Coal-clay composite hydrogel and preparation method thereof

Abstract

This invention, belonging to the field of hydrogel technology, discloses a coal-clay composite hydrogel and its preparation method. The preparation method first disperses coal powder in water, then adds an emulsifier to obtain suspension A. A polyvinyl alcohol aqueous solution and a clay mineral are sequentially added to suspension A to obtain suspension B. A polymer, a crosslinking agent, and an initiator are sequentially added to suspension B to obtain suspension C. Suspension C is then placed in a nitrogen atmosphere and heated for polymerization to obtain the coal-clay composite hydrogel. The hydrogel of this invention has a high coal content, and the coal particles are stably bound within the hydrogel's three-dimensional network, resulting in a stable hydrogel structure with excellent strength and toughness.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogels, and in particular relates to a coal-clay composite hydrogel and a preparation method thereof. Background Art

[0002] Coal is an organic mineral rock with a macromolecular structure composed of the basic structural units aromatic rings and hydrogenated aromatic rings. It has rich pore structures and a large specific surface area. Due to its chemical composition and microstructure, coal particles have a good ability to remove organic pollutants from water and can be used to purify organically contaminated wastewater. The smaller the coal particle size, the stronger the adsorption performance. However, using fine coal particles as an adsorbent presents the problem of difficulty in solid-liquid separation. If coal particles are combined with polymers to form hydrogels, which can then be used for wastewater purification, the coal particles can be efficiently separated from the wastewater after purification.

[0003] Currently, there are few reports on the use of coal in the preparation of hydrogels. A search revealed the following literature. In their February 2014 paper, "Preparation and Swelling Properties of PAM / CMC / Coal Composite Hydrogels," Zhu Lin et al. prepared polyacrylamide / sodium carboxymethylcellulose / coal composite hydrogels by polymerization at room temperature using acrylamide as the monomer, ammonium persulfate as the initiator, tetramethylethylenediamine as the catalyst, N,N'-methylenebisacrylamide as the crosslinker, and sodium carboxymethylcellulose as the dispersant. However, due to the presence of numerous hydrophobic regions on the surface of coal particles, which cannot interact with polymers such as acrylamide and cellulose, the hydrogel's three-dimensional network cannot effectively bind the coal particles. This results in the coal particles destroying the hydrogel structure, resulting in poor mechanical properties and unfavorable for multiple recycling. Furthermore, the coal content in the gel is low, with the coal mass accounting for less than 20% of the monomer mass. Patent CN107814888B discloses a coal-based polymer hydrogel and its preparation method. To overcome the strength defects of coal-based hydrogel, water-soluble polymers are first extracted from coal using an alkali dissolution and acid precipitation method. The water-soluble polymers are then chemically modified and used to prepare the hydrogel. This method is cumbersome and does not directly use coal particles to prepare the hydrogel.

[0004] Therefore, how to directly use coal particles to prepare a composite hydrogel with stable structure, good mechanical properties and high coal content is a technical challenge currently faced. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies in the existing technology and provide a coal-clay composite hydrogel and a preparation method thereof. The hydrogel has a high coal content, and the coal particles can be stably bound in the three-dimensional network of the hydrogel, so that the hydrogel structure is stable and has excellent strength and toughness.

[0006] In order to solve the technical problem raised by the present invention, the present invention provides a method for preparing a coal-clay composite hydrogel, comprising the following steps:

[0007] 1) Adding coal powder to water and dispersing it evenly, then adding an emulsifier and stirring to dissolve the emulsifier to obtain a suspension A;

[0008] 2) adding a polyvinyl alcohol aqueous solution to suspension A, stirring and mixing, then adding clay mineral, and stirring again to obtain suspension B;

[0009] 3) Adding polymer to suspension B, stirring and dissolving, then adding crosslinking agent, stirring and dissolving, then adding initiator, and continuing stirring and dissolving to obtain suspension C;

[0010] 4) placing the suspension C in a nitrogen atmosphere, heating and then keeping the temperature to polymerize, and cooling to room temperature to obtain a coal-clay composite hydrogel.

[0011] In the above scheme, the mass parts of each raw material are: 200-400 parts of water, 20-50 parts of coal powder, 1-6 parts of emulsifier, 4-10 parts of polyvinyl alcohol aqueous solution, 5-40 parts of clay mineral, 30-55 parts of polymer, 1-10 parts of crosslinking agent, and 2-5 parts of initiator.

[0012] In the above solution, the particle size of the coal powder is less than 10 μm.

[0013] In the above solution, the emulsifier is one or more of dodecyltrimethylammonium bromide, sodium lauryl sulfate, and octadecyltrimethylammonium chloride.

[0014] In the above solution, the concentration of the polyvinyl alcohol aqueous solution is 80-120 g / L.

[0015] In the above solution, the clay mineral is one or more of montmorillonite, kaolinite, and attapulgite, and the particle size of the clay mineral is less than 10 μm.

[0016] In the above solution, the polymer is at least two of sodium carboxymethyl cellulose, chitosan, polyacrylamide, polyacrylic acid, sodium alginate, and sodium carboxymethyl starch.

[0017] In the above solution, the cross-linking agent is one or more of dicyclopentenyl acrylate, N,N'-methylenebisacrylamide, glycol dimethacrylate, and acrylic acid.

[0018] In the above scheme, the initiator is one of potassium persulfate and sodium persulfate.

[0019] In the above scheme, the heating temperature in step 4) is 50-80° C. and the insulation time is 4-10 hours.

[0020] The present invention also provides a coal-clay composite hydrogel, which is prepared by the above method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) The present invention utilizes the hydrophobic association between coal particles and emulsifier molecules, as well as the interaction between the emulsifier molecules and the polar groups of the hydrogel polymer network, to stably bind the coal particles in the three-dimensional hydrogel network. At the same time, clay mineral fine particles are used as active sites to cross-link with the hydrogel polymer to enhance the mechanical properties of the hydrogel. As a result, the prepared hydrogel has a high coal content, a stable structure, and excellent strength and toughness.

[0023] 2) The present invention directly utilizes coal particles to prepare hydrogel, avoiding the conventional process of oxidizing the surface of the coal particles. The preparation process is simple and is conducive to promotion and application. DETAILED DESCRIPTION

[0024] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0025] Example 1

[0026] A method for preparing a coal-clay composite hydrogel comprises the following steps:

[0027] 1) adding 38 parts of coal powder with a particle size of less than 10 μm to 280 parts of water, and mechanically stirring to disperse it uniformly, and then adding 1.2 parts of sodium lauryl sulfate, and mechanically stirring to disperse and dissolve it, to obtain suspension A;

[0028] 2) adding 5 parts of a 120 g / L aqueous solution of polyvinyl alcohol to suspension A, stirring and mixing uniformly, then adding 8 parts of montmorillonite with a particle size of less than 10 μm, stirring and mixing again to obtain suspension B;

[0029] 3) Add 10 parts of sodium carboxymethyl cellulose, 10 parts of polyacrylamide, and 10 parts of polyacrylic acid to suspension B, stir until completely dissolved, add 6 parts of N,N'-methylenebisacrylamide, stir until dissolved, and then add 4 parts of sodium persulfate, stir until dissolved, to obtain suspension C;

[0030] 4) The suspension C was placed in a nitrogen atmosphere, heated to 60° C. for 6 h for polymerization, and cooled to room temperature to obtain a coal-clay composite hydrogel.

[0031] Example 2

[0032] A method for preparing a coal-clay composite hydrogel comprises the following steps:

[0033] 1) adding 20 parts of coal powder with a particle size of less than 10 μm to 240 parts of water, and mechanically stirring to disperse uniformly, then adding 0.5 parts of sodium lauryl sulfate and 0.5 parts of dodecyltrimethylammonium bromide, and mechanically stirring to disperse and dissolve them, to obtain suspension A;

[0034] 2) adding 4 parts of a 100 g / L aqueous solution of polyvinyl alcohol to suspension A, stirring and mixing uniformly, then adding 2 parts of montmorillonite with a particle size of less than 10 μm and 3 parts of kaolinite with a particle size of less than 10 μm, stirring and mixing again to obtain suspension B;

[0035] 3) Add 10 parts of sodium carboxymethyl cellulose, 10 parts of polyacrylamide, 10 parts of polyacrylic acid, 5 parts of sodium alginate, and 5 parts of sodium carboxymethyl starch to Suspension B, stir until completely dissolved, then add 2 parts of dicyclopentenyl acrylate and 2 parts of acrylic acid, stir until dissolved, and then add 2.5 parts of potassium persulfate and stir until dissolved to obtain Suspension C;

[0036] 4) The suspension C was placed in a nitrogen atmosphere, heated to 70° C. for 4 h for polymerization, and cooled to room temperature to obtain a coal-clay composite hydrogel.

[0037] Example 3

[0038] A method for preparing a coal-clay composite hydrogel comprises the following steps:

[0039] 1) adding 50 parts of coal powder with a particle size of less than 10 μm to 380 parts of water, and mechanically stirring to disperse uniformly, then adding 2 parts of dodecyltrimethylammonium bromide and 3 parts of octadecyltrimethylammonium chloride, and mechanically stirring to disperse and dissolve them, to obtain suspension A;

[0040] 2) adding 8 parts of a 90 g / L aqueous solution of polyvinyl alcohol to suspension A, stirring and mixing uniformly, then adding 10 parts of kaolinite with a particle size of less than 10 μm and 10 parts of attapulgite with a particle size of less than 10 μm, stirring and mixing again to obtain suspension B;

[0041] 3) Add 15 parts of polyacrylamide, 15 parts of polyacrylic acid, 5 parts of sodium alginate, and 15 parts of sodium carboxymethyl starch to suspension B, stir until completely dissolved, then add 2 parts of acrylic acid, 3 parts of biscyclopentenyl acrylate, and 3 parts of N,N'-methylenebisacrylamide, stir until dissolved, and then add 6 parts of potassium persulfate and stir until dissolved to obtain suspension C;

[0042] 4) The suspension C was placed in a nitrogen atmosphere, heated to 75° C. for 3 h for polymerization, and cooled to room temperature to obtain a coal-clay composite hydrogel.

[0043] Example 4

[0044] A method for preparing a coal-clay composite hydrogel comprises the following steps:

[0045] 1) adding 40 parts of coal powder with a particle size of less than 10 μm to 340 parts of water, and mechanically stirring to disperse uniformly, then adding 2 parts of dodecyltrimethylammonium bromide, 1 part of octadecyltrimethylammonium chloride and 1 part of sodium lauryl sulfate, and mechanically stirring to disperse and dissolve them to obtain suspension A;

[0046] 2) adding 9 parts of an 80 g / L aqueous solution of polyvinyl alcohol to suspension A, stirring and mixing uniformly, then adding 15 parts of montmorillonite with a particle size of less than 10 μm and 15 parts of attapulgite with a particle size of less than 10 μm, stirring and mixing again to obtain suspension B;

[0047] 3) adding 15 parts of sodium carboxymethyl cellulose, 5 parts of sodium alginate, 10 parts of sodium carboxymethyl starch, and 20 parts of polyacrylamide to suspension B, stirring until dissolved, adding 3 parts of acrylic acid and 2 parts of dicyclopentenyl acrylate, stirring until dissolved, and then adding 4.5 parts of potassium persulfate, stirring until dissolved, to obtain suspension C;

[0048] 4) The suspension C was placed in a nitrogen atmosphere, heated to 60° C. for 8 h for polymerization, and cooled to room temperature to obtain a coal-clay composite hydrogel.

[0049] Comparative Example 1

[0050] The only difference between Comparative Example 1 and Example 1 is that no emulsifier and clay mineral particles are added.

[0051] Comparative Example 2

[0052] The only difference between Comparative Example 2 and Example 1 is that no clay mineral is added.

[0053] The tensile strength and tensile strain of the hydrogels prepared in Examples 1-4 and Comparative Examples 1-2 were measured. The mechanical properties of the hydrogels were measured by cutting them into samples with a width of 5 mm, a thickness of 2 mm, and a length of 75 mm at equilibrium swelling. The results are shown in Table 1.

[0054] Table 1

[0055]

[0056] It can be seen from the data of Example 1 and Comparative Example 1 that the tensile strength and tensile strain of the hydrogel prepared without adding emulsifiers and clay minerals are very low; it can be seen from the data of Comparative Examples 1 and 2 that after adding emulsifiers, the tensile strength of the hydrogel is increased from 0.82kPa to 1.85kPa, and the tensile strain is correspondingly increased from 80% to 170%. This is because the coal particles can be stably bound in the three-dimensional hydrogel network by utilizing the hydrophobic association between the coal particles and the emulsifier molecules, and the effect of the polar groups of the emulsifier molecules and the hydrogel polymer network, thereby significantly enhancing the hydrogel. stability and mechanical properties; it can be seen from the data of Example 1 and Comparative Example 2 that the tensile strength of the hydrogel prepared by adding the emulsifier and the clay mineral at the same time is increased from 1.85 kPa to 3.93 kPa compared with the hydrogel added with only the emulsifier, indicating that the clay mineral can further enhance the strength of the hydrogel, while the tensile strain is reduced from 170% to 133%. This is because the clay has a strong effect on the polymer polar groups and increases the cross-linking density, thereby leading to an increase in tensile strength and a decrease in tensile strain. However, from the comprehensive performance point of view, the hydrogel prepared by adding the emulsifier and the clay mineral at the same time has the best performance.

[0057] The above embodiments are merely examples for clarification and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications may be made based on the above descriptions. It is not necessary and impossible to enumerate all implementation methods here, and any obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing a coal-clay composite hydrogel, characterized in that: The following steps are involved: 1) adding pulverized coal to water and dispersing it uniformly, then adding an emulsifier and stirring to dissolve the emulsifier to obtain a suspension A; the emulsifier is one or more of dodecyltrimethylammonium bromide, sodium lauryl sulfate, and octadecyltrimethylammonium chloride; 2) Add polyvinyl alcohol aqueous solution to suspension A, stir and mix, then add clay mineral, and stir again to obtain suspension B; 3) adding a polymer to suspension B, stirring and dissolving, then adding a crosslinking agent, stirring and dissolving, then adding an initiator, and continuing to stir and dissolve to obtain suspension C; the polymer is at least two of sodium carboxymethyl cellulose, chitosan, polyacrylamide, polyacrylic acid, sodium alginate, and sodium carboxymethyl starch; 4) The suspension C is placed in a nitrogen atmosphere, heated and then kept warm for polymerization, and then cooled to room temperature to obtain a coal-clay composite hydrogel.

2. The method for preparing the coal-clay composite hydrogel according to claim 1, wherein: The mass proportions of the raw materials are: 200-400 parts of water, 20-50 parts of coal powder, 1-6 parts of emulsifier, 4-10 parts of polyvinyl alcohol aqueous solution, 5-40 parts of clay mineral, 30-55 parts of polymer, 1-10 parts of cross-linking agent, and 2-5 parts of initiator; the concentration of the polyvinyl alcohol aqueous solution is 80-120 g / L.

3. The method for preparing the coal-clay composite hydrogel according to claim 1, wherein: The clay mineral is one or more of montmorillonite, kaolinite and attapulgite.

4. The method for preparing the coal-clay composite hydrogel according to claim 1, wherein: The particle size of the coal powder and clay mineral is less than 10 μm.

5. The method for preparing the coal-clay composite hydrogel according to claim 1, wherein: The cross-linking agent is one or more of dicyclopentenyl acrylate, N,N'-methylenebisacrylamide, glycol dimethacrylate, and acrylic acid.

6. The method for preparing the coal-clay composite hydrogel according to claim 1, wherein: The initiator is one of potassium persulfate and sodium persulfate.

7. The method for preparing the coal-clay composite hydrogel according to claim 1, wherein: The heating temperature in step 4) is 50-80°C and the holding time is 4-10 hours.

8. A coal-clay composite hydrogel prepared by the method according to any one of claims 1 to 7.

Images