METHOD FOR RECYCLING PHOTOVOLTAIC MODULES

Description

1 / 12 METHOD FOR RECYCLING PHOTOVOLTAIC MODULES FIELD OF THE INVENTION

[01] In general, the present invention belongs to the technological sector of recycling and reuse of waste and refers, more specifically, to a method for recycling photovoltaic modules capable of characterizing and recycling crystalline silicon (c-Si) photovoltaic modules, with the objective of properly disposing of this waste and, consequently, reducing the pollution generated by the photovoltaic industry, reintroducing these materials into the production chain in an ecological way and with minimal environmental impact. BACKGROUND OF THE INVENTION

[02] As is generally known, solar radiation is a clean energy source and, as far as is known, an infinite and inexhaustible resource. The solar cell is the central element of photovoltaic generation, responsible for converting solar energy in the form of light into electrical energy.

[03] It is known that a solar cell is made up of a p-type semiconductor and an n-type semiconductor, so that when light falls on a photovoltaic cell, electrons and holes (gaps) are produced in the semiconductor due to the photovoltaic effect, first described in 1839 by Alexandre-Edmond Becquerel, when he observed the appearance of a potential difference between electrodes immersed in an acidic solution. When a photon is absorbed, an electron is released from the atom. The electron-hole pair can be separated by an electric field, and this is achieved with the help of the pn junction. In the absence of an electric field, the electron would recombine with the hole, while in the presence of the field the electron flows, creating a current. If the photon energy is less than the band gap energy, the Petition 870260052828, dated 01 / 06 / 2026, page 41 / 65 2 / 12 of the electron will not have enough energy to jump to the conduction band, so this excess energy will be converted into thermal energy or may even be transmitted, generating a temperature increase. If both sides of the cell are connected to a load, an electric current will arise as long as there are photons incident on the cell.

[04] A set of cells is called a photovoltaic module, traditionally made of crystalline silicon (c-Si) and typically marketed with a vitrified structure under which are found an encapsulant, a solar cell, another encapsulant and, finally, a backsheet sequentially superimposed. Such cells (c-Si) account for about 90% of the photovoltaic panels marketed in the world.

[05] That said, there are also some alternatives that represent the current state of the art and that are described in patent documents. Some examples can be seen in the case of US invention patent no. US11104116 “METHOD FOR DISMANTLING SOLAR CELL MODULE FOR RECYCLING”, which discloses a method for dismantling a solar cell module for recycling comprising the steps of: providing a silicon solar cell module in which a silicon solar cell element and one side of the glass are joined by a sealing agent and a layer of transparent conductive material is coated between the glass side and the sealing agent; applying high voltage between the layer of transparent conductive material and the other side of the glass; and separating the glass and the sealing agent exposing the silicon solar cell module having the layer of transparent conductive material discolored by the application of high voltage to a humid environment. Petition 870260052828, dated 01 / 06 / 2026, p. 42 / 65 3 / 12

[06] However, this invention is based exclusively on the application of electric current in a humid environment to extract recyclable conductive material, leaving aside other waste, generating environmental impact and not being a complete recycling cycle aimed at the ecological and circular economy.

[07] There is also Brazilian patent BR102016025097-8 “METHOD FOR REMOVING AND RECOVERING SILVER METAL FROM FIRST-GENERATION CRYSTALLINE SILICON PHOTOVOLTAIC MODULES” which discloses a method for removing and recovering silver metal from first-generation crystalline silicon photovoltaic modules using mechanical operations with mills and hydrometallurgical operations with acidic solutions and salts to cause leaching and decantation of silver. Specifically, the present invention comprises the use of nitric acid and sodium chloride for the leaching and separation steps of silver chloride salts from the solution. The present invention is situated in the field of chemistry.

[08] However, as the title itself points out, this is only a method of silver recovery, which demonstrates the current state of the art, capable only of dealing with the recycling of parts of the photovoltaic array and not the whole thing, resulting in a large amount of waste destined for landfills.

[09] Thus, given all the drawbacks of the systems and equipment currently used, described above in the state of the art, a gap is evident in the creation of a photovoltaic module recycling method capable of characterizing and recycling crystalline silicon (c-Si) photovoltaic modules, with the aim of properly disposing of these wastes and, consequently, reducing the pollution generated by the photovoltaic industry, reintroducing these Petition 870260052828, dated 01 / 06 / 2026, page 43 / 65 4 / 12 materials in the production chain in an ecological way and with minimal environmental impact. SUMMARY AND NOVELTY OF THE INVENTION

[010] The present invention relates to a method for recycling photovoltaic modules which characterizes and recycles crystalline silicon (c-Si) photovoltaic modules, with the aim of properly disposing of these waste materials and, consequently, reducing the pollution generated by the photovoltaic industry, reintroducing these materials into the production chain in an ecological way and with minimal environmental impact.

[011] The present method includes the steps of manual separation, pyrolysis, electromagnetic separation, metal separation, characterization of the received sample by SEM-EDS, characterization after leaching with nitric acid (HNO3) by SEM, characterization after leaching with potassium hydroxide (KOH) by SEM-EDS, liquid-liquid extraction aiming at the extraction of copper (Cu), re-extraction (stripping) using sulfuric acid (H2SO4), precipitation of silver (Ag) through the addition of hydrochloric acid (HCl) and precipitation of lead (Pb).

[012] Thus, in order to remedy the shortcomings of the current state of the art, the present invention patent aims to propose a method for recycling photovoltaic modules which characterizes and recycles crystalline silicon (c-Si) photovoltaic modules, through simple and easy-to-execute physical-chemical steps, which enable the complete recycling of the modules, eliminating the need to dispose of waste in landfills or dumps, reintroducing these materials into the production chain in an ecological way and with minimal environmental impact. BRIEF DESCRIPTION OF THE FIGURES

[013] In order for the present invention to be fully understood and put into practice by any technician in this technological field, the Petition 870260052828, dated 01 / 06 / 2026, page 44 / 65 5 / 12 it will be described in a clear, concise and sufficient manner, based on the attached drawings, which illustrate and support it listed below:

[014] Figure 1 represents a disused photovoltaic cell.

[015] Figure 2 represents the pyrolyzer.

[016] Figure 3 represents the flowchart of the pyrolysis process used.

[017] Figure 4 represents the wafer obtained after pyrolysis.

[018] Figure 5 represents the liquid extract resulting from pyrolysis.

[019] Figure 6 represents the chemical composition of the liquid extract resulting from pyrolysis.

[020] Figure 7 represents the spectrum analysis of the microstructural characterization of the front face of the cell.

[021] Figure 8 represents the semi-quantitative characterization of the frontal face.

[022] Figure 9 represents the spectrum analysis of the back face of the wafer.

[023] Figure 10 represents the semi-quantitative analysis of the back face of the wafer.

[024] Figure 11 represents the spectrum analysis of the microstructural characterization of the busbar.

[025] Figure 12 represents the semi-quantitative characterization of the busbar.

[026] Figure 13 represents the appearance of the HNO3 solution containing Cu, Ag and Pb.

[027] Figure 14 represents the semiquantitative analysis of the back face of the wafer after HNO3.

[028] Figure 15 represents the appearance of the KOH solution. Petition 870260052828, dated 01 / 06 / 2026, page 45 / 65 6 / 12

[029] Figure 16 represents the semiquantitative analysis of the back face of the wafer after KOH, lacking Al and Pb.

[030] Figure 17 represents the leaching sequence using LIX-84-l.

[031] Figure 18 represents the appearance of the solution leached with H2SO4.

[032] Figures 19 and 19A represent the process flowchart of the method used. DESCRIPTION OF THE INVENTION

[033] The present method begins with manual separation, in which the modules are separated according to the properties of each one, namely: size, weight, power, generation, technology, etc. After that, the modules are subjected to a characterization process to obtain basic information about their properties, as previously described.

[034] To remove the aluminum frame, a grinder with a diamond disc is used to remove the edges and a hot cutting knife is used to heat the frame, making it easier to separate the aluminum frame from the encapsulating material (EVA).

[035] At this stage, the junction box and cables are also removed so that the rest of the module (glass and wafer) can then be sent to the thermal pyrolysis process.

[036] In pyrolysis (1) a batch reactor is used, as illustrated in Figure 2. This reactor has a removable lid, heating furnace, condensers for cooling the products, liquid collector and separator and a gas outlet line for collecting and burning non-condensable gases.

[037] The reactor is closed, positioned in the furnace and coupled to the condensation line, being heated from ambient temperature to 500°C using a heating rate of approximately 1°C / min. Petition 870260052828, dated 01 / 06 / 2026, page 46 / 65 7 / 12

[038] The volatile products then leave the reactor in the form of hot gases and vapors, which pass through the condensers where they are indirectly cooled with water to room temperature, so that the separation between liquids and non-condensable gases occurs voluntarily.

[039] During the volatile product release phase, pyrolysis gases are sampled through the outlet pipe using multilayer gas bags. At this stage, sampling is carried out in a temperature range that can vary from 120°C to 300°C and from 300° to 500°C.

[040] It is possible to check the flammability of the gases using a burner and an ignition source, so that, after the final temperature is reached, the reactor is left to cool naturally to room temperature and then opened to collect the remaining solid product inside.

[041] Figure 3 shows a flowchart to illustrate the pyrolysis process.

[042] After these steps, the solid and liquid products are stored in sealed bottles and subsequently portioned for transport, without being stored under refrigeration.

[043] Figure 4 shows the silicon cells and silver fingers contained in the wafers after the pyrolysis process.

[044] During the development of the technological route, pyrolysis was chosen to separate the silicon wafer from the glass plates. The pyrolysis process generates two residues, a gaseous residue and a liquid residue. The appearance of the liquid residue is shown in Figure 5. For the correct disposal of this residue, a complete analysis of the liquid extract is essential, as shown in Figure 6. Petition 870260052828, dated 01 / 06 / 2026, page 47 / 65 8 / 12

[045] Next, the glass and the photovoltaic cells and busbar, which are responsible for collecting the electric current produced by the photovoltaic cells, are separated by means of an electromagnetic separation (2), so that the more conductive materials (cells and busbar) are attracted by an electromagnet, being separated from the glass.

[046] From this separation, the metals are sent to a chemical separation process by leaching.

[047] Thus, the metal separation stage (3) consists of eight sub-stages, namely: Substage 3.1 - Characterization of the sample received by MEVEDS for evaluation of the metals present; Substep 3.2 - Characterization of the sample after leaching with HNO3 by SEM-EDS, aiming to evaluate the efficiency of Si wafer release; Substep 3.3 - Characterization of the sample after leaching with KOH by SEM-EDS, aiming to evaluate the efficiency of Si wafer release; Substage 3.4 - Characterization of the solution obtained from leaching the solar cell using HNO3, analysis of Ag, Sn, Pb, Cu via atomic absorption; Substage 3.5 - Performing a liquid-liquid extraction step aimed at the selective extraction of Cu, followed by characterization of the solution obtained after extraction (raffinate), analyses of Ag, Sn, Pb, Cu; Substep 3.6 - Performing a re-extraction (stripping) step using H2SO4, aiming to obtain a Cu-rich solution (extract), followed by characterization of the solution through the determination of the concentrations of Ag, Sn, Pb, Cu; Petition 870260052828, dated 01 / 06 / 2026, page 48 / 65 9 / 12 Substep 3.7 - Performing an Ag precipitation step by adding HCl, followed by characterization of the solution obtained after precipitation, analysis of Ag, Sn, Pb, Cu via atomic absorption. Characterization of the solid precipitate will also be performed by SEM-EDS and X-ray diffraction; Substage 3.8 - Performing a lead precipitation step by adding NaOH, followed by characterization of the solution obtained after precipitation, analyses of Ag, Sn, Pb, Cu. Characterization of the solid precipitate will also be performed by SEM-EDS and X-ray diffraction.

[048] Figure 7 presents the SEM-EDS results for the front face. SEM-EDS characterization of the front face of the Si wafer plate was performed at four points (a.1, a.2, a.3, a.4), producing four spectra (a.1.1, a.2.1, a.3.1, a.4.1).

[049] The results obtained by EDS (semi-quantitative analysis) at different points on the front face are presented in figure 8. The most representative elements on the upper face of the wafer were Silver (Ag), predominant in the collectors present in the photovoltaic cell, and silicon (Si), which is the constituent material of the photovoltaic cell; traces of Mg, Ti, Cu, Pb, Sn and In were also identified.

[050] Figure 9 shows an image of the back face of the wafer, where the different structures present can be observed. SEM EDS was then performed to characterize these different structures and the results are presented in Figure 10. The characterization of the back face was performed at three points (a, b, c), obtaining three spectra (a.1, b.1, c.1).

[051] The results obtained by EDS (semi-quantitative analysis) at different points on the back face are presented in Figure 10. The Petition 870260052828, dated 01 / 06 / 2026, page 49 / 65 10 / 12 of the most representative elements on the underside of the wafer were titanium (Ti) and aluminum (Al) in region a.1; aluminum (Al) and silicon (Si) in region b.1 of the cell; and silicon (Si) in region c.1, the base constituent of the photovoltaic cell. Traces of Ca, C, Pb, Sn, and Sb were identified using SEM-EDS on the back side of the cell.

[052] In order to characterize the filament (busbar) that separated from the wafer during the delamination process, SEM-EDS analyses were performed. Figure 11a shows the morphology of the outer lateral part of the filament and Figure 11a.1, its respective semi-quantitative characterization. Figure 11b shows the micrograph of the cross-section of the filament, and Figure 11b.1 its respective semi-quantitative characterization.

[053] The results obtained by EDS (semi-quantitative analysis) at different points of the filament are presented in Figure 12. The most representative elements of the outer side (coating) of the filament were lead (Pb), tin (Sn) and titanium (Ti). In the cross-section, the main constituents were copper (Cu), lead (Pb) and tin (Sn).

[054] Figure 13 shows the appearance of the HNO3 solution containing Cu, Ag and Pb, used for the chemical processing (leaching) of the recycled components.

[055] In figure 14 it is possible to observe the semiquantitative analysis of the back face of the wafer after HNO3. Note the presence of 75.47% Al in a.1 and the high concentration (97.98%) of Si observed in the EDS in c.1.

[056] Figure 15 shows the appearance of the KOH solution, evidencing a semi-transparent leaching process, indicating absence Petition 870260052828, dated 01 / 06 / 2026, pages 50 / 65 11 / 12 of Al and Pb, as can be seen in the semi-quantitative analysis of the back face of the wafer after KOH, see figure 16.

[057] Note in figure 17, which shows the leaching sequence, after addition of the organic reagent (LIX 84-I), the upper phase containing LIX and Copper is observed, and the lower phase (raffinate) is composed mainly of Ag2+ and Pb2+ ions.

[058] In figure 18, when a 150 gL-1 solution of H2SO4 is added in a 1 to 4 ratio of LIX-84I, the removal of Cu2+ ions in the form of Copper II Sulfate (Cu(SO4)2) is observed.

[059] Finally, based on the data presented above, the present method makes it possible to determine the chemical composition of the modules.

[060] Silver (Ag) is present in the electrodes on the front of the wafer, while aluminum (Al) electrodes are present on the back of the wafer. The wafer is made of silicon (Si), and the filament on the front face is formed by a copper (Cu) wire coated with a Sn / Pb alloy. However, as can be seen in figures 8, 10, 12, 14, and 16, the presence of titanium (Ti) was detected in the samples.

[061] In this way, the filament is not completely solubilized. Therefore, the experiment carried out at room temperature (~18°C) results in a sample consisting basically of copper resistant to HNO3.

[062] Leaching with KOH was efficient for leaching aluminum, and lead solubilization was also observed. In this sense, leaching is carried out using a 45% potassium hydroxide (KOH) solution for 10 minutes at 80°C. However, characterization showed that traces of aluminum were still detected in two of the three regions analyzed. Another contaminant still present is tin, which was detected in all 3 regions analyzed. Petition 870260052828, dated 01 / 06 / 2026, pages 51 / 65 12 / 12

[063] The results obtained in the AAS analyses for the solution before and after the precipitation step indicate that precipitation did in fact occur. The solution before precipitation contained 50.8 PPM, and after precipitation this concentration dropped to 5.24 PPM.

[064] Finally, note that the addition of NaOH to the solution containing both copper and lead resulted in the joint precipitation of both metals. Petition 870260052828, dated 01 / 06 / 2026, p. 52 / 65

Claims

1 / 2 CLAIMS:

1. METHOD FOR RECYCLING PHOTOVOLTAIC MODULES which comprises a manual separation step, in which the modules are separated according to the properties of size, weight, power, generation, technology characterized by presenting the steps of (1) pyrolysis, (2) electromagnetic separation and (3) metal separation, divided into sub-steps: (3.1) characterization of the received sample by SEM-EDS, (3.2) characterization after leaching with nitric acid (HNO3) by SEM, (3.3) characterization after leaching with potassium hydroxide (KOH) by SEM-EDS, (3.4) Characterization of the solution obtained in the leaching of the solar cell using HNO3, analysis of Ag, Sn, Pb, Cu via atomic absorption, (3.5) liquid-liquid extraction aiming at the extraction of copper (Cu), (3.6) re-extraction (stripping) using sulfuric acid (H2SO4), (3.7) precipitation of silver (Ag) by adding hydrochloric acid (HCl) and (3.8) precipitation of lead (Pb).

2. METHOD FOR RECYCLING PHOTOVOLTAIC MODULES, according to claim 1, and further characterized in that the pyrolysis step occurs through heating from ambient temperature to 500°C, with a heating rate of 1°C / min.

3. METHOD FOR RECYCLING PHOTOVOLTAIC MODULES, according to claim 1, characterized in that the gases resulting from pyrolysis are sampled in a temperature range that can vary from 120°C to 300°C and from 300°C to 500°C.

4. METHOD FOR RECYCLING PHOTOVOLTAIC MODULES, according to claim 1, characterized by the leaching step forming an upper phase containing Copper and a lower phase composed of Ag2+ and Pb2+ ions.

5. METHOD FOR RECYCLING PHOTOVOLTAIC MODULES, according to claim 1, characterized by the addition of a 150 gL-1 H2SO4 solution in a 1:4 ratio of organic reagent, resulting in the removal of Cu2+ ions in the form of Copper(II) Sulfate (Cu(SO4)2).

6. METHOD FOR RECYCLING PHOTOVOLTAIC MODULES, according to claim 1, characterized by leaching being carried out with a 45% potassium hydroxide (KOH) solution for 10 minutes at 80°C.

7. METHOD FOR RECYCLING PHOTOVOLTAIC MODULES, according to claim 1, characterized by the addition of NaOH to the solution obtained in the leaching step, containing Cu as well as Pb, resulting in the precipitation of both. Petition 870260052828, dated 01 / 06 / 2026, pp. 54 / 65

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