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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]

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Water pollution has become one of the most acute environmental problems. One of the pollutants coming to water bodies from industries are dyes, which are harmful to human health, living organisms, and the esthetic appearance of water. Most dyes are toxic, carcinogenic, rarely biodegradable, and highly soluble in water. Therefore, industrial wastewater treatment has become important. Adsorption technique of removal of dyes from water is simple, efficient, and inexpensive as compared to other techniques. Adsorption efficiency depends on the type and surface area of adsorbents. Iron-rich coal fly ash (IRCFA)–Polydopamine (PDA)@ Silver (Ag) nanocomposite was prepared by separating the iron-rich part (IRCFA) from coal fly ash and coated with polydopamine. IRCFA was mixed with 10 mM tris buffer solution containing 1 g dopamine. The prepared IRCFA-PDA was added to an aqueous solution of silver nitrate, heated at 60 °C, and then 30 mL of flower waste extract was added to this solution. Solid IRCFA-PDA@Ag was obtained, and the prepared nanocomposite was used for the removal of methylene blue (MB) dye from water. The nanocomposite used was prepared by a cost-effective method and has high reusability, separability, and fast regeneration ability. The mechanism of removal of MB dye has been discussed in detail. [ABSTRACT FROM AUTHOR]

Calcium looping (CaL) process relying on CaO as high-temperature CO 2 sorbents is a prospective alternative technology for simultaneously cyclic CO 2 capture and thermochemical energy storage. However, the cyclic stability and the energy storage density of the CaO-based sorbents decay drastically over repeated carbonation-calcination cycles. Herein, we yielded CaO-based sorbents derived from all industrial solid wastes with carbide slag (CS) as precursor and coal fly ash (CFA) as stabilizer featuring superior carbonation characteristics, stable CO 2 cyclic uptake and high thermochemical energy storage density over multiple operation cycles. The optimal sorbent (CCS–H-G-CFA-D) exhibited a high initial CO 2 uptake of 0.38 g CO2 /g sorbent , superior cyclic stability with an average decay rate of 1.05% per cycle and remarkably stable energy storage density of 1375 kJ/kg, retaining 89.5% after 10 repeated cycles. Thereby, the simultaneously enhanced cyclic CO 2 capture and thermochemical energy storage are attributed to adding CFA stabilizers in CS-derived CaO-based sorbents, forming stable skeleton to alleviate sintering, improving the uniform mixing degree between sorbent particles and promoting the carbonation reaction via synergistic effect. This simple and eco-friendly approach of cost-effective sorbents totally derived from industrial solid wastes provides a new avenue for large-scale practical CO 2 capture and energy storage processes. Coal fly ash (CFA)-stabilized carbide slag-derived CaO-based sorbents feature superior carbonation characteristics, stable CO 2 cyclic uptake and high thermochemical energy storage density over multiple reversible operation cycles. [Display omitted] • A process coupled calcium looping and thermochemical energy storage is proposed. • Facile cost-effective strategy to synthesize all-solid-waste-derived CaO-based sorbent. • Modified carbide slag with coal fly ash is employed in coupled process. • The optimal sorbent retains 89.5% initial capacity with stable energy storage density. • New-formed solid solutions and uniform doping enhance stability by isolating CaO grains. [ABSTRACT FROM AUTHOR]

High value-added NaHS zeolite was prepared using the microwave-assisted alkali fusion hydrothermal method from industrial solid waste coal fly ash as raw material without adding silicon and aluminum sources. The effect of mass ratio of alkali to coal fly ash, crystallization temperature, and crystallization time on the preparation of NaHS zeolite was investigated. The NaHS zeolite was characterized using XRD, SEM, BET, and FT-IR. The experimental results showed that the NaHS zeolite with complete crystal structure could be synthesized at m(sodium hydroxide):m(coal fly ash) = 2:1, crystallization temperature of 140°C, and crystallization time of 48 h. The prepared HS zeolite had high purity, complete crystal structure, and uniform grain size (2 μm). The NaHS zeolite was beneficial for CO2 adsorption properties with 110.9 cm3/g at 25°C. [ABSTRACT FROM AUTHOR]

Coal fly ash (CFA), an industrial by-product of high-temperature combustion of coal in coal-fired power plants, is one of the most complex and largest amounts of industrial solid wastes generated in China. It is widely recognized that CFA should be considered as a potential alumina resource to substitute bauxite. In this review, the features of high-alumina fly ash and aluminum recovery technologies are first described. Later, the merits and drawbacks of alumina extraction technologies in recovering more valuable materials are compared in terms of extraction mechanisms and equipment requirements. It is shown that "predesilicating-sodium carbonate (Na2CO3) activation-acid leaching" is currently a promising method in achieving multimetal synergistic extraction. Finally, the hydrochloric acid and sulfuric acid combination process is proposed as a sustainable development of the predesilicating-Na2CO3 activation-acid leaching process. The findings of this review provide theoretical guidance for novel developments and applications of aluminum extraction technologies. [ABSTRACT FROM AUTHOR]

Coal fly ash (CFA) as an industrial solid waste has an extremely adverse influence on the environment. The high value utilization of CFA was a hot research topic with sustainable development for years. In this work, we found that CFA exhibits underoil superhydrophobicity and underwater superoleophobicity due to the special microstructures and chemical composition. And for the first time, CFA was used as a filter material for the separation of various oil/water mixtures and emulsions under the driven of gravity without any further chemical modification. Both light oil/water and heavy oil/water immiscible mixtures can be completely separated through CFA with almost 99.9% efficiency. More importantly, due to the "size-sieving" effect, CFA was capable of purifying various emulsions with high separation efficiency. After being pre-wetted with water, CFA displayed excellent separation capacity more than 92% and good flux as fast as 1050 L m−2 h−1 for water-in-oil emulsions. After being pre-wetted with oil, CFA exhibited a higher separation efficiency of 99.5% and a flux of over 935 L m−2 h−1 for water-in-oil emulsions. Therefore, this work provided an innovative, green, and low-cost approach for various oil/water mixtures and emulsions separation, which can also be widely used in wastewater treatment. Image, graphical abstract • CFA shows underwater superoleophobicity and underoil superhydrophobicity. • CFA was used for various emulsions separation without extra chemical treatment. • High efficiency of oil-in-water and water-in-oil emulsions separation was achieved. • The research presented an innovative approach for oil/water emulsion separation. [ABSTRACT FROM AUTHOR]

Coal fly ash is industrial waste produced by coal power plants, containing large amounts of magnetospheres (MSs), where Fe 3 O 4 is abundant and magnetite is the major composition. However, the functional reuses of MSs are always restricted by the impurities of aluminosilicate and other forms of iron oxide including maghemite, magnesioferrite, as well as hematite. In this paper, a chemical vapor deposition (CVD) process was proposed to convert MSs into a magnetic core@ carbon shell structure, which would found its application in microwave adsorption field. The prepared samples were characterized by using SEM, HRTEM, EDX, BET, XRD, Raman spectroscopy and TGA analysis. Results showed that MSs burst during the CVD process and transformed into a loose agglomeration of submicron-sized particles with a typical core@ shell structure. Crucially, instead of single sphere of MSs, the ultrafine grains of ferrospinel within MSs served as the core. The mechanism of carbon deposition of graphite shells and phase transformation of ferrospinel cores during the CVD process were revealed. Magnetism and microwave adsorption properties were tested, and the structural dependence relationship between these properties and the core@ shell structure was clearly identified. For a sample time of 60 min, the minimum absorption peak was observed as −32.4 dB at 12 GHz, with the minimum frequency bandwidth below −10 dB at 4.3 GHz. We propose a low-cost, one-step preparation of cementite core@ graphite shell composites with high-performing microwave adsorption. Our method provides an alternative option for the practical reuse of the industrial waste. [ABSTRACT FROM AUTHOR]

Coal fly ash is an industrial waste generated from the thermal power plant and a large amount of it could be produced annually in the world, which can cause serious environmental problems. Reutilization of coal fly ash could be imperative to alleviate the environmental pressure. Thus, in the present study, coal fly ash was used as silicon source for the synthesis of calcium silicate hydrates (C-S-Hs) though the desilication process. Two kinds of C-S-Hs was synthetized at 100°C and room temperature respectively, with the fixed Ca/Si molar ratio of 1.2, and adopted as the adsorbents for phosphate. The properties of them were characterized using XRD, SEM, FTIR, TG-DTA as well as surface area and pore analysis. Compared to C-S-H synthesized from high temperature, the C-S-H obtained at room temperature possessed high purity and larger surface area. Therefore, synthesis by agitation at room temperature could be an alternative method to produce C-S-H materials from desilication liquid of coal fly ash, and this could save infrastructure cost and energy consumption. Both C-S-H materials have good ability to immobilize phosphate pollutant (higher than 100 mg·g-1). The specific mechanisms of phosphate removal using C-S-H include several steps: firstly, phosphate ion was immobilized by binding with Ca2+and forming aggregates, and the C-S-H structures were gradually corroded. Eventually, hydroxyapatite was formed after the C-S-H structure was totally destroyed. [ABSTRACT FROM AUTHOR]

• Resource utilization of industrial wastes in energy storage system. • Synergistic adsorption-electrocatalysis effectively suppresses the shuttle effect. • MCFA separator can effectively reduce internal resistance and polarization of LSBs. • MCFA helps to improve the transformation kinetics of LiPSs. The notorious shuttle effect severely limits the practical application of Lithium-Sulfur Batteries (LSBs). In line with the concept of "green chemistry", industrial solid waste is reasonably applied to the design of battery's interlayer. The modified coal fly ash (MCFA) can effectively accelerate the redox kinetics of the electrode and optimize the nucleation and decomposition of Li 2 S. The synergistic adsorption and catalytic action from rich pore structure and polar metal oxides can effectively capture and fix free polysulfide (LiPSs), which realizes the inhibition of shuttle effect. The LSBs with MCFA interlayer exhibit good cycle stability (decay-rate: 0.05% per cycle) and rate capability (703 mAh g−1 at 3C). Even under extreme conditions of poor electrolytes (E/S = 7.8 μL /mg), Cell-MCFA/PE with a high S loading (7.5 mg cm−2) still performs well (732 mAh g−1 after 100 cycles). This work provides an economical and environment-friendly strategy for the design of interlayer, which is conducive to the commercialization process of LSBs. [ABSTRACT FROM AUTHOR]

In this work, coal fly ash (CFA) was first converted to fly ash-derived zeolite (FAZ), then CuO particles were prepared and loaded onto FAZ to build a heterogeneous Fenton catalyst (CuO-FAZ) for bisphenol a (BPA) removal. The characterization results demonstrated that CFA was changed into a mesoporous structure with a higher specific surface area after FAZ conversion, and CuO showed granularity and was well distributed on the surface of FAZ. Under optimal experimental conditions ([BPA] = 50 mg/L, [catalyst] = 1.0 g/L, [H 2 O 2 ] = 140 mM, and temperature = 25 °C), over 85% of BPA was degraded within 60 min. After five consecutive cycles, BPA removal remained more than 70%, indicating that CuO-FAZ had excellent catalytic capability as well as superior stability. Furthermore, compared to other reactive radicals generated in the process, O H ∙ (s u r) radicals were found to play a major role in the removal, with a contribution of nearly 50%. A ligand complex could develop between CuO-FAZ and BPA, thereby enhancing the O H ∙ (s u r) radicals generation. Results further showed that CuO-FAZ can be employed to effectively and economically treat actual industrial wastewater containing phenolic compounds. This work introduces a method of preparing coal fly ash-based heterogeneous Fenton catalyst, which provides a novel idea for high-value coal fly ash reuse. • A coal fly ash-based heterogeneous Fenton catalyst (CuO-FAZ) was prepared. • CuO-FAZ exhibited excellent catalytic activity and stability. • The possible BPA removal mechanism was discussed. • This is cost-effective with potential industrial applications. [ABSTRACT FROM AUTHOR]

• Physico-chemical properties of CFA were summarised in detail. • Leachability of CFA was analysed using six aspects. • Adverse effects of CFA on humans, wild animals, and plants were reviewed. • Utilisation of CFA in the USA and EU were summarised. • Directions for the reuse of CFA in the near future were proposed. Coal fly ash (CFA) is a valuable industrial solid waste, but conventional methods used for its disposal can lead to serious and long-lasting environmental issues. The study of technologies for CFA recycling has been of major concern, while the harm caused by CFA is only partially understood, limiting its reuse. In this review, the basic physico-chemical properties of CFA are introduced, followed by a systematic summary and discussion of the leachability of CFA via different leaching methods and the chemical speciation of some typical metal elements in CFA, which is related to its harmful effects. The specific harm that CFA causes to humans, wild animals, and plants and the study status of magnetic property of CFA are presented. Because of the pervasive concerns of many people, the utilisation of CFA in the USA and Europe and an economic and environmental analysis of its disposal is provided and discussed. Finally, some possible directions for future research involving CFA are proposed. [ABSTRACT FROM AUTHOR]

Fly ash is a coal combustion by-product with low pozzolanic reactivity which limits its resource utilization and engineering properties in building materials. The present study investigates a wet-milling treatment to activate the coal fly ash and promote its sustainable utilization. It was found that wet-milling is a suitable, efficient and eco-friendly technology for solid waste refinement. The pozzolanic reactivity is greatly improved after wet-milling treatment, as high as 140% at 60 days with particle size of 2.51 μm. It was observed that ettringite formation has occurred during the wet-milling. Physical structure, chemical evolution and ion leaching behavior during the wet-milling were discussed. It was proved that activation mechanism of wet-milling is a combined effect of physical breakage and ion dissolution acceleration. Binding energy was found decreased and SiQn structural units were found less polymerized which are helpful for the depolymerization during the pozzolanic reaction. Furthermore, technical applicability of wet-milling for various industrial solid wastes was also investigated. Image 102651 • Wet-milling is a suitable, efficient and eco-friendly technology for solid waste refinement. • Pozzolanic reactivity of coal fly ash is greatly improved after wet-milling treatment. • The activation mechanism of wet-milling technique for solid wastes was addressed. • Technical advantages and applicability of wet-milling for various solid wastes were discussed. [ABSTRACT FROM AUTHOR]