• Journal of Soil and Groundwater Environment
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• v.25 no.1
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• pp.95-105
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• 2020

In this study, iron nanoparticles impregnated hydrochar (FeNPs@HC) was synthesized using lignocellulosic waste and simple one-pot synthetic method. During hydrothermal carbonization (HTC) process, the mixture of lignocellulosic waste and ferric nitrate (0.1~0.5 M) as a precursor of iron nanoparticles was added and heated to 220℃ for 3 h in a teflon sealed autoclave, followed by calcination at 600℃ in N₂ atmosphere for 1 h. For the characterization of the as-prepared materials, X-ray diffraction (XRD), cation exchange capacity (CEC), fourier transform infrared spectrometer (FT-IR), Brunauer-Emmett-Teller (BET), transmission electron microscope (TEM), Energy Dispersive X-ray Spectroscopy (EDS) were used. The change of Fe(III) concentration in the feedstock influenced characteristics of produced FeNPs@HC and removal efficiency towards As(V) and Pb(II). According to the Langmuir isotherm test, maximum As(V) and Pb(II) adsorption capacity of Fe_0.25NPs@HC were found to be 11.81 and 116.28 mg/g respectively. The results of this study suggest that FeNPs@HC can be potentially used as an adsorbent or soil amendment for remediation of groundwater or soil contaminated with arsenic and cation heavy metals.

• Korean Journal of Materials Research
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• v.20 no.4
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• pp.199-203
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• 2010

Hybridization of semiconductor materials with carbon nanotubes (CNTs) is a recent field of interest in which new nanodevice fabrication and applications are expected. In this work, nanowire type GaAs structures are synthesized on porous single-wall carbon nanotubes (SWCNTs) as templates using the molecular beam epitaxy (MBE) technique. The field emission properties of the as-synthesized products were investigated to suggest their potential applications as cold electron sources, as well. The SWCNT template was synthesized by the arc-discharge method. SWCNT samples were heat-treated at $400^{\circ}C$ under an $N_2/O_2$ atmosphere to remove amorphous carbon. After heat treatment, GaAs was grown on the SWCNT template. The growth conditions of the GaAs in the MBE system were set by changing the growth temperatures from $400^{\circ}C$ to $600^{\circ}C$. The morphology of the GaAs synthesized on the SWCNTs strongly depends on the substrate temperature. Namely, nano-crystalline beads of GaAs are formed on the CNTs under $500^{\circ}C$, while nanowire structures begin to form on the beads above $600^{\circ}C$. The crystal qualities of GaAs and SWCNT were examined by X-ray diffraction and Raman spectra. The field emission properties of the synthesized GaAs nanowires were also investigated and a low turn-on field of $2.0\;V/{\mu}m$ was achieved. But, the turn-on field was increased in the second and third measurements. It is thought that arsenic atoms were evaporated during the measurement of the field emission.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.2
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• pp.136-142
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• 2012

Various factors affecting on the bioassay were investigated. Experiments with a low mixture ratio (cell to toxicant solution) of 0.5 : 9.5 (v/v) produced observable bioluminescence intensity for assay. Both sodium lactate and potassium nitrate stimulate bioluminescence activity; 2.6~4.0 times of control. Distilled water and MSM, which gave non significant effects on the bioluminescence activity, were determined as proper diluent or extract solutions. A wide range of toxic responses of metals and organics were observed. In general, organics were much less sensitive than metals. Samples collected from eleven sites showed the bioluminescence activity ranging from 29 to 111% of the control. Significant correlation between toxicity and total metal contents was not observed, but the toxicity of two groups, sorted based on the contaminated arsenic concentration in soils, was 44% and 20%, showing considerable differences.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.264-269
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• 2001

Large amounts of orange juice are produced in Japan every yea.. Accompanied by the production of orange juice, large amount of juice residues are also generated in nearly the same amounts with juice. Although, at present, some of these residues are marketed as a feed for cattle after drying and mixing with lime, the marketing price is lower than its production cost and the difference is paid by the consumers as a part of the price of orange juice. In the present work, we developed new innovative use of orange juice residue, a biomass waste, as adsorption gel for removing toxic heavy metals such as lead. arsenic, selenium and so on as well as radioactive elements such as uranium and thorium from environments. The major components of orange juice residue are cellulose. hemicellulose and pectin, which are converted into pectic. acid, an acidic polysaccharide, by means of saponification with concentrated sodium hydroxide solution. In the previous work, we found that crosslinked pectic acid gel strongly an selectively adsorbs lead over other metals such as zinc an copper. On the other hand. it is well known that polysaccharides such as cellulose can be easily phosphorylated and that phosphorylated polysaccharides have high affinity to uranium and thorium as well as some trivalent metals such as ferric iron and aluminum. Taking account of the noticeable characteristics of these polysaccharides, 2 types of adsorption gels were prepared from orange juice residue: one is the gel which was prepared by saponificating the residue followed by crosslinking with epichlorohydrin and another is that prepared by crosslinking the residue followed by phosphorylation. The former gel exhibited excellent adsorptive separation behavior for lead away from zinc owing to high content of pectic acid while the latter gel exhibited that for uranium and thorium. Both types of adsorption gels exhibited high affinity to ferric iron, which enables selective and strong adsorption for some toxic oxo-anions of arsenic (V and III), . selenium and so on via iron loaded on these gels. These results demonstrate that biomass wastes such as orange juice residue can be effectively utilized fer the purpose of removing toxic heavy or radioactive metals existing in trace or small amounts in environments.

• Journal of the Korean Wood Science and Technology
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• v.33 no.6 s.134
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• pp.87-94
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• 2005

This study was carried out to investigate the effect of soil types and soil properties on wood preservative leaching. Radiata pine (Pinus radiata Don.) sapwood stakes, which had been treated with 2.0%(w/v) CCA, were leached for 12 weeks by a common laboratory method in four different soils and for 14 days by the AWPA standard leaching method in water. The physical and chemical properties of the four soils were determined, and the percent leaching of the individual component of CCA was correlated with the various soil properties. The data show that leaching of preservative chemicals from treated wood exposed to soil is influenced by the type of soil. The preservative leaching was greater when wood was exposed to water than when the wood was in contact with water-saturated soil. The greatest chromium, copper and arsenic leaching from CCA-treated stakes were observed in the sandy loam, loam, and sand, respectively, and the least amount of leaching of CCA components occurred in the silty loam. The leaching of preservative components from treated wood is extremely complex and appears to be influenced differently by the soil properties. The extent of copper leaching from CCA treated wood appears to be related to exchangeable Mg and sum of bases. There is a reasonably good relationship between chromium leaching and exchangeable Mg, and between arsenic leaching and exchangeable K, soil Ni, Mn, Fe, Cr, or Cu content. Since this study was conducted based on laboratory leaching method using small cross-sectional dimensions; thus, data obtained from this experiment should not be used to predict leaching characteristics from commercial-size wood used in real situation. Accordingly, further studies are necessary using outdoor ground-contact leaching.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.1
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• pp.9-18
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• 2017

Arsenic (As) has been considered as the most toxic one among various hazardous materials and As contamination can be caused naturally and anthropogenically. Major forms of arsenic in groundwater are arsenite [(As(III)] and/or arsenate [(As(V)], depending on redox condition: arsenite and arsenate are predominant in reduced and oxidized environments, respectively. Because arsenite is much more toxic and mobile than arsenate, there have been a number of studies on the reduction of its toxicity through oxidation of As(III) to As(V). This study was initiated to develop photocatalytic oxidation process for treatment of groundwater contaminated with arsenite. The performance of two types of light sources (UV lamp and UV LED) was compared and the feasibility of goethite as a photocatalyst was evaluated. The highest removal efficiency of the process was achieved at a goethite dose of 0.05 g/L. Based on the comparison of oxidation efficiencies of arsenite between two light sources, the apparent performance of UV LED was inferior to that of UV lamp. However, when the results were appraised on the basis of their emitting UV irradiation, the higher performance was achieved by UV LED than by UV lamp. This study demonstrates that environmentally friendly process of goethite-catalytic photo-oxidation without any addition of foreign catalyst is feasible for the reduction of arsenite in groundwater containing naturally-occurring goethite. In addition, this study confirms that UV LED can be used in the photo-oxidation of arsenite as an alternative light source of UV lamp to remedy the drawbacks of UV lamp, such as long stabilization time, high electrical power consumption, short lifespan, and high heat output requiring large cooling facilities.

• Journal of the Korean Wood Science and Technology
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• v.33 no.3 s.131
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• pp.53-63
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• 2005

This study attempted to obtain the basic data of utilizable possibility of preservative treated wood as a material used in a marine ranch. To evaluate the leaching stability of CCA-, CCFZ-, and ACQ-treated woods in seawater, the specimens treated with 2% and 3% (w/v) of CCA, CCFZ, and ACQ were exposed to deionized water, synthetic seawater and natural seawater for 41 days and then each component released was periodically determined. There was little amount of copper and chromium released from CCA-treated wood exposed in both deionized and seawater. Although relatively large amount of arsenic was released from CCA-treated wood, the release rate in seawater was lower than that in deionized water. The release rate of chromium and zinc from CCFZ-treated wood were somewhat greater in deionized water, but lower in seawater than in deionized water. Retention level and salinity of synthetic seawater had little effect on the release rate of components. The ACQ-treated wood had greater copper release than CCA- and CCFZ-treated wood, and the amount of copper released did not affected by leaching media used.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.300.2-300.2
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• 2014

테라헤르쯔(terahertz : THz)파는 0.1~10 THz 의 범위로 적외선과 방송파 사이에 광대역 주파수 스펙트럼을 차지하고 있으며 직진성, 투과성, 그리고 낮은 에너지(meV)를 가지고 있어 비 파괴적이고 무해한 장점을 지니고 있다. Ti:sapphire laser와 같은 femto-pulse source 등이 많은 발전이 되어 현재 많은 연구와 발전이 이루어지고 있다. femto-pulse source를 이용한 THz 응용에서는 높은 저항, 큰 전자이동도, 그리고 아주 짧은 전하수명의 기판을 요구하는데 저온에서 성장한(low-temperature grown : LT) InGaAs는 격자 내에 Gallium 자리에 Arsenic이 치환 하면서 AsGa antisite가 발생하여 전하수명을 짧아지는 것을 응용하여 가장 많이 이용되고 있다. 본 연구에서는 보다 높은 저항을 얻기 위하여 molecular beam epitaxy를 이용하여 semi-insulating InP:Fe 기판위에 격자 정합된 LT-InGaAs:Be/InAlAs multi quantum well (MQW)를 well과 barrier를 가각 $10{\mu}m$ 씩 100주기 성장을 하였고 Ti와 Au를 각각 30, $200{\mu}m$로 dipole antenna를 제작 하였다. 이 때 Ti:sapphire femto-pulse laser (30 fs/90 MHz)를 excitation source로 사용하였을 때 9000 pA로 LT-InGaAs epilayer (180 pA)보다 50배 이상 큰 전류 신호를 얻을 수 있었다. THz 발생과 검출을 초소형, 초경량, 고효율로 하기 위해서는 fiber-optic를 이용해야 하는데 이때 분산과 산란 손실이 가장 적은 1550 nm 대역에서 많은 연구가 이루어 졌다. 780, 1560 nm의 mode-locking laser (90 fs/100 MHz)를 사용하여 현재 많이 이용되고 있는 Ti:sapphire femto-pulse laser와 비교하여 THz 특성 변화를 확인하는 연구를 진행 하고 있다.

• Environmental Engineering Research
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• v.25 no.4
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• pp.579-587
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• 2020

Novel silane grafted bentonite was obtained using the natural bentonite as precursor material. The material which is termed as nanocomposite was characterized by the Fourier Transform Infra-red (FT-IR) and X-ray diffraction (XRD) methods. The surface imaging and elemental mapping was performed using Scanning Electron Microscopic (SEM/EDX) technique. The electroanalytical studies were performed using the nanocomposite electrode. The electroactive surface area of nanocomposite electrode was significantly increased than the pristine bentonite or bare carbon paste based working electrode. The impedance spectroscopic studies were conducted to simulate the equivalent circuit and Nyquist plots were drawn for the carbon paste electrode and nanocomposite electrodes. A single step oxidation/reduction process occurred for As(III) having ΔE value 0.36 V at pH 2.0. The anodic stripping voltammetry was performed for concentration dependence studies of As(III) (0.5 to 20.0 ㎍/L) and reasonably a good linear relationship was obtained. The detection limit of the As(III) detection was calculated as 0.00360±0.00002 ㎍/L having with observed relative standard deviations (RSD) less than 4%. The presence of several cations and anions has not affected the detection of As(III) however, the presence of Cu(II) and Mn(II) affected the detection of As(III). The selectivity of As(III) was achieved using the Tlawng river water sample spiked with As(III).

• The Journal of Engineering Geology
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• v.16 no.2 s.48
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• pp.153-159
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• 2006

The discharges of time, technology and finance was increased and it was difficult to use water resources effectively by serious water pollutions. Thus the main aim of this work was focused on effectiveness of water treatment process using non-controlled indicators such as UV absorbance($E_{260}$) and particle counts that provided analytical results with simple and rapid. The soluble aluminum was increased by the increase of aluminum doses for turbidity removals It means that the water quality was not controlled by only turbidity monitoring cause maximum turbidity removal did not guarantee minimum residual aluminum in an aluminum-based coagulation. E removal efficiency appeared to be the promising indicator for monitoring the effectiveness of the water quality process such as coagulation and nanofiltration membranes for arsenic(V). On the basis of the particle monitoring, it was also found that the particle counts could be used very useful for changing the coagulants in real water treatments.