Silicon recycling method for preparing aerogel by using concentrated alkali wastewater in photovoltaic industry

Abstract

The invention discloses a silicon recycling method for preparing aerogel by using concentrated alkali wastewater in the photovoltaic industry, which comprises the following steps: feeding concentrated alkali wastewater and acid water into a reactor, controlling the pH value of the wastewater to be 6-9, adding glass fibers into the reactor, starting ultrasonic equipment, carrying out ultrasonic operation for 5-30 minutes, then closing the ultrasonic equipment, continuously reacting the wastewater for 1-4 hours to form silica gel with the glass fibers, and recycling the silica gel with the glass fibers. The method comprises the following steps: carrying out dehydration treatment on silica gel, transferring the dehydrated silica gel into an aging reactor, adding an aging agent into the aging reactor for aging treatment, and drying the aged silica gel to obtain the blocky glass fiber reinforced silica aerogel. And a silicon dioxide aerogel product with high strength and stable properties is prepared, so that resource recovery of silicon in concentrated alkali wastewater is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a silicon resource recovery method for preparing aerogel by utilizing concentrated alkaline wastewater from the photovoltaic industry. Background Art

[0002] Solar energy, an inexhaustible, clean energy source, has garnered widespread attention in the context of sustainable development. Solar photovoltaic technology has rapidly developed, and the photovoltaic industry is growing rapidly. While the photovoltaic industry utilizes solar power for power generation, it does not generate pollution. However, the production of solar cells, a key component of photovoltaic systems, involves the use of large quantities of hydrofluoric acid and sodium hydroxide for etching, texturing, and cleaning operations, generating wastewater, including concentrated acid, concentrated alkali, dilute acid, and dilute alkali.

[0003] Acidic wastewater contains significant amounts of fluoride. Current treatment methods typically rely on calcium defluoridation. This involves adding agents such as lime and calcium chloride to reduce the fluoride ion concentration in the water while converting it into calcium fluoride sludge or products, thereby recovering fluoride resources. Alkaline wastewater is generally treated in two ways: mixing it with acidic wastewater, where it is used as a neutralizing agent, or treating it separately, where it is neutralized with acid and then discharged directly to meet standards. Alkaline wastewater also contains significant amounts of silicon. Since there are currently no restrictions on silicon in photovoltaic wastewater discharge standards, both of these methods rely on direct discharge, without considering the recovery and resource utilization of silicon in alkaline wastewater, particularly concentrated alkaline wastewater. This results in a waste of silicon resources. Since silicon content in concentrated alkaline wastewater can reach over 4000 mg / L, accounting for over 85% of the total silicon content, the recovery and resource utilization of silicon in concentrated alkaline wastewater is of great significance. Summary of the Invention

[0004] In order to overcome the above-mentioned defects, the present invention provides a silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry. The silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry can remove silicon from the concentrated alkaline wastewater and produce a silicon dioxide aerogel product, thereby realizing the resource recovery of silicon.

[0005] The present invention adopts a technical solution to solve the technical problem: a silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry, characterized by the following specific steps:

[0006] Step 1: The concentrated alkaline wastewater generated by the photovoltaic industry is fed into the reactor, and acid water is added to the reactor to control the pH of the wastewater within the range of 6-9;

[0007] Step 2: Add glass fiber into the reactor, the amount of glass fiber added is 10%-30% of the silicon concentration in the concentrated alkaline wastewater;

[0008] Step 3: Turn on the ultrasonic equipment installed at the bottom of the reactor, and run the ultrasonic for 5-30 minutes;

[0009] Step 4: Turn off the ultrasonic equipment and continue the reaction of wastewater for 1-4 hours to form a silica gel with glass fibers;

[0010] Step 5: Dehydrating the silicone gel;

[0011] Step 6: Transfer the dehydrated silica gel to an aging reactor, and add an aging agent into the aging reactor for aging treatment;

[0012] Step 7: Drying the aged silica gel to obtain block-shaped glass fiber reinforced silica aerogel.

[0013] Silicon in concentrated alkaline wastewater primarily exists as silicate ions. Adding acidic water to adjust the wastewater's pH to neutral allows hydrogen ions to combine with silicate ions to form silicic acid. Under certain conditions, silicic acid undergoes reactions such as coagulation and dehydration to convert into SiO2·nH2O, which then forms a gel. Adding glass fiber to the silica gelation process enhances its strength and other physical properties, broadening the application range of the resulting silica gel product. To ensure uniform mixing of the glass fiber and the uniformity and size of the particles during the silica gelation reaction, ultrasonic technology is used to enhance the reaction. The silica gel is then aged. An aging agent replaces the water within the gel, preventing rapid evaporation of water from the gel's pores during natural aging. This effectively prevents pore shrinkage or collapse during long-term use or storage. This method ultimately yields silica aerogel products that maintain a nanoscale porous network structure over time.

[0014] As a further improvement of the present invention, the acid water in step 1 is concentrated acid wastewater generated by the photovoltaic industry. The concentrated alkaline wastewater and concentrated acid wastewater generated by the photovoltaic industry are first collected separately and homogenized, and then the homogenized concentrated alkaline wastewater and concentrated acid wastewater are transported into the reactor via a pump and a pipeline to ensure sufficient reaction between the two, which is conducive to maintaining reaction stability.

[0015] As a further improvement of the present invention, during the addition of acid water to the reactor in step 1, the pH of the wastewater is monitored online in real time by a pH detection device to control the amount of acid water added. By online monitoring of the pH of the wastewater in the reactor and controlling the amount of acid water added, the pH of the wastewater can be maintained between 6 and 9, allowing the silicon in the wastewater to fully react and form silica gel.

[0016] As a further improvement of the present invention, the time for mixing the concentrated alkaline wastewater and the acid water in step 1 is 10-30 minutes.

[0017] As a further improvement of the present invention, the operating frequency of the ultrasonic equipment in step three is 25kHz-40kHz.

[0018] As a further improvement of the present invention, the step five includes the following steps:

[0019] Step 5.1: Dehydrating the silicone gel for the first time to reduce the moisture content of the silicone gel to 80%-90%;

[0020] Step 5.2: Rinse the dehydrated silicone gel with clean water, the amount of clean water used is 5-10 times the amount of silicone gel;

[0021] Step 5.3: Dehydrate the cleaned silicone gel for the second time to reduce the moisture content of the silicone gel to 80%-90%.

[0022] After the silica gel is dehydrated, cleaned and dehydrated again, the impurities in the silica gel are fully removed, which is conducive to the subsequent acquisition of pure silica aerogel products.

[0023] As a further improvement of the present invention, in both step 5.1 and step 5.3, a screw press dehydrator is used to dehydrate the silica gel.

[0024] As a further improvement of the present invention, in step 6, the aging agent is at least one of ethanol, n-propanol, and isopropanol, and when the aging agent is a mixture of two or three of ethanol, n-propanol, and isopropanol, the components are mixed in any proportion. The aging agent can be selected from one of ethanol, n-propanol, and isopropanol as a single-component aging agent, or two or three of them can be mixed to form a multi-component aging agent.

[0025] As a further improvement of the present invention, in step six, the ratio of the amount of the aging agent to the amount of the silicone gel is 1:1-1:2, the aging temperature is 20-40° C., and the aging time is 6-24 h.

[0026] As a further improvement of the present invention, in step seven, the aged silicone gel is dried in a dryer at normal temperature and pressure.

[0027] The beneficial effects of the present invention are as follows: after the pH is adjusted by adding acid water to the concentrated alkaline wastewater generated by the photovoltaic industry, the silicon in the concentrated alkaline wastewater is converted into silicic acid; during the gelation process of the silicic acid, a certain amount of glass fiber is added to the wastewater, so that the glass fiber effectively supports the silicone gel, thereby effectively improving the physical properties of the silicone gel product; the present invention also improves the dispersion and particle size of the particles in the gelation process and the uniformity of mixing with the glass fiber by introducing ultrasound during the gelation reaction; finally, the clean silicone gel after washing and dehydration is aged to avoid pore shrinkage or collapse of the silicone gel due to rapid evaporation of water in the natural aging state; the method of the present invention can effectively remove silicon from the concentrated alkaline wastewater and make a silica aerogel product with high strength and stable properties, thereby realizing the resource recovery of silicon in the concentrated alkaline wastewater; the present invention further selects the concentrated acid wastewater generated by the photovoltaic industry as the acid water, thereby reducing the resource recovery cost of silicon in the concentrated alkaline wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0029] To make the advantages, technical solutions, and innovations of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0030] Example: The silicon content in the concentrated alkaline wastewater generated by a photovoltaic enterprise is 4500-7800 mg / L. The silicon resource recovery method for preparing aerogel using the concentrated alkaline wastewater generated by the photovoltaic enterprise is as follows:

[0031] The homogenized concentrated alkaline wastewater and concentrated acid wastewater are transported into the reactor through a pump and a pipeline, and the amount of concentrated acid wastewater added is controlled by online monitoring of the pH of the mixed wastewater through a pH detection device, and the pH of the mixed wastewater is controlled within the range of 6.5-8.5. The concentrated alkaline wastewater and concentrated acid wastewater are mixed in the reactor for 10 minutes;

[0032] Adding glass fiber to a reactor after mixing concentrated acid wastewater and concentrated alkaline wastewater, the amount of glass fiber added is 10% of the silicon concentration in the concentrated alkaline wastewater, turning on an ultrasonic device with an operating frequency of 28 kHz and an ultrasonic operation time of 8 minutes. After turning off the ultrasonic device, the mixture in the reactor continues to react for 2 hours to form a silicone gel with glass fiber;

[0033] The generated silica gel is dehydrated for the first time using a screw dehydrator to reduce the moisture content of the silica gel to 90%;

[0034] The dehydrated silica gel is washed with clean water, the amount of clean water is 10 times the amount of silica gel, and then dehydrated for the second time using a spiral dehydrator to control the moisture content of the silica gel to 90%;

[0035] The dehydrated silica gel was transferred to an aging reactor for aging treatment. Ethanol was used as an aging agent during the aging process. The ratio of ethanol to silica gel was 1:1.5. The aging temperature was set at 35°C and the aging time was 18 h.

[0036] The aged silica gel enters a normal temperature and pressure dryer, where it is first dried at 60°C for 1 hour and then at 100°C for 2 hours, ultimately obtaining block-shaped glass fiber reinforced silica aerogel.

Claims

1. A silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry, characterized by: The specific steps are as follows: Step 1: The concentrated alkaline wastewater generated by the photovoltaic industry is fed into the reactor, and acid water is added to the reactor to control the pH of the wastewater within the range of 6-9; Step 2: Add glass fiber into the reactor, the amount of glass fiber added is 10%-30% of the silicon concentration in the concentrated alkaline wastewater; Step 3: Turn on the ultrasonic equipment installed at the bottom of the reactor, and run the ultrasound for 5-30 minutes; Step 4: Turn off the ultrasonic equipment and continue the reaction of wastewater for 1-4 hours to form a silica gel with glass fibers; Step 5: Dehydrating the silicone gel; Step 6: Transfer the dehydrated silica gel to an aging reactor, and add an aging agent into the aging reactor for aging treatment; Step 7: Drying the aged silica gel to obtain block-shaped glass fiber reinforced silica aerogel.

2. The silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry according to claim 1, characterized in that: The acid water in step 1 is concentrated acid wastewater generated in the photovoltaic industry.

3. The silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry according to claim 1 or 2, characterized in that: During the process of adding acid water into the reactor in step 1, the pH of the wastewater is monitored online in real time by a pH detection device to control the amount of acid water added.

4. The silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry according to claim 1, characterized in that: In the step 1, the concentrated alkaline wastewater and the acid water are mixed for 10-30 minutes.

5. The silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry according to claim 1, characterized in that: The operating frequency of the ultrasonic equipment in step 3 is 25kHz-40kHz.

6. The silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry according to claim 1, characterized in that: The step five includes the following steps: Step 5.1: Dehydrating the silicone gel for the first time to reduce the moisture content of the silicone gel to 80%-90%; Step 5.2: Rinse the dehydrated silicone gel with clean water, the amount of clean water used is 5-10 times the amount of silicone gel; Step 5.3: Dehydrate the cleaned silicone gel for the second time to reduce the moisture content of the silicone gel to 80%-90%.

7. The silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry according to claim 6, characterized in that: In both step 5.1 and step 5.3, a screw press dehydrator is used to dehydrate the silica gel.

8. The silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry according to claim 1, characterized in that: In step 6, the aging agent is at least one of ethanol, n-propanol and isopropanol, and when the aging agent is a mixture of two or three of ethanol, n-propanol and isopropanol, the components are mixed in any proportion.

9. The silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry according to claim 1, characterized in that: In the step six, the ratio of the amount of the aging agent to the amount of the silicone gel is 1:1-1:2, the aging temperature is 20-40° C., and the aging time is 6-24 hours.

10. The silicon resource recovery method for preparing aerogel using concentrated alkaline wastewater from the photovoltaic industry according to claim 1, characterized in that: In step seven, the aged silicone gel is dried in a dryer at normal temperature and pressure.

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