Preparation method of modified humic acid, prepared product and application

Abstract

The invention provides a preparation method of modified humic acid, a prepared product and application. The preparation method comprises the following steps: adding humic acid into an aqueous solution, adding an amination reagent which is piperazine with amino and hydroxyl, then adding concentrated sulfuric acid, and reacting under the conditions of heating and ultrasonic waves to obtain aminated humic acid; adding the aminated humic acid into an alkaline solution, adjusting the pH value to 9-11, adding a polyphenyl compound of which the chemical structural formula comprises a halogen atom and at least one benzene ring, carrying out a reaction under a heating condition, and adjusting the pH value of the product to 7-7.5 after the reaction is finished, so as to obtain the modified humic acid. The humic acid is subjected to chemical grafting modification, so that the balance of the molecular structure of the humic acid is improved, the humic acid has good complexing, adsorbing and buffering capacities, and particularly, the remediation capacity of the humic acid in the aspect of remediation of heavy metal contaminated soil and organic matter contaminated soil is improved, so that the remediation effect is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and particularly relates to a preparation method of modified humic acid, a product obtained thereby, and applications thereof. Background Art

[0002] Humic Acid is a kind of high-molecular organic substance widely existing in nature, mainly formed by the microbial decomposition, transformation and geological action of animal and plant residues. Its structure is complex and contains various functional groups such as hydroxyl, carboxyl, phenolic hydroxyl, aromatic ring and quinone group, and the above groups endow it with good complexing, adsorption and buffering capabilities. Humic acid is usually distributed in soil, water body, coal (such as peat and lignite), and is an important part of soil organic matter.

[0003] Due to the fact that humic acid itself has certain surface activity and is a natural surfactant, it can be used as a soil remediation agent. Moreover, there are also relevant reports on the application of humic acid as a surfactant in the leaching remediation of contaminated soil. However, due to the complex molecular structure of humic acid itself, which is composed of skeletons such as aromatic rings and aliphatic chains, and is attached with various oxygen-containing functional groups such as carboxyl, phenolic hydroxyl and carbonyl. These functional groups endow humic acid with strong chemical reactivity, enabling it to form coordination bonds or chelates with metal ions. Since these functional groups are prone to form hydrogen bonds with water molecules, the heavy metal adsorption sites are competitively occupied by water molecules, thus reducing the adsorption efficiency. On the other hand, the hydrophobic region is composed of non-polar structures such as aromatic rings and hydrocarbon chains. Although it can adsorb some non-polar or weakly polar substances through hydrophobic interaction, it shows low affinity for most heavy metal ions. This unbalanced distribution of hydrophilic and hydrophobic regions limits the comprehensive performance of humic acid in adsorbing heavy metals.

[0004] Certain achievements have also been made in the modification of humic acid in the prior art. For example, in the research on the preparation and surface properties of a humic acid surfactant disclosed by Si Linjie et al. at Beijing University of Chemical Technology in June 2007, a modification method of fulvic acid and a modification method of humic acid are disclosed. The modification method of fulvic acid is to react fulvate with alkyl ammonium chloride salt to obtain a modified fulvic acid. However, due to the small molecular weight of fulvic acid and poor liposolubility, its remediation ability for heavy metals and persistent organic pollutants in contaminated soil is poor. It also discloses a modification method of humic acid, which is to carry out a sulfomethylation reaction of humic acid with sodium hydroxymethylsulfonate under alkaline conditions, and then react with ethyl chloroacetate to obtain a modified sulfomethylated humic acid with an ester group.

[0005] The method adopted in Patent CN102504278A includes adding humic acid into an alkaline solution and performing an alkylation reaction with a halogenated alkane to obtain alkylated humic acid; then adding the alkylated humic acid into a sulfomethylation reagent to perform a sulfomethylation reaction, and after the reaction ends, a humic acid modifier is obtained.

[0006] However, the above method only modifies humic acid, and the performance of its humic acid modifier in repairing heavy metal and organic pollution is poor. The heavy metal residue rate in the repaired soil still reaches more than 20%, and the repair effect cannot be achieved well. Summary of the Invention

[0007] Object of the Invention: The object of the present invention is to provide a preparation method of a modified humic acid, the obtained product and its application. Aiming at the problems of traditional humic acid in soil remediation, such as few active functional groups and easy rebound of the repair effect, chemical modification is carried out on ordinary humic acid to improve the adsorption efficiency of the modified humic acid for heavy metals and organic pollutants.

[0008] Technical Solution of the Present Invention:

[0009] To solve the above technical problems, the present invention provides the following technical solutions:

[0010] On the one hand, the present invention provides a preparation method of a modified humic acid, and the steps of the preparation method are as follows:

[0011] Step 1: Add humic acid into an aqueous solution, add an amination reagent, the alkylation reagent is piperazine with an amino group and a hydroxyl group, and then add concentrated sulfuric acid, and carry out a reaction under the conditions of heating and ultrasonic waves to obtain aminated humic acid;

[0012] Step 2: Add the aminated humic acid into an alkaline solution, adjust the pH value to 9-11, add a polybenzene compound, the chemical structural formula of the polybenzene compound includes a halogen atom and at least one benzene ring, carry out a reaction under heating conditions, and after the reaction ends, adjust the pH value of the product to 7-7.5 to obtain a modified humic acid.

[0013] In some embodiments, the structural formula of the amination reagent is as shown in Formula I:

[0014]

[0015] In some embodiments, the mass ratio of the humic acid to the amination reagent is 7-9:1.

[0016] In some embodiments, under the conditions of heating and ultrasonic waves, wherein the heating condition is heating at 70-100 °C; the ultrasonic condition is a frequency of 25-30 KHZ; the power of the ultrasonic wave is 200-500 KW.

[0017] In some embodiments, the alkaline solution is one or more combinations of sodium hydroxide solution, potassium hydroxide solution, potassium carbonate solution, or sodium carbonate solution.

[0018] In some embodiments, the chemical structural formula of the polybenzene compound includes one halogen atom and at least two benzene rings; preferably, the chemical structural formula of the polybenzene compound includes one halogen atom and two benzene rings; an appropriate number of benzene rings can balance the hydrophilicity and lipophilicity of the modified humic acid, avoid the situation where effective adsorption sites are competitively occupied by water molecules, and at the same time improve the lipophilic property and enhance the affinity of the modified humic acid for heavy metals with relatively weak polarity.

[0019] In some embodiments, the halogen atom is one of chlorine atom, bromine atom, or iodine atom.

[0020] Furthermore, the polybenzene compound is selected from one or more combinations of 4-chloro-2-benzylphenol (CAS 120-32-1), 4-(4-chlorobenzyl)-2-methylphenol (CAS 6279-21-6), 4-benzyl-2-chlorophenol (CAS 31089-49-3), 6-bromohexanoic acid triphenyl phosphate (CAS 27798-38-5).

[0021] In some embodiments, the heating condition is heating to 65°C - 85°C.

[0022] In some embodiments, the mass ratio of the aminated humic acid to the polybenzene compound is 2 - 5:1.

[0023] On the other hand, the present invention also provides a modified humic acid prepared by the preparation method of the above-mentioned modified humic acid.

[0024] On the other hand, the present invention also provides the application of the modified humic acid prepared by the preparation method of the above-mentioned modified humic acid in repairing contaminated soil.

[0025] In some embodiments, the contaminated soil is heavy metal contaminated soil and / or organic matter contaminated soil.

[0026] In some embodiments, the heavy metal is one or more combinations of copper, zinc, lead, and cadmium.

[0027] In some embodiments, the organic matter is methylene blue.

[0028] Beneficial effects:

[0029] The modified humic acid prepared by the preparation method of the modified humic acid provided by the present invention has high surface activity. By chemically grafting and modifying humic acid, the balance of its molecular structure is improved, enabling it to have good complexing, adsorption, and buffering capabilities. In particular, the remediation ability of humic acid in repairing heavy metal-polluted soil and organic matter-polluted soil is enhanced. It can effectively adsorb and complex heavy metals in polluted soil, and also effectively improve the dissolution and migration of organic matter, thereby achieving the remediation effect. Detailed implementation mode

[0030] The following will illustrate the present invention in combination with specific implementation examples. It should be noted that the following examples are examples of the present invention, only used to illustrate the present invention, and not used to limit the present invention. Without departing from the gist or scope of the present invention, other combinations and various improvements within the concept of the present invention can be made.

[0031] Unless otherwise specified, the chemical reagents used in the present invention are all ordinary commercially available analytical pure reagents.

[0032] The humic acid used in the examples of the present invention is Macklin H811077 humic acid (fulvic acid FA ≥ 90%).

[0033] Example 1

[0034] Step 1: Add 14 g to 50 ml of aqueous solution, add 2 g of 1-amino-4-(2-hydroxyethyl)piperazine, and then add 0.2 ml of concentrated sulfuric acid. Under the conditions of heating at 80 °C, ultrasonic frequency of 25 KHZ, and power of 300 KW, react for 4 h. After the reaction, filter to obtain aminated humic acid;

[0035] Step 2: Take 20 g of the aminated humic acid prepared in Step 1 and add it to 50 ml of sodium hydroxide aqueous solution. Adjust the pH value to 9, add 10 g of the polybenzene compound 4-chloro-2-benzylphenol, and react at 65 °C for 4 h. After the reaction, use dilute hydrochloric acid to adjust the pH value of the product to 7. Filter, collect the filtrate, distill it to dryness under reduced pressure, and place the obtained solid in a drying oven at 70 °C for vacuum drying to obtain modified humic acid 1.

[0036] Perform infrared spectrum analysis on modified humic acid 1. According to the infrared spectrum analysis, it can be obtained that: the peak at 3296 cm -1 is the absorption peak generated by the stretching vibration of amino N-H; the peak at 3060 cm -1 is the absorption peak generated by the stretching vibration of C-H on the aromatic ring, which is at a higher position than the C-H vibration peak of saturated hydrocarbons; the peak at 2846 cm -1 is the absorption peak generated by the C-H bond in piperazine; the peak at 1634 cm -1 is the absorption peak generated by the bending vibration of the N-H bond in piperazine; the peak at 3517 cm-1 The absorption peak is generated by the O-H stretching vibration of the hydroxyl group. From the above analysis, it can be obtained that the infrared spectrum data confirm the successful modification of humic acid.

[0037] Example 2

[0038] Basically the same as Example 1, the difference is that the polybenzene compound used in Step 2 is 4-(4-chlorobenzyl)-2-methylphenol, and modified humic acid 2 is prepared.

[0039] Example 3

[0040] Basically the same as Example 1, the difference is that the polybenzene compound used in Step 2 is triphenyl phosphate 6-bromohexanoate, and modified humic acid 3 is prepared.

[0041] Example 4

[0042] Basically the same as Example 1, the difference is that the added mass of the aminated humic acid used in Step 2 is 30 g, and modified humic acid 4 is prepared.

[0043] Example 5

[0044] Basically the same as Example 1, the difference is that the added mass of the aminated humic acid used in Step 2 is 50 g, and modified humic acid 5 is prepared.

[0045] Comparative Example 1

[0046] Basically the same as Example 1, the difference is that the polybenzene compound used in Step 2 is 3-chlorotoluene, and modified humic acid 6 is prepared.

[0047] Comparative Example 2

[0048] Basically the same as Example 1, the difference is that the polybenzene compound used in Step 2 is 4-methoxytriphenyl chloromethane, and modified humic acid 7 is prepared.

[0049] Comparative Example 3

[0050] Basically the same as Example 1, the difference is that the added mass of the aminated humic acid used in Step 2 is 0 g, and modified humic acid 8 is prepared.

[0051] Comparative Example 4

[0052] Basically the same as Example 1, the difference is that the added mass of the aminated humic acid used in Step 2 is 70 g, and modified humic acid 9 is prepared.

[0053] Comparative Example 5

[0054] Basically the same as Example 1, the difference is that Step 1 is omitted, and humic acid is used as the raw material for the grafting reaction in Step 2, and modified humic acid 10 is prepared.

[0055] Comparative Example 6

[0056] Humic acid from Macklin H811077 (hereinafter referred to as the original humic acid).

[0057] Performance test

[0058] 1. Prepare 50 ml of 50 ppm heavy metal ion aqueous solutions respectively. Take 25 mg of the products obtained in the examples and comparative examples as the repair agents and add them to the above solutions, then stir for 3 hours. Then filter to test the remaining heavy metal ions in the solution and calculate the removal rate. (Heavy metal ions include copper, zinc, lead, and cadmium).

[0059] 2. Prepare 50 ml of 50 ppm methylene blue aqueous solutions respectively. Take 25 mg of the products obtained in the examples and comparative examples as the repair agents and add them to the above solutions, then stir for 3 hours. Then filter to test the remaining methylene blue concentration in the solution and calculate the removal rate.

[0060] The detection results are as follows in the table:

[0061]

[0062] It can be seen from the comparison of the detection results of the examples and comparative examples that through the structural design of the modified humic acid, the present invention controls the number and proportion of grafted hydrophobic groups, so that the obtained modified humic acid has good lipophilicity and good hydrophilicity on the basis, improves the balance of its molecular structure, makes it have good complexing, adsorption and buffering capabilities, and reduces the recovery cost.

[0063] Through comparison, it can be seen that the modified humic acid 3 prepared by the preparation method provided in Example 3 has a good repair effect on soil polluted by various heavy metals and organic matters, indicating that it can effectively adsorb and complex heavy metals in the polluted soil, and can also effectively improve the dissolution and migration of organic matters, so as to achieve the repair effect. Compared with the prior art, the number of active functional groups in humic acid is increased, and at the same time, the hydrophilic and hydrophobic regions of the modified humic acid are more balanced, which helps to improve the repair efficiency of the modified humic acid on polluted soil.

[0064] The present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for preparing modified humic acid, characterized in that: The preparation method comprises the following steps: Step 1: adding humic acid to an aqueous solution, adding an amination agent, wherein the alkylation agent is piperazine having an amine group and a hydroxyl group, and then adding concentrated sulfuric acid, and reacting under heating and ultrasonic conditions to obtain aminated humic acid; Step 2: adding the aminated humic acid to an alkaline solution and adjusting the pH value to 9-11, adding a polyphenyl compound, wherein the chemical structure of the polyphenyl compound includes a halogen atom and at least one benzene ring, and reacting under heating conditions. After the reaction is completed, adjusting the pH value of the product to 7-7.5 to obtain modified humic acid.

2. The method for preparing modified humic acid according to claim 1, characterized in that: The structural formula of the amination reagent is shown in Formula I:

3. The method for preparing modified humic acid according to claim 1, characterized in that: The mass ratio of the humic acid to the aminating agent is 7-9:

1.

4. The method for preparing modified humic acid according to claim 1, characterized in that: The heating and ultrasonic conditions include heating at 70-100° C., ultrasonic conditions at a frequency of 25-30 KHZ, and ultrasonic power of 200-500 KW.

5. The method for preparing modified humic acid according to claim 1, characterized in that: The chemical structure of the polybenzene compound includes a halogen atom and at least two benzene rings.

6. The method for preparing modified humic acid according to claim 5, characterized in that: The halogen atom is one of a chlorine atom, a bromine atom or an iodine atom.

7. The method for preparing modified humic acid according to claim 5, characterized in that: The polyphenyl compound is selected from one or more combinations of 4-chloro-2-benzylphenol, 4-(4-chlorobenzyl)-2-methylphenol, 4-benzyl-2-chlorophenol, and 6-bromohexanoic acid triphenylphosphonic acid.

8. The method for preparing modified humic acid according to claim 5, characterized in that: The mass ratio of the aminated humic acid to the polyphenyl compound is 2-5:

1.

9. The modified humic acid prepared by the method for preparing modified humic acid according to any one of claims 1 to 8.

10. Use of the modified humic acid prepared by the preparation method of modified humic acid according to any one of claims 1 to 8 in remediating contaminated soil.

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