A Denitrification-Phase Transition and Protection Rings (DPP) Process for Recycling Electrolytic Aluminum Dross

Abstract

The continuous growth of the aluminum electrolysis industry has produced large amounts of electrolytic aluminum dross (EAD) as a waste product, which lacks proper recycling methods and poses serious environmental pollution risks. A short and clean process for recycling EAD is proposed involving the preparation of anode protection rings, which can effectively reduce the corrosion of anode steel stubs, improve the quality of molten aluminum, and return to aluminum reduction cells for recycling alumina and fluoride after being broken. The phase transition path of Al(OH) 3 in denitrified EAD by thermal decomposition was bayerite → boehmite → γ-Al 2 O 3 → α-Al 2 O 3 . The calcination temperature should be controlled at 600−800 °C for 2 h to obtain a higher content of activated γ-Al 2 O 3 . The average dissolution rate of denitrified EAD in the aluminum electrolyte was 7.33 times higher than that before denitrification treatment. After using EAD anode protection rings, the corrosion rate of anode steel stubs decreased by 67.7% on average. Furthermore, the iron and silicon contents in the molten aluminum were reduced by 18.57% and 6.25%, respectively. The alumina consumption for producing primary aluminum was reduced by 8.14 kg•t −1 . The experimental results suggest that the proposed process is economical and promising for EAD recycling.

Cleaner Process for the Selective Extraction of Lithium from Spent Aluminum Electrolyte Slag

“…Secondary lithium resources mainly include spent lithium batteries, electronic products, glass powder, and spent aluminum electrolyte slag, while with the mass production of aluminum products, the industrial accumulation of spent aluminum electrolyte slag is also increasing. − It is estimated that 10–20 kg of spent aluminum electrolyte slag is produced per ton of primary aluminum production . Cryolite, calcium fluoride, lithium fluoride, and other substances are usually added as spent aluminum electrolyte slag in aluminum electrolysis.…”

Clean Process for Selective Recovery of Lithium Carbonate from Waste Lithium-Bearing Aluminum Electrolyte Slag

“…As of October 31, 2022, the prevailing price of battery-grade lithium carbonate had risen to $79,383.7/ton. , Because of demand for lithium resources and commercial opportunity, researchers have directed their focus toward recycling of spent lithium-ion batteries − and using low-grade raw materials (low-grade lithium ore smelting − and saline brine lithium − ) in metallurgical processes. Moreover, a substantial volume of lithium-rich aluminum electrolyte slags is generated during the aluminum electrolysis process due to the usage of low-grade bauxite and lithium salts. − Considering the environmentally hazardous character of aluminum electrolyte slag and the rising price of lithium carbonate, the extraction and recovery of lithium from lithium-bearing aluminum electrolytes emerge as a favorable option …”