Recycling Techniques for Silicon Kerf Loss

Method for removing silicon powder from a coolant used in monocrystalline silicon slicing with a diamond wire. The method involves adding an inorganic coagulation-inducing saline solution to the waste coolant, causing the silicon powder to agglomerate and precipitate. The solution is prepared by mixing calcium and magnesium salts in a specific mass ratio, and is added to the coolant in a controlled volume ratio. The mixture is then stirred at a moderate speed for a short period of time, allowing the silicon powder to settle out of the coolant. The treated coolant can be reused, and the recovered silicon powder can be recycled.

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Method for producing high-purity silicon powder from waste silicon sludge by drying the sludge to form powder, followed by heating in a reducing atmosphere to remove moisture and SiO2, thereby achieving ultra-high purity silicon powder with minimized oxygen content.

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Recycling materials from end-of-life devices and products is becoming increasingly a fundamental activity for the sustainable development of nations. With the return from the market of immense quantities of photovoltaic panels at the end of their life, it is essential to foresee processes for recovering and valorizing all the raw materials present in them to avoid wasting important flows of raw materials. This research introduces a novel process aimed at the recovery of silver and silicon from end-of-life photovoltaic panels. The leaching efficiency and kinetics of ground cake powder in sulfuric acid, ferric sulfate, and thiourea were investigated in the leaching system. In particular, the influences of significant parameters, including particle size, leaching temperature, and stirring rate, on the extraction kinetics were analyzed using the shrinking core model. The results showed silver dissolving mechanisms, in which more than 90% of silver recovery at 60 min of reaction time and 99% at 120 min was achieved (120 rpm, 53125 m, and 40 C). The significant effect of the leaching te... Read More

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The aim of this work was to study the purification of silicon kerf loss waste (KLW) by a combination of single-acid leaching followed by inductive melting at high temperatures with an addition of fluidized bed reactor (FBR) silicon granules. The KLW indicated an average particle size (D50) of approximately 1.6 m, and a BET surface area of 30.4 m2/g. Acid leaching by 1 M HCl indicated significant removal of impurities such as Ni (77%), Fe (91%) and P (75%). The combined two-stage treatment resulted in significant removal of the major impurities: Al (78%), Ni (79%), Ca (85%), P (92%) and Fe (99%). The general material loss during melting decreased with an increasing amount of FBR silicon granules which aided in the melting process and indicated better melting. It was observed that the melting behavior of the samples improved as the temperature increased, with complete melting being observed throughout the crucibles at the highest temperature (1800 C) used, even without any additives. At lower temperatures (1600 C1700 C) and lower FBR-Si (<30 wt.%) additions, the melting was inc... Read More

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As the demand for silicone polymers continues to grow across various industries, the need for effective recycling methods has become increasingly important, because recycling silicone products reduces landfill waste, conserves resources, and uses less energy. Chemical recycling involves the depolymerization of silicone waste into oligomers, which can then be used to produce virgin-grade silicone. While this sector of the recycling industry is still in its infancywe estimate that 35,000 to 45,000 metric tons of silicone waste will be chemically recycled worldwide in 2024an increasing number of companies are beginning to explore the implementation of closed-loop systems to recycle silicones. This article examines the technical options and challenges for recycling silicone polymers, the major degradation chemistries available for depolymerizing silicones, and the current industrial reality of chemical recycling of silicones.

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The recovery of massive kerf loss silicon waste into silicon anodes is an attractive approach to efficiently utilizing resources and protect the environment. Tens-of-nanometers-scale-thickness Si waste particles enable the high feasibility of high-rate Li-ion storage, but continuous oxidation leads to a gradual loss of electrochemical activity. Understanding the relationship between this oxidation and Li-ion storage properties is key to efficiently recovering silicon wastes into silicon anodes. However, corresponding research is rare. Herein, a series of silicon waste samples with different oxidation states were synthesized and their Li-ion storage characters were investigated. By analyzing their Li-ion storage properties and kinetics, we found that oxidation has absolutely detrimental effects on Li-ion storage performance, which is different to previously reported results of nano-silicon materials. The 2.5 wt.% Si provides a substantial initial discharge capacity of 3519 mAh/g at 0.5 A/g. The capacity retention of 2.5 wt.% Si is almost 70% after 500 cycles at 1 A/g. However, the 35.... Read More

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The increasing importance of recycling end-of-life photovoltaic modules is demonstrated by the rising quantity of discarded crystalline silicon solar cells that contain valuable metals. Despite advanced recycling methods, the surplus of broken Si wafers poses challenges for reintegration into new module manufacturing. The present study introduces a novel recycling process that addresses this issue and promotes sustainable waste processing, focusing on the untapped resources of Si wafer breakage and environmentally harmful red mud. The proposed method uses these two critical waste materials to enable a silicothermal reduction, yielding ferrosilicon-based alloys. To comprehensively analyze the influence of the iron oxide source on alloy composition, a readily available iron oxide pigment (Bayferrox 110) is implemented as a reference material. FeSi-based alloys containing 15 to 65 wt % Si are produced by the silicothermal reduction with soda ash as a flux, at a temperature of 1600 C. The use of Bayferrox as an iron oxide source facilitates the production of FeSi alloys that are free ... Read More

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The solid waste from solar photovoltaic (PV) systems diverges from carbon neutrality targets and the core principles of clean energy. Herein, we present an innovative and cost-effective strategy to fabricate P-SKW@C as anode materials based on the natural properties of submicron silicon kerf waste (SKW) by increasing the surface oxide layer and combining the synergistic effects of magnesium thermal and acid leaching. In particular, the carbon layer establishes channels for electron and ion transport, thereby enhancing the conductivity of P-SKW@C and the mobility of lithium ions. The formation of pores by the synergistic effects of magnesium thermal and acid leaching provides buffer space to accommodate the volume changes in silicon, ensuring the structural integrity of the electrode. Specifically, the P-SKW@C anode exhibits superior rate performance, reaching 1006 mAh g1 at 2 A g1, and an outstanding reversible capacity of 1103 mAh g1 with the current density returning to 0.2 A g1. Furthermore, the P-SKW@C anode demonstrates a remarkable specific capacity of 905 mAh g1 at 500 mA... Read More

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In this work, industrially processed silicon kerf loss (abbreviated to silicon kerf) from the photovoltaic industry is assessed as an anode material for the lithium-ion battery (LIB). The study includes both a characterization of processed silicon kerf from different sources and a comparison with commercially available nano-sized silicon (40 and 100 nm) in electrochemical testing. Such a direct comparison between these two silicon types in electrochemical testing provides a new insight into silicon kerf as an anode material. The silicon kerf particles are flake-like with varying lengths, with a mean particle size (d50) measured to 700 nm and a dimension of thickness of a few tens of nanometers. However, the specific surface area ranging from 20 to 26 m 2 /g is comparable to that of a silicon material of size 100 nm. The silicon oxide layer surrounding the particles was measured to 12 nm in thickness and, therefore, is in a suitable range for the LIB. In terms of electrochemical performance, the silicon kerf is on par with the commercial nano-sized silicon, further supporting the s... Read More

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It is imperative in the photovoltaic (PV) industry to establish a circular materials flow for more sustainable solar silicon production. In the present work, a series of K2O-SiO2 binary and K2O-CaO-SiO2 ternary slags were examined for the combination of silicon purification and Si-kerf waste recycling. The study revealed that the mass transfer mechanism of the slag composition variation is predominantly due to the silicothermic reduction of K2O. The boron removal degree achieved high level at approximately 80% in most of tests, with gasification as potassium metaborate confirmed as an important B removal mechanism, especially in slags with high K2O content. In the case of ternary slags, the results indicated that an increase in CaO enhances boron partitioning in slag phase and a high K2O content also led to boron accumulation in the slag phase due to rapid reaction kinetics. Molecular dynamics simulations reveal that calcium and potassium ions exhibit distinct behaviours in slag phase. Potassium ions preferentially modify bridging oxygen, while calcium ions contribute more to depolym... Read More

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The increasing scrapped Si-based photovoltaic (PV) panels has become an urgent problem, and their disposal is essential for resources utilization and environment issues. This paper proposes a comprehensive process for recycling of discarded silicon-based PV panels economically, environmentally, and efficiently. Based on the thermal properties of ethylene vinyl acetate (EVA), they are removed from the discarded PV panels at 600 C with heating rate of 5 C/min and maintain for one hour. The glass, solar cells, and copper strips were separated after heat treatment. Simultaneously, the solar cells were crushed into powder. Nitric acid was used to recover silver from the solar cell powder, while most of the metal impurities such as Mg, Ti and Al, were removed as well. The leaching efficiency of silver was over 96 % under the optimized conditions: HNO3 of 4.0 mol/L, liquid-to-solid ratio of 10:1, temperature of 50 C for 80 min. Regarding the copper strips, they were sequentially treated with 0.5 mol/L CH3COOH and NaOH solution to remove the oxides of Pb and Sn on their surface. Subsequen... Read More

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Addition curing systems involve two-part silicones which require the mixture of a silicone polymer with a catalyst to initiate the cure. Platinum is the most commonly used metal catalyst for addition curing of silicones by hydrosilylation which involves the crosslinking by the addition reaction of silicon hydride species to unsaturated bonds, mainly CC, but also CO or CN double bonds. After crosslinking of the polymers, the platinum catalyst cannot be recovered but remains in the silicone materials throughout the entire product life. In the end, platinum is disposed of together with the silicones and is thus lost to the value chain. The overall objective of this work was to develop a recycling process for the recovery of platinum from addition-cured silicone elastomers. In the first step, this was achieved by efficient digestion methods and by optimizing the leaching processes for exemplary commercial silicone elastomer products. Two different silicone materials were investigated, both of which were crosslinked with a platinum catalyst. The initial Pt content in the tested samples wa... Read More

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Recycling silicon cutting waste (SCW) plays a pivotal role in reducing environmental impact and enhancing resource efficiency within the semiconductor industry. Herein SCW was utilized to prepare SiC and ultrasound-assisted leaching was investigated to purify the obtained SiC and the leaching factors were optimized. The mixed acids of HF/H

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This study examines the efficacy of photovoltaic (PV) recycling processes and technologies for the recovery of high-purity silicon powder from waste solar modules. In order to facilitate the simplification of complex processes, such as the conventional nitric acid dissolution, solvent and ultrasonic irradiation, and solvent dissolution, a variety of mechanical separation processes have been established. These processes are designed to enhance the efficiency and effectiveness of the aforementioned processes. And a novel method for separating EVA from recycled Si powder was devised, which studied the WGS process using aqueous solutions of H

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The retirement wave of photovoltaic (PV) panels is expected to result in a significant number of discarded panels in the near future. Recycling PV silicon in a rational manner will not only help reduce the environmental impact but also lead to substantial economic gains. In this study, aaste solar silicon wafers were ball-milled to obtain recycled silicon (r-Si) powder. The TiO2/r-Si carrier was prepared through a simple hydrothermal process, followed by the creation of a novel Ag3PO4/TiO2/r-Si (APO/TIO/r-Si) ternary heterojunction composite using a co-precipitation method. The photocatalytic properties of the materials doped with different concentrations of Ag3PO4 were examined using Rhodamine B (RhB) degradation rate as a performance metric. Among them, 40 %APO/TIO/r-Si heterojunction exhibits excellent photodegradation activity under visible light irradiation. The photocatalytic degradation efficiency reached 93.0 % in 30 min, with a removal rate of 82.8 % after 5 cycles. It was found that superoxide radicals and hydroxyl radicals are the main drivers of RhB photodecomposition. Th... Read More

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The increasing adoption of crystalline silicon solar cells as a renewable energy solution has led to a growing concern regarding the proper management of end-of-life photovoltaic modules. This paper presents a comprehensive analysis of chemical processes for the recycling of crystalline solar cells, focusing on state-of-the-art technologies. The recycling of crystalline silicon cells by the chemical process where we identified that the chemical process for extracting silicon from PV modules is considerably more effective than all other techniques and technologies. A comparative analysis is made from all the chemical processes containing chemical compositions with a greater extraction of silicon. The results show that the significance of the chemical processes not only depends on the chemical element but also depends on the temperature. Besides a comprehensive assessment is done to address the growing challenges associated with end-of-life solar modules.

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A process for recycling silicon carbide (SiC) waste into high-purity powders. The process involves cutting and pulverizing the waste SiC, followed by graphite removal, iron component removal, and cleaning steps. The resulting powders have a purity of 95-99.9999% and contain impurities at levels of 1 ppm or less.

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Abstract Silicon powder kerf loss from diamond wire sawing in the photovoltaic wafering industry is a highly appealing source material for use in lithiumion battery negative electrodes. Here, it is demonstrated for the first time that the kerf particles from three independent sources contain ~50 % amorphous silicon. The crystalline phase is in the shape of nanoscale crystalline inclusions in an amorphous matrix. From literature on wafering technology looking at wafer quality, the origin and mechanisms responsible for the amorphous content in the kerf loss powder are explained. In order to better understand for which applications the material could be a valuable raw material, the amorphicity and other relevant features are thoroughly investigated by a large amount of experimental methods. Furthermore, the kerf powder was crystallized and compared to the partly amorphous sample by operando Xray powder diffraction experiments during battery cycling, demonstrating that the powders are relevant for further investigation and development for battery applications.

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It is of great significance to recycle the silicon (Si) kerf slurry waste from the photovoltaic (PV) industry. Si holds great promise as the anode material for Li-ion batteries (LIBs) due to its high theoretical capacity. However, the large volume expansion of Si during the electrochemical processes always leads to electrode collapse and a rapid decline in electrochemical performance. Herein, an effective carbon coating strategy is utilized to construct a precise Si@CPPy composite using cutting-waste silicon and polypyrrole (PPy). By optimizing the mass ratio of Si and carbon, the Si@CPPy composite can exhibit a high specific capacity and superior rate capability (1436 mAh g-1 at 0.1 A g-1 and 607 mAh g-1 at 1.0 A g-1). Moreover, the Si@CPPy composite also shows better cycling stability than the pristine prescreen silicon (PS-Si), as the carbon coating can effectively alleviate the volume expansion of Si during the lithiation/delithiation process. This work showcases a high-value utilization of PV silicon scraps, which helps to reduce resource waste and develop green energy storage.

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Silicon is considered to have significant potential for anode materials in lithiumion batteries (LIBs) with a theoretical specific capacity of 4200 mAh g1. However, the development of commercial applications is impacted by the volume shift that happens in silicon when charging and discharging. In this paper, a yolkshellstructured Si@void@C anode material has been developed to address this problem. The silicon nanoparticle yolk material is obtained by recycling kerf loss (KL) Si waste from the process of slicing silicon block casts into wafers in the photovoltaic industry; the carbon shell is prepared by a hydrothermal method with glucose, and the sacrificial interlayer is Al2O3. The produced material is employed in the production of anodes, exhibiting a reversible capacity of 836 mAh g1 at 0.1 A g1 after 100 cycles, accompanied by a Coulomb efficiency of 71.4%. This study demonstrates an economical way of transforming KL Si waste into materials with an enhanced value for LIBs.

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