• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3507-3508
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• 2010

• Carbon letters
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• v.18
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• pp.62-66
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• 2016

• Resources Recycling
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• v.17 no.6
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• pp.68-78
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• 2008

Using a Pinus koraiensis and Pinus rigida which are normally being discarded in South Korea, optimal conditions of producing activated carbons have been studied to recycle as a higher value-added product. This study consists of two processes, the production process of charcoals from waste timbers by low temperature pyrolysis and the production process of activated carbons from the charcoals by chemical activation reaction. This paper deals with the production process of activated carbons from the charcoals by chemical activation reaction. As an alkali has been generally used as an activating agent, KOH and NaOH which react well with a carbon were used in this study. As a result of the experiments, it is confirmed that activated carbons made with KOH treatment had superior values in physicochemical properties to NaOH, showing that there was no remain of KOH at the surface of the charcoals while there was $3{\sim}4%$ of NaOH remaining after the experiments. Thus, it is concluded that KOH reacted more actively with a charcoal than NaOH. Moreover, it was also found that values in physicochemical properties when using a Pinus koraiensis are superior to the ones when using a Pinus rigida. The optimal mixing ratio of an activating agent to a charcoal was 400 wt.%. To improve the physicochemical properties, activated carbons were washed out by distilled water after neutralization with SM hydrochloric acid solution. When activated carbons were produced from a Pinus koraiensis in this optimal conditions, value of BET surface area was found to be approx. $2400\;m^2/g$.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.237-243
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• 2018

The surface chemistry of WCK-AC, WCN-AC and WCZ-AC which are activated carbons prepared from waste citrus peel using KOH, NaOH, and $ZnCl_2$ as activating chemicals were investigated. Also the relationships between the adsorption capacities of the target gases such as acetone, benzene and methyl mercaptan (MM) by the prepared activated carbons and the pore characteristics of each activated carbon were examined. According to XPS analysis of the prepared activated carbons, graphite and phenolic were the main surface functional groups of C1, and the sum of phenol, carbonyl and carboxyl groups increased in the order of WCK-AC > WCN-AC > WCZ-AC. The breakthrough curves obtained from the adsorption experiments for the three target gases in the fixed bed adsorption reactor were well simulated by the empirical equations proposed by Yoon and Nelson. The adsorption capacity for acetone, benzene and MM was larger for activated carbons with the larger sum of surface functional groups. The larger the specific surface area and the pore volume of activated carbons and the smaller the pore size, the better the adsorption performance. In particular, the specific surface area was the best criterion for the adsorption performance of activated carbons used in this study.

• Journal of Environmental Science International
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• v.17 no.5
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• pp.565-571
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• 2008

The surface properties of activated carbon modified by acids and base were studied. The influence of the surface chemistry on the adsorption of benzene and acetone vapor on modified activated carbons has been investigated The modified activated carbons were obtained by treatment with acetic acid ($CH_3COOH$), nitric acid ($HNO_3$) and sodium hydroxide (NaOH). The modified activated carbons had similar porosity but different surface chemistry and adsorption characteristics. The total surface acidity (sum of functional groups) of activated carbon (AC-AN) treated by nitric acid was 2.6 times larger than that of activated carbon (AC) before the acid treatment. Especially, carboxyl group was much developed by nitric acid treatment. The benzene equilibrium adsorption capacity of AC-AN decreased 20% more than that of AC. However, the acetone equilibrium adsorption capacity of AC-AN increased 20% more than that of AC because of the large increase of carboxyl group and acidity.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1321-1326
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• 2011

In this work, the effects of different surface functional groups on the elemental mercury adsorption of porous carbons modified by chemical treatments were investigated. The surface properties of the treated carbons were observed by Boehm's titration and X-ray photoelectron spectroscopy (XPS). It was found that the textural properties, including specific surface area and pore structures, slightly decreased after the treatments, while the oxygen content of the ACs was predominantly enhanced. Elemental mercury adsorption behaviors of the acidtreated ACs were found to be four or three times better than those of non-treated ACs or base-treated ACs, respectively. This result indicates that the different compositions of surface functional groups can lead to the high elemental mercury adsorption capacity of the ACs. In case of the acid-treated ACs, the $R_{C=O}/R_{C-O}$ and $R_{COOH}/R_{C-O}$ showed higher values than those of other samples, indicating that there is a considerable relationship between mercury adsorption and surface functional groups on the ACs.

• Carbon letters
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• v.7 no.2
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• pp.97-104
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• 2006

The influence of carbon surface area, carbon-oxygen groups associated with the carbon surface and the solution pH on the adsorption of Pb(II) ions from aqueous solutions has been studied using three activated carbons. The adsorption isotherms are Type I of BET classification and the data obeys Langmuir adsorption equation. The BET surface area has little effect on the adsorption while it is strongly influenced by the presence of acidic carbon oxygen surface groups. The amount of these surface groups was enhanced by oxidation of the carbons with different oxidizing agents and reduced by eliminating these groups on degassing at different temperatures. The adsorption of Pb(II) ions increases on each oxidation and decreases on degassing the oxidized carbons. The increase in adsorption on oxidation has been attributed to the formation of acidic carbon-oxygen surface groups and the decrease to the elimination of these acidic surface groups on degassing. The adsorption is also influenced by the pH of the aqueous solution. The adsorption is only small at pH values lower than 3 but is considerably larger at higher pH values. Suitable mechanisms consistent with the adsorption data have been suggested.

• Journal of Environmental Science International
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• v.15 no.7
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• pp.695-699
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• 2006

This study is to investigate the relationship between pore structures of activated carbons and adsorption characteristics of toluene vapor using dynamic adsorption method. The surface areas of below $10{\AA}$ in the pore diameter of activated carbons used in this experiment were in the range of 72 -93 % of total cumulative surface area and the toluene vapor equilibrium adsorption capacities were in the range of 350 - 390mg/g. Activated carbons having larger toluene adsorption capacity than the compared activated carbons had relatively pores in the pore diameter range of $7-10{\AA}$. Linear relationship between equilibrium adsorption capacity and cumulative sur- face area was in the diameter range of over $7{\AA}$. It was thought that toluene vapor was relatively well adsorbed on surfaces of pores of over $7{\AA}$.

• Carbon letters
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• v.14 no.4
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• pp.234-242
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• 2013

Potassium hydroxide-activated carbons (CK21, CK11, and CK12) were prepared from pistachio nutshells. Physicochemical properties of activated carbons were characterized by TGA, $pH_{pzc}$, Fourier transform infrared spectroscopy, scanning electron microscopy, and $N_2$-adsorption at $-196^{\circ}C$. The examinations showed that activated carbons have high surface area ranging between 695-1218 $m^2/g$, total pore volume ranging between 0.527-0.772 mL/g, and a pore radius around 1.4 nm. The presence of acidic and basic surface C-O groups was confirmed. Batch adsorption experiments were carried out to study the effects of adsorbent dosage, temperature, initial concentration of adsorbate, and contact time on deltamethrin adsorption by activated carbons. The kinetic studies showed that the adsorption data followed a pseudo-second order kinetic model. The Langmuir model showed a maximum adsorption capacity of 162.6 mg/g at $35^{\circ}C$ on CK12. Thermodynamic studies indicated that adsorption was spontaneous and increased with temperature, suggesting an endothermic process.

• Carbon letters
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• v.13 no.4
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• pp.236-242
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• 2012

Poly(vinylidene chloride) (PVDC)-derived nanoporous carbons were prepared by various activation methods: heat-treatment under an inert atmosphere, steam activation, and potassium hydroxide (KOH) activation at 873, 1073, and 1273 K. The pore structures of PVDC-derived nanoporous carbons were characterized by the $N_2$ adsorption technique at 77 K. Heat treatment in an inert atmosphere increased the specific surface area and micropore volume with elevating temperature, while the average micropore width near 0.65 nm was not significantly changed, reflecting the characteristic pore structure of ultramicroporous carbon. Steam activation for PVDC at 873 and 1073 K also yielded ultramicroporosity. On the other hand, the steam activated sample at 1273 K had a wider average micropore width of 1.48 nm, correlating with a supermicropore. The KOH activation increased the micropore volume with elevating temperature, which is accompanied by enlargement of the average micropore width from 0.67 to 1.12 nm. The average pore widths of KOH-activated samples were strongly governed by the activation temperature. We expect that these approaches can be utilized to simply control the porosity of PVDC-derived nanoporous carbons.