The adsorption of Acid Blue 92 onto three low cost and ecofriendly biosorbents viz., cow dung ash, mango stone ash and parthenium leaves ash and commercial activated carbon have discussed in this work. The ash of all the mentioned bio-wastes was prepared in the muffle furnace at 500oC and all the adsorbents were stored in an air thermostat. Experiments at total dye concentrations of 10~100 mg/L were carried out with a synthetic effluent prepared in the laboratory. The parameters such as pH and dye concentration were varied. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms. The results indicate that cow dung ash, mango stone ash and parthenium leaves ash could be employed as low-cost alternatives to commercial activated carbon in wastewater treatment for the removal of dye.
The synthesis of C60@MWCNT was carried out at room temperature (~25℃) from arc-discharge prepared Multi-wall carbon nanotubes (MWCNTs). They were oxidized and acid treated for tube opening. Then C60 molecules were encapsulated into MWCNTs by wetting them with C60-toluene solution for several minutes followed by ultrasonification. C60@MWCNT was cleaned by pure toluene to remove any excess C60. C60@MWCNT was characterized by electron microscopy, which showed large scale filling of C60 into MWCNTs. It was observed that the mechanism of insertion of C60 into MWCNTs may be due to the capillary suction at the opening ends of MWCNTs.
Coconut shell activated carbon (CSAC) was investigated for its ability in the removal of two neutral chlorinated organic compounds,namely trichloroethylene (TCE) and dichloromethane (DCM) from aqueous solution using a packed bed column. The efficiency of the prepared activated carbon was also compared with a commercial activated carbon (CAC). The important design parameters such as flow rate and bed height were studied. In all the cases the lowest flow rate (5 mL/min) and the highest bed height (25 cm) resulted in maximum uptake and per cent removal. The experimental data were analysed using bed depth service time model (BDST) and Thomas model. The regeneration experiments including about five adsorption-desorption cycles were conducted. The suitable elutant selected from batch regeneration experiments (25% isopropyl alcohol) was used to desorb the loaded activated carbon in each cycle.
The precipitation polymerization of acrylonitrile (AN) was carried out in a mixture solution of dimethyl sulfoxide (DMSO) and water at 50~65oC using α,α’-azobisisobutyronitrile (AIBN) as an initiator. The increased molecular weight polyacrylonitrile (PAN) was prepared with increasing the H2O/DMSO ratio from 10/90 to 80/20. The viscosity average molecular weight of H2O/DMSO solvent was 4.4 times larger than that of H2O/DMF solvent, and precipitation polymerization was accelerlated due to the far decreased chain transfer effect of DMSO. Based on the experimental results,the increased PAN molecular weight was regarded as the summation of two mechanisms: i) particle-particle aggregation and ii) particle-radical attachment. The theoretical equation derived from the mechanisms was well coincided with the experimental results showing the linear relationship between the viscosity average molecular weight and the H2O/DMSO ratio.
In this study, TiO2-Activated carbon (AC) complex fibers were prepared by electrospinning for the synergetic effect of adsorption and degradation of organic pollutant. The average diameter of these fibers increased with increasing the amount of AC added, except for 1AC-TOF (AC/TiO2 =1/40 mass ratio). After calcinations at 500oC, long as-spun fibers were broken and their average diameter was slightly decreased. The resultant fibers after calcination had rough surface and sphere shapes like a peanut. From XRD results, it was confirmed that as-spun fibers were changed to anatase TiO2 fiber after calcinations at 500oC. The prepared TiO2-AC complex fibers could remove procian blue dyes by solar light irradiation with high removal property of 94~99%. The PB dye was rapidly removed by adsorption during the initial 5 minutes. But after 5 minutes, dye removal was occurred by photodegradation. In this study, the most efficient AC/TiO2 ratio of TiO2-AC complex fibers was 5/40, showing the synergetic effect of adsorption and photodegradation. It is expected that the TiO2-AC complex fibers can be used to remove of organic pollutants in water system.
In this work, graphite nanofibers (GNFs) were prepared by ammonia and heat treatment at temperatures up to 1000oC to improve its CO2 adsorption capacity. The effects of the heat treatment on the textural properties and surface chemistry of the GNFs were investigated by N2 adsorption isotherms, XRD, and elemental analysis. We found that the chemical properties of GNFs were significantly changed after the ammonia treatment. Mainly amine groups were formed on the GNF surfaces such as lactam groups, pyrrole and pyridines. The GNFs treated at 500oC showed highest CO2 adsorption capacity of 26.9 mg/g at 273 K in this system.
Carbon supported electrocatalysts are commonly used as electrode materials for polymer electrolyte membrane fuel cells(PEMFCs). These kinds of electrocatalysts provide large surface area and sufficient electrical conductivity. The support of typical PEM fuel cell catalysts has been a traditional conductive type of carbon black. However, even though the carbon particles conduct electrons, there is still significant portion of Pt that is isolated from the external circuit and the PEM,resulting in a low Pt utilization. Herein, new types of carbon materials to effectively utilize the Pt catalyst are being evaluated.
Carbon nanofiber/activated carbon fiber (CNF/ACF) composite with multifunctional surfaces were prepared through catalytic growth of CNFs on ACFs. Nickel nitrate was used as a precursor of the catalyst to synthesize carbon nanofibers(CNFs). CNFs were synthesized by pyrolysising CH4 using catalysts dispersed in acetone and ACF(activated carbon fiber). The as-prepared samples were characterized with transmission electron microscopy(TEM), scanning electron microscopy(SEM). In TEM image, carbon nanofibers were synthesized on the ACF to form a three-dimensional network. Pt/CNF/ACF was employed as a catalyst for PEMFC. As the ratio of prepared catalyst to commercial catalyst was changed from 0 to 50%, the performance of the mixture of 30 wt% of Pt/CNF/ACF and 70wt% of Pt/C commercial catalyst showed better perfromance than that of 100% commercial catalyst. The unique structure of CNF can supply the significant site for the stabilization of Pt particles.
CNF/ACF is expected to be promising support to improve the performance in PEMFC.
화석원료의 고갈에 대비한 수소생산용 원자로건설에 대한관심이 전세계적으로 높아지고 있다. 원자로를 이용한 수소생산은 고온으로 수증기를 가열하여 열분해를 통해 수소를 생산하는 방식으로 기존 원자로가 발생하는 800oC 보다 높은1000oC 부근의 온도를 요구하고 있어 고온가스냉각반응로에대한 다양한 형태의 원자로가 거론이 되고 있다. 따라서 이에적합한 새로운 개념을 갖는 원자로에 대한 연구가 진행되고있고 이와 같이 원자로 사용 재료에 대한 연구 또한 진행되고있다. 고온가스냉각반응로에 사용되는 재료는 고온물성과 중성자에 안정한 재료가 요구되며 흑연은 이에 부합하는 최고의재료로 원자로 내부와 지지체 등에 상당량이 사용이 예상된다.
흑연은 핵분열시 발생하는 중성자에 견디는 능력이 여타 재료에 비해 매우 탁월하고 반응속도를 늦쳐주는 감속재, 그리고중성자를 내부로 제한하는 반사체로 매우 효과적인 재료이다 .