Granular activated carbon having many mesopores, and manufacturing method for same

Abstract

Provided is a granular activated carbon having many mesopores that can be used for applications similar to sine chloride-activated carbons, and also provided is a method for manufacturing the same. The granular activated carbon is obtained by bringing an activated carbon into contact with a calcium component, followed by activation and washing.

Claims

1. A granular activated carbon having the following properties (1) to (4): (1) an ignition residue of 2 mass fraction % or less; (2) a hardness of 60 mass fraction % or more; (3) a mesopore volume of 0.5 mL/g or more; and (4) comprising an activated carbon raw material being at least one member selected from the group consisting of coconut shells, natural fibers, synthetic fibers, and synthetic resins.

2. A method for manufacturing a granular activated carbon having a hardness of 60 mass fraction % or more, comprising the following steps (A) to (C) of: (A) bringing an activated carbon raw material into contact with a calcium component, wherein the content of the calcium component, which is attached to the activated carbon surface and pores after being brought into contact therewith, in the activated carbon is, in terms of calcium, 0.5 to 2 wt %, wherein the calcium component is at least one member selected from the group consisting of calcium chloride, calcium carbonate and calcium hydroxide; (B) activating the activated carbon raw material obtained in step (A); and (C) washing the activated carbon obtained in step (B), wherein an activation yield in step (B) is set to 20 to 32.9% and the granular activated carbon has a hardness of 60 mass fraction % or more.

3. A granular activated carbon obtained by the manufacturing method according to claim 2.

4. The manufacturing method according to claim 2, wherein the activated carbon raw material is selected from the group consisting of coconut shells, natural fibers, synthetic fibers, and synthetic resins.

5. A granular activated carbon obtained by the manufacturing method according to claim 4.

6. The manufacturing method according to claim 4, wherein the activated carbon raw material is a coconut shell.

7. A granular activated carbon obtained by the manufacturing method according to claim 6.

8. A method for manufacturing a granular activated carbon having a hardness of 60 mass fraction % or more, comprising the following steps (A) to (D) of: (A) carbonizing an activated carbon raw material, followed by pulverization; (B) mixing the activated carbon raw material obtained in step (A) with a calcium component wherein the amount of the calcium component is, in terms of calcium, 0.5 to 1.5 parts by weight, based on 100 parts by weight of the pulverized product after carbonization in step (A), wherein the calcium component is selected from the group consisting of calcium chloride, calcium carbonate and calcium hydroxide, followed by molding; (C) carbonizing and activating the activated carbon raw material obtained in step (B); and (D) washing the activated carbon obtained in step (C), wherein an activation yield in step (C) is set to 10 to 25% and the granular activated carbon has a hardness of 60 mass fraction % or more.

9. A granular activated carbon obtained by the manufacturing method according to claim 8.

10. The manufacturing method according to claim 8, wherein the activated carbon raw material is selected from the group consisting of coconut shells, natural fibers, synthetic fibers, and synthetic resins.

11. A granular activated carbon obtained by the manufacturing method according to claim 10.

12. The manufacturing method according to claim 10, wherein the activated carbon raw material is a coconut shell.

13. A granular activated carbon obtained by the manufacturing method according to claim 12.

Description

BRIEF DESCRIPTION OF DRAWING

(1) FIG. 1 shows an example of the hardness test plate used for the hardness measurement specified in JIS K1474.

DESCRIPTION OF EMBODIMENTS

(2) The present invention is described in detail below with reference to Examples and Comparative Examples; however, the present invention is not limited thereto.

EXAMPLES

Example 1

(3) Coconut shells (produced on Mindanao Island of the Republic of the Philippines) were carbonized at a reaching temperature of 650° C. for 8 hours, and then activated by steam at 900° C., thereby obtaining a coconut shell-activated carbon (specific surface area: 1,282 m.sup.2/g). To 500 g of the coconut shell-activated carbon, a calcium chloride aqueous solution (10 g of calcium chloride and 350 g of water) was sprayed so that the amount of calcium chloride was 2 wt. %. Thereafter, the resulting product was dried in an electric dryer adjusted to 115±5° C. The calcium content of the activated carbon, was 0.8 wt. %.

(4) The dried calcium-contact activated carbon (200 g) was activated by steam under the conditions shown in Table 1. After cooling, the obtained activated product was washed by boiling in a hydrochloric acid aqueous solution (concentration: 3 wt. %) for 10 minutes, and then boiled in water for 10 minutes three times. After draining, the resulting product was dried in an electric dryer adjusted to 115±5° C., and pulverized by using a roll mill to a particle size of 0.6 to 0.212 mm, followed by particle size regulation, thereby obtaining an activated carbon.

Example 2

(5) An activated carbon was obtained in the same manner as in Example 1, except that 15 g of calcium chloride and 350 g of water were used as the calcium chloride aqueous solution, the calcium content of the activated carbon was changed to 1.1 wt. %, and the activation time was changed as shown in Table 1.

Comparative Example 1 and 2

(6) Coconut shells (produced, on Mindanao Island of the Republic of the Philippines) were carbonized at 550° C. for 8 hours, and then pulverized to an average particle diameter of 20 to 80 μm. The pulverized product (1,000 g), a calcium aqueous solution prepared by dissolving 25 g of calcium chloride (special grade chemical; produced by Wako Pure Chemical Industries, Ltd.) in 57 g of water, 250 g of hard pitch having a softening point of 110° C., 80 g of creosote, 15 g of lignin (SAN X-M, produced by Nippon Paper Industries Co., Ltd.), and 73 g of water were placed in a kneader and mixed for 25 minutes. Then, the resulting mixture was extruded from an extrusion granulator (pore size: 4 mm). The extruded product was heated to 650° C. at a ratio of 5° C./min, and then maintained for 30 minutes, thereby obtaining a coconut shell-carbonized product. The carbonized product was activated by steam under the conditions shown in Table 1. The obtained activated, product was not washed. Thus, an activated carbon was obtained.

Example 3

(7) Coconut shells (produced on Mindanao Island of the Republic of the Philippines) were carbonized at 550° C. for 8 hours, and then pulverized to an average particle diameter of 20 to 80 μm. The pulverized product (1,000 g), 27.5 g of calcium carbonate (special grade chemical; produced by Wako Pure Chemical Industries, Ltd.), 250 g of hard pitch having a softening point of 110° C., 80 g of creosote, 15 g of lignin (SAN X-M, produced by Nippon Paper Industries Co., Ltd.), and 130 g of water were placed in a kneader and mixed for 25 minutes. Then, the resulting mixture was extruded from an extrusion granulator (pore size: 4 mm), and carbonization and steam activation were performed. The carbonization conditions were as follows: carbonization reaching temperature: 650° C.; temperature increase rate: 5° C./min; and retention time: 30 minutes. The steam activation conditions were as follows: activation temperature: 900° C.; activation time: 135 minutes; and activation yield: 45.5%. Thereby, activated carbon A (specific surface area: 1.208 m.sup.2/g, pore volume: 0.585 mL/g, and mesopore ratio (mesopore volume/total pore volume)=0.42) was obtained. Subsequently, activated carbon A was activated by steam again for 150 minutes at an activation temperature of 900° C. until the activation yield reached 35%. The obtained, activated product (final activation yield: 15.9% (=45.5%×35%) based on the product after carbonization for a retention time of 30 minutes) was washed by boiling in a hydrochloric acid aqueous solution (concentration: 3 wt. %) for 10 minutes, and then boiled in water for 10 minutes three times. After draining, the resulting product was dried in an electric dryer adjusted to 115±5° C., and pulverized by using a roll mill to a particle size of 0.6 to 0.212 mm, followed by particle size regulation, thereby obtaining an activated carbon.

(8) TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 Comp. Ex. 1 Comp. Ex. 2 Activation temperature (° C.) 900 900 900 900 Activation time (min) 165 180 180 210 Activation yield (%) 32.9 23.2 34.4 22.8
Performance Measurement of Activated Carbon

(9) Nitrogen adsorption isotherms of the activated carbons obtained in Examples 1 to 3 and Comparative Examples 1 and 2 above, and an activated carbon obtained in Comparative Example 3 below, were measured at the boiling point temperature of liquid nitrogen. The specific surface area was determined by the BET method, and the pore distribution was determined by the CI method. Pores with a diameter of up to 2 nm were regarded as micropores, and pores with a diameter of 2 to 30 nm were regarded as mesopores. Further, the ignition residue, iodine adsorption performance, and hardness were measured according to JIS K1474.

Comparative Example 3

(10) A commercially available zinc chloride-activated granular activated carbon (Granular Shirasagi KL, produced by Japan EnviroChemicals) was used.

(11) Table 2 shows the performance measurement results.

(12) TABLE-US-00002 TABLE 2 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1 Ex. 2 Ex. 3 Ignition residue 0.3 0.2 1.6 1.6 2.2 0.6 (mass fraction %) Hardness (mass 78 66 62 77 18 55 fraction %) Iodine adsorption 1680 1810 1570 1280 1630 980 performance (mg/g) Specific surface 2027 2058 1754 1362 1859 1413 area (m.sup.2/g) Pore volume (ml/g) 1.233 1.62 1.166 0.828 1.159 1.182 Mesopore volume 0.63 1.11 0.71 0.45 0.72 0.96 (ml/g)
Decolorization Performance Measurement of Activated Carbon

(13) The activated carbons of Examples 1 to 3 and Comparative Example 3 were prepared, and each activated, carbon was pulverized. The pulverization of each activated carbon was performed so that 30% or more of a suitable amount of sample was passed through the 45-μm mesh sieve specified in JIS Z 8801-1 (sieve frame size: inner diameter of the portion above the sieve surface: 75 mm). Subsequently, the pulverized activated carbons of Examples 1 to 3 and Comparative Example 3 were each added to 50 mL of commercially available thin soy sauce (registered trademark: Higashimaru, produced by Higashimaru Shoyu Co., Ltd.). Each of the resulting mixtures was shaken at 25° C. for 3 hours, followed by filtration, thereby obtaining a filtrate. Next, the absorbance of each filtrate was measured at a wavelength of 460 nm, and the absorbance adsorption amount per unit mass of the activated carbon when the filtrate was decolorized to 1/10 of the original absorbance (3.8) was calculated, and determined.

(14) Table 3 shows the results.

(15) TABLE-US-00003 TABLE 3 Soy sauce absorbance adsorption amount (E .Math. L/g) Ex. 1 0.21 Ex. 2 0.25 Ex. 3 0.25 Comp. Ex. 3 0.18

(16) The mesopore volume of the activated carbons of the present invention was equivalent to that of the commercially available zinc chloride-activated granular activated carbon. Further, the decolonization performance of the activated carbons of the present invention was equal to or higher than that of the zinc chloride-activated carbon (Examples 1 to 3).

(17) In contrast, the mesopore volume of the activated carbon of Comparative Example 1 was insufficient. Although the mesopore volume was increased by reducing the yield, the hardness was very low, making it unusable as a granular activated carbon (Comparative Example 2).

(18) The activated carbons of the present invention had a higher hardness and much more excellent iodine adsorption performance than the zinc chloride-activated carbon (Examples 1 to 3 and Comparative Example 3). Therefore, the activated carbons of the present invention can be regarded as granular activated carbons having sufficient hardness, excellent handling properties, and high adsorption performance.

INDUSTRIAL APPLICABILITY

(19) The activated carbon of the present invention can be used for liquid treatment applications, particularly applications in which decolorization performance is an issue, as a granular activated carbon in a column passing system, in contrast to conventional wood-based zinc chloride-activated carbons. Furthermore, due to its high adsorption performance for low-molecular-weight compounds, the activated carbon of the present invention can be suitably used as an activated carbon for solution adsorption treatment (particularly, an activated carbon for solution purification).