Silicon Kerf Recovery via Acid Leaching Followed by Melting at Elevated Temperatures

Silicon Kerf Recovery via Acid Leaching Followed by Melting at Elevated Temperatures

The aim of this work was to study the purification of silicon kerf loss waste (KLW) by a combination of single-acid leaching followed by inductive melting at high temperatures with an addition of fluidized bed reactor (FBR) silicon granules. The KLW indicated an average particle size (D50) of approx...

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Bibliographic Details
Published in:Recycling (Basel) Vol. 9; no. 4; p. 66
Main Authors: Mubaiwa, Tinotenda, Garshol, Askh, Azarov, Alexander, Safarian, Jafar
Format: Journal Article
Language:English
Published: Basel MDPI AG 01-08-2024
Subjects:
Acid leaching
Acids
Combined treatment
Crucibles
Electron microscopy
Fluidized bed reactors
Fluidized beds
Gallium
Granular materials
Graphite
High temperature
Hot pressing
Impurities
Iron
Kerf
kerf loss waste
Leaching
Low temperature
Mass spectrometry
Melting
Nickel
Oxidation
Particle size
Photovoltaic cells
Polyethylene glycol
recycling
Scanning electron microscopy
Scientific imaging
Silicon
Silicon wafers
solar
Solar cells
Visual observation
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Summary:The aim of this work was to study the purification of silicon kerf loss waste (KLW) by a combination of single-acid leaching followed by inductive melting at high temperatures with an addition of fluidized bed reactor (FBR) silicon granules. The KLW indicated an average particle size (D50) of approximately 1.6 µm, and a BET surface area of 30.4 m2/g. Acid leaching by 1 M HCl indicated significant removal of impurities such as Ni (77%), Fe (91%) and P (75%). The combined two-stage treatment resulted in significant removal of the major impurities: Al (78%), Ni (79%), Ca (85%), P (92%) and Fe (99%). The general material loss during melting decreased with an increasing amount of FBR silicon granules which aided in the melting process and indicated better melting. It was observed that the melting behavior of the samples improved as the temperature increased, with complete melting being observed throughout the crucibles at the highest temperature (1800 °C) used, even without any additives. At lower temperatures (1600 °C–1700 °C) and lower FBR-Si (<30 wt.%) additions, the melting was incomplete, with patches of molten silicon and a lot of surface oxidation as confirmed by both visual observation and electron microscopy. In addition, it was indicated that more reactive and volatile elements (Ga, Mg and P) compared to silicon are partially removed in the melting process (51–87%), while the less reactive elements end up in the final silicon melt. It was concluded that if optimized, the combined treatment of single-acid leaching and inductive melting with the addition of granular FBR silicon has great potential for the recycling of KLW to solar cells and similar applications. Moreover, the application of higher melting temperatures is accompanied by a higher silicon yield of the process, and the involved mechanisms are presented.
ISSN:2313-4321
2313-4321
DOI:10.3390/recycling9040066