Eutectic solvent and method for separating and recycling metal in waste crystalline silicon photovoltaic panel battery piece by using eutectic solvent

Abstract

The invention discloses a preparation method of a eutectic solvent for separating and recycling metals in waste crystalline silicon photovoltaic panels. According to the method, betaine hydrochloride is used as a hydrogen bond acceptor, ethylene glycol is used as a hydrogen bond donor to prepare a deep eutectic solvent with high solubility, and copper chloride is used as an oxidizing agent to leach metal silver and metal aluminum in the waste photovoltaic panel crystal silicon wafer. The leaching system is easy to operate, strong acid and strong alkali used in traditional wet recovery do not participate in the leaching system, and the problem of discharge of waste gas and waste water is solved. In the recovery process, the used ammonia water and water can be reused after rotary evaporation. Compared with a traditional crystalline silicon photovoltaic panel recycling route, the method has the advantages that the technological process is shortened, the cost is reduced, and an effective method is provided for recycling the waste crystalline silicon photovoltaic panel.

Description

Technical Field

[0001] The present invention relates to the technical field of waste photovoltaic panel recycling, and in particular to a low eutectic solvent and a method for separating and recycling metals in waste crystalline silicon photovoltaic panel cells. Background Art

[0002] As a new type of renewable energy, solar energy is one of the most promising and mature renewable energy production technologies. According to the service life of photovoltaic panels (25-30 years), it is estimated that a large number of waste photovoltaic panels will appear in my country by 2050. Improper handling of waste photovoltaic panels will cause great pollution to the environment, and the metals in photovoltaic panels will damage the soil and water sources. At the same time, waste photovoltaic panels have a strong recycling value, which contains a large amount of precious metals such as silver, aluminum, silicon, etc. Recycling photovoltaic panels can save a lot of metal resources. According to statistics, the average silver content in photovoltaic panels is 630 grams / ton, which is equivalent to 700g / t per ton of silver ore. In addition, the structure of photovoltaic panels is simple. Recycling silver from photovoltaic panels can reduce energy loss.

[0003] At present, the recycling methods of photovoltaic panels mainly consist of pyrometallurgy and hydrometallurgy. Pyrometallurgy is a process of recycling metals by controlling the temperature to melt waste photovoltaic panels at high temperature to separate the metal part from the non-metal part in the electronic waste. It has some inevitable disadvantages, such as high operating temperature, high energy cost, and more harmful waste gas emissions. The high recovery rate of the hydrometallurgical recycling process makes it widely used in the field of metal recycling. Traditional hydrometallurgical technology usually operates in an aqueous system, and due to the chemical inertness of silver and other precious metals, strong acids, strong bases and oxidants are usually required. The hydrometallurgical leaching process will produce harmful gases, which requires gas collection and purification equipment, increasing production costs.

[0004] A low eutectic solvent is a eutectic mixture that lowers the melting point through hydrogen bonding interactions between two or more components. It has outstanding advantages such as non-toxicity, a wide liquid phase range, high thermal stability and designability. It has a simple preparation process, a wide range of material sources, and a low price. It has great potential in the field of metal recycling.

[0005] The present invention uses a low eutectic solvent prepared by betaine hydrochloride and ethylene glycol, and adds cupric chloride as an oxidant to achieve efficient recovery of metals in waste crystalline silicon photovoltaic panels. The low eutectic solvent can provide a polar environment to solvate metal cations, while the oxidizing ability of cupric chloride allows the reaction to proceed. This special leaching method avoids the participation of strong acids and alkalis in traditional wet recovery, can be recovered through simple treatment, does not generate waste gas and wastewater, and is environmentally friendly. The present invention provides a new technology route for the recovery of metals in waste crystalline silicon photovoltaic panels with high efficiency, low cost and low pollution. Summary of the invention

[0006] The invention provides a low eutectic solvent and a method for separating and recovering metals in waste crystalline silicon photovoltaic panel cells.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A low eutectic solvent is a mixture of a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:1 to 1:12, wherein the hydrogen bond acceptor is betaine hydrochloride and the hydrogen bond donor is ethylene glycol.

[0009] Furthermore, the preparation method is: mixing a hydrogen bond donor and a hydrogen bond acceptor and heating and stirring to obtain a low eutectic solvent, wherein the heating temperature is 80 to 120°C and the heating and stirring time is 16 to 72 hours; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:5 to 1:8, preferably 1:6; the water content in the low eutectic solvent should be less than 35%.

[0010] A method for separating and recovering metals from waste crystalline silicon photovoltaic panel cells using a deep eutectic solvent comprises the following steps:

[0011] (1) Mixing a low eutectic solvent, an oxidant and waste crystalline silicon photovoltaic panel cell material in a certain proportion and heating and leaching; specifically:

[0012] First, according to the needs, the corresponding proportion of hydrogen bond donor ethylene glycol and hydrogen bond acceptor betaine hydrochloride are mixed and heated and stirred to form a light yellow transparent solution. The reaction temperature is 80℃~120℃ and the time is 24h~36h. During the reaction process, the temperature, time, and the ratio of hydrogen bond donor and hydrogen bond acceptor have a direct impact on the formation of the low eutectic solvent and the subsequent reaction with the waste crystalline silicon photovoltaic panel cells.

[0013] Then, copper chloride is added as an oxidant to the above solution, heated and stirred to form a brown-yellow solution, the amount of copper chloride added is 0.1-0.5 mol / L, the heating temperature is 80° C.-120° C., and the heating time is 1 h-12 h.

[0014] Next, add the waste crystalline silicon photovoltaic panel cells into the above solution, and heat and stir.

[0015] (2) filtering the mixed material after the reaction to separate the silicon wafer and the leachate, washing the silicon wafer with deionized water for multiple times to obtain a silicon wafer with higher purity, and testing the silver and aluminum contents in the leachate by ICP;

[0016] (3) adding deionized water to the leaching solution in a certain proportion to precipitate the silver in the form of silver chloride, filtering and rinsing for multiple times to obtain silver chloride with higher purity;

[0017] (4) adding oxalic acid to the filtrate in a certain proportion to purify the copper in the form of copper oxalate, filtering and rinsing for multiple times to obtain copper oxalate with higher purity;

[0018] (5) adding ammonia water to the filtrate in a certain proportion to precipitate the aluminum in the form of aluminum hydroxide, and washing it multiple times to obtain aluminum hydroxide with higher purity;

[0019] (6) The treated filtrate is subjected to rotary evaporation at 60° C. for 1 h to remove water and ammonia, thereby recovering the low eutectic solvent.

[0020] Furthermore, in the step (1), the solid-liquid ratio of the low eutectic solvent to the waste crystalline silicon photovoltaic panel cell material is 5 to 25 g / L; the leaching temperature is 40 to 120° C.; the leaching time is 0.5 h to 24 h; and the cupric chloride content is 0.1 mol / L to 1 mol / L.

[0021] Furthermore, in the step (3), the addition ratio of deionized water is 0.5L / L to 3L / L; in the step (4), the addition ratio of oxalic acid is 0.1mol / L to 1mol / L; in the step (5), the addition ratio of ammonia water is 0.1mol / L to 5mol / L.

[0022] The advantages of the present invention are:

[0023] 1. The low eutectic solvent used avoids the wastewater and waste gas problems generated in the traditional wet recovery process. It is environmentally friendly, can be recycled many times, and can be recycled through simple treatment.

[0024] 2. The low eutectic solvent used is simple to prepare, low in price, and has the advantages of high solubility, wide liquid phase range, non-toxicity and strong thermal stability. It provides a new idea for the metal recycling of waste crystalline silicon photovoltaic panel cells and is of great significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the thermogravimetric diagram of the prepared deep eutectic solvent.

[0026] Figure 2 It is the XRD pattern of silver chloride precipitate.

[0027] Figure 3 It is the XRD pattern of copper oxalate precipitate.

[0028] Figure 4 It is the XRD pattern of aluminum hydroxide precipitate.

[0029] Figure 5 This is a graph showing the effect of temperature on the metal leaching rate in waste photovoltaic panels.

[0030] Figure 6This is a graph showing the effect of time on the metal leaching rate in waste photovoltaic panels.

[0031] Figure 7 This is a graph showing the effect of the solid-liquid ratio on the metal leaching rate in waste photovoltaic panels.

[0032] Figure 8 This is a graph showing the effect of copper chloride addition on metal leaching rates in waste photovoltaic panels.

[0033] Fig. 9 This is a relationship diagram of the influence of different low eutectic solvent recovery times on the leaching rate. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with the embodiments and drawings. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0035] Example 1

[0036] A method for separating and recovering metals from waste crystalline silicon photovoltaic panel cells using a deep eutectic solvent, the specific steps are as follows:

[0037] Betaine hydrochloride and ethylene glycol were mixed in a molar ratio of 1:6 and reacted at 100°C for 24 hours to prepare a low eutectic solvent. The TG curve of the prepared low eutectic solution is shown in Figure 1 As shown by Figure 1 It can be seen that the ligand ethylene glycol of the low eutectic solvent begins to decompose at 135.4°C, and the temperature needs to be controlled below 130°C to prevent the ligand decomposition from affecting the reaction between the low eutectic solvent and the waste crystalline silicon photovoltaic panels.

[0038] Take 20ml of low eutectic solvent, add copper chloride and prepare a 0.5mol / L low eutectic solvent-copper chloride solution at a reaction temperature of 100℃. Add waste crystalline silicon photovoltaic panel cells at a solid-liquid ratio of 5g / L, react at 100℃ for 4h, filter to obtain leachate and filter residue, use ICP to test the silver and aluminum content of the filter residue and leachate, and obtain leaching rates of Ag=100% and Al=100%, respectively. No metal residue is detected in the filter residue, which is a pure silicon wafer and can be directly reused.

[0039] Add 2L / L deionized water to the leaching solution to precipitate silver chloride and filter it out. After multiple rinses, perform XRD tests, analyze phase parameters, and conduct qualitative analysis on the precipitate. Figure 2 As shown, the silver chloride precipitated after adding water has a high purity and no obvious impurity peaks in the XRD spectrum.

[0040] Add 0.5 mol / L oxalic acid to the filtrate to precipitate copper oxalate, and filter and separate it. After multiple rinses, perform XRD tests, analyze phase parameters, and conduct qualitative analysis on the precipitate. Figure 3 As shown, the copper oxalate precipitated after adding oxalic acid has a high purity and no obvious impurity peaks in the XRD spectrum.

[0041] Add 0.3 mol / L ammonia water to the filtrate to precipitate aluminum hydroxide, and filter and separate it. After multiple rinses, perform XRD tests, analyze phase parameters, and conduct qualitative analysis on the precipitate. Figure 4 As shown, the aluminum hydroxide precipitated after adding ammonia water has a high purity and no obvious impurity peaks in the XRD spectrum.

[0042] The treated filtrate is subjected to rotary evaporation at 60° C. for 1 h to remove water and ammonia, and the low eutectic solvent can be recovered.

[0043] Embodiments 2 to 5

[0044] The difference from Example 1 is that in this example, the leaching temperature is replaced with 80°C (Example 2), 90°C (Example 3), 110°C (Example 4), and 120°C (Example 5). The change of leaching rate is shown in Figure 5 .

[0045] Embodiments 6 to 9

[0046] The difference from Example 1 is that in this example, the leaching time is replaced by 1h (Example 6), 2h (Example 7), 3h (Example 8), and 5h (Example 9). The change of leaching rate is shown in Figure 6 .

[0047] Embodiments 10 to 13

[0048] The difference from Example 1 is that in this example, the solid-liquid ratio is replaced with 10 g / L (Example 10), 15 g / L (Example 11), 20 g / L (Example 12), and 25 g / L (Example 13). The change in leaching rate is shown in Figure 7 .

[0049] Embodiments 14 to 17

[0050] The difference from Example 1 is that in this example, the amount of copper chloride added and the amount of oxalic acid added are replaced with 0.1 mol / L (Example 14), 0.2 mol / L (Example 15), 0.3 mol / L (Example 16), and 0.4 mol / L (Example 17). The change in leaching rate is shown in Figure 8 .

[0051] Examples 18 to 22

[0052] The difference from Example 1 is that in this example, the prepared deep eutectic solvent is replaced by the recovered deep eutectic solvent, and the leaching rates of the deep eutectic solvents with different recycling times are as follows: Fig. 9 shown.

[0053] Embodiment 23

[0054] The difference from Example 1 is that in this example, the molar ratio of betaine hydrochloride to ethylene glycol is 1:5, and the leaching rate is Ag=100%, Al=100%.

[0055] Embodiment 24

[0056] The difference from Example 1 is that in this example, the molar ratio of betaine hydrochloride to ethylene glycol is 1:12, and the leaching rate is Ag=78.34%, Al=98.45%.

[0057] Embodiments 25-26

[0058] The difference from Example 1 is that in this example, the preparation temperature of the low eutectic solvent is 80°C (Example 25) and 120°C (Example 26). The leaching rate is Ag=100%, Al=100% (Example 25). The leaching rate is Ag=100%, Al=100% (Example 26).

[0059] Examples 27-28

[0060] The difference from Example 1 is that in this example, the preparation time of the low eutectic solvent is 16 h (Example 27) and 72 h (Example 28). The leaching rate is Ag = 100%, Al = 100% (Example 27). The leaching rate is Ag = 100%, Al = 100% (Example 28).

[0061] Embodiment 29

[0062] The difference from Example 1 is that in this example, the leaching temperature is replaced with 40° C. The leaching rates are Ag=28.78%, Al=36.69%.

[0063] Embodiment 30-31

[0064] The difference from Example 1 is that in this example, the leaching time is replaced by 0.5h (Example 30) and 24h (Example 31). The leaching rate is Ag=73.56%, Al=31.19% (Example 30). The leaching rate is Ag=100%, Al=100% (Example 31).

[0065] The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A deep eutectic solvent, characterized in that It is a mixture of a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:5 to 1:12, wherein the hydrogen bond acceptor is betaine hydrochloride and the hydrogen bond donor is ethylene glycol.

2. A deep eutectic solvent according to claim 1, characterized in that The preparation method is as follows: a hydrogen bond donor and a hydrogen bond acceptor are mixed and then heated and stirred to obtain a low eutectic solvent, wherein the heating temperature is 80 to 120° C. and the heating and stirring time is 16 to 72 hours.

3. A deep eutectic solvent according to claim 2, characterized in that: The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:5 to 1:8, preferably 1:6; the water content in the low eutectic solvent should be less than 35%.

4. A method for separating and recovering metals from waste crystalline silicon photovoltaic panel cells using a low eutectic solvent, characterized in that: The following steps are involved: (1) mixing a low eutectic solvent, an oxidant and waste crystalline silicon photovoltaic panel cell material in a certain proportion, and heating and leaching; (2) filtering the mixed material after the reaction to separate the silicon wafer and the leachate, and washing the silicon wafer with deionized water for multiple times to obtain a silicon wafer with higher purity; (3) adding deionized water to the leaching solution in a certain proportion to precipitate the silver in the form of silver chloride, filtering and rinsing for multiple times to obtain silver chloride with higher purity; (4) adding oxalic acid to the filtrate in a certain proportion to purify the copper in the form of copper oxalate, filtering and rinsing for multiple times to obtain copper oxalate with higher purity; (5) adding ammonia water to the filtrate in a certain proportion to precipitate the aluminum in the form of aluminum hydroxide, and washing it multiple times to obtain aluminum hydroxide with higher purity; (6) The treated filtrate is subjected to rotary evaporation at 60° C. for 1 h to remove water and ammonia, thereby recovering the low eutectic solvent.

5. The method for separating and recovering metals from waste crystalline silicon photovoltaic panel cells by using a deep eutectic solvent according to claim 4, characterized in that: In the step (1), the solid-liquid ratio of the low eutectic solvent to the waste crystalline silicon photovoltaic panel cell material is 5 to 25 g / L; the leaching temperature is 40 to 120° C.; and the leaching time is 0.5 h to 24 h.

6. The method for separating and recovering metals from waste crystalline silicon photovoltaic panel cells by using a deep eutectic solvent according to claim 4, characterized in that: In the step (1), the oxidant is cupric chloride, and the content of cupric chloride is 0.1 mol / L to 1 mol / L.

7. The method for separating and recovering metals from waste crystalline silicon photovoltaic panel cells by using a deep eutectic solvent according to claim 4, characterized in that: In the step (3), the addition ratio of deionized water is 0.5L / L to 3L / L.

8. The method for separating and recovering metals from waste crystalline silicon photovoltaic panel cells by using a deep eutectic solvent according to claim 4, characterized in that: In the step (4), the addition ratio of oxalic acid is 0.1 mol / L to 1 mol / L.

9. The method for separating and recovering metals from waste crystalline silicon photovoltaic panel cells by using a deep eutectic solvent according to claim 4, characterized in that: In the step (5), the addition ratio of ammonia water is 0.1 mol / L to 5 mol / L.

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