Method for treating organic silicon-containing wastewater
By using membrane treatment and inert waste residue slurry flocculation sedimentation methods, the problem of organosilicon treatment in titanium dioxide production wastewater was solved, realizing the effective reuse of wastewater and the safe treatment of inert waste residue.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HENAN BILLIONS NEW MATERIAL CO LTD
- Filing Date
- 2024-04-30
- Publication Date
- 2026-06-05
AI Technical Summary
During the production of titanium dioxide, organosilicon additives enter water bodies, increasing the difficulty of wastewater treatment. Conventional methods such as activated carbon adsorption and biochemical treatment are costly and ineffective, and there is a lack of effective means to treat inert waste residue.
A membrane treatment system is used to increase the concentration of organosilicon, and inert waste residue is mixed and pulped. Conditions are controlled to cause organosilicon to flocculate and settle. Combined with sedimentation and neutralization in a thick pool, the clear liquid and sludge are separated.
It effectively reduces the organosilicon content in wastewater, enabling the reuse or discharge of the clarified liquid. The acidity of the inert waste residue is reduced after treatment, meeting environmental protection requirements.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of wastewater treatment technology, and specifically relates to a method for treating wastewater containing organosilicon. Background Technology
[0002] During the production of titanium dioxide, a small amount of organic additives are added to ensure properties such as powder flowability. Furthermore, for titanium dioxide used in specific industries, specific additives are required depending on the application scenario. For example, organosilicon additives are used to ensure the hydrophobicity of titanium dioxide used in the plastics industry. However, during the titanium dioxide production process, organosilicon additives inevitably enter water bodies, resulting in a certain amount of organosilicon additives in the production wastewater, thus increasing the difficulty of water treatment.
[0003] Because silicone oil has high chemical stability and a certain degree of resistance to acids and alkalis, and it does not react at high temperatures, conventional treatment methods include activated carbon adsorption and biological treatment. Activated carbon adsorption has good treatment effects, but it is costly; biological treatment has certain requirements regarding the temperature, salinity, and organic matter content of the raw water. Summary of the Invention
[0004] The purpose of this invention is to provide a method for treating organosilicon-containing wastewater in order to overcome the shortcomings of the prior art.
[0005] The objective of this invention is achieved through the following technical solution:
[0006] A method for treating wastewater containing organosilicon includes the following steps:
[0007] S1. Wastewater containing organosilicon is treated through a membrane treatment system to obtain concentrated water with increased organosilicon concentration;
[0008] S2. The concentrated water and the inert waste residue from the tail gas section of the chlorination process titanium dioxide are mixed and pulped to obtain a slurry; the pulping temperature is 30-90℃;
[0009] S3. The slurry is allowed to settle to obtain a clear liquid and sludge with organosilicon removed.
[0010] Preferably, the organosilicon-containing wastewater in step S1 is wastewater generated during the titanium dioxide production process, wherein the TOC content is 30-150 ppm and the silicon content is 50-150 ppm.
[0011] Preferably, the membrane treatment system is an ultrafiltration + reverse osmosis membrane treatment system.
[0012] Preferably, the reverse osmosis membrane treatment system adopts a single-stage three-stage treatment process, controlling the TOC content in the first-stage purified water to be 0-50 ppm and the silicon content to be 1-20 ppm; the TOC content in the first-stage concentrate to be 100-300 ppm and the silicon content to be 200-600 ppm; the TOC content in the second-stage purified water to be 0-100 ppm and the silicon content to be 10-90 ppm; the TOC content in the second-stage concentrate to be 300-600 ppm and the silicon content to be 400-600 ppm; the TOC content in the third-stage purified water to be 0-20 ppm and the silicon content to be 10-100 ppm; and the TOC content in the third-stage concentrate to be 500-900 ppm and the silicon content to be 600-1800 ppm.
[0013] Preferably, the first stage of clean water, the second stage of clean water, and the third stage of clean water are combined and returned to the titanium dioxide production system as titanium dioxide washing water for recycling.
[0014] Preferably, the density of the slurry in step S2 is 1.2 to 1.45 g / mL.
[0015] Preferably, step S3 uses a thick sedimentation tank for settling.
[0016] Preferably, mechanical defoaming is performed before settling in step S3.
[0017] Preferably, the clarified liquid is neutralized to pH 11-12, and the sludge is neutralized to meet post-treatment requirements.
[0018] Preferably, the sludge is neutralized with alkali to a pH of 6.0–8.0.
[0019] This application first employs membrane treatment to increase the concentration of organosilicon in the wastewater containing organosilicon, which is beneficial for subsequent treatment. At the same time, some clean water is recovered. Then, the concentrated water from the membrane treatment and inert waste residue are mixed and pulped. By controlling the pulping conditions, the organosilicon undergoes silica gelation and is flocculated and settled by the inert waste residue, thus being removed from the wastewater. After treatment, the acidity of the inert waste residue is reduced, thereby effectively treating both the organosilicon and the inert waste residue. Detailed Implementation
[0020] In the production process of titanium dioxide in specific industries, such as the plastics industry, organosilicon additives are generally added at the corresponding production stages to ensure hydrophobicity. Inevitably, some organosilicon additives will be released into the water, resulting in titanium dioxide washing water containing organosilicon. The TOC content in this titanium dioxide washing water is about 30-150 ppm, and the silicon content is about 50-150 ppm. The applicant has tried to treat the titanium dioxide washing water using conventional activated carbon adsorption and biochemical treatment methods in the existing technology, but both methods have certain problems and cannot achieve good treatment results.
[0021] On the other hand, in the chlorination stage of titanium dioxide production via the chloride process, the chlorination gas contains not only titanium tetrachloride but also compounds of calcium, magnesium, silicon, aluminum, iron, etc., that do not participate in the reaction or are not completely reacted. After tail gas treatment such as condensation, a large amount of inert waste residue is generated. Due to its strong acidity and the large amount of harmful gases (such as chlorine) adsorbed on its surface, the inert waste residue cannot be directly discharged and needs to be neutralized to neutrality with a large amount of alkali before further treatment. Current technologies rarely address the treatment of this waste residue.
[0022] Based on the above, this application provides a method for treating organosilicon-containing wastewater using inert waste residue, which can effectively treat both the inert waste residue and the organosilicon-containing wastewater, specifically including the following steps:
[0023] S1. Wastewater containing organosilicon is treated through a membrane treatment system to obtain concentrated water with increased organosilicon concentration;
[0024] S2. Mix the concentrated water and the inert waste residue from the tail gas section of the titanium dioxide process with chlorination and pulp at a pulping temperature of 30-90℃ to obtain a slurry;
[0025] S3. Settle the slurry to obtain a clear liquid and sludge with organosilicon removed.
[0026] After membrane treatment, clear water and concentrated water enriched with salt are obtained. The clear water has a low ion content and can be directly discharged or returned to the titanium dioxide production system for reuse as titanium dioxide washing water. However, the concentrated water has a high salt content, which does not meet the standards for direct discharge. If conventional concentration and crystallization is used to precipitate the salt in solid form, the presence of organosilicon will cause partial silica gelation during the concentration and crystallization process, forming silica-like substances that prevent the entire concentration and crystallization process from operating normally. Therefore, the applicant uses a method of mixing and pulping the membrane treatment concentrated water with inert waste residue. By controlling the pulping conditions, the inert waste residue, which has a high salt content and a certain degree of acidity, promotes the silica gelation of organosilicon under high temperature conditions. This silica is then flocculated and settled by the inert waste residue and removed from the wastewater (settling liquid).
[0027] The clarified liquid after sedimentation and separation has a certain degree of acidity and contains a small amount of silicon. Therefore, it is preferable to neutralize it with carbide slag before further treatment or application. After neutralization, the silicon content can be further reduced.
[0028] The acidity of the sludge after sedimentation and separation decreases, but it still has a certain degree of acidity. It is recommended to neutralize it with alkali to about neutral (preferably pH 6.0 to 8.0) before landfilling or other treatments.
[0029] This application first employs membrane treatment to increase the concentration of organosilicon in the wastewater containing organosilicon, which is beneficial for subsequent treatment. At the same time, some clean water is recovered. Then, the concentrated water from the membrane treatment and inert waste residue are mixed and pulped. By controlling the pulping conditions, the organosilicon undergoes silica gelation and is flocculated and settled by the inert waste residue, thus being removed from the wastewater. After treatment, the acidity of the inert waste residue is reduced, thereby effectively treating both the organosilicon and the inert waste residue.
[0030] Preferably, the membrane treatment system is an ultrafiltration + reverse osmosis membrane treatment system. First, ultrafiltration is used to remove large particulate matter from the wastewater, and then reverse osmosis is used for concentration.
[0031] Preferably, the reverse osmosis membrane treatment system adopts a single-stage, three-stage treatment process. The TOC content in the first-stage purified water is controlled at 0–50 ppm, and the silicon content at 1–20 ppm; the TOC content in the first-stage concentrate is controlled at 100–300 ppm, and the silicon content at 200–600 ppm. The first-stage concentrate is then sent to the second-stage membrane treatment, where the TOC content in the second-stage purified water is controlled at 0–100 ppm, and the silicon content at 10–90 ppm; the TOC content in the second-stage concentrate is controlled at 300–600 ppm, and the silicon content at 400–1000 ppm. The second-stage concentrate is then sent to the third-stage membrane treatment, where the TOC content in the third-stage purified water is controlled at 0–20 ppm, and the silicon content at 10–50 ppm; the TOC content in the third-stage concentrate is controlled at 500–900 ppm, and the silicon content at 600–1800 ppm. The sulfate content in the third-stage concentrate is 15–25 g / L, and the chloride ion content is 5–15 g / L. Based on the content of each element in the raw water, combined with the desalination rate of the membrane system and the system pressure, the element content of the clear water and concentrate in each stage is controlled, and the treatment effect is relatively stable.
[0032] Preferably, the slurry density in step S2 is 1.2 to 1.45 g / mL. By limiting the slurry density, the amount of concentrated water and inert waste residue is limited, thereby improving the treatment effect.
[0033] Preferably, step S3 uses a thick sedimentation tank for settling.
[0034] Preferably, mechanical defoaming is performed before sedimentation in step S3 to prevent foam from affecting the flocculation and sedimentation effect.
[0035] Example 1
[0036] 1. Titanium dioxide washing water containing organosilicon is treated by an ultrafiltration + one-stage three-stage reverse osmosis membrane treatment system to obtain concentrated water. The TOC in the titanium dioxide washing water is 34 ppm and the silicon content is 97.3 ppm. The TOC in the first-stage reverse osmosis purified water is controlled to be 0 ppm and the silicon content is 1.5 ppm; the TOC in the first-stage reverse osmosis concentrated water is 252 ppm and the silicon content is 244.4 ppm; the TOC in the second-stage reverse osmosis purified water is 8.54 ppm and the silicon content is 39 ppm; the TOC in the second-stage reverse osmosis concentrated water is 484 ppm and the silicon content is 504.1 ppm; the TOC in the third-stage reverse osmosis purified water is 12.3 ppm and the silicon content is 49.7 ppm; the TOC in the third-stage reverse osmosis concentrated water is 881 ppm and the silicon content is 764.7 ppm. After mixing the first-stage, second-stage, and third-stage purified water, the silicon content is low, not exceeding 60 ppm, which meets the requirements for titanium dioxide washing water. This water is returned to the titanium dioxide production system as titanium dioxide washing water (preferably for the first washing stage) for reuse.
[0037] 2. The concentrated water from the third stage is returned to the tail gas section of the titanium dioxide process via the chloride process for pulping of inert waste residue; the pulp density is controlled at 1.3 g / mL and the pulping temperature is 65℃.
[0038] 3. Add appropriate defoaming equipment and thickening tank to remove the foam generated during the pulping process. At the same time, the clear liquid overflows. The resulting clear liquid has a silicon content of 34 ppm and a TOC of 45 ppm. The clear liquid is neutralized to pH 11.3 with carbide slag, and the thick bottom mud is neutralized to pH 7.0 with alkali.
[0039] The silicon content in the wastewater is ≤60ppm, which meets the requirements for reuse or discharge. Therefore, the silicon content in the clear liquid after sedimentation after pulping also meets the requirements for reuse or discharge.
[0040] Example 2
[0041] 1. Titanium dioxide washing water containing organosilicon is treated by an ultrafiltration + one-stage three-stage reverse osmosis membrane treatment system to obtain concentrated water. The TOC in the titanium dioxide washing water is 43 ppm, and the silicon content is 127 ppm. The TOC in the first-stage reverse osmosis purified water is controlled at 0.38 ppm, and the silicon content is 1.96 ppm; the TOC in the first-stage reverse osmosis concentrated water is 158.23 ppm, and the silicon content is 465.08 ppm; the TOC in the second-stage reverse osmosis purified water is 5.36 ppm, and the silicon content is 74.21 ppm; the second-stage reverse osmosis... The TOC in the concentrate was 311.10 ppm, and the silicon content was 855.94 ppm; the TOC in the three-stage reverse osmosis water was 7.92 ppm, and the silicon content was 84.39 ppm; the TOC in the three-stage reverse osmosis concentrate was 592.08 ppm, and the silicon content was 1566.35 ppm. After mixing the first-stage, second-stage, and third-stage water, the silicon content was low, not exceeding 60 ppm, which met the requirements for titanium dioxide washing water. This water was returned to the titanium dioxide production system as titanium dioxide washing water (preferably for the first washing stage) for reuse.
[0042] 2. The concentrated water from the third stage is returned to the tail gas section of the titanium dioxide process via the chloride process for pulping of inert waste residue; the pulp density is controlled at 1.3 g / mL and the pulping temperature is 65℃.
[0043] 3. Add appropriate defoaming equipment and thickening tank to remove the foam generated during the pulping process. At the same time, the clear liquid overflows. The resulting clear liquid has a silicon content of 31ppm and a TOC of 27ppm. The clear liquid is neutralized to pH 11.3 with carbide slag, and the thick bottom mud is neutralized to pH 7.0 with alkali.
[0044] The silicon content in the wastewater is ≤60ppm, which meets the requirements for reuse or discharge. Therefore, the silicon content in the clear liquid after sedimentation after pulping also meets the requirements for reuse or discharge.
[0045] Example 3
[0046] 1. Titanium dioxide washing water containing organosilicon is treated by an ultrafiltration + one-stage three-stage reverse osmosis membrane treatment system to obtain concentrated water. The TOC in the titanium dioxide washing water is 54 ppm, and the silicon content is 143 ppm. The TOC in the first-stage reverse osmosis purified water is controlled at 0.48 ppm, and the silicon content is 2.20 ppm; the TOC in the first-stage reverse osmosis concentrated water is 198.71 ppm, and the silicon content is 523.67 ppm; the TOC in the second-stage reverse osmosis purified water is 6.73 ppm, and the silicon content is 83.56 ppm; the second-stage reverse osmosis... The TOC in the concentrate was 390.69 ppm, and the silicon content was 963.77 ppm; the TOC in the three-stage reverse osmosis water was 9.93 ppm, and the silicon content was 95.02 ppm; the TOC in the three-stage reverse osmosis concentrate was 743.54 ppm, and the silicon content was 1763.69 ppm. After mixing the first-stage, second-stage, and third-stage water, the silicon content was low, not exceeding 60 ppm, which met the requirements for titanium dioxide washing water. This water was returned to the titanium dioxide production system as titanium dioxide washing water (preferably for the first washing stage) for reuse.
[0047] 2. The concentrated water from the third stage is returned to the tail gas section of the titanium dioxide process via the chloride process for pulping of inert waste residue; the pulp density is controlled at 1.3 g / mL and the pulping temperature is 65℃.
[0048] 3. Add appropriate defoaming equipment and thickening tank to remove the foam generated during the pulping process. At the same time, the clear liquid overflows. The resulting clear liquid has a silicon content of 37ppm and a TOC of 42ppm. The clear liquid is neutralized to pH 11.3 with carbide slag, and the thick bottom mud is neutralized to pH 7.0 with alkali.
[0049] The silicon content in the wastewater is ≤60ppm, which meets the requirements for reuse or discharge. Therefore, the silicon content in the clear liquid after sedimentation after pulping also meets the requirements for reuse or discharge.
[0050] Comparative Example 1
[0051] 1. Titanium dioxide washing water containing organic silica is treated by an ultrafiltration + one-stage three-stage reverse osmosis membrane treatment system to obtain concentrated water. The TOC in the titanium dioxide washing water is 20.5 ppm and the silica content is 85.6 ppm. The TOC in the first stage of purified water is controlled to be 0 ppm and the silica content is 0.8 ppm; the TOC in the first stage of concentrated water is 153 ppm and the silica content is 215 ppm; the TOC in the second stage of purified water is 5.19 ppm and the silica content is 34.3 ppm; the TOC in the second stage of concentrated water is 484 ppm and the silica content is 504.1 ppm; the TOC in the third stage of purified water is 12.3 ppm and the silica content is 49.7 ppm; the TOC in the third stage of concentrated water is 881 ppm and the silica content is 764.7 ppm.
[0052] 2. Add polyferric chloride to the concentrated solution of the three stages, according to an iron content of 53 g / L;
[0053] 3. Neutralization was performed using carbide slag slurry, with a final pH of 11.3. During neutralization, precipitates formed and adsorbed organosilicon. After sedimentation, a clear liquid and sludge were obtained. The clear liquid contained 75 ppm of silicon and 0.1 ppm of iron. The high silicon content in the clear liquid required further treatment and it could not be directly crystallized. Moreover, some solids remained after neutralization, resulting in high turbidity in the system after the reaction, making it impossible to directly proceed with crystallization. This demonstrates that neutralization with polyferric chloride and alkali is ineffective in removing organosilicon from concentrated water.
[0054] Comparative Example 2
[0055] 1. Titanium dioxide washing water containing organic silica is treated by an ultrafiltration + one-stage three-stage reverse osmosis membrane treatment system to obtain concentrated water. The TOC in the titanium dioxide washing water is 20.5 ppm and the silica content is 85.6 ppm. The TOC and silica content are controlled as follows: in the first stage of purification water, the TOC is 0 ppm and the silica content is 0.8 ppm; in the first stage of concentrated water, the TOC is 153 ppm and the silica content is 215 ppm; in the second stage of purification water, the TOC is 5.19 ppm and the silica content is 34.3 ppm; in the second stage of concentrated water, the TOC is 484 ppm and the silica content is 504.1 ppm; in the third stage of purification water, the TOC is 12.3 ppm and the silica content is 49.7 ppm; in the third stage of concentrated water, the TOC is 881 ppm and the silica content is 764.7 ppm.
[0056] 2. The three-stage concentrated water was mixed with hydrochloric acid, and the resulting acidity was 1.4 mol / L and the silicon content was 150.6 ppm.
[0057] 3. Neutralization was performed using carbide slag slurry, with a final pH of 11.3. Sedimentation followed, during which precipitates formed and adsorbed organosilicon, yielding a clear liquid and sludge. The clear liquid contained 75 ppm of silicon and 0.1 ppm of iron. The high silicon content necessitates further treatment, and the post-reaction system exhibited high turbidity, making direct crystallization impossible. This demonstrates that neutralization with hydrochloric acid and alkali is ineffective in removing organosilicon from concentrated water.
[0058] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.
Claims
1. A method for treating wastewater containing organosilicon, characterized in that, Includes the following steps: S1. Wastewater containing organosilicon is treated through a membrane treatment system to obtain concentrated water with increased organosilicon concentration; the membrane treatment system is an ultrafiltration + reverse osmosis membrane treatment system; the reverse osmosis membrane treatment system adopts a one-stage three-stage treatment process, controlling the TOC content in the first stage clean water to be 0~50ppm and the silicon content to be 1~20ppm; the TOC content in the first stage concentrated water to be 100~300ppm and the silicon content to be 200~600ppm; the TOC content in the second stage clean water to be 0~100ppm and the silicon content to be 10~90ppm; the TOC content in the second stage concentrated water to be 300~600ppm and the silicon content to be 400~1000ppm; the TOC content in the third stage clean water to be 0~20ppm and the silicon content to be 10~100ppm; the TOC content in the third stage concentrated water to be 500~900ppm and the silicon content to be 600~1800ppm; S2. The concentrated water from the three stages and the strongly acidic inert waste residue from the tail gas stage of the chlorination process of titanium dioxide are mixed and pulped to obtain a slurry; the density of the slurry is 1.3 g / mL, and the pulping temperature is 65℃; by controlling the pulping conditions, the organosilicon is silicated and flocculated and settled by the strongly acidic inert waste residue, and removed from the wastewater. The acidity of the strongly acidic inert waste residue is reduced after treatment, thereby effectively treating the organosilicon and the strongly acidic inert waste residue; S3. The slurry is settled in a thickening tank to obtain a clear liquid and sludge with organosilicon removed; Before settling in step S3, mechanical defoaming is performed first.
2. The method for treating organosilicon-containing wastewater as described in claim 1, characterized in that, The organosilicon-containing wastewater mentioned in step S1 is wastewater generated during the titanium dioxide production process, wherein the TOC content is 30~150ppm and the silicon content is 50~150ppm.
3. The method for treating organosilicon-containing wastewater as described in claim 1, characterized in that, The first, second, and third sections of clean water are combined and returned to the titanium dioxide production system as titanium dioxide washing water for recycling.
4. The method for treating organosilicon-containing wastewater as described in claim 1, characterized in that, The clarified liquid is neutralized to pH 11-12, and the sludge is neutralized to meet post-treatment requirements.
5. The method for treating organosilicon-containing wastewater as described in claim 4, characterized in that, The sludge is neutralized with alkali to a pH of 6.0-8.0.