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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Current recycling strategies applied to photovoltaic (PV) modules have not yet solved the issue of effectively reusing and reconditioning their active part, namely the solar cells. This paper presents first results in the research carried out within the RESILIENS project to develop a cost-effective and environmentally meaningful technological recycling process for silicon solar cells that allows the recovery and reutilization of silicon and precious metals. On the one hand, demetallization of two different silicon solar cell technologies has been successfully realized via an alkaline route, optimizing process conditions. On the other hand, fragments of old silicon wafers have been successfully recrystallized, and the resulting wafers show resistivities and charge carrier lifetimes after a phosphorus diffusion gettering compatible with further high efficiency solar cell processing.

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Abstract Solar energy is currently one of the most promising clean energy sources and the use of solar energy has led to a rapid increase in the number of solar cells. As one of the fastest-growing electronic wastes, the resource treatment of solar cells at the end of their life should not be neglected. This review discusses the trend for the market development of crystalline-silicon solar cells and analyzes their physical structure and composition. It also discusses the current domestic and international recycling technologies for crystalline-silicon solar cells, including manual dismantling, inorganic acid dissolution, the combination of heat-treatment and chemical methods, and organic solvent dissolution. The shortcomings of the above treatment methods are discussed and some views on the recycling of waste crystalline-silicon solar cells are presented. Constructive suggestions for the green and sustainable development of crystalline-silicon solar cells are put forward by comparing different treatment-recycling processes.

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This paper presents an eco-friendly approach for reducing chemical solutions in the chemical process of recovering silicon from a silicon solar cell separated from a waste solar panel. Methanesulfonic acid or laser ablation was used to remove Ag metal electrodes instead of nitric acid. These processes can reduce the use of chemical acid solutions by 50% in our reference process consisting of nitric acid and hydrochloric acid. The purity of the recovered silicon powder measured by inductively coupled plasma atomic emission spectroscopy was more than 99.99% (4N). The feasibility of anode material for secondary batteries was tested by manufacturing recycled silicon powder and SiC powder using the recovered silicon. When the recovered silicon powder and high-purity silicon powder were mixed with the SiC powder, the initial capacity was 1256 mAh/g.

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Perovskitesilicon tandem cells have shown much higher efficiencies than single-junction cells, which promises further reduction of energy cost from photovoltaics. Due to the protection by perovskites, silicon subcells in perovskitesilicon tandem cells may last much longer than those in single-junction devices. Herein, we report recycling silicon bottom cells from end-of-life perovskitesilicon tandem solar cells, which further reduces their cost and enhances the sustainability. We demonstrate that silicon bottom cells can be recycled from end-of-life tandem cells by thermal delamination and chemical cleaning processes. The optoelectronic properties of silicon bottom cells were shown to be largely unchanged in the end-of-life tandem cells. The efficiencies of tandem cells refurbished from recycled silicon bottom cells are comparable to those fabricated from fresh cells.

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Conventional recycling methods to separate pure silicon from photovoltaic cells rely on complete dissolution of metals like silver and aluminium and the recovery of insoluble silicon by employing multiple leaching reagents. A common approach that eschews hydrofluoric acid (HF) treatment is the double reagent approach which utilizes nitric acid (HNO3) and potassium hydroxide (KOH) to separate the metals from silicon cell. However, the double reagent approach is unable to remove the anti-reflective coating and use of KOH leads to formation of insoluble precipitates, in turn affecting the purity of recovered silicon. Herein, we report a single reagent approach for a streamlined process for recovery of high purity silicon with unmatched recovery yield. Phosphoric acid, (H3PO4) identified as a reagent for this approach, directly targets the anti-reflective coating and separates the Ag and Al present on the Si wafer surfaces. This approach led to an impressive recovery rate of 98.9% with a high purity of 99.2%, as determined by X-ray fluorescence and Inductively-coupled plasma optical emis... Read More

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Large amounts of silicon kerf waste (SKW) and photovoltaic (PV) glass waste are being generated as the PV industry grows. At present, independent approaches have been adopted to recycle these waste materials. In this work, an original approach was first proposed for recycling silicon by using PV glass particles (PVGPs) that refine SKW. Compared with the experiment wherein no PVGPs were added, silicon yield increased from 51.44% to 87.66%. Furthermore, the transfer of the SiO2 surface-layer and the separation of silicon from slag were realized with different phase affinities. Moreover, network breakers, such as Ca2+ and F, in PVGPs destroyed the network structure of SiO2 and provided a favorable microenvironment for silicon separation. This work innovatively used PV glass waste to refine SKW. It is expected to provide a green cleaning solution for the circular development of the PV industry.

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Silicon and its usage in photovoltaics and advanced Li-ion traction batteries is a key material for the decarbonisation of the energy and mobility sector. To achieve sustainable silicon-based products, an efficient raw material processing is required. However, the production of silicon and its purification is energy- and resource intensive. Further, during the production of photovoltaic cells, about 40% of the silicon used is lost as sawdust, the so-called silicon kerf, which is often not recycled to a high quality. Compared to primary production, silicon recycling requires less electrical energy and no fossil reductants. However, an environmental assessment of the GHG reduction potential of silicon kerf recycling in comparison to primary production of silicon is limited in literature. In this paper, we will provide a comprehensive environmental assessment of silicon kerf recycling located in Sichuan and Xinjiang in China and Germany, since China is the biggest producer of silicon worldwide. For the assessment of the recycling, a detailed process-specific material and energy flow bal... Read More

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Silicon solar modules are only 1015 wt% circular with today's recycling technologies. A 90 wt% circularity requires that all the inorganic materials in silicon modules be recovered for reuse in solar or similar applications. Major technical barriers to a 90 wt% circularity for silicon modules include: 1) removal of the fluoropolymer back sheet; 2) detachment of silicon cells from glass; 3) removal of the encapsulant on silicon cells; and 4) mild chemistry and minimization of chemical waste along with high material recovery rates. Noticeable progress in recycling technologies in the last few years includes: 1) mechanical milling to remove the fluoropolymer back sheet; 2) laser debonding of the encapsulant from silicon cells; 3) dissolution of the encapsulant with a base; 4) mild chemistry for silver and lead recovery; and 5) regenerative chemistry to reuse some of the chemicals in silicon cell recycling.

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With the strengthened awareness of environmental protection and the growing interests of wastes recycling, silicon recovery from polycrystalline silicon kerf loss (PSKL) has drawn extensive attentions all over the world. In this paper, an efficient and environmental friendly approach for oxygen removal and silicon recovery from PSKL by combining vacuum magnesium thermal reduction (VMTR) and hydrochloric acid leaching was proposed. The effects of temperature, duration and particle size on the reduction of PSKL were investigated thoroughly. It is proved that the amorphous SiO2 in PSKL can be reduced by magnesium vapor at 923 K to generate MgO, and then the produced MgO can be dissolved by hydrochloric acid to eliminate the impurity oxygen. The oxygen removal fraction and the silicon recovery efficiency attained 98.43% and 94.46%, respectively, under the optimal conditions, indicating that a high efficiency recovery of silicon from PSKL was achieved. Compared to the existing PSKL deoxidation technologies, e.g., the high temperature process and the hydrofluoric acid leaching method, this... Read More

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The high rate of PV adaptation around the world requires a strategy for recovery of the materials from PV waste panels and a circular market development. In particular, the silicon recovered from the PV cells can be used in different applications. A valuable acquisition is to refine the recovered silicon at metallurgical grade to a high level of purity namely electronic grade silicon which in conjunction with graphite can be the raw material for silicon carbide crystal production. Based on a comprehensive and critical review of the latest research and development of relevant technologies, a manufacturing process is proposed to increase the usage of renewable resources, reduce the energy consumption and CO2e emissions. The recovered silicon from recycling PV waste can reduce the CO2e emissions to a third of what is involved in the current carbothermic reduction of quartz in an induction furnace. Based upon the thorough evaluation of available evidence, a continuous coupled process is envisaged where the upgraded metallurgical grade silicon from recycling PV waste undergoes further vac... Read More

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Considering the boom of Si solar cell installation, it is necessary to establish a process for recycling of Si from End-of-life photovoltaics (PVs). Silicon in the PVs is synthetically doped and coated by various elements and hence dedicated methods will be required for recycling of Si, back to the SoG-Si. In this research, recycling of Si from the shredded solar cells is studied by means of vacuum refining process. In this research the rejected solar cells after the firing step are treated by acid etching techniques to remove the Al back layer and the Ag finger on the front side of the cells, providing a product called de-metallized Si fragments. The vacuum refining experiments were carried out on demetallized Si fragments. Results showed the demetallized Si contained presence of P (11.67 ppmw), B (1 ppmw), Ca with up to 0.28 wt%, Ag (96 ppmw) and Sn (136 ppmw), while other metallic impurities were lower. We have shown that Sn, Ag, O, N, and Mg can be removed from the Si melt via short vacuum refining, while a complete removal of Ca and P required longer times compared to the mentio... Read More

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The post-processing and recycling of silicon cutting scraps in PV industry is of great importance both in environmental remediation and from an economic perspective. In this work, a novel organic-inorganic composite was synthesized by three-step surface modification of nanoporous silicon (NPSi) powder that was etched with Ag-assisted chemically of kerf loss silicon waste, which showed high-effective extraction of Pb in industrial effluents. The factors that have a decisive influence on its absorption performance, such as original pH value, absorption saturation time, and original concentration of PbII, are studied in detail. The produced adsorbent has a maximum adsorption capacity of 253.3 mg/g for PbII at the ideal circumstances of pH = 6, t = 10 min, and C0 = 300 mg/L. Both the Langmuir isotherm and the pseudo-second-order model exhibit favorable agreement with the adsorption process. In addition, the adsorption mechanism is dominated by chemical chelation and ion exchange reactions between silanol groups and PbII. The EDA-CC-APTES-NPSi still held fantabulous adsorption capacity e... Read More

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The increased manufacturing of silicon heterojunction (SHJ) solar cells/panels has generated a significant rise in production waste, which contains valuable materials like indium, silver and silicon. With a high demand for these raw materials, the recovery of waste solar cells has become a crucial undertaking. While various methodologies have been explored for recycling crystalline silicon cells and leading to significant benefits through the recovery of valuable materials, a comprehensive and validated recovery process for SHJ solar cells is still lacking. This paper investigates the potential use of benign hydrometallurgical conditions for recovering valuable materials and maximizing the resource purification of metal indium from production waste SHJ cells. The results demonstrate that complete recovery of silver grids can be achieved through 10% NaOH etching at 90 for 10 min due to their low adhesion properties with the transparent conductive oxide layer. Furthermore, optimal chemical treatment conditions were adjusted to achieve efficient leaching recovery of indium. Consequent... Read More

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The photovoltaic industry is developing rapidly to support the net-zero energy transition. Among various photovoltaic technologies, silicon-based technology is the most advanced, commanding a staggering 95% market share. However, the energy-intensive process of manufacturing silicon wafer raises concerns. In the photovoltaic supply chain, a substantial amount of photovoltaic secondary silicon-containing resource (PV-SSCR), including metallurgical-grade silicon refined slag (MGSRS), silicon fume (SF), silicon cutting waste (SCW) and end-of-life silicon solar cell (ESSC) from discharged modules, can be recycled. Recycling holds the potential to enhance economic value and reduce the overall environmental impacts associated with the lifecycle of silicon photovoltaics. This article offers a comprehensive overview of techniques and applications of four kinds of PV-SSCR: MGSRS, SF, SCW, and ESSC. Moreover, it also highlights challenges and opportunities for further research and development in this field.

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Silicones are ubiquitous materials owing to their exceptional mechanical and thermal stability as well as low toxicity. Recycling them has become a seducing target for Circular Economy purposes. Conventional chemical recycling processes of polysiloxanes allow for the recovery of valuable cyclic monomers. Unfortunately, they lack efficiency and still require high operating temperatures thus yielding detrimental by-products. We introduce an efficient method for the solvent-free depolymerisation of linear polydimethylsiloxanes using a [polydentate ligand-silanolate] complex as a catalyst, that promote chemical recycling of silicones into cyclic monomers from many industrial substrates including actual waste materials. Our method only requires a small amount of catalyst (0.1 mol%) and proceeds over a wide range of temperature (60C-170C) to efficiently yield of a mixture of cyclosiloxanes (up to 98-99% yield) from up to a 100g scale of waste silicone oils. Moreover, the recyclability of this catalyst was demonstrated over five runs without loss of activity.

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Photovoltaic panel waste is expected to rise rapidly as installed modules approach their end of life. Recovery and reuse of valuable components such as semiconductors is crucial. Crystalline silicon panel derived waste reacts with alkali producing hydrogen gas and metasilicate structures in the solution which can be used as geopolymerization activator. In this work the prospect of utilizing 1st generation crystalline silicon panel waste for geopolymer activation with simultaneous hydrogen production is examined. Preliminary test results show that 1.550.05L of hydrogen gas can be produced from 1g of recovered semiconductor (Si). The resulting metasilicate solution is used for fly ash geopolymer activation. After 7 days of curing, the compressive strength of the generated geopolymer samples reached 19.50.5 MPa, indicating that this zero-waste reuse pathway can be viable after optimization.

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Silicon cutting waste (SCW) mainly consists of Si (80 ~ 85 wt%), SiO2 (13 ~ 16 wt%) and other impurities (2 ~ 4 wt%). Nowadays, the Si in SCW is commercially recycled to produce Si ingots by a slag refining method, but the SiO2 in SCW is melted into silicon slag and discarded as waste. In this paper, a carbothermal reduction method has been proposed for recycling Si resources from both Si and SiO2 in SCW to prepare high-quality silicon in a submerged arc furnace. Petroleum coke was selected as the carbonaceous reducing agent. Firstly, the effects of carbon content on the equilibrium compositions of the Si-SiO2-C system were simulated. Secondly, SCW was mixed with petroleum coke under the guidance of thermodynamic analysis results. Finally, the mixtures were charged into furnace and smelted. Thermodynamic equilibrium analysis results showed that the value of n(Si):n(C):n(SiO2) should be controlled as 2.62:0.22:0.44 theoretically. Experimental results revealed that the recovery ratio of SCW was 50% and the purity of Si products was 99.40%. This proposed method provides an effective and... Read More

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Silicon cutting waste (SCW) produced during silicon wafer producing process mainly consists of Si (8085 wt%), SiO2 (1316 wt%) and other impurities (24 wt%). In this paper, a slag refining process was proposed to recycle Si from SCW for producing high-quality silicon. CaO was used as fluxing agent to react with SiO2 for forming compounds with low melting point and viscosity during recycling process. The influences of CaO addition amount and refining time on recovery ratio of SCW and purity of Si products were investigated. Under the optimized conditions of a CaO addition amount of 8 wt% and a refining time of 50 min, the recovery ratio of SCW and the purity of Si products can achieve 59.59% and 99.56%, respectively, in laboratory-scale experiments. The separation mechanism of Si from SCW is that the external SiO2 film is digested by CaO, and then the internal Si is exposed and melted into liquid Si. This method was successfully applied for recycling Si from SCW in industrial-scale and the recovery ratio of SCW can reach 60%. Economical evaluation shows that this method can bring en... Read More

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Silicon powder kerf loss from diamond wire sawing in the photovoltaic wafering industry is a highly appealing source material for use in lithium-ion 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 nano-scale 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 cycling X-ray powder diffraction experiments, demonstrating that the powders are relevant for further investigation and development for battery applications.

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The proliferated growth of the Photovoltaic industry (PV) will eventually lead to unprecedented volumes of silicon-based solar waste. Failing to manage high volumes of waste, can lead to a huge amount of silicon metal loss and is also highly conducive to posing an environmental hazard. Therefore, efficient recovery and re-utilization after proper purification of the PV-waste-based silicon are highly obligatory for the sustainable development of the PV industry. Herein, we report the growth of small-size silicon ingots ( = 0.5 inch, 1.0 inch) produced from recovered silicon from the waste crystalline silicon (c-Si) solar module through the Spark Plasma Sintering (SPS) technique. The silicon feedstock was prepared, after the extraction of silicon cells from the used panel and chemically etching contacts, ARC (anti-reflection coating), from the cells in order to recover the silicon wafer. The silicon wafer pieces were pulverized to produce very fine powder and subsequently processed at a different set of temperature-pressure for the study of density variation. The highest density (2.33... Read More

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Silicon is identified as the most promising anode candidate for next-generation lithium-ion batteries (LIBs). However, its application is limited by the large volume variation and high cost. In this study, the silicon powders from the kerf slurry wastes are used as raw materials for the preparation of silicon/carbon composite anodes for lithium-ion batteries. An effective pretreatment process that combines the sand milling and a chemical cleaning method is utilized to prepare the purified silicon powders. Then, a facile one-step hydrothermal method is used to prepare the purified silicon/carbon composites. The results demonstrate that the chemical purification can effectively remove the organic contaminants and metal impurities on the surface of raw silicon powders. It also renders hydrophilic surfaces for the silicon powders, which improves the bonding of carbon layer and results in the improvement of the electrical performance correspondingly. The as-prepared purified silicon/carbon anode shows a high specific discharge capacity of 2099 mAh g-1 in the first cycle at the current den... Read More

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The photovoltaic (PV) market started in 2000, and the first batch of crystalline silicon (c-Si) PV panels with a lifespan of 2030 years are about to be retired. Recycling Si in waste c-Si PV panels is critical for resource reuse and environmental preservation. Electrostatic separation is a non-polluting and low-cost technology for recovering Si from mechanical crushing products of c-Si PV panels. In this study, the waste c-Si PV panels were pretreated by mechanical crushing and the products contained two parts: the blocks and the mixed powder. Through acid washing and X-ray fluorescence tests, a mass fraction of 82.8 wt% of Si in the crushed c-Si PV waste was distributed in the mixed powder, which was recycled by electrostatic separation. The effects of particle size of the powder, voltage of the DC power supply and rotation speed of the roller on the recovery of Si were investigated. The optimum particle size for recycling Si by electrostatic separation was 0.300.45 mm, and the best separation effect was achieved at a rotation speed of 30 rpm and a voltage of 15 kV at this particl... Read More

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The rapid development of the photovoltaic (PV) industry will result in an increase in the amount of electrical and electronic waste from used PV panels. Only in Poland, the total capacity installed in photovoltaic sources in Poland in May 2020 exceeded 1,950 MW, and the installation weight was approximately 120,000. tone. The problem arises in the recycling or management of this waste. This work presents methods used to recycle waste into photovoltaic modules. The authors investigated the possibility of mechanical and chemical processing of crystalline silicon. A method of thermal treatment of the panel was also proposed. As a result of the research, it was found that the stage of separating materials (crystalline cream, EVO foil, aluminum frame) plays an important role in the recycling process, which is not easy. Chemical treatment allows the silicon to become plastic and the temperature melts the back layer of the panel.

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This work reports a cost-effective and environmentally friendly method for preparing high-quality and highly-crystalline silicon nitride (Si3N4) powders from silicon (Si) scrap through direct nitridation. With Si scrap from semiconductor manufacturing processes being a critical and imperative global issue in recent times, an efficient methodology is essentially required to recycle it. For this purpose, ball milling parameters for Si scrap were optimized using different solvents to obtain homogeneous and fine-micron sized silicon powders for efficient nitridation. Ethanol was found to be the most effective in producing the required conditions of Si powders. Direct nitridation was performed at 1450 C in an atmosphere of nitrogen and hydrogen gas flow to prepare Si3N4 powders. Various characterization techniques were used to analyze particle sizes, phase compositions, and morphologies of raw Si scrap, ball-milled Si powders, and Si3N4 powders. Results indicated that the nitridation reaction resulted in 90.1% conversion of Si into Si3N4 and the -Si3N4 phase accounted for 85% of the tot... Read More

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The present work suggests a unique approach for recovering pure silicon from end-of-life silicon solar panels by a direct treatment which does not involve the use of Hydrofluoric Acid (HF). Firstly, the better alkaline treatment between NaOH and KOH was determined. Then, effects of HF etching time and concentration were studied by comparing different etching treatments. Metal impurities such as Ag, Sn, and heavy metal Pb decreased considerably during the acid leaching studies with suitable concentrations. The major impurity Aluminium was reduced significantly by a two-step chemical treatment which ensures minimal silicon loss. Although it is possible to recover 4 N pure silicon by both (with and without HF etching) methods, direct treatment is preferred since the process eliminates potential human health and environmental concerns associated with HF. The recovered silicon samples were analysed by ICP-OES to detect impurity concentration, by XRD for phase identification and SEM analysis for surface morphology. The critical doping impurities, boron and phosphorous dropped considerably ... Read More

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The utilization of high-purity silicon (99.9999 %) is prevalent in the solar photovoltaic sector, and achieving a reduction in its cost has emerged as a pivotal engineering objective within the silicon solar industry. Recycling silicon from diamond wire saw silicon powder (DWSSP) is a promising solution to fulfill the continuously expanding of high purity silicon demand. Vacuum directional solidification technology using high-frequency electromagnetic induction heating was proposed to purify DWSSP for the first time efficiently. The silicon melt and gas interface reaction, as well as metal impurities' microsegregation in silicon ingot were observed. The effects of vacuum level and electromagnetic force on the separation of silicon and metal impurities were investigated using thermodynamics and electromagnetic mechanics. Results indicate that the content of oxygen in the silicon reduced from 30.91 wt% to 5.08 wt%, and the actual sample composition including for uptake of residual gas contamination steadily declined as the vacuum level increased from 600 Pa to 10 Pa. Vacuum electromag... Read More

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In the traditional technology of smelting technical silicon, a number of problems remain unresolved that need to be addressed. This chapter describes an integrated approach to solving existing problems, which consists in the development of new technologies for the smelting of technical silicon, which can reduce energy costs, improve product quality, and reduce the severity of environmental problems of this production. The ways of increasing the profitability of carbothermal electric arc melting of technical silicon are described by returning to the process fine wastes from the preparation of charge materials and microsilica dusty wastes from the production of silicon itself in the form of briquettes. The use of these pulverized wastes for the synthesis of liquid glass glue, in concrete and building mixtures, and for the synthesis of micro- and nanosized silicon carbide powders is also described.

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With the continuous progress of science and technology, more and more solar cells are used in the field of green power generation. Silicon solar cells, which are widely used as solar cells, dominate the solar cell market. Along with this comes a lot of waste silicon solar cells reaching the end of their useful life. In this essay, experimental data were collected by changing the time and solubility of solution at the same room temperature through the control variable method. The most efficient recovery conditions are obtained based on the existing recycle methods. This efficient recycling method can be applied to a large number of existing abandoned silicon solar cells to improve the recycling efficiency of enterprises and increase economic benefits. At the same time, it can also maintain efficient recycling and utilization of resources, reduce environmental damage and promote technological progress.

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A method for recycling diamond wire cutting silicon waste, comprising: solid-liquid separation to isolate the silicon powder; drying to remove moisture; carbonylation to remove metallic impurities; and chemical reactions to produce elemental silicon, silicon monoxide, and silicon-containing alloys. The method enables efficient recovery of high-purity silicon from waste generated during diamond wire cutting of silicon materials.

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This paper investigates the current and future projected silicon demand for the photovoltaics industry towards broad electrification scenarios with over 60 TW of PV installed by 2050. The current silicon consumption contained in cells/modules is 1510-1900 tonnes/GW. However, this does not account for silicon losses during purification, ingot growth and wafering. The global polysilicon demand by the PV industry in 2020 of 452 kt equates to a silicon consumption of approximately 3150 tonnes/GW, suggesting a current utilization factor of 48-60%. Depending on physical constraints determining the lower limit for future silicon consumption, (eg. 1550 tonnes/GW for 30% tandems made on 100 m thick wafers, with 50% silicon utilization), the cumulative silicon demand to 2050 could be in the range of 45-123 Mt, with an annual demand of 2-9 Mt in 2050. To reduce the environmental impact of silicon wafers, we must increase efficiencies, use thinner wafers, reduced kerf-loss and explore alternative purification methods with low emissions intensities.

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