Diamond-wire sawing silicon waste (DWSSW) as a reductant of the Pidgeon process is beneficial for alleviating the high energy consumption of primary magnesium production. However, the oxygen in DWSSW exists in the form of SiO₂ coated on the Si surface, which is not conducive to the silicothermic reaction and thus affecting the yield of primary magnesium. In this study, we proposed a modified deoxidation method utilizing ammonium fluoride (NH₄F) and hydrochloric acid (HCl) solutions to deoxidize the DWSSW. It was found that NH₄F solution effectively reduced the oxygen content in DWSSW and the deoxidation efficiency increased with higher NH₄F concentration. The addition of HCl further enhanced the deoxidation efficiency, leading to a minimum oxygen content of 1.31% in the deoxidized DWSSW. Transmission electron microscopy (TEM) images indicated a significant reduction in SiO₂ layer thickness, which improves the chemical reactivity of the material. The deoxidized DWSSW was subsequently employed as the reductant in the Pidgeon process to produce primary magnesium. Consequently, the reduction conversion of the Pidgeon process increased by 6.7% compared to raw DWSSW. This work not only provided an effective solution to reduce the oxygen content in DWSSW, but also expanded its application in Pidgeon process, promoting primary magnesium industry towards energy conservation and cost reduction.

It is practically difficult to find titanium sponges with low and stable aluminum impurities on the market even though it is the precondition to prepare high-purity titanium. Analysis indicates that almost all the aluminum impurities in the titanium sponge are inherited from the magnesium used to reduce titanium tetrachloride. However, it remains elusive for decades why magnesium produced through the silicothermic reduction method contains a high content of aluminum impurities with large fluctuations. By recourse to thermodynamic calculations and comparative experiments, we demonstrate that fluorite, a material used as a catalyst in the silicothermic reduction method to produce magnesium, is the chief culprit for the pest aluminum and propose a mechanism to rationalize the observed phenomena. Our findings indicate that one practical way to produce qualified magnesium for the production of high-purity titanium is to abandon fluorite during the production of magnesium with the silicothermic reduction method.