Preparation method of 2-methylpyrrolidine-N-dithioformate and application of 2-methylpyrrolidine-N-dithioformate in fly ash solidification
By preparing and applying 2-methylpyrrolidine-N-dithioformate, the problems of insufficient stability and high water solubility of existing fly ash curing agents have been solved, and efficient and stable heavy metal curing effect has been achieved, which is in line with the country Standards reduce pollution risk.
Patent Information
- Application Number
- CN202411291293.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-14
- Publication Date
- 2024-12-17
AI Technical Summary
The existing fly ash curing agents have insufficient stability, high water solubility, difficulty in using and heavy metal resolubleness when treating heavy metals, resulting in unsatisfactory curing effect and difficulty in controlling the dosage, which increases the risk of pollution.
Using 2-methylpyrrolidine-N-dithioformate (sodium or potassium salt) as the new fly ash curing agent, through specific preparation methods and application processes, including the addition of 2-methyl to the reaction vessel Pyrrolidine, water, polyethylene glycol, malonic acid and alkali solution are reacted, filtered and adsorbed by activated carbon to obtain high yield 2-methylpyrrolidine-N-dithioformate, and in fly ash Used to cure heavy metal ions.
It achieves efficient and stable heavy metal ion curing, and the curing effect complies with the GB 5085.3-2007 standard. The heavy metal ion concentration in the extract liquid is controlled, the curing stability is ensured, the re-dissolution of heavy metals is avoided, and the difficulty of use is simplified.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of fly ash solidification, and in particular to a preparation method of 2-methylpyrrolidine-N-dithiocarboxylate and an application thereof in fly ash solidification. Background Art
[0002] Heavy metal pollutants are non-biodegradable, accumulate in the food chain and cause long-term harm. Even trace amounts of heavy metals pose high risks to the ecology and human health. It is very meaningful to control the emission and leakage of heavy metals.
[0003] Chemical treatment of heavy metals is an efficient and relatively economical treatment method. Heavy metal treatment agents can be used to solidify heavy metals in fly ash containing heavy metals (i.e. fly ash heavy metal solidification agents). Commonly used inorganic sulfide heavy metal treatment agents are inexpensive and can form precipitation with heavy metals, but when leached with acidic leaching solutions of relevant standards, sulfides will form hydrogen sulfide, which not only pollutes the environment, but also causes heavy metal ions to be released, and cannot play the role of fly ash solidification.
[0004] The main fly ash solidifying agents on the market include DTC (dithiocarboxylate compounds) heavy metal treatment agents, TMT (trisodium trithiocarbamate) and xanthate. The main DTC is sodium dimethyldithiocarbamate, which is efficient and economical in treating heavy metal ions, but it is easy to decompose, making the precipitate unstable. TMT has a relatively stable structure and strong heavy metal complexing ability. Although the three thiol groups make the density of TMT active groups (-S-) much higher than other products, due to the strong hydrophilicity of the thiol groups, as long as one thiol group is not complexed with heavy metal ions, the water solubility of the entire complex will increase significantly, causing the landfilled solidified fly ash to have heavy metal-containing complexes dissolved after contact with water. This feature also makes it difficult to accurately calculate the amount of TMT added, increasing the difficulty of use. In order to solve this problem, some people add TMT in excess when using TMT, and add polyferric sulfate. The addition of polyferric sulfate can block the excess thiol groups on TMT, but the iron ions in the polyferric sulfate will replace some heavy metal ions originally fixed by TMT (such as Cr 3+ The RO-CSS-bond in xanthate and black medicine of xanthate is easy to break, resulting in frequent re-dissolution of heavy metal ions, and has been gradually eliminated.
[0005] Therefore, it is necessary to provide an efficient fly ash solidifying agent. Summary of the invention
[0006] In view of the above problems, the present invention provides a new fly ash solidifying agent 2-methylpyrrolidine-N-dithiocarbamate (sodium salt or potassium salt), and provides an economical synthesis and purification method, and an application method thereof in fly ash solidification. The N in the product is on the 2-methylpyrrolidine ring, and the stability is higher than that of sodium dimethyldithiocarbamate. The product has better treatment effect on many heavy metal ions than sodium dimethyldithiocarbamate and TMT, and the solidification effect of the treated fly ash meets the "GB 5085.3-2007 Leaching Toxicity Identification Standard".
[0007] In order to solve at least one of the above technical problems, in the first aspect of the present application, the present application provides a method for preparing 2-methylpyrrolidine-N-dithiocarboxylate, comprising the following steps: adding 2-methylpyrrolidine, water, additives, carbon disulfide and alkali solution into a reaction container, reacting, filtering, adsorbing on activated carbon, and dehydrating the filtrate to obtain the 2-methylpyrrolidine-N-dithiocarboxylate;
[0008] The additives are polyethylene glycol and malonic acid.
[0009] Through the above technical scheme, adding polyethylene glycol and malonic acid during the reaction process can significantly improve the yield of 2-methylpyrrolidine-N-dithiocarboxylate.
[0010] The 2-methylpyrrolidine-N-dithiocarboxylate is preferably potassium 2-methylpyrrolidine-N-dithiocarboxylate or sodium 2-methylpyrrolidine-N-dithiocarboxylate.
[0011] That is, the structural formula of the 2-methylpyrrolidine-N-dithiocarboxylate is shown below.
[0012]
[0013] Preferably, the mass ratio of 2-methylpyrrolidine to water is 1:1.8-5.
[0014] Preferably, the mass ratio of polyethylene glycol to 2-methylpyrrolidine is 0.1-10:100.
[0015] Preferably, the mass ratio of malonic acid to 2-methylpyrrolidine is 0.1-10:100.
[0016] Preferably, the reaction temperature is 25-40°C.
[0017] Preferably, the reaction temperature is 4-6h.
[0018] Preferably, the alkali solution is an aqueous solution of potassium hydroxide or sodium hydroxide with a mass concentration of 40-60%, and the alkali solution is added dropwise into the reaction container.
[0019] In a second aspect of the present invention, the present invention provides the use of 2-methylpyrrolidine-N-dithiocarboxylate in the solidification of heavy metal ions in fly ash.
[0020] Preferably, the heavy metal ion is selected from Cu 2+ , Pb 2+ 、Cd 2+ At least one of .
[0021] Preferably, the 2-methylpyrrolidine-N-dithiocarbamate is prepared by the preparation method described in the first aspect of the present invention.
[0022] In summary, the present invention includes at least one of the following beneficial technical effects:
[0023] 1. The present application provides an economical preparation method of 2-methylpyrrolidine-N-dithiocarboxylate (sodium salt or potassium salt), which has a fast reaction speed and high yield. After 6 hours of reaction, the yield can reach up to 91.9%.
[0024] 2. The present application provides an application of 2-methylpyrrolidine-N-dithiocarboxylate (sodium salt or potassium salt) in the solidification of heavy metal ions in fly ash. 2-methylpyrrolidine-N-dithiocarboxylate can solidify heavy metal ions in fly ash, with good solidification effect and good solidification stability after solidification, and can control the content of Pb in the leaching solution. 2+ The concentration was below 150 μg / L, Cd 2+ When the concentration is below 150 μg / L, Cu 2+ The concentration is below 20μg / L. DETAILED DESCRIPTION
[0025] The present invention will be further described below in conjunction with specific examples, but the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. In the following examples, if specific conditions are not specified, they are carried out according to normal conditions or conditions recommended by the manufacturer. The methods used are conventional methods known in the art unless otherwise specified, and the consumables and reagents used are commercially available unless otherwise specified. Unless otherwise specified, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the recorded content may also be applied to the present invention.
[0026] Polyethylene glycol 1000 was purchased from Shanghai Bangao Chemical Co., Ltd.
[0027] In the preparation example, the reaction formula for preparing 2-methylpyrrolidine-N-dithiocarboxylic acid potassium or 2-methylpyrrolidine-N-dithiocarboxylic acid sodium is as follows:
[0028]
[0029] Preparation Example 1
[0030] 100 parts by mass of 2-methylpyrrolidine and 300 parts by mass of deionized water were added to a four-necked flask. Under stirring, nitrogen was introduced for 30 minutes, and then 3 parts by mass of polyethylene glycol 1000 were added, and then 5 parts by mass of malonic acid were added. After stirring, 98.35 parts by mass of carbon disulfide (the molar ratio of 2-methylpyrrolidine to carbon disulfide was 1:1.1) was added, and then the nitrogen was turned on, the temperature was adjusted to 30°C and the stirring reaction was started, and then 131.78 parts by mass of 50wt% potassium hydroxide aqueous solution (the molar ratio of 2-methylpyrrolidine to potassium hydroxide was 1:1) was added dropwise, and the addition was completed in 3.5 hours. The total reaction time was controlled to be 6 hours, and the mixture was filtered. The filtrate (clear aqueous solution) after filtration was adsorbed by an activated carbon column to remove excess carbon disulfide. The residence time of the product aqueous solution through the activated carbon column was 30 minutes. Then, the mixture was placed in a vacuum drying oven and dried at 60°C to obtain 2-methylpyrrolidine-N-dithioformate potassium.
[0031] Preparation Example 2
[0032] The difference between Preparation Example 2 and Preparation Example 1 is that the total reaction time is controlled to be 5 hours.
[0033] Preparation Example 3
[0034] The difference between Preparation Example 3 and Preparation Example 1 is that 93.96 parts by mass of 50 wt % sodium hydroxide aqueous solution is used instead of 131.78 parts by mass of 50 wt % potassium hydroxide aqueous solution to obtain sodium 2-methylpyrrolidine-N-dithiocarboxylate.
[0035] Preparation Example 4
[0036] The difference between Preparation Example 4 and Preparation Example 1 is that the reaction temperature is 25°C.
[0037] Preparation Example 5
[0038] The difference between Preparation Example 5 and Preparation Example 1 is that the reaction temperature is 40°C.
[0039] Preparation Example 6
[0040] The difference between Preparation Example 6 and Preparation Example 1 is that the amount of deionized water added is reduced to 180 parts by weight, and the reaction system is obviously turbid before filtration.
[0041] Preparation Example 7
[0042] The difference between Preparation Example 7 and Preparation Example 1 is that the amount of deionized water added is increased to 500 parts by mass.
[0043] Preparation Example 8
[0044] The difference between Preparation Example 8 and Preparation Example 1 is that 0.1 parts by mass of polyethylene glycol 1000 is added.
[0045] Preparation Example 9
[0046] The difference between Preparation Example 9 and Preparation Example 1 is that 10 parts by mass of polyethylene glycol 1000 are added.
[0047] Preparation Example 10
[0048] The difference between Preparation Example 10 and Preparation Example 1 is that 0.1 parts by mass of malonic acid is added.
[0049] Preparation Example 11
[0050] The difference between Preparation Example 11 and Preparation Example 1 is that 10 parts by mass of malonic acid are added.
[0051] Comparative Preparation Example 1
[0052] The difference between Comparative Preparation Example 1 and Preparation Example 1 is that polyethylene glycol 1000 is not added.
[0053] Comparative Preparation Example 2
[0054] The difference between Comparative Preparation Example 2 and Preparation Example 1 is that malonic acid is not added.
[0055] Comparative Preparation Example 3
[0056] The difference between Preparation Example 3 and Preparation Example 1 is that the mass of polyethylene glycol 1000 is replaced by trimethylbenzyl ammonium chloride.
[0057] The products of Preparation Example 1-11 and Comparative Preparation Example 1-3 were weighed, with the mass being V1, and the yield was calculated.
[0058] The calculation formula is: 100%*[(V1-V2-V3) / M1] / (100 / 85.25)
[0059] Among them, V2 is the mass of polyethylene glycol 1000 in Preparation Examples 1-11 and Comparative Preparation Examples 1-2, and is the mass of trimethylbenzyl ammonium chloride in Comparative Preparation Example 3; V3 is the mass of malonic acid; M1 is the molar mass of the corresponding product (potassium 2-methylpyrrolidine-N-dithiocarboxylate or sodium 2-methylpyrrolidine-N-dithiocarboxylate), and 85.15 is the molar mass of 2-methylpyrrolidine; V1, V2, and V3 are all measured in parts by mass.
[0060] Table 1 Yields of Preparation Examples 1-11 and Comparative Preparation Examples 1-3
[0061] Preparation Example Yield (%) Preparation Example 1 91.8 Preparation Example 2 87.5 Preparation Example 3 91.6 Preparation Example 4 88.5 Preparation Example 5 91.9 Preparation Example 6 55.3 Preparation Example 7 89.6 Preparation Example 8 76.6 Preparation Example 9 85.2 Preparation Example 10 78.4 Preparation Example 11 90.3 Comparative Preparation Example 1 69.3 Comparative Preparation Example 2 62.4 Comparative Preparation Example 3 59.5
[0062] Comparison of Preparation Example 1 with Comparative Preparation Example 1 and Comparative Preparation Example 2 in combination with Table 1 shows that when polyethylene glycol or malonic acid is not added during the reaction, the yield of 2-methylpyrrolidine-N-potassium dithiocarboxylate is relatively low.
[0063] Comparison of Preparation Example 1 and Comparative Preparation Example 3 in combination with Table 1 shows that when polyethylene glycol is replaced with other phase transfer catalysts, the yield of 2-methylpyrrolidine-N-dithiocarboxylic acid potassium is lower than that of Comparative Preparation Example 1. This may be because replacing the phase transfer catalyst with trimethylbenzyl ammonium chloride not only does not help the yield much, but also precipitates the generated product and then filters it out, so the yield is lower.
[0064] Comparison of Preparation Example 1 with Preparation Example 4 and Preparation Example 5 in conjunction with Table 1 shows that the reaction temperature affects the yield of 2-methylpyrrolidine-N-potassium dithiocarboxylate.
[0065] Comparison of Preparation Example 1 with Preparation Example 6 and Preparation Example 7 in combination with Table 1 shows that when the mass ratio of water to 2-methylpyrrolidine is too low, the yield of 2-methylpyrrolidine-N-dithioformate potassium is very low. The mass ratio of water to 2-methylpyrrolidine will affect the yield of 2-methylpyrrolidine-N-dithioformate potassium.
[0066] Comparison of Preparation Example 1 with Preparation Example 8 and Preparation Example 9 in conjunction with Table 1 shows that the mass ratio of polyethylene glycol to 2-methylpyrrolidine will affect the yield of 2-methylpyrrolidine-N-potassium dithiocarboxylate.
[0067] Comparison of Preparation Example 1 with Preparation Example 10 and Preparation Example 11 in combination with Table 1 shows that the mass ratio of malonic acid to 2-methylpyrrolidine will affect the yield of 2-methylpyrrolidine-N-potassium dithiocarboxylate.
[0068] The following example is an example of treating fly ash from a waste incineration power plant using the sodium 2-methylpyrrolidine-N-dithiocarbamate prepared in Preparation Example 3 and other treatment agents.
[0069] Example 1
[0070] 2 parts by weight of dried 2-methylpyrrolidine-N-sodium dithiocarboxylate prepared by the preparation method of Preparation Example 3 were diluted with water to 30 parts by weight for standby use. 100 parts by weight of fly ash from a waste incineration power plant after drying to constant weight was added to a beaker, and then 30 parts by weight of water containing 2-methylpyrrolidine-N-sodium dithiocarboxylate was slowly and evenly poured into the beaker. During the water addition process, the water was slowly poured and fully stirred with the fly ash to fully mix and obtain the treated fly ash.
[0071] Example 2
[0072] The difference between Example 2 and Example 1 is that an equimolar amount of sodium pyrrolidine-N-dithiocarbamate (CAS No.: 872-71-9) is used to replace sodium 2-methylpyrrolidine-N-dithiocarbamate.
[0073] Example 3
[0074] The difference between Example 3 and Example 1 is that an equimolar amount of sodium dimethyldithiocarbamate is used to replace sodium 2-methylpyrrolidine-N-dithiocarbamate.
[0075] Example 4
[0076] The difference between Example 4 and Example 1 is that TMT replaces sodium 2-methylpyrrolidine-N-dithiocarbamate, and the molar amount of TMT is 1 / 3 of the molar amount of sodium 2-methylpyrrolidine-N-dithiocarbamate in Example 1.
[0077] Example 5
[0078] The difference between Example 5 and Example 4 is that the molar amount of TMT is 0.5 times that of Example 4.
[0079] Example 6
[0080] The difference between Example 6 and Example 4 is that the molar amount of TMT is twice that of Example 4.
[0081] Example 7
[0082] The difference between Example 7 and Example 4 is that 0.5 parts by mass of polyferric sulfate is added simultaneously with the addition of TMT.
[0083] Comparative Example 1
[0084] The difference between Comparative Example 1 and Example 1 is that no sodium 2-methylpyrrolidine-N-dithioformate is added. That is, 100 parts by weight of fly ash from a waste incineration power plant after drying to a constant weight is added to a beaker, and then 30 parts by weight of water is slowly and evenly poured into the beaker. During the water addition process, the water is slowly poured and fully stirred with the fly ash to obtain the treated fly ash.
[0085] Heavy metal leaching and heavy metal ion detection in fly ash after treatment in Examples 1-7 and Comparative Example 1:
[0086] The first extraction was carried out according to the acetic acid buffer solution method of HJ / T 300-2007 Solid Waste Leaching Toxicity Leaching Method.
[0087] The heavy metal ions in the blank fly ash leaching solution (the leaching solution corresponding to Comparative Example 1) were detected by ICP-OES; the heavy metal ions in the treated fly ash leaching solution (the leaching solution corresponding to Examples 1-7) were detected by ICP-MS. The results are shown in Table 2 as the concentration of heavy metal ions in the primary leaching solution.
[0088] Table 2 Treatment effects of different embodiments
[0089]
[0090] The filter residue on the membrane during the first leaching of Example 1 and Example 2 was taken out, and leached again according to the acetic acid buffer solution method of HJ / T 300-2007 Solid Waste Leaching Toxicity Leaching Method to obtain the leaching solution. The heavy metal ions in the blank fly ash leaching solution were detected by ICP-OES; the heavy metal ions in the treated fly ash leaching solution were detected by ICP-MS, and the results are shown in Table 3 for the heavy metal ion concentration in the secondary leaching solution.
[0091] Table 3 Treatment effect of secondary leaching of Examples 1 and 2
[0092]
[0093] It can be seen from Table 2 that the fly ash solidification effect of sodium 2-methylpyrrolidine-N-dithiocarbamate is much better than that of sodium pyrrolidine-N-dithiocarbamate, sodium dimethyldithiocarbamate and TMT. The heavy metal ion concentration of the leaching solution is much lower than the national standard, which can control the Pb content in the primary leaching solution. 2+ The concentration was below 150 μg / L, Cd 2+ When the concentration is below 150 μg / L, Cu 2+ The concentration is below 20μg / L.
[0094] Because the sources of fly ash vary greatly, fly ash solidifiers are usually added in excess. In this case, when using fly ash solidifiers with multiple active groups such as TMT, there will inevitably be many complexes with excess active groups that do not participate in the complexation. Such active groups will greatly increase the water solubility of the complex, making the fly ash containing such complexes easily leached out with the leaching liquid during leaching, and at the same time making the leaching liquid darker in color.
[0095] It can be seen from Examples 1 and 2 combined with Table 3 that the fly ash solidification stability of sodium 2-methylpyrrolidine-N-dithiocarboxylate is better than that of potassium pyrrolidine-N-dithiocarboxylate. 2+ The concentration is below 200 μg / L, Cd 2+ When the concentration is below 200 μg / L, Cu 2+ The concentration is below 50μg / L.
[0096] In actual application, it is shown that when the landfilled fly ash is infiltrated and moistened by rainwater or other water sources, this type of water-soluble heavy metal complex will be carried out by water. If the landfill is not well waterproofed, this type of water-soluble heavy metal complex will infiltrate into normal soil. As the organic part of the leaked complex gradually decomposes, the heavy metal will be released again, causing soil pollution around the landfill. In contrast, 2-methylpyrrolidine-N-dithiocarboxylate not only has excellent heavy metal solidification effect, but also has good stability. After solidification, it is not easy to release heavy metals again to cause secondary pollution, and it is easy to use.
[0097] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.
Claims
1. A method for preparing 2-methylpyrrolidine-N-dithioformate, characterized in that: The method comprises the following steps: adding 2-methylpyrrolidine, water, additives, carbon disulfide and alkali solution into a reaction container, reacting, filtering, adsorbing on activated carbon, and dehydrating the filtrate to obtain the 2-methylpyrrolidine-N-dithiocarboxylate; The additives are polyethylene glycol and malonic acid.
2. The method for preparing 2-methylpyrrolidine-N-dithioformate according to claim 1, characterized in that: The mass ratio of 2-methylpyrrolidine to water is 1:1.8-5.
3. The method for preparing 2-methylpyrrolidine-N-dithioformate according to claim 1, characterized in that: The mass ratio of polyethylene glycol to 2-methylpyrrolidine is 0.1-10:
100.
4. The method for preparing 2-methylpyrrolidine-N-dithiocarboxylate according to claim 1, characterized in that: The mass ratio of malonic acid to 2-methylpyrrolidine is 0.1-10:
100.
5. The method for preparing 2-methylpyrrolidine-N-dithiocarboxylate according to claim 1, characterized in that: The reaction temperature is 25-40°C.
6. The method for preparing 2-methylpyrrolidine-N-dithiocarboxylate according to claim 1, characterized in that: The reaction temperature is 4-6h.
7. The method for preparing 2-methylpyrrolidine-N-dithiocarboxylate according to claim 1, characterized in that: The alkali solution is an aqueous solution of potassium hydroxide or sodium hydroxide with a mass concentration of 40-60%, and the alkali solution is added dropwise into the reaction container.
8. Application of 2-methylpyrrolidine-N-dithiocarboxylate in the solidification of heavy metal ions in fly ash.
9. The use according to claim 8, characterized in that: The heavy metal ion is selected from Cu 2+ , Pb 2+ 、Cd 2+ At least one of .
10. The use according to claim 8, characterized in that: The 2-methylpyrrolidine-N-dithiocarboxylate is prepared by the preparation method according to any one of claims 1 to 7.