• Advances in environmental research
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• 제1권2호
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• pp.143-151
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• 2012

Nitrate removal from aqueous solution was investigated using $ZnCl_2$ and phosphoric acid activated carbon developed from pomegranate peel with particle size 0.4 mm. Potassium nitrate solution was used in batch adsorption experiments for nitrate removal from water. The effects of activated carbon dosage, time of contact, and pH were studied. The equilibrium time was fond to be 45 min. Two theoretical adsorption isotherms namely Langmuir and Freundlich were used to describe the experimental results. The Langmuir fit the isotherm with the theoretical adsorption capacity ($q_t$) was fond 78.125 mg g-1. Adsorption kinetics data were modeled using the pseudo-first, pseudo-second order, and intraparticle diffusion models. The results indicate that the second-order model best describes adsorption kinetic data. Results show activated carbon produced from pomegranate is effective for removal of nitrate from aqueous solution.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 추계학술대회
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• pp.196-201
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• 2000

The influence of adsorption on cadmium toxicity to soil microorganisms in smectite-rich soils and sediments was quantified as a function of solution and sorbent characteristics. Adsorption and surface complexation experiments were conducted to infer Cd sorption mechanisms to a reference smectite and three fractions of a Veritsol soil, and to elucidate the effects of the surface complexation on Cd bioavailability and toxicity in soils and sediments. Cadmium adsorption isotherms conformed to the Langmuir adsorption model, with adsorptive capacities of the different samples dependent on their characteristics. Equilibrium geochemical modeling (MINTEQA2) was used to predict the speciation of Cd in the soil suspensions using Langmuir and Triple Layer surface complexation models. The influence of adsorption and surface complexation on cadmium toxicity to soil microorganisms was assessed indirectly through the relative change in microbial hydrolysis of fluorescein diacetate (FDA) as a function of total Cd concentration and sorbent characteristics. Adsorption decreased the toxicity of Cd to soil microorganisms. Inner-sphere complexation is more effective than outer-sphere complexation in reducing the bioavailability and toxicity of heavy metals in soils and sediments.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.216-216
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• 2011

There have been various direct or indirect methods to measure the characteristics of plasma. Comparing to direct method like Langmuir probe method, indirect measurements which give information as some external parameters like current, voltage, or phase are easier to obtain. In this research, an indirect method to measure averaged plasma density in a transformer coupled plasma(TCP) has been proposed and evaluated. With a simple analytic model connecting electrical characteristics to plasma impedance, direct measurement via double Langmuir probe has been performed. This result may play a meaningful role to diagnose TCP or similar plasma sources

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.296-299
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• 1987

The purpose of this paper is to increase the lamp efficacy by filling the optimal Nitrogen gas pressure in the outer enclosure of metal halide lamp. This study presents a new model of Langmuir in the outer enclosure of discharge lamp. In this paper, in the first place, the diameter of Langmuir sheath and the total gab loss were calculated. Secondly, the each gas loss was computed if the arbitrary gas pressure is filled, With the calculated data, flash over which affects the lamp efficacy, lamp life and color rendering was considered. In case of the established discharge lamp, the gab pressure has been filled by experience only roughly. The gas loss is converted into the radiation output. Therefore, the lamp efficacy is improved by reducing the gas loss.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3391-3398
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• 2013

The carboxylated multiwall carbon nanotubes (MWCNT-COOH) and functionalized with isatin derivative (MWCNT-isatin) have been used as efficient adsorbents for the removal of lead (Pb) from aqueous solutions. The influence of variables including pH, concentration of the lead, amount of adsorbents and contact time was investigated by the batch method. The adsorption of the lead ions from aqueous solution by modified MWCNTs was studied kinetically using different kinetic models. The kinetic data were fitted with pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The sorption process with MWCNT-COOH and MWCNT-isatin was well described by pseudo-second-order and pseudo-first-order kinetics, respectively which it was agreed well with the experimental data. Also, it involved the particle-diffusion mechanism. The values of regression coefficient of various adsorption isotherm models like Langmuir, Freundlich and Tempkin to obtain the characteristic parameters of each model have been carried out. The Langmuir isotherm was found to best represent the measured sorption data for both adsorbent.

• 한국수처리학회지
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• 제26권6호
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• pp.143-152
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• 2018

The process parameters of ethyl violet from aqueous solution by activated carbon adsorption were carried out as a function of pH, temperature, contact time, initial concentration and temperature. The adsorption equilibrium data can be described well by the Langmuir and Freundlich isotherm models. Base on Langmuir constant ($R_L=0.0343{\sim}0.0523$) and Freundlich constant (1/n=0.1633~0.1974), This process could be employed as effective treatment for adsorption of ethyl violet. The kinetic experimental results showed that the adsorption process can be well described with the pseudo second order model. Based on the positive enthalpy (6.505 kJ/mol), the adsorption of ethyl violet onto granular activated carbon is endothermic. The negative Gibbs free energy (-1.169~-1.681 kJ/mol) obtained indicates that the adsorption process is spontaneous and physisorption.

• Journal of Astronomy and Space Sciences
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• 제15권2호
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• pp.401-415
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• 1998

1998년 6월 11일 오전 10시(KST)에 태안 반도(37。N, 126。E)에서 발사된 국산 로켓 KSR-II는 73km에서 130km고도에 걸쳐 전자 밀도, 전자 온도, 부동 전위 등을 관측하는데 성공하였다. 이 지역은 이온 층의 E-region에 해당하는 지역으로 전자 온도가 낮고 특히 Probe의 오염 효과에 의해 오차가 생길 수 있기 때문에 전자 온도에 대한 정확한 데이터를 얻기가 쉽지 않다. 본 실험에서 사용된 장비는 Langmuir Probe (LP)와 Electron Temperature Probe (ETP)로 두 가지 서로 다른 probe를 통해 얻은 전자 온도를 비교하여 검증된 전자 온도를 구할 수 있었다. 실험 결과 전자 밀도는 약 90km지점에서 급격히 증가하여 약 102km지점에서 최대 전자 밀도를 갖고 이 이상의 고도에서는 점차 감소하는 것으로 나타났다. 이는 최대 전자밀도가 110km에서 나타나는 IRI(International Reference Ionosphere)95-model이나 PIM(Parameterized Ionospheric Model)과 비교해 보면 다소 낮은 고도에서 최대 전자 밀도가 존재하였음을 알 수 있으며 측정된 값은 모델 계산에 비해 약간 큰 값을 갖는 것으로 나타났다. 한편 ETP로 측정된 전자 온도는 200$^{\circ}$K에서 700$^{\circ}$K에서 LP에 의한 교란 효과로 추정되는 요동현상을 보였으며 이를 제외하면 전자 온도가 고도에 따라 다소 증가하는 경향을 볼 수 있었다. LP를 통해 구한 전자 온도는 125km이상의 고도에서 ETP를 통하여 구한 전자 온도와 어는 정도 일치한다는 점에서 신뢰할 만한 측정값을 얻었다고 판단된다.

• 상하수도학회지
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• 제20권1호
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• pp.63-70
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• 2006

Biosorption characteristics were investigated at various temperature and pH conditions in order to establish lead(II) removal using Zoogloea ramigera 115SLR. Biosorption equilibrium isotherms and kinetics were obtained from batch experiments. The Freundlich and Langmuir model could be described the biosorption equilibrium of lead(II) on Z. ramigera 115SLR, Ca-alginate bead and immobilized Z. ramigera 115SLR. The maximum biosorption capacity of Z. ramigera 115SLR increased from 325 to 617mg $pb^{2+}/g$ biomass as temperature increased from 288.15 K to 308.15K from the Langmuir model. Fixed-bed column breakthrough curves for lead(II) removal were also obtained. For regeneration of the biosorbent, complete lead(II) desorption was achieved using 5mM HCl in fixed-bed column. This study shows the possibilities that well-treated immobilized Z. ramigera 115SLR with the mechanical intensity like TEOS (Tetraethyl orthosilicate) treatment and the optimum acid solution for desorption can be used for the effective treatment for lead(II) containing wastewater.

• 한국환경과학회지
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• 제27권6호
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• pp.401-410
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• 2018

Waste citrus peel-based activated carbon (WCAC) was prepared from waste citrus peels by activation with KOH. The removal of Cu and Pb ions from aqueous solution by the prepared WCAC was investigated in batch experiments. The solution pH significantly influenced Cu and Pb adsorption capacity and the optimum pH was 4 to 6. The adsorption of Cu and Pb ions by WCAC followed pseudo-second-order kinetics and the Langmuir isotherm model. The maximum adsorption capacity calculated by Langmuir isotherm model was 31.91 mg/g for Cu and 92.22 mg/g for Pb. As the temperature was increased from 303 K to 323 K, the ${\Delta}G^{\circ}$ value decreased from -7.01 to -8.57 kJ/mol for Cu ions and from -0.87 to -2.06 kJ/mol for Pb ions. These results indicated that the adsorption of Cu and Pb by WCAC is a spontaneous process.

• Environmental Engineering Research
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• 제16권2호
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• pp.55-60
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• 2011

The removal of hexavalent chromium from aqueous solutions onto modified holly sawdust was studied at varying initial hexavalent chromium concentrations, adsorbent doses, pHs and contact times. The removal of hexavalent chromium from aqueous solutions increased with increasing adsorbent dosage and contact time. The percentage of hexavalent chromium removed from the aqueous solutions decreased with increasing hexavalent chromium concentration and pH of the solution. The kinetics of the adsorption of hexavalent chromium onto modified holly sawdust was analyzed using pseudo first-order and pseudo second-order models. The pseudo second-order model described the kinetics of adsorption of hexavalent chromium. The Langmuir and Freundlich isotherm models were used for modeling of the adsorption equilibrium data. The Langmuir isotherm model well described the equilibrium data for the removal of hexavalent chromium by modified holly sawdust. The obtained maximum adsorption capacity was 18.86 mg/g at pH 7. The results showed that modified holly sawdust can be used as a low cost adsorbent for the treatment of aqueous solutions containing chromium.