Preparation method of flocculant based on photosensitizer for enhancing visible light initiation
Technical Field
The invention belongs to the technical field of sewage treatment, and particularly relates to a preparation method of a flocculant based on photosensitizer enhanced visible light initiation.
Background
Water is a valuable natural and strategic resource, and plays an indispensable role in urban construction, industrial production, economic development and the well-being and happiness industry of people. Under the large background of water resource shortage, a large amount of municipal sewage and industrial sewage are directly or indirectly discharged into rivers, lakes and seas, so that the fresh water resources are seriously polluted, and the increasingly prominent problems of water resource shortage and pollution thereof are gradually developed to become one of the main obstacles restricting the development of the economic society of China and further improving the living standard of people. The common water treatment technologies mainly comprise methods such as filtration, flocculation, activated carbon adsorption, ion exchange resin, membrane separation, advanced oxidation, an electrochemical method, magnetization treatment, biological immobilization and the like. The flocculation method is the core part of the water treatment process, and is widely adopted due to the advantages of high efficiency, good applicability, low manufacturing cost, convenient use and the like. Free radical polymerization is a main mechanism in the preparation process of the flocculant, the chain growth of the free radical photopolymerization is mainly completed through the double bond addition reaction of acrylate or acrylamide monomers, the monomer types are few, and oxygen has certain inhibition on visible photopolymerization; therefore, free radical polymerization has certain limitations in both initiation efficiency and flocculation effect. It is therefore of great importance to explore other polymerization systems to improve various aspects of flocculant efficiency.
The development of cationic photopolymerization technology was relatively late and was formally proposed in the 80's of the 20 th century. In the cationic initiation process, the cationic initiator photolyzes to form a protonic acid or Lewis acid, which then initiates cationic polymerization. Compared with free radical photopolymerization, cationic photopolymerization systems have more monomers and are insensitive to oxygen inhibition, and once active cations are generated by radiation excitation, the monomers can be initiated to realize cationic polymerization until the monomers are completely converted even if irradiation is stopped. The photosensitizer absorbs visible light, absorbs the visible light to reach an excited state, and generates active cations by electron transfer with the cation initiator. Cationic polymerization is used for flocculant production but is still in the off-going phase. Therefore, the research and development of the flocculant based on the photosensitizer for strengthening the initiation of the visible light has important significance for enriching and developing the visible light polymerization technology.
Chinese patent application No. CN201510129012.9 discloses a preparation method and application of a composite flocculant for treating coking strong brine wastewater, wherein the preparation method of the composite flocculant comprises the following steps: (1) putting matrix chitosan, a photosensitizer benzophenone, a polymerization inhibitor ammonium ferrous sulfate and a catalyst sulfuric acid into an acrylamide aqueous solution to form a mixed solution, filling nitrogen into the mixed solution to remove oxygen in the mixed solution, irradiating the mixed solution by using an ultraviolet lamp, and adjusting the mixed solution to be alkaline by using sodium hydroxide to obtain a chitosan solution grafted with acrylamide; (2) and mixing the prepared chitosan solution grafted with acrylamide with an aluminum-containing compound, an iron-containing compound, polymeric ferric sulfate, polymeric aluminum chloride and a polyamine compound to obtain the composite flocculant. And adding the prepared composite flocculant into the coking concentrated salt wastewater for treatment. The composite flocculant prepared by the invention has the advantages of good stability, small dosage, good flocculation effect, biodegradability, high treatment efficiency and wide pH application range. The flocculant prepared by the method has single pollutant removal type, and the flocculation capability of the flocculant on other pollutants is still under examination.
Chinese patent application No. CN202110368193.6 discloses a sewage treatment flocculant and a preparation method thereof, wherein the flocculant comprises water, acetone, isopropanol, dimethylacetamide, dimethylformamide, alkali lignosulfonate, cationic polyacrylamide, polymerized aluminum sulfate powder, polyvinyl alcohol, bacillus subtilis, nitrobacteria, potassium hydroxide, sodium bicarbonate, carboxymethyl cellulose, N-isopropyl methacrylamide, N-tert-butyl acrylamide and N-isopropyl acrylamide. Compared with the prior art, the flocculant of the invention has the advantages of no secondary pollution, convenient use, strong flocculation capability, good effects of removing oil and suspended matters, no toxicity and no harm, can replace or partially replace the traditional inorganic polymer and synthetic organic polymer flocculant, has wide application range and has popularization and application values. The preparation method has the advantages of excessive monomer types, application of various solvents, inconsistent water solubility and easy secondary pollution to water bodies.
Therefore, it is necessary to develop a cationic flocculant based on photosensitizer-enhanced visible light initiation, which has the advantages of simple monomer, high initiation efficiency, good stability and good flocculation effect.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a preparation method of a flocculant based on photosensitizer-enhanced visible light initiation, which has the advantages of low energy consumption, simple process, simple monomers, good water solubility and good product stability.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
2- (N, N-dimethylamino) ethyl acrylate (DA) and Acrylamide (AM) are used as raw materials, urea is used as a cosolvent, benzoin ethyl ether is used as a photosensitive initiator, and 4-isobutylphenyl-4' -methylphenyl iodohexafluorophosphate is used as an initiator. Adding the two into a reaction bottle in sequence, adding proper water, and fully mixing and dissolving the three under the condition of rapid stirring; adding urea, stirring quickly, and finally adding benzoin ethyl ether and an isobutyl phenyl-4' -methylphenyl iodohexafluorophosphate initiator in sequence; introducing nitrogen to expel oxygen, and stirring and uniformly mixing; finally, placing the reaction bottle under an LED lamp for reaction; and after the reaction is finished and the product is aged, extracting and purifying the product to obtain the cationic flocculant.
The method specifically comprises the following steps:
1) monomer (b): weighing a certain amount of AM, and placing the AM in pure water to obtain a solution with the concentration of 10-20%; after the mixture is uniformly stirred, a certain amount of DA monomers are weighed in a reaction bottle and uniformly stirred at the temperature of 40-45 ℃, and the concentration of the DA monomers is controlled to be 15-30%.
2) Adding a cosolvent: adding urea with the concentration of 0.01-0.025%, and uniformly stirring until the urea is completely dissolved.
3, adding an initiator: adding photosensitizer benzoin ethyl ether and visible light initiator 4-isobutylphenyl-4 '-methylphenyl iodohexafluorophosphate into a reaction bottle, wherein the concentration of the benzoin ethyl ether in the mixed solution is 0.125% -0.5%, and the concentration of the 4-isobutylphenyl-4' -methylphenyl iodohexafluorophosphate is 0.2% -0.6%; then nitrogen is introduced to drive out oxygen;
4) visible light illumination and reaction: and finally, placing the mixed solution under a 200-400W visible light lamp for irradiation reaction for 1-2 h. And (4) aging, and then extracting and purifying the product to obtain the flocculant.
Wherein: in the step 1), the concentration of AM is 10-20%, and the concentration of DA monomer is 15-30%. When the AM concentration is less than 10%, the overall polymerization activity of the monomer is not high enough, the polymerization reaction is not completely carried out, and the polymerization product with lower molecular weight is in an apparent form or even in a semifluid state; when the AM concentration is greater than 20%, the functionality of DA in the flocculant is lost, ensuring that it has a certain content. When the DA concentration is less than 15%, the molecular weight and the intrinsic viscosity of the flocculant are too low, so that the initiation efficiency is influenced; when the DA concentration is more than 30%, an excess of DA monomer interferes with the generation of active cations.
And 2) under the condition of appropriate dosage of the cosolvent urea, the generation of hydrogen bonds can be prevented, the crosslinking probability is reduced, and the aim of increasing the product solubility is fulfilled. The urea is uneconomically used in an excessive amount and may affect the flocculation property if the urea acts as a chain transfer agent to lower the intrinsic viscosity of the product.
And 3) the concentration of benzoin ethyl ether in the mixed solution is 0.125-0.5%, and the concentration of the initiator 4-isobutylphenyl-4' -methylphenyl iodohexafluorophosphate in the mixed solution is 0.2-0.6%. When the adding concentration of benzoin ethyl ether is less than 0.125%, the amount of the photosensitive initiator is too small, and sufficient light energy is difficult to absorb to reach an excited state and generate electron transfer with a cationic initiator, so that the initiation efficiency is influenced; when the adding concentration of benzoin ethyl ether is more than 0.5%, the initiation efficiency is not greatly improved and is not economical. When the adding concentration of the 4-isobutylphenyl-4' -methylphenyl iodohexafluorophosphate is less than 0.2 percent, less active cations are generated to initiate monomer polymerization when electron transfer occurs, and the initiation efficiency is influenced; when the adding concentration of the 4-isobutylphenyl-4' -methylphenyliodohexafluorophosphate is more than 0.6 percent, the initiation efficiency is not greatly improved and is uneconomical.
In the step 4), the visible light illumination time is 1-2 h, and the power of the LED lamp is 200-400W. Benzoin ethyl ether absorbs enough light energy under the irradiation of visible light to reach an excited state to generate electron transfer with a cation initiator, and active cations are generated. However, when the power of the LED lamp is lower than 200W, the time required for initiating the copolymerization reaction is increased, and the reaction efficiency is reduced; and when the power of the LED lamp is higher than 400W, the molecular weight of the product is not obviously increased, and the energy consumption is increased. When the illumination time is less than 1h, the monomers are not completely copolymerized; and after 2 hours, the molecular weight and the performance of the product cannot be obviously improved, and the energy consumption is larger and uneconomical.
Compared with the prior art, the invention has the following beneficial effects:
1. the preparation method has the advantages of simple operation, high production efficiency, low production cost and good stability;
2. the cationic flocculant obtained by the invention has good water solubility, simple monomer, good flocculation effect and strong functionality;
3. the invention replaces the traditional free radical polymerization system with cationic polymerization, thereby avoiding the defects of few free radical polymerization monomers, oxygen inhibition and the like, and obtaining certain breakthrough on the initiation performance and flocculation performance of the flocculant. Therefore, the flocculant initiated by the intensified visible light based on the photosensitizer has good social and economic benefits in practical application.
Detailed Description
The present invention will be described in further detail with reference to specific examples, wherein the raw materials used are common commercial products unless otherwise specified.
Example 1:
1) weighing a certain amount of AM, and placing the AM in pure water to obtain a solution with the concentration of 10%; after the mixture is stirred uniformly, a certain amount of DA monomer is weighed in the reaction bottle and is added and stirred uniformly, and the concentration of the DA monomer is controlled to be 15%.
2) Then, 0.01% urea is added and stirred uniformly until the urea is completely dissolved.
3) Adding benzoin ethyl ether with the concentration of 0.125% in the mixed solution into a reaction bottle, adding an initiator with the concentration of 0.2% in the mixed solution, namely 4-isobutylphenyl-4' -methylphenyliodihexafluorophosphate, and then introducing nitrogen and removing oxygen;
4) and finally, placing the mixed solution under a 200W LED visible light lamp for irradiation reaction for 1 h. And (4) aging, and then extracting and purifying the product to obtain the flocculant.
Example 2:
1) weighing a certain amount of AM, and placing the AM in pure water to obtain a solution with the concentration of 15%; after the mixture is stirred uniformly, a certain amount of DA monomer is weighed in the reaction bottle and is added and stirred uniformly, and the concentration of the DA monomer is controlled to be 20%.
2) Then, 0.015% of urea is added and stirred uniformly until the urea is completely dissolved.
3) Adding benzoin ethyl ether with the concentration of 0.2% in the mixed solution into a reaction bottle, adding an initiator with the concentration of 0.3% in the mixed solution, namely 4-isobutylphenyl-4' -methylphenyliodihexafluorophosphate, and then introducing nitrogen and removing oxygen;
4) and finally, placing the mixed solution under a 300W LED visible light lamp for irradiation reaction for 2 h. And (4) aging, and then extracting and purifying the product to obtain the flocculant.
Example 3:
1) weighing a certain amount of AM, and placing the AM in pure water to obtain a solution with the concentration of 20%; after the mixture is stirred uniformly, a certain amount of DA monomer is weighed in the reaction bottle and is added and stirred uniformly, and the concentration of the DA monomer is controlled to be 30%.
2) Then, 0.02% urea was added and stirred until completely dissolved.
3) Adding benzoin ethyl ether with the concentration of 0.3% in the mixed solution into a reaction bottle, adding an initiator with the concentration of 0.4% in the mixed solution, namely 4-isobutylphenyl-4' -methylphenyliodihexafluorophosphate, and then introducing nitrogen and removing oxygen;
4) and finally, placing the mixed solution under a 400W LED visible light lamp for irradiation reaction for 1 h. And (4) aging, and then extracting and purifying the product to obtain the flocculant.
Example 4:
1) weighing a certain amount of AM, and placing the AM in pure water to obtain a solution with the concentration of 15%; after the mixture is stirred uniformly, a certain amount of DA monomer is weighed in the reaction bottle and is added and stirred uniformly, and the concentration of the DA monomer is controlled to be 25%.
2) Then adding urea with the concentration of 0.025 percent, and stirring uniformly until the urea is completely dissolved.
3) Adding benzoin ethyl ether with the concentration of 0.4% in the mixed solution into a reaction bottle, adding an initiator with the concentration of 0.5% in the mixed solution, namely 4-isobutylphenyl-4' -methylphenyliodihexafluorophosphate, and then introducing nitrogen and removing oxygen;
4) and finally, placing the mixed solution under a 300W LED visible light lamp for irradiation reaction for 2 h. And (4) aging, and then extracting and purifying the product to obtain the flocculant.
Example 5:
1) weighing a certain amount of AM, and placing the AM in pure water to obtain a solution with the concentration of 10%; after the mixture is stirred uniformly, a certain amount of DA monomer is weighed in the reaction bottle and is added and stirred uniformly, and the concentration of the DA monomer is controlled to be 20%.
2) Then, 0.02% urea was added and stirred until completely dissolved.
3) Adding benzoin ethyl ether with the concentration of 0.5% in the mixed solution into a reaction bottle, adding an initiator with the concentration of 0.6% in the mixed solution, namely 4-isobutylphenyl-4' -methylphenyliodihexafluorophosphate, and then introducing nitrogen and removing oxygen;
4) and finally, placing the mixed solution under a 200W LED visible light lamp for irradiation reaction for 1 h. And (4) aging, and then extracting and purifying the product to obtain the flocculant.
The intrinsic viscosity and the kaolin removal rate of the organic polymeric flocculants prepared in examples 1 to 5 were measured, and the data are shown in table 1.
TABLE 1 Performance parameters of organic polymeric flocculants
Product performance
|
Intrinsic viscosity (dL/g)
|
Kaolin wastewater removal (%)
|
Example 1
|
11.72
|
96.7
|
Example 2
|
11.95
|
97.1
|
Example 3
|
12.23
|
97.5
|
Example 4
|
12.15
|
97.3
|
Example 5
|
11.85
|
96.8 |
As can be seen from the above table 1, the flocculant prepared by the method for preparing a flocculant based on photosensitizer enhanced visible light initiation has excellent and stable product performance, good intrinsic viscosity range and good treatment effect on kaolin wastewater. Thus, the method is a practical and excellent method for preparing the organic polymeric flocculant.
Finally, it should be noted that the above-mentioned examples of the present invention are only examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. Variations and modifications in other variations will occur to those skilled in the art upon reading the foregoing description. Not all embodiments are exhaustive. All obvious changes and modifications of the present invention are within the scope of the present invention.