A flocculant for industrial wastewater treatment and a preparation method thereof

Abstract

The application discloses a flocculant for industrial wastewater treatment and a preparation method thereof. The flocculant is composed of urethane-based silane, silicon dioxide and polyethylene polymer with a mass ratio of 2-3:1-2:10. The preparation method comprises the following steps: mixing urethane-based silane modified silicon dioxide and polyethylene polymer according to a ratio of 2-3:10, and then reacting at 200-220 DEG C for 2-3 hours to obtain polyethylene containing modified silicon dioxide; and then processing the polyethylene containing modified silicon dioxide by a melt extrusion method to obtain the target flocculant. In the melt extrusion process, the temperature is controlled to be 210-230 DEG C, the rotating speed of the extruder is controlled to be 300-500 rpm, and the processing pressure is controlled to be 0.5-1.5 MPa. The flocculant provided by the application has a removal rate of Cu 2+ , Pb 2+ , Cr 3+ , Zn 2+ , Cd 2+ and COD in industrial wastewater all reaching above 97%, and is suitable for popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical industry, and particularly relates to a flocculant for industrial wastewater treatment and a preparation method thereof. BACKGROUND

[0002] The flocculant is a water treatment agent that can promote the aggregation of suspended particles in water into flocs and accelerate sedimentation. In the field of water treatment, the flocculant plays a crucial role, especially in removing suspended solids, adjusting water quality, and promoting solid-liquid separation. With the acceleration of industrialization and urbanization, water pollution problems are becoming increasingly serious, and the demand for flocculants is also increasing.

[0003] Silica-based flocculants are inorganic polymer flocculants composed of silica and other oxides, mainly used for removing suspended solids, colloids, and organic matter and other pollutants in water. However, its limitations need to be noted during use. The application range of this flocculant is limited, and the removal effect of heavy metals is not good. A large amount of flocculant needs to be used to achieve good flocculation effect, or other treatment methods need to be combined to improve the treatment effect. At the same time, factors such as suspended solids, hardness, and alkalinity in water will also affect the flocculation effect of silica-based flocculants, and it is difficult to recover from water after use, which will cause a certain waste of resources.

[0004] Polyethylene-based flocculants are organic polymer flocculants, and their performance will be affected by the environment. At high temperatures, the activity of flocculant molecules decreases, reducing their flocculation effect. In high salinity environments, the effect of polyethylene-based flocculants will be inhibited to some extent. This is because salinity will affect the interaction between the flocculant and the pollutants. The adsorption capacity of polyethylene-based flocculants is affected by the type and chemical properties of heavy metal ions. Different heavy metal ions have different charges, radii, and chemical properties, resulting in differences in their binding capacity and selectivity with flocculants, making the adsorption capacity of polyethylene-based flocculants for heavy metal ions relatively low. When treating high-concentration heavy metal wastewater, a large amount of flocculant needs to be used or multiple adsorption treatments need to be performed to achieve sufficient removal effect.

[0005] The present application aims to provide a silica composite polyethylene flocculant for heavy metal treatment of industrial wastewater. SUMMARY

[0006] The first object of the present application is to provide a flocculant for industrial wastewater treatment, and the second object of the present application is to provide a preparation method of the flocculant.

[0007] The first object of the present application is achieved by a flocculant for industrial wastewater treatment, which is composed of urethane-based silane, silica, and polyethylene polymer with a mass ratio of 2-3:1-2:10.

[0008] The second object of the present application is achieved in that the preparation method of the flocculant is achieved in particular as follows:

[0009] 1) urethane-based silane modified silica: silica powder is added to a wax-water mixture at 60-70°C, ultrasonically treated at a power of 50000-60000 Hz for 1-2 h, then cooled to room temperature, urethane-based silane is added, and stirring is continued for 3-4 h; then, the modified silica is obtained by centrifugation, deionized water washing, and drying;

[0010] 2) the modified silica is mixed with polyethylene high polymer at a ratio of 2-3:10, and then reacted at 200-220°C for 2-3 h to obtain polyethylene containing modified silica, and the polyethylene containing modified silica is processed by a melt extrusion method to obtain the target flocculant; during the melt extrusion process, the temperature is controlled at 210-230°C, the extruder speed is 300-500 rpm, and the processing pressure is 0.5-1.5 MPa.

[0011] In step 2), the preparation method of the polyethylene high polymer is to mix low-density polyethylene and an initiator at a ratio of 100:0.1-1, then stir at a speed of 200-300 rpm for 10-20 min, and then polymerize at 80-90°C for 8-10 h; the obtained precipitate is filtered, washed, dried, and crushed to obtain the polyethylene high polymer.

[0012] Silica is one of the most abundant resources on earth, easy to obtain, low cost, and has good thermal stability and chemical stability, not easy to be hydrolyzed, suitable for long-term use. Silica particles have a large specific surface area and good mechanical strength, and can maintain stable flocculation effect even under strong stirring. The silica flocculant has good dispersibility in water and can effectively capture suspended solids after forming flocs. The present application introduces various functional groups such as hydroxyl and thiol into silica through chemical modification, which can enhance its flocculation performance and effectively adsorb heavy metal ions, which is beneficial to the removal of heavy metal ions in water treatment. The present application uses wax water modified silica shell to coat polyethylene high polymer matrix to obtain a flocculant with excellent heavy metal ion removal performance. The silica shell has good acid and alkali resistance, can provide additional protection and stability, reduce the degradation or inactivation of polyethylene high polymer in solution, can maintain stability in a wide pH range, and is suitable for various water quality conditions, thereby improving the service life and effect of the flocculant and widening the application range of the flocculant. The silica shell modified by mercaptoacetic acid can improve the flocculation performance of the flocculant, so that it can more effectively remove suspended solids, colloids and organic matter and other impurities.

[0013] The flocculant provided by the present application can remove Cu2+ Pb 2+ Cr 3+ Zn 2+ Cd 2+ COD removal rate is as high as 97% or more, which is significantly better than commercially available polyvinyl amide flocculants, and is suitable for popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Microscopic picture of the flocculant prepared in Example 1. DETAILED DESCRIPTION

[0015] The application will be further described in detail below in combination with the drawings and examples, but the application is not limited in any way by the description, and any transformation or improvement based on the teaching of the application falls within the protection scope of the application.

[0016] The application is a flocculant for industrial wastewater treatment, which is composed of urethane-based silane, silicon dioxide and polyethylene polymer with a mass ratio of 2-3:1-2:10.

[0017] The flocculant further comprises mercaptoacetic acid.

[0018] The application further provides a preparation method of the flocculant, which is specifically implemented according to the following steps:

[0019] 1) Urethane-based silane modified silicon dioxide: silicon dioxide powder is added into a wax-water mixture at 60-70℃ and ultrasonically treated at a power of 50000-60000 Hz for 1-2 h, then cooled to room temperature, urethane-based silane is added, and stirring is continued for 3-4 h; then, the modified silicon dioxide is obtained by centrifugation, deionized water washing and drying;

[0020] 2) The modified silicon dioxide and polyethylene polymer are mixed in a ratio of 2-3:10, and then reacted at 200-220℃ for 2-3 h to obtain polyethylene containing modified silicon dioxide, and the target flocculant is obtained by melt extrusion of the polyethylene containing modified silicon dioxide; during the melt extrusion process, the temperature is controlled at 210-230℃, the extruder speed is 300-500 rpm, and the processing pressure is 0.5-1.5 MPa.

[0021] In step 2), the preparation method of the polyethylene polymer is to mix low-density polyethylene and initiator in a ratio of 100:0.1-1, then stir at a speed of 200-300 rpm for 10-20 min, and then polymerize at 80-90℃ for 8-10 h, and the obtained precipitate is filtered, washed, dried and crushed to obtain the polyethylene polymer.

[0022] In step 2), the initiator is hydrogen peroxide.

[0023] In step 1), the preparation method of the wax-water mixture is to melt the paraffin wax and then add it to water at 60-70°C, stir until uniform to obtain a wax-water mixture, and the mass ratio of paraffin wax to water is 1:3.

[0024] In step 2), 20-30 g / L of mercaptoacetic acid is added to the flocculant obtained in step 1), and after mixing, it is reacted at room temperature for 2-3 h and stirred at a stirring speed of 200-220 rpm to obtain a mercaptoacetic acid modified flocculant.

[0025] In step 2), 20-30 g / L of mercaptoacetic acid is added to the flocculant obtained in step 1), and after mixing, it is reacted at room temperature for 2-3 h and stirred at a stirring speed of 200-220 rpm to obtain a mercaptoacetic acid modified flocculant.

[0026] Example 1

[0027] 100 g of paraffin wax was melted in a 60°C water bath at a stirring speed of 400 rpm, then added to 300 g of water at 60°C, and stirred at a speed of 50 rpm for 30 min to obtain a wax-water mixture.

[0028] 10 g of 20 nm diameter silica powder was slowly added to the wax-water mixture, and ultrasonically treated at a power of 50,000 hz for 1 h to ensure uniformity of the system. Silica particles with surface energy between the two liquids will be adsorbed to the liquid-liquid interface. Then cooled to 25°C to solidify the wax phase and lock the particles in place. Subsequently, 20 g of urethane-based silane (AMCS) was added to modify the surface of the silica in the wax-water system, and maintained for 3 h. After modification, the urethane-based silane modified silica was obtained by centrifugation, deionized water washing, drying.

[0029] 100 g of low-density polyethylene and 0.1 g of initiator, i.e., hydrogen peroxide (H2O2), were mixed at a stirring speed of 200 rpm for 10 min to ensure uniform distribution of the initiator in the monomer. After mixing, the polymerization reaction was carried out at a temperature of 80°C for 8 h. After the reaction was completed, the product was removed from the reactor, precipitated, filtered, washed, dried, and crushed to obtain a polyethylene polymer.

[0030] 20 g of urethane-based silane modified silica was mixed with 100 g of polyethylene matrix and reacted at 200°C for 2 h to obtain polyethylene containing modified silica, which was then processed into a flocculant by melt extrusion method. Figure 1 Figure 1 ​It can be seen that the modified silica is attached to the surface of the polyethylene polymer. During the melt extrusion process, the temperature is controlled at 220 ℃ to ensure that the modified silica is fully mixed with the polyethylene. At the same time, the speed of the extruder is adjusted to 400 rpm, and the processing pressure is controlled at 1 MPa to ensure the structural stability and performance reliability of the flocculant.

[0031] To further improve the removal efficiency of heavy metal ions, 200 ml of mercaptoacetic acid (MEA) with a concentration of 20 g / L is mixed with 10 g of the obtained flocculant. The unmodified surface of the silica is fully contacted with the MEA to introduce thiol functional groups. The reaction is carried out at 25 ℃ for 2 h with stirring at a speed of 200 rpm. The mercaptoacetic acid modified flocculant is obtained.

[0032] Example 2

[0033] After melting 100 g of paraffin at 65 ℃ in a water bath with stirring at a speed of 400 rpm, it is added to 300 g of water at 60 ℃, and stirred at a speed of 50 rpm for 30 min to obtain a wax-water mixture.

[0034] 15 g of silica powder with a particle size of 30 nm is slowly added to the wax-water mixture, and ultrasonic treatment is carried out at a power of 55000 hz for 1.5 h to ensure uniformity of the system. Silica particles with surface energy between the two liquids will be adsorbed to the liquid-liquid interface. Then, it is cooled to 25 ℃ to solidify the wax phase and lock the particles in place. Subsequently, 25 g of urethane-based silane (AMCS) is added to modify the surface of the silica in the wax-water system, and maintained for 3.5 h. After the modification is completed, the urethane-based silane modified silica is obtained by centrifugation, deionized water washing, drying.

[0035] 100 g of low-density polyethylene and 0.5 g of initiator, i.e., hydrogen peroxide (H2O2), are mixed with stirring at a speed of 250 rpm for 15 min to ensure uniform distribution of the initiator in the monomer. After mixing uniformly, the polymerization reaction is carried out at a temperature of 85 ℃ for 9 h. After the reaction is completed, the product is taken out of the reactor, precipitated, filtered, washed, dried, and crushed to obtain a polyethylene polymer.

[0036] After mixing 25 g of urethane-based silane modified silica with 100 g of polyethylene matrix, the modified silica-containing polyethylene is obtained by reacting at 210 ℃ for 2.5 h. The modified silica-containing polyethylene is then processed into a flocculant by melt extrusion. During the melt extrusion process, the temperature is controlled at 210 ℃ to ensure that the modified silica is fully mixed with the polyethylene. At the same time, the speed of the extruder is adjusted to 300 rpm, and the processing pressure is controlled at 0.5 MPa to ensure the structural stability and performance reliability of the flocculant.

[0037] To further enhance the removal efficiency of heavy metal ions, 220 ml of mercaptoacetic acid (MEA) with a concentration of 25 g / L was mixed with 10 g of the obtained flocculant, the unmodified surface of the silica was fully contacted with the MEA to introduce thiol functional groups, and the reaction was carried out at 30 °C for 2.5 h with stirring at a stirring speed of 210 rpm, to obtain a mercaptoacetic acid modified flocculant.

[0038] Example 3

[0039] After 100 g of paraffin was melted in a 70 °C water bath at a stirring speed of 600 rpm, it was added to 300 g of water at 60 °C, and stirred at a speed of 60 rpm for 30 min to obtain a wax-water mixture.

[0040] 20 g of silica powder with a particle size of 50 nm was slowly added to the wax-water mixture, and ultrasonic treatment was carried out at a power of 60,000 hz for 2 h to ensure uniformity of the system. Silica particles with surface energy between the two liquids will be adsorbed onto the liquid-liquid interface. Then, it was cooled to 25 °C to solidify the wax phase and lock the particles in place. Subsequently, 30 g of urethane-based silane (AMCS) was added to modify the surface of the silica in the wax-water system, and maintained for 4 h. After the modification was completed, the urethane-based silane modified silica was obtained by centrifugation, deionized water washing, drying.

[0041] 100 g of low-density polyethylene and 1 g of initiator, i.e., hydrogen peroxide (H2O2), were mixed at a stirring speed of 300 rpm for 20 min to ensure uniform distribution of the initiator in the monomer. After uniform mixing, the polymerization reaction was carried out at a temperature of 90 °C for 10 h. After the reaction was completed, the product was taken out of the reactor, and after precipitation, it was subjected to filtration, washing, drying and crushing treatment to obtain a polyethylene polymer.

[0042] After 30 g of urethane-based silane modified silica was mixed with 100 g of a polyethylene matrix, the polyethylene containing modified silica was obtained by reacting at 220 °C for 3 h, and the polyethylene containing modified silica was processed into a flocculant by a melt extrusion method. In the melt extrusion process, the temperature was controlled at 230 °C to ensure that the modified silica was fully mixed with the polyethylene. At the same time, the rotation speed of the extruder was adjusted to 500 rpm, and the processing pressure was controlled at 1.5 MPa to ensure the structural stability and performance reliability of the flocculant.

[0043] To further improve the removal efficiency of heavy metal ions, 240 ml of mercaptoacetic acid (MEA) with a concentration of 30 g / L was mixed with 10 g of flocculant, the unmodified surface of the silica was fully contacted with the MEA to introduce thiol functional groups, and the reaction was carried out at 40°C for 3 h with stirring at a stirring speed of 220 rpm, to obtain the mercaptoacetic acid modified flocculant.

[0044] Comparative Example 1

[0045] 100 g of low-density polyethylene and 0.5 g of initiator, i.e., hydrogen peroxide (H2O2), were mixed at a stirring speed of 250 rpm for 15 min to ensure uniform distribution of the initiator in the monomer. After uniform mixing, the polymerization reaction was carried out at a temperature of 85°C for 9 h. After completion of the reaction, the product was taken out of the reactor, precipitated, and then subjected to filtration, washing, drying, and crushing processes to obtain polyethylene macromolecules. 10 g of the polyethylene macromolecules was mixed with 220 ml of mercaptoacetic acid (MEA) with a concentration of 25 g / L, and the reaction was carried out at 30°C for 2.5 h with stirring at a stirring speed of 210 rpm to obtain the flocculant.

[0046] Detection Example

[0047] The wastewater treatment effects of the mercaptoacetic acid modified flocculants prepared in Examples 1-3, the polyethylene macromolecules of Example 1 without mixing with silica, the flocculant of Example 1 without modification with mercaptoacetic acid, and a commercially available polyethylene imine flocculant were detected.

[0048] Method: A certain industrial wastewater was taken as a sample, and 0.01 g of the performance enhanced flocculant prepared in Examples 1-3, the polyethylene macromolecules of Example 1 without mixing with silica, the flocculant of Example 1 without modification with mercaptoacetic acid, and a commercially available polyethylene imine flocculant were respectively added to 100 ml of the industrial wastewater, and stirred at a speed of 300 rpm for 30 min. The removal rates of Cu 2+ , Pb 2+ , Cr 3 + , Zn 2+ , Cd 2+ , and chemical oxygen demand (COD) in each group of wastewater were detected, and the specific results are shown in Table 1.

[0049] Table 1 Removal rates of Cu 2+ , Pb 2+ , Cr 3+ , Zn 2+ , Cd 2+ , and COD in the industrial wastewater of the performance enhanced flocculants prepared in Examples 1-3

[0050]

[0051] From table 1, the flocculant prepared by the application without mercaptoacetic acid modification has better removal rate of Cu 2+ , Pb 2+ , Cr 3+ , Zn 2+ , Cd 2+ , COD than the commercially available polyvinylamide flocculant, and the flocculant modified by mercaptoacetic acid has much better removal rate of Cu 2+ , Pb 2+ , Cr 3+ , Zn 2+ , Cd 2+ , COD than the commercially available polyvinylamide flocculant.

Claims

1. A method for preparing a flocculant for industrial wastewater treatment, characterized by, The preparation method comprises the following steps: 1) urethane-silane modified silica: the silica powder is added into a wax-water mixture at 60-70 DEG C, and is ultrasonically treated at a power of 50000-60000 Hz for 1-2 h, and then is cooled to room temperature, and the urethane-silane is added, and the stirring is continued for 3-4 h; then, the modified silica is obtained by centrifugation, deionized water washing and drying; 2) the modified silica and the polyethylene high polymer are mixed at a ratio of 2-3:10, and then are reacted at 200-220 DEG C for 2-3 h to obtain the polyethylene containing the modified silica, and then the polyethylene containing the modified silica is processed by a melt extrusion method to obtain the target flocculant; in the melt extrusion process, the temperature is controlled to be 210-230 DEG C, the extruder rotating speed is controlled to be 300-500 rpm, and the processing pressure is controlled to be 0.5-1.5 MPa.

2. The method of claim 1, wherein the flocculant is prepared by the steps of: In the step 2), the polyethylene high polymer is prepared by mixing the low-density polyethylene and the initiator at a ratio of 100:0.1-1, and then stirring at a speed of 200-300 rpm for 10-20 min, and then polymerizing at 80-90 DEG C for 8-10 h, and then filtering, washing, drying and crushing the obtained precipitate to obtain the polyethylene high polymer.

3. The method of claim 1, wherein the flocculant is prepared by the steps of: In the step 1), the wax-water mixture is prepared by melting the paraffin wax, and then adding the paraffin wax into water at 60-70 DEG C, and then stirring to obtain the wax-water mixture, and the mass ratio of the paraffin wax to water is 1:

3.

4. The method of claim 2, wherein the flocculating agent is prepared by the steps of: In the step 2), the initiator is hydrogen peroxide.

5. The method for preparing the flocculant according to claim 1, characterized in that, The mercaptoacetic acid modified flocculant is obtained by adding the mercaptoacetic acid with a concentration of 20-30 g / L into the flocculant obtained in the step 2), and then uniformly mixing, and then reacting at room temperature for 2-3 h, and then stirring at a stirring speed of 200-220 rpm; wherein, the mass-volume ratio of the flocculant to the mercaptoacetic acid is 1:22-24 g / ml.

6. The flocculating agent prepared according to the method of claim 1, characterized in that, The flocculant is composed of the urethane-silane, the silica and the polyethylene high polymer at a mass ratio of 2-3:1-2:

10.

7. The flocculating agent of claim 6, wherein The flocculant further comprises the mercaptoacetic acid.

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