A method for treating wastewater containing BDG de-waxing

Abstract

The present application relates to the technical field of industrial wastewater treatment, and particularly relates to a method for treating BDG-containing dewaxing wastewater. The method comprises the following steps: S1. adding sodium carbonate powder into the wastewater and stirring until the sodium carbonate is in a saturated or supersaturated state in the mixed solution; S2. allowing the mixed solution to stand to obtain a layered mixed solution; S3. separating the layered mixed solution to obtain a first waste liquid originally placed in the upper layer of the layered mixed solution and a second waste liquid originally placed in the lower layer of the layered mixed solution; and S4. separately treating the first waste liquid and the second waste liquid. The BDG-containing dewaxing wastewater is treated to form a first waste liquid mainly containing organic substances and a second waste liquid mainly containing inorganic substances, and the two kinds of waste liquids can be separately treated in subsequent wastewater treatment, and the second waste liquid with a larger proportion can be treated as inorganic waste liquid, thereby greatly reducing the overall wastewater treatment cost of the BDG-containing dewaxing wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater treatment, in particular to a BDG-containing dewaxing wastewater treatment method. BACKGROUND

[0002] Inkjet printing technology is a technology that is simpler in process and lower in cost than traditional exposure and development technology, and therefore gradually widely used in the photovoltaic field. In the use process of inkjet printing technology, the mask layer on the raw material needs to be removed.

[0003] A mask removal process is provided in the patent with application number 202410857737.9. The mask layer material targeted by this process is hot melt material. This process first uses a high-temperature oven to pretreat the silicon wafer, so that most of the hot melt material can be melted and recycled. Then, the silicon wafer is treated with hot water and ultrasonic waves combined with bubbling to remove part of the hot melt material. The remaining trace amount of hot melt material is removed using an alkali solution (a mixed solution of BDG and KOH or BDG and NaOH). In the BDG-containing dewaxing reagent used in this patent, BDG plays a major role in dissolving wax, and alkali such as sodium hydroxide plays a role in destroying the molecular chain of wax. The two work together to effectively remove the mask layer made of wax. Therefore, after using this process to remove the mask, BDG-containing dewaxing wastewater is inevitably produced.

[0004] The composition of this wastewater is complex, containing not only residual inorganic substances such as potassium hydroxide and sodium hydroxide, but also organic substances such as diethylene glycol monobutyl ether (BDG) and wax. Therefore, this wastewater is usually treated as organic wastewater in subsequent wastewater treatment. On the one hand, the total amount of such organic wastewater produced in the mask removal process is large. On the other hand, the treatment cost of each ton of organic wastewater is high and much higher than that of inorganic wastewater. The above reasons combined result in a high total cost of wastewater treatment if the BDG-containing dewaxing reagent is used in the mask removal process. This phenomenon also makes it difficult to further promote the use of such dewaxing reagent. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a BDG-containing dewaxing wastewater treatment method. In this method, a low-cost chemical reagent is used to preliminarily treat the wastewater with complex composition, so as to separate the organic substances from the inorganic substances as much as possible, thereby reducing the total amount of organic wastewater to be treated and reducing the overall wastewater treatment cost.

[0006] The present application is realized by the following technical solutions:

[0007] The application discloses a method for treating BDG-containing de-waxing wastewater, which comprises the following steps: S1, adding sodium carbonate powder into the wastewater and stirring until the sodium carbonate is in a dissolved saturated state or a dissolved supersaturated state in the mixed solution; S2, standing the mixed solution to obtain a layered mixed solution; S3, separating the layered mixed solution to obtain a first waste liquid originally placed in the upper layer of the layered mixed solution and a second waste liquid originally placed in the lower layer of the layered mixed solution; and S4, respectively treating the first waste liquid and the second waste liquid.

[0008] The dissolved saturated state refers to that the dissolved amount of the sodium carbonate in the mixed solution reaches the maximum, and if the sodium carbonate is continuously added, the sodium carbonate is difficult to be dissolved again and will be precipitated; and the dissolved supersaturated state refers to that the dissolved amount of the sodium carbonate powder in the mixed solution reaches the maximum and the sodium carbonate is precipitated at the bottom of the mixed solution.

[0009] As a further improvement of the application, between S3 and S4, the second waste liquid obtained by layering is repeatedly subjected to steps 2-3 in S1-S3 for 2-3 times, and the first waste liquid obtained by separation is collected for unified treatment.

[0010] As a further improvement of the application, in S2, the mixed solution is stood for 1-10 min to obtain the layered mixed solution.

[0011] As a further improvement of the application, in S1, during the process of adding the sodium carbonate powder into the wastewater, bubble stirring treatment is performed.

[0012] As a further improvement of the application, in S4, the first waste liquid is subjected to distillation treatment to recover the BDG.

[0013] As a further improvement of the application, the distillation temperature is 230.5-231.5 DEG C.

[0014] As a further improvement of the application, in S4, the second waste liquid is subjected to acid-base neutralization treatment.

[0015] As a further improvement of the application, the BDG-containing de-waxing wastewater contains BDG, a strong alkali and wax.

[0016] As a further improvement of the application, the strong alkali is any one or a combination of the following: sodium hydroxide or potassium hydroxide.

[0017] As a further improvement of the application, the wax is any one or a combination of the following: paraffin wax, acrylate, C11-C22 alkyl acid, polypropylene wax, microcrystalline wax, polyethylene wax and ethylene-vinyl acetate copolymer wax.

[0018] The application has the following beneficial effects:

[0019] Firstly, the BGD-containing dewaxing wastewater as the processing object of the present application itself has a relatively complex chemical agent content, which contains not only organic substances such as BGD and wax, but also inorganic substances such as sodium hydroxide and / or potassium hydroxide. Therefore, the BGD-containing dewaxing wastewater will be treated as organic waste liquid for subsequent wastewater treatment, and the treatment cost of the organic waste liquid is usually much higher than that of the inorganic waste liquid, thereby resulting in a relatively high total cost of the BGD-containing dewaxing wastewater treatment. However, in the present application, the BGD and wax and other organic substances are separated from other inorganic substances such as alkali, and the BGD-containing dewaxing wastewater is treated to form a first waste liquid mainly containing BGD and wax and a second waste liquid mainly containing alkali. The two waste liquids can be separately treated for subsequent wastewater treatment, and the second waste liquid with a large proportion can be treated as inorganic waste liquid for wastewater treatment, thereby greatly reducing the total cost of the BGD-containing dewaxing wastewater treatment.

[0020] In the present application, the inventors found through experiments that after a sufficient amount of sodium carbonate is dissolved into the wastewater and left to stand, the wastewater can be caused to stratify. Detection of the two mixed liquids after stratification shows that the liquid originally placed at the top of the stratified mixed liquid is a first waste liquid mainly containing wax and BGD, and the liquid originally placed at the bottom of the stratified mixed liquid is a second waste liquid mainly containing alkali. In addition, the inventors excluded the influence of sodium ions or carbonate ions alone on the stratification phenomenon through further detection, and determined that the above-mentioned effect can only be achieved after a sufficient amount of sodium carbonate is dissolved in the wastewater.

[0021] The BGD-containing dewaxing wastewater treatment method obtained through experiments by the inventors is generally simple and easy to operate, and the reagents used are easily available and inexpensive, which greatly reduces the treatment cost of the complex wastewater and is conducive to the popularization and use of the method. Meanwhile, as a further preferred embodiment, the user can also recycle and reuse the BGD in the first waste liquid separated by distillation, which can reduce the use cost of the BGD-containing dewaxing reagent for manufacturers and further promote the widespread use of the BGD-containing dewaxing reagent. BRIEF DESCRIPTION OF DRAWINGS

[0022] The following drawings are provided to assist in the understanding of the objects and advantages of the present application in combination with the preferred embodiments of the present application, wherein:

[0023] Figure 1 is a photo of BGD-containing dewaxing wastewater;

[0024] Figure 2 is a photo of BGD-containing dewaxing wastewater after single treatment;

[0025] Figure 3 is a photo of BGD-containing dewaxing wastewater after secondary treatment;

[0026] Figure 4 Picture of the mixture after adding paraffin to the BDG solution;

[0027] Figure 5 Picture of the mixture after adding paraffin to the alkali solution;

[0028] Figure 6 Picture of the mixture after adding paraffin to the second waste liquid;

[0029] Figure 7 Picture of the BDG wax removal wastewater when the amount of sodium carbonate added does not reach the saturated state of dissolution;

[0030] Figure 8 Picture of the BDG wax removal wastewater after adding sodium chloride;

[0031] Figure 9 Picture of the BDG wax removal wastewater after adding ammonium carbonate;

[0032] Figure 10 Picture of the BDG wax removal wastewater after adding sodium bicarbonate;

[0033] Figure 11 Picture of the BDG wax removal wastewater after adding ferric chloride;

[0034] Figure 12 Picture of the BDG wax removal wastewater after adding copper chloride;

[0035] Figure 13 Picture of the BDG wax removal wastewater after adding ammonium chloride. DETAILED DESCRIPTION

[0036] The present application will be further described in detail with reference to the accompanying drawings and examples.

[0037] In order to make the purpose, technical solutions and advantages of the present application more clear and explicit, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, rather than all examples. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0038] The BDG-containing wax removal wastewater is mainly formed after the BDG-containing wax removal agent dissolves the mask layer on the battery piece. In this example, the BDG-containing wax removal agent used is prepared by dissolving 30 g of sodium hydroxide and 150 ml of BDG in 2 L of water. The mask layer removed by the BDG-containing wax removal agent is composed of paraffin.

[0039] In this example, the discharge standards after wastewater treatment are all based on the relevant requirements in the "Integrated Wastewater Discharge Standard" (GB 8978-1996).

[0040] Example 1:

[0041] This embodiment provides a method for treating BDG-containing dewaxing wastewater, which mainly includes the following steps:

[0042] S1. Pour the wastewater to be treated into the container and observe that the wastewater condition is as follows: Figure 1 As shown in the figure. Sodium carbonate powder is then continuously added to the wastewater and stirred until the sodium carbonate in the mixture is in a supersaturated state. In this embodiment, it is observed that sodium carbonate precipitate still exists at the bottom of the wastewater after continuous stirring.

[0043] S2. After the above mixture is allowed to stand, a layered mixture will be obtained;

[0044] S3. In this embodiment, a separating funnel is used to separate the layered mixture to obtain two types of waste liquid. The first waste liquid is originally placed on the upper layer of the layered mixture, while the second waste liquid is originally placed on the lower layer of the layered mixture.

[0045] S4. The first and second waste liquids are treated separately. The first waste liquid mainly contains organic substances such as BDG and wax, while the second waste liquid mainly contains inorganic substances such as sodium hydroxide. There are relatively mature existing treatment methods for both types of waste liquids after separation. For example, the first waste liquid can be degraded using methods such as the Fenton reagent method to meet wastewater discharge standards before being discharged; the second waste liquid can be treated using methods such as neutralization and precipitation to meet various indicators of the second waste liquid before being discharged.

[0046] Preferably, in this embodiment, during step S1, the sodium carbonate powder can be bubbled to improve the dissolution efficiency of the sodium carbonate powder.

[0047] Preferably, before the final treatment of the first and second waste liquids in S4, steps 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 layer of the first waste liquid. After the separation step, the first waste liquid obtained from the repeated operation is collected uniformly for subsequent treatment. Meanwhile, the settling time of the mixture in S2 can be selected as 2 minutes to improve the overall efficiency of the treatment method.

[0048] like Figure 4 As shown, when paraffin wax dissolves in BDG solution, the solution as a whole will be a clear yellow solution. Since both sodium hydroxide aqueous solution and BDG solution are usually colorless and transparent liquids, the inventors hypothesize that when the mixture contains both paraffin wax and BDG solution, the solution color will change to yellow, and the intensity of the color can be used to roughly determine the content of BDG and wax in the mixture.

[0049] After the single addition of sodium carbonate reagent until the saturation state of dissolution, the second waste liquid obtained after 24h standing can also be colorless and transparent.

[0050] However, as shown in Figure 2 , when the standing time is short and only single separation is performed, the waste liquid at the bottom still presents a light yellow color. Then when the waste liquid at the bottom is subjected to a second addition of sodium carbonate powder until the sodium carbonate solution is supersaturated, as shown in Figure 3 , the waste liquid again produces a separation phenomenon, and the waste liquid at the bottom after the new separation tends to be colorless. This phenomenon not only verifies the above speculation of the inventor that the color depth of the solution is related to the residual degree of BDG and wax, but also shows that under the condition of single sodium carbonate supersaturation and short standing time, there are still BDG and wax residues in the waste liquid at the bottom. According to the further tests of the inventor, if the above steps are repeated more times, the liquid hardly separates again, and the color change in the waste liquid at the bottom is difficult to be detected by the naked eye. The two results confirm each other, indicating that most of the BDG and wax in the BDG-containing dewaxing wastewater have been separated into the upper waste liquid.

[0051] Therefore, in this embodiment, it is preferred to use the form of short standing time and twice repeated addition of sodium carbonate to the supersaturation state of dissolution to improve the treatment efficiency of the wastewater and to ensure that most of the BDG and wax are separated out.

[0052] Preferably, the first waste liquid obtained by separation can be subjected to distillation treatment to recover the BDG therein. In this embodiment, the distillation temperature is controlled at 230.5-231.5°C under standard atmospheric pressure, and the BDG can be recovered by distillation, wherein the recovery rate of the BDG can be ≥90%.

[0053] 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-containing dewaxing reagent, and therefore the second waste liquid is mainly subjected to acid-base neutralization treatment until it meets the wastewater discharge standard.

[0054] Waste liquid detection:

[0055] This step is used to detect the main components in the waste liquid after separation to prove that the BDG and wax have indeed been transferred. The main detection method used is the paraffin drop addition detection method.

[0056] This method is mainly based on the following principles: first, paraffin is difficult to dissolve in water. Paraffin is generally difficult to directly dissolve in water, but can dissolve in BDG aqueous solution, and as shown in Figure 4As shown, when paraffin wax dissolves in an aqueous BDG solution, the mixture is a clear, yellow solution. Secondly, paraffin wax undergoes a saponification reaction upon contact with alkali. Paraffin wax will undergo a saponification reaction when it enters an alkaline solution, such as... Figure 5 As shown, the solution will gradually become cloudy and viscous. Thirdly, when a large amount of BDG and alkali are present in the mixture, paraffin preferentially undergoes dissolution rather than saponification, and therefore... Figure 1 As shown, the BDG-containing dewaxing wastewater is a clear solution overall. In the above principle, changes in the liquid's color and transparency can be directly observed with the naked eye. Therefore, this paraffin addition detection method is mainly based on observing the changes in the color and transparency of the liquid after adding paraffin to the test object to determine the content of BDG and alkali in the test object.

[0057] The wastewater containing BDG for dewaxing, as described in this invention, mainly comprises wax, BDG, and alkali. After separation, the first wastewater primarily contains wax and BDG, while the second wastewater mainly contains alkali with only trace amounts of BDG and other organic substances remaining. Therefore, in this embodiment, during detection, it is only necessary to add paraffin wax to the second wastewater and observe its color and transparency to determine whether a large amount of BDG solution remains in the second wastewater, thus indicating whether BDG separation has occurred.

[0058] Test results displayed:

[0059] Figure 1 The image shows BDG-containing dewaxing wastewater, which can be equated to a mixture of water containing large amounts of BDG, a large amount of alkali, and then paraffin wax. As can be visually observed from the attached diagram, in this case, the mixture is generally a clear, yellow liquid with no obvious turbidity.

[0060] Figure 4 The image shows the mixture of BDG solution and paraffin. As can be clearly seen from the attached image, the mixture remains a clear, yellow liquid overall, without any turbidity. Figure 1 and Figure 2 This confirms that when a large amount of BDG and alkali are present in the mixture, paraffin preferentially dissolves, resulting in a mixture that is essentially a clear, yellow liquid.

[0061] and Figure 6 The image shows the direction taken from... Figure 3 The mixture at the bottom of the second waste liquid after adding paraffin is shown in the attached diagram. The mixture exhibits significant turbidity, indicating that the paraffin primarily reacted with the residual sodium hydroxide in the second waste liquid through a saponification reaction. On one hand, this result shows that the paraffin no longer preferentially dissolves, and the BDG content in the second waste liquid is much lower than the sodium hydroxide content. On the other hand, since the lower layer of the second waste liquid is taken from… Figure 3The bottom of the mixed solution, if the second waste liquid still exists wax, it can not keep the colorless and clear state as shown in Figure 3

[0062] Therefore, the above test results show that the treatment method of the present application successfully separates the organic matter such as BDG.

[0063] Comparative Example 1:

[0064] The difference between this comparative example and Example 1 is that in this comparative example, sodium carbonate is added to the sewage but does not reach the saturation state of sodium carbonate dissolution.

[0065] Comparative Example 2:

[0066] 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 a stratification phenomenon, the subsequent steps are not advanced.

[0067] Comparative Example 3:

[0068] 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 a stratification phenomenon, the subsequent steps are not advanced.

[0069] Comparative Example 4:

[0070] 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 a stratification phenomenon, the subsequent steps are not advanced.

[0071] Comparative Example 5:

[0072] 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 a stratification phenomenon, the subsequent steps are not advanced.

[0073] Comparative Example 6:

[0074] 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 a stratification phenomenon, the subsequent steps are not advanced.

[0075] Comparative Example 7:

[0076] 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 a stratification phenomenon, the subsequent steps are not advanced.

[0077] Analysis of the situation of the comparative example:

[0078] Figures 7-13 The changes of the BDG-containing dewaxing sewage after adding various reagents in Comparative Examples 1-7 are shown respectively. From​Figure 7 As can be seen from the results, when the amount of added sodium carbonate does not reach the saturation state of dissolution, no obvious stratification occurs in the BDG-containing dewaxing wastewater, and the treatment method described in the present application is difficult to promote. Figures 8-9 As can be seen from the results, neither the introduction of sodium ions alone nor the introduction of carbonate alone can cause obvious stratification in the BDG-containing dewaxing wastewater. Figure 10 As can be seen from the results of adding sodium bicarbonate in Example 3, even the combination of sodium ions and bicarbonate ions is difficult to cause the stratification of BDG-containing dewaxing wastewater to occur smoothly. Figures 11-13 The detection results of adding ferric chloride, copper chloride and ammonium chloride in Example 4 exclude the influence of other common metal ions, ammonium ions and halide ions represented by chloride ions on the stratification of BDG-containing dewaxing wastewater.

[0079] Therefore, based on the above detection results, the inventors have summarized the BDG-containing dewaxing wastewater treatment method described in the present application, which uses sodium carbonate as the core treatment agent to achieve the stratification of BDG-containing dewaxing wastewater, separate BDG and wax from the wastewater, and only leave the second wastewater that can be used for inorganic wastewater treatment. At the same time, the BDG in the first waste liquid can also be distilled and recycled for reuse, which overall reduces the corresponding use cost of BDG-containing dewaxing agents.

[0080] Finally, it should be noted that the above implementation examples are only used to illustrate the technical solutions of the present application, and are not limiting. Although the present application has been described in detail with reference to the foregoing implementation examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing implementation examples, or make equivalent substitutions for part of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solution to deviate from the scope of the technical solutions of the implementation examples of the present application.

Claims

1. A method for treating BDG-containing de-waxing effluent wastewater, comprising: The method comprises the following steps: S1. continuously adding sodium carbonate powder into sewage and stirring until sodium carbonate is in a dissolved saturated state or a dissolved supersaturated state in the mixed solution; S2. allowing the mixed solution to stand to obtain a layered mixed solution; S3. separating the layered mixed solution to obtain first waste liquid originally placed in the upper layer of the layered mixed solution and second waste liquid originally placed in the lower layer of the layered mixed solution; S4. separately performing waste liquid treatment on the first waste liquid and the second waste liquid; The BDG-containing dewaxing sewage contains BDG, strong alkali and wax.

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

3. A method for treating BDG-containing de-waxing effluent wastewater according to claim 2, wherein In S2, the mixed solution is allowed to stand for 1-10 min to obtain the layered mixed solution.

4. The method of claim 1, wherein the BDG-containing de-waxing wastewater is treated by a method comprising: In S1, bubbling stirring treatment is performed during the process of adding sodium carbonate powder into the sewage.

5. The method of claim 1, wherein the BDG-containing de-waxing effluent is treated by a method comprising: In S4, the first waste liquid is subjected to distillation treatment to recover BDG.

6. A method for treating BDG-containing de-waxing effluent wastewater according to claim 5, wherein The distillation temperature is 230.5-231.5 °C.

7. The method of claim 1, wherein the BDG-containing de-waxing effluent is treated by a method comprising: In S4, the second waste liquid is subjected to acid-base neutralization treatment.

8. The method of claim 1, wherein the BDG-containing de-waxing effluent is treated by a method comprising: The strong alkali is any one or a combination of multiple of sodium hydroxide or potassium hydroxide.

9. The method of claim 1, wherein the BDG-containing de-waxing effluent is treated by a method comprising: The wax is any one or a combination of multiple of paraffin wax, acrylate, C11-C22 alkyl acid, polypropylene wax, microcrystalline wax, polyethylene wax, and ethylene-vinyl acetate copolymer wax.

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