash (CFA) and red mud (RM) are widely utilized as CO2 mineralizers. However, the inert calcium species in CFA limit its carbonation capacity, meanwhile the substantial Ca2+ releasing of RM is hindered by a covering layer of calcium carbonate. In this study, CO2 mineralization in a composite system of CFA and RM was investigated to enhance the carbonation capacity. Multiple analyzers were employed to characterize the raw materials and resulting mineralization products. The results demonstrated that a synergistic effect existed in the composite system of CFA and RM, resulting in improving CO2 mineralization rate and efficiency. The produced calcium carbonate was ectopically attached the surface of CFA in the composite system, thus slowing down its coverage on the surface of RM. This phenomenon facilitated further releasing Ca2+ from the internal RM, thereby enhancing CO2 mineralization efficiency. Meanwhile, the inclusion of RM significantly improved the alkalinity of the composite system, which not only promoted the dissolution of Ca2+ of the inert CaSO4(H2O)2 in CFA, but also accelerated CO2 mineralization rate. The investigation would be beneficial to CO2 mineralization using industrial solid wastes. [ABSTRACT FROM AUTHOR]

Diopside-Like based ceramics as the main crystalline phase (expressed as 'Diopside') were prepared via one-step sintering using extracted titanium slag (ETS) and coal fly ash (CFA) as raw materials. The effects of CFA content and sintering temperature on the crystal phase composition, microstructure, properties and crystallization kinetics were studied by X-ray fluorescence, X-ray diffraction, scanning electron microscopy, and inductively coupled plasma emission spectrometry. According to the findings, the addition of CFA supplemented the deficiency of Si and Al in ETS and balanced the Ca/Al/Si molar ratio in the system. Moreover, at the CFA doping of 20 %, melilite was gradually transformed into 'diopside' at 800–1100 °C that further remained stable at 1160–1200 °C. 'Despite' the fact that the crystallization activation energy increased and the Avrami index was at its lowest level (1.75), the crystallization temperature was reduced, whereas the crystallization rate increased, causing the ceramic body and surface to crystallize and thereby improving the properties of ceramics. Sintering at 1180 °C for 1 h resulted in ceramics with 'diopside' as the primary crystal phase composition. The water absorption, linear shrinkage, bulk density, bending strength, and acid resistance were respectively 1.3 %, 13 %, 2.89 g cm−3, 141.8 MPa, and 97.36 %. Finally, 'diopside' possessed the higher acid resistance than melilite and anorthite. [ABSTRACT FROM AUTHOR]