Recycling and reuse of kerf-loss silicon from diamond wire sawing for photovoltaic industry

• Published in: Waste management (Elmsford) 2019-02, Vol.84, p.204-210
• Main Authors: Yang, H.L., Liu, I.T., Liu, C.E., Hsu, H.P., Lan, C.W.
• Format: Article
• Language: English
• Subjects: Acid leaching; Carbon; Cutting kerf-loss slurry waste; Diamond; Industry; Metals; Oxygen; Recycle; Recycling; Silicon; Solid Waste
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/j.wasman.2018.11.045

[Display omitted] •Silicon kerf wastes of diamond wire sawing from solar industry were studied.•Remove metals and C by acid leaching and calcination respectively and effectively.•HF was fount effective for leaching Ni.•Recycled silicon had a purity of near 5 N.•Use raw materials to make silicon nitride powder and crucibles for solar industry. With the rapid growth of the global photovoltaic (PV) industry, the waste from PV industry cannot be ignored, especially the solid wastes from silicon kerf loss and the used quartz crucibles from silicon casting. The silicon kerf loss during wafer sawing was nearly 160,000 tonnes and the used crucible waste was nearly 70,000 tonnes in 2017. With the transition of wafering technology from the slurry-based wire to diamond wire sawing, recycling and reuse of kerf-loss silicon have become more feasible due to the lower impurity contents. In this paper, we aimed to find a simple approach to recycle the kerf loss and identify the purity for reuse. We first analyzed the contents of the as-received kerf-loss silicon from the industry. Then, suitable acids and refining procedure were proposed. The metals, especially nickel, could be easily reduced to several ppmw, boron and phosphorous to sub-ppmw, and carbon to several hundred ppmw, while oxygen was less than 5 wt%. Although the purity of the recycled silicon was not sufficient for casting feedstock, it had a comparable purity of about 5 N with the commercial silicon nitride releasing agent and crucibles used in silicon casting for solar cells. Because the nitride crucibles could be reused a few times for casting, the used crucible waste could be significantly reduced as well.