Acid Refining of Synthesised Alloys Within the Quaternary System Fe–Si–Ca–AI: Effect of Ferric Ions

Abstract

A systematic study of synthesis of different chemical composition of alloys within the quaternary Fe–Si–Ca–Al system, versus acid leaching refining using HCl with or without FeCl3 has been undertaken. Such study has the aim of achieving an adequate structural composition of Fe–Si alloys, in order to obtain high purity and fine particle size silicon by acid leaching, at more reduced costs. The experimental results show that an adequate control of Fe/Al and Si/Ca concentration ratios can hinder the formation of tetragonal and orthorhombic FeSi2 phases, and consequently promotes a successful refining of ferro-silicon alloys. The presence of ferric ion influences on a distinct way the rate of removal of Al–Fe–Si and Fe–Al–Si–Ca phases, increasing the first and decreasing the second one. The suitable starting composition which could give the expected results must be the following: 92–94% Si; 3–3.5% Fe; 3.5–4% Al and Ca ≤ 0.5%.