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Owing to the rapid advancement of the photovoltaic industry, a lot of photovoltaic (PV) silicon waste will be generated. Thus, the recycling and reuse of waste silicon have become particularly important, both for environmental remediation and economic benefits. In this work, a special structure of porous Si nanoparticles embedded nano-Ag and coated carbon layer (P-SiNPs/Ag@C) was produced by silver-assisted chemical etching (Ag-ACE) the deposited silicon waste. The special porous structure and carbon layer coating can effectively address the volume expansion issues during charge/discharge. The intercalated Ag nanoparticles greatly reduced the transfer impedance and enhanced the electrical conductivity of the anode material. As a result, the novel-designed P-SiNPs/Ag@C anode can maintain a prominent reversible capacity (1521 mAh·g

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 sin...

Environmentally harmful silicon cutting waste (SCW) generated during the production of silicon solar cells possesses a high reuse value. However, the presence of oxide surface and impurities restrict the Si-cores reuse. Herein, inspired by the structure and composition of SCW, designed a combined process consisting of vacuum sintering and alloying to reuse SCW into Al-Si alloy at a low cost. Vacuum sintering promotes the reduction of the oxide surface by Si-core. Oxygen content was decreased by 92.54 %, demonstrating the successful removal of the oxide surface. The discharge of reduction products contributes to the densification, and the Si-core has converged into dense Vac-ceramic (Si block), rendering a relative density of 96.17 %. More importantly, during the alloying process, the formation of Vac-ceramic dredges the mass transfer pathway from Si-core to Al melt. As a result, the Si utilization rate increased about seven times compared with the direct reuse of pristine SCW. Compared with commercial Al-Si alloys, the Al-Si alloys prepared by reusing silicon cutting waste in this work have satisfactory mechanical properties. The method has the prominent advantages of being protective-atmosphere-free, additive-free, and scalability, and may be a promising candidate for the silicon cutting waste purifying and reusing field.

Titanium (Ti) and calcium (Ca), as trappers, were introduced into copper-alloyed metallurgical grade silicon (MG-Si). The effects of trappers on the segregation behavior and removal efficiency of phosphorus (P) were investigated. It was found that P tended to enrich in the TiSi2 and CaCu2Si2 phases, and quenching above the eutectic temperature of Si-Cu alloy is conducive to the P removal. The corrosion process of the P-enriched phases indicated that Ca addition was in favour of P removal, while Ti addition was opposite. The results suggested that though the addition of Ti and Ca could effectively enrich P in the Si-Cu alloy, the acid sensitivity of P-enriched phases would affect the P removal.

In this study, vanadium (V) was employed as an impurity trapper for purification of metallurgical-grade silicon (MG-Si). The effect of V addition on the microstructural evolution, etching behavior, and impurities removal of MG-Si were investigated. It was found that Si2V and Si-Al-Fe-V phases were formed in the Si-5 wt%V alloy. The etching behavior of Si-V alloy was studied through the in-situ etching method and Eh-pH diagrams for Si-V-N/Cl/F-H2O system. The results showed that the V addition increases the difficulty of acid etching of the precipitated phases in MG-Si due to the low acid sensitivity of Si2V phase, and the HCl+HF mixture was effective for the elimination of precipitated phases in Si-V alloy. Compared to the directly acid leaching of MG-Si, the enhanced-effect of V addition on removal efficiencies of impurities Fe, Al, Ca, Ti, Cr, and B was confirmed. Notably, the removal efficiency of B was increased from 22.78% to 53.16%, mainly attributing to the formation of VB2 by V addition. This study is intended to provide an alternative candidate of impurity trapper for the purification of MG-Si.

Silicon kerf waste from diamond-wire sawing of solar grade silicon is regarded as a promising resource for the clean production of high-purity silicon. In this study, silicon kerf waste is collected by a two-step sintering method (TSS) to obtain a ceramic product for the first time and its effect on the leaching behavior of silicon kerf was assessed. The results show that the relative density and grain size of silicon kerf ceramic could reach 91.72% and 0.75 μm under TSS3-10 h condition (1400 °C in the first stage and 1350 °C for 10 h in the second stage). The TSS process is confirmed to be beneficial for decomposing silicon oxide layer and promoting densification. Acid leaching experiment was conducted and the relationship between the relative density and impurity extraction was evaluated. It was found that the removal rate of impurities (except oxygen) from silicon kerf by direct acid leaching was higher than that through TSS3-10 h and acid leaching. However, the combined process can reduce 52.4% oxygen content and the yield of silicon was reached 96.03%. The present study aims to shed light on the feasible application of TSS on the hydrometallurgical recycling of silicon kerf.

A combined purification process of Si-Al-Ca solvent refining and CaO-CaF2 slag treatment was investigated with a focus on removing phosphorus (P) from metallurgical-grade Si (MG-Si). The primary precipitates in the slag-treated Si-Al-Ca alloy are CaAl2Si2 and CaSi2, and these precipitates can be eliminated via leaching with HCl + CH3COOH and HCl + HF in sequence. Compared to MG-Si, a higher extraction efficiency of P was achieved with Si-Al-Ca alloy after CaO-CaF2 slag treatment. Influences of alloy composition, slag components, and operation parameter on the P removal efficiency were studied systematically. The optimal dephosphorization efficiency reached 98.6% when the 70%Si-Al-Ca alloy was treated with 20%CaO–80%CaF2 slag twice. Furthermore, the mechanism of P removal using the combined process was studied. The results indicate that the Si-Al-Ca solvent refining causes the segregation coefficient of P to be lower, thus facilitating its mass transfer in slag treatment. A large amount of P was reduced and then diffused to the slag phase in the slag experiment. Residual P in the slag-treated alloy was trapped by the CaAl2Si2 phase and was then removed via acid leaching.