Modified activated carbon as well as preparation method and application thereof

Abstract

The invention discloses modified activated carbon as well as a preparation method and application thereof. The preparation method of the modified activated carbon comprises the following steps: reacting oxidized activated carbon with a first solution to obtain the modified activated carbon, the first solution comprises dopamine and tannic acid; the mass ratio of the activated carbon to the dopamine is 100: (0.2-0.6); the pH value of the first solution is 7.5 to 8.5. The modified activated carbon provided by the invention is high in hydrophilicity, and the prepared filter element is high in adsorption capacity and low in water resistance.

Description

Technical Field

[0001] The present invention specifically relates to modified activated carbon, its preparation method and application. Background Art

[0002] At present, household water purifiers are developing towards the direction of small volume, large flow rate and high performance. How to design an excellent water purification system in a limited volume has become a major challenge in the industry development.

[0003] For activated carbon filters used for water purification, the form has gradually changed from granular activated carbon to sintered carbon rods. The carbon rod filter is sintered from carbon powder and binder ultra-high molecular weight polyethylene under high temperature and high pressure. Due to the high packing density of carbon powder, efficient removal of organic substances in water can be achieved within a limited volume. However, with the increase of packing density, the resistance of the carbon rod filter to fluid also increases, resulting in the loss of the flow rate of the filtration system; for a filtration system with the same flow rate, a higher performance carbon rod filter requires a larger pump or membrane module to achieve the ideal flow rate, resulting in waste of cost.

[0004] Therefore, obtaining an activated carbon filter with low water resistance and large flow rate is of great significance to the water purification field. Summary of the Invention

[0005] The main purpose of the present invention is to overcome the defect of large water resistance generated by the activated carbon filter in the prior art when ensuring the adsorption capacity, and provides modified activated carbon, its preparation method and application. The modified activated carbon provided by the present invention has strong hydrophilicity, the prepared filter has strong adsorption capacity and low water resistance.

[0006] The present invention provides a preparation method of modified activated carbon, which comprises the following steps:

[0007] Reacting the oxidized activated carbon with a first solution to obtain the modified activated carbon; the first solution comprises dopamine and tannic acid; the mass ratio of the activated carbon to the dopamine is 100:(0.2-0.6); the pH of the first solution is 7.5-8.5.

[0008] In the present invention, the source of the activated carbon (AC) can be conventional in the art, preferably coconut shell activated carbon.

[0009] In the present invention, the iodine value of the activated carbon can be 1000mg / g-1500mg / g, such as 1050mg / g. The iodine value is a measure of the activity level and is a basic parameter representing the performance of activated carbon. The higher the iodine value, the higher the activation degree and the stronger the adsorption capacity.

[0010] In the present invention, the ash content of the activated carbon can be 8%-15%, such as 8%.

[0011] In the present invention, the strength of the activated carbon can be 90%-98%, such as 98%.

[0012] In the present invention, the moisture content of the activated carbon can be 3%-8%, such as 3%.

[0013] In the present invention, the size of the activated carbon can be 20-200 mesh, such as 100 mesh.

[0014] In the present invention, the oxidized activated carbon can be obtained through commercial purchase or by conventional preparation methods in the art. The preparation method of the oxidized activated carbon can be obtained by an oxidation reaction of the activated carbon with an oxidant.

[0015] Among them, the oxidation reaction can be carried out in an aqueous solution.

[0016] Among them, in the raw material system of the oxidation reaction, the concentration of the oxidant can be 1%-10%, such as 1%, 5%, 8% or 10%.

[0017] Among them, the time of the oxidation reaction can be 20 min-120 min, such as 20 min, 40 min, 60 min or 120 min.

[0018] Among them, the oxidant can be a conventionally used oxidizing substance in the art, preferably a colorless oxidant, such as hydrogen peroxide. The function of the oxidant is to oxidize the surface of the activated carbon to generate a large number of carboxyl groups.

[0019] Among them, before the oxidation reaction, the activated carbon is also pretreated. The pretreatment is to wash and filter the raw materials in sequence, and then dry them. The pretreatment is to wash away the scum and impurities on the surface of the raw materials. The drying time is preferably 6 h-24 h, such as 12 h; the drying temperature is preferably 100-150 °C, such as 120 °C.

[0020] In the present invention, the mass ratio of the dopamine to the tannic acid can be 1:(0.25-3.75), such as 1:0.25, 1:1.25, 1:2.5 or 1:3.75.

[0021] In the present invention, the mass ratio of the activated carbon to the dopamine is preferably 100:(0.4-0.6), such as 100:0.4.

[0022] In the present invention, the solvent of the first solution can be a Tris-HCl buffer solution. The pH of the Tris-HCl buffer solution is preferably 7.5-8.5, such as 7.5, 8.0, 8.2 or 8.5.

[0023] In the present invention, the pH of the first solution is preferably 7.5 - 8.2, such as 7.5, 8.0 or 8.2. If the pH of the first solution is too high or too low, it will affect the polymerization process of dopamine and tannic acid, resulting in the activated carbon being unable to obtain hydrophilic groups, affecting its hydrophilicity, and thus affecting the flow rate.

[0024] In the present invention, the first solution can be prepared by mixing a dopamine solution and a tannic acid solution; the concentration of the dopamine solution is preferably 0.1% - 0.9%, such as 0.4%; the concentration of the tannic acid solution is preferably 0.1% - 1.5%, such as 0.1%, 0.5%, 1% or 1.5%. The phenolic hydroxyl groups and oxidized quinone groups in tannic acid can undergo a cross-linking reaction with the amino groups in dopamine. Dopamine and tannic acid jointly modify the activated carbon, which can significantly improve the hydrophilicity of the activated carbon, thereby improving the water resistance of the filter element.

[0025] In the present invention, the reaction time can be 2h - 8h, such as 2h, 4h, 6h or 8h.

[0026] In the present invention, the reaction temperature can be 20 - 40°C, such as 20°C, 25°C or 30°C.

[0027] The present invention also provides modified activated carbon prepared by the preparation method described above.

[0028] In the present invention, the iodine value of the modified activated carbon is preferably 1000mg / g - 1500mg / g, such as 1050mg / g.

[0029] The present invention also provides a carbon rod filter element, which comprises the modified activated carbon described above.

[0030] The present invention also provides the application of the modified activated carbon or carbon rod filter element described above in the field of water treatment.

[0031] On the basis of conforming to the common knowledge in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain various preferred examples of the present invention.

[0032] The reagents and raw materials used in the present invention are all commercially available.

[0033] The positive and progressive effects of the present invention are as follows:

[0034] The modified activated carbon provided by the present invention has good hydrophilicity and small water resistance. When used as a carbon rod filter element, it can provide a high flow rate while maintaining good adsorption capacity, which is beneficial to cost savings.

[0035] In some specific embodiments, the water contact angle of the modified activated carbon is less than 35°, the flow rate is greater than 4.1L / min@0.1bar, and it is equivalent to the iodine value of the unmodified activated carbon. Detailed implementation manners

[0036] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions noted in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0037] Example 1

[0038] (1) Pretreatment: Activated carbon powder with a particle size of 80 - 200 mesh is rinsed with distilled water multiple times until the surface scum and impurities are washed away; suction filtration is carried out, and it is dried at 120 °C for 12 h, then bagged and placed in a desiccator for standby;

[0039] The activated carbon powder selected is coconut shell activated carbon, with an iodine value of 1050 mg / g, an ash content of 8%, a strength of 98%, a moisture content of 3%, and a mesh number of 100 mesh;

[0040] (2) Oxidation modification: The activated carbon powder obtained in step (1) is soaked in a hydrogen peroxide solution to oxidize a large number of carboxyl groups on the surface of the activated carbon to obtain oxidized activated carbon;

[0041] (3) Prepare dopamine solution and tannic acid solution respectively with Tris-HCl buffer solution, then mix the two, and place the oxidized activated carbon prepared in step (2) in the mixed solution and react at room temperature for a period of time;

[0042] (4) The modified activated carbon prepared in step (3) is washed 3 - 5 times with distilled water, suction filtered, and dried at 120 °C for 12 h.

[0043] The material dosages and process parameters of Examples 1 - 5 and Comparative Examples 1 - 9 are shown in Table 1.

[0044] The preparation method of Comparative Example 5 is to first react activated carbon with a mixed solution of dopamine and tannic acid, and then carry out oxidation modification.

[0045] In Comparative Example 6, tannic acid is replaced with gallic acid.

[0046] Table 1

[0047]

[0048]

[0049] Effect examples

[0050] The modified activated carbons prepared in Examples 1 - 5 and Comparative Examples 1 - 9 are characterized, and the test results are shown in Table 2.

[0051] (1) Surface contact angle test

[0052] Surface contact angle measurement is an important means to characterize the surface hydrophilicity / hydrophobicity of activated carbon, which is equivalent to an analysis of surface functional groups. Different materials were tested and characterized at room temperature by a contact angle tester. All contact angle tests were repeated three times, and the data with an error of no more than 5% were taken, and then the average value was obtained as the final result.

[0053] (2) Flow rate

[0054] The modified activated carbon prepared in the examples and comparative examples was loaded into the filter element, the inlet dynamic pressure was adjusted to 0.1 MPa, and a stopwatch and a flow meter were used to measure the water output per unit time.

[0055] (3) Iodine value

[0056] The iodine adsorption value was measured according to the test method of GB-T 12496.8-1999 for wood-based activated carbon.

[0057] Table 2

[0058]

[0059]

[0060] The water contact angle of the modified activated carbon provided by the present invention is less than 35°, the flow rate is greater than 4.1 L / min@0.1 bar, and the iodine value is equivalent to that of the unmodified activated carbon. It can have high purification ability and low water resistance at the same time, ensuring the treatment efficiency.

[0061] In Comparative Example 1, the activated carbon was not oxidized, and the pH value of the first solution was less than that of the present invention. According to the data in Table 2, it can be seen that its surface contact angle is much larger than that of the present invention, which means that its hydrophilicity is worse than that of the present invention. When used as a carbon rod filter element, its flow rate is lower, and compared with the raw material, the iodine value also decreases, indicating that the purification ability is reduced.

[0062] The pH values of Comparative Example 2 and Comparative Example 9 are greater than that of the present invention, and their contact angles, flow rates and iodine values are all worse than those of the present invention. Especially the iodine value decreases significantly. This may be because too acidic or too alkaline conditions will affect the polymerization of dopamine and tannic acid, resulting in the activated carbon being unable to obtain hydrophilic groups, affecting its hydrophilicity, and thus affecting the flow rate and adsorption capacity.

[0063] In Comparative Example 3 and Comparative Example 4, dopamine and tannic acid were not added respectively, and their effects were worse than those when both were added at the same time. This may be because the phenolic hydroxyl group and oxidized quinone group of tannic acid can cross-link with the amino group in the precursor of polydopamine. Dopamine and tannic acid jointly modify the activated carbon, which can greatly improve the hydrophilicity of the activated carbon, thus improving the water resistance of the filter element.

[0064] In Comparative Example 5, the activated carbon first reacts with dopamine and tannic acid and then undergoes oxidation treatment. The obtained effect is worse than that of the present invention. This may be because the activated carbon without oxidation treatment has fewer active functional groups on its surface and cannot combine with hydrophilic functional groups, thus affecting its hydrophilicity and flow rate.

[0065] In Comparative Example 6, gallic acid is used to replace tannic acid, and the effect is worse than that of the present invention. This may be because gallic acid has a small molecular weight and a short molecular chain and cannot effectively combine with activated carbon.

[0066] In Comparative Example 7, the ratio of activated carbon to dopamine is greater than that of the present invention. It can be seen that its hydrophilicity, flow rate, and iodine value are all worse than those of the present invention. This may be because the excessive amount of dopamine leads to the complete reaction of the active sites on the surface of the activated carbon and occupies some pores of the activated carbon, so the effect is poor.

[0067] In Comparative Example 8, no oxidation treatment is carried out. It can be seen that its contact angle is very large, and the flow rate and iodine value are both lower than those of the present invention. This may be because the activated carbon without oxidation treatment has fewer active functional groups on its surface and cannot combine with hydrophilic functional groups, thus affecting its effect.

[0068] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

Claims

1. A preparation method of modified activated carbon, characterized in that, It includes the following steps: React the oxidized activated carbon with the first solution to obtain the modified activated carbon; the first solution includes dopamine and tannic acid; the mass ratio of the activated carbon to the dopamine is 100:(0.2 - 0.6); the pH of the first solution is 7.5 - 8.

5.

2. The preparation method of the modified activated carbon according to claim 1, wherein, The oxidized activated carbon is obtained by the oxidation reaction of the activated carbon with an oxidant; the oxidation reaction is preferably carried out in an aqueous solution; in the raw material system of the oxidation reaction, the concentration of the oxidant is preferably 1% - 10%, such as 1%, 5%, 8% or 10%; And / or, the mass ratio of the activated carbon to the dopamine is 100:(0.4 - 0.6), such as 100:0.

4.

3. The preparation method of the modified activated carbon according to claim 1, characterized in that, The mass ratio of the dopamine to the tannic acid is 1:(0.25 - 3.75), such as 1:0.25, 1:1.25, 1:2.5 or 1:3.

75.

4. The preparation method of the modified activated carbon according to claim 1, wherein, The pH of the first solution is 7.5 - 8.2, such as 7.5, 8.0 or 8.2; And / or, the solvent of the first solution is a Tris-HCl buffer solution, and the pH of the Tris-HCl buffer solution is preferably 7.5 - 8.5, such as 7.5, 8.0, 8.2 or 8.5; And / or, the first solution is prepared by mixing a dopamine solution and a tannic acid solution; wherein the concentration of the dopamine solution is preferably 0.1% - 0.9%, such as 0.4%; the concentration of the tannic acid solution is preferably 0.1% - 1.5%, such as 0.1%, 0.5%, 1% or 1.5%.

5. The preparation method of the modified activated carbon according to claim 1, characterized in that, The reaction time is 2h - 8h, such as 2h, 4h, 6h or 8h; And / or, the reaction temperature is 20 - 40°C, such as 20°C, 25°C or 30°C.

6. The preparation method of the modified activated carbon according to claim 2, wherein, The oxidant is a colorless oxidant, such as hydrogen peroxide; And / or, the oxidation reaction time is 20min - 120min, such as 20min, 40min, 60min or 120min; And / or, before the oxidation reaction, the activated carbon is pretreated, and the pretreatment is to rinse and filter the raw materials in sequence, and then dry; the drying time is preferably 6h - 24h, such as 12h; the drying temperature is preferably 100 - 150°C, such as 120°C.

7. The preparation method of the modified activated carbon according to claim 6, characterized in that, The raw material of the activated carbon is coconut shell activated carbon; And / or, the iodine value of the activated carbon is 1050mg / g - 1500mg / g, such as 1050mg / g; And / or, the ash content of the activated carbon is 8% - 15%, such as 8%; And / or, the strength of the activated carbon is 90% - 98%, such as 98%; And / or, the moisture content of the activated carbon is 3% - 8%, such as 3%; And / or, the size of the activated carbon is 20 - 200 mesh, such as 100 mesh.

8. A modified activated carbon prepared by the preparation method according to any one of claims 1 - 7; the iodine value of the modified activated carbon is preferably 1000mg / g - 1500mg / g, such as 1050mg / g.

9. A carbon rod filter element, characterized in that, It comprises the modified activated carbon as described in claim 8.

10. Application of the modified activated carbon as described in claim 8 or the carbon rod filter element as described in claim 9 in the field of water treatment.

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