Search Results (39)

To evaluate the stability of fiber-reinforced cemented foamed backfill (FCFB) in complex underground mining environments, this study investigates the synergistic effects of fiber content and modified coal gangue (MCG) under acidic and high-temperature conditions. Through a systematic analysis of hydration processes, compressive strength, and deformation characteristics, the research identifies critical mechanisms for optimizing backfill performance. Calcination of MCG at 700 °C enhances gelling activity via amorphous phase formation, while modified aluminum dross (MAD) treated at 950 °C develops dense α-Al₂O₃ and spinel phases, significantly improving chemical stability. In acidic environments, the suppression of calcium silicate hydrate (C-S-H) is offset by the development of Al³⁺-driven C-A-S-H gels. These gels adopt a tobermorite-like structure, substantially increasing acid resistance. Mechanical testing reveals that while 1% fiber reinforcement promotes nucleation and densification, a 2% concentration hinders hydration. Compressive strength at 28 days shows constrained growth due to pore inhibition, and failure modes transition from multi-crack parallel failure (3-day) to single-crack tensile-shear failure. Under acidic conditions, strain concentration in the upper sample highlights a competitive mechanism between Al³⁺ migration and fiber anchorage. Ultimately, the coordinated regulation of MCG/MAD and fiber content provides a robust solution for roof support in challenging thermo-chemical mining environments. Full article

The amount of secondary aluminium dross in China exceeds one million tons annually, posing environmental and disposal challenges. This study explores acid leaching as an alternative to conventional alkali methods for recovering Al from secondary aluminium dross to produce Al₂O₃. Research has focused on optimizing leaching conditions. Under optimized H₂SO₄ leaching conditions, an Al³⁺ leaching ratio of 86.5% is achieved. By maintaining a pH below 9 during hydrolytic precipitation and multiple washes, the leaching efficiency of Al from Al(OH)₃ reached 95.97%. The original dross, which is primarily composed of Al, Al₂O₃, and AlN, undergoes a transformation where AlN becomes Al(OH)₃ during washing. Thermal decomposition then yields Al₂O₃. The overall recovery of Al reaches 83.11%. Full article

Aluminum is one of the most in-demand nonferrous metals in the world. The secondary aluminum dross (SAD) produced during aluminum smelting is a type of solid waste that urgently requires disposal. SAD, municipal solid waste incineration fly ash, and bottom slag were used as raw materials to prepare porous ceramsite in a laboratory in this study. Multi-factor design experiments were then used to explore the influence of the sintering condition on the compressive strength to provide a basis for ceramsite preparation using SAD. The results showed that, within a certain variation range, the levels of each factor showed overall positive correlations with the ceramsite compressive strength. The contributions of the ceramsite particle size, the silicon–aluminum ratio (Si/Al), the sintering temperature, and the sintering time to the compressive strength of the porous ceramsite then decreased. The factors had a synergistic effect. The interactive effect of multiple factors on the porous ceramsite compressive strength rose with an increase in the particle size and Si/Al ratio. The average compressive strength of the porous ceramsite prepared in this study was 4.06 ± 3.71 MPa, and the maximum compressive strength was 14.13 MPa. The highest ceramsite compressive strength was achieved under a sintering temperature of 1270 °C, a particle size of 2 cm, a sintering time of 30 min, and a silicon–aluminum ratio of 1.5. In addition, there was a reaction relationship between the multiple factors involved in the sintering of the SAD-based porous ceramsite. Pilot or industrial tests should be conducted in the future based on these experiments and the intended ceramsite use. Full article

This study investigates the synthesis of magnesia–hercynite-based refractories using blends of magnesia powder, aluminum dross (AD), mill scale (MS), and graphite, focusing on the effects of carbon concentration and heating temperature. The results demonstrate successful synthesis at 1550 °C and 1650 °C, with high magnesia content (C80 and D80) leading to the formation of distinct phases, including MgO, FeAl₂O₄, MgFeAlO₄, CaMg(SiO₄), and Ca₃Mg(SiO₄)₂, which influence the ceramic’s microstructure and mechanical properties. Increased magnesia content reduces porosity and enhances crushing strength, while heating to 1650 °C significantly improves densification and nearly doubles cold crushing strength, from 43.77–58.97 MPa at 1550 °C to 76.79–95.67 MPa at 1650 °C. These findings suggest that the synthesized refractories exhibit properties comparable to commercial magnesia–hercynite bricks, with potential for the further development for industrial rotary kiln applications. Full article

This study investigates the potential of utilizing industrial by-products—mill scale (MS) and aluminum dross (AD)—as sources of Fe₂O₃ and Al₂O₃, respectively, for hercynite (FeAl₂O₄) production. Through combustion of MS-AD-graphite systems at 1550 °C under air atmosphere, hercynite-based refractory materials were synthesized. Results confirm the viability of this upcycling approach for hercynite synthesis. During the formation of hercynite, the development of a dendritic structure can be observed, which subsequently fuses into a grain shape. XRD phase analysis using the Rietveld method revealed that the major components of the product with a C/O ratio of 1 were 85.11% FeAl₂O₄, 10.99% Al₂O₃, and 3.9% C. For the product with a C/O ratio of 2, the composition was 82.4% FeAl₂O₄, 13.0% Al₂O₃, and 4.6% C. The combustion of raw pellets with a C/O ratio of 1 at 1550 °C for 1 h in a normal air atmosphere is economically viable for producing hercynite, yielding 85.11 wt%. This approach presents a sustainable and eco-friendly alternative to using commercial raw materials, potentially eliminating the need for virgin alumina and iron ore. By repurposing waste materials from the steel and aluminum industries, this study contributes to the circular economy and aligns with the goal of zero waste. Full article

Secondary aluminum dross is a solid waste generated after removing aluminum from industrial aluminum slag (primary aluminum dross), which is included in the European Hazardous Waste List because of harmful substances such as aluminum nitride. More and more SAD is being directly disposed of in landfills, which will not only harm the ecological environment and human health, but also cause resources. Under the background of green and low-carbon circular economy, nitrogen removal and resource recycling of SAD are very important environmental pollution, resource and the economic benefits of the aluminum industry. In this study, a new method was introduced to explore the interaction between various factors in the denitrification process by using the response surface method, and the optimal denitrification process conditions were predicted and determined by a regression equation that is, the denitrification rate of SAD was 99.98% at the reaction time of 263 min, reaction temperature of 95 ℃ and concentration of 6.5 wt.%. Furthermore, the content of Al₂O₃ in SAD was successfully elevated to 98.43% through the reaction carried out in a 10 wt.% NaOH solution system at the controlled temperature of 90 °C for 5 h. It was summarized that the wet treatment methodology can efficiently eliminate aluminum nitride (AlN) from SAD and heighten the Al₂O₃ grade to meet metallurgical standards. This research is expected to eliminate the adverse impact of SAD on the environment and its safety risks, and provide an innovative method for the sustainable resource utilization of SAD. Full article

This study created ceramic preforms with a 3D network structure (TAD_3D) by using treated aluminum dross (TAD) and kaolin slurry, with 30 ppi polyurethane foam as a template via the sacrificial template method. TAD_3D/5A05Al composites were then produced via pressureless infiltration of 5A05Al aluminum alloy into TAD_3D. The corrosion behavior and resistance of TAD_3D/5A05Al in salt spray were assessed via neutral salt spray corrosion (NSS), scanning electron microscopy (SEM), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests. The results showed that after 24 to 360 h of NSS corrosion, the corrosion of the 5A05 matrix was primarily pitting, with pits expanding and deepening over time, and showing a tendency to interconnect. The main corrosion products were MgAl₂O₄, Al(OH)₃, and Al₂O₃. As corrosion progressed, these products increased and filled cracks, pits, and grooves at the composite interface on the material’s surface. Corrosion products transferred to the grooves at the composite interface and grew on the ceramic surface. Corrosion products on the ceramic framework and the Al matrix can form a continuous passivation film covering the composite surface. PDP and EIS results indicated that the composite’s corrosion resistance decreased by 240 h but increased after that time. After 240 h, the surface passivation film can weaken corrosion effects and enhance the composite’s resistance, although it remained weaker than that of the uncorroded samples. Additionally, grooves at the composite interface deepened over time, with loosely structured corrosion products inside, potentially leading to severe localized corrosion. Full article

This study utilizes desalted and denitrated treated aluminum dross (TAD) as a raw material, along with kaolin and 10 ppi (pores per inch) polyurethane foam as a template. The slurry is converted into an aluminum dross green body with a three-dimensional network structure using the impregnation method. A three-dimensional network aluminum dross ceramic framework (TAD_3D) is created at a sintering temperature of 1350 °C. The liquid 5A05 aluminum alloy at a temperature of 950 °C infiltrates into the voids of TAD_3D through pressureless infiltration, resulting in TAD_3D/5A05Al composite material with an interpenetrating phase composite (IPC) structure. The corrosion behavior of TAD_3D/5A05 composite material in sodium chloride solution was examined using the salt spray test (NSS) method. The study shows that the pores of the TAD3D framework, produced by sintering aluminum dross as raw material, are approximately 10 ppi. The bonding between TAD3D and 5A05Al interfaces is dense, with strong interfacial adhesion. The NSS corrosion time ranged from 24 h to 360 h, during which the composite material underwent pitting corrosion, crevice corrosion and self-healing processes. Results from Potentiodynamic Polarization (PDP) and Electrochemical Impedance Spectroscopy (EIS) indicate that, as corrosion progresses, the E_corr of TAD_3D/5A05Al decreases from −0.718 V to −0.786 V, and I_corr decreases from 0.398 μA·cm⁻² to 0.141 μA·cm⁻². A dense oxide film forms on the surface of the composite material, increasing the anodic Tafel slope and decreasing the cathodic Tafel slope, thus slowing down the rates of cathodic and anodic reactions. Factors such as lower interface corrosion resistance or a relatively weak passivation film at the interface do not significantly diminish the corrosion resistance of TAD_3D and 5A05Al. The corrosion resistance of the composite material initially decreases and then increases. Full article

During hot-dip galvanization, wastes such as bottom dross, zinc ash, spent pre-treatment solutions, and galvanizing flue dust (GFD) are generated. In scientific publications, research devoted to GFD waste recycling is absent, and companies generating this waste require a solution to this complex problem. GFD is often landfilled in hazardous waste landfills. However, it is possible to process this waste hydrometallurgically, where GFD is first leached, the solution is refined, and finally, zinc metal is obtained by electrowinning. During specific environmentally friendly leaching, not all solid GFD is dissolved, and the aim of this study is to process the remaining solid GFD residue. The analysis shows that the GFD residue material mainly contains zinc (42.46%) in the form of oxides, but there is also a small amount of polluting elements such as Al, Fe, and Pb. This study examines the leaching of the samples in HCl and H₂SO₄ under different conditions with the aim of obtaining a solution with a high concentration and high leaching efficiency of zinc. The L/S ratio of 3, 4 M H₂SO_4, and ambient temperature proved to be optimal for the leaching of the GFD residue, where 96.24% of zinc was leached out, which represents a zinc concentration of 136.532 g/L. Full article

Waste fly ash (WFA) and secondary aluminum dross (SAD) are common solid wastes inducing environmental pollution. These materials contain certain active substances that can be used in cement-based materials. Therefore, cement concrete can be used to solidify these solid wastes. In this study, the influence of the assembly unit of secondary aluminum dross (SAD) and waste fly ash (WFA) on the properties of ultra-high-performance concrete (UHPC) is investigated. The slump flow, the plastic viscosity, the yield shear stress, and the initial setting time of fresh UHPC are measured. Moreover, the flexural and compressive strengths and the dry shrinkage rate (DSR) are determined. The electrical resistance and reactance are tested. The electron microscopy spectroscopy (EDS), thermogravimetric analysis (TG), and X-ray diffraction spectrum (XRD) curves are obtained for revealing the mechanism of macroscopic performances. Results show that due to the optimal specific surface area and the volcanic ash effect, the UHPC with the assembly unit of 50% SAD and 50% WFA provides the highest slump flow, DSR, and mechanical strengths, while the corresponding plastic viscosity, yield shear stress, and electrical resistance are the lowest. The SAD can delay the setting time of UHPC. The relationship between the electrical resistance or the electrical reactance and the mass ratio of SAD accords with the quadratic function. The corresponding electrical resistance is the lowest. The relationship between the mechanical strengths and the electrical resistance fits with the cubic function. The leaching amounts of Z_n and C_r increase in the form of cubic function with the immersing time. Meanwhile, the SAD can decrease the Z_n and C_r by 0%–46.3% and 0%–45.2% respectively. As obtained from the EDS results, the element of Al is increased by adding SAD. The XRD curves show that the crystals of Al₂O₃ are increased and the SiO₂ crystals are decreased by the added SAD. UHPC with 50% SAD exhibits the highest compact microstructures and the least Ca(OH)₂ and 3CaO·S_iO₂ hydration products. The TG results show that UHPC with 50% SAD shows the lowest TG values of all the groups. This research will provide new UHPC materials and techniques applied in solidifying the WFA and SAD in the future. Full article

In light of globalization and escalating environmental concerns, society is increasingly confronted with the challenge of implementing the concept of a circular economy, which promotes the recycle of waste materials and offers a promising solution. Aluminum dross, a byproduct of the aluminum production process, poses environmental issues when not properly managed. Therefore, this study examined the technical and financial feasibility of implementing an industrial process for the recovery and transformation of aluminum dross into raw materials for use in cementitious materials. From a technical perspective, two processes were evaluated: washing and the grindability of the material. An X-ray diffraction analysis allowed to verify an approximately 88% reduction in AlN (a compound that produces ammonia gases when reacting with water) after washing the material. The most efficient grinding process was achieved using an impact mill. The financial feasibility study was carried out through cash flow forecasting, which revealed that a minimum selling price of USD 0.12 per kilogram of processed material could generate a return rate of 9.7% over a five-year period. These results present opportunities for the metal and construction industries to develop products with low CO₂ emissions by reintegrating aluminum dross into a productive cycle. Moreover, this work serves as a valuable reference for policymakers and environmental authorities seeking to formulate new legislation or incentives that encourage companies to invest in environmentally focused projects. Full article

Aluminum oxide production from aluminum filings, which are a byproduct of several industrial machining processes and cannot be recycled to attain bulk aluminum (Al), is vital due to its wide use in scientific research and industry. The goal of this paper is to produce ultrafine and down-to-the-nanoscale alumina powder (Al₂O₃), starting from a waste Al filings. The microstructure and composition of the starting Al used were investigated using scanning electron microscopy (SEM), which was equipped with an attached energy dispersive spectrometer (EDS) unit. The results of this investigation confirmed that the starting Al was mainly Al–Mg alloy. Al₂O₃ was produced using two routes: The first involved the burning of aluminum hydroxide Al(OH)₃ that was precipitated from aluminum chloride solution (AlCl₃) resulting from dissolving the Al filings in 2M HCl. The second route involved direct precipitation as a reaction product of aluminum chloride with sodium carbonate solution. The Al₂O₃ produced using both routes, as well as the intermediate product Al(OH)₃, were studied by SEM. The results demonstrate that the nanoscale range size was reached after milling of the produced Al₂O₃. Following thorough washing with distilled water, the EDS and the XRD techniques confirmed the formation of Al₂O₃, with no residual salt detected. The EDS results showed that the ratios of Al and O in the produced Al₂O₃ were about 96% of the ideal compound ratios. The XRD analysis also revealed the amorphous structure of the standard and the produced Al(OH)₃, whereas the phases of the produced Al₂O₃ were either crystalline or amorphous. In our study, the Al₂O₃ percentage yield was about 77%, and this value obviously depends on the percentage of Al dross in the original Al filings. Overall, this research provides a novel contribution to the production of alumina powder in the nano-range starting from an aluminum filings byproduct, thereby reducing the dependence on known sources of aluminum. Full article

Al₂O₃-bonded SiAlON ceramic with self-coating was prepared using aluminum dross and silicon solid waste as starting materials under ambient air conditions. The changes in phase, microstructure, and physical properties of the ceramic with temperature were analyzed and the formation mechanism of the SiAlON phase was elucidated. The results showed that higher temperature was more suitable for the preparation of SiAlON ceramics. As the temperature increased from 1400 to 1600 °C, the main phases in the ceramic transformed from mullite, Al₂O₃, and SiAlON to Al₂O₃ and SiAlON. An Al₂O₃-rich layer spontaneously coated the surface of the porous ceramic as Al melted and oxidized at high temperature. The thickness of this layer decreased as the temperature increased. The presence of Al₂O₃-rich coating layer impeded air flow, allowing nitriding of Si and Al, and the formation of the SiAlON phase in ambient air conditions. This study not only presents a strategy to successfully recycle aluminum dross and silicon solid waste but also offers a straightforward approach to preparing SiAlON material in air atmosphere. Full article

This work first transformed hazardous aluminum waste into low-cost MgAl−layered double hydroxide@ANA zeolite (LDHs@ANA) composite for dye wastewater adsorption, which was meaningful for waste recovery and pollution control. Based on this strategy, the Al(OH)₃ extracted from secondary aluminum dross (a hazardous waste in the aluminum industry) was used as an aluminum source to synthesize LDHs@ANA composite, which had more excellent adsorption capacity to methylene blue than MgAl−LDHs and ANA alone. The composite consisted of spherical ANA particles uniformly covered with LDH nanosheets, which effectively avoided a large amount of aggregation between nanosheets and increased specific surface areas and pore volumes. The kinetic results indicated that the adsorption process conformed to the pseudo-second-order kinetic model, and the adsorption site was the main factor affecting the adsorption process. The equilibrium studies showed the adsorption process was exothermic, and the Langmuir model best fitted for the adsorption process, with a maximum adsorption capacity reaching 65.27 mg/g. Meanwhile, the effects of pH, adsorbent concentration, initial methylene blue concentration, and adsorption time on the LDHs@ANA were analyzed. Overall, this work provides a fresh concept for the preparation of low-cost adsorbents from aluminum waste. Full article

Dross in a Zn-55wt%Al-1.6wt%Si metal coating bath is a mixture of bath metal and the quaternary intermetallic phase τ5c-Al₂₀Fe₅Si₂(+Zn). Understanding the properties and formation of dross in a hot-dip Al-Zn galvanizing bath at the processing temperature (~600 °C) is critical for improving the production quality of steel sheet coating. However, dross analysis is usually conducted at room temperature with dross samples taken from the hot-dip bath and it is not known how representative these samples are of the phase(s) existing at high temperature. Using in-situ synchrotron X-ray diffraction (XRD), the crystal lattice and the coefficient of thermal expansion (CTE) of the intermetallic phase have been determined in the temperature range of 30 °C to 660 °C. Phase formation and phase stability of the intermetallic phase in the dross powder have been determined, providing fundamental knowledge for optimizing the production and quality of steel sheet coating. Full article