• 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.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.146-152
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• 2019

In order to study the transport behavior of tripolyphosphate (TPP) in aqueous solutions, the adsorption process of TPP on synthetic goethite, which exists stably in supergene environment, has been systematically studied. The adsorption properties under different conditions (pH, electrolyte presence, and temperature) were investigated. The adsorption of TPP in the presence of humic acid (HA)/fulvic acid (FA) has also been discussed in this paper. The results indicated that the adsorption capacity quickly increased within the first hour and equilibrium was reached within 24 h. The adsorption capacity decreased from 1.98 to 0.27 mg·g^-1 upon increasing the pH from 8.5 to 11.0, whereas the adsorption of TPP on goethite hardly changed with increasing electrolyte concentration. The results of analysis of the kinetic and isothermal models showed that the adsorption was more in accord with the pseudo second-order equation and Freundlich model. The adsorption capacity decreased obviously regardless of the order of addition of TPP, HA, and goethite. Subsequent addition of FA led to a large increase in the adsorption capacity, which might be attributed to the adsorption ability of FA. According to the predictions of the kinetic and isothermal models and the spectroscopic evidence (X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM)), the adsorption mechanism may be mainly based on surface complexation and physical adsorption.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.409-414
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• 1996

Radionuclides such as Cs and Sr were removed from dilute aqueous solutions by means of inorganic adsorbents, 13X and chabazite. The physical adsorption obeyed the DA equation and non-equilibrium dynamic adsorption model, which describes surface diffusion mechanism with the DA equation, simulated the adsorption behavior of cesium and strontium on zeolite in fixed bed adsorbers. The dynamic model simulated the adsorption behavior of cesium and strontium.

• Carbon letters
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• v.13 no.2
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• pp.61-72
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• 2012

Dye removal from waste water via adsorption by activated carbons (ACs) developed from agricultural wastes represents an ideal alternative to other expensive treatment options. Physical and chemical ACs were prepared from rice husks. The textural properties of the ACs were characterized by Brunauer-Emmett-Teller-$N_2$ adsorption and scanning electron microscopy. The chemistry of the carbon surface was investigated by Fourier transform infrared spectroscopy, base and acid neutralization capacities, pH of the active carbon slurry, and $pH_{pzc}$. The adsorption capacities of the ACs for the basic dye (methylene blue) and acid dye (acid green 25) were determined using parameters such as contact time, pH, and temperature. NaOH-ACs showed the highest surface area and total pore volume, whereas steam-ACs showed the lowest ones.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.307-312
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• 2001

Adsorption capacities of toxic heavy metal ions using as-received carbon(AC), single and double surface-modified activated carbon(OAC and DSMC) in wide pH ranges are extensively evaluated. Physical and chemical properties of surface-modified activated carbons are evaluated through BET analysis, surface acidity and oxides measurements. Based oil tile adsorption isotherms of Pb, Cd and Cr ions by AC, OAC and DSMC, the adsorption amount on DSMC was obviously higher than that on the other carbons. Breakthrough behaviors of ternary metal ions in a column packed with three kinds of carbon were also characterized with respect to the variations of the influent pH and concentration. The adsorption capacity of DSMC in a fixed bed stood a favorable comparison with that of as-received carbon.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.628-635
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• 2016

Natural gas reformed hydrogen is used as a fuel of fuel cell vehicle, PSA process is used for the purification of reformed hydrogen. In this study, the performance of CO adsorbent in PSA process was evaluated. Zeolite adsorbents used in the commercial PSA process is used. The physical and chemical properties of adsorbents were characterized using BET apparatus, XRD, and FE-SEM. The breakthrough apparatus modified from GC was used for the CO breakthrough experiment, the quantitative analysis of CO adsorption capacity was performed using CO breakthrough curve. Zeolite 10X and 13X showed superior CO adsorption capacity than activated alumina. The CO adsorption capacity of zeolite 10X is more than twice of zeolite 13X even the BET surface area is low. It seems that the presence of $Ca^{2+}$ cation in zeolite 10X is beneficial to the adsorption of CO.

• Environmental Engineering Research
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• v.24 no.1
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• pp.99-106
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• 2019

Using the abandoned agricultural by-product corncobs, the most commonly used methylene blue (MB) dyestuffs were removed. This experiment is very meaningful because it is the recycling of resources and the use of environmentally friendly adsorbents. According to the Hauser ratio and porosity analysis, the corncob has a good flow ability of the adsorbent material and many pores, which is very advantageous for MB adsorption. As a result of the experiment, MB concentration of less than 0.005 g/L was very efficiently removed with 10 g/L of bioadsorbent corncob and the maximum adsorption capacity of corncob for MB dyes was obtained at 417.1 mg/g. In addition, adsorption process of MB onto corncob was a physical process according to adsorption energy analysis. Corncob can efficiently and environmentally remove MB in aqueous solution, and is very cost effective and can recycle the abandoned resources.

• Bulletin of the Korean Chemical Society
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• v.9 no.4
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• pp.244-248
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• 1988

Multilayer adsorption isotherms of nitrogen on hexagonal boron nitride, ${\gamma}$-alumina, and silica-gel powders are determined at the liquid nitrogen temperature using a gravimetric adsorption apparatus. The volume (V) of the adsorbed gas are plotted against the statistical thickness(t) of the adsorbed layer, and the t-method area are calculated from the slope of these V-t plots to compare with the BET area. A number of universal adsorption isotherms and the Frenkel-Halsey-Hill equation are used one after another in calculating the statistical thickness. The appropriateness of the FHH equation as an universal adsorption isotherm is discussed finally.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.1
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• pp.68-76
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• 2014

The present study has evaluated the $CO_2$ adsorption amount of activated carbon pellets (AC). Coconut shell based test AC were modified with surface impregnation of glycine, glycine metal salts and monoethanolamine for low level $CO_2$ (3000 ppm) adsorption. Physical and chemical properties of prepared adsorbents were analyzed and the adsorbed amount of $CO_2$ was investigated by using pure and 3,000 ppm $CO_2$ levels. The impregnation of nitrogen functionalities was verified by XPS analysis. The adsorption capacity for pure $CO_2$ gas was found to reach upto 3.08 mmol/g by AC-LiG (Activated carbon-Lithium glycinate), which has the largest specific surface area ($1026.9m^2/g$). As for low level $CO_2$ flow the primary amine impregnated adsorbent showed 0.26 mmol/g of adsorption amount, indicating the highest selectivity. An adsorbent with potassium-glycine salts (AC-KG, Activated carbon-Potassium glycinate) instead of amine presented with 0.12 mmol/g of adsorption capacity, which was higher than that of raw activated carbon granules (0.016 mmol/g).

• Journal of the Korean Society of Tobacco Science
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• v.35 no.1
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• pp.7-12
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• 2013

A Solid-phase micro extraction(SPME) was evaluated as a tool for headspace sampling of tobacco samples. Several experimental parameters (sampling temperature, pH, and type of SPME fibers) were optimized to improve sampling efficiency in two aspects ; maximum adsorption and selective adsorption of volatile organic acids onto SPME fibers. Among four types of SPME fibers such as PDMS(Polydimethylsiloxane), PA(Polyacrylate), Car/PDMS (Carboxen/Polydimethylsiioxane) and PDMS/DVB(Polydimethylsiioxane/Divinylbenzene) which were investigated to determine the selectivity and adsorption efficiency. A variety of tobacco samples such as flue cured, burley and oriental were used in this study. The effect of these parameters was often dominated by the physical and chemical nature (volatility, polarity) of target compounds. This method allowed us to make important improvements in selectivity and sensitivity. The Car/PDMS fiber was shown to be the most efficient at extracting the 10 selected volatile organic acids. The parameters were optimized: $80^{\circ}C$ adsorption temperature, 30 min of adsorption time, $240^{\circ}C$ desorption temperature, 1 min of adsorption time.