• Journal of Korean Society of Environmental Engineers
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• v.22 no.7
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• pp.1319-1330
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• 2000

Activated carbons prepared by chemical activation of organic waste sludges with $ZnCl_2$ and $K_2S$ have been studied in terms of their pore development and adsorptivity. Pore development of the carbons prepared from organic waste sludges was characterized by the nitrogen adsorption at 77K. The $ZnCl_2$-activated carbon produced by chemical activation with zinc chloride exhibited type I isotherm characteristics according to the BDDT classification, suggesting the presence of micropores formed by activation process. The isotherms of the commercial powdered activated carbon and $K_2S$-activated carbon reveal a hysteresis similar to that of type IV in BDDT classification, indicating the formation of mesopores. This result implies that the major pores of $K_2S$-activated carbon are composed of meso and micropores, and a macropores are minor. The adsorptive capacities of metal on the $K_2S$-activated carbon prepared from organic waste sludges were found to be superior to those on a commercial granular activated carbon. The Langmuir and Freundlich isotherms yield a fairly good fit to the adsorption data, indicating a monolayer adsorption of metals onto $K_2S$-activated carbon. The adsorptive capacity of the $K_2S$-activated carbon was superior to $ZnCl_2$-activated carbon for $PO_4$-P, and vice versa for $NO_3$-N. From the results of the studies reported here, it can be concluded that activated carbons with adsorptivity superior to commercial granular activated carbons can be produced from organic waste sludge using a two-step carbonization/activation procedure with zinc chloride or potassium sulfide as the activating agents.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.381-385
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• 2007

High density activated carbons electrode materials, for supercapacitor were prepared by chemical KOH activation of cokes as the starting material under Ar atmosphere. By controlling the synthesis conditions and reducing KOH quantity in the activation step, the specific surface area of the product was decreased. BET surface area was measured to be $500{\sim}1260m^2/g$, and the electrode density was in the range of $0.68{\sim}0.83g/cm^3$. Volumetric specific capacitance (unit cell test) was as high as 20 F/cc, which corresponds to gravimetric specific capacitance of about 95 F/cc on the basis of half cell test. It should be noted that the specific capacitance of the activated carbons prepared in this study is superior to that of commercial activated carbons.

• Korean Chemical Engineering Research
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• v.48 no.6
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• pp.752-756
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• 2010

Desorption reaction characteristics of the used activated carbons collected from painting process in Shiwha/Banwal industrial complex were investigated. Thermogravimetric analyzer was used to investigate the desorption characteristics. Activation energies and reaction orders for desorption reaction characteristics of used activated carbons were estimated by employing Friedman method and Freeman-Carroll method. In the used activated carbons collected from painting process, it was found that the activation energies were 20.6~43.2 kJ/mol in Friedman method and 12.3~26.5 kJ/mol in Freeman-carroll method, and reaction orders were 0.1~1.7.

• Carbon letters
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• v.12 no.1
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• pp.1-7
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• 2011

In the present study, the removal of Pb (II) ions on oxidized activated carbons (ACs) was investigated. ACs were derived from activation of indigenous cotton stalks waste with potassium hydroxide (KOH) in two-stage process. The KOH-ACs were subjected to liquid-phase oxidation with hot $HNO_3$ and one untreated sample was included for comparison. The obtained carbons were characterized by Fourier transform infrared (FTIR), slurry pH and $N_2$-adsorption at 77 K, respectively. Adsorption capacity of Pb (II) ions on the resultant carbons was determined by batch equilibrium experiments. The experimental results indicated that the oxidation with nitric acid was associated with a significant increase in mass of yield as well as a remarkable reduction in internal porosity as compared to the untreated carbon. The AC-800N revealed higher adsorption capacity than that of AC-800, although the former sample exhibited low surface area and micropore volume. It was observed that the adsorption capacity enhancement attributed to pore widening, the generation of oxygen functional groups and potassium containing compounds leading to cation-exchange on the carbon surface. These results show that the oxidized carbons represented prospective adsorbents for enhancing the removal of heavy metals from wastewater.

• Journal of the Korean Applied Science and Technology
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• v.20 no.1
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• pp.72-79
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• 2003

The impregnated activated carbons were prepared by the incipient wetness method with the contents of $KIO_3$ varied from 1.0${\sim}$10 wt% as the impregnation material. The specific surface area and micropore volume of the rice hulls activated carbon were $2,600{\sim}2,800$ $m^2$/g and 1.1${\sim}$1.4 cc/g, respectively. With increasing the contents of impregnation materials, the surface area and micropore volume decreased by 3${\sim}$21%. However, The amounts of hydrogen sulfide adsorbed increased by 2.1${\sim}$2.8 times depending on the impregnation content. The optimum contents of $KIO_3$ were 2.4 wt%. Although the breakthrough time and adsorption capacity of hydrogen sulfide decreased with increasing temperature in the case of the unimpregnated activated carbons, they increased by 1.2${\sim}$ 3.2 times for the case of the impregnated activated carbons. The optimum aspect ratio(L/D) was 1.0 and the adsorption amount of hydrogen sulfide enhanced with increasing the gas flow rate. The regeneration temperature was determined as 400$^{\circ}C$ from the TGA experiment. The adsorption capacity of hydrogen sulfide with the impregnated activated carbon decreased gradually as the regeneration continued. The hydrogen sulfide adsorption amount of the regenerated activated carbon up to 4 times was still higher than that of the unimpregnated activated carbon.

• Carbon letters
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• v.2 no.3_4
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• pp.176-181
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• 2001

A series of activated carbons were prepared from coconut shells and coal-tar pitch binder by physical activation with steam in this study. The effect of variable processes such as activation temperature, activation time and ratio of mixing was investigated for optimizing those preparation parameters. The activation processes were carried out continuously. The nitrogen adsorption isotherms at 77 K on pellet-shaped activated carbons show the same trend of Type I by IUPAC classification. The average pore sizes were about 19-21${\AA}$. The specific surface areas ($S_{BET}$) of pellet typed ACs increased with increasing the activation temperature and time. Specific surface area of AC treated for 90 min at temperature $900^{\circ}C$ was 1082 $m^2/g$. The methylene blue numbers continuously increased with increasing the activation temperature and time. On the other hand, iodine numbers highly increased till activation time of 60 min, but the rate of increase of iodine numbers decreased after that time. This indicates that new micropores were created and the existing micropores turned into mesopores and macropores because of increased reactivity of carbon surface and $H_2O$.

• Carbon letters
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• v.9 no.4
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• pp.275-282
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• 2008

Chemically activated carbons were prepared from maize cobs, using phosphoric acid of variable concentration. The textural parameters of the activated carbons were determined from the nitrogen adsorption isotherms measured at 77 K. The chemistry of the carbon surface was determined by measuring the surface pH, the pHPZC and the concentration of the carbon - oxygen groups of the acid type on the carbon surface. Kinetics of Cr(VI) sorption/reduction was investigated at 303 K. Two processes were investigated in terms of kinetics and equilibrium namely; Cr(VI) removal and chromium sorption were studied at various initial pH (1-7). Removal of Cr(VI) shows a maximum at pH 2.5. At pH<2.5, sorption decreases because of the proton competition with evolved Cr(III) for ion exchange sites. The decrease of sorption at pH>2.5 is due to proton insufficiency and to the decrease of the extent of Cr(VI) reduction. The chemistry of the surface of activated carbon is an important factor in determining its adsorption capacity from aqueous solutions particularly when the sorption process involves ion exchange.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.1
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• pp.31-37
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• 2002

This paper was investigated to clarify the possibility of a biodegradation of materials adsorbed on different porous granular-activated carbons (GACs) such as coal-& coconut-based GAC. Total organic carbon, humic substance and ammonia were used to compare their removal efficiencies. The objective of this study is to determine the adsorption capacity of bioregenerated GAC. When raw water reacted with chloride, the yield of THMs increased as a function of the input amount of chloride. The formation of trihalomethanes (THMs) was investigated in water treated with chlorine when humic acid was used as THM precursor. As the input amount of chloride in raw water increased by two or five-fold to remove the $NH_3$, the chloroform of the THMs significantly increased also five or ten-fold. It was found that the chloroform was significantly removed by the treatment of biological activated carbon (BAG) in comparison with the ozone treatment, and the removal efficiency of THMs in coal-typed GAC was $10-30\%$ better than coconut-typed GAC due to the biological degradation on the surface of the activated carbons.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06b
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• pp.279-284
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• 2006

Activated carbon is proposed as a new application of wastepaper recycling other than the paper-making. Waste kraft bag is considered to be a suitable raw material for activated carbon because of its low ash content. Small pellets of wastepaper squeezed out from the continuous kneader were carbonized in a nitrogen atmosphere and activated using carbon dioxide. The BET specific surface areas of activated carbon prepared from waste kraft bag was $1,285m^{2}/g$, which is higher than commercially available activated carbons. The activated carbon prepared from wastepaper has a well-developed porous structure, particularly in mesopore and macropore ranges. As a result, activated carbon with iodine adsorption capacity of 1,400 mg/g was obtained from waste kraft bag. In this paper, adsorption amount of Bisphenol A (BPA) was determined to investigate adsorbability of activated carbon from waste kraft bag. Adsorption measurements were on solutions ranging from $0.1{mu}g/L\;to\;100mg/L$. The activated carbon from waste kraft bag gave higher BPA adsorbabilities over a wide range, compared with commercially available activated carbons.

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.456-459
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• 2011

Among the various activated carbons available in the market, an optimum mixing method of two kind activated carbons with different adsorbability was investigated in this study. The representative adsorption behaviors of the activated carbon are the adsorption isotherm plots obtained by the BET-Analysis which suggests also basic information of adsorption filter design. So we have tested three cases with certifications, the one was the extreme case of coal cokes based activated carbon with highest BET-model and coconut-shell based activated carbon with the lowest Langmuir-model, the other middle and cross case were applied this method to two kinds of activated carbons with higher and lower specific surface areas which are not available but supplied as research samples by an authority of an Korean Research Institute.