A flocculant for oily wastewater and preparation method thereof

Abstract

The present invention relates to the technical field of flocculants for oily sewage, and specifically discloses a flocculant for oily sewage and a preparation method thereof. The flocculant raw material composition includes: tetraethyl orthosilicate, citric acid, MOFs precursor, zinc chloride, ethylenediamine, polyacrylamide, acrylic acid and toluene diisocyanate. The flocculant preparation method of the present invention is simple, can quickly form large-sized, high-strength flocs, significantly improves the sedimentation rate and treatment efficiency of oily sewage, is easy to separate, effectively reduces the subsequent treatment cost, and is suitable for large-scale promotion and use.

Description

Technical Field

[0001] The invention relates to the technical field of flocculants for oily sewage, and in particular to a flocculant for oily sewage and a preparation method thereof. Background Art

[0002] In the field of water treatment, polyacrylamide (PAM) is widely used as a flocculant, mainly through its long chain molecules to form bridges between suspended particles, accelerate the aggregation and sedimentation of particles to achieve solid-liquid separation. However, PAM still has some limitations when treating oily wastewater.

[0003] First, PAM is not particularly efficient in treating oily wastewater. Since the amide group (-CONH2) and carboxyl group (-COOH) on the PAM molecular chain cannot effectively neutralize the negative charge of the oil droplets in the oily wastewater, the flocculation effect is poor. On the one hand, PAM has limited adsorption capacity for oil droplets, especially when treating high-concentration oily wastewater, its oil removal rate often cannot meet environmental emission standards; on the other hand, the flocs formed by PAM are easily broken during the sedimentation process, resulting in a decrease in the turbidity removal rate, which not only affects the water treatment effect, but also increases the difficulty of subsequent sludge treatment.

[0004] Secondly, PAM also has limitations in floc strength. Due to the weak interaction between PAM molecules, the floc structure formed is relatively loose and has poor shear resistance. The strength of PAM flocs is not enough to resist the shear force during mechanical stirring and pumping, which affects the sedimentation effect. This limits its use in some application scenarios that require high-strength flocs.

[0005] In general, although PAM has a wide range of applications in water treatment, its oil removal rate, turbidity removal rate and floc strength limit its effectiveness and application range in the treatment of oily wastewater. Therefore, developing new flocculants or modifying PAM to improve its performance in oily wastewater treatment is an important research direction. Summary of the invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for preparing a flocculant for oily wastewater.

[0007] A flocculant for oily wastewater, wherein the raw materials include, by weight: 1-2 parts of tetraethyl orthosilicate, 0.2-0.4 parts of citric acid, 1-2 parts of MOFs precursor, 0.1-0.2 parts of zinc chloride, 0.2-0.4 parts of ethylenediamine, 2-4 parts of polyacrylamide, 0.2-0.4 parts of acrylic acid, and 0.1-0.2 parts of toluene diisocyanate;

[0008] The MOFs precursor contains Zn 2+A mixture of material and 2-methylimidazole; the Zn-containing 2+ The material is one of zinc nitrate, zinc chloride, zinc sulfate, zinc oxide and zinc acetate.

[0009] A method for preparing a flocculant for oily wastewater comprises the following steps:

[0010] S1. Dissolve tetraethyl orthosilicate in deionized water, add hydrochloric acid, stir, stand in a constant temperature water bath, add citric acid, stir, ultrasonicate, adjust the pH value of the system to 4-5, and dry to obtain a carboxylated aerogel;

[0011] S2, dissolving the MOFs precursor in deionized water, adding zinc chloride, stirring, adding ethylenediamine, ultrasonication, adjusting the pH value of the system to 7.5-8, standing in a constant temperature water bath, and drying to obtain amino-modified MOFs;

[0012] S3, dissolving polyacrylamide in deionized water, stirring, adding acrylic acid, stirring, ultrasonicating, adding toluene diisocyanate, adjusting the pH value of the system to 8-8.5, standing in a constant temperature water bath, and drying to obtain graft-modified polyacrylamide;

[0013] S4. Dissolve the modified polyacrylamide in deionized water, stir, add carboxyl aerogel and amino modified MOFs, stir, sonicate, adjust the pH value of the system to 7-7.5, let stand in a constant temperature water bath, dry, press through a granulator for 0.5-1h, the pressing pressure is 30-40MPa, the pressing temperature is 80-100℃, and sieve to obtain a flocculant for oily wastewater.

[0014] Preferably, in step S1, hydrochloric acid with a concentration of 1-1.5 mol / L is used to adjust the pH value of the system.

[0015] Preferably, in step S1, the stirring time is 0.5-1.5 h, and the stirring speed is 500-700 r / min.

[0016] Preferably, in step S1, the drying time is 24-36 hours and the drying temperature is 60-80°C.

[0017] Preferably, in step S1, the temperature of the constant temperature water bath is 40-60° C., and the time of the constant temperature water bath is 4-6 hours.

[0018] Preferably, in step S2, a sodium hydroxide solution with a concentration of 1-1.5 mol / L is used to adjust the pH value of the system.

[0019] Preferably, in step S2, the stirring time is 0.5-1h, and the stirring speed is 800-1000r / min.

[0020] Preferably, in step S2, the rate of adding ethylenediamine is 10-15% per minute based on the total weight of ethylenediamine.

[0021] Preferably, in step S2, the drying time is 12-18 hours and the drying temperature is 60-80°C.

[0022] Preferably, in step S2, the temperature of the constant temperature water bath is 80-90° C., and the time of the constant temperature water bath is 2-3 hours.

[0023] Preferably, in step S3, based on the total weight of toluene diisocyanate, the speed of adding toluene diisocyanate is 20-25% per minute.

[0024] Preferably, in step S3, the stirring time is 1-2 h, and the stirring speed is 500-700 r / min.

[0025] Preferably, in step S3, a sodium hydroxide solution with a concentration of 1-1.5 mol / L is used to adjust the pH value of the system to 8-8.5.

[0026] Preferably, in step S3, the temperature of the constant temperature water bath is 60-80° C., and the time of the constant temperature water bath is 4-6 hours.

[0027] Preferably, in steps S1, S2 and S3, the ultrasonic treatment time is 0.5-1 h, and the ultrasonic frequency is 40-60 kHz.

[0028] Preferably, in step S4, the first stirring time is 1-1.5 h, and the stirring speed is 600-800 r / min; the second stirring time is 0.6-1 h, and the stirring speed is 400-600 r / min.

[0029] Preferably, in step S4, a sodium hydroxide solution with a concentration of 0.5-1.5 mol / L is used to adjust the pH value of the system to 7-7.5.

[0030] Preferably, in step S4, the drying time is 24-30 hours and the drying temperature is 60-80°C.

[0031] Preferably, in step S4, the temperature of the constant temperature water bath is 50-60° C., and the time of the constant temperature water bath is 3-5 hours.

[0032] Preferably, in step S4, the ultrasonic treatment time is 1-2 h, and the ultrasonic frequency is 40-60 kHz.

[0033] Beneficial effects:

[0034] 1. In the present invention, carboxyl aerogel is formed by mixing ethyl orthosilicate with deionized water, adding hydrochloric acid solution for hydrolysis, and then reacting with citric acid at a specific temperature. The carboxyl functional group (-COOH) introduced in this step provides an active site for the subsequent chemical bonding with polyacrylamide, thereby improving the adsorption performance and flocculation effect of the flocculant. The high specific surface area and porous structure of the carboxyl aerogel provide more adsorption sites for oil droplets, thereby improving the treatment efficiency of the flocculant for oily wastewater, and having good oil removal and turbidity removal efficiency.

[0035] 2. In the present invention, the MOFs precursor reacts with ethylenediamine to introduce amino functional groups (-NH2), which not only enhance the chemical stability of MOFs, but also form stable coordination bonds with polyacrylamide, thereby improving the overall performance of the flocculant. In addition, the high specific surface area of ​​the amino-modified MOFs provides more adsorption sites for oil droplets, further enhancing the oil removal and turbidity removal efficiency.

[0036] 3. In the present invention, by introducing isocyanate groups into the polyacrylamide molecular chain, not only the chemical activity of polyacrylamide is enhanced, but also stable chemical bonds are formed by reacting with the carboxyl groups of the aerogel and the amino groups of the MOFs, which not only enhances the adsorption capacity of oil droplets, but also improves the flocculation efficiency and stability of the flocculant.

[0037] 4. In the present invention, the stable and tight chemical bonds not only improve the reusability of the flocculant and reduce the overall water treatment cost, but also greatly improve the floc strength: on the one hand, the high-strength flocs can form tight and strong flocs, which help to accelerate the sedimentation rate of the flocs in the water body; on the other hand, in the actual water treatment process, the flocs may be affected by mechanical forces such as pumping and stirring, while the high-strength flocs can resist these shear forces, maintain the integrity of their structure, and avoid the flocs from breaking and causing a decrease in the treatment effect.

[0038] 5. The flocculant preparation method of the present invention is simple, efficient and convenient for large-scale production. By precisely controlling the reaction conditions and the raw material ratio, flocculants with consistent performance can be continuously produced to meet the needs of industrial applications, which is of great significance for quickly reducing the oil content in sewage to meet the discharge standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a comparison chart of the oil removal rates of the oily wastewater flocculants obtained in Example 5 and Comparative Examples 1-2.

[0040] Figure 2 It is a comparison chart of the turbidity removal rates of the oily wastewater flocculants obtained in Example 5 and Comparative Examples 1-2.

[0041] Figure 3It is a comparison chart of floc particle size of the oily wastewater flocculants obtained in Example 5 and Comparative Examples 1-2.

[0042] Figure 4 It is a comparison chart of floc settling speed of the flocculants for oily wastewater obtained in Example 5 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0043] The present invention will be further explained below in conjunction with specific embodiments.

[0044] Example 1

[0045] A method for preparing a flocculant for oily wastewater comprises the following steps:

[0046] S1. Dissolve 50 g of tetraethyl orthosilicate in 200 g of deionized water by weight, add 5 g of 1 mol / L hydrochloric acid solution, stir for 0.5 h at a stirring speed of 500 r / min, stand in a constant temperature water bath at 40°C for 4 h, add 10 g of citric acid, stir for 0.5 h at a stirring speed of 500 r / min, perform ultrasonic treatment for 0.5 h at a frequency of 40 kHz, adjust the pH value of the system to 4 using a 1 mol / L hydrochloric acid solution, dry for 24 h at a drying temperature of 60°C, and obtain a carboxylated aerogel;

[0047] S2, 50g MOFs precursor was dissolved in 200g deionized water, 5g zinc chloride was added, and the mixture was stirred for 0.5h at a stirring speed of 800r / min, 10g ethylenediamine was added, and the addition rate of ethylenediamine was 10% per minute based on the total weight of ethylenediamine, and ultrasonic treatment was performed for 0.5h at an ultrasonic frequency of 40kHz, and the pH value of the system was adjusted to 7.5 using a sodium hydroxide solution with a concentration of 1mol / L, and the mixture was placed in a constant temperature water bath at 80°C for 2h, and dried for 12h at a drying temperature of 60°C to obtain amino-modified MOFs;

[0048] The MOFs precursor is a mixture of zinc chloride and 2-methylimidazole; the weight ratio of zinc chloride to 2-methylimidazole is 1:2;

[0049] S3, dissolving 100g polyacrylamide in 500g deionized water, stirring for 1h, stirring speed is 500r / min, adding 10g acrylic acid, stirring for 0.5h, stirring speed is 500r / min, ultrasonic treatment for 0.5h, ultrasonic frequency is 40kHz, adding 5g toluene diisocyanate, based on the total weight of toluene diisocyanate, toluene diisocyanate addition rate is 20% per minute, using 1mol / L sodium hydroxide solution to adjust the system pH value to 8, standing in a constant temperature water bath at 60°C for 4h, drying for 12h, drying temperature is controlled at 60°C, to obtain graft-modified polyacrylamide;

[0050] S4. Dissolve the modified polyacrylamide in 500g deionized water, stir for 1h at a stirring speed of 600r / min, add carboxyl aerogel and amino modified MOFs, stir for 0.6h at a stirring speed of 400r / min, perform ultrasonic treatment for 1h at an ultrasonic frequency of 40kHz, adjust the pH value of the system to 7 with a sodium hydroxide solution having a concentration of 0.5mol / L, place in a constant temperature water bath at 50°C for 3h, dry for 24h at a drying temperature of 60°C, press through a granulator for 0.5h at a pressing pressure of 30MPa and a pressing temperature of 80°C, and sieve to obtain a flocculant for oily wastewater.

[0051] Example 2

[0052] A method for preparing a flocculant for oily wastewater comprises the following steps:

[0053] S1. Dissolve 100 g of tetraethyl orthosilicate in 300 g of deionized water by weight, add 10 g of 1.5 mol / L hydrochloric acid solution, stir for 1.5 h at a stirring speed of 700 r / min, stand in a 60°C constant temperature water bath for 6 h, add 20 g of citric acid, stir for 1.5 h at a stirring speed of 700 r / min, perform ultrasonic treatment for 1 h at a frequency of 60 kHz, adjust the pH value of the system to 5 using a 1.5 mol / L hydrochloric acid solution, dry for 36 h at a drying temperature of 80°C, and obtain a carboxylated aerogel;

[0054] S2. Dissolve 100g of MOFs precursor in 300g of deionized water, add 10g of zinc chloride, stir for 1h at a stirring speed of 1000r / min, add 20g of ethylenediamine, and add ethylenediamine at a rate of 15% per minute based on the total weight of ethylenediamine. Ultrasonic treatment for 1h at an ultrasonic frequency of 60kHz, use a sodium hydroxide solution with a concentration of 1.5mol / L to adjust the system pH value to 8, place in a constant temperature water bath at 90°C for 3h, dry for 18h at a drying temperature of 80°C, and obtain amino-modified MOFs;

[0055] The MOFs precursor is a mixture of zinc sulfate and 2-methylimidazole; the weight ratio of zinc sulfate to 2-methylimidazole is 1:2;

[0056] S3, dissolving 200g polyacrylamide in 750g deionized water, stirring for 2h, stirring speed is 700r / min, adding 20g acrylic acid, stirring for 1h, stirring speed is 700r / min, ultrasonic treatment for 1h, ultrasonic frequency is 60kHz, adding 10g toluene diisocyanate, based on the total weight of toluene diisocyanate, toluene diisocyanate addition rate is 25% per minute, using 1.5mol / L sodium hydroxide solution to adjust the system pH value to 8.5, standing in 80℃ constant temperature water bath for 6h, drying for 18h, drying temperature is controlled to 80℃, to obtain graft modified polyacrylamide;

[0057] S4. Dissolve the modified polyacrylamide in 1000g deionized water, stir for 1.5h at a stirring speed of 800r / min, add carboxyl aerogel and amino modified MOFs, stir for 1h at a stirring speed of 600r / min, perform ultrasonic treatment for 2h at an ultrasonic frequency of 60kHz, adjust the pH value of the system to 7.5 with a sodium hydroxide solution having a concentration of 1.5mol / L, place in a constant temperature water bath at 60°C for 5h, dry for 30h at a drying temperature of 80°C, press through a granulator for 1h at a pressing pressure of 40MPa and a pressing temperature of 100°C, and sieve to obtain a flocculant for oily wastewater.

[0058] Example 3

[0059] A method for preparing a flocculant for oily wastewater comprises the following steps:

[0060] S1. Dissolve 60g of tetraethyl orthosilicate in 225g of deionized water by weight, add 6g of 1.1mol / L hydrochloric acid solution, stir for 0.7h at a stirring speed of 550r / min, stand in a 45°C constant temperature water bath for 4.5h, add 12.5g of citric acid, stir for 0.7h at a stirring speed of 550r / min, perform ultrasonic treatment for 0.6h at an ultrasonic frequency of 45kHz, adjust the pH value of the system to 4.2 using a 1.1mol / L hydrochloric acid solution, dry for 27h at a drying temperature of 65°C, and obtain a carboxylated aerogel;

[0061] S2, 60g MOFs precursor was dissolved in 225g deionized water, 6g zinc chloride was added, and the mixture was stirred for 0.6h at a stirring speed of 850r / min, 12.5g ethylenediamine was added, and the addition rate of ethylenediamine was 11% per minute based on the total weight of ethylenediamine, and ultrasonic treatment was performed for 0.6h at an ultrasonic frequency of 45kHz, and the pH value of the system was adjusted to 7.6 using a sodium hydroxide solution with a concentration of 1.1mol / L, and the mixture was placed in a constant temperature water bath at 82°C for 2.2 hours, and dried for 14h at a drying temperature of 65°C to obtain amino-modified MOFs;

[0062] The MOFs precursor is a mixture of zinc oxide and 2-methylimidazole; the weight ratio of zinc oxide to 2-methylimidazole is 1:2;

[0063] S3, 125g polyacrylamide was dissolved in 550g deionized water, stirred for 1.2h, stirring speed was 550r / min, 12.5g acrylic acid was added, stirred for 0.6h, stirring speed was 550r / min, ultrasonic treatment was performed for 0.6h, ultrasonic frequency was 45kHz, 6g toluene diisocyanate was added, based on the total weight of toluene diisocyanate, the toluene diisocyanate addition rate was 21% per minute, the pH value of the system was adjusted to 8.1 using a sodium hydroxide solution with a concentration of 1.1mol / L, the system was allowed to stand in a constant temperature water bath at 65°C for 4.5h, dried for 13h, and the drying temperature was controlled to 65°C to obtain graft-modified polyacrylamide;

[0064] S4. Dissolve the modified polyacrylamide in 600g deionized water, stir for 1.1h at a stirring speed of 650r / min, add carboxyl aerogel and amino modified MOFs, stir for 0.7h at a stirring speed of 450r / min, perform ultrasonic treatment for 1.2h at an ultrasonic frequency of 45kHz, adjust the pH value of the system to 7.1 with a sodium hydroxide solution having a concentration of 0.7mol / L, place in a constant temperature water bath at 52°C for 3.5, dry for 25h at a drying temperature of 65°C, press through a granulator for 0.6h at a pressing pressure of 32MPa and a pressing temperature of 85°C, and sieve to obtain a flocculant for oily wastewater.

[0065] Example 4

[0066] A method for preparing a flocculant for oily wastewater comprises the following steps:

[0067] S1. Dissolve 90g of tetraethyl orthosilicate in 275g of deionized water by weight, add 9g of 1.4mol / L hydrochloric acid solution, stir for 1.2h at a stirring speed of 650r / min, stand in a 55°C constant temperature water bath for 5.5h, add 17.5g of citric acid, stir for 1.2h at a stirring speed of 650r / min, perform ultrasonic treatment for 0.9h at an ultrasonic frequency of 55kHz, adjust the pH value of the system to 4.8 using a 1.4mol / L hydrochloric acid solution, dry for 33h at a drying temperature of 75°C, and obtain a carboxylated aerogel;

[0068] S2, 90g MOFs precursor was dissolved in 275g deionized water, 9g zinc chloride was added, and the mixture was stirred for 0.9h at a stirring speed of 950r / min, 17.5g ethylenediamine was added, and the addition rate of ethylenediamine was 14% per minute based on the total weight of ethylenediamine, and ultrasonic treatment was performed for 0.9h at an ultrasonic frequency of 55kHz, and the pH value of the system was adjusted to 7.9 using a sodium hydroxide solution with a concentration of 1.4mol / L, and the mixture was placed in a constant temperature water bath at 88°C for 2.8h, and dried for 17h at a drying temperature of 75°C to obtain amino-modified MOFs;

[0069] The MOFs precursor is a mixture of zinc acetate and 2-methylimidazole; the weight ratio of zinc acetate to 2-methylimidazole is 1:1;

[0070] S3, 175g polyacrylamide was dissolved in 700g deionized water, stirred for 1.8h, the stirring speed was 650r / min, 17.5g acrylic acid was added, stirred for 0.9h, the stirring speed was 650r / min, ultrasonic treatment was performed for 0.9h, the ultrasonic frequency was 55kHz, 9g toluene diisocyanate was added, based on the total weight of toluene diisocyanate, the toluene diisocyanate addition rate was 24% per minute, the pH value of the system was adjusted to 8.4 using a sodium hydroxide solution with a concentration of 1.4mol / L, the mixture was allowed to stand in a constant temperature water bath at 75°C for 5.5h, dried for 17h, and the drying temperature was controlled to 75°C to obtain graft-modified polyacrylamide;

[0071] S4. Dissolve the modified polyacrylamide in 900g deionized water, stir for 1.4h at a stirring speed of 750r / min, add carboxyl aerogel and amino modified MOFs, stir for 0.9h at a stirring speed of 550r / min, perform ultrasonic treatment for 1.8h at an ultrasonic frequency of 55kHz, adjust the pH value of the system to 7.4 with a sodium hydroxide solution having a concentration of 1.2mol / L, place in a constant temperature water bath at 58°C for 4.5h, dry for 29h at a drying temperature of 75°C, press through a granulator for 0.9h at a pressing pressure of 38MPa at a pressing temperature of 95°C, and sieve to obtain a flocculant for oily wastewater.

[0072] Example 5

[0073] A method for preparing a flocculant for oily wastewater comprises the following steps:

[0074] S1. Dissolve 75g of tetraethyl orthosilicate in 250g of deionized water by weight, add 7.5g of 1.2mol / L hydrochloric acid solution, stir for 1h at a stirring speed of 600r / min, stand in a 50°C constant temperature water bath for 5h, add 15g of citric acid, stir for 1h at a stirring speed of 600r / min, perform ultrasonic treatment for 0.7h at an ultrasonic frequency of 50kHz, adjust the pH value of the system to 4.5 using a 1.2mol / L hydrochloric acid solution, dry for 30h at a drying temperature of 70°C, and obtain a carboxylated aerogel;

[0075] S2, 75g MOFs precursor was dissolved in 250g deionized water, 7.5g zinc chloride was added, and the mixture was stirred for 0.7h at a stirring speed of 900r / min, 15g ethylenediamine was added, and the addition rate of ethylenediamine was 12% per minute based on the total weight of ethylenediamine, and ultrasonic treatment was performed for 0.7h at an ultrasonic frequency of 50kHz, and the pH value of the system was adjusted to 7.7 using a sodium hydroxide solution with a concentration of 1.2mol / L, and the mixture was placed in a constant temperature water bath at 85°C for 2.5h, and dried for 15h at a drying temperature of 70°C to obtain amino-modified MOFs;

[0076] The MOFs precursor is a mixture of zinc nitrate and 2-methylimidazole; the weight ratio of zinc nitrate to 2-methylimidazole is 1:3;

[0077] S3, 150g polyacrylamide was dissolved in 600g deionized water, stirred for 1.5h, the stirring speed was 600r / min, 15g acrylic acid was added, stirred for 0.7h, the stirring speed was 600r / min, ultrasonic treatment was performed for 0.7h, the ultrasonic frequency was 50kHz, 7.5g toluene diisocyanate was added, based on the total weight of toluene diisocyanate, the toluene diisocyanate addition rate was 22% per minute, the pH value of the system was adjusted to 8.2 using a sodium hydroxide solution with a concentration of 1.2mol / L, the mixture was allowed to stand in a constant temperature water bath at 70°C for 5h, dried for 15h, and the drying temperature was controlled to 70°C to obtain graft-modified polyacrylamide;

[0078] S4. Dissolve the modified polyacrylamide in 750g deionized water, stir for 1.2h at a stirring speed of 700r / min, add carboxyl aerogel and amino modified MOFs, stir for 0.8h at a stirring speed of 500r / min, perform ultrasonic treatment for 1.5h at an ultrasonic frequency of 50kHz, adjust the pH value of the system to 7.2 with a sodium hydroxide solution having a concentration of 1mol / L, place in a constant temperature water bath at 55°C for 4h, dry for 27h at a drying temperature of 70°C, press in a granulator for 0.7h at a pressing pressure of 35MPa and a pressing temperature of 90°C, and sieve to obtain a flocculant for oily wastewater.

[0079] Comparative Example 1

[0080] A method for preparing a flocculant for oily wastewater comprises the following steps:

[0081] 150 g of PAM powder was added to 1500 ml of deionized water, stirred, and allowed to stand at room temperature for 24 hours. The powder was extruded by a granulator to form a granular flocculant. The pressing pressure of the granulator was set to 35 MPa, and the pressing temperature was controlled at 90° C. The formed PAM particles were dried in a drying oven at 70° C. for 27 hours, and sieved to obtain a flocculant for oily wastewater.

[0082] Comparative Example 2

[0083] A method for preparing a flocculant for oily wastewater comprises the following steps:

[0084] S1. Dissolve 75g of tetraethyl orthosilicate in 250g of deionized water by weight, add 7.5g of 1.2mol / L hydrochloric acid solution, stir for 1h at a stirring speed of 600r / min, stand in a 50°C constant temperature water bath for 5h, add 15g of citric acid, stir for 1h at a stirring speed of 600r / min, perform ultrasonic treatment for 0.7h at an ultrasonic frequency of 50kHz, adjust the pH value of the system to 4.5 using a 1.2mol / L hydrochloric acid solution, dry for 30h at a drying temperature of 70°C, and obtain a carboxylated aerogel;

[0085] S2, 75g MOFs precursor was dissolved in 250g deionized water, 7.5g zinc chloride was added, and the mixture was stirred for 0.7h at a stirring speed of 900r / min, 15g ethylenediamine was added, and the addition rate of ethylenediamine was 12% per minute based on the total weight of ethylenediamine, and ultrasonic treatment was performed for 0.7h at an ultrasonic frequency of 50kHz, and the pH value of the system was adjusted to 7.7 using a sodium hydroxide solution with a concentration of 1.2mol / L, and the mixture was placed in a constant temperature water bath at 85°C for 2.5h, and dried for 15h at a drying temperature of 70°C to obtain amino-modified MOFs;

[0086] The MOFs precursor contains Zn 2 + a mixture of material and 2-methylimidazole; the Zn-containing 2 +The material is one of zinc nitrate, zinc chloride, zinc sulfate, zinc oxide and zinc acetate;

[0087] S3. Dissolve 150g of polyacrylamide in 750g of deionized water, stir for 1.2h at a stirring speed of 700r / min, add carboxyl aerogel and amino-modified MOFs, stir for 0.8h at a stirring speed of 500r / min, perform ultrasonic treatment for 0.7h at an ultrasonic frequency of 50kHz, adjust the pH value of the system to 7.2 with a sodium hydroxide solution having a concentration of 1mol / L, place in a constant temperature water bath at 55°C for 4h, dry for 27h at a drying temperature of 70°C, press in a granulator for 0.7h at a pressing pressure of 35MPa and a pressing temperature of 90°C, and sieve to obtain a flocculant for oily wastewater.

[0088] Test Example 1

[0089] The flocculants for oily wastewater obtained in Example 5 and Comparative Examples 1-2 were tested for oil removal rate, as follows:

[0090] Collect oily wastewater samples of the same source and nature, and record their initial oil content. Mix 1000g of oily wastewater sample with 20mg, 30mg, 40mg, 50mg, and 60mg of flocculants (Example 5, Comparative Example 1, and Comparative Example 2), stir, and leave for 0.5h.

[0091] A water sample was taken from the supernatant of the mixture and the remaining oil content was determined.

[0092] Use the following formula to calculate:

[0093] Test Example 2

[0094] The flocculants for oily wastewater obtained in Example 5 and Comparative Examples 1-2 were tested for turbidity removal rate, as follows:

[0095] Collect oily wastewater samples of the same source and nature, and record their initial turbidity. Mix 1000g of oily wastewater sample with 20mg, 30mg, 40mg, 50mg, and 60mg of flocculants (Example 5, Comparative Example 1, and Comparative Example 2), stir, and place for 0.5h.

[0096] A water sample was collected from the supernatant of the mixture, and the turbidity of the supernatant was measured using a turbidity meter.

[0097] Use the following formula to calculate:

[0098] Depend on Figure 1 , Figure 2The test results of oil removal rate and turbidity removal rate show that Example 5 has the best oil removal effect, followed by Comparative Example 2, and Comparative Example 1 is the worst. This is because Example 5 introduces multiple functional groups, such as carboxyl, amino, etc., which enhance the interaction between the flocculant and the oil-containing particles, thereby greatly improving the oil removal rate. This modified flocculant usually has a stronger adsorption capacity and bridging effect, which can significantly improve the oil removal and turbidity removal efficiency. However, the traditional polyacrylamide flocculant in Comparative Example 1 cannot provide enough functional groups to interact with the oil droplets due to its single functional group, resulting in a low oil removal rate. Although the flocculant in Comparative Example 2 has also been modified to a certain extent, its oil removal effect is between Example 5 and Comparative Example 1 due to incomplete modification or a small number of functional groups.

[0099] Test Example 3

[0100] The flocculants for oily wastewater obtained in Example 5 and Comparative Examples 1-2 were tested for floc strength in terms of "floc particle size", as follows:

[0101] Oily wastewater samples of the same source and nature were collected, and flocculants (Example 5, Comparative Example 1, Comparative Example 2) were mixed with 1000 g of the oily wastewater samples at dosages of 20 mg, 30 mg, 40 mg, 50 mg, and 60 mg, respectively, and stirred. A laser particle size analyzer (such as Malvern Mastersizer) was used, and the laser beam passed through the sample cell. The particles would scatter the laser, and the detector of the instrument would capture the intensity and angle of the scattered light, automatically record the intensity and angle of the scattered light, and analyze it through the built-in software.

[0102] Test Example 4

[0103] The flocculants for oily wastewater obtained in Example 5 and Comparative Examples 1-2 were tested for floc strength by "floc settling velocity", as follows:

[0104] Collect oily wastewater samples of the same source and nature, mix the flocculants (Example 5, Comparative Example 1, Comparative Example 2) with 1000g of the oily wastewater sample at dosages of 20mg, 30mg, 40mg, 50mg, and 60mg, respectively, stir, pour the mixed sample into a 1L measuring cylinder to the full scale, let it stand, time it, and record the starting height of floc sedimentation, let the sedimentation tube or measuring cylinder stand, start timing, and record the height of floc sedimentation.

[0105] Use the following formula to calculate:

[0106] Where Δh is the change in height of floc settling and Δt is the change in time taken for settling.

[0107] Depend on Figure 3 , Figure 4It can be seen that the modified flocculant of Example 5 has a larger floc particle size and a faster floc settling rate, which indicates that the floc strength of Example 5 is stronger. This is because the addition of tetraethyl orthosilicate and citric acid helps to form a more stable floc structure, while the MOFs precursor and zinc chloride increase the density and particle size of the floc.

[0108] From the above, we can see that the performance of flocculants can be significantly improved by rationally designing polyacrylamide and adding specific functional groups. Future research will further explore the effects of different functional groups on floc strength and how to improve the efficiency of flocculants by optimizing the formula.

[0109] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A flocculant for oily wastewater, characterized in that: The raw materials include, by weight: 1-2 parts of tetraethyl orthosilicate, 0.2-0.4 parts of citric acid, 1-2 parts of MOFs precursor, 0.1-0.2 parts of zinc chloride, 0.2-0.4 parts of ethylenediamine, 2-4 parts of polyacrylamide, 0.2-0.4 parts of acrylic acid, and 0.1-0.2 parts of toluene diisocyanate; The MOFs precursor contains Zn 2+ A mixture of material and 2-methylimidazole; the Zn-containing 2+ The material is one of zinc nitrate, zinc chloride, zinc sulfate, zinc oxide and zinc acetate; Prepared by the following steps: S1. Dissolve tetraethyl orthosilicate in deionized water, add hydrochloric acid, stir, stand in a constant temperature water bath, add citric acid, stir, ultrasonicate, adjust the pH value of the system to 4-5, and dry to obtain a carboxylated aerogel; S2, dissolving the MOFs precursor in deionized water, adding zinc chloride, stirring, adding ethylenediamine, ultrasonication, adjusting the pH value of the system to 7.5-8, standing in a constant temperature water bath, and drying to obtain amino-modified MOFs; S3, dissolving polyacrylamide in deionized water, stirring, adding acrylic acid, stirring, ultrasonicating, adding toluene diisocyanate, adjusting the pH value of the system to 8-8.5, standing in a constant temperature water bath, and drying to obtain graft-modified polyacrylamide; S4. Dissolve the modified polyacrylamide in deionized water, stir, add carboxyl aerogel and amino modified MOFs, stir, sonicate, adjust the pH value of the system to 7-7.5, let stand in a constant temperature water bath, dry, press through a granulator for 0.5-1h, the pressing pressure is 30-40MPa, the pressing temperature is 80-100℃, and sieve to obtain a flocculant for oily wastewater.

2. A method for preparing a flocculant for oily wastewater according to claim 1, characterized in that: The steps include: S1. Dissolve tetraethyl orthosilicate in deionized water, add hydrochloric acid, stir, stand in a constant temperature water bath, add citric acid, stir, ultrasonicate, adjust the pH value of the system to 4-5, and dry to obtain a carboxylated aerogel; S2, dissolving the MOFs precursor in deionized water, adding zinc chloride, stirring, adding ethylenediamine, ultrasonication, adjusting the pH value of the system to 7.5-8, standing in a constant temperature water bath, and drying to obtain amino-modified MOFs; S3, dissolving polyacrylamide in deionized water, stirring, adding acrylic acid, stirring, ultrasonicating, adding toluene diisocyanate, adjusting the pH value of the system to 8-8.5, standing in a constant temperature water bath, and drying to obtain graft-modified polyacrylamide; S4. Dissolve the modified polyacrylamide in deionized water, stir, add carboxyl aerogel and amino modified MOFs, stir, sonicate, adjust the pH value of the system to 7-7.5, let stand in a constant temperature water bath, dry, press through a granulator for 0.5-1h, the pressing pressure is 30-40MPa, the pressing temperature is 80-100℃, and sieve to obtain a flocculant for oily wastewater.

3. The method for preparing a flocculant for oily wastewater according to claim 2, characterized in that: In S1, hydrochloric acid with a concentration of 1-1.5 mol / L is used to adjust the pH value of the system.

4. The method for preparing a flocculant for oily wastewater according to claim 2, characterized in that: In S1, the stirring time is 0.5-1.5h, and the stirring speed is 500-700r / min.

5. The method for preparing a flocculant for oily wastewater according to claim 2, characterized in that: In S2, a sodium hydroxide solution with a concentration of 1-1.5 mol / L is used to adjust the pH value of the system.

6. The method for preparing a flocculant for oily wastewater according to claim 2, characterized in that: In S2, the stirring time is 0.5-1h, and the stirring speed is 800-1000r / min.

7. The method for preparing a flocculant for oily wastewater according to claim 2, characterized in that: In S2, the ethylenediamine is added at a rate of 10-15% per minute based on the total weight of ethylenediamine.

8. The method for preparing a flocculant for oily wastewater according to claim 2, characterized in that: In S3, based on the total weight of toluene diisocyanate, the toluene diisocyanate is added at a rate of 20-25% per minute.

9. The method for preparing a flocculant for oily wastewater according to claim 2, characterized in that: In S4, the temperature of the constant temperature water bath is 50-60°C, and the time of the constant temperature water bath is 3-5h.

10. The method for preparing a flocculant for oily wastewater according to claim 2, characterized in that: In S4, the drying time is 24-30 hours and the drying temperature is 60-80°C.

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