Effect of acid leaching conditions on impurity removal from silicon doped by magnesium

Stine Espelien; Jafar Safarian; Stine Espelien; Jafar Safarian

doi:10.3934/energy.2017.4.636

AIMS Energy

2017, Volume 5, Issue 4: 636-651. doi: 10.3934/energy.2017.4.636

Previous Article Next Article

Research article Topical Sections

Effect of acid leaching conditions on impurity removal from silicon doped by magnesium

Stine Espelien ,
Jafar Safarian ^,

Department of Materials Science and Engineering, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway

Received: 28 April 2017 Accepted: 11 July 2017 Published: 18 July 2017

The effect of magnesium addition into a commercial silicon and its leaching refining behavior is studied for producing solar grade silicon feedstock. Two different levels of Mg is added into a commercial silicon and the leaching of the produced alloys by 10% HCl solution at 60 ℃ for different durations is performed. It is shown that the microstructure of the alloy and in particular the distribution of eutectic phases is dependent on the amount of the added Mg. Moreover, the metallic impurities in silicon such as Fe, Al, Ca and Ti are mainly forming silicide particles with different compositions. These silicides are physically more detached from the primary silicon grains and their removal through chemical and physical separation in leaching is better for higher Mg additions. It is observed that the leaching is more effective for the purification of smaller silicon particles produced from each Mg-doped silicon alloy. It is shown that acid leaching by the applied method is effective to reach more than 70% of phosphorous removal. It is also shown that the purity of silicon is dependent on the total Mg removal and effectiveness of leaching on removing the Mg₂Si phase.
- solar silicon,
- purification,
- magnesium,
- silicide,
- leaching,
- phosphorus
Citation: Stine Espelien, Jafar Safarian. Effect of acid leaching conditions on impurity removal from silicon doped by magnesium[J]. AIMS Energy, 2017, 5(4): 636-651. doi: 10.3934/energy.2017.4.636

Related Papers:

Abstract

The effect of magnesium addition into a commercial silicon and its leaching refining behavior is studied for producing solar grade silicon feedstock. Two different levels of Mg is added into a commercial silicon and the leaching of the produced alloys by 10% HCl solution at 60 ℃ for different durations is performed. It is shown that the microstructure of the alloy and in particular the distribution of eutectic phases is dependent on the amount of the added Mg. Moreover, the metallic impurities in silicon such as Fe, Al, Ca and Ti are mainly forming silicide particles with different compositions. These silicides are physically more detached from the primary silicon grains and their removal through chemical and physical separation in leaching is better for higher Mg additions. It is observed that the leaching is more effective for the purification of smaller silicon particles produced from each Mg-doped silicon alloy. It is shown that acid leaching by the applied method is effective to reach more than 70% of phosphorous removal. It is also shown that the purity of silicon is dependent on the total Mg removal and effectiveness of leaching on removing the Mg₂Si phase.

References

[1]	Safarian J, Tranell G, Tangstad M (2012) Processes for upgrading metallurgical grade silicon to solar grade silicon. Energy Procedia 20: 88–97. doi: 10.1016/j.egypro.2012.03.011
[2]	Safarian J, Tranell G (2016) Silicon purification through magnesium addition and acid leaching, In: 32nd European Photovoltaic Solar Energy Conference and Exhibition, 1011–1014.
[3]	Wu JJ, Long LY, Ma WH, et al. (2014) Boron removal in purifying metallurgical grade silicon by CaO-SiO₂ slag refining. TransNonferrous Met Soc China 24: 1231–1236. doi: 10.1016/S1003-6326(14)63183-6
[4]	Jakobsson LK (2013) Distribution of boron between silicon and CaO-SiO₂, MgO-SiO₂, CaO-MgO-SiO₂ and CaO-Al₂O₃-SiO₂ slags at 1600 °C. Mat Sci Eng 2013: 326.
[5]	Safarian J, Tranell G, Tangstad M (2013) Thermodynamic and kinetic behavior of B and Na through the contact of B-doped silicon with Na₂O-SiO₂ slags. High Temp Mater Proc 44: 571–583.
[6]	Safarian J, Tranell G, Tangstad M (2015) Boron removal from silicon by CaO-Na₂O-SiO₂ ternary slag. Metall Mater Trans E 2: 109–118.
[7]	Safarian J, Tangstad M (2012) Kinetics and mechanism of phosphorus removal from silicon in vacuum induction refining. Metall Mater Trans B 31: 73–81.
[8]	Safarian J, Tangstad M (2012) Vacuum refining of molten silicon. Metall Mater Trans B 43: 1427–1445. doi: 10.1007/s11663-012-9728-1
[9]	Safarian J, Tang K, Hildal K, et al. (2014) Boron removal from silicon by humidified gases. Metall Mater Trans B 1: 41–47.
[10]	Safarian J, Tang K, Olsen JE, et al. (2014) Mechanisms and kinetics of boron removal from silicon by humidified hydrogen. Metall Mater Trans B 47: 1–17.
[11]	Esfahani S (2010) Solvent refining of metallurgical grade silicon using iron. Master thesis of applied science at University of Toronto. Available from: https://tspace.library.utoronto.ca/bitstream/1807/25570/3/Shaghayegh_Esfahani_201011_MASc_thesis.pdf.
[12]	Mohanty BC, Galgali RK (1987) Solvent refining of metallurgical grade silicon. Sol Energ Mat 16: 289–296. doi: 10.1016/0165-1633(87)90077-3
[13]	Dietl J (1983) Hydrometallurgical purification of metallurgical grade silicon. Solar Cells 10: 145–154. doi: 10.1016/0379-6787(83)90015-7
[14]	Santos IC, Gonçalves AP, Santos CS, et al. (1990) Purification of metallurgical grade silicon by acid leaching. Hydrometallurgy 23: 237–246. doi: 10.1016/0304-386X(90)90007-O
[15]	He F, Zheng S, Chen C (2012) The effect of calcium oxide addition on the removal of metal impurities from metallurgical-grade silicon by acid leaching. Metall Mater Trans B 43: 1011–1018. doi: 10.1007/s11663-012-9681-z
[16]	Espelien S, Tranell G, Safarian J (2017) Effect of magnesium addition on removal of impurities from silicon by hydrometallurgical treatment. Energy Technology 2017, Carbon Dioxide Management and Other Technologies, Springer International Publishing, 355–365.
[17]	Shimpo T, Yoshikawa T, Morita K (2004) Thermodynamic study of the effect of calcium on removal of phosphorus from molten silicon by acid leaching treatment. Metall Mater Trans B 35: 277–284. doi: 10.1007/s11663-004-0029-1
[18]	Yu ZL, Ma WH, Dai YN, et al. (2007) Removal of Iron and aluminium impurities from metallurgical grade-silicon with hydrometallurgical route. Trans Nonferrous Met Soc China 17: 1030–1033.
[19]	Jian Z, Li T, Ma X, et al. (2009) Optimization of the acid leaching process by using ultrasonic field for metallurgical grade silicon. J Semiconductors 30: 22–27.
[20]	Juneja JM, Mukherjee TK (1986) A study of the purification of metallurgical grade silicon. Hydrometallurgy 16: 69–75. doi: 10.1016/0304-386X(86)90052-6
[21]	Inoue G, Yoshikawa T, Morita K (2003) Effect of calcium on thermodynamic properties of boron in molten silicon. High Temp Mat Proc 22: 221–226.

Reader Comments

Your name:*

Email:*
© 2017 the Author(s), licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0)