Occurrence State and Dissolution Mechanism of Metallic Impurities in Diamond Wire Saw Silicon Powder

Abstract

The facilitation of metallic impurities removal via acid leaching pretreatment plays a key role in silicon recovery from diamond wire saw silicon powder (DWSSP) waste. Disappointingly, the occurrence state and dissolution mechanism of the metallic impurities present in DWSSP have not yet been revealed. For this reason, in this study, three different kinds of raw DWSSP were used for acid leaching tests and leaching behavior verification to investigate the dissolution mechanism. After two-stage acid leaching with 4 M HCl and 2 M HCl + 2.5 M HF, the results indicate that the removal efficiency was superior to that of other previously reported leaching processes. Furthermore, two occurrence states of metallic impurities present in DWSSP were defined based on their different dissolution behaviors, and the intrinsic relationship between dissolution behavior and the thinning process of the amorphous SiO2 shell was derived. The findings indicate that the first type of impurity was more easily dissolved in HCl solution; however, the second type of retained metallic impurity was restricted by the SiO2 shell barrier and was removed by the added HF solution. For this reason, the disintegration dissolution of the amorphous SiO2 shell was found to have a significant impact on the facilitation of the removal of impurities retained in DWSSP. The findings of this study are significant for the recovery of silicon from DWSSP with an effective acid leaching flow design.

Application of Pressure-less Sintering and Dynamic-Slag Treatment to Recover Diamond Wire Saw Silicon Powder

“…Various research had been carried out to find ways to recover silicon from DWSSP. The proposed disposal methods included acid leaching method to remove metallic impurities in DWSSP, − the two-stage thermal plasma process to recycle silicon from DWSSP, the vacuum carbothermal reduction and hydrobromination reaction method to eliminate silicon oxide, , the furnace aerosol method to remove the carbon contamination, and the slag treatment process for silicon recycling. , These previous works mainly focused on silicon recycling and purification and had already achieved remarkable results. Nevertheless, the impurities in DWSSP, especially boron, can affect the power generation efficiency of the photovoltaic industry − and should be further removed.…”