Nitrogen-containing activated carbon, carbon rod, preparation method of carbon rod and water purifier

Abstract

The invention provides nitrogen-containing activated carbon, a carbon rod, a preparation method of the carbon rod and a water purifier, and the preparation method of the nitrogen-containing activated carbon comprises the following steps: crushing a coconut shell raw material, cleaning the crushed coconut shell raw material with pure water, drying the cleaned coconut shell raw material, and carbonizing the dried coconut shell raw material under the protection of inert gas to obtain a carbonized material; crushing the carbonized material to a predetermined mesh number, and screening out an over-coarse or over-fine carbonized material by using a screen to obtain a coconut shell carbonized material; placing the coconut shell carbonized material in a rotary activation furnace, and activating by using water vapor as an activation gas to obtain microporous coconut shell activated carbon; the preparation method comprises the following steps: cleaning and drying microporous coconut shell activated carbon, crushing and sieving to 80-325 meshes; and placing the microporous coconut shell activated carbon in a rotary activation furnace, raising the temperature to 500-1000 DEG C under the protection of inert gas, and activating by using a mixed gas of ammonia gas and ammonia gas as an activation gas to obtain the nitrogen-containing activated carbon. By optimizing the pore structure and surface chemical properties of the activated carbon, the adsorption capacity of the activated carbon to trichloromethane and the catalytic capacity of the activated carbon to chloramine are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of water purification, and particularly to a nitrogen-containing activated carbon, a carbon rod, a preparation method thereof, and a water purifier. Background Art

[0002] Most of people's diseases are related to bacterial infections, and most bacterial infections are transmitted through drinking water. Therefore, to avoid the occurrence and prevalence of water-borne diseases and ensure human health, domestic drinking water must be disinfected before it can be consumed.

[0003] Currently, public water supply systems still mainly use chlorine for tap water disinfection, but in some areas, chloramine (NH2Cl) has begun to be used instead of chlorine. As a result, consumers are increasingly paying attention to the function of water purifiers in removing chloramine.

[0004] Generally speaking, the disinfection by-products in drinking water mainly come from the reaction of chlorine used for disinfection with humic acid in water. Among them, trihalomethanes, as carcinogenic substances, have also attracted great attention from market consumers. Trihalomethanes are composed of chloroform, bromodichloromethane, dibromochloromethane, and bromoform. Among them, chloroform is usually used as the main means to evaluate the filtration of disinfection by-products by household water purifiers due to its high proportion in total disinfection by-products and small molecular weight.

[0005] Due to its high specific surface area and developed pore structure, activated carbon is beneficial to the adsorption and catalysis of organic substances in water. Moreover, its raw materials are cheap and easily available as renewable resources. After using an adhesive to bond activated carbon into a carbon rod, it has a stable filtration efficiency and is widely used in household water purifiers. However, currently, commercially available activated carbon is difficult to balance the adsorption capacity for chloroform and the catalytic capacity for chloramine. Some commercially available modified carbon powders have a low bulk density, resulting in difficult use. Summary of the Invention

[0006] In view of the technical problem that existing activated carbon in the field of water purification is difficult to balance the adsorption capacity for chloroform and the catalytic capacity for chloramine, the present invention provides a nitrogen-containing activated carbon, a carbon rod, a preparation method thereof, and a water purifier to improve the above problems.

[0007] A preparation method of a nitrogen-containing activated carbon, comprising: S1, crushing coconut shell raw materials, washing them with pure water and then drying them, and carbonizing them under the protection of an inert gas to obtain a carbonized material; S2, putting the carbonized material into a coal crusher to crush it to a predetermined mesh number, and using a sieve to screen out the too thick or too fine carbonized material to obtain a coconut shell carbonized material; S3, placing the coconut shell carbonized material in a rotary activation furnace, and using water vapor as an activation gas for activation to obtain a microporous coconut shell activated carbon; S4. After cleaning and drying the microporous coconut shell activated carbon, it is crushed and sieved to 80 - 325 mesh. S5. Place the microporous coconut shell activated carbon in a rotary activation furnace. After using an inert gas to protect and heat up to 500 - 1000 °C, use a mixed gas of ammonia and nitrogen as the activation gas for activation to obtain nitrogen - containing activated carbon.

[0008] Preferably, in step S1, the drying is carried out at 80 °C for 24 h, and the carbonization temperature is 450 °C.

[0009] Preferably, in step S2, the predetermined mesh number is less than 80 mesh, preferably 20 mesh.

[0010] Preferably, in step S3, the water vapor flow rate is 30 ml / min, the activation time is 2 hours, and the activation temperature is 800 °C; the average pore diameter of the microporous coconut shell activated carbon is 1.6 - 2.0 nm, and the total pore volume is 0.45 - 0.50 cm 3 / g, where: the micropore volume is 0.36 - 0.40 cm 3 / g.

[0011] Preferably, in step S4, During cleaning: use 0.1M HCl solution to clean twice to remove inorganic salts and ash; During rinsing, use distilled water to rinse until the pH is in the range of 6.5 - 7; During drying, dry at 105 °C for 10 h.

[0012] Preferably, after step S4 and before step S5, it further includes: Place the sieved microporous coconut shell activated carbon in a hydrogen peroxide oxidant, stir, and then dry to obtain hydrogen peroxide - modified microporous coconut shell activated carbon; Among them, the concentration of the hydrogen peroxide oxidant is 30%; the stirring condition is stirring at 500 r / min for 12 h; the drying condition is drying at 50 °C for 24 h; In step S5, the inert gas is nitrogen; the ammonia flow rate is 80 ml / min, the nitrogen flow rate is 100 ml / min, and the activation time is 1 hour The embodiment of the present invention also provides a nitrogen - containing activated carbon prepared by the above - mentioned preparation method.

[0013] The embodiment of the present invention also provides a carbon rod for removing chloramine and chloroform in water. By weight: It includes 70 parts of the nitrogen - containing activated carbon as described above and 30 parts of ultra - high - molecular - weight polyethylene binder.

[0014] The embodiment of the present invention also provides a preparation method of the carbon rod as described above, which includes: Weigh the nitrogen-containing activated carbon and the binder respectively according to a weight ratio of 7:3, and then mix them using a two-dimensional mixer to obtain a mixed material. Extrude and cut the mixed material to obtain a carbon rod capable of removing chloramine and chloroform. Among them, during the extrusion process, the extrusion includes three temperature stages. The temperature of the first stage is 120-160°C, the temperature of the second stage is 180-240°C, and the temperature of the third stage is 170-235°C. During the extrusion process, the rotation speed of the screw is 200-400 r / min.

[0015] An embodiment of the present invention also provides a water purifier, which includes the carbon rod as described above.

[0016] By optimizing the pore structure and surface chemical properties of the activated carbon, the embodiment of the present invention significantly improves its adsorption capacity for chloroform and catalytic capacity for chloramine. In addition, the preparation method of the embodiment of the present invention is simple and safe, suitable for large-scale production, and has good economic value and application prospects. Detailed Embodiments

[0017] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] Example 1 The preparation steps of the carbon rod for removing chloramine and chloroform in water purification in this embodiment are as follows: Step 1. Preparation of microporous activated carbon: First, crush the coconut shell raw material, thoroughly wash it with pure water, dry it at 80°C for 24 hours, and carbonize it under the protection of inert gas to obtain a carbonized material. The carbonization temperature is 450°C.

[0019] Then, put the obtained carbonized material into a coal crusher and crush it to 20 mesh, and use a stainless steel sieve to screen out the too thick or too fine carbonized material to obtain coconut shell carbonized material.

[0020] Next, place 500 g of the sieved coconut shell carbonized material in a rotary activation furnace, use water vapor as the activation gas, the water vapor flow rate is 30 ml / min, the activation time is 2 hours, and the activation temperature is 800°C to obtain microporous activated carbon.

[0021] Finally, take the activated microporous activated carbon and wash it thoroughly twice with 0.1M HCl solution to remove inorganic salts and ash. Then rinse it with distilled water until the pH is in the range of 6.5 - 7. Dry it at 105°C for 10h, crush it with a charcoal crusher and sieve it through 80 - 325 mesh, and then store it in a sealed plastic bag.

[0022] Step 2: Preparation of nitrogen-containing activated carbon First, take 200g of the microporous activated carbon obtained above and place it in 500ml of 30% hydrogen peroxide oxidant, stir at 500r / min for 12h. Dry it at 50°C for 24h and store it in a sealed plastic bag.

[0023] Then, put 200g of the activated carbon modified by hydrogen peroxide into a rotary activation furnace. After heating to 500°C under nitrogen protection, use ammonia gas as the activation gas, the ammonia gas flow rate is 80ml / min, the nitrogen gas flow rate is 100ml / min, and the activation time is 1 hour to obtain nitrogen-containing activated carbon.

[0024] Step 3: Preparation of carbon rods Next, by weight, mix 70 parts of the nitrogen-containing activated carbon obtained in step 6 and 30 parts of ultra-high molecular weight polyethylene binder using a two-dimensional mixer for 60min, and extrude and cut the mixed material. A carbon rod for removing chloramine and chloroform with an outer diameter, inner diameter, and length of 38*10*110mm is prepared.

[0025] Among them, during the extrusion molding process, the extrusion includes three temperature sections. The first section temperature is 120 - 160°C, the second section temperature is 180 - 240°C, and the third section temperature is 170 - 235°C; During the extrusion molding process, the rotation speed of the screw is 200 - 400r / min.

[0026] Example 2 The preparation steps of a carbon rod for removing chloramine and chloroform for water purification in this example are as follows: The preparation of microporous activated carbon in step 1 is the same as that in Example 1 Step 2: Preparation of nitrogen-containing activated carbon: Put 200g of the microporous coconut shell activated carbon obtained in step 1 into 500ml of 30% hydrogen peroxide oxidant, stir at 500r / min for 12h. Dry it at 50°C for 24h and store it in a sealed plastic bag for further experiments.

[0027] Put 200g of the activated carbon modified by hydrogen peroxide into a rotary activation furnace. After heating to 750°C under nitrogen protection, use ammonia gas as the activation gas, the ammonia gas flow rate is 80ml / min, the nitrogen gas flow rate is 100ml / min, and the activation time is 1 hour to obtain nitrogen-containing activated carbon Step 3: The preparation of carbon rods is the same as in Example 1 Example 3 Step 1: The preparation of microporous activated carbon is the same as in Example 1 Step 2: Preparation of nitrogen-containing activated carbon: Put 200 g of the microporous coconut shell activated carbon obtained in Step 1 into 500 ml of 30% hydrogen peroxide oxidant, stir at 500 r / min for 12 h. Dry at 50 °C for 24 h and store in a sealed plastic bag for further experiments.

[0028] Put 200 g of the activated carbon modified by hydrogen peroxide into a rotary activation furnace. After heating to 1000 °C under nitrogen protection, use ammonia gas as the activation gas, the ammonia gas flow rate is 80 ml / min, the nitrogen gas flow rate is 100 ml / min, and the activation time is 1 hour to obtain nitrogen-containing activated carbon.

[0029] Step 3: The preparation of carbon rods is the same as in Example 1 Example 4 Step 1: The preparation of microporous activated carbon is the same as in Example 1 II. Preparation of nitrogen-containing activated carbon: Without hydrogen peroxide oxidation, directly put 200 g of the microporous coconut shell activated carbon obtained in Step 1 into a rotary activation furnace. After heating to 750 °C under nitrogen protection, use ammonia gas as the activation gas, the ammonia gas flow rate is 80 ml / min, the nitrogen gas flow rate is 100 ml / min, and the activation time is 1 hour to obtain nitrogen-containing activated carbon.

[0030] Step 3: The preparation of carbon rods is the same as in Example 1 Comparative Example 1 I. Preparation of nitrogen-containing activated carbon: Put 200 g of commercially available black Carbo RWAP-4453 coconut shell activated carbon into 500 ml of 30% hydrogen peroxide oxidant, stir at 500 r / min for 12 h. Dry at 50 °C for 24 h and store in a sealed plastic bag for further experiments.

[0031] Put 200 g of the RWAP-4453 activated carbon modified by hydrogen peroxide into a rotary activation furnace. After heating to 750 °C under nitrogen protection, use ammonia gas as the activation gas, the ammonia gas flow rate is 80 ml / min, the nitrogen gas flow rate is 100 ml / min, and the activation time is 1 hour to obtain nitrogen-containing activated carbon The remaining steps are the same as in Example 1 Comparative Example 2 Step 1: Obtain coconut shell activated carbon in the same way as in Example 1

[0032] Step 2: Preparation of carbon rods According to the weight parts, take 70 parts of the coconut shell activated carbon in Step 1 and 30 parts of ultra-high molecular weight polyethylene binder.

[0033] Weigh the activated carbon powder and the binder according to the specified weight parts respectively, and then mix them in a two-dimensional mixer for 60 minutes. Extrude and cut the mixed material to obtain a carbon rod with an outer diameter, inner diameter, and length of 38*10*110 mm.

[0034] The remaining steps are the same as those in Example 1. Comparative Example 3 According to the weight parts, take 70 parts of commercially available black Carbo activated carbon RWAP-4453 coconut shell activated carbon and 30 parts of ultra-high molecular weight polyethylene binder.

[0035] Weigh the activated carbon powder and the binder according to the specified weight parts respectively, and then mix them in a two-dimensional mixer for 60 minutes. Extrude and cut the mixed material to obtain a carbon rod with an outer diameter, inner diameter, and length of 38*10*110 mm.

[0036] Use RO water to prepare general experimental water, adjust the TDS of the experimental water to be 200 - 500 mg / L using sodium chloride, adjust the TOC of the experimental water to be > 1 mg / L using chlorinated tannic acid, and control the experimental water temperature to be 20 ± 2.5 °C. Use chloroform as a spike and add it to the experimental water to prepare test water with a chloroform concentration of 300 ± 30 μg / L in the test water. Put the 7 carbon rods of Examples 1 - 4 and Comparative Examples 1 - 3 into a suitable test fixture, connect the test machine, and control the water flow rate to be 1.9 L / min. After flushing for 5 minutes, take filtered water samples at the points of 0 L, 200 L, 400 L, 600 L, and 800 L of water throughput, use GC-MS to test the chloroform concentration in the filtered water samples, and calculate the chloroform removal rate according to the chloroform concentration in the test water.

[0037] The experimental results of the above examples and comparative examples are listed in Table 1. Table 1 Chloroform removal rates of different carbon rods

[0038] Use RO water to prepare general experimental water, adjust the TDS of the experimental water to be 200 - 500 mg / L, use chlorinated tannic acid to adjust the TOC of the experimental water to be > 1 mg / L, and control the experimental water temperature to be 20 ± 3 °C. Prepare monochloramine test water with a monochloramine concentration of 3.0 ± 0.3 mg / L in the test water. Put the 7 carbon rods of Examples 1 - 4 and Comparative Examples 1 - 3 into a suitable test fixture, connect the test machine, and control the water flow rate to be 1.9 L / min. After flushing for 5 minutes, take filtered water samples at the points of 0 L, 200 L, 400 L, 600 L, and 800 L of water throughput, use a spectrophotometer to test the monochloramine concentration in the water samples, and calculate the monochloramine removal rate. The experimental results are listed in Table 2. Table 2 Removal rates of different carbon rods for monochloramine

[0039] Tables 1 and 2 list the activated carbons obtained by 7 different treatment methods. After making carbon rods with dimensions of 38*10*110 mm, the removal capabilities for chloroform and chloramine are respectively presented. From the test results of Examples 1 - 3, it can be seen that the higher the nitrogen / ammonia modification temperature, the better the chloramine catalytic ability and the higher the removal rate of the resulting final carbon rod product. This is because the higher the temperature, the more thoroughly the oxygen-containing functional groups on the activated carbon surface are converted into nitrogen-containing functional groups, and the more nitrogen element content there is, resulting in a better effect of catalyzing chloramine. However, too high an activation temperature will affect the microporous structure of the original carbon powder, and pore collapse occurs during the activation process, leading to a decrease in its adsorption ability for chloroform. According to the test results, when the activation temperature is 750 °C, the nitrogen-containing activated carbon obtained and made into a carbon rod has the best comprehensive removal ability for both chloroform and chloramine at the 800 L node, which are 97.46% and 84.23% respectively, meeting the removal requirements for the two substances in the NSF standard.

[0040] It can be seen from Example 4 that if the microporous activated carbon obtained in Step 1 is not treated with an oxidant, its removal performance for chloramine after being made into a carbon rod is lower than that of Example 2, indicating that pre-oxidation treatment can better improve the nitridation effect of the activated carbon. Comparative Example 1 directly carried out nitridation modification on a commercially available coconut shell activated carbon product with a mesh size of 80 - 325. The chloramine removal rate at the 800 L node was 84.52%, but at the same time, the removal rate for chloroform was lower than the NSF standard. This is because its micropores are small and the average pore size is large, resulting in a lower adsorption performance for chloroform than that of Example 2.

[0041] The embodiment of the present invention also provides a water purifier based on the above carbon rod.

[0042] By optimizing the pore structure and surface chemical properties of coconut shell activated carbon and combining with a specific forming process, the present invention significantly improves the adsorption ability of activated carbon for chloroform and the catalytic ability for chloramine. The nitrogen-containing activated carbon prepared by the present invention shows the best comprehensive performance at an activation temperature of 750 °C, and the removal rates for chloroform and chloramine reach 97.46% and 84.23% respectively, meeting the requirements of the NSF standard. The preparation method is simple and safe, suitable for large-scale production, and has good economic value and application prospects.

[0043] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention.

Claims

1. A preparation method of nitrogen-containing activated carbon, characterized in that, Comprising: S1, crushing the coconut shell raw material, washing it with pure water and then drying it, and carbonizing it under the protection of inert gas to obtain carbonized material; S2, crushing the carbonized material to a predetermined mesh number, and using a sieve to screen out the over-coarse or over-fine carbonized material to obtain coconut shell carbonized material; S3, placing the coconut shell carbonized material in a rotary activation furnace, and using water vapor as the activation gas for activation to obtain microporous coconut shell activated carbon; S4, washing and drying the microporous coconut shell activated carbon, and then crushing and screening it to 80 - 325 mesh; S5, placing the crushed and screened microporous coconut shell activated carbon in a rotary activation furnace, heating it to 500 - 1000 °C under the protection of inert gas, and then using a mixed gas of ammonia and ammonia as the activation gas for activation to obtain nitrogen-containing activated carbon.

2. The preparation method of the nitrogen-containing activated carbon according to claim 1, characterized in that, In step S1, drying is carried out at 80 °C for 24 h, and the carbonization temperature is 450 °C.

3. The preparation method of the nitrogen-containing activated carbon according to claim 1, characterized in that, In step S2, the predetermined mesh number is less than 80 mesh, preferably 20 mesh.

4. The preparation method of the nitrogen-containing activated carbon according to claim 1, characterized in that, In step S3, the water vapor flow rate is 30 ml / min, the activation time is 2 hours, and the activation temperature is 800 °C; the average pore diameter of the microporous coconut shell activated carbon is 1.6 - 2.0 nm, and the total pore volume is 0.45 - 0.50 cm 3 / g, where: the micropore volume is 0.36 - 0.40 cm 3 / g.

5. The preparation method of the nitrogen-containing activated carbon according to claim 1, characterized in that, In step S4, During washing: use 0.1M HCl solution for washing to remove inorganic salts and ash; During rinsing, use distilled water for rinsing until the pH is within the range of 6.5 - 7; During drying, dry at 105 °C for 10 h.

6. The preparation method of the nitrogen-containing activated carbon according to claim 1, wherein After step S4 and before step S5, it further includes: Placing the sieved microporous coconut shell activated carbon in a hydrogen peroxide oxidant, stirring it and then drying it to obtain hydrogen peroxide-modified microporous coconut shell activated carbon; Wherein, the concentration of the hydrogen peroxide oxidant is 30%; the stirring condition is stirring at 500 r / min for 12 h; the drying condition is drying at 50 °C for 24 h; In step S5, the inert gas is nitrogen; the ammonia gas flow rate is 80 ml / min, the nitrogen gas flow rate is 100 ml / min, and the activation time is 1 hour.

7. A nitrogen-containing activated carbon prepared by the preparation method according to any one of claims 1 to 6.

8. A carbon rod for removing chloramines and chloroform in water, characterized in that, By weight: Comprising 70 parts of the nitrogen-containing activated carbon according to claim 7 and 30 parts of ultra-high molecular weight polyethylene binder.

9. A method for preparing a carbon rod as described in claim 8, characterized in that, Comprising: Weighing the nitrogen-containing activated carbon and the binder according to a weight ratio of 7:3 respectively, and then mixing them using a two-dimensional mixer to obtain a mixed material; Extruding and cutting the mixed material to obtain a carbon rod capable of removing chloramine and chloroform; wherein, during the extrusion molding process, the extrusion includes three temperature segments, the first temperature segment is 120 - 160 °C, the second temperature segment is 180 - 240 °C, and the third temperature segment is 170 - 235 °C; During the extrusion molding process, the rotation speed of the screw is 200 - 400 r / min.

10. A water purifier, characterized in that, Comprising the carbon rod according to claim 8.

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