A method of making a glass frit and the resulting product

Abstract

The application discloses a preparation method of glass frit and the obtained product, and comprises the following steps: adding water glass, acid solution and activated carbon into electroplating wastewater in sequence, and stirring uniformly; then, drying under sunlight until dry gel is formed and the solid no longer loses weight; finally, high-temperature melting of the dry gel, water quenching to obtain glass frit. The application utilizes the excellent light-heat conversion efficiency of activated carbon to efficiently convert sunlight energy into heat energy, promotes the rapid evaporation of water in the gel, greatly shortens the drying time and reduces the energy consumption; meanwhile, the wastewater is all converted into gel and melted to form glass, and the harmful components in the wastewater are all solidified in the glass, so that the wastewater treatment is complete and the operation is simple; the obtained glass frit can be used for glaze or directly used as glass raw material, and the wastewater is turned into treasure.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment and resource utilization technology, specifically relating to a method for preparing glass frit using electroplating wastewater containing hazardous substances such as phosphorus or heavy metal ions as raw material, and the glass frit obtained by this method. Background Technology

[0002] The electroplating industry is a vital foundation of the national economy, but the process generates large quantities of wastewater containing hazardous substances such as heavy metal ions and phosphorus. Phosphorus discharge into water bodies leads to eutrophication and damages the aquatic ecosystem; while heavy metal ions such as chromium, nickel, and copper are biotoxic and non-degradable, posing a serious threat to the environment and human health. Traditional methods for treating electroplating wastewater include chemical precipitation, ion exchange, membrane separation, and biological treatment, but these methods generally suffer from complex processes, high costs, and the potential for secondary pollution.

[0003] In recent years, our research group has developed a gelation technology for treating electroplating wastewater using water glass (sodium silicate solution). Existing technologies include adding water glass to chromium electroplating wastewater to induce complete gelation, with the resulting gel being dried and used as an additive for glassmaking; another approach uses electroplating wastewater to provide an acidic environment for the reaction system, adjusting the pH with calcium oxide, and then reacting water glass with sodium aluminate to obtain a dry gel, which is then used to prepare sodium-calcium-aluminum silicate glass. Furthermore, there is a method for treating sulfate-containing electroplating wastewater by first adding barium nitrate for desulfurization before gelation treatment, and then using the resulting gel to prepare foamed microcrystalline glass.

[0004] However, existing technologies still have many shortcomings, mainly in the following aspects: the gelation reaction rate of water glass at room temperature is slow, which severely restricts the processing efficiency; the resulting gel has a high water content, and the traditional hot air or oven drying methods are energy-intensive and time-consuming, significantly increasing the processing cost; in addition, if no other substances besides water glass are introduced, the resulting gel can only be used as a glass additive due to its excessive Na2O content. If sodium aluminate is used in the gel, Na2O will be introduced again; and the use of barium nitrate for desulfurization complicates the water treatment process, and both methods increase the cost of electroplating wastewater treatment; while without desulfurization, unmelted sodium sulfate nitrate water will appear in the molten glass. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a method for preparing glass frit. This method uses electroplating wastewater as raw material and can also be referred to as a resource-based treatment method for electroplating wastewater. This invention involves adding water glass to the electroplating wastewater for gelation treatment, using an acidic solution to accelerate the gelation process and provide the necessary components for glass production. Activated carbon is added to the gelation reaction system, utilizing its excellent photothermal conversion efficiency to achieve gel drying under sunlight irradiation, significantly reducing drying energy consumption. Finally, the dried gel is melted at high temperature, and the melt is directly water-quenched to obtain glass frit, achieving efficient solidification and low-cost resource utilization of hazardous substances in electroplating wastewater.

[0006] The specific technical solution of this invention is as follows: A method for preparing a glass frit, the method comprising the following steps: (1) Add water glass, acidic solution and activated carbon to the electroplating wastewater in sequence, and mix them evenly under stirring conditions; (2) Place the mixture from step (1) under sunlight to dry until a dry gel is formed and constant weight is achieved; (3) The dry gel obtained in step (2) is melted at high temperature, and the resulting melt is quenched in water to obtain a glass frit.

[0007] Furthermore, the electroplating wastewater refers to wastewater generated in the electroplating industry. Electroplating wastewater contains phosphorus, or one or more heavy metal ions selected from chromium, nickel, copper, and zinc, as well as sulfate ions. In phosphorus-containing electroplating wastewater, the phosphorus content is greater than or equal to 150 mg / L.

[0008] Furthermore, in step (1), water glass, acidic solution and activated carbon are added in sequence, each reagent is added under stirring, and each reagent is stirred evenly before the next reagent is added.

[0009] Furthermore, in step (1), the volume ratio of electroplating wastewater to water glass is 25:2-3. The water glass can be a commercially available water glass product, and the modulus of the water glass is 3.2-3.5.

[0010] Furthermore, in step (1), the acidic solution is a sulfate solution or a phosphoric acid solution, wherein the sulfate solution is a ferrous sulfate solution with a concentration of 10-20 wt%, and the phosphoric acid solution has a concentration of 80-85 wt%.

[0011] Furthermore, in step (1), the amount of acidic solution used is 0.6~12% of the volume of electroplating wastewater, for example 0.6%, 1.0%, 1.2%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%.

[0012] Preferably, when the acidic solution is a sulfate solution, the amount of sulfate solution used is 8-12% of the volume of the electroplating wastewater. When the acidic solution is a phosphoric acid solution, the amount of phosphoric acid solution used is 0.6-1.2% of the volume of the electroplating wastewater.

[0013] Furthermore, in step (1), the ratio of activated carbon to electroplating wastewater is 0.05~0.25g:25ml, for example 0.05g:25ml, 0.10g:25ml, 0.15g:25ml, 0.20g:25ml, 0.25g:25ml.

[0014] Furthermore, in step (1), if the added acidic solution is a phosphoric acid solution, add activated carbon first, then add halloysite powder. If the acidic solution is not a phosphoric acid solution, then it is not necessary to add halloysite powder. Add 0.4-0.6g of halloysite powder per 100ml of electroplating wastewater.

[0015] Furthermore, after thoroughly stirring the mixture from step (1) and allowing it to stand, the mixture will become a gel. The addition of an acidic solution can accelerate the gelation reaction process and shorten the gel formation time. Activated carbon has excellent photothermal conversion efficiency, which can accelerate the drying process of the gel and improve the drying efficiency. After the mixture becomes a wet gel, it is placed under sunlight to dry naturally until a dry gel is formed and the dry gel no longer loses weight.

[0016] Furthermore, in step (3), the high-temperature melting treatment temperature is 1500~1550℃, and the holding time is 2-3 hours. After high-temperature melting, a glass melt is obtained. The glass melt is directly poured into water, or it is quenched in water through a pre-reserved hole at the bottom of the high-temperature furnace or crucible. The resulting broken glass is the glass frit. The glass frit is dried and kept for later use or sold as broken glass.

[0017] The present invention also provides a glass frit obtained according to the above method.

[0018] Compared with the prior art, the present invention has the following advantages: (1) The gelation reaction was accelerated, and the wastewater treatment efficiency was improved. The present invention effectively accelerated the gelation reaction of water glass in electroplating wastewater by adding an acidic solution, significantly shortened the gel formation time, and improved the treatment efficiency of electroplating wastewater.

[0019] (2) Significantly reduced drying energy consumption. This invention is the first to apply the photothermal conversion characteristics of activated carbon to the drying process of electroplating wastewater gel. Activated carbon has a broad spectrum of absorption capacity and excellent photothermal conversion efficiency, enabling it to efficiently absorb solar energy and convert it into heat energy, promoting the rapid evaporation of moisture inside the gel, significantly shortening the drying time and reducing energy consumption. Compared with traditional hot air drying or oven drying methods, this invention makes full use of sunlight, a clean energy source, significantly reducing the energy consumption of the drying process, which meets the requirements of green environmental protection and sustainable development.

[0020] (3) Efficient solidification of hazardous substances is achieved. This invention uses a gelation process to uniformly solidify phosphorus and heavy metal ions in electroplating wastewater into a silica gel network structure, then melts it at high temperature to form a glass melt, and then rapidly cools it to form a solid glass block. Hazardous substances are firmly sealed in the silica tetrahedral network of the glass, with an extremely low leaching rate, thus achieving safe and stable solidification treatment.

[0021] (4) The addition of activated carbon can promote the decomposition of sulfate and inhibit the generation of "nitrate water" during the process of sulfate-containing gel melting into glass melt at high temperature and water quenching into glass melt. There is no need for barium nitrate to remove sulfur in advance, which simplifies the preparation process.

[0022] (5) Achieve zero discharge and full resource utilization of wastewater. The process of this invention does not generate new wastewater discharge. All wastewater is converted into gel and finally made into glass products. The resulting glass frit can be used as glaze or directly as glass raw material, thus achieving zero discharge of electroplating wastewater and reuse of its beneficial resources, avoiding the generation of solid waste and secondary pollution. Detailed Implementation

[0023] The following specific embodiments provide a more detailed description of the present invention. These embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0024] In the following examples and comparative examples, the electroplating wastewater containing heavy metal ions used was from a company's waste electroplating solution. The basic characteristics of the wastewater were: chromium 312.4 mg / L, zinc 272.2 mg / L, calcium 119.9 mg / L, sulfur 98.6 mg / L, magnesium 27.8 mg / L, sodium 30.5 mg / L, phosphorus 26 mg / L, and pH between 3.6 and 3.7. The basic characteristics of the phosphorus-containing electroplating wastewater used were: sodium 375 mg / L, phosphorus 204.2 mg / L, sulfur 178.3 mg / L, calcium 174.6 mg / L, magnesium 32.5 mg / L, and pH between 6.5 and 6.6.

[0025] In the following examples and comparative examples, the modulus of the water glass used is 3.3.

[0026] In the following examples and comparative examples, to maintain consistency of experimental conditions, a xenon lamp was used to simulate sunlight, and the intensity was set to one times the solar irradiance (100 mW / cm²). 2 However, the present invention is not limited to this lighting condition.

[0027] Example 1 (1) Add 2.5 mL of water glass to 25 mL of electroplating wastewater containing heavy metal ions and stir for 5 min; (2) While stirring, add 3 mL of 15 wt% ferrous sulfate solution to the above solution, mix thoroughly, and then add 0.05 g of activated carbon. (3) After thorough stirring, place the mixture in step (2) under a simulated light source to dry until the weight no longer changes. (4) Transfer the dry gel solid from step (3) to an alumina crucible and heat it in a high-temperature furnace. Heat it to 1500°C at 5°C / min and keep it at that temperature for 2 hours. Pour the resulting glass melt into water for water quenching to obtain a glass molten block.

[0028] Example 2 The glass frit was prepared according to the method of Example 1, except that in step (2), the amount of activated carbon added was 0.1g.

[0029] Example 3 (1) Add 2.5 mL of water glass to 25 mL of phosphorus-containing electroplating wastewater and stir for 5 min; (2) While stirring, add 0.3 mL of 85 wt% phosphoric acid solution to the above solution, mix thoroughly, and then add 0.25 g of activated carbon and 0.125 g of halloysite in sequence; (3) After thorough stirring, place the mixture in step (2) under a simulated light source to dry until the weight no longer changes. (4) Transfer the dry gel solid from step (3) to an alumina crucible and heat it in a high-temperature furnace. Heat it to 1550°C at 5°C / min and keep it at that temperature for 2 hours. Pour the resulting glass melt into water for water quenching to obtain a glass molten block.

[0030] Example 4 The glass frit was prepared according to the method of Example 3, except that in step (2), the amount of 85wt% phosphoric acid solution added was 0.15mL.

[0031] Comparative Example 1 (1) Add 2.5 mL of water glass to 25 mL of electroplating wastewater containing heavy metal ions and stir for 5 min; (2) While stirring, continue to add 3 mL of ferrous sulfate with a mass fraction of 15 wt% to the above solution and mix thoroughly. (3) After thorough stirring, place the mixture in step (2) under a simulated light source to dry until the weight no longer changes. (4) Transfer the dry gel solid from step (3) to an alumina crucible and heat it in a high-temperature furnace. Increase the temperature to 1500℃ at 5℃ / min and hold for 2 hours. Pour out the high-temperature melt directly. A mixture of yellow and black solids will appear. This is because the excess sulfate did not completely decompose during the melting process, producing nitrate water. Therefore, water quenching is not allowed, otherwise an explosion will occur.

[0032] Comparative Example 2 (1) Add 2.5 mL of water glass to 25 mL of phosphorus-containing electroplating wastewater and stir for 5 min; (2) While stirring, add 0.3 mL of 85 wt% phosphoric acid solution to the above solution, mix thoroughly, and then add 0.25 g of activated carbon and 0.25 g of halloysite in sequence; (3) After thorough stirring, place the mixture in step (2) under a simulated light source to dry until the weight no longer changes. (4) The dry gel solid in step (3) is transferred to an alumina crucible and heated in a high-temperature furnace. The temperature is increased to 1550°C at 5°C / min and then kept at that temperature for 2 hours. Finally, a solid containing black and gray inclusions is formed, which cannot form a uniform melt.

[0033] Comparative Example 3 (1) Add 2.5 mL of water glass to 25 mL of phosphorus-containing electroplating wastewater and stir for 5 min; (2) While stirring, add 0.3 mL of 85 wt% phosphoric acid solution to the above solution, mix thoroughly, and then add 0.25 g of activated carbon. (3) After thorough stirring, place the mixture in step (2) under a simulated light source to dry until the weight no longer changes. (4) Transfer the dry gel solid from step (3) to an alumina crucible and heat it in a high-temperature furnace. Heat it to 1550°C at 5°C / min and hold it for 2 hours. The resulting melt is water-soluble and cannot be made into glass frit by water quenching.

[0034] Comparative Example 4 (1) Add 5 mL of water glass to 50 mL of phosphorus-containing electroplating wastewater and stir for 5 min; (2) While stirring, add 0.6 mL of 85 wt% phosphoric acid solution to the above solution, mix thoroughly, and then add 0.5 g of activated carbon; (3) After thorough stirring, the mixture from step (2) was dried in a simulated light source and a 50°C oven, respectively. The mixture dried in the 50°C oven reached constant weight in about 114 hours, while it only took about 36 hours to reach constant weight under simulated light source irradiation. This shows that the method of the present invention greatly improves the drying speed of the gel.

Claims

1. A method for preparing a glass frit, characterized in that, Includes the following steps: (1) Add water glass, acidic solution and activated carbon to the electroplating wastewater in sequence, and mix them evenly under stirring conditions; (2) Place the mixture from step (1) under sunlight to dry until a dry gel is formed and constant weight is achieved; (3) The dry gel obtained in step (2) is melted at high temperature, and the resulting melt is quenched in water to obtain a glass frit.

2. The preparation method according to claim 1, characterized in that, The electroplating wastewater contains phosphorus, or one or more heavy metal ions from chromium, nickel, copper, and zinc, as well as sulfate ions.

3. The preparation method according to claim 1, characterized in that, The volume ratio of electroplating wastewater to water glass is 25:2-3; preferably, the modulus of the water glass is 3.2-3.

5.

4. The preparation method according to claim 1, characterized in that, The acidic solution is a sulfate solution or a phosphoric acid solution; preferably, the concentration of the sulfate solution is 10-20 wt%, and the concentration of the phosphoric acid solution is 80-85 wt%.

5. The preparation method according to claim 4, characterized in that, The sulfate solution is a ferrous sulfate solution.

6. The preparation method according to claim 1, 4, or 5, characterized in that, The amount of acidic solution used is 0.6~12% of the volume of electroplating wastewater.

7. The preparation method according to claim 4, characterized in that, When the added acidic solution is phosphoric acid solution, add activated carbon first, then add halloysite powder; preferably, add 0.4-0.6g halloysite powder per 100ml of electroplating wastewater.

8. The preparation method according to claim 1, characterized in that, The ratio of activated carbon to electroplating wastewater is 0.05~0.25g:25ml.

9. The preparation method according to claim 1, characterized in that, The melting temperature for high-temperature melting is 1500~1550℃, and the holding time is 2-3 hours.

10. A glass frit prepared according to any one of claims 1-9.