• Carbon letters
• /
• v.8 no.2
• /
• pp.108-114
• /
• 2007

In this work, activated carbon (AC) after $HNO_3$ modification was used as the support during the production of supported $TiO_2$ to increase the high deposition efficiency and the photocatalytic activity. The results of $N_2$ adsorption showed that the BET surface area of samples decreased with an increasing of the concentration of $HNO_3$ due to the penetration of $TiO_2$. From XRD data, a single crystal structure of anatase peak was observed in diffraction patterns for the AC coated with titanium complexes. From the SEM results, almost all particles were aggregated with each other at the carbon surface and AC was covered with $TiO_2$ particles in all of the samples. The EDX spectra show the presence of C, O, Ti and other elements. It was also observed a decreasing of amount of C content with increasing Ti and O content from the EDX. The results of FT-IR revealed that the modified AC contained more surface oxygen bearing groups than that of the original AC. The effect of surface acidity and basity calculated from Boehm titration method was also evaluated from correlations as a function of NaOH, $NaHCO_3$, and $Na_2CO_3$ uptake. The surface modification of AC by $HNO_3$ leads to an increase in the catalytic efficiency of AC/$TiO_2$ catalysts, and the catalytic efficiency increases with increasing of $HNO_3$ concentration.

• Journal of Korean Society of Water and Wastewater
• /
• v.34 no.6
• /
• pp.425-435
• /
• 2020

Numerous chemical modifications on activated carbon such as acidic conditioning, thermal treatment and metal impregnation have been investigated to enhance adsorption capacities of micropollutants in water treatment plants. In this study, chemical modification including acidic, alkaline treatment, and iron-impregnation was evaluated for adsorption of 2,4-dichlorophenol (2,4-DCP). For Fe-impregnation, three concentrations of ferric chloride solutions, i.e., 0.2 M, 0.4 M, and 0.8 M, were used and ion-exchange (MIX) of iron and subsequent thermal treatment (MTH) were also applied. Surface properties of the modified carbons were analyzed by active surface area, pore volume, three-dimensional images, and chemical characteristics. The acidic and alkaline treatment changed the pore structures but yielded little improvement of adsorption capacities. As Fe concentrations were increased during impregnation, the active adsorption areas were decreased and the compositional ratios of Fe were increased. Adsorption capacities of modified ACs were evaluated using Langmuir isotherm. The MIX modification was not efficient to enhance 2,4-DCP adsorption and the MES treatment showed increases in adsorption capacities of 2,4-DCP, compared to the original activated carbon. These results implied a possibility of chemical impregnation modification for improvement of adsorption of 2,4-DCP, if a proper modification procedure is sought.

• Journal of Korean Society for Atmospheric Environment
• /
• v.25 no.2
• /
• pp.122-132
• /
• 2009

Adsorption of toluene by activated carbon fiber (ACF) coated with dielectric heating element and desorption by applying microwave were investigated. In order to prepare adsorbent so that VOC can be desorbed by microwave heating, fine dielectric heating element with nano size was coated on the surface of the ACF using hybrid binder. Eight adsorbents (ACF-DHE, Activated Carbon Fiber coated with Dielectric Heating Element) were prepared with different amount of dielectric heating element, kinds of hybrid binder, and solvent. In order to investigate adsorption characteristics, BET surface area, pore volume, and average pore size were measured for each adsorbent including ACF. Breakthrough experiments with toluene concentration, flow rate, bed length using fixed bed reactor were performed to investigate adsorbality of adsorbent, and results were compared with that of the ACF. Desorption reactor was constructed with modified microwave oven to investigate heating effect on ACF-DHE by applying microwave power. Each adsorbent saturated with toluene were put into desorption reactor. Composition of desorbed gas generated by applying controlled microwave power to reactor was measured. Up to now, hot air desorption method has been used. Experimental results showed that desorption method with new adsorbent prepared by coating dielectric heating element on ACF can be used for industrial application.

• Carbon letters
• /
• v.14 no.1
• /
• pp.27-33
• /
• 2013

An increase in population initiating rapid industrialization was found to consequently increase the effluents and domestic wastewater into the aquatic ecosystem. In this research the potentialities of Sambucus nigra L. (SNL) plant in the remediation of water, contaminated with methylene blue (MB), a basic dye were investigated. SNL was chemically impregnated with $KHCO_3$. Operating variables studied were pH, amount of adsorbent and contact time. In general, pH did not have any significant effect on colour removal and the highest adsorption capacity was obtained in 0.035 g MB/g-activated carbon. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich adsorption models were applied to describe the equilibrium isotherms. The adsorption isotherm data were fitted to the Temkin isotherm. The mass transfer property of the sorption process was studied using Lagergren pseudo-first-order and chemisorption pseudo-second-order kinetic models. The sorption process obeyed the pseudo-second-order kinetic model. The surface area, pores volume and diameter were assessed by the Brunauer-Emmett-Teller and Barrett-Joyner-Halenda methods. The results were compared to those from activated carbon (Merck) and an actual sample. The results indicate that SNL can be employed as a natural and eco-friendly adsorbent material for the removal of dye MB from aqueous solutions.

• Journal of Korean Society for Atmospheric Environment
• /
• v.25 no.4
• /
• pp.316-324
• /
• 2009

Carbon based sorbents for $CO_2$ adsorption were prepared by impregnation with alkali metals ($Li^+$, $K^+$) and alkaline earth metals ($Ca^{2+}$, $Mg^{2+}$). BET surface area of test sorbents was lower than the intrinsic activated carbon. In particular, impregnation of $Ca^{2+}$ or $Mg^{2+}$ resulted in lower surface area of specific adsorption sites than that of $Li^+$ or $K^+$. While the adsorption capacity for $CO_2$ was high in the sorbents containing $Ca^{2+}$ and $Mg^{2+}$, strong interaction with $CO_2$ would cause to drop the capacity after regeneration. The adsorption was found high relatively in the flow with a high concentration of $CO_2$ and in a low flow rate. The adsorption isotherm for the present modified AC sorbents fits well with the Freundlich model.

• Carbon letters
• /
• v.1 no.1
• /
• pp.6-11
• /
• 2000

Coal tar pitch was chemically modified with 10 wt% benzoquinone (BQ) to raise the softening point of isotropic pitch precursor and the precursor was melt-spun into pitch fibers, stabilized, carbonized and activated with steam at $900^{\circ}C$. The weight loss of carbon fiber-benzoquinone (CF-BQ) increased with the increase of activation time like other fibers, but was lower than those of Kureha fiber at the same activation time in spite of larger geometric surface area. Those adsorption isotherms fitted into 'Type I' according to Brunauer, Deming, Deming and Teller classification. However, there was very thin low-pressure hysteresis that lower closure points of the hysteresis are about 0.42-0.45. From the pore size distribution curves, there might be some micropores having narrow-necked bottle; a series of interconnected pore is more likely than discrete bottles. FT-IR studies showed that the functional groups such as carboxyl, quinone, and phenol were introduced to ACFs-BQ surface after steam activation. Methylene blue decolorization and iodine adsorption capacity of ACF-BQ increased linearly with the increase of specific surface area and was larger than that of ACF-Kureha at the same specific surface area.

• Carbon letters
• /
• v.8 no.3
• /
• pp.191-198
• /
• 2007

Recent studies have revealed the poisonous nature of aluminum(III) species to aquatic and terrestrial organisms. Therefore, this investigation aims to develop batch adsorption experiments in the laboratory, aiming to the removal of aluminum(III) from aqueous solutions onto powdered activated carbon (PAC). The latter (which is an effective and inexpensive sorbent) was prepared from olive stones generated as plant wastes and modified with an aqueous modifying oxidizing agent, viz. $HNO_3$. The main parameters (i.e. initial solution pH, sorbent and $Al^{3+}$ ions concentrations, stirring times and temperature) influencing the sorption process were examined. The results obtained revealed that the sorption of $Al^{3+}$ ions onto PAC is endothermic in nature and follows first-order kinetics. The adsorption data were well described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption models over the concentration range studied. Under the optimum experimental conditions employed, the removal of ca. 100% $Al^{3+}$ ions in the concentration range $1.35-2.75\;mg{\cdot}l^{-1}$ was attained. Moreover, the procedure was successfully applied to the recovery of aluminum spiked to some environmental water samples with an RSD (%), does not exceed 1.22%.

• Environmental Engineering Research
• /
• v.23 no.3
• /
• pp.301-308
• /
• 2018

We investigated simultaneous removal of heavy metals such as Cr, Ni, and Zn by adsorption onto powdered activated carbon (PAC) and PAC modified with sodium diethyldithiocarbamate (PAC-SDDC). Modification of PAC was confirmed by Fourier transform infrared spectroscopy and Scanning electron microscopy and energy dispersive X-ray spectroscopy. Both PAC and PAC-SDDC reached adsorption equilibrium within 48 h, and the adsorption kinetics followed a pseudo-second order reaction kinetics. The removal of metals was enhanced with increasing both adsorbent dosage and followed the descending order of Cr > Ni > Zn for PAC and Cr > Zn > Ni for PAC-SDDC, respectively. Adsorption kinetics followed pseudo-second order kinetics. Adsorption kinetic results were well fitted by the Freundlich isotherm except for Cr adsorption onto PAC. The optimum pH for heavy metal adsorption onto PAC was 5, whereas that for PAC-SDDC ranged from 7 to 9, indicating that modification of PAC with SDDC significantly enhanced heavy metal adsorption, especially under neutral and alkaline pH conditions. Our results imply that SDDC modified PAC can be applied to effectively remove heavy metals especially Cr in plating wastewaters without adjusting pH from alkaline to neutral.

• Journal of Environmental Science International
• /
• v.18 no.5
• /
• pp.501-508
• /
• 2009

In this study, the characteristics of granular activated carbon (GAC) supported metal was investigated in an area influenced by flame discharge and temperature variation during irradiating microwave. The modified GAC was formulated by impregnating metal hydroxides of nickel (Ni/GAC), barium (Ba/GAC), copper (Cu/GAC), zinc (Zn/GAC), cobalt (Co/GAC) and lanthanum (La/GAC). Ba/GAC was selected as it showed lack of spark discharge and temperature increasing aspects. Comparison of adsorption and desorption amount of GAC and Ba/GAC showed that adsorption and desorption rate of the GAC were higher than those of Ba/GAC. The results show that the presence of barium can decrease adsorption/desorption rate because of plugging pore of GAC. Toluene regeneration rate of Ba/GAC was better than that of GAC due to barium loading. Finally, GAC with barium can be controled a rapid increasing temperature and spark discharge, increased the regeneration rate of toluene during desorption by irradiating microwave.

• 한국생물공학회:학술대회논문집
• /
• 2000.04a
• /
• pp.414-417
• /
• 2000

BACC(Biological Activated Carbon Cartridge)process is a newly developed biological process to remove organic compounds, nitrogen, and phosphorus with activated carbon granules in iron fixed-frame cartridge type. The largest defect of previous BACC process was denitrification inefficiency. The removal efficiencies of nitrogen and phosphorous with external recycle ratios $100{\sim}200%$ for synthetic wastewater were $69.8{\sim}90.1%$ and $62.18{\sim}91%$, respectively, since the modified BACC process with external recycle overcame the defect of BACC process. When external recycle ratio was increased more than 300%, T-N removal efficiencies were decreased. In the treatment of a real sewage using modified BACC process, $COD_{Cr}$, removal efficiencies were $96.3{\sim}97.5%$ which was similar to those of the previous BACC process. while T-N removal efficiencies was $88.3{\sim}95.7%$ which were superior to those of the previous BACC process.