The Investigation of Optimizing Leaching Efficiency of Al in Secondary Aluminum Dross via Pretreatment Operations

Abstract

Secondary aluminum dross (SAD) is an inevitable by-product from the secondary aluminum industry and has caused serious environmental issues. In this study, the effect of pretreatment operations on the subsequent acid leaching operation was studied by process mineralogy, a series of leaching experiments, XRD, and SEM. Leaching results showed that the leaching efficiency of Al in direct acid leaching was only 22.99%. Process mineralogy showed the complex intertexture and continuous network structure in the SAD. Pretreatment operations were extremely efficient in destroying the structure by physical and chemical interaction. Interestingly, by adding the grinding and water leaching operations, the leaching efficiency of total aluminum in the SAD reached approximately 28.70%. XRD results showed that nearly all metallic Al, AlN, and partial Al2O3 were leached by grinding–water leaching–acid leaching. The scanning electron micrographs showed that the residue particles mainly included some insoluble components and had a smooth surface.

Aluminum Recovery from White Aluminum Dross by a Mechanically Activated Phase Separation and Remelting Process

“…These studies were all on black dross treatment, and it caused low Al recovery as a portion of metallic Al was lost in the process. Recoveries of 35% 31 , 28.42% and 24.34% 32 , and 34% 34 have been achieved. The present study, however, is focused on developing a salt-free integrated process to treat white dross; it includes mechanical treatment, followed by Al-rich portion separation and remelting.…”

“…The next patent (US 3,037,711) 29 devoted entirely to liberation of aluminum metal by crushing and grinding was issued in 1962 to Businger of Metallwerke Refonda, Weiderkehr & Co. for a dry milling process which uses a mill to flatten aluminum pieces that are then separated from the friable oxides by screening and air classification. 30 A literature survey [31][32][33][34] revealed a few works on crushing and milling as a method to separate aluminum metal. However, in the literature, there are a limited number of studies on the metallographic characterization of the dross phase separations and the size fractions after milling.…”

“…However, in the literature, there are a limited number of studies on the metallographic characterization of the dross phase separations and the size fractions after milling. [31][32][33][34] Moreover, in the literature the results are described using milling treatment of dross combined with salts, such as Nguyen et al 31 , who investigated the effect of a process consisting of ball milling followed by NaOH leaching to selectively dissolve alumina from black dross. These studies were all on black dross treatment, and it caused low Al recovery as a portion of metallic Al was lost in the process.…”

Synthesis and Performance of PAFS Coagulant Derived from Aluminium Dross

“…The effect of leaching temperatures on turbidity removal efficiency is shown in Figure 1. The temperatures were chosen based on previous studies by other researchers on the effect of varying temperatures on the dissolution of alumina (Sarker et al, 2015;Feng et al, 2020;David & Kopac, 2013). Regression analysis was performed on the experimental data, and results showed that the leaching temperature (X variable) has a significant influence on turbidity removal rate (Y variable) with analysis of variance P<0.05, and therefore Y variable was predicted for different temperature values.…”

Efficient Al Recovery from Aluminum Dross with Simultaneous AlN Separation by a Mechanical Method

“…The Al extraction rate ranged from 78.64% to 93.11% and from 78.35% to 91.99% for ground dross and as-received dross, respectively. Haigang Feng studied the leaching rate of aluminum in secondary AD (SAD) and optimized the pretreatment process by adding grinding and water leaching steps; the SAD total aluminum leaching efficiency reached approximately 28.70% [18]. This increase in efficiency is markedly higher than the loss of AlN because the Al in AlN only accounts for 19.35% of the total Al content in AD.…”