Thermodynamic analysis of contamination by alloying elements in aluminum recycling

Kenichi Nakajima, Osamu Takeda, Takahiro Miki, Kazuyo Matsubae, Shinichiro Nakamura, Tetsuya Nagasaka

Research output: Contribution to journalArticlepeer-review

106 Citations (Scopus)


In previous studies on the physical chemistry of pyrometallurgical processing of aluminum scrap, only a limited number of thermodynamic parameters, such as the Gibbs free energy change of impurity reactions and the variation of activity of an impurity in molten aluminum, were taken into account. In contrast, in this study we thermodynamically evaluated the quantitative removal limit of impurities during the remelting of aluminum scrap; all relevant parameters, such as the total pressure, the activity coefficient of the target impurity, the temperature, the oxygen partial pressure, and the activity coefficient of oxidation product, were considered. For 45 elements that usually occur in aluminum products, the distribution ratios among the metal, slag, and gas phases in the aluminum remelting process were obtained. Our results show that, except for elements such as Mg and Zn, most of the impurities occurred as troublesome tramp elements that are difficult to remove, and our results also indicate that the extent to which the process parameters such as oxygen partial pressure, temperature, and flux composition can be changed in aluminum production is quite limited compared to that for iron and copper production, owing to aluminum's relatively low melting point and strong affinity for oxygen. Therefore, the control of impurities in the disassembly process and the quality of scrap play important roles in suppressing contamination in aluminum recycling.

Original languageEnglish
Pages (from-to)5594-5600
Number of pages7
JournalEnvironmental Science and Technology
Issue number14
Publication statusPublished - 2010 Jul 15

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry


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