Boron separation from Si–Sn alloy by slag treatment

  • Rowaid Al-khazraji
  • Ya-qiong Li
  • Li-feng ZhangEmail author


This study investigates a purification process for metallurgical-grade silicon (MG-Si) in which Si is alloyed with tin (Sn) and CaO–SiO2–CaCl2 slag is used to remove boron (B) impurity. Acid leaching was performed to remove the Sn phase after slag refining to recover high-purity Si from the Si–Sn alloy. The effect of refining time was investigated, and acceptable refining results were realized within 15 min. The effects of slag composition and Sn content on the removal of B were also studied. The results indicate that increasing Sn content favors B removal. With the increase of Sn to 50% of the alloy, the final B content decreased to 1.1 × 10−4wt%, 93.9% removal efficiency.


boron removal metallurgical grade silicon Si–Sn alloy slag refining 


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This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 51334002 and 51604023), Beijing Key Laboratory of Green Recycling and Extraction of Metals (GREM), the Laboratory of Green Process Metallurgy and Modeling (GPM2) and the High Quality steel Consortium (HQSC) at the School of Metallurgical and Ecological Engineering at University of Science and Technology Beijing (USTB), the Chinese government scholarship information System C.S.C, China.


  1. [1]
    A. Luque and S. Hegedus, Handbook of Photovoltaic Science and Engineering, John Wiley & Sons, Hoboken, 2011, p. 56.Google Scholar
  2. [2]
    K. Suzuki and N. Sano, Thermodynamics for removal of boron from metallurgical silicon by flux treatment, [in] Tenth EC Photovoltaic Solar Energy Conference, Dordrecht, 1991, p. 273.Google Scholar
  3. [3]
    H. Lai, L.Q. Huang, H.P. Xiong, C. Gan, P.F. Xing, J.T. Li, and X.T. Luo, Hydrometallurgical purification of metallurgical grade silicon with hydrogen peroxide in hydrofluoric acid, Ind. Eng. Chem. Res., 56(2016), No. 1, p. 311.CrossRefGoogle Scholar
  4. [4]
    J. Safarian and M. Tangstad, Vacuum refining of molten silicon, Metall. Mater. Trans. B, 43(2012), No. 6, p. 1427.CrossRefGoogle Scholar
  5. [5]
    J.C.S. Pires, A.F.B. Braga, and P.R. Mei, Profile of impurities in polycrystalline silicon samples purified in an electron beam melting furnace, Sol. Energy Mater. Sol. Cells, 79(2003), No. 3, p. 347.CrossRefGoogle Scholar
  6. [6]
    K. Arafune, E. Ohishi, H. Sai, Y. Ohshita, and M. Yamaguchi, Directional solidification of polycrystalline silicon ingots by successive relaxation of supercooling method, J. Cryst. Growth, 308(2007), No. 1, p. 5.CrossRefGoogle Scholar
  7. [7]
    Y. Lei, W.H. Ma, G.Q. Lv, K.X. Wei, S.Y. Li, and K. Morita, Purification of metallurgical–grade silicon using zirconium as an impurity getter, Sep. Purif. Technol., 173(2017), No. 1, p. 364.CrossRefGoogle Scholar
  8. [8]
    J.T. Wang, X.D. Li, Y.M. He, N. Feng, X.Y. An, F. Teng, C.T. Gao, C.H. Zhao, Z.X. Zhang, and E.Q. Xie, Purification of metallurgical grade silicon by a microwave–assisted plasma process, Sep. Purif. Technol., 102(2013), No. 1, p. 82.CrossRefGoogle Scholar
  9. [9]
    R.H. Hopkins and A. Rohatgi, Impurity effects in silicon for high efficiency solar cells, J. Cryst. Growth, 75(1986), No. 1, p. 67.CrossRefGoogle Scholar
  10. [10]
    R.N. Hall, Segregation of impurities during the growth of germanium and silicon, J. Phys. Chem., 57(1953), No. 8, p. 836.CrossRefGoogle Scholar
  11. [11]
    J.J. Wu, Y.L. Li, K.X. Wei, B. Yang, and Y.N. Dai, Boron removal in purifying metallurgical grade silicon by CaO−SiO2 slag refining, Trans. Nonferrous Met. Soc. China, 24(2014), No. 4, p. 1231.CrossRefGoogle Scholar
  12. [12]
    J.J. Wu, W.H. Ma, B.J. Jia, B. Yang, D.C. Liu, and Y.N. Dai, Boron removal from metallurgical grade silicon using a CaO−Li2O−SiO2 molten slag refining technique, J. Non–Cryst. Solids, 358(2012), No. 23, p. 3079.CrossRefGoogle Scholar
  13. [13]
    Y. Wang, X.D. Ma, and K. Morita, Evaporation removal of boron from metallurgical–grade silicon using CaO−CaCl2−SiO2 slag, Metall. Mater. Trans. B, 45(2014), No. 2, p. 334.CrossRefGoogle Scholar
  14. [14]
    M.D. Johnston and M. Barati, Distribution of impurity elements in slag–silicon equilibria for oxidative refining of metallurgical silicon for solar cell applications, Sol. Energy Mater. Sol. Cells, 94(2010), No. 12, p. 2085.CrossRefGoogle Scholar
  15. [15]
    L.A.V. Teixeira and K. Morita, Removal of boron from molten silicon using CaO−SiO2 based slags, ISIJ Int., 49(2009), No. 6, p. 783.CrossRefGoogle Scholar
  16. [16]
    X.D. Ma, T. Yoshikawa, and K. Morita, Purification of metallurgical grade Si combining Si−Sn solvent refining with slag treatment, Sep. Purif. Technol., 125(2014), No. 2, p. 264.CrossRefGoogle Scholar
  17. [17]
    L.Q. Huang, H.X. Lai, C.H. Gan, H.P. Xiong, P.F. Xing, and X.T. Luo, Separation of boron and phosphorus from Cu–alloyed metallurgical grade silicon by CaO−SiO2−CaCl2 slag treatment, Sep. Purif. Technol., 170(2016), No. 1, p. 408.CrossRefGoogle Scholar
  18. [18]
    M. Li, T. Utigard, and M. Barati, Removal of boron and phosphorus from silicon using CaO−SiO2−Na2O−Al2O3 flux, Metall. Mater. Trans. B, 45(2014), No. 1, p. 221.CrossRefGoogle Scholar
  19. [19]
    O. Kubaschewski and C.B. Alcock, Metallurgical Thermochemistry, Pergamon Press, Oxford, 1979, p. 89.Google Scholar
  20. [20]
    Y.V. Meteleva–Fischer, Y.X. Yang, R. Boom, B. Kraaijveld, and H. Kuntzel, Microstructure of metallurgical grade silicon and its acid leaching behaviour by alloying with calcium, Miner. Process. Extr. Metall., 122(2013), No. 4, p. 229.CrossRefGoogle Scholar
  21. [21]
    J.Y. Li, P.P. Cao, P. Ni, Y.Q. Li, and Y. Tan, Enhanced boron removal from metallurgical grade silicon by the slag refining method with the addition of tin, Sep. Purif. Technol., 51(2016), No. 9, p. 1598.Google Scholar
  22. [22]
    J. Cai, J.T. Li, W.H. Chen, C. Chen, and X.T. Luo, Boron removal from metallurgical silicon using CaO−SiO2−CaF2 slags, Trans. Nonferrous Met. Soc. China, 21(2011), No. 6, p. 1402.CrossRefGoogle Scholar

Copyright information

© University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Rowaid Al-khazraji
    • 1
    • 2
  • Ya-qiong Li
    • 1
    • 2
  • Li-feng Zhang
    • 1
    • 2
    Email author
  1. 1.School of Metallurgical and Ecological EngineeringUniversity of Science and Technology BeijingBeijingChina
  2. 2.Beijing Key Laboratory of Green Recycling and Extraction of MetalUniversity of Science &Technology BeijingBeijingChina

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