Flocculating agent and sludge dewatering and solidification treatment process

Abstract

The application relates to the technical field of sludge dewatering treatment, and more particularly to a flocculating agent and a sludge dewatering and solidification treatment process.A flocculating agent comprises the following raw materials in parts by weight: 16-20 parts of chitin, 4-6 parts of an Aspergillus fermentation liquor, 2-3 parts of PLA-g-CS, 10-12 parts of an epoxy group quaternary ammonium salt and 8-12 parts of a calcium salt, the Aspergillus fermentation liquor contains Aspergillus niger and Aspergillus nidulans, and the PLA-g-CS is prepared from carboxyl-terminated polylactic acid grafted chitosan.The flocculating agent PLA-g-CS of the application serves as a growth carrier for Aspergillus niger and Aspergillus nidulans in the Aspergillus fermentation liquor, and chitin and quaternary ammonium salt groups are introduced at chitosan on the PLA-g-CS, so that the flocculating agent obtains stronger flocculation effect, and the flocculating agent has better biodegradability, reducing the pollution of the flocculating agent to the environment.

Description

Technical Field

[0001] This application relates to the technical field of mud and sludge dewatering treatment, and more specifically, to a flocculant and a mud and sludge dewatering and solidification treatment process. Background Technology

[0002] Silt is a type of soft soil with a flocculent or honeycomb structure formed by sedimentation in still or slow-moving water. Silt has a high water content and numerous natural pores, resulting in relatively poor mechanical strength. Mud slurry, on the other hand, is a mixture of silt and mud. Mud slurry has a much higher water content than silt, meaning that both have virtually no strength. Therefore, silt and mud slurry are difficult to prepare for engineering applications, and their direct disposal would lead to a significant waste of land resources.

[0003] Currently, the treatment of sludge slurry usually adopts a dehydration and solidification process, which involves adding flocculants to the sludge slurry and then dehydrating and solidifying the sludge flocs to achieve the recycling of sludge slurry. Flocculants can be mainly divided into inorganic flocculants or organic flocculants.

[0004] Common inorganic flocculants include polyferric chloride, polyferric sulfate, polyaluminum chloride, and polyaluminum sulfate. However, these inorganic flocculants are used in large quantities, and iron and aluminum ions can easily cause secondary pollution.

[0005] Common organic flocculants include polyacrylamide flocculants (PAM) and cationic polyacrylamide flocculants (CPAM). Although these organic flocculants require small dosages and have strong flocculation capabilities, they have high dosage requirements. If too much of these organic flocculants is used, the excessive amount can easily cause harm to humans and the ecological environment.

[0006] Therefore, there is an urgent need for a flocculant with strong flocculation ability that does not easily cause secondary pollution, as well as a process for dewatering and solidifying mud and sludge. Summary of the Invention

[0007] In order to overcome the shortcomings of existing flocculants in achieving both high flocculation and low pollution, this application provides a flocculant and a process for dewatering and solidifying mud and sludge.

[0008] In a first aspect, this application provides a flocculant, which adopts the following technical solution:

[0009] A flocculant comprising the following raw materials in parts by weight: 16-20 parts chitin, 4-6 parts Aspergillus fermentation broth, 2-3 parts PLA-g-CS, 10-12 parts epoxy quaternary ammonium salt and 8-12 parts calcium salt, wherein the Aspergillus fermentation broth contains Aspergillus niger and Aspergillus nidus, and the PLA-g-CS is prepared by grafting chitosan with carboxyl-terminated polylactic acid.

[0010] Through the above technical solution, chitin contains a large number of hydroxyl and amino groups, which can form hydrogen bonds, covalent bonds or coordinate bonds with organic molecules in sludge, such as proteins, amino acids, nucleic acids, phenolic compounds, etc., and thus achieve the flocculation effect; moreover, chitin is biodegradable, non-toxic and harmless, and unlikely to cause secondary pollution to the environment.

[0011] The Aspergillus fermentation broth contains live Aspergillus niger and live Aspergillus nidus. These live Aspergillus niger and live Aspergillus nidus multiply in large quantities on the surface of PLA-g-CS using PLA-g-CS as a carrier. Among them, there are some short hyphae on the surface of Aspergillus niger mycelial balls, and these short hyphae have an adsorption effect on small particles, causing the flocculents to gradually accumulate around PLA-g-CS.

[0012] Furthermore, as Aspergillus niger continues to grow and reproduce, the concentration of its extracellular metabolites on the PLA-g-CS surface is higher than in other areas of the solvent. The extracellular substances produced by Aspergillus niger metabolism are mostly small molecules such as citric acid, gluconic acid, and oxalic acid. These extracellular substances have excellent flocculation effects, which further causes the flocs to gradually accumulate around PLA-g-CS. In addition, both the Aspergillus niger fermentation broth and PLA-g-CS are biodegradable and unlikely to cause secondary pollution to the environment.

[0013] In addition to its excellent flocculation properties, Aspergillus fermentation broth also contains Aspergillus nidulans, which can form chitin deacetase under the induction of chitosan in PLA-g-CS. The chitin deacetase deacetylates some chitin, thereby allowing some chitin to be embedded in PLA-g-CS.

[0014] Because chitosan contains three types of active groups—C2-NH2, C3-OH, and C6-OH—C2-NH2 is a primary amino group with a lone pair of electrons, exhibiting strong nucleophilicity; C3-OH is a secondary hydroxyl group that cannot rotate freely and has significant steric hindrance, resulting in poor activity; and C6-OH is a primary hydroxyl group that can rotate freely in its spatial conformation, exhibiting less steric hindrance and higher activity. Therefore, both C2-NH2 and C6-OH can react with the epoxy groups in the epoxy quaternary ammonium salt, thereby introducing quaternary ammonium salt groups into the chitosan on PLA-g-CS. This effectively increases the flocculation effect of PLA-g-CS, thus promoting a stronger flocculation effect of the flocculant.

[0015] Due to the presence of chitin, Aspergillus fermentation broth, and PLA-g-CS, the amount of epoxy quaternary ammonium salt added is relatively small, which leads to a larger range of flocculant addition amounts, effectively reducing the precision of flocculant dosage and thus reducing the possibility of secondary pollution caused by excessive epoxy quaternary ammonium salt.

[0016] Metal cations can enhance the bridging and charge neutralization effects of flocculants, thereby improving their flocculation effect. Common metal cation additives include ferric salts, aluminum salts, and calcium salts. However, compared to calcium salts, ferric salts and aluminum salts are more likely to cause secondary pollution problems, so calcium salts are relatively superior.

[0017] Preferably, the Aspergillus fermentation broth is a mixture of Aspergillus niger fermentation broth and Aspergillus niger fermentation broth, and the mass ratio of the Aspergillus niger fermentation broth to the Aspergillus niger fermentation broth is (3-5):1.

[0018] Through the above technical solution, if the content of Aspergillus niger fermentation broth is too low, the amount of substances secreted by Aspergillus niger into the extracellular space is insufficient, reducing the flocculation capacity of the flocculant; if the content of Aspergillus niger fermentation broth is too high, the substances secreted by Aspergillus niger into the extracellular space already have sufficient flocculation effect, while the content of Aspergillus nidulans is low, reducing the production of chitin deacetase and reducing the effect of chitin embedding into PLA-g-CS, thereby reducing the flocculation effect of the flocculant. Therefore, after extensive research and experimental verification, the applicant finally determined that the mass ratio of Aspergillus niger fermentation broth to Aspergillus nidulans fermentation broth in this application is preferably as described above.

[0019] Preferably, the preparation method of PLA-g-CS includes the following steps:

[0020] Preparation of carboxyl-terminated polylactic acid: Weigh lactide, water and zinc lactate, mix them evenly, and heat under nitrogen protection to melt the reactants to obtain carboxyl-terminated polylactic acid;

[0021] Preparation of PLA-g-CS: The carboxyl-terminated polylactic acid was dissolved in dimethyl sulfoxide, and 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride and N-hydroxysuccinimide were added. The mixture was stirred at a constant temperature, and chitosan solution was added to react. Impurities were removed by dialysis, precipitate was removed by filtration, and PLA-g-CS was obtained by freeze drying.

[0022] The above technical solution first uses zinc lactate as a catalyst to initiate the ring-opening polymerization of lactide under molten conditions to obtain carboxyl-terminated polylactic acid; then, using 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride and N-hydroxysuccinimide as catalysts, PLA-g-CS is prepared by coupling reaction between the amino group in the CS molecule and the carboxyl group in the carboxyl-terminated polylactic acid.

[0023] Preferably, the mass ratio of the carboxyl-terminated polylactic acid to the chitosan in the chitosan solution is 10:(0.4-0.8).

[0024] Through the above technical solution, if the chitosan content is too high compared to the terminal carboxyl polylactic acid, the self-polymerization reaction of chitosan may dominate, reducing the grafting rate of the terminal carboxyl polylactic acid and thus reducing the flocculation capacity of the flocculant. If the chitosan content is too low compared to the terminal carboxyl polylactic acid, there may not be enough chitosan to graft onto the terminal carboxyl polylactic acid, which will also reduce the flocculation capacity of the flocculant. Therefore, after extensive research and experimental verification, the applicant finally determined that the mass ratio of carboxyl polylactic acid to chitosan in this application is as described above.

[0025] Preferably, the epoxy quaternary ammonium salt is a mixture of 2,3-epoxypropyldodecyldimethylammonium chloride and epioxypropyltrimethylammonium chloride.

[0026] Through the above technical solution, both 2,3-epoxypropyldodecyldimethylammonium chloride and glycidyltrimethylammonium chloride have epoxy and quaternary ammonium salt groups, therefore, both can react with chitosan. Among them, 2,3-epoxypropyldodecyldimethylammonium chloride has long branches, while glycidyltrimethylammonium chloride has short branches, thus promoting PLA-g-CS to have a mixed structure of cationic, long-branched, and short-branched chains. Consequently, when dewatering sludge, the flocculant can form large and dense sludge flocs, that is, the flocculant can have a better flocculation effect. Moreover, the resulting sludge cake has a porous structure, thereby improving the compressibility of the sludge cake and the filterability of water.

[0027] Preferably, the mass ratio of 2,3-epoxypropyldodecyldimethylammonium chloride to epioxypropyltrimethylammonium chloride is (1-3):1.

[0028] Through the above technical solution, if the content of 2,3-epoxypropyldodecyldimethylammonium chloride is too low, the mixed structure of cationic, long-chain, and short-chain branches on the surface of PLA-g-CS will be dominated by short-chain branches, and the overall structure will not be perfect, thus reducing the flocculation ability of the flocculant. If the content of 2,3-epoxypropyldodecyldimethylammonium chloride is too high, the mixed structure of cationic, long-chain, and short-chain branches on the surface of PLA-g-CS will be dominated by long-chain branches, and the overall structure will still not be perfect, similarly reducing the flocculation ability of the flocculant. Therefore, after extensive research and experimental verification, the applicant finally determined that the mass ratio of 2,3-epoxypropyldodecyldimethylammonium chloride to epioxypropyltrimethylammonium chloride in this application should be as described above.

[0029] Secondly, this application provides a method for preparing a flocculant, employing the following technical solution:

[0030] A method for preparing a flocculant, for preparing any one of the above-mentioned flocculants, includes the following steps: first, chitin, Aspergillus fermentation broth and PLA-g-CS are added to a solvent and stirred thoroughly, then an epoxy quaternary ammonium salt is added, and then the mixture is stirred under UVA ultraviolet light to finally obtain the flocculant.

[0031] Through the above technical solutions, in addition to enabling the simpler and more stable introduction of epoxy quaternary ammonium salts onto chitosan, the UVA ultraviolet environment has a very low inhibitory effect on Aspergillus and can also induce mutagenesis in the Aspergillus fermentation broth, thereby improving the stability of Aspergillus niger and Aspergillus nidus in the Aspergillus fermentation broth and indirectly improving the flocculation effect of the flocculant.

[0032] Preferably, when stirring under UVA ultraviolet light, the reaction temperature is 35-40℃ and the reaction time is 8-10h.

[0033] With the above technical solution, when the above reaction temperature and reaction time are used, the epoxy quaternary ammonium salt can be introduced onto chitin more simply and stably, and Aspergillus niger and Aspergillus nidulans in the Aspergillus fermentation broth can be more stable, thereby indirectly improving the flocculation effect of the flocculant.

[0034] Preferably, when stirring in a UVA environment, the UV wavelength is 400-405nm and the pH value is 5-7.

[0035] Through the above technical solution, when the above pH value and ultraviolet wavelength are used, epoxy quaternary ammonium salt can be introduced onto chitin more simply and stably, and Aspergillus niger and Aspergillus nidus in the Aspergillus fermentation broth can be more stable, indirectly improving the flocculation effect of the flocculant.

[0036] Thirdly, this application provides a process for dewatering and solidifying mud and sludge, employing the following technical solution:

[0037] A process for dewatering and solidifying mud and sludge includes the following steps:

[0038] Extraction: The sludge is extracted into the mud pit and then mixed and stirred evenly;

[0039] Sedimentation: Add the above flocculant to the sludge slurry, then stir and mix and let it settle to obtain stratified sludge flocculents and supernatant liquid;

[0040] Dewatering: The mud flocs are transferred to a geotextile for dewatering and filtration to obtain solidified mud cakes, which are then removed.

[0041] Through the above technical solution, when the flocculant is added to the sludge, over time, Aspergillus niger and Aspergillus nidus gradually multiply in large quantities using PLA-g-CS as a carrier. The hyphae of Aspergillus niger begin to adsorb small particulate matter, and the metabolites secreted by Aspergillus niger into the extracellular space gradually exert a flocculation effect. The chitin deacetase formed by Aspergillus nidus promotes the binding of chitin to PLA-g-CS, while chitin exerts a flocculation effect. Most of the sludge gradually forms sludge flocs with PLA-g-CS as the center, thereby completing solid-liquid separation.

[0042] In summary, this application has the following beneficial effects:

[0043] 1. PLA-g-CS serves as a growth carrier for Aspergillus niger and Aspergillus nidus in the Aspergillus fermentation broth. Besides its excellent flocculation properties, the Aspergillus nidus in the fermentation broth can also form chitin deacetylase under the induction of soluble chitosan. This chitin deacetylase deacetylates some chitin to form chitosan, which then reacts with the epoxy groups in the quaternary ammonium salt, introducing quaternary ammonium salt groups at the chitosan sites on PLA-g-CS. This results in a stronger flocculation effect for the flocculant. Furthermore, this flocculant exhibits good biodegradability, reducing environmental pollution.

[0044] 2. Chitosan, PLA-g-CS and Aspergillus fermentation broth are all non-toxic and harmless. Due to the presence of these three substances, the amount of epoxy quaternary ammonium salt added is relatively small, which enables the flocculant to have a large addition range, effectively reducing the precision of flocculant dosage and thus reducing the possibility of secondary pollution caused by excessive epoxy quaternary ammonium salt.

[0045] 3. Glycidyltrimethylammonium chloride has short branches, while 2,3-glycidyldodecyldimethylammonium chloride has long branches. This results in PLA-g-CS having a mixed structure of cationic, long-branched, and short-branched chains. Consequently, when dewatering sludge, the flocculant can form large and dense sludge flocs, meaning the flocculant can have a better flocculation effect. Detailed Implementation

[0046] Raw materials: Chitosan (CAS: 1398-61-4); Lactose (CAS: 13076-17-0); Chitosan (CAS: 9012-76-4); Epioxypropyltrimethylammonium chloride (CAS: 3033-77-0); Epichlorohydrin (CAS: 106-89-8); Diethyl ether (CAS: 60-29-7); Dodecyl dimethylamine (CAS: 112-18-5); Aspergillus niger spore powder (Ruiyuan 5 billion); Aspergillus niger spore powder (Shanghai Yansheng); LB culture medium (Kaiheng Bio); Polyacrylamide flocculant (Shouxin Environmental Protection CAS: 9003-05-8);

[0047] Different types of calcium salts can be selected. This application specifically uses calcium silicate with CAS number 1344-95-2 as an example for experiments. Calcium silicate also contains silicate ions, which have a strong adsorption and bridging ability for colloidal particles in sludge. Calcium salts, through hydrolysis, yield positively charged calcium hydroxyl ions. When the two are combined, they can exert both charge neutralization and adsorption bridging abilities, further improving the flocculation effect of the flocculant.

[0048] 2,3-Epoxypropyldodecyldimethylammonium chloride: 40 kg of epichlorohydrin was added to 30 kg of diethyl ether, followed by the dropwise addition of 27 kg of dodecyldimethylamine. The mixture was then reacted at 20 °C for 10 h. Finally, the mixture was filtered, washed, and dried to obtain 2,3-epoxypropyldodecyldimethylammonium chloride.

[0049] Aspergillus niger fermentation broth: 0.1g of Aspergillus niger spore powder was restored and cultured, then inoculated into 100ml of LB medium and cultured in a shaker at 28℃ for 72h to obtain Aspergillus niger fermentation broth.

[0050] Aspergillus nidulans fermentation broth: 0.6g of Aspergillus nidulans spore powder was restored and cultured, then inoculated into 100ml of LB medium and cultured in a shaker at 28℃ for 72h to obtain Aspergillus nidulans fermentation broth.

[0051] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0052] Example

[0053] Example 1

[0054] I. Preparation of PLA-g-CS

[0055] 1. Preparation of carboxyl-terminated polylactic acid: Weigh 12.5 kg of lactide, 0.25 kg of water, and 0.1 kg of zinc lactate and add them to a polymerization tube. Under nitrogen protection, heat at 140 °C to melt the reactants. When the liquid in the polymerization tube turns into a milky white solid, freeze it with liquid nitrogen and then dry the milky white solid in a vacuum drying oven to obtain carboxyl-terminated polylactic acid.

[0056] 2. Preparation of PLA-g-CS: 10 kg of carboxyl-terminated polylactic acid was dissolved in 60 L of dimethyl sulfoxide, and 500 g of 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride and 500 g of N-hydroxysuccinimide were added. The mixture was stirred at 30 °C for 1 h. 0.7 kg of soluble chitosan was added to 5 L of dimethyl sulfoxide to prepare a chitosan solution. The chitosan solution was added to the above solution and reacted for 4 h. Impurities were removed by dialyzing, precipitate was removed by filtration, and PLA-g-CS was obtained by freeze drying.

[0057] II. Preparation of Flocculants

[0058] First, 18 kg of chitin, 5 kg of Aspergillus fermentation broth, and 2.5 kg of PLA-g-CS were mixed evenly at a stirring speed of 50 r / min for 6 h. Then, 11 kg of epoxy quaternary ammonium salt and 10 kg of calcium silicate were added to obtain a reaction solution. The reaction solution was then subjected to a 403 nm long-wave ultraviolet light environment at a reaction temperature of 38 °C for 9 h. The pH value of the reaction was adjusted to 6 using hydrochloric acid and sodium hydroxide.

[0059] The Aspergillus fermentation broth is a mixture of Aspergillus niger and Aspergillus nidus fermentation broths, with a mass ratio of 4:1. The epoxy quaternary ammonium salt is a mixture of 2,3-epoxypropyldodecyl dimethylammonium chloride and epioxypropyltrimethylammonium chloride, with a mass ratio of 2:1.

[0060] A process for dewatering and solidifying mud and sludge includes the following steps:

[0061] Extraction: Extract 100L of sludge into the mud tank, and then mix and stir evenly;

[0062] Sedimentation: Add 5 kg of flocculant to the sludge slurry, then stir at a stirring speed of 100 r / min for 2 h, and then settle to obtain stratified sludge flocculents and supernatant.

[0063] Dewatering: The mud flocs are transferred to a geotextile for dewatering and filtration to obtain solidified mud cakes, which are then removed.

[0064] Example 2-3

[0065] Examples 2-3 are based on the preparation method of Example 1, but the amount of each component of the flocculant is adjusted, as shown in Table 1.

[0066] Comparative Examples 1-2

[0067] Comparative Examples 1-2 were prepared using the same method as in Example 1, but with adjustments made to the amount of each component of the flocculant added. The specific adjustments are shown in Table 1.

[0068] Comparative Example 3

[0069] Comparative Example 3 is based on the preparation method of Example 1, but the flocculant is replaced with polyacrylamide flocculant.

[0070] Table 1. Dosage (kg) of each component added in Examples 1-3 and Comparative Examples 1-2

[0071] Item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Chitin 18 16 20 18 18 Fermentation broth of Aspergillus 5 4 6 5 5 PLA-g-CS 2.5 2 3 3.5 1.5 Epoxy-based quaternary ammonium salt 11 12 10 11 11 Calcium silicate 10 8 12 10 10

[0072] Performance testing

[0073] Flocculation effect and flocculation time test

[0074] Mix 100ml of sludge slurry until uniform, then add 100ml of sludge slurry to a 250ml graduated cylinder. Each group consists of 3 graduated cylinders of sludge slurry. Then, add 5g of flocculant provided in the embodiments and comparative examples of this application to each group of graduated cylinders and let stand for 30 minutes to obtain sludge flocculents and supernatant.

[0075] The mud flocs were then filtered, dried, and weighed. Finally, the average value of the data measured by three graduated cylinders in each group was taken as the flocculation effect parameter and recorded. The results are shown in Table 2.

[0076] Record the time when the mud flocs reach the 20mL mark in the test tube. Finally, take the average of the data measured by the three graduated cylinders in each group as the flocculation time parameter and record it. The results are shown in Table 2.

[0077] Table 2 Performance test results of Examples 1-3 and Comparative Examples 1-3

[0078]

[0079] Referring to Table 2, comparing Examples 1-3 and Comparative Examples 1-3, it can be seen that compared with Example 1, the flocculation effect parameters of Examples 2-3 decreased and the flocculation time increased. The flocculation effect parameters of Comparative Examples 1-2 decreased significantly and the flocculation time increased significantly. This shows that the components of the flocculant have a better flocculation effect under the ratio of Example 1.

[0080] Furthermore, the flocculation effect of Examples 1-3 significantly exceeded that of Comparative Example 3, and the flocculation time of Examples 1-3 was significantly shorter than that of Comparative Example 3, indicating that the flocculation capacity of the flocculants prepared in Examples 1-3 all exceeded that of the polyacrylamide flocculant.

[0081] Examples 4-5

[0082] Examples 4-5 are based on the preparation method of Example 1, but the mass ratio of Aspergillus niger fermentation broth to Aspergillus nidus fermentation broth is adjusted, as shown in Table 3.

[0083] Comparative Example 4-5

[0084] Comparative Examples 4-5 were prepared using the same method as in Example 1, but with adjustments made to the mass ratio of Aspergillus niger fermentation broth to Aspergillus nidus fermentation broth. The specific adjustments are shown in Table 3.

[0085] The flocculants prepared in Examples 4-5 and Comparative Examples 4-5 were subjected to the above performance tests, and the test results are shown in Table 3.

[0086] Table 3. Data on the addition amount and performance test of Aspergillus niger fermentation broth and Aspergillus nidus fermentation broth in Examples 1, 4-5 and Comparative Examples 4-5.

[0087]

[0088] Referring to Table 3, comparing Examples 1, 4-5, and 4-5, it can be seen that as the content of Aspergillus niger fermentation broth increases, the flocculation effect and flocculation time of the flocculant first increase and then decrease. This may be because as the content of Aspergillus niger fermentation broth increases, the amount of substances secreted by Aspergillus niger into the extracellular space increases, thereby continuously improving the flocculation capacity of the flocculant. However, if the content of Aspergillus niger fermentation broth is too high, the substances secreted by Aspergillus niger into the extracellular space already have sufficient flocculation effect, while the content of Aspergillus nidulans is low, which reduces the production of chitin deacetylase and reduces the effect of chitin embedding into PLA-g-CS, thereby reducing the flocculation capacity of the flocculant.

[0089] Examples 6-8

[0090] Examples 6-8 are based on the preparation method of Example 1, but the mass ratio of carboxyl-terminated polylactic acid to chitosan in the chitosan solution is adjusted, as shown in Table 4.

[0091] Comparative Examples 6-7

[0092] Comparative Examples 6-7 were prepared using the same method as in Example 1, but with adjustments made to the mass ratio of carboxyl-terminated polylactic acid to chitosan in the chitosan solution. The specific adjustments are shown in Table 4.

[0093] The flocculants prepared in Examples 6-8 and Comparative Examples 6-7 were subjected to the above performance tests, and the test results are shown in Table 4.

[0094] Table 4. Data on the addition amount and performance test of carboxyl-terminated polylactic acid and chitosan in Examples 1, 6-8, and Comparative Examples 6-7.

[0095]

[0096] Referring to Table 4, comparing Examples 1, 6-8, and 6-7, it can be seen that as the chitosan content increases, the flocculation effect and flocculation time of the flocculant first increase and then decrease. This may be because as the chitosan content increases, chitosan is continuously grafted onto the terminal carboxyl polylactic acid, continuously improving the flocculation capacity of the flocculant. However, if the chitosan content is too high, the self-polymerization reaction of chitosan dominates, reducing the grafting rate of the terminal carboxyl polylactic acid, thereby reducing the flocculation capacity of the flocculant.

[0097] Examples 9-10

[0098] Examples 9-10 are based on the preparation method of Example 1, but the mass ratio of 2,3-epoxypropyldodecyldimethylammonium chloride (referred to as "2,3-epoxypropylammonium chloride" in the table) and epioxypropyltrimethylammonium chloride (referred to as "epoxypropylammonium chloride" in the table) was adjusted, as shown in Table 5.

[0099] Comparative Examples 8-9

[0100] Comparative Examples 8-9 were prepared using the same method as in Example 1, but with adjustments made to the mass ratio of 2,3-epoxypropyldodecyldimethylammonium chloride (referred to as "2,3-epoxypropylammonium chloride" in the table) and epioxypropyltrimethylammonium chloride (referred to as "epoxypropylammonium chloride" in the table). The specific adjustments are shown in Table 5.

[0101] The flocculants prepared in Examples 9-10 and Comparative Examples 8-9 were subjected to the above performance tests, and the test results are shown in Table 5.

[0102] Table 5. Data on the addition amount and performance test results of 2,3-cycloammonium chloride and cycloammonium chloride in Examples 1, 9-10, and Comparative Examples 8-9.

[0103]

[0104]

[0105] Referring to Table 5, comparing Examples 1, 9-10 and Comparative Examples 8-9, it can be seen that as the content of 2,3-epoxypropyldodecyldimethylammonium chloride increases, the flocculation effect and flocculation time of the flocculant first increase and then decrease. This may be because as the chitosan content increases, the mixed structure of cationic, long-branched, and short-branched structures on the surface of chitin is first continuously improved and then reaches a critical point. Then, the mixed structure is dominated by short-branched structures, which makes the flocculation ability of the flocculant continuously increase and then decrease.

[0106] Examples 11-12

[0107] Examples 11-12 are based on the preparation method of Example 1, but the reaction temperature and reaction time during flocculant preparation are adjusted, as shown in Table 6.

[0108] Comparative Examples 10-11

[0109] Comparative Examples 10-11 were prepared based on the method in Example 1, but the reaction temperature and reaction time during flocculant preparation were adjusted, as shown in Table 6.

[0110] The flocculants prepared in Examples 11-12 and Comparative Examples 10-11 were subjected to the above performance tests, and the test results are shown in Table 7.

[0111] Table 6. Reaction conditions for Examples 1, 11-12 and Comparative Examples 10-11

[0112] Item Reaction temperature / °C Reaction time / h Example 1 38 9 Example 11 35 10 Example 12 40 8 Comparative Example 10 32 11 Comparative Example 11 45 7

[0113] Table 7 Performance test data for Examples 1, 11-12 and Comparative Examples 10-11

[0114]

[0115]

[0116] Referring to Table 7, a comparison of Examples 1, 11-12 and Comparative Examples 10-11 shows that, compared to Example 1, the flocculation effect parameters of Examples 11-12 decreased and the flocculation time increased, while the flocculation effect parameters of Comparative Examples 10-11 decreased significantly and the flocculation time increased significantly. This indicates that the flocculant components have a better flocculation effect when formulated in the proportions of Example 1.

[0117] Examples 13-16

[0118] Examples 13-14 are based on the preparation method of Example 1, but the ultraviolet wavelength during flocculant preparation is adjusted, as shown in Table 8.

[0119] Examples 15-16 are based on the preparation method of Example 1, but the pH during flocculant preparation is adjusted, as shown in Table 8.

[0120] Comparative Examples 12-15

[0121] Comparative Examples 12-13 were prepared using the same method as in Example 1, but with adjustments made to the ultraviolet wavelength used in the preparation of the flocculant. The specific adjustments are shown in Table 8.

[0122] Comparative Examples 14-15 were prepared using the same method as in Example 1, but with adjustments made to the pH during flocculant preparation. The specific adjustments are shown in Table 8.

[0123] The flocculants prepared in Examples 13-16 and Comparative Examples 12-15 were subjected to the above performance tests, and the test results are shown in Table 9.

[0124] Table 8. Reaction conditions for Examples 1, 13-16 and Comparative Examples 12-15

[0125]

[0126]

[0127] Table 9 Performance test data for Examples 1, 13-16 and Comparative Examples 12-15

[0128]

[0129] Referring to Table 9, comparing Examples 1, 13-16 and Comparative Examples 12-15, it can be seen that, compared with Example 1, the flocculation effect parameters of Examples 13-16 decreased and the flocculation time increased, while the flocculation effect parameters of Comparative Examples 12-15 decreased significantly and the flocculation time increased significantly. This indicates that the flocculant components have a better flocculation effect when formulated in the proportions of Example 1.

[0130] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A flocculant, characterized in that, The raw materials include the following parts by weight: 16-20 parts chitin, 4-6 parts Aspergillus fermentation broth, 2-3 parts PLA-g-CS, 10-12 parts epoxy quaternary ammonium salt and 8-12 parts calcium salt, wherein the Aspergillus fermentation broth contains Aspergillus niger and Aspergillus nidus, and the PLA-g-CS is prepared by grafting chitosan with carboxyl-terminated polylactic acid; The Aspergillus fermentation broth is a mixture of Aspergillus niger fermentation broth and Aspergillus niger fermentation broth, and the mass ratio of the Aspergillus niger fermentation broth to the Aspergillus niger fermentation broth is (3-5):1; The preparation method of PLA-g-CS includes the following steps: Preparation of carboxyl-terminated polylactic acid: Weigh lactide, water and zinc lactate, mix them evenly, and heat under nitrogen protection to melt the reactants to obtain carboxyl-terminated polylactic acid; Preparation of PLA-g-CS: The carboxyl-terminated polylactic acid was dissolved in dimethyl sulfoxide, 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride and N-hydroxysuccinimide were added, the mixture was stirred at a constant temperature, chitosan solution was added to react, impurities were removed by dialysis, precipitate was removed by filtration, and PLA-g-CS was obtained by freeze drying. The mass ratio of the terminal carboxyl polylactic acid to the chitosan in the chitosan solution is 10:(0.4-0.8).

2. The flocculant according to claim 1, characterized in that: The epoxy quaternary ammonium salt is a mixture of 2,3-epoxypropyldodecyldimethylammonium chloride and epioxypropyltrimethylammonium chloride.

3. The flocculant according to claim 2, characterized in that: The mass ratio of 2,3-epoxypropyldodecyldimethylammonium chloride to epioxypropyltrimethylammonium chloride is (1-3):

1.

4. A method for preparing a flocculant, used to prepare the flocculant as described in any one of claims 1-3, characterized in that: First, chitin, Aspergillus fermentation broth, and PLA-g-CS were added to a solvent and stirred thoroughly. Then, epoxy quaternary ammonium salt and calcium salt were added, and the mixture was stirred under UVA ultraviolet light to obtain the flocculant.

5. The method for preparing the flocculant according to claim 4, characterized in that: When stirring under UVA ultraviolet light, the reaction temperature is 35-40℃ and the reaction time is 8-10h.

6. The method for preparing the flocculant according to claim 4, characterized in that: When stirring in a UVA environment with a wavelength of 400-405nm and a pH value of 5-7.

7. A process for dewatering and solidifying mud and sludge, characterized in that, Includes the following steps: Extraction: The sludge is extracted into the mud pit and then mixed and stirred evenly; Sedimentation: The flocculant according to any one of claims 1-3 is added to the sludge slurry, then stirred and mixed and precipitated to obtain stratified sludge flocs and supernatant; Dewatering: The mud flocs are transferred to a geotextile for dewatering and filtration to obtain solidified mud cakes, which are then removed.

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