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Recycling diamond wire sawing silicon powders (DWSSP) from photovoltaic (PV) silicon wafers production has become an urgent problem. The challenge of recovery is the surface oxidation and contamination of the ultra-fine powder with impurities during the sawing and collection process. In this study, a clean recovery strategy of Na 2 CO 3 -assisted sintering and acid leaching was proposed. Due to the Al contamination from the perlite filter aid, the introduced Na 2 CO 3 sintering aid can react with the SiO 2 shell of DWSSP to form a slag phase with accumulated impurity Al during the pressure-less sintering process. Meanwhile, the evaporation of CO 2 contributed to the formation of ring-like pores surrounded by a slag phase, which can be easily removed by acid leaching. When 15 % Na 2 CO 3 was added, the content of impurity Al in DWSSP could be reduced to 0.07 ppm with a removal rate of 99.9 % after acid leaching. The mechanism suggested that the addition of Na 2 CO 3 can trigger the liquid phase sintering (LPS) process of the powders, and the cohesive force and liquid pressures difference generated during the process facilitated the transportation of impurity Al from the SiO 2 shell of DWSSP to the formed liquid slag phase. The efficient silicon recovery and impurity removal of this strategy demonstrated its potential for solid waste resource utilization in the PV industry., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

[Display omitted] • The preparation mechanism of P-SiNPs/Ag@C was discussed in detail. • Anode materials derived from deposited silicon waste toward LiBs. • Electrochemical performance of P-SiNPs/Ag@C anode was investigated. 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−1 at 0.2 A g−1 after 50 cycles) and outstanding rate performance (1099 mAh·g−1 at 2 A g−1). When the current density at 1 A g−1, the specific capacity still maintains at 706 mAh·g−1 over 300 cycles. The superiority of the prepared P-SiNPs/Ag@C structures was further confirmed by Comsol Multiphysics software. Impressively, the synthesis route provides a novel avenue for value-added utilization of residual silicon waste resources from EB refining silicon and the preparation of high-performance lithium battery silicon-based anode. [ABSTRACT FROM AUTHOR]

[Display omitted] • Si/SiOx@ZnO@C anode with excellent cycling stability is synthesized from waste silicon. • The fabrication process of Si/SiOx@ZnO@C is discussed in detail. • The addition of zinc oxide and carbon improves the structure stability and transport of Li+ of the electrode. • Excellent electrochemical performance of Si/SiOx@ZnO@C anode is investigated. Silicon anode is deemed to be one of the most promising anode materials and has attracted wide attention from all walks of life. However, its commercial application is severely limited owing to the high cost, serious volume expansion, and poor electrical conductivity. Herein, Si/SiOx nanoparticles were successfully prepared by sand milling the low-cost volatile deposited silicon waste from electron beam refining polycrystalline silicon. Furthermore, the atomic layer deposited (ALD) zine oxide on Si/SiOx nanoparticles enhances the integrity of the electrode structure and provides a steady solid electrolyte layer (SEI). The outer layer is wrapped by a uniform carbon shell to restrict the volume expansion and boost the conductivity of the electrode during lithiation/delithiation. Impressively, lithium-ion batteries (LIBs) employing the Si/SiOx@ZnO@C anodes display excellent rate performance (up to 844.48 mAh g−1 at 2 A g−1) and cycle stability (912.7 mAh g−1 at 1A g−1 over 50 cycles). Moreover, the Si/SiOx@ZnO@C electrode exhibits high initial coulombic efficiency (76.8 %) and the reversible specific capacity maintains at 846 mAh g−1 over 200 cycles with a current density at 0.5 A g−1. The improvement is ascribed to the synergistic effect of triple-protected layer that effectively enhances the stability of SEI and the conductivity of the electrode. This work not only opens a novel and economic strategy for the manufacture of high-performance silicon-based anode but also furnishes an original approach for recycling and resource utilization of silicon waste. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recycling environmentally hazardous SPW into industry raw material. • Removing the oxide layer of SPW by economically-attractive vacuum sintering. • Na 3 AlF 6 -enhanced slag refining exhibited a larger reaction interface. • A smoother remove pathway of BO 3 3 - was created. • The removal rate of impurity boron has increased by 40.92%. Recycling of environmentally hazardous silicon powder waste (SPW) is conducive to achieving "carbon neutrality". However, the high-cost and low-efficiency impurity removal limit the industrial recovery of SPW. Herein, a combination strategy of vacuum sintering and Na 3 AlF 6 -enhanced slag refining is demonstrated to upgrade the traditional recycling process. The cost-effective vacuum sintering can remove 89.44% of oxygen in silicon waste, indicating that the oxide layer of SPW is removed effectively. In the Na 3 AlF 6 -enhanced CaO–SiO 2 slag, the optimal Na 3 AlF 6 content and CaO/SiO 2 mass ratio are set to 20 wt% and 1.6 based on thermodynamic simulation. Na 3 AlF 6 reduces the liquidus temperature and increases the interfacial tension of the slag system. Moreover, in Na 3 AlF 6 -containing slag, the diffusion pathway of BO 3 3 - is dredged. As a result, the silicon-slag interface is adjusted from a half-spherical to a cylindrical surface, and the interface area has increased by 14.69%. The boron removal rate by Na 3 AlF 6 -strengthened slag refining is 40.92% faster than that of traditional slag. This work improves the removal efficiency of key impurity boron, reducing the cost of SPW recovery. Based on economic evaluation, this strategy offers a commercially available way to achieve the high-value recycling of silicon waste. [ABSTRACT FROM AUTHOR]

The surface oxide layer (SiO 2 layer) is still one of the main limitations of the recovery and purification of silicon kerf waste (SKW). Herein, to recycle SKW as the low-boron silicon ingot, an effective combination strategy that digests the surface oxide layer by pretreatment and then removes impurity boron by slag treatment is proposed. In the pretreatment part, the surface oxide layer of SKW was successfully digested into a liquid phase after mixing 10.5 wt% cryolite and sintering at 1400 °C, and the obtained SKW-ceramic has a dense structure. Moreover, when holding at 1400 °C for 2 h, the boron concentration in SKW-ceramic was decreased to 5.75 ppmw, and the removal rate reaches 14.18%. In the slag treatment part, CaO and SiO 2 are selected as slag agents. The CaO/SiO 2 mass ratio and reaction temperature were determined to be 2 and 1600 °C based on thermodynamic simulation. Besides, Na 2 O formed due to the dissociation of cryolite, which can enhance the oxygen ion activity and boron-absorbing capacity of the slag. The experimental result exhibited that the boron removal efficiency reached 86.56%. The simplicity and scalability of this strategy provide a better alternative for the recovery of SKW. [Display omitted] • Hazardous silicon kerf waste is recycled into a useful low-boron silicon ingot. • Mixing cryolite to digest SiO 2 surface layer of silicon kerf waste. • SKW-ceramic sintering can remove impurity boron to a certain extent. • The formed Na 2 O enhanced the boron-absorbing and boron-holding of the slag. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mixing sintering aids to digest SiO 2 surface-layer of silicon kerf waste. • The addition range of sintering aids was designed by thermodynamic simulation. • The emerged liquid slag phase has a positive effect on the separation of B. • After a few sintering aids mixed, the removal efficiency of B reached 45.32%. • The mechanism of removing B in silicon kerf waste was discussed in detail. Removing the SiO 2 surface-layer and impurity boron in diamond wire saw silicon powder waste (DWSSP) are two difficulties in the field of photovoltaic waste recycling. Aiming at the two difficulties, this paper proposes a method of mixing sintering aids to digest the SiO 2 layer and remove impurity boron. Firstly, sintering aids Al 2 O 3 and CaO were mixed into DWSSP, and DWSSP-ceramics were prepared by pressure-less sintering. The mixed sintering aids reacted with the SiO 2 surface-layer of DWSSP, and the formed liquid slag phase plays a role in promoting the densification of DWSSP-ceramics (the relative density reached 85.97% when sintered at 1300 °C). Secondly, to obtain low-boron silicon, the slag phase was separated from DWSSP-ceramics by smelting treatment. The results showed that an optimal boron removal effect of 45.32% was reached after only 10.11 wt% sintering aids were mixed into DWSSP. The mechanism that the liquid slag phase gathered impurity boron during the sintering process, and then promoted boron to remove from silicon was reasonably deduced. The method of mixing sintering aids to remove the SiO 2 surface-layer and impurity boron provides a novel insight into purification and recovery of DWSSP. [ABSTRACT FROM AUTHOR]

• Ti and Ca were introduced as trappers of P in Cu-alloyed MG-Si. • The effects of trapper on the segregation behavior of P were discussed. • The difficulty about the removal of P-enriched phases by aqua regia was studied. • The mechanism of P removal was investigated. 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 TiSi 2 and CaCu 2 Si 2 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. [ABSTRACT FROM AUTHOR]