Preparation method and application of degradable flocculant for sludge

Abstract

The invention discloses a preparation method and application of a degradable flocculating agent for sludge, and belongs to the technical field of sludge treatment.The preparation method of the flocculating agent comprises the following steps that acrylamide, chlorin grafted itaconic acid hyperbranched polyester, a polyaspartic acid derivative and a cationic monomer are added into a solvent, an initiator is added in the nitrogen atmosphere, stirring is carried out, and the flocculating agent is obtained. And after the reaction is finished, cooling to room temperature, precipitating the reaction product by using absolute ethyl alcohol, filtering the precipitated product, washing by using absolute ethyl alcohol, and drying to obtain the degradable flocculating agent for sludge. The chlorin grafted itaconic acid hyperbranched polyester and the polyaspartic acid derivative are introduced to optimize the flocculation performance of traditional cationic polyacrylamide, sludge can be deeply dewatered, the turbidity and COD content of dewatered filtrate are low, and good biodegradability is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment, and in particular relates to a preparation method and application of a degradable flocculant for sludge. Background Art

[0002] With the rapid development of economy and the rapid improvement of people's living standards, the amount of water used in cities is increasing, and the amount of sludge produced and discharged is also increasing. The water content of sludge is usually high (more than 80%), and it is accompanied by the presence of metal ions and organic pollution. The odor and organic volatiles it emits not only pollute the air, but also pollute the groundwater, and cause local sudden excessive heavy metal ions, which are absorbed by crops and directly endanger human health.

[0003] In the prior art, mechanical methods or flocculants are usually used to dehydrate sludge, but the separated water produced after sludge dehydration contains various organic matter, which not only makes the water turbid, but also has a high content of suspended organic matter, which will pollute the environment. The use of traditional polyacrylamide flocculants often fails to achieve good flocculation efficacy. After flocculation, the turbidity and COD of the filtrate still exceed the standard and need to be treated before discharge. In addition, the existing cationic polyacrylamide flocculants are difficult to biodegrade and are prone to secondary pollution. Summary of the invention

[0004] The purpose of the present invention is to provide a preparation method and application of a degradable flocculant for sludge, so as to solve the problem that the polyacrylamide flocculant in the prior art is non-degradable.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a degradable flocculant for sludge comprises the following steps:

[0007] S1. Prepare the following raw materials in parts by weight: 100 parts of acrylamide, 3-5 parts of chlorin-grafted itaconic acid hyperbranched polyester, 1-10 parts of polyaspartic acid derivative, 10-20 parts of cationic monomer, 0.08-0.1 parts of initiator, and 500-800 parts of solvent;

[0008] S2. Add acrylamide, dihydrochlorin grafted itaconic acid hyperbranched polyester, polyaspartic acid derivative and cationic monomer into a solvent, add an initiator in a nitrogen atmosphere, and carry out copolymerization. After the reaction is completed, cool to room temperature, precipitate the reaction product with anhydrous ethanol, filter the precipitated product, wash with anhydrous ethanol and then dry to obtain a degradable flocculant for sludge.

[0009] Furthermore, the copolymerization reaction temperature is 50-65°C, and the copolymerization time is 2-5h.

[0010] Further, the chlorin-grafted itaconic acid hyperbranched polyester is prepared by the following steps:

[0011] Add itaconic acid hyperbranched polyester and DMSO to the reaction bottle, stir evenly, then add dihydrochlorin E6, DCC, NHS and DMAP, seal, stir and heat to 50°C, react for 72h, then precipitate with ether, and dry the precipitate at 50°C to constant weight;

[0012] The dosage ratio of itaconic acid hyperbranched polyester, DMSO, dihydrochlorin E6, DCC, NHS and DMAP is 0.5-0.8g:10-20mL:0.2g:0.41g:0.23g:0.24g, DMSO is dimethyl sulfoxide, DCC is N,N'-dicyclohexylcarbodiimide, NHS is N-hydroxysuccinimide, and DMAP is 4-dimethylaminopyridine.

[0013] Further, itaconic acid hyperbranched polyester is prepared by the following steps:

[0014] Mix itaconic acid, trimethylolpropane, p-toluenesulfonic acid and DMF, stir and react at 90-100°C for 8h under nitrogen protection, and remove DMF by vacuum distillation;

[0015] The molar ratio of itaconic acid to trimethylolpropane is 1:1, and the amount of p-toluenesulfonic acid used is 0.5-1% of the total mass of itaconic acid and trimethylolpropane.

[0016] Further, the polyaspartic acid derivative is prepared by the following steps:

[0017] Mix polysuccinimide, dopamine hydrochloride, allylthiourea, sodium hydroxide and deionized water evenly, heat to 60°C and stir to react for 24 hours. After the reaction is completed, cool to room temperature, add the reaction product dropwise into acetone, and then vacuum dry at 80°C to constant weight;

[0018] The dosage ratio of polysuccinimide, dopamine hydrochloride, allylthiourea, sodium hydroxide, deionized water and acetone is 0.98g:0.775g:0.775g:0.32g:5-10mL, the molecular weight of polysuccinimide is 3000-7000, dopamine hydrochloride and allylthiourea are used as modifiers, and a polyaspartic acid derivative containing a thiourea structure, catechol and allyl is obtained through a ring-opening reaction of polysuccinimide with dopamine and allylthiourea.

[0019] Further, the cationic monomer is at least one of methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride and (3-acrylamidopropyl) trimethyl ammonium chloride.

[0020] Furthermore, the initiator is at least one of potassium persulfate, ammonium persulfate and azobisisobutyronitrile.

[0021] Furthermore, the solvent is any one of distilled water and ethanol aqueous solution, and the volume fraction of the ethanol aqueous solution is 20-25%.

[0022] The invention discloses an application of the degradable flocculant obtained by the preparation method described above in dewatering of municipal sludge.

[0023] Beneficial effects of the present invention:

[0024] The invention provides a preparation method and application of a degradable flocculant for sludge. The flocculation performance of traditional cationic polyacrylamide is optimized by introducing dihydrochlorin grafted itaconic acid hyperbranched polyester and polyaspartic acid derivatives, and the sludge can be deeply dehydrated. The filtrate after dehydration has low turbidity and COD content and good biodegradability.

[0025] The positively charged cations in the flocculant of the present invention are electrically neutralized with the negatively charged sludge, so that the sludge is mixed and aggregated. The polyaspartic acid derivative forms a physical entanglement network structure through long molecular chains to play a bridging net capture role, and the thiourea structure and catechol group of the molecular chain have better adsorption effects on organic pollutants and heavy metal ions. The dihydrochlorin grafted itaconic acid hyperbranched polyester contains more oxygen-containing groups and benzene ring structures, and can adsorb pollutants through hydrogen bonding and π-π interactions. It also contains a large number of holes inside, which can wrap and adsorb a large number of pollutants. More prominently, the dihydrochlorin structure in the dihydrochlorin grafted itaconic acid hyperbranched polyester can produce active oxygen species or other oxidizing substances under visible light irradiation, and these substances can participate in the oxidation process of organic matter in the sludge, thereby helping to reduce COD. In summary, the filtrate water quality after the flocculant of the present invention treats the sludge is better.

[0026] The polyaspartic acid derivatives in the present invention can participate in polymerization reactions, belong to polyamino acid substances, have good biodegradability, and are specifically prepared by using dopamine hydrochloride and allylthiourea as composite modifiers. Compared with the single use of dopamine hydrochloride or allylthiourea as a modifier, the composite modification method of the present invention significantly optimizes the polymerization process, achieving the ideal effect of both participating in the polymerization reaction and effectively avoiding excessive polymerization. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Preparation Example 1

[0029] The preparation of dihydrochlorin grafted itaconic acid hyperbranched polyester is as follows:

[0030] Add 5 g of itaconic acid hyperbranched polyester and 100 mL of DMSO to the reaction bottle, stir evenly, then add 2 g of dihydrochlorin E6, 4.1 g of DCC, 2.3 g of NHS and 2.4 g of DMAP, seal, stir and heat to 50°C, react for 72 h, then precipitate with ether, and dry the precipitate at 50°C to constant weight.

[0031] Itaconic acid hyperbranched polyester is prepared by the following steps:

[0032] Mix 0.1 mol itaconic acid, 0.1 mol trimethylolpropane, 0.13 g p-toluenesulfonic acid and 180 mL DMF, stir and react at 90°C for 8 h under nitrogen protection, and remove DMF by distillation under reduced pressure.

[0033] Preparation Example 2

[0034] The preparation of dihydrochlorin grafted itaconic acid hyperbranched polyester is as follows:

[0035] Add 8 g of itaconic acid hyperbranched polyester and 200 mL of DMSO to the reaction bottle, stir evenly, then add 2 g of dihydrochlorin E6, 4.1 g of DCC, 2.3 g of NHS and 2.4 g of DMAP, seal, stir and heat to 50°C, react for 72 hours, then precipitate with ether, and dry the precipitate at 50°C to constant weight.

[0036] Itaconic acid hyperbranched polyester is prepared by the following steps:

[0037] Mix 0.1 mol itaconic acid, 0.1 mol trimethylolpropane, 0.26 g p-toluenesulfonic acid and 220 mL DMF, stir and react at 100 °C for 8 h under nitrogen protection, and remove DMF by distillation under reduced pressure.

[0038] Example 1

[0039] A method for preparing a degradable flocculant for sludge comprises the following steps:

[0040] S1. Prepare the following raw materials in parts by weight: 100 parts of acrylamide, 3 parts of the chlorin-grafted itaconic acid hyperbranched polyester of Preparation Example 1, 1 part of a polyaspartic acid derivative, 10 parts of methacryloyloxyethyltrimethylammonium chloride, 0.08 parts of potassium persulfate, and 500 parts of distilled water;

[0041] S2. Add acrylamide, dihydrochlorin grafted itaconic acid hyperbranched polyester, polyaspartic acid derivatives and methacryloyloxyethyltrimethylammonium chloride into distilled water, add potassium persulfate in a nitrogen atmosphere, react at 50°C for 5 hours, and after the reaction is completed, cool to room temperature. The reaction product is precipitated with anhydrous ethanol, the precipitated product is filtered, washed with anhydrous ethanol and then dried to obtain a degradable flocculant for sludge.

[0042] The polyaspartic acid derivative is prepared by the following steps:

[0043] 9.8 g of polysuccinimide, 7.75 g of dopamine hydrochloride, 7.75 g of allyl thiourea, 3.2 g of sodium hydroxide and 50 mL of deionized water were mixed evenly, heated to 60 ° C and stirred for reaction for 24 hours. After the reaction was completed, it was cooled to room temperature, and the reaction product was added dropwise to acetone, and then vacuum dried at 80 ° C to constant weight. The molecular weight of polysuccinimide is 3000.

[0044] Example 2

[0045] A method for preparing a degradable flocculant for sludge comprises the following steps:

[0046] S1. Prepare the following raw materials in parts by weight: 100 parts of acrylamide, 4 parts of the chlorin-grafted itaconic acid hyperbranched polyester of Preparation Example 2, 5 parts of a polyaspartic acid derivative, 15 parts of acryloyloxyethyltrimethylammonium chloride, 0.08 parts of ammonium persulfate, and 700 parts of a 20% by volume ethanol aqueous solution;

[0047] S2. Add acrylamide, dihydrochlorin grafted itaconic acid hyperbranched polyester, polyaspartic acid derivatives and acryloyloxyethyltrimethylammonium chloride into a 20% by volume aqueous ethanol solution, add ammonium persulfate in a nitrogen atmosphere, react at 60°C for 3 hours, and after the reaction is completed, cool to room temperature. The reaction product is precipitated with anhydrous ethanol, the precipitated product is filtered, washed with anhydrous ethanol and then dried to obtain a degradable flocculant for sludge.

[0048] The polyaspartic acid derivative is prepared by the following steps:

[0049] 9.8 g of polysuccinimide, 7.75 g of dopamine hydrochloride, 7.75 g of allyl thiourea, 3.2 g of sodium hydroxide and 100 mL of deionized water were mixed evenly, heated to 60 ° C and stirred for reaction for 24 hours. After the reaction was completed, it was cooled to room temperature, and the reaction product was added dropwise to acetone, and then vacuum dried at 80 ° C to constant weight. The molecular weight of polysuccinimide is 5000.

[0050] Example 3

[0051] A method for preparing a degradable flocculant for sludge comprises the following steps:

[0052] S1. Prepare the following raw materials in parts by weight: 100 parts of acrylamide, 5 parts of the chlorin-grafted itaconic acid hyperbranched polyester of Preparation Example 2, 10 parts of a polyaspartic acid derivative, 20 parts of (3-acrylamidopropyl)trimethylammonium chloride, 0.1 parts of azobisisobutyronitrile, and 800 parts of a 25% by volume ethanol aqueous solution;

[0053] S2. Add acrylamide, dihydrochlorin grafted itaconic acid hyperbranched polyester, polyaspartic acid derivatives and (3-acrylamidepropyl)trimethylammonium chloride into 25% by volume ethanol aqueous solution, add azobisisobutyronitrile in a nitrogen atmosphere, react at 65°C for 2 hours, cool to room temperature after the reaction, precipitate the reaction product with anhydrous ethanol, filter the precipitated product, wash with anhydrous ethanol and then dry to obtain a degradable flocculant for sludge.

[0054] The polyaspartic acid derivative is prepared by the following steps:

[0055] 9.8 g of polysuccinimide, 7.75 g of dopamine hydrochloride, 7.75 g of allyl thiourea, 3.2 g of sodium hydroxide and 100 mL of deionized water were mixed evenly, heated to 60 ° C and stirred for reaction for 24 hours. After the reaction was completed, it was cooled to room temperature, and the reaction product was added dropwise to acetone, and then vacuum dried at 80 ° C to constant weight. The molecular weight of polysuccinimide is 7000.

[0056] Comparative Example 1

[0057] A method for preparing a degradable flocculant for sludge, compared with Example 1, the only difference is that the dihydrochlorin grafted itaconic acid hyperbranched polyester in Example 1 is replaced with an equal weight portion of itaconic acid hyperbranched polyester, and the preparation process of the itaconic acid hyperbranched polyester is the same as that of Preparation Example 1.

[0058] Comparative Example 2

[0059] A method for preparing a degradable flocculant for sludge, compared with Example 1, the only difference is that the dopamine hydrochloride in Example 1 is replaced by allyl thiourea of ​​the same mass.

[0060] Comparative Example 3

[0061] A method for preparing a degradable flocculant for sludge, compared with Example 1, the only difference is that the allyl thiourea in Example 1 is replaced by dopamine hydrochloride of the same mass.

[0062] Comparative Example 4

[0063] A method for preparing a degradable flocculant for sludge, compared with Example 1, the only difference is that the dihydrochlorin grafted itaconic acid hyperbranched polyester in Example 1 is removed.

[0064] Comparative Example 5

[0065] A method for preparing a degradable flocculant for sludge, compared with Example 1, the only difference is that the polyaspartic acid derivative in Example 1 is removed.

[0066] The flocculants obtained from Examples 1 to 3 and Comparative Examples 1 to 5 were tested, and the testing process was as follows:

[0067] Take 600mL of sludge from a municipal sewage treatment plant concentration tank as a sludge sample with a water content of 98.5% to measure its turbidity, chemical oxygen demand (COD), Pb 2+ Content, turbidity was tested by turbidity meter (equipment model: HACH-2100Q), COD laboratory was determined according to GB11914-89, Pb 2+ The content was obtained by Shimadzu AA-6200 atomic spectrophotometer analysis and detection, and the data were recorded. Each group of flocculants was added according to the dosage ratio of 1.5 mg: 600 mL, stirred for 30 min under visible light irradiation, and allowed to stand for 2 h. The supernatant was taken to measure the turbidity, COD, and lead ion content, and the turbidity removal rate (%), COD removal rate (%), Pb 2+ Removal rate (%), the results are shown in Table 1:

[0068] Table 1

[0069]

[0070]

[0071] It can be seen from Table 1 that after the same sludge was treated with flocculants in Example 1, Example 2, and Example 3, the turbidity removal rate, COD removal rate, and Pb 2+ The removal rates are all greater than those of comparative examples 1-5, indicating that the synergistic effect of the flocculants provided by the present invention enables the flocculants to have better decontamination performance.

[0072] The flocculants prepared in Examples 1-3 and Comparative Examples 1-5 were added to soil extracts under the same conditions, respectively, and degraded at 37°C for 60 days. Samples were taken at 30 days and 60 days, respectively, and the degradation rates were calculated. The results are shown in Table 2:

[0073] Table 2

[0074]

[0075] It can be seen from Table 2 that the flocculants prepared in Examples 1-3 have good biodegradability, which is obviously better than that in Comparative Examples 4 and 5, indicating that the present invention effectively provides the biodegradability of the polyacrylamide flocculant by introducing dihydrochlorin grafted itaconic acid hyperbranched polyester and polyaspartic acid derivatives.

[0076] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0077] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a degradable flocculant for sludge, characterized in that: The following steps are involved: Acrylamide, dihydrochlorin grafted itaconic acid hyperbranched polyester, polyaspartic acid derivative and cationic monomer are added to a solvent, and an initiator is added in a nitrogen atmosphere to carry out a copolymerization reaction. After the reaction is completed, it is cooled to room temperature, and the reaction product is precipitated with anhydrous ethanol. The precipitated product is filtered, washed with anhydrous ethanol and then dried to obtain a degradable flocculant for sludge.

2. The method for preparing a degradable flocculant for sludge according to claim 1, characterized in that: The degradable flocculant for sludge comprises the following raw materials in parts by weight: 100 parts of acrylamide, 3-5 parts of dihydrochlorin grafted itaconic acid hyperbranched polyester, 1-10 parts of polyaspartic acid derivative, 10-20 parts of cationic monomer, 0.08-0.1 parts of initiator and 500-800 parts of solvent.

3. The method for preparing a degradable flocculant for sludge according to claim 1, characterized in that: The copolymerization reaction temperature is 50-65°C and the copolymerization time is 2-5h.

4. The method for preparing a degradable flocculant for sludge according to claim 1, characterized in that: Chlorin grafted itaconic acid hyperbranched polyester is prepared by the following steps: Add itaconic acid hyperbranched polyester and DMSO to the reaction bottle, stir evenly, then add dihydrochlorin E6, DCC, NHS and DMAP, seal, stir and heat to 50°C, react for 72h, then precipitate with ether, and dry the precipitate at 50°C to constant weight; The usage ratio of itaconic acid hyperbranched polyester, DMSO, dihydrochlorin E6, DCC, NHS and DMAP is 0.5-0.8 g: 10-20 mL: 0.2 g: 0.41 g: 0.23 g: 0.24 g.

5. The method for preparing a degradable flocculant for sludge according to claim 1, characterized in that: The polyaspartic acid derivative is prepared by the following steps: Mix polysuccinimide, dopamine hydrochloride, allylthiourea, sodium hydroxide and deionized water evenly, heat to 60°C and stir to react for 24 hours. After the reaction is completed, cool to room temperature, add the reaction product dropwise into acetone, and then vacuum dry at 80°C to constant weight.

6. The method for preparing a degradable flocculant for sludge according to claim 5, characterized in that: The dosage ratio of polysuccinimide, dopamine hydrochloride, allylthiourea, sodium hydroxide, deionized water and acetone is 0.98 g: 0.775 g: 0.775 g: 0.32 g: 5-10 mL.

7. The method for preparing a degradable flocculant for sludge according to claim 1, characterized in that: The cationic monomer is at least one of methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride and (3-acrylamidopropyl) trimethyl ammonium chloride.

8. The method for preparing a degradable flocculant for sludge according to claim 1, characterized in that: The initiator is at least one of potassium persulfate, ammonium persulfate and azobisisobutyronitrile.

9. The method for preparing a degradable flocculant for sludge according to claim 1, characterized in that: The solvent is any one of distilled water and ethanol aqueous solution, and the volume fraction of the ethanol aqueous solution is 20-25%.

10. Use of the degradable flocculant obtained by the preparation method according to any one of claims 1 to 9 in dewatering of municipal sludge.

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