Preparation method and application of 2-methylpyrrolidine-N-dithioformate

Abstract

The invention provides a preparation method of 2-methylpyrrolidine-N-dithioformate, which comprises the following steps: adding 2-methylpyrrolidine, water, an additive, carbon disulfide and alkali liquor into a reaction container, reacting, filtering, adsorbing with activated carbon, and dehydrating filtrate to obtain the 2-methylpyrrolidine-N-dithioformate, the additives are polyethylene glycol and malonic acid. The invention also provides an application of the 2-methylpyrrolidine-N-dithioformate (sodium salt or potassium salt) in removal of heavy metal ions in sewage or reduction of heavy metal ion re-dissolution. The preparation method provided by the invention is high in yield. According to the present invention, the 2-methylpyrrolidine-N-dithioformate can control the heavy metal ions in the sewage to a low concentration, and the complex precipitate formed by the 2-methylpyrrolidine-N-dithioformate and the heavy metal ions has characteristics of good stability and difficult re-dissolution;

Description

Technical Field

[0001] The present application relates to the field of water treatment technology, and in particular to a preparation method and application of 2-methylpyrrolidine-N-dithiocarboxylate. 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] The treatment of heavy metals with chemical agents is an efficient and relatively economical treatment method. When heavy metal treatment agents are used to treat wastewater containing heavy metals, they can form extremely insoluble precipitates with heavy metals in the water, thereby achieving the purpose of removing heavy metals from the water. Commonly used inorganic sulfides (such as sodium sulfide, sodium trithiocarbonate, etc.) are inexpensive, but the heavy metals in the treated wastewater are difficult to meet the standards and require further treatment before discharge. When the pH is low, the heavy metals will be released again. At the same time, inorganic sulfides will also generate hydrogen sulfide gas, causing secondary pollution.

[0004] The main organic heavy metal treatment agents on the market include DTC (dithiocarboxylate compounds) heavy metal treatment agents and TMT (trisodium trithiotriazine). 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 be greatly increased, making it difficult for the complex to precipitate. Further, when it is used for heavy metal wastewater treatment, the dosage of TMT is difficult to accurately calculate, which increases the difficulty of use. In order to solve this problem, the prior art uses TMT, while adding TMT in an appropriate excess, and supplementing it with polyferric sulfate. The addition of polyferric sulfate can not only serve as a coagulant to facilitate the precipitation of the complex, but also can block the excess thiol groups on TMT. However, the iron ions in the polyferric sulfate will replace some heavy metal ions originally captured by TMT (such as Cr 3+ The above defects of products such as TMT have limited their practical application (especially in the deep treatment of heavy metal ions).

[0005] Therefore, it is necessary to provide an efficient heavy metal treatment agent. Summary of the invention

[0006] In view of the above problems, the present invention provides a new heavy metal treatment agent 2-methylpyrrolidine-N-dithiocarbamate (sodium salt or potassium salt), and provides an economical synthesis and purification method, and its application method in heavy metal wastewater treatment. The N in the product is on the 2-methylpyrrolidine ring, the stability is higher than that of sodium dimethyldithiocarbamate, the product has a better treatment effect on many heavy metal ions than sodium dimethyldithiocarbamate and TMT, and the heavy metal ion content of the treated wastewater meets the relevant national emission standards (GB 21900-2008 electroplating pollutant emission standard, GB 8978-1996 sewage comprehensive emission standard, etc.).

[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 the second aspect of the present invention, the present invention provides the use of 2-methylpyrrolidine-N-dithiocarbamate in removing heavy metal ions in sewage or reducing the re-dissolution of heavy metal ions.

[0020] Preferably, the heavy metal ion is selected from Ni 2+ , Cu 2+ , Pb 2+ 、Co 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] Preferably, the pH value of the sewage is 3-5.

[0023] In summary, the present invention includes at least one of the following beneficial technical effects:

[0024] 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%.

[0025] 2. The present application provides an application of 2-methylpyrrolidine-N-dithioformate (sodium salt or potassium salt) in removing heavy metal ions from sewage or reducing the re-dissolution of heavy metal ions. 2-methylpyrrolidine-N-dithioformate can control the heavy metal ions in sewage to a lower concentration, and the complex precipitation formed by 2-methylpyrrolidine-N-dithioformate and heavy metal ions has good stability and is not easy to re-dissolve. DETAILED DESCRIPTION

[0026] 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.

[0027] Polyethylene glycol 1000 was purchased from Shanghai Bangao Chemical Co., Ltd.

[0028] 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:

[0029]

[0030] Preparation Example 1

[0031] 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.

[0032] Preparation Example 2

[0033] The difference between Preparation Example 2 and Preparation Example 1 is that the total reaction time is controlled to be 5 hours.

[0034] Preparation Example 3

[0035] 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.

[0036] Preparation Example 4

[0037] The difference between Preparation Example 4 and Preparation Example 1 is that the reaction temperature is 25°C.

[0038] Preparation Example 5

[0039] The difference between Preparation Example 5 and Preparation Example 1 is that the reaction temperature is 40°C.

[0040] Preparation Example 6

[0041] 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.

[0042] Preparation Example 7

[0043] 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.

[0044] Preparation Example 8

[0045] The difference between Preparation Example 8 and Preparation Example 1 is that 0.1 parts by mass of polyethylene glycol 1000 is added.

[0046] Preparation Example 9

[0047] The difference between Preparation Example 9 and Preparation Example 1 is that 10 parts by mass of polyethylene glycol 1000 are added.

[0048] Preparation Example 10

[0049] The difference between Preparation Example 10 and Preparation Example 1 is that 0.1 parts by mass of malonic acid is added.

[0050] Preparation Example 11

[0051] The difference between Preparation Example 11 and Preparation Example 1 is that 10 parts by mass of malonic acid are added.

[0052] Comparative Preparation Example 1

[0053] The difference between Comparative Preparation Example 1 and Preparation Example 1 is that polyethylene glycol 1000 is not added.

[0054] Comparative Preparation Example 2

[0055] The difference between Comparative Preparation Example 2 and Preparation Example 1 is that malonic acid is not added.

[0056] Comparative Preparation Example 3

[0057] The difference between Preparation Example 3 and Preparation Example 1 is that the mass of polyethylene glycol 1000 is replaced by trimethylbenzyl ammonium chloride.

[0058] Weigh the weight of the product of Preparation Example 1-11 and Comparative Preparation Example 1-3, the mass is V 1 , calculate the yield.

[0059] The calculation formula is: 100%*[(V 1 -V 2 -V 3 ) / M 1 ] / (100 / 85.25)

[0060] Among them, V 2 In Preparation Examples 1-11 and Comparative Preparation Examples 1-2, it is the mass of polyethylene glycol 1000, and in Comparative Preparation Example 3, it is the mass of trimethylbenzyl ammonium chloride; V 3 is the mass of malonic acid; M 1 V 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; 1 、V 2、V 3 All are measured by mass.

[0061] Table 1 Yields of Preparation Examples 1-11 and Comparative Preparation Examples 1-3

[0062] 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

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] The following examples are examples of treating heavy metal-containing sewage with sodium 2-methylpyrrolidine-N-dithiocarbamate prepared in Preparation Example 3 and other treatment agents. In the following examples, the sources of the heavy metal-containing sewage are as follows:

[0070] Take the heavy metal-containing wastewater from a nonferrous metal ore processing enterprise, first perform ICP-MS cation full scan on the heavy metal-containing wastewater, detect the content of various heavy metal ions in the heavy metal-containing wastewater, and calculate the corresponding molar content. The results are shown in Table 2 below.

[0071] Table 2 Heavy metal ions and their contents in the heavy metal wastewater

[0072]

[0073]

[0074] Then, the theoretical dosage of the heavy metal ion remover required is calculated based on the molar content of each metal ion and the valence state of the metal ion. 1 mol of divalent heavy metal ions requires 2 mol of active groups (such as 2-methylpyrrolidine-N-dithiocarboxylate with only one active group (dithiocarboxyl) requires 2 mol, and the theoretical dosage of TMT with three active groups (thiol) is 2 / 3 mol). Similarly, 1 mol of trivalent heavy metal ions requires 3 mol of active groups.

[0075] Example 1

[0076] In a 250mL beaker, add 200mL of the above-mentioned heavy metal-containing wastewater, and then add 0.3096mmol of 2-methylpyrrolidine-N-dithioformate sodium prepared by the preparation method of Preparation Example 3 (the molar ratio of 2-methylpyrrolidine-N-dithioformate sodium to total heavy metal ions is 2.4:1), stir at 300R / min for 15min on a Zhongrun ZR4-6 six-connection stirrer, filter with a 0.4μm filter membrane, and take the filtrate for heavy metal ion detection by ICP-MS (this step obtains the treatment effect of the heavy metal treatment agent, corresponding to the concentration detected immediately after treatment in Table 3). The precipitate on the filter membrane and the filter cake was transferred to the filtrate, and the pH was adjusted to 4.0 with dilute nitric acid. After stirring for 10 seconds, the mixture was allowed to stand at room temperature for 24 hours. Then, the mixture was stirred for 30 seconds and filtered with a 0.4 μm filter membrane. The filtrate was tested for heavy metal ions using ICP-MS (this step is to test the stability of the complex formed by the heavy metal treatment agent and the heavy metal, corresponding to the concentration detected after standing for 24 hours in Table 3).

[0077] Example 2

[0078] 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.

[0079] Example 3

[0080] 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.

[0081] Example 4

[0082] The difference between Example 4 and Example 1 is that 0.1032 mmol of TMT replaces 0.3096 mmol of 2-methylpyrrolidine-N-dithiocarboxylate sodium prepared by the preparation method of Preparation Example 1. During the experiment, the process filtrate was gray-brown and not clear and transparent.

[0083] Example 5

[0084] The difference between Example 5 and Example 4 is that 0.052 mmol of polyferric sulfate in terms of iron ions is added at the same time as TMT. The process filtrate is clear and transparent.

[0085] Table 3 shows the concentration results of the treatment agents in Examples 1-5 detected immediately after treatment and after standing for 24 hours.

[0086] Table 3 Treatment effect of Examples 1-5

[0087]

[0088]

[0089] Comparison of Example 1 with Example 2 in conjunction with Table 3 shows that sodium 2-methylpyrrolidine-N-dithiocarbamate is significantly better than potassium pyrrolidine-N-dithiocarbamate in removing heavy metals from wastewater and is not easily re-dissolved.

[0090] Comparison of Example 1 with Examples 3, 4, and 5 combined with Table 3 shows that the effect of 2-methylpyrrolidine-N-dithiocarbamate in removing heavy metals from wastewater is significantly better than TMT and sodium dimethyldithiocarbamate; in the stability test, sodium dimethyldithiocarbamate showed the worst stability among the four agents.

[0091] In actual heavy metal wastewater treatment, the insoluble complex formed by the heavy metal treatment agent and the heavy metal will form a precipitate in the sedimentation tank, and the precipitate will enter the collection tank with the water (the sludge content mainly composed of complex precipitates in the water in this step is about 0.5-2%). It will then undergo concentration, conditioning, and sludge dehydration. The entire process from adding heavy metal treatment agents to sludge dehydration takes from several hours to several days depending on the site. The complex formed by the heavy metal treatment agent and the heavy metal is unstable, and the heavy metal will dissolve into the water again. The heavy metal content in the subsequent filtrate will exceed the standard, causing secondary pollution.

[0092] 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-dithiocarbamate in removing heavy metal ions from sewage or reducing the re-dissolution of heavy metal ions.

9. The use according to claim 8, characterized in that: The heavy metal ion is selected from Ni 2+ , Cu 2+ , Pb 2+ 、Co 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.

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