Study on the kinetics of iron removal from silicon diamond-wire saw cutting waste: Comparison between heterogeneous and homogeneous reaction methods

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.

Section: Introductionsupporting

confidence: 89%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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

Yang

Wan

Wei

et al. 2020

“…For diamond wire sawing, the cutting wire is coated with diamond particles, resulting in less impurities and higher wafer quality. Therefore, the latter has become the promising method for slicing silicon wafers. − …”

Section: Introductionmentioning

confidence: 99%

Preparation of Low-Boron Silicon from Diamond Wire Sawing Waste by Pressure-Less Sintering and CaO–SiO₂ Slag Treatment

Zhang

Wang

Huang

et al. 2020

Self Cite

In order to recover silicon from diamond wire sawing waste, silicon extraction and boron removal are two key issues that need to be addressed. In this study, a combined process of pressure-less sintering and CaO−SiO 2 slag treatment was proposed. Low -boron silicon was prepared and considered as raw materials in solar cell production. The results confirmed that pressure-less sintering was beneficial for the digestion of the silicon oxide layer, and the molar percentage of oxygen in silicon kerf was reduced from 14.83 to 7.24% after pressure-less sintering at 1400 °C for 2 h. The effect of slag composition on boron removal was investigated. It was found that an optimum boron removal efficiency of 86.91% was obtained when the optical basicity reached 0.68 and no CaF 2 was added; the CaO−SiO 2 mass ratio was 1.2, the holding time was 40 min, and the slag to silicon mass ratio was 1. Although the addition of CaF 2 can decrease the viscosity, it affects the activity and the oxygen potential of slag.

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Chen

Wang

Huang

et al. 2020

Self Cite

Recycling silicon from environmentally hazardous diamond wire saw silicon powder waste (DWSSP) and effectively removing boron is still an elusive aim. Here, pressure-less sintering and dynamic-slag treatment were used to recover the powder waste. On the basis of thermodynamic simulation, the slag composition was designed. Dense structure of DWSSP ceramics could effectively reduce the oxidation loss. Dynamic-slag treatment can provide higher silicon recovery and better boron removal rate than can traditional one-step slag treatment. Slag-1 (Na 2 O-SiO 2 ) can remove boron while protecting molten silicon from oxidation. Interestingly, after Slag-2 (CaO−SiO 2 −Na 2 O) was added, relative displacement between the mixed slag and silicon can provide more favorable dynamic conditions. Using the dynamic-slag treatment, the boron removal efficiency reached 83.4%, and the silicon recovery rate reached 82.29%. Additionally, by introducing the solute penetration theory, the mechanism of boron removal during convective mass transfer process was discussed in detail. The simplicity of this combined approach provides a new possibility for recovery and purification of intractable fine powdery waste.