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Herein, a simple, versatile, and low‐cost approach has been proposed to realize the green utilization of secondary aluminum dross, the hazardous solid waste, namely directly sintering dry‐pressed green bodies from secondary aluminum dross to fabricate porous ceramics according to high‐temperature foaming process spontaneously without adding spare foaming agents. Aluminum nitride (AlN) in secondary aluminum dross was employed to realize high‐temperature foaming due to its oxidation, which makes traditional AlN and salts removal process needless. Moreover, near‐zero shrinkage or even expansion during sintering of porous ceramics have occurred because in‐situ foaming process together with the oxidation of Al particles well offset the sintering shrinkage. After sintering at 1400°C for 2 h, porous ceramics composed of α‐Al2O3 and spinel phases with open porosity of 37.91%, sintering expansion rate of 1.13%, flexural strength of 45.67 MPa, and thermal conductivity of 0.97 W/(m·K) have been prepared. Cenospheres as pore‐forming agents have been added to further improve the porosity, and alumina‐based porous ceramics with open porosity of 28.39%–43.20% and flexural strength of 15.80–52.48 MPa have been obtained. This effective solution for recycling secondary aluminum dross could supply high‐performance porous ceramics, which is expected to be applied in the fields of light‐weight structural components and thermal insulations. [ABSTRACT FROM AUTHOR]

• Highly porous ceramics were fabricated by particle-stabilized foams method. • Slags from smelting of spent automotive catalysts have been utilized. • Sintering temperature and dosage of slag determined the properties of porous ceramics. • The obtained porous ceramics show excellent physical properties. Spent automotive catalysts are the most crucial secondary resources of platinum group metals (PGMs). Currently, the iron-capturing method is one of the most promising technologies for PGMs recycling. The residual smelting slags contain large amounts of CaO, Al 2 O 3 , MgO, SiO 2 , Na 2 O, and the trace of heavy metals (e.g. Cr, Pb, Ni), which are classified as solid waste or even hazardous waste, which are typically treated by landfills, and poses severe threats to the environment. In this paper, based on the specific chemical composition of smelting slags, ceramic foams with high porosity, low density and good thermal insulation were fabricated by particle-stabilized foams method, where long-chain surfactant hexadecyltrimethylammonium chloride served as the hydrophobic modifier of slag particles and colloidal silica as binding agent. Herein, the influence of sintering temperature and the amount of smelting slag on the physical properties of obtained porous ceramics were systematically investigated. The results showed that porous ceramics with a bulk density of 0.40–0.64 g/cm3, open porosity of 74.7–83.4%, thermal conductivity of 0.10–0.21 W/(m∙K) and compressive strength of 1.04–4.01 MPa can be obtained with the mass ratio of slag: colloidal silica of 2:1, 3:1 and 4:1 sintered at 1000°C for 2 h. The porous ceramics with these unique properties are promising to be applied as thermal insulation materials. This convenient, facile and versatile approach is also expected to fabricate porous ceramics by using other solid waste as raw materials. [ABSTRACT FROM AUTHOR]

To prepare bio-scaffolds with multi-stage pores, excellent mechanical and biological properties to meet the requirements of personalized bone repair, digital light processing using Pickering emulsion as paste has been proposed here firstly for porous hydroxyapatite scaffolds with complex shape and fine microstructure. It is found that dispersant content, solid loading and oil to water ratio of Pickering emulsions play vital roles on the controlling of pore morphology and pore size distribution of final hydroxyapatite ceramic foams. The multi-stage pores consist of millimeter-scale pores designed by 3D models and micro-pores below 10 µm derived from emulsion droplets. Due to the integration of hierarchical pores at different scale levels and micropores, hydroxyapatite ceramic foams possess outstanding compressive strength of 4.46–8.03 MPa at porosity of 76.59-72.96%. In vitro cell experiments illustrate that rat bone mesenchymal stem cells can spread and adhere to bio-scaffolds, promoting cell proliferation effectively and further verifying their good biocompatibility. [ABSTRACT FROM AUTHOR]

Particle-stabilized foams employing dual-phase sol of boehmite in combination with silica to prepare mullite ceramic foams has been proposed for the first time. The obtained mullite ceramic foams possess hierarchical pores, that is micropores derived from the air bubble templates and open windows formed by grain growth at thin area of pore wall according to the mullitization reaction. Furthermore, nanoparticles favor the improvement of specific surface area of ceramic foams, and wrinkles caused by drying shrinkage would retain when sintering at low temperature of 900℃-1100℃, leading to high specific surface area of 94.4-219.2 m2/g. The achieved mullite ceramic foams present relatively high compressive strength of 6.6−40.4 MPa at a high open porosity of 64.0 %–87.0 %, and their thermal conductivity could reach as low as 0.10 W/(m·K), which would make them promising lightweight materials applied in broad fields including thermal insulations, filters, bio-scaffolds, catalyst supports and the like. [ABSTRACT FROM AUTHOR]

[Display omitted] • Over 6.5 million tons of SAD is discharged on the planet annually. • Recycling SAD to make building materials is reviewed. • Recycling SAD to make ceramics possesses a better carbon reduction. • SAD can be made into metal/alumina ceramics with low carbon emission. Secondary aluminum dross (SAD) is consisted of alumina, aluminum nitride (AlN), salts and heavy metal oxides. Over 6.5 million tons of SAD is discharged in the world annually. Currently, recycling SAD to make building materials is a promising way of waste recovery. Building materials made from SAD can be divided into structure materials and insulation materials. Structure materials inherits the high strength, fire resistance and chemical stability of alumina in SAD. The products include cement, bricks, ceramics and glass ceramics. Insulation materials are manufactured by utilizing reactivity of AlN in SAD. AlN can hydrolyze or be oxidized to release gas. Insulation materials include porous bricks, porous ceramics and porous glass ceramics. Environmental and economic benefits analysis was conducted on structure materials and insulation materials made from SAD. Ceramics and porous ceramics were taken as evaluation objects. Manufacturing a ton of ceramics and porous ceramics from SAD attained profits of 370.2 and 388.2 dollars, and reduced carbon emissions of 746.2 and 261.5 kg. Therefore, recycling SAD to make ceramics possessed a better carbon reduction. In order to further reduce carbon emission and utilize AlN in SAD, we proposed a novel idea of manufacturing metal/alumina composite ceramics from SAD and metallurgical solid waste. AlN in SAD reduced the metal oxides into alloy, which can strengthen the alumina ceramics. We should clarify the thermodynamics and kinetics of AlN reducing metal oxides and strengthening mechanisms of metal/alumina composite ceramics. [ABSTRACT FROM AUTHOR]

[Display omitted] • High addition SAD is fully recycled and transformed into glass–ceramic foams. • Glass-ceramic foams exhibited excellent compressive strength and high porosity. • The application of glass–ceramic foams in adsorbent was verified. • The pore-forming mechanism is explained during thermal treatment. Porous ceramics with hierarchical pore and high strength were prepared by secondary aluminum dross and quicklime as main raw materials. The influence of quicklime content and thermal treatment on the porosity, pore morphology, compressive strength and bulk density of porous ceramics has been investigated. Scanning electron microscopy, computed tomography, x-ray diffraction and thermal analysis were used to characterize the microstructure, phase transition and high-temperature reaction of the samples. The formation temperature of the liquid phase in the micro-region starts at around 973 °C, close to the temperature at which the mixture starts to produce the liquid phase as calculated by FactSage7.1 software. The achieved porous ceramics exhibited excellent compressive strength of 12.4–51.0 MPa at a relatively high porosity of 63.7%-79.6%. Furthermore, the potential application of the obtained porous ceramics as adsorbent was verified by the adsorption of malachite green solution. Due to the high connectivity of the pores and the presence of a large number of thin lamellar crystalline phases, the adsorption rate of the sample to malachite green solution can be as high as 98.4%. [ABSTRACT FROM AUTHOR]

As a hazardous waste, municipal solid waste incineration (MSWI) fly ash poses a serious threat to the environment, and considerable efforts have been made to achieve its harmless treatment. Herein, a novel approach for handling MSWI fly ash has been proposed to prepare porous glass–ceramics by alkali activation–crystallization, which overcomes the difficulty of controlling air bubbles under high temperatures. MSWI bottom ash rich in Al 2 O 3 and SiO 2 are co-treating as raw material to develop glass framework structure. The alkali activation mechanism shows that the development of MSWI ashes based basic glass from monomer to silica–aluminate gel under alkaline condition. The influence of H 2 O 2 addition on the morphology and physical properties of porous glass–ceramics were evaluated. Porous glass–ceramics with uniform hierarchical pore structure have been fabricated at 3 mol/L NaOH, a solid loading of 55 wt%, and 1–4 wt.% H 2 O 2 , then crystallization treatment at 1150 °C for 2 h, the porosity and the bulk density of which varies from 77.22 to 82.94% and 0.68–0.91 g/cm3 respectively, while their relatively high compressive strength ranges from 1.62 MPa to 3.85 MPa. Attributed to the hierarchical porous structure, uniform distribution of pores and excellent physical properties, porous glass–ceramics has potential applications in construction, filtration, and adsorption materials, providing a convenient and feasible method for the efficient and comprehensive utilization of MSWI ashes. [Display omitted] • A novel method for developing hierarchically porous glass ceramics is proposed. • The alkali-activation mechanism of basic glass prepared by MSWI ashes has been studied. • Hydration products can promote the formation of sub-micron pore. • The porous glass-ceramics has excellent properties and environmentally acceptable. [ABSTRACT FROM AUTHOR]