Study on the Necessity for Deironing from Al-Si Alloys Prepared by CFA via Hydrometallurgy Pretreatment

Abstract

Coal fly ash (CFA), as a major solid waste of coal-fired power plants in China, is widely applied in building materials, pavement, and soil improvement. However, its potential value hasn’t been fully utilized yet. In recent years, CFA has received attractive attention as a potential raw material to prepare Al-Si alloy because of the main components of SiO2, Al2O3 and a small amount of iron in it. The presence of iron in CFA will benefit the process of carbothermic reduction which can be carried out at lower temperature for preparing Al-Si alloys. On the other hand, the content of iron in the Al-Si alloys products need to be controlled strictly, otherwise it will have the significant influence on the mechanical properties of the alloys and lead to the formation of excessive shrinkage defects. In this paper, we studied the necessity for deironing from Al-Si alloys prepared by CFA via hydrometallurgy pretreatment. Results indicate that the optimal route to prepare the qualified Al-Si alloys products is to remove most of the iron from CFA using hydrometallurgical pretreatment before carbothermic reduction. Other pyrometallurgy refining methods are applied to further deironing if necessary after the primary Al-Si alloys are obtained.