Water treatment composite clarifier and preparation method thereof

Abstract

The application discloses a water treatment composite clarifier and a preparation method thereof. The clarifier contains, per 1000 parts by mass, 60-120 parts of polyaluminum chloride, 30-60 parts of polyferric sulfate, 3-10 parts of sodium phytate, 8-25 parts of trimethylsilanol, 2-8 parts of cationic polyacrylamide, and the balance of water. In the preparation, the trimethylsilanol is pre-dispersed in a PAC acidic solution to form a stable micro-dispersion system, and then a PFS-sodium phytate solution and a CPAM solution are introduced in sequence. The trimethylsilanol introduces a hydrophobic end-capping group through a condensation reaction with Si-OH groups of dissolved organosilicon in wastewater, reduces water solubility of the organosilicon, promotes phase separation and precipitation of the organosilicon, and realizes efficient capture and removal in cooperation with PAC / PFS electric neutralization and CPAM bridging flocculation. The total silicon removal rate can reach 88-95.8%, which is 20-30 percentage points higher than that of a traditional clarifier.

Description

Technical Field

[0001] This invention belongs to the field of water treatment agent technology, specifically relating to a composite clarifier for water treatment and its preparation method. Background Technology

[0002] Wastewater from the organosilicon industry contains a large amount of dissolved organosilicon compounds, including hydrolysis products of low molecular weight cyclosiloxanes, linear siloxane oligomers, silicon-containing surfactants, and hydrolysis products of silane coupling agents. These dissolved organosilicon substances are difficult to remove effectively by conventional coagulation and sedimentation methods due to their water solubility or the formation of stable emulsion / solubilization systems.

[0003] In existing technologies, the treatment of wastewater containing organosilicon mainly employs demulsification-coagulation, advanced oxidation, and membrane separation methods. Among these, coagulation is widely used due to its simple equipment and low cost. However, traditional inorganic clarifying agents such as polyaluminum chloride (PAC) or polyferric sulfate (PFS) typically only achieve a removal rate of 40-70% for dissolved organosilicon, which is insufficient to meet increasingly stringent emission requirements.

[0004] Therefore, it is necessary to develop a composite clarifying agent that can efficiently remove dissolved organosilicon from wastewater by converting dissolved organosilicon into an insoluble state and then combining it with flocculation and capture to achieve efficient removal. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a water treatment composite clarifying agent, which uses trimethylsilanol to hydrophobically modify dissolved organosilicon, causing it to destabilize and precipitate, and then combines it with an inorganic-organic composite flocculation system to achieve efficient capture and removal.

[0006] The composite clarifying agent of the present invention comprises, by weight (per 1000 parts of product), the following components: 60-120 parts of polyaluminum chloride, 30-60 parts of polyferric sulfate, 3-10 parts of sodium phytate, 8-25 parts of trimethylsilyl alcohol, 2-8 parts of cationic polyacrylamide, and the balance being water.

[0007] The polyaluminum chloride has a basicity of 60-90% and an Al2O3 content ≥28%. The polyferric sulfate has a basicity of 9-14% and a total iron content ≥19%. The cationic polyacrylamide has a molecular weight of 6 million-12 million and a cationicity of 20-40%. The trimethylsilanol has a purity ≥95%.

[0008] The present invention also provides a method for preparing the composite clarifying agent, comprising the following steps:

[0009] Step 1: Take 30-40% of the total water volume and place it in a reaction vessel. Add polyaluminum chloride and stir to dissolve. Then add trimethylsilanol and stir at 400-600 rpm for 20-30 minutes at 40-50℃ to obtain a PAC micro-dispersion containing trimethylsilanol, which is denoted as solution A.

[0010] Step 2: Take 15-25% of the total water volume, add polyferric sulfate and sodium phytate, stir and dissolve at room temperature until uniform, and record as solution B;

[0011] Step 3: Take 25-35% of the total water volume and add it to another container. While stirring continuously (300-500 rpm), slowly add solution B to solution A, then add the water in that amount, and continue stirring for 15-20 minutes to make the system homogeneous. This solution is called solution C.

[0012] Step 4: Take the remaining water volume and slowly disperse the cationic polyacrylamide into it. Stir at a low speed of 200-300 rpm for 60-90 minutes until it is fully swollen and dissolved to form a concentrated CPAM solution, which is denoted as solution D. Slowly add solution D to solution C and stir at a low speed (150-250 rpm) for 10-15 minutes to mix evenly to obtain the product.

[0013] In step one, trimethylsilanol is premixed with polyaluminum chloride (PAC). Trimethylsilanol (boiling point 99℃, molecular weight 90.2) has a solubility of approximately 1.5-2.0 g / 100 mL in water at 25℃, classifying it as slightly soluble. When directly added to wastewater, trimethylsilanol tends to float on the surface as droplets, resulting in extremely limited contact area with dissolved organosilicon. In this invention, the pH of the PAC solution is 2.5-3.5, and the hydrolysis products of aluminum (such as Al) in this acidic environment... 13 The polynuclear hydroxy complex (PAC) exhibits surface activity and can act as an emulsion stabilizer; simultaneously, a temperature of 40-50℃ enhances the water dispersibility of trimethylsilane. Under stirring, trimethylsilane is dispersed into microdroplets with a particle size of 1-5 μm, stabilized by PAC hydrolysis products, forming an acid-stable microdispersion system. This microdispersion system remains stable during product storage (no obvious stratification after standing at 25℃ for 30 days). When added to wastewater, trimethylsilane is rapidly and uniformly released in the form of microdroplets, achieving efficient contact with dissolved organosilicon.

[0014] In step two, the timing of adding sodium phytate is synchronized with that of polyferric sulfate, utilizing the interaction between the six phosphate groups of phytate and Fe. 3+ This forms a stable chelate coordination, preventing premature hydrolysis and ineffective precipitation of PFS due to pH changes during subsequent mixing with PAC. The sodium phytate-iron complex gradually releases Fe upon subsequent addition to the wastewater (pH 6-9). 3+ This achieves a slow-release flocculation effect, which is conducive to the formation of a dense floc structure.

[0015] The mixing sequence in step three (adding solution B to solution A) ensures that the PAC system is always in excess, preventing excessively high local pH levels that could lead to premature precipitation of aluminum and iron hydrolysis products. Adding supplementary water lowers the system concentration and reduces unintended reactions between components.

[0016] In step four, cationic polyacrylamide is dissolved separately before being mixed into the main system because the dissolution of high molecular weight CPAM requires low shear and long time conditions, and the concentrated solution (3-7%) is in a high-viscosity gel state. Finally, slow mixing avoids mechanical degradation of the CPAM molecular chains, maintaining its bridging and flocculation capabilities.

[0017] The mechanism of action of the composite clarifying agent of this invention on organosilicon-containing wastewater is as follows:

[0018] Dissolved organosilicon in wastewater mainly exists in the form of linear siloxane oligomers containing Si-OH end groups, hydrolysis products of cyclosiloxanes, and water-soluble organosilicon containing polyether segments. In this invention, the effect of trimethylsilanol on dissolved organosilicon is not through a cross-linking bridging mechanism (i.e., trimethylsilanol is a monofunctional silanol and lacks bridging ability), but rather through the following pathway to destabilize and precipitate the dissolved organosilicon:

[0019] Firstly, hydrophobic end-capping modification. The Si-OH group of trimethylsilanol undergoes a condensation reaction with the Si-OH end group on the dissolved organosilicon molecule (Si-OH + HO-Si → Si-O-Si + H2O), introducing a -OSi(CH3)3 hydrophobic group at the end of the organosilicon molecule. The strong hydrophobicity of the trimethyl group significantly reduces the hydrophilic-lipophilic balance of the organosilicon molecule, causing the organosilicon species that were originally soluble or dispersible in water to lose their water solubility and undergo phase separation and precipitation.

[0020] Secondly, acid-catalyzed self-condensation polymerization. The acidic environment provided by PAC (the local pH of the wastewater drops to 4-5 after addition) catalyzes the self-condensation reaction between multifunctional silicon-containing species in the wastewater (such as siloxane hydrolysates with multiple Si-OH groups), increasing their molecular weight and further reducing their water solubility. The condensation reaction of trimethylsilanol consumes the Si-OH groups of dissolved organosilicon, while the acidic conditions promote the condensation between the remaining Si-OH groups. These two effects work synergistically to rapidly convert dissolved organosilicon into insoluble silicon-containing particles.

[0021] Thirdly, flocculation and capture. The precipitated insoluble silica-containing particles carry a negative charge on their surface. These particles are destabilized by the positive charge provided by PAC and PFS, which neutralizes the aluminum / iron hydrolysis products. Then, the long molecular chains of CPAM bridge and flocculate, forming large-particle-size, high-density flocs that settle and separate. The slow-release properties of the sodium phytate-iron complex allow the flocculation process to continue, increasing the floc density.

[0022] The beneficial effects of this invention are:

[0023] (1) Through the hydrophobic end-capping modification of trimethylsilanol, dissolved organosilicon in wastewater is converted into insoluble microparticles, which solves the industry problem of low removal rate of dissolved organosilicon by traditional clarifying agents. The total silicon removal rate can reach 88-95.8%, which is 20-30 percentage points higher than that of traditional PAC / PFS composite clarifying agents.

[0024] (2) Multi-component synergistic design: PAC / PFS dual inorganic clarifying agent provides strong charge neutralization ability, sodium phytate-iron complex realizes slow-release flocculation and floc densification, and CPAM realizes bridging flocculation and accelerates sedimentation.

[0025] (3) The stepwise premixing in the preparation method ensures that trimethylsilanol is uniformly distributed in the product in a micro-dispersed state, thus ensuring the stability of the effect.

[0026] (4) The product is a uniform liquid preparation, which is convenient to use and can be directly metered and added. It is suitable for the treatment of various organic silicon wastewaters, such as organosilicon production wastewater and silicon-containing daily chemical wastewater. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments.

[0028] The raw materials used in the following examples are all commercially available industrial products or chemically pure reagents, and their specific specifications are as follows:

[0029] Polyaluminum chloride (PAC), basicity 75%, Al2O3 content 30%;

[0030] Polyferric sulfate (PFS), basicity 12%, total iron content 20%;

[0031] Sodium phytate, content 70% (calculated as phytic acid);

[0032] Trimethylsilanol, 97% purity;

[0033] Cationic polyacrylamide (CPAM) has a molecular weight of 8 million and a cationicity of 30%.

[0034] Example 1

[0035] A composite clarifier for water treatment, with the following dosages for each component (total 1000g):

[0036] Polyaluminum chloride (PAC): 80g;

[0037] Polyferric sulfate (PFS): 40g;

[0038] Sodium phytate: 5g;

[0039] Trimethylsilanol: 15g;

[0040] Cationic polyacrylamide (CPAM): 4g;

[0041] Water: 856g.

[0042] A method for preparing a composite clarifier for water treatment:

[0043] Step 1: Take 300g of water (35.0% of the total water volume of 856g, rounded up) and place it in a 1L three-necked flask. Add 80g of PAC and start stirring (500rpm) until completely dissolved. The solution is a pale yellow transparent liquid with a pH of approximately 3.1. Then add 15g of trimethylsilanol, heat to 45℃, and stir at 500rpm for 25 minutes. It was observed that trimethylsilanol initially dispersed in the form of oil droplets. After stirring for 10 minutes, the system became a uniform milky white semi-transparent state, indicating that trimethylsilanol had been stably dispersed into microdroplets by the PAC hydrolysis products. The resulting solution A is a uniform microemulsion liquid.

[0044] Step 2: Take another 170g of water (accounting for 19.9% ​​of the total water volume) into a 500mL beaker, add 40g of PFS and 5g of sodium phytate in sequence, stir at room temperature until completely dissolved, and the resulting solution B is a dark brown-red transparent solution.

[0045] Step 3: Take 257g of water (30.0% of the total water volume) and place it in a 2L reaction vessel. While stirring (400rpm), slowly add solution B to solution A (adding the rest in about 5 minutes). Then add the 257g of water to the mixture and continue stirring for 15 minutes. The resulting solution C is a brownish-yellow homogeneous liquid with a pH of approximately 2.8.

[0046] Step 4: Take the remaining 129g of water (15.1% of the total water volume) into a 500mL beaker. Slowly and evenly sprinkle 4g ​​of CPAM onto the water surface and stir at a low speed of 250rpm for 75min until the CPAM is fully swollen and dissolved, forming a viscous solution D (concentration approximately 3.0%). Slowly pour solution D into solution C and stir at a low speed of 200rpm for 12min to mix thoroughly, thus obtaining the finished product.

[0047] The resulting product is a uniform, viscous, brownish-yellow liquid with a viscosity of approximately 85 mPa·s at 25°C, a pH of approximately 2.9, and a density of approximately 1.08 g / cm³. 3 After being stored at 25℃ for 30 days, there was no stratification or sedimentation.

[0048] Example 2

[0049] A composite clarifier for water treatment, with the following dosages for each component (total 1000g):

[0050] Polyaluminum chloride (PAC): 60g;

[0051] Polyferric sulfate (PFS): 30g;

[0052] Sodium phytate: 3g;

[0053] Trimethylsilanol: 8g;

[0054] Cationic polyacrylamide (CPAM): 2g;

[0055] Water: 897g.

[0056] Preparation method:

[0057] Step 1: Take 287g of water (accounting for 32.0% of the total water volume of 897g) and place it in a reaction vessel. Add 60g of PAC and stir to dissolve. Add 8g of trimethylsilanol and stir at 450rpm for 20min at 40℃ to obtain solution A.

[0058] Step 2: Take 162g of water (accounting for 18.1% of the total water volume), add 30g of PFS and 3g of sodium phytate, stir and dissolve at room temperature to obtain solution B.

[0059] Step 3: Take 296g of water (accounting for 33.0% of the total water usage). Add solution B to solution A while stirring, then add the 296g of water, stir for 15 minutes, and obtain solution C.

[0060] Step 4: Take 152g of the remaining water (accounting for 16.9% of the total water volume), add 2g of CPAM, and stir at low speed (250rpm) for 60min until fully dissolved to form solution D (concentration approximately 1.3%). Add solution D to solution C, stir at low speed for 10min to mix evenly, and the finished product is obtained.

[0061] The resulting product is a light brownish-yellow homogeneous liquid with a viscosity of approximately 42 mPa·s at 25°C and a pH of approximately 3.2.

[0062] Example 3

[0063] A composite clarifier for water treatment, with the following dosages for each component (total 1000g):

[0064] Polyaluminum chloride (PAC): 120g;

[0065] Polyferric sulfate (PFS): 60g;

[0066] Sodium phytate: 10g;

[0067] Trimethylsilanol: 25g;

[0068] Cationic polyacrylamide (CPAM): 8g;

[0069] Water: 777g.

[0070] Preparation method:

[0071] Step 1: Take 295g of water (38.0% of the total water volume of 777g) and place it in a reaction vessel. Add 120g of PAC and stir to dissolve. Add 25g of trimethylsilanol and stir at 600rpm for 30min at 50℃ to obtain solution A. The system is milky white to pale yellow and has a high viscosity.

[0072] Step 2: Take 171g of water (accounting for 22.0% of the total water volume), add 60g of PFS and 10g of sodium phytate, stir and dissolve at room temperature to obtain solution B.

[0073] Step 3: Take 202g of water (accounting for 26.0% of the total water volume). Add solution B to solution A while stirring (500rpm), then add the 202g of water, stir for 20min to obtain solution C.

[0074] Step 4: Take the remaining 109g of water (accounting for 14.0% of the total water volume), add 8g of CPAM, and stir at 300rpm for 90min until fully swollen and dissolved to form a high-viscosity liquid D (concentration of about 6.8%, in a gel-like state). Add liquid D to liquid C in three portions, stirring at 200rpm for 5min after each addition, for a total of 15min until homogeneous, to obtain the finished product.

[0075] The resulting product is a uniform, viscous, brownish-yellow liquid with a viscosity of approximately 210 mPa·s at 25°C, a pH of approximately 2.5, and a density of approximately 1.13 g / cm³. 3 Due to the high content of active ingredients and the high viscosity of the product, it is recommended to dilute it with water at a ratio of 1:1 to 1:3 before use.

[0076] Example 4

[0077] A composite clarifier for water treatment, with the following dosages for each component (total 1000g):

[0078] Polyaluminum chloride (PAC): 100g;

[0079] Polyferric sulfate (PFS): 35g;

[0080] Sodium phytate: 6g;

[0081] Trimethylsilanol: 18g;

[0082] Cationic polyacrylamide (CPAM): 5g;

[0083] Water: 836g.

[0084] Preparation method:

[0085] Step 1: Take 301g of water (accounting for 36.0% of the total water volume of 836g) and place it in a reaction vessel. Add 100g of PAC and stir to dissolve. Add 18g of trimethylsilanol and stir at 500rpm for 25min at 45℃ to obtain solution A.

[0086] Step 2: Take 159g of water (accounting for 19.0% of the total water volume), add 35g of PFS and 6g of sodium phytate, stir and dissolve at room temperature to obtain solution B.

[0087] Step 3: Take 242g of water (accounting for 29.0% of the total water volume). Add solution B to solution A while stirring (450rpm), then add the 242g of water, stir for 18min to obtain solution C.

[0088] Step 4: Take the remaining 134g of water (accounting for 16.0% of the total water volume), add 5g of CPAM, and stir at low speed (250rpm) for 70min until fully dissolved to form solution D (concentration approximately 3.6%). Add solution D to solution C, stir at low speed for 12min to mix evenly, and the finished product is obtained.

[0089] The resulting product is a brownish-yellow, uniform, viscous liquid with a viscosity of approximately 120 mPa·s at 25°C and a pH of approximately 2.7.

[0090] Example 5

[0091] A composite clarifier for water treatment, with the following dosages for each component (total 1000g):

[0092] Polyaluminum chloride (PAC): 70g;

[0093] Polyferric sulfate (PFS): 55g;

[0094] Sodium phytate: 8g;

[0095] Trimethylsilanol: 12g;

[0096] Cationic polyacrylamide (CPAM): 3g;

[0097] Water: 852g.

[0098] Preparation method:

[0099] Step 1: Take 281g of water (accounting for 33.0% of the total water volume of 852g) and place it in a reaction vessel. Add 70g of PAC and stir to dissolve. Add 12g of trimethylsilanol and stir at 450rpm for 22min at 42℃ to obtain solution A.

[0100] Step 2: Take 162g of water (19.0% of the total water volume), add 55g of PFS and 8g of sodium phytate, and stir to dissolve at room temperature. Due to the high amount of PFS, the dissolution time was extended to 10 minutes to ensure complete dissolution, thus obtaining solution B.

[0101] Step 3: Take 264g of water (accounting for 31.0% of the total water volume). Add solution B to solution A while stirring (400rpm), then add the 264g of water, stir for 18min to obtain solution C.

[0102] Step 4: Take 145g of the remaining water (17.0% of the total water volume), add 3g of CPAM, and stir at low speed (200rpm) for 65 minutes until fully dissolved to form solution D (concentration approximately 2.0%). Add solution D to solution C and stir at low speed for 10 minutes to mix evenly to obtain the finished product.

[0103] The resulting product is a dark brownish-yellow homogeneous liquid with a viscosity of approximately 65 mPa·s at 25°C and a pH of approximately 2.8. This example exhibits a high PFS ratio, making it suitable for organosilicon wastewater with high heavy metal content.

[0104] Example 6

[0105] Amounts of each component (total 1000g): PAC 90g, PFS 45g, sodium phytate 4g, trimethylsilyl alcohol 20g, CPAM 6g, water 835g. The preparation method is the same as in Example 1. In step one, 292g (35.0%) of water was used; in step two, 167g (20.0%); in step three, 242g (29.0%); and in step four, 134g (16.0%). In step one, the temperature was 48℃ and the mixture was stirred for 28 minutes. The resulting product had a viscosity of approximately 155 mPa·s at 25℃ and a pH of approximately 2.7.

[0106] Example 7

[0107] Amounts of each component (total 1000g): PAC 75g, PFS 50g, sodium phytate 7g, trimethylsilyl alcohol 10g, CPAM 3g, water 855g. The preparation method is the same as in Example 1. In step one, 291g (34.0%) of water was used; in step two, 171g (20.0%); in step three, 257g (30.0%); and in step four, 136g (16.0%). In step one, the temperature was 43℃ ​​and the stirring time was 22min. The resulting product had a viscosity of approximately 58 mPa·s at 25℃ and a pH of approximately 2.9.

[0108] Example 8

[0109] Amounts of each component (total 1000g): PAC 110g, PFS 38g, sodium phytate 9g, trimethylsilyl alcohol 22g, CPAM 7g, water 814g. The preparation method is the same as in Example 1. In step one, 301g (37.0%) of water was used; in step two, 163g (20.0%); in step three, 228g (28.0%); and in step four, 122g (15.0%). In step one, the temperature was 50℃ and the mixture was stirred for 30min. The resulting product had a viscosity of approximately 185 mPa·s at 25℃ and a pH of approximately 2.6.

[0110] Example 9

[0111] Amounts of each component (total 1000g): PAC 65g, PFS 42g, sodium phytate 5g, trimethylsilyl alcohol 14g, CPAM 4g, water 870g. The preparation method is the same as in Example 1. In step one, 296g (34.0%) of water was used; in step two, 165g (19.0%); in step three, 270g (31.0%); and in step four, 139g (16.0%). In step one, the temperature was 44℃ and the mixture was stirred for 24 min. The resulting product had a viscosity of approximately 72 mPa·s at 25℃ and a pH of approximately 3.0.

[0112] Comparative Example 1

[0113] The difference from Example 1 is that it does not contain trimethylsilane, but is replaced by an equal amount of water. The amounts of each component (total 1000g): PAC 80g, PFS 40g, sodium phytate 5g, CPAM 4g, water 871g. In step one of the preparation method, only PAC is dissolved in 315g of water and stirred at 45°C for 25min (without the addition of trimethylsilane). The remaining steps are the same as in Example 1 (step two uses 170g of water, step three uses 257g of water, and step four uses 129g of water).

[0114] Comparative Example 2

[0115] The difference from Example 1 is that sodium phytate is not included; instead, an equal amount of water is used. The amounts of each component (total 1000g): PAC 80g, PFS 40g, trimethylsilyl alcohol 15g, CPAM 4g, water 861g. In step two of the preparation method, only PFS is dissolved in 175g of water; the remaining steps are the same as in Example 1.

[0116] Comparative Example 3

[0117] The difference from Example 1 is that CPAM is not included, and water in step four is directly added to solution C. The amounts of each component (total 1000g): PAC 80g, PFS 40g, sodium phytate 5g, trimethylsilyl alcohol 15g, water 860g. The preparation method is the same as in Example 1 for steps one to three; in step four, 133g of water is directly added to solution C and stirred until homogeneous.

[0118] Comparative Example 4

[0119] The difference from Example 1 is that an equal amount of dimethyl silicone oil (viscosity 50 mPa·s) was used instead of trimethylsilane. The amounts of each component (total 1000g): PAC 80g, PFS 40g, sodium phytate 5g, dimethyl silicone oil 15g, CPAM 4g, water 856g. The preparation method is the same as in Example 1. Dimethyl silicone oil was chosen as a control to demonstrate that the condensation reaction activity of the Si-OH groups in trimethylsilane is a necessary condition for achieving hydrophobic modification of dissolved organosilicon, i.e., dimethyl silicone oil molecules do not contain active Si-OH groups and cannot undergo a condensation reaction with dissolved organosilicon.

[0120] Comparative Example 5

[0121] The difference from Example 1 is that all components were mixed at once, without stepwise preparation. 856g of water was placed in a container, and 80g of PAC, 40g of PFS, 5g of sodium phytate, 15g of trimethylsilyl alcohol, and 4g of CPAM were added simultaneously. The mixture was stirred at room temperature for 60 minutes. This comparative example was used to verify the necessity of a stepwise preparation process.

[0122] Performance testing

[0123] The wastewater used for testing was taken from the effluent of the integrated wastewater equalization tank of an organosilicon monomer production enterprise. The water quality indicators were as follows: COD 950±80mg / L, total silicon (as Si) 72±8mg / L (of which dissolved organosilicon was about 58mg / L, measured after filtration through a 0.45μm filter membrane), suspended solids 280±40mg / L, pH 7.2±0.3, and turbidity 320±30NTU.

[0124] Test method: Take 1L of wastewater into a 1L beaker and place it on a six-piece stirrer. After adding the reagent, stir rapidly (250rpm) for 2 minutes, then stir slowly (50rpm) for 15 minutes. After standing for 30 minutes, take the supernatant for testing. The dosage is uniformly 400mg / L (i.e., 0.4g of product per liter of wastewater).

[0125] Methods for measuring each index: Total silicon was measured by inductively coupled plasma optical emission spectrometry (ICP-OES); COD was measured by the potassium dichromate method (GB11914); turbidity was measured by a turbidity meter; sedimentation velocity was recorded as the time required for the flocs to settle to the bottom of the cup and no longer change in volume, as observed by visual observation.

[0126] Characterization methods: After collection, the flocs were vacuum dried at 60℃ for 24h and the structure was analyzed by Fourier transform infrared spectroscopy (FTIR); the zeta potential of the supernatant after treatment was determined by Malvern zetasizer.

[0127] Test Results

[0128] Table 1: Summary of the processing effects of each embodiment and comparative example

[0129] serial number Total silicon removal rate / % COD removal rate / % Turbidity removal rate / % Settling time / min Example 1 93.5 78.2 96.8 16 Example 2 88.2 72.5 94.1 22 Example 3 95.8 82.6 97.5 14 Example 4 94.1 79.8 96.2 15 Example 5 91.6 76.9 95.8 18 Example 6 94.8 80.5 97.1 14 Example 7 90.3 75.4 95.2 19 Example 8 95.2 81.8 97.3 13 Example 9 91.0 74.8 95.5 19 Comparative Example 1 67.5 69.8 93.2 20 Comparative Example 2 86.3 71.2 91.5 28 Comparative Example 3 82.1 67.5 83.6 42 Comparative Example 4 69.2 68.3 92.8 21 Comparative Example 5 83.7 72.1 89.4 26

[0130] Table 2: FTIR characteristic peaks of flocs and Zeta potential of supernatant

[0131] serial number <![CDATA[Si-O-Si peak (1020-1090cm -1 ) relative intensity]]> <![CDATA[Si-C peak (1260cm -1 ) relative intensity]]> Zeta potential / mV Example 1 Strong (absorbance 0.82) Medium (absorbance 0.35) -3.2 Example 3 Strong (absorbance 0.91) Medium intensity (absorbance 0.41) -2.1 Comparative Example 1 Weak (absorbance 0.28) Weak (absorbance 0.12) -8.5 Comparative Example 3 Medium (absorbance 0.65) Medium (absorbance 0.30) -12.8 Comparative Example 4 Weak (absorbance 0.31) Weak (absorbance 0.14) -7.9

[0132] The results are analyzed as follows:

[0133] (1) Hydrophobic end-capping modification effect of trimethylsilane: Compared with Comparative Example 1, the total silicon removal rate increased from 67.5% to 93.5% after the addition of trimethylsilane, an increase of 26 percentage points. FTIR analysis of the flocs showed that Si-O-Si (1020-1090 cm⁻¹) in the flocs of Example 1 -1 ) and Si-C (1260cm) -1 The characteristic peak intensity of the sample was significantly higher than that of Comparative Example 1, proving that the formulation containing trimethylsilanol can transfer more organosilicon substances into the floc phase. The Si-O-Si peak in the floc phase of Comparative Example 1 was weaker, indicating that traditional clarifying agents can only capture a small amount of suspended organosilicon and are ineffective against dissolved organosilicon.

[0134] (2) Necessity of Si-OH groups: Compared with Comparative Example 4 (dimethyl silicone oil replacement), its total silicon removal rate was only 69.2%, which was comparable to Comparative Example 1 (67.5%) without silanol, and the Si-O-Si and Si-C peaks in the floc FTIR were both weak peaks. Although dimethyl silicone oil is also an organosilicon compound, it does not contain Si-OH active groups and cannot undergo a condensation reaction with dissolved organosilicon to introduce hydrophobic end-capping groups. This result directly proves that the mechanism of action of trimethylsilanol is a condensation reaction involving Si-OH, rather than a simple physical hydrophobic effect.

[0135] (3) Densification effect of sodium phytate: Compared with Comparative Example 1 and Comparative Example 2, the total silicon removal rate decreased by about 7 percentage points after removing sodium phytate, that is, from 93.5% to 86.3%. The more significant effects were the extended settling time (from 16 min to 28 min) and the decrease in turbidity removal rate (from 96.8% to 91.5%), indicating that sodium phytate improved the floc density and settling performance through the slow release effect of iron complex.

[0136] (4) Bridging and flocculation effect of CPAM: Compared with Comparative Example 1 and Comparative Example 3, the settling time after removing CPAM was significantly extended from 16 min to 42 min, and the turbidity removal rate decreased from 96.8% to 83.6%, indicating that the polymer bridging effect of CPAM is crucial for increasing floc size and rapid settling. The total silicon removal rate also decreased, from 93.5% to 82.1%, indicating that large flocs have a better trapping effect on silicon-containing particles than small flocs.

[0137] (5) Necessity of stepwise preparation process: Compared with Comparative Example 1 and Comparative Example 5 (one-time mixing), the removal rates of all items decreased and the settling time was prolonged. During one-time mixing, trimethylsilanol could not form a stable micro-dispersion system in the acidic environment of PAC and existed in the form of large droplets, resulting in insufficient contact with dissolved organosilicon; at the same time, CPAM had poor dissolution under high salt and high acid conditions, insufficient molecular chain unfolding, and weakened bridging effect.

[0138] Product stability test:

[0139] The product from Example 1 was sealed and stored at 5°C, 25°C and 40°C respectively, and its appearance was observed and the treatment effect was tested periodically.

[0140] The results showed that after 90 days of storage at 5℃ and 25℃, the product showed no stratification or sedimentation, and the total silicon removal rate changed by less than 2% compared with the fresh product. After 90 days of storage at 40℃, the product showed slight discoloration but no stratification, and the total silicon removal rate decreased by about 3%, but still remained above 90%.

Claims

1. A composite clarifying agent for water treatment, characterized in that, Per 1000 parts by weight, the product contains the following components: 60-120 parts polyaluminum chloride; 30-60 parts polyferric sulfate; 3-10 parts sodium phytate; 8-25 parts trimethylsilyl alcohol; 2-8 parts cationic polyacrylamide; and the balance is water.

2. The composite clarifying agent according to claim 1, characterized in that, The basicity of the polyaluminum chloride is 60%-90%, and the Al2O3 content is ≥28%; the basicity of the polyferric sulfate is 9%-14%, and the total iron content is ≥19%.

3. The composite clarifying agent according to claim 1, characterized in that, The cationic polyacrylamide has a molecular weight of 6 million to 12 million and a cationicity of 20% to 40%; the trimethylsilanol has a purity of ≥95%.

4. The composite clarifying agent according to claim 1, characterized in that, When the composite clarifying agent is used to treat wastewater containing organosilicon, the total silicon removal rate is ≥88%.

5. A method for preparing the composite clarifying agent as described in any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Take 30%-40% of the total water volume, add polyaluminum chloride and stir to dissolve, then add trimethylsilanol, stir at 400-600 rpm for 20-30 minutes at 40-50℃, so that trimethylsilanol forms a stable micro-dispersion system in the acidic PAC solution in the form of microdroplets, and obtain solution A. Step 2: Take 15%-25% of the total water volume, add polyferric sulfate and sodium phytate, stir and dissolve at room temperature to obtain solution B; Step 3: Take 25%-35% of the total water volume, add solution B to solution A while stirring, then add the same amount of water, and continue stirring for 15-20 minutes to obtain solution C; Step 4: Take the remaining water volume, add cationic polyacrylamide, and stir at a low speed of 200-300 rpm for 60-90 minutes until fully dissolved to obtain solution D; add solution D to solution C, stir at a low speed for 10-15 minutes to mix evenly, and the product is obtained.

6. The preparation method according to claim 5, characterized in that, In step three, the time for adding solution B to solution A is 3-8 minutes.

7. The application of the composite clarifying agent as described in any one of claims 1-4 in the treatment of organosilicon-containing wastewater, characterized in that, The dosage is 200-600 mg / L, and it is suitable for wastewater with a pH range of 5-9.

8. The application according to claim 7, characterized in that, The dissolved organosilicon content in the wastewater containing organosilicon is 20-150 mg / L (calculated as Si).

9. The application according to claim 7, characterized in that, The source of the organosilicon-containing wastewater is one or more of the following: organosilicon monomer production wastewater, organosilicon downstream processing wastewater, or silicon-containing surfactant wastewater.

10. The application according to claim 7, characterized in that, The application enables the total silicon removal rate of organosilicon-containing wastewater to reach over 88%.