Effect of salt/oxide interaction on the process of aluminum recycling

The goal of this work was to study the salt/oxide interactions during the process of aluminum recycling in rotary furnaces, which uses salts to protect the burden. Microstructure analysis was the main tool to analyze the morphologies of aluminum dross and its interactions with liquid salt flux; consequently the study was carried out through scanning electron microscope coupled with an energy dispersive X-ray spectrometry detector. Drosses collected from aluminum can recycling industries were used. Tests were carried out using equimolar mixtures of sodium and potassium chlorides. The results revealed that drosses are heterogeneous systems composed essentially of oxides and aluminum. The aluminum oxides develop a chain microstructure, with a high specific surface area, that traps aluminum. The molten salt corrodes this structure and breaks the oxide links, consequently liberating the retained aluminum.