BDG-containing dewaxing sewage treatment method

Abstract

The invention relates to the technical field of industrial sewage treatment, in particular to a BDG-containing dewaxing sewage treatment method. The treatment method comprises the following steps: S1, adding sodium carbonate powder into sewage, and stirring until sodium carbonate is in a dissolved saturated state or a dissolved supersaturated state in a mixed solution; s2, standing the mixed solution to obtain a layered mixed solution; s3, performing liquid separation on the layered mixed liquid to obtain first waste liquid originally placed on the upper layer of the layered mixed liquid and second waste liquid originally placed on the lower layer of the layered mixed liquid; and S4, respectively treating the first waste liquid and the second waste liquid. According to the method, the BDG-containing dewaxing sewage is simply treated to form the first waste liquid mainly containing organic substances and the second waste liquid mainly containing inorganic substances, the two waste liquids can be separately subjected to subsequent sewage treatment work, and the second waste liquid with a large proportion can be used as inorganic waste liquid for sewage treatment; further, the total sewage treatment cost of the BDG-containing dewaxing sewage is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment, and in particular to a method for treating BDG-containing dewaxing wastewater. Background Art

[0002] Compared with traditional exposure and development technology, inkjet printing technology is simpler in process and cheaper in cost, so it is gradually being widely used in the photovoltaic field. In the process of using inkjet printing technology, the mask layer on the raw material needs to be removed.

[0003] For example, the patent with application number 202410857737.9 provides a mask removal process. The mask layer material targeted by this process is a hot-melt material. This process first uses a high-temperature oven to pre-treat the silicon wafer so that most of the hot-melt material can be melted and then recycled. Then, the silicon wafer is treated with hot water ultrasound combined with bubbling to remove part of the hot-melt material. The remaining trace hot-melt material is then removed using alkaline solution (a mixed solution of BDG and KOH or BDG and NaOH). In the BDG-containing dewaxing agent used in this patent, BDG plays the main role of dissolving wax, while alkalis such as sodium hydroxide play the role of destroying the molecular chains in the wax. The synergy between the two can effectively remove the mask layer made of wax. Therefore, after the mask is removed using this process, dewaxing wastewater containing BDG is inevitably produced.

[0004] The composition of this wastewater is relatively complex, containing inorganic substances such as residual potassium hydroxide and sodium hydroxide, as well as organic substances such as diethylene glycol monobutyl ether (BDG) and wax. Therefore, this wastewater is usually used as organic wastewater in subsequent wastewater treatment. On the one hand, the total amount of such organic wastewater generated in the mask removal process is large; on the other hand, the cost per ton of treatment of organic wastewater is high and much higher than the cost per ton of treatment of inorganic wastewater. The above reasons combined lead to the fact that if the BDG-containing dewaxing agent is to be used in the mask removal process, the total cost of wastewater treatment will remain high, which also makes it difficult for such dewaxing agents to be further promoted and used. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for treating BDG-containing dewaxing wastewater, in which low-cost chemical agents are used to carry out preliminary treatment of the above-mentioned wastewater with complex components, and the organic matter therein is separated from the inorganic matter as much as possible, so that the total amount of organic waste liquid that needs to be treated in the end is reduced, thereby reducing the overall wastewater treatment cost.

[0006] The present invention is achieved through the following technical solutions: A method for treating BDG-containing dewaxing wastewater comprises the following steps: S1. adding sodium carbonate powder to wastewater and stirring until the sodium carbonate is in a saturated or supersaturated state in a mixed liquid; S2. allowing the mixed liquid to stand to obtain a layered mixed liquid; S3. separating the layered mixed liquid to obtain a first waste liquid originally placed in an upper layer of the layered mixed liquid and a second waste liquid originally placed in a lower layer of the layered mixed liquid; S4. performing waste liquid treatment on the first waste liquid and the second waste liquid respectively.

[0007] The saturated state refers to the state in which the amount of sodium carbonate dissolved in the mixed solution reaches the maximum. If more sodium carbonate is added, it will be difficult to dissolve again and sodium carbonate precipitation will be produced; the supersaturated state refers to the state in which the amount of sodium carbonate powder dissolved in the mixed solution reaches the maximum and sodium carbonate precipitation has been produced at the bottom of the mixed solution.

[0008] As a further improvement of the present invention, between S3 and S4, the steps S1 to S3 are repeated 2 to 3 times for the second waste liquid obtained by layering, during which the first waste liquid obtained by separation is collected for unified treatment.

[0009] As a further improvement of the present invention, in S2, the mixed solution is allowed to stand for 1 to 10 minutes to obtain the layered mixed solution.

[0010] As a further improvement of the present invention, in S1, bubbling stirring treatment is performed during the process of adding sodium carbonate powder to the sewage.

[0011] As a further improvement of the present invention, in S4, the first waste liquid is distilled to recover BDG.

[0012] As a further improvement of the present invention, the distillation temperature is 230.5-231.5°C.

[0013] As a further improvement of the present invention, in S4, the second waste liquid is subjected to acid-base neutralization treatment.

[0014] As a further improvement of the present invention, the BDG-containing dewaxing wastewater contains BDG, a strong alkali and wax.

[0015] As a further improvement of the present invention, the strong base is any one or more combinations of sodium hydroxide or potassium hydroxide.

[0016] As a further improvement of the present invention, the wax is a combination of any one or more of paraffin wax, acrylate, C11-C22 alkyl acid, polypropylene wax, microcrystalline wax, polyethylene wax, and ethylene-vinyl acetate copolymer wax.

[0017] The beneficial effects of the present invention are: First of all, the BDG-containing dewaxed wastewater itself, which is the treatment object of the present invention, has a relatively complex chemical agent content, including organic substances composed of BDG, wax, etc., and inorganic substances such as sodium hydroxide and / or potassium hydroxide. Therefore, the BDG-containing dewaxed wastewater will be used as an organic waste liquid for subsequent sewage treatment, and the treatment cost of organic waste liquid is usually much higher than the treatment cost of inorganic waste liquid, which leads to a high total treatment cost of the BDG-containing dewaxed wastewater. The present invention separates organic substances such as BDG and wax from other inorganic substances such as alkali, and forms a first waste liquid mainly composed of organic substances such as BGD and wax and a second waste liquid mainly composed of inorganic substances such as alkali after simple treatment of the BDG-containing dewaxed wastewater. The two waste liquids can be separated for subsequent sewage treatment, and the second waste liquid, which accounts for a larger proportion, can be used as an inorganic waste liquid for sewage treatment, thereby greatly reducing the total sewage treatment cost of the BDG-containing dewaxed wastewater.

[0018] In the scheme of the invention, the inventors found through experiments that dissolving a sufficient amount of sodium carbonate into sewage and leaving it to stand can drive the sewage to stratify. Testing the two mixed liquids after stratification shows that the liquid originally placed on the top of the stratified mixed liquid after stratification is the first waste liquid mainly containing wax and BDG, while the liquid originally placed at the bottom of the stratified mixed liquid is the second waste liquid mainly containing alkali. In addition, the inventors ruled out the influence of simple sodium ions or carbonate ions on the stratification phenomenon through further testing, and determined that the above effect can only be achieved after sufficient sodium carbonate is dissolved in the wastewater.

[0019] The inventors have obtained a method for treating BDG-containing dewaxing wastewater through experiments. The steps are relatively simple and easy to operate. The reagents used are easily available and cheap, which greatly reduces the cost of treating the complex wastewater, and is conducive to the promotion and use of the method. At the same time, as a further preference, the user can also recycle and reuse the BDG in the separated first waste liquid by distillation, which reduces the cost of using the BDG-containing dewaxing reagent for the manufacturer and can further promote the widespread use of the BDG-containing dewaxing reagent. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following drawings are provided for combining with the preferred implementation examples of the present invention to help understand the purpose and advantages of the present invention, wherein: Figure 1 This is a photo of the dewaxed wastewater containing BDG; Figure 2 This is a photo of the BDG-containing dewaxed wastewater after a single treatment; Figure 3 This is a photo of the BDG-containing dewaxed wastewater after secondary treatment; Figure 4 This is a photo of the mixed solution after adding paraffin into the BDG solution; Figure 5This is a photo of the mixed solution after adding paraffin wax to the alkaline solution; Figure 6 This is a picture of the mixed liquid after adding paraffin to the second waste liquid; Figure 7 This is a photo of BDG-containing dewaxing wastewater when the amount of sodium carbonate added does not reach the dissolution saturation state; Figure 8 This is a photo of BDG dewaxing wastewater after adding sodium chloride; Fig. 9 This is a photo of BDG dewaxing wastewater after adding ammonium carbonate; Fig.10 This is a photo of BDG dewaxing wastewater after adding sodium bicarbonate; Fig.11 This is a photo of BDG dewaxing wastewater after adding ferric chloride; Fig.12 This is a photo of BDG dewaxing wastewater after adding copper chloride; Fig.13 This is a photo of BDG dewaxing wastewater after adding ammonium chloride. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below based on the accompanying drawings and implementation examples.

[0022] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] The BDG-containing dewaxing wastewater is mainly formed by dissolving the mask layer on the battery cell with the BDG-containing dewaxing agent. In this embodiment, the BDG-containing dewaxing agent is prepared by dissolving 30g of sodium hydroxide and 150ml of BDG in 2L of water. The mask layer removed by the BDG-containing dewaxing agent is composed of paraffin.

[0024] The discharge standards for treated sewage in this embodiment refer to the relevant requirements in the "Comprehensive Sewage Discharge Standard" (GB8978-1996).

[0025] Embodiment 1: This embodiment provides a method for treating BDG-containing dewaxing wastewater, which mainly comprises the following steps: S1. Pour the sewage to be treated into the container and observe the sewage condition. Figure 1As shown in . Then, sodium carbonate powder is continuously added to the sewage and stirred until the sodium carbonate in the mixed solution is in a supersaturated state of dissolution. In this embodiment, it is observed that sodium carbonate precipitation still exists at the bottom of the sewage after continuous stirring; S2. The above-mentioned mixture is allowed to stand to obtain a layered mixture; S3. In this embodiment, a separatory funnel is used to separate the layered mixed liquid to obtain two waste liquids, wherein the first waste liquid is originally placed on the upper layer of the layered mixed liquid, and the second waste liquid is originally placed on the lower layer of the layered mixed liquid; S4. Treat the first waste liquid and the second waste liquid separately, wherein the first waste liquid is mainly composed of organic substances such as BDG and wax, while the second waste liquid is mainly composed of inorganic substances such as sodium hydroxide. There are relatively mature existing treatment schemes for the two waste liquids obtained after separation. For example, the first waste liquid can be degraded by Fenton reagent method to meet the sewage discharge standard before discharge; the second waste liquid can be treated by neutralization method, precipitation method, etc. to meet the sewage discharge standard before discharge.

[0026] Preferably, in this embodiment, in step S1, bubbling treatment may be performed while the sodium carbonate powder is being dissolved, so as to improve the dissolution efficiency of the sodium carbonate powder.

[0027] Preferably, before the first waste liquid and the second waste liquid are finally treated in S4, the steps of S1 to S3 can be repeated twice for the second waste liquid to ensure that most of the BDG in the second waste liquid has been transferred to the newly formed upper first waste liquid, and the first waste liquid obtained by the repeated operation is uniformly collected after the liquid separation step for subsequent treatment. At the same time, the standing time of the mixed liquid in S2 can be selected as 2 min to improve the overall efficiency of the treatment method.

[0028] like Figure 4 As shown in the figure, when paraffin is dissolved in BDG solution, the whole solution will be a yellow clear solution. Generally, both sodium hydroxide aqueous solution and BDG solution are colorless and transparent liquids. Therefore, the inventors speculate that when the mixed solution contains both paraffin and BDG solution, the color of the solution will change to yellow, and the color depth can be used to roughly judge the content of BDG and wax in the mixed solution.

[0029] After adding sodium carbonate reagent once until it is dissolved to saturation, and standing for 24 hours, the second waste liquid obtained at the lower layer can also be colorless and transparent.

[0030] But if Figure 2 As shown in the figure, when the standing time is short and only a single separation is performed, the waste liquid at the bottom still appears light yellow. Then, when the sodium carbonate powder is added to the waste liquid at the bottom for the second time until the sodium carbonate is supersaturated, as shown in the figure, Figure 3As shown, stratification occurred again in the waste liquid, and after the new stratification, the waste liquid at the bottom was closer to a colorless state as a whole. This phenomenon, on the one hand, verifies the above-mentioned speculation of the inventor, that is, the color depth of the solution is related to the residual degree of BDG and wax. On the other hand, it also shows that when a single sodium carbonate dissolution is supersaturated and the standing time is short, there are still BDG and wax remaining in the waste liquid at the bottom. According to further experiments by the inventor, if the above steps are repeated many times, the liquid will hardly be stratified, and the color change in the waste liquid at the bottom will be difficult to be detected by the naked eye. The two results confirm each other, indicating that most of the organic substances such as BDG and wax in the BDG-containing dewaxing wastewater have been separated into the upper waste liquid.

[0031] Therefore, in this embodiment, it is preferred to adopt a form of a short standing time and repeat the steps of adding sodium carbonate twice until it is dissolved in a supersaturated state, so as to improve the treatment efficiency of sewage and ensure that most of the organic substances such as BDG and wax can be separated.

[0032] Preferably, the first waste liquid obtained by separation can be distilled to recover BDG therein. In this embodiment, under standard atmospheric pressure, the distillation temperature is controlled to be 230.5-231.5° C., and BDG can be recovered by distillation, wherein the recovery rate of BDG can be ≥90%.

[0033] Preferably, in this embodiment, the second waste liquid obtained by separation mainly contains inorganic substances such as sodium hydroxide remaining after dewaxing in the BDG dewaxing agent, so the second waste liquid is mainly subjected to acid-base neutralization treatment until it meets the sewage discharge standard.

[0034] Waste liquid detection: This step is used to detect the main components in the waste liquid after stratification to prove that BDG and wax have indeed been transferred. The main detection method used is the paraffin drop detection method.

[0035] This method is mainly based on the following principles: First, paraffin is difficult to dissolve in water. Usually paraffin is difficult to dissolve directly in water, but it can be dissolved in BDG aqueous solution, and Figure 4 As shown in , when paraffin is dissolved in BDG aqueous solution, the mixture is a yellow clear solution. Second, paraffin will undergo saponification reaction when it encounters alkali. Paraffin will undergo saponification reaction when it enters the alkaline solution, such as Figure 5 As shown, the solution will gradually become turbid and viscous. Third, when a large amount of BDG and alkali are present in the mixture, paraffin will be dissolved first rather than saponified. Figure 1As shown, the BDG-containing dewaxing wastewater is a clear solution as a whole. In the above principle, the color and transparency changes of the liquid can be directly observed by the naked eye. Therefore, the paraffin drop detection method is mainly based on observing the color and transparency changes of the liquid of the object to be detected after adding paraffin to the object to be detected to determine the content of BDG and alkali in the object to be detected.

[0036] The BDG-containing dewaxed wastewater to be treated in the present invention mainly contains wax, BDG and alkali. After liquid separation, the first waste liquid mainly contains wax and BDG, while the second waste liquid mainly contains alkali with only a very small amount of organic substances such as BDG remaining. Therefore, in this embodiment, when performing the test, it is only necessary to drop paraffin into the second waste liquid and observe the color and transparency of the second waste liquid to know whether a large amount of BDG solution is still retained in the second waste liquid, and therefore it is also possible to know whether the separation of BDG occurs.

[0037] Test results display: Figure 1 The figure shows the BDG-containing dewaxing wastewater, which can be equivalent to a mixture of water containing a large amount of BDG and a large amount of alkali, and then adding paraffin. It can be intuitively found from the attached figure that in this case, the mixed liquid is generally a yellow clear liquid without obvious turbidity.

[0038] Figure 4 The mixed solution after adding paraffin to the BDG solution is shown. It can be intuitively found from the attached figure that the mixed solution is still a yellow clear liquid as a whole, and there is no turbidity. Figure 1 and Figure 2 It can be confirmed that when a large amount of BDG and alkali exist in the mixed solution at the same time, paraffin is dissolved first, so the mixed solution is basically a yellow clear liquid.

[0039] and Figure 6 The shown is taken from Figure 3 The mixed liquid after adding paraffin to the second waste liquid at the bottom. It can be seen from the attached figure that the mixed liquid is obviously turbid, which means that the paraffin has mainly produced a saponification reaction with the residual sodium hydroxide in the second waste liquid. On the one hand, this result shows that paraffin is no longer preferentially dissolved, and the content of BDG in the second waste liquid is much less than that of sodium hydroxide; on the other hand, since the second waste liquid at the bottom is taken from Figure 3 If wax still exists in the second waste liquid, it cannot be kept as Figure 3 The colorless and clear state shown in the figure also indicates that the wax content in the second waste liquid is extremely low or absent.

[0040] Therefore, the above test results indicate that the treatment method of the present invention successfully separates organic substances such as BDG.

[0041] Comparative Example 1: The difference between this comparative example and Example 1 is that in this comparative example, sodium carbonate is added to the sewage but the sodium carbonate is not dissolved to a saturated state.

[0042] Comparative Example 2: The difference between this comparative example and Example 1 is that in this comparative example, sodium chloride is added to the sewage. If the sewage does not produce stratification, the subsequent steps are not carried out.

[0043] Comparative Example 3: The difference between this comparative example and Example 1 is that in this comparative example, sodium bicarbonate is added to the sewage. If the sewage does not produce stratification, the subsequent steps are not carried out.

[0044] Comparative Example 4: The difference between this comparative example and Example 1 is that in this comparative example, ammonium carbonate is added to the sewage. If the sewage does not produce stratification, the subsequent steps are not carried out.

[0045] Comparative Example 5: The difference between this comparative example and Example 1 is that in this comparative example, ferric chloride is added to the sewage. If the sewage does not produce stratification, the subsequent steps are not carried out.

[0046] Comparative Example 6: The difference between this comparative example and Example 1 is that in this comparative example, copper chloride is added to the sewage. If the sewage does not produce stratification, the subsequent steps are not carried out.

[0047] Comparative Example 7: The difference between this comparative example and Example 1 is that in this comparative example, ammonium chloride is added to the sewage. If the sewage does not produce stratification, the subsequent steps are not carried out.

[0048] Comparative proportion analysis: Figures 7 to 13 The changes of BDG-containing dewaxing wastewater after adding various reagents in Comparative Examples 1 to 7 are shown respectively. Figure 7 The results show that when the amount of sodium carbonate added does not reach the saturated state of dissolution, no obvious stratification will occur in the BDG-containing dewaxing wastewater, and the treatment method of the present invention is difficult to advance. Figures 8 and 9 It can be seen from the results in that whether the introduction of sodium ions or carbonate ions alone will not cause obvious stratification in the BDG-containing dewaxing wastewater; Fig.10 The results of adding sodium bicarbonate show that even the combination of sodium ions and bicarbonate ions is difficult to achieve smooth stratification of BDG-containing dewaxing wastewater. Figures 11 to 13The test results of adding ferric chloride, cupric chloride and ammonium chloride ruled out the influence of other common metal ions, ammonium ions and halogen anions represented by chloride ions on the stratification phenomenon of BDG-containing dewaxing wastewater.

[0049] Therefore, based on the above test results, the inventors summarized the BDG-containing dewaxing wastewater treatment method shown in the present invention, using sodium carbonate as the core treatment agent to achieve stratification of BDG-containing dewaxing wastewater, and separate BDG and wax from the wastewater, leaving only the second wastewater that can participate in the treatment of inorganic wastewater. At the same time, the BDG in the first waste liquid can also be distilled and recovered for reuse, which generally reduces the corresponding use cost of the BDG-containing dewaxing agent.

[0050] Finally, it should be noted that the above implementation cases are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned implementation cases, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned implementation cases, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the implementation cases of the present invention.

Claims

1. A method for treating BDG-containing dewaxing wastewater, characterized in that: The following steps are involved: S1. Continuously add sodium carbonate powder to the sewage and stir until the sodium carbonate is dissolved in the mixed solution in a saturated state or in a supersaturated state; S2. The mixed solution is allowed to stand to obtain a layered mixed solution; S3. The layered mixed liquid is separated to obtain a first waste liquid originally placed on the upper layer of the layered mixed liquid and a second waste liquid originally placed on the lower layer of the layered mixed liquid; S4. Perform waste liquid treatment on the first waste liquid and the second waste liquid respectively.

2. A method for treating BDG-containing dewaxing wastewater according to claim 1, characterized in that: Between S3 and S4, the steps in S1 to S3 are repeated 2 to 3 times for the second waste liquid obtained by layering, during which the first waste liquid obtained by separation is collected for unified treatment.

3. A method for treating BDG-containing dewaxing wastewater according to claim 2, characterized in that: In S2, the mixed solution is allowed to stand for 1 to 10 minutes to obtain the layered mixed solution.

4. The method for treating BDG-containing dewaxing wastewater according to claim 1, characterized in that: In S1, during the process of adding sodium carbonate powder to the sewage, bubbling and stirring treatment is performed.

5. A method for treating BDG-containing dewaxing wastewater according to claim 1, characterized in that: In S4, the first waste liquid is subjected to distillation treatment to recover BDG.

6. A method for treating BDG-containing dewaxing wastewater according to claim 5, characterized in that: The distillation temperature is 230.5~231.5℃.

7. The method for treating BDG-containing dewaxing wastewater according to claim 1, characterized in that: In S4, the second waste liquid is subjected to acid-base neutralization treatment.

8. The method for treating BDG-containing dewaxing wastewater according to claim 1, characterized in that: The BDG-containing dewaxing wastewater contains BDG, strong alkali and wax.

9. A method for treating BDG-containing dewaxing wastewater according to claim 8, characterized in that: The strong base is any one or more of sodium hydroxide and potassium hydroxide.

10. The method for treating BDG-containing dewaxing wastewater according to claim 8, characterized in that: The wax is any one or more of paraffin wax, acrylate, C11-C22 alkyl acid, polypropylene wax, microcrystalline wax, polyethylene wax, and ethylene-vinyl acetate copolymer wax.

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