Key Takeaways & Executive Findings
- •• Waste sodium acetate (NaAc) serves as an environmentally friendly additive for complete AlN removal and enhanced Al extraction from secondary aluminum dross (SAD). • Co-sintering at 850°C achieved 93.19% AlN removal and 90.49% Al leaching efficiency, significantly outperforming control conditions. • The process involves exothermic decomposition of NaAc, which facilitates the transformation of aluminum species into soluble phases like Na1.95Al1.95Si0.05O4. • This method offers a cost-effective and sustainable route for hazardous SAD treatment, addressing both environmental risks and resource recovery.
Abstract
Secondary aluminum dross (SAD) is a rich source of recyclable aluminum but poses considerable risk due to its high AlN content. Therefore, thoroughly removing AlN is essential, but intricate aluminum components and expensive additives pose challenges to the process. In this study, waste sodium acetate is proposed as an environmentally friendly additive for completely removing AlN and enhancing the extraction of aluminum from SAD. Through the exothermic decomposition of NaAc, reactions can occur at 850°C. AlN removal efficiency reached 93.19% after sintering, whereas Al leaching efficiency in the subsequent leaching process reached 90.49%, which were 37.86% and 375.26% higher than the removal efficiency of the control, respectively. These favorable results were attributed to the comprehensive transformation of aluminum species. The formation of soluble phase Na1.95Al1.95Si0.05O4 occurred during the destruction of the Al2O3 layer surrounding AlN and the transformation of other aluminum components. AlN decomposed upon contact with NaAc. Therefore, this study utilizes the decomposition properties of NaAc to provide an efficient and environmentally friendly route for removing AlN and extracting Al from SAD.
1. Introduction
Secondary aluminum dross (SAD), which contains the reactive component AlN and a considerable amount of alumina, is a hazardous waste generated by metallic Al production and processing industries [1–2]. In general, SAD is the residue produced after metallic Al is extracted from primary aluminum dross, consisting of 40wt%–60wt% Al2O3, 10wt%–30wt% AlN, 5wt%–15wt% salts and other components [3–4]. In recent years, the world aluminum industry experienced steady growth, with annual output of 70.58 million tons in 2023; that is, 0.44–0.71 million tons of SAD was generated (6.3–10 kg SAD per ton of Al electrolytic production) [5–6], theoretically containing 44–213 thousand tons of AlN, which enables hydrolysis to produce environmentally hazardous NH3 and more than 0.23 million tons of potentially recyclable Al2O3 [7–8]. Therefore, a feasible process of efficiently extracting Al while fully removing AlN is of great significance for SAD disposal.
Currently employed methods for decomposing AlN and extracting Al from SAD mainly include hydrometallurgical and pyrometallurgical routes [9]. In hydrometallurgy, Al species react directly with concentrated acid or alkali solutions. The hydrolysis of AlN to bayerite and pseudo-boehmite can proceed spontaneously and can be accelerated by increasing temperature [10–11]. Silica aluminate precipitates formed in hydrolysis side reactions could enhance nitrogen removal efficiency, decreasing residual nitrogen content to 0.39wt% [12]. Furthermore, Al species, including metallic Al, AlN, and MgAl2O4, in SAD could be converted into Al3+ or [Al(OH)4]− through a reaction with concentrated acid or alkali, and subsequent pH adjustment leads to the precipitation of the products as Al(OH)3. Corundums and spinels inhibit the transformation of aluminum, leading to the 40% extraction efficiency of alkali leaching [13]. Consequently, the application of hydrometallurgical methods is limited because of the need for ammonia treatment and substantial quantities of concentrated acids or alkalis.
In pyrometallurgical processes, the porous structure of AlN surface oxide layers facilitates AlN removal through high-temperature oxidation. AlN removal efficiency could reach up to 90.86% after 180 min of sintering at 1200°C [14]. Synergistically treating hazardous waste, such as fly ash and pickling sludge, through heat treatment ensures the removal of AlN, the fixation of F and heavy metals, and the volatilization of Cl [15–17]. Additionally, alkaline additives were added to transform Al species into soluble phases NaAlO2 and 12CaO·7Al2O3, and then Al was recovered through leaching and carbonation decomposition [18]. This process was extensively used in the extraction of Al from tailings and slags, exhibiting remarkable efficiency for SAD [19–20]. When exogenous Na2CO3 was added to SAD and sintered at 1150°C for 60 min, the AlN removal and Al leaching efficiency increased to 98.93% and 90.79%, respectively [1]. The efficienc
Loading authentic research manuscript (Pages 1–5)...
Xiang Li, Nengwu Zhu, Yunhao Xi, Fei Li, Pengfei Zhang (2025). Efficient AlN decomposition and Al species transformation in secondary aluminum dross through co-sintering with waste sodium acetate. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-2990-9
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the main objective of this study?
The main objective is to develop an efficient and environmentally friendly method for removing AlN and extracting aluminum from secondary aluminum dross (SAD) using waste sodium acetate as an additive.
How does waste sodium acetate contribute to AlN removal?
Waste sodium acetate undergoes exothermic decomposition at 850°C, which facilitates the destruction of the Al2O3 layer surrounding AlN and promotes the transformation of aluminum species into soluble phases, thereby enhancing AlN removal and aluminum extraction.
What are the key performance indicators of the proposed method?
The method achieves 93.19% AlN removal efficiency and 90.49% aluminum leaching efficiency, which are significantly higher than control conditions, demonstrating its effectiveness.
Why is this method considered environmentally friendly?
The method utilizes waste sodium acetate, a byproduct, as an additive, reducing the need for expensive and potentially hazardous chemicals. It also operates at a relatively lower temperature (850°C) compared to traditional methods, and effectively mitigates the environmental risks associated with AlN in SAD.
What are the potential applications of this research?
This research provides a sustainable route for the treatment of secondary aluminum dross, enabling resource recovery of aluminum while reducing environmental pollution. It can be applied in the aluminum recycling industry and waste management sectors.
Related Technical Papers & Translations
Direct Repair of the Crystal Structure and Coating Surface of Spent LiFePO4 Materials Enables Superfast Li-Ion Migration
The rapid accumulation of spent LiFePO4 (LFP) cathodes from retired lithium-ion batteries necessitates the development of effective and environmental-friendly recycling strategies. In this context, direct regeneration has emerged as a promising approach for reclaiming LFP cathode materials, offering a streamlined pathway to restore their electrochemical functionality. We report an integrated regeneration protocol that simultaneously repairs the degraded crystal structure and reconstructs the damaged carbon coating in spent LFP. The regenerated cathode material had superfast lithium-ion diffusion kinetics and a stable cathode–electrolyte interface, giving a remarkable rate capability with specific capacities of 122 mAh g−1 at 5C and 106 mAh g−1 at 10C (1C = 170 mA g−1). It also maintained capacities of 110.7 mAh g−1 (5C) and 84.1 mAh g−1 (10C) after 400 cycles. It could be used in harsh environments and could be stably cycled at subzero temperatures (−10 and −20 °C) and in solid-state electrolyte batteries. Life cycle assessment combined with economic evaluation using the EverBatt model reveals that this direct regeneration approach has high economic and environmental benefits.
Oxide Semiconductor for Advanced Memory Architectures: Atomic Layer Deposition, Key Requirement and Challenges
Oxide semiconductors (OSs), introduced by the Hosono group in the early 2000s, have evolved from display backplane materials to promising candidates for advanced memory and logic devices. The exceptionally low leakage current of OSs and compatibility with three-dimensional (3D) architectures have recently sparked renewed interest in their use in semiconductor applications. This review begins by exploring the unique material properties of OSs, which fundamentally originate from their distinct electronic band structure. Subsequently, we focus on atomic layer deposition (ALD), a core technique for growing excellent OS films, covering both basic and advanced processes compatible with 3D scaling. The basic surface reaction mechanisms—adsorption and reaction—and their roles in film growth are introduced. Furthermore, material design strategies, such as cation selection, crystallinity control, anion doping, and heterostructure engineering, are discussed. We also highlight challenges in memory applications, including contact resistance, hydrogen instability, and lack of p-type materials, and discuss the feasibility of ALD-grown OSs as potential solutions. Lastly, we provide an outlook on the role of ALD-grown OSs in memory technologies. This review bridges material fundamentals and device-level requirements, offering a comprehensive perspective on the potential of ALD-driven OSs for next-generation semiconductor memory devices.
Laser powder bed fusion of biodegradable Zn-4Cu alloy: Processing, microstructure and properties
Zn's natural degradability and biocompatibility make it a promising candidate for implants, however, its mechanical properties remain insufficient for bone applications. In this study, the performance of Zn was enhanced by developing Zn-Cu alloys via laser powder bed fusion (LPBF). Optimal LPBF parameters for forming stable tracks were achieved by adjusting laser power and scanning speed. Under optimized conditions of 100 W and 100 mm/s, high-density (99.58%) Zn-Cu alloys with improved hardness (68.2HV) and yield strength (160 MPa) were achieved. These improvements are attributed to solid solution strengthening, segregation strengthening, and grain refinement. The Zn-Cu alloys also demonstrated favorable degradation behavior, with a rate of 0.16 mm/year. This degradation is primarily driven by micro-galvanic corrosion between the CuZn5 phase and Zn matrix, along with refined grains and increased grain boundary density. This work demonstrates a viable strategy for fabricating Zn-based implants with enhanced structural integrity and mechanical performance via LPBF.