Recycling of silicon from silicon cutting waste by Al-Si alloying in cryolite media and its mechanism analysis

Environmental Pollution
Donghui WeiPengfei Xing

Abstract

More than 40% of the crystalline silicon has been wasted as silicon cutting waste (SCW) during the wafer production process. This waste not only leads to resource wastage but also causes environmental burden. In this paper, SCW produced by the diamond-wire sawing process was recycled by Al-Si alloying process. Cryolite was introduced to the reaction system to dissolve the SiO2 layer existed on the surface of the Si particles in SCW. Alloys with 12.02 wt% of Si were prepared and the mechanism of the alloying process was investigated in detail. The Si-Al-cryolite system and SiO2-Al-cryolite system were studied individually to analyze the reaction process and transferring behavior of Si and SiO2 in SCW. The SiO2 shell was firstly transformed into Si-O-F ions. Then the Si-O-F ions diffused to the reaction interface by the effect of the concentration gradient and were reduced to Si by the aluminothermic reduction reaction: 4Al (l) + 3SiO2 (dissolved in the melt) = 3Si (Al)+ 2Al2O3 (dissolved in the melt). Then the internal Si particles were released into cryolite after the dissolution of SiO2 and transferred to the reaction interface by the effect of gravity. The influences of the mass ratio of Al/SCW and agitation modes on the Si c...Continue Reading

References

Mar 16, 2011·Journal of Hazardous Materials·Tzu-Hsuan Tsai
Sep 22, 2018·Journal of Hazardous Materials·Zih-Yao ShenMaw-Tien Lee

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