CN108912328B

CN108912328B - Preparation method of heavy metal ion chelating agent

Info

Publication number: CN108912328B
Application number: CN201810865052.3A
Authority: CN
Inventors: 胡清; 童立志; 唐一; 王峰; 胡滨; 王宏
Original assignee: Southwest University of Science and Technology
Current assignee: Southwest University of Science and Technology
Priority date: 2018-08-01
Filing date: 2018-08-01
Publication date: 2021-11-09
Anticipated expiration: 2038-08-01
Also published as: CN108912328A

Abstract

The invention provides a preparation method of a heavy metal ion chelating agent. The preparation method comprises the following steps: (1) reacting polyethyleneimine and carbon disulfide serving as raw materials and alcohol and/or ether serving as a solvent to generate a solid intermediate product; (2) and reacting the solid intermediate product with alkali to obtain the heavy metal ion chelating agent. The invention takes alcohol and/or ether as solvent, can form homogeneous reaction system, is helpful for full contact reaction of polyethyleneimine and carbon disulfide, and shortens reaction time; alcohol and ether can be recycled more conveniently, so that the production cost is reduced; the alkali is introduced after the reaction of the polyethyleneimine and the carbon disulfide, so that the side reaction of the carbon disulfide and the alkali is avoided, and the yield of the product is improved.

Description

Preparation method of heavy metal ion chelating agent

Technical Field

The invention belongs to the technical field of chelating agents, and particularly relates to a preparation method of a heavy metal ion chelating agent.

Background

Heavy metal contamination refers to environmental contamination caused by heavy metals or compounds thereof. Mainly caused by human factors such as mining, waste gas discharge, sewage irrigation, use of products with heavy metals exceeding standards and the like. Unlike the pollution of other organic compounds, many organic compounds can reduce or eliminate the harmfulness by physical, chemical or biological purification in nature, while heavy metals are rich and difficult to degrade in the environment. The general method for treating the heavy metal wastewater comprises a physical or chemical method.

Currently, the most common heavy metal wastewater treatment method is chemical precipitation. The method is to combine the chelating agent with heavy metal ions in the wastewater to generate chelate which is insoluble in water and stable in property, and the chelate generally exists in the form of precipitation or suspension. The method for separating heavy metals from wastewater can effectively achieve the aim of controlling the heavy metals.

Heavy metal chelating agents can be divided into small molecules and high molecules according to different molecular weights; the micromolecule chelating agent is combined with metal ions to generate a suspended chelate, and the chelate can be settled by adding a flocculating agent. The macromolecular chelating agent has the characteristic of good sedimentation property.

At present, in order to efficiently and economically control the heavy metal pollution problem, a high-quality low-cost high-molecular heavy metal chelating agent needs to be developed on the basis of the prior art. The method for synthesizing the high-molecular heavy metal chelating agent comprises two methods: one is to introduce or form a chelating structure on a polymer skeleton by various methods, and the other is to prepare the polymer by a high molecular method by taking a small molecular complexing agent or a chelating agent as a raw material.

In recent years, a macromolecular dithiocarbamate chelating agent synthesized by taking polyethyleneimine as a framework becomes a hot spot concerned by the heavy metal ion wastewater treatment industry.

In the existing preparation methods of dithiocarbamate chelating agents, such as CN 101081827A, CN 103965471A and CN 105084502A, water is used as a solvent, polyethyleneimine is mixed with a sodium hydroxide solution, and then a carbon disulfide solution is dropwise added for reaction, so that an orange product is obtained. However, this preparation method has problems of long reaction time, low product yield, and by-products such as orange-colored sodium thiosulfate, which limits the mass production and application of dithiocarbamate, and leaves room for improvement.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a preparation method of a heavy metal ion chelating agent. The method can reduce side reaction, shorten reaction time, improve the yield of the chelating agent and reduce the cost.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a preparation method of a heavy metal ion chelating agent, which comprises the following steps:

(1) reacting polyethyleneimine and carbon disulfide serving as raw materials and alcohol and/or ether serving as a solvent to generate a solid intermediate product;

(2) and reacting the solid intermediate product with alkali to obtain the heavy metal ion chelating agent.

The inventor discovers that in the process of preparing the high-molecular dithiocarbamate chelating agent by adopting the existing method, the raw materials are layered to form a heterogeneous system. Wherein, the lower layer is carbon disulfide, the middle layer is sodium hydroxide aqueous solution, and the upper layer is polyethyleneimine aqueous solution. In the reaction process, carbon disulfide and polyethyleneimine are difficult to fully contact, long-time stirring is needed, and carbon disulfide is easy to react with sodium hydroxide to generate orange sodium thiosulfate, so that the product yield is low.

The invention adopts alcohol and/or ether as solvent, homogeneous reaction system can be formed, polyethyleneimine and carbon disulfide can fully contact and react, which is beneficial to shortening reaction time; the solid intermediate product generated by the reaction is insoluble in alcohol and ether, can be separated by simple filtration, and then reacts with alkali to obtain the light yellow green dithiocarbamate chelating agent, so that the contact between carbon disulfide and alkali is avoided, the side reaction is reduced, and the product yield is improved. Moreover, alcohols and ethers are easier to recycle than water, which helps to reduce production costs.

As a preferred technical scheme of the invention, the preparation method comprises the following steps:

(1) dropwise adding the polyethyleneimine solution into a carbon disulfide solution by using alcohol and/or ether as a solvent, and reacting to obtain a solid intermediate product;

(2) and dissolving the solid intermediate product in alkali liquor, and reacting to obtain the heavy metal ion chelating agent.

As a preferred embodiment of the present invention, the molar ratio of the repeating unit of polyethyleneimine to the carbon disulfide is 0.3-0.8: 1; for example, it may be 0.3:1, 0.32:1, 0.35:1, 0.38:1, 0.4:1, 0.42:1, 0.45:1, 0.48:1, 0.5:1, 0.52:1, 0.55:1, 0.58:1, 0.6:1, 0.62:1, 0.65:1, 0.68:1, 0.7:1, 0.72:1, 0.75:1, 0.78:1 or 0.8: 1.

As a preferable technical scheme of the invention, the number average molecular weight of the polyethyleneimine is 1000-100000; for example, 1000, 1500, 2000, 3000, 5000, 6000, 8000, 10000, 15000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000, 100000, or the like can be mentioned.

The inventor finds that the larger the molecular weight of polyethyleneimine in the aqueous phase, the more obvious the delamination phenomenon with alkali and carbon disulfide, and the more side reaction ratio, the lower the product yield. Therefore, the method provided by the invention is particularly suitable for preparing the chelating agent taking polyethyleneimine with large molecular weight (more than 2000) as a raw material.

As a preferable technical scheme of the invention, the concentration of the polyethyleneimine solution is 80-125 g/L; for example, 80g/L, 100g/L, 105g/L, 110g/L, 115g/L, 120g/L, 125g/L, or the like may be used.

Preferably, the concentration of the carbon disulfide solution is 200-250 g/L; for example, 200g/L, 210g/L, 220g/L, 230g/L, 240g/L, 250g/L, etc. may be used.

As a preferred technical scheme of the invention, the temperature of the reaction in the step (1) is 5-40 ℃; for example, it can be 5 ℃, 6 ℃, 8 ℃, 10 ℃, 12 ℃, 13 ℃, 15 ℃, 16 ℃, 18 ℃, 20 ℃, 22 ℃, 23 ℃, 25 ℃, 26 ℃, 28 ℃, 30 ℃, 32 ℃, 33 ℃, 35 ℃, 36 ℃, 38 ℃ or 40 ℃ and the like; more preferably 5-20 deg.c.

Preferably, the reaction time in step (1) is 1-3 h; for example, 1h, 1.2h, 1.3h, 1.5h, 1.6h, 1.8h, 2h, 2.2h, 2.3h, 2.5h, 2.6h, 2.8h, 3h, etc.

In addition, since the polyethyleneimine starts to react with carbon disulfide during the dropwise addition, the reaction time is the time from the start of the addition of the raw materials to the end of the reaction.

In a preferred embodiment of the present invention, the alcohol is ethanol.

Preferably, the ether is diethyl ether.

As a preferred embodiment of the present invention, the step (1) further comprises: after the reaction is finished, solid-liquid separation and washing are carried out.

In the present invention, the method of the solid-liquid separation and washing is not particularly limited, and, for example, a method of washing with an alcohol and/or an ether and suction filtration to perform solid-liquid separation may be selected.

Preferably, the molar ratio of the base to the recurring units of the polyethyleneimine is 1 (1-1.5); for example, it may be 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1: 1.5.

In a preferred embodiment of the present invention, the alkali is sodium hydroxide and/or potassium hydroxide, preferably sodium hydroxide.

(1) controlling the temperature to be 5-40 ℃, taking alcohol and/or ether as a solvent, dropwise adding a polyethyleneimine solution into a carbon disulfide solution for reaction, wherein the molar ratio of a repeating unit of polyethyleneimine to carbon disulfide is 0.3-0.8:1, the time from the beginning of dropwise adding to the end of the reaction is 1-3h, and carrying out solid-liquid separation and washing to obtain a solid intermediate product;

(2) and (3) dissolving the solid intermediate product in a sodium hydroxide solution, wherein the molar ratio of the sodium hydroxide to the repeating unit of the polyethyleneimine is 1 (1-1.5), and reacting to obtain the heavy metal ion chelating agent.

The heavy metal ion chelating agent obtained by the method is in the form of an aqueous solution, and a person skilled in the art can remove water (such as vacuum drying) according to actual needs to obtain a solid product.

Compared with the prior art, the invention has the following beneficial effects:

the invention takes alcohol and/or ether as solvent, can form homogeneous reaction system, is helpful for full contact reaction of polyethyleneimine and carbon disulfide, and shortens reaction time; alcohol and ether can be recycled more conveniently, so that the production cost is reduced; the alkali is introduced after the reaction of the polyethyleneimine and the carbon disulfide, so that the side reaction of the carbon disulfide and the alkali is avoided, and the yield of the product reaches 90-95%.

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

The embodiment provides a preparation method of a heavy metal ion chelating agent, which comprises the following steps:

(1) respectively preparing 125g/L polyethyleneimine ethyl ether solution (number average molecular weight is 1000) and 250g/L carbon disulfide ethyl ether solution;

(2) controlling the temperature at 5 ℃, dropwise adding the polyethyleneimine diethyl ether solution into the carbon disulfide diethyl ether solution for reaction, wherein the molar ratio of the polyethyleneimine repeating unit to the carbon disulfide is 0.8:1, the time from the beginning of dropwise adding to the end of reaction is 1.5h, and after the reaction is finished, performing suction filtration and washing with diethyl ether to obtain a solid intermediate product;

(3) and (3) dissolving the solid intermediate product obtained in the step (2) in a sodium hydroxide solution according to the molar ratio of the sodium hydroxide to the polyethyleneimine repeating unit of 1:1 to obtain a light yellow-green heavy metal ion chelating agent solution, and drying to obtain the solid heavy metal ion chelating agent.

The preparation method provided by the embodiment can reduce side reactions, shorten the reaction time, improve the yield of the chelating agent (90.7%) and reduce the cost.

Example 2

(1) respectively preparing 125g/L polyethyleneimine ethanol solution (with the number average molecular weight of 5000) and 250g/L carbon disulfide ethanol solution;

(2) controlling the temperature at 10 ℃, dropwise adding polyethyleneimine ethanol solution into carbon disulfide ethanol solution for reaction, wherein the molar ratio of a polyethyleneimine repeating unit to carbon disulfide is 0.7:1, the time from the beginning of dropwise adding to the end of reaction is 2 hours, performing suction filtration after the reaction is finished, and washing with absolute ethyl alcohol to obtain a solid intermediate product;

(3) and (3) dissolving the solid intermediate product obtained in the step (2) in a sodium hydroxide solution according to the molar ratio of the sodium hydroxide to the polyethyleneimine repeating unit of 1:1.2 to obtain a light yellow-green heavy metal ion chelating agent solution, and drying to obtain the solid heavy metal ion chelating agent.

The preparation method provided by the embodiment can reduce side reactions, shorten the reaction time, improve the yield of the chelating agent (91.4%) and reduce the cost.

Example 3

(1) respectively preparing 125g/L polyethyleneimine ethanol solution (the number average molecular weight is 1 ten thousand) and 200g/L carbon disulfide ethanol solution;

(2) controlling the temperature to be 15 ℃, dropwise adding the polyethyleneimine ethanol solution into a carbon disulfide ethanol solution for reaction, wherein the molar ratio of a repeating unit of polyethyleneimine to carbon disulfide is 0.5:1, the time from the beginning of dropwise adding to the end of reaction is 2 hours, and after the reaction is finished, performing suction filtration and drying to obtain a solid intermediate product;

(3) and (3) dissolving the solid intermediate product obtained in the step (2) in a sodium hydroxide solution according to the molar ratio of the sodium hydroxide to the polyethyleneimine repeating unit of 1:1.3 to obtain a light yellow-green heavy metal ion chelating agent, and drying to obtain the solid heavy metal ion chelating agent.

The preparation method provided by the embodiment can reduce side reactions, shorten the reaction time, improve the yield of the chelating agent (93.5%) and reduce the cost.

Example 4

(1) respectively preparing 125g/L polyethyleneimine ethanol solution (the number average molecular weight is 3 ten thousand) and 200g/L carbon disulfide ethanol solution;

(2) controlling the temperature to be 20 ℃, dropwise adding the polyethyleneimine ethanol solution into a carbon disulfide ethanol solution for reaction, wherein the molar ratio of a repeating unit of polyethyleneimine to carbon disulfide is 0.4:1, the time from the beginning of dropwise adding to the end of reaction is 2.5h, performing suction filtration after the reaction is finished, and washing with absolute ethyl alcohol to obtain a solid intermediate product;

The preparation method provided by the embodiment can reduce side reactions, shorten the reaction time, improve the yield of the chelating agent (94.0%) and reduce the cost.

Example 5

(1) respectively preparing 100g/L polyethyleneimine ethanol solution (with the number average molecular weight of 10 ten thousand) and 200g/L carbon disulfide ethanol solution;

(2) controlling the temperature to be 40 ℃, dropwise adding the polyethyleneimine ethanol solution into a carbon disulfide ethanol solution for reaction, wherein the molar ratio of a repeating unit of polyethyleneimine to carbon disulfide is 0.3:1, the time from the beginning of dropwise adding to the end of reaction is 1h, performing suction filtration after the reaction is finished, and washing with absolute ethanol to obtain a solid intermediate product;

(3) and (3) dissolving the solid intermediate product obtained in the step (2) in a sodium hydroxide solution according to the molar ratio of the sodium hydroxide to the polyethyleneimine repeating unit of 1:1.5 to obtain a light yellow-green heavy metal ion chelating agent solution, and drying to obtain the solid heavy metal ion chelating agent.

The preparation method provided by the embodiment can reduce side reactions, shorten the reaction time, improve the yield of the chelating agent (94.1%) and reduce the cost.

The heavy metal ion chelating agents provided in examples 1 to 5 were prepared into 50mg/mL aqueous solutions and were ready for use. Preparing 10mg/L Pb²⁺、Ni²⁺、Cu²⁺、Cd²⁺Each 100mL of the solution was used as a simulated wastewater. Adding the heavy metal ion chelating agent aqueous solution at a molar ratio of chelating agent to metal ion of 2:1, adjusting pH to acidity (pH 5.0-5.5) under stirring, standing for 15min, and filtering. And measuring the concentration of the heavy metal ions in the supernatant after the simulated wastewater is treated by ICP-MS (inductively coupled plasma mass spectrometry), and calculating to obtain the removal rate of various heavy metal ions. The removal rate of each metal ion is shown in table 1 below:

TABLE 1

	Pb²⁺	Ni²⁺	Cu²⁺	Cd²⁺
					Example 1	99.8％	99.8％	99.9％	99.7％
Example 2	99.6％	99.7％	99.9％	99.8％
					Example 3	99.9％	99.8％	99.8％	99.9％
Example 4	99.8％	99.5％	99.9％	99.8％
					Example 5	99.8％	99.9％	99.9％	99.8％

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims

1. The preparation method of the heavy metal ion chelating agent is characterized by comprising the following steps:

(2) dissolving the solid intermediate product in alkali liquor, and reacting to obtain the heavy metal ion chelating agent;

the molar ratio of the repeating unit of the polyethyleneimine to the carbon disulfide is 0.3-0.8: 1;

the number average molecular weight of the polyethyleneimine is 1000-100000;

the alcohol is ethanol;

the ether is diethyl ether.

2. The method as claimed in claim 1, wherein the concentration of the polyethyleneimine solution is 100-125 g/L.

3. The method as claimed in claim 1, wherein the concentration of the carbon disulfide solution is 200-250 g/L.

4. The method according to claim 1, wherein the temperature of the reaction in the step (1) is 5 to 40 ℃.

5. The method according to claim 1, wherein the reaction time in the step (1) is 1 to 3 hours.

6. The method of claim 1, wherein step (1) further comprises: after the reaction is finished, solid-liquid separation and washing are carried out.

7. The method according to claim 1, wherein the molar ratio of the base to the repeating units of polyethyleneimine is 1 (1-1.5).

8. The method according to claim 1, wherein the alkali is sodium hydroxide and/or potassium hydroxide.

9. The method of claim 1, wherein the base is sodium hydroxide.

10. The method of claim 1, comprising the steps of:

(1) controlling the temperature to be 5-20 ℃, dropwise adding the polyethyleneimine solution into the carbon disulfide solution for reaction, wherein the molar ratio of the repeating unit of the polyethyleneimine to the carbon disulfide is 0.3-0.8:1, the time from the beginning of dropwise adding to the end of the reaction is 1-3h, and obtaining a solid intermediate product after solid-liquid separation and washing;