Study on removal of impurities in aluminum by one-step vacuum-rotary crystallization method

In this study, aluminum was purified by the rotary crystallization method. In order to enhance the impurity removal, the vacuum system was introduced into the rotary crystallization process, and the synergistic mechanism of the vacuum and rotation for impurity removal has been investigated systematically. Results show that the combination of a vacuum system and rotational mechanism can provide thermodynamic driving force and channels for the volatilization of volatile impurities (zinc (Zn) and magnesium (Mg)), and it can also improve interface mass transfer conditions and further promote the removal of non-volatile impurities (silicon (Si) and iron (Fe)). Among them, vacuum degree, rotation rate, and crystallization radius were identified as the primary factors for this process. Under the rotation rate of 80 rpm and vacuum degree of 10 -1 Pa, the maximum removal efficiencies of Si, Fe, and Mg can reach 75%, 81%, 93% at the optimal crystal radius of 20 mm, and that of Zn can also reach 91% at the optimal crystal radius of 25 mm. This method takes advantage of the vacuum system and rotational technology to deeply remove Si, Fe, Zn, and Mg in aluminum by a one-step process, providing a valuable reference for advanced aluminum purification.