• Environmental Engineering Research
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• 제15권4호
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• pp.207-213
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• 2010

This study investigated the potential of using bottom ash to be used as an adsorbent for the removal of lead (Pb) from aqueous solutions. The physical and chemical characteristics of bottom ash were determined, with a series of leaching and adsorption experiments performed to evaluate the suitability of bottom ash as an adsorbent material. Trace elements were present, such as silicon and aluminum, indicating that the material had a good adsorption capacity. All heavy metals leached during the Korea standard leaching test (KSLT) passed the regulatory limits for safe disposal, while batch adsorption experiments showed that bottom ash was capable of adsorbing Pb (experimental $q_e$ = 0.05 mg/g), wherein the adsorption rate increased with decreasing particle size. The adsorption data were then fitted to kinetic models, including Lagergren first-order and Pseudo-second order, as well as the Elovich equation, and isotherm models, including the Langmuir, Freundlich and Dubinin-Radushkevich isotherms. The results showed that pseudo-second order kinetics was the most suitable model for describing the kinetic adsorption, while the Freundlich isotherm best represented the equilibrium sorption onto bottom ash. The maximum sorption capacity and energy of adsorption of bottom ash were 0.315 mg/g and 7.01 KJ/mol, respectively.

• 한국지반환경공학회 논문집
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• 제10권7호
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• pp.25-32
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• 2009

본 연구는 팽창질석을 사용하여 수용액 상의 구리이온 흡착 제거능을 평가 하고자 하였다. 질석의 화학적 조성분석은 XRF, 구리이온 농도분석은 UV-VIS를 각각 사용하여 이루어졌다. 수용액 상의 구리이온의 제거양상을 살펴보기 위해 batch kinetic test와 batch sorption test가 실시되었고, 그 결과 구리의 제거속도($K_{obs}$, 1/hr)는 초기pH 3일때 0.73, pH 4일때 1.52, pH 5일때 1.71였고 초기농도가 $1mg\;L^{-1}$ 일때 3.19, 5일때 1.90, 10일때 0.73으로 초기구리농도와 반비례하고 초기 pH와는 비례하여 증가하는 양상을 보였다. 하지만 초기용액의 농도차이보다 초기pH의 영향이 지배적일 것이라는 예상하에 동일한 농도에 pH만 달리하여 실험해본 결과 역시 예상대로 pH에 따라 제거속도가 크게 차이남을 알 수 있었다. 최종적으로 batch sorption test를 통해 얻은 결과를 각각 Freundlich와 Langmuir 등온흡착식에 대입한 결과 두 식 모두 양호한 fitting 결과를 얻을 수 있었으나 Freundlich 식의 결정계수가 0.965로 Langmuir 식의 결정계수 0.936보다 좀 더 높게 나타나 좀 더 정확한 fitting 결과를 보여주었다. Langmuir 모델로부터 얻은 최대흡착용량($Q_{max}$), Freundlich 모델의 분배계수, n 값은 각각 $1,250mg\;kg^{-1}$, $635.1L\;kg^{-1}$, 1.69였다. 이러한 결과는 팽창질석이 다양한 형태의 수용액 상에 존재하는 구리이온을 효과적으로 제거할 수 있음을 보여준다.

• Environmental Engineering Research
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• 제11권1호
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• pp.1-13
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• 2006

In this study, conventional biofilters packed with flexible synthetic polyurethane (PU) foam carriers were operated to remove toluene from a contaminated air stream. PU foams containing various adsorbents (e.g., zeolite, sepiolite, dolomite and barite) were synthesized for the biofilter media and their adsorption characteristics of toluene were determined. Adsorption capacity of PU-adsorbent foam was in the order of PU-dolomite ${\approx}$ PU-zeolite > PU-sepiolite > PU-barite. During the biofiltration experiment, influent toluene concentration was in the range of 0-160 ppm and EBRT (i.e., empty bed residence time) was 45 seconds. Pressure drop of the biofilter bed was 4-5 mm $H_2O/m$ column height. The maximum removal capacity was in the order of PU-dolomite > PU-zeolite > PU-sepiolite > PU-barite, while the complete removal capacity was in the order of PU-dolomite > PU-sepiolite > PU-zeolite > PU-barite. The better biofiltration performance in PU-dolomite foam was because PU-dolomite foam had lower density and higher porosity than the others providing favorable conditions for microbial growth. The results of biodegradation kinetic analysis showed that PU-dolomite foam had higher maximum removal rate ($V_m\;=\;11.04\;g$ toluene/kg dry material/day) and saturation constant ($K_s\;=\;26.57\;ppm$) than the other PU foams. This supports that PU-dolomite foam was better than the others for biofilteration of toluene.

• Korean Journal of Chemical Engineering
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• 제35권12호
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• pp.2384-2393
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• 2018

Porous alginate-based hydrogel beads (porous ABH) have been prepared through a facile and sustainable template-assisted method using nano-calcium carbonate and nano-$CaCO_3$ as pore-directing agent for the efficient capture of methylene blue (MB). The materials were characterized by various techniques. The sorption capacities of ABH towards MB were compared with pure sodium alginate (ABH-1:0) in batch and fixed-bed column adsorption studies. The obtained adsorbent (ABH-1:3) has a higher BET surface area and a smaller average pore diameter. The maximum adsorption capacity of ABH-1:3 obtained from Langmuir model was as high as $1,426.0mg\;g^{-1}$. The kinetics strictly followed pseudo-second order rate equation and the adsorption reaction was effectively facilitated, approximately 50 minutes to achieve adsorption equilibrium, which was significantly shorter than that of ABH-1:0. The thermodynamic parameters revealed that the adsorption was spontaneous and exothermic. Thomas model fitted well with the breakthrough curves and could describe the dynamic behavior of the column. More significantly, the uptake capacity of ABH-1:3 was still higher than 75% of the maximum adsorption capacity even after ten cycles, indicating that this novel adsorbent can be a promising adsorptive material for removal of MB from aqueous solution under batch and continuous systems.

• 한국환경보건학회지
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• 제30권5호
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• pp.395-401
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• 2004

In this study, lots of methods have been studing to utilize energy and decrease contaminated effluents. There has been great progress on IGCC (Integrated gasification combined cycle) to reduce thermal energy losses. The following results have been conducted from desulfurization experiments using waste shell to remove $H_{2}S$. Unreacted core model ior desulfuriration rate prediction of sorbent was indicated. These were linear relationship between time and conversion. So co-current diffusion resistance was conducted reaction rate controlling step. The sulfidation rate is likely to be controlled primarily by countercurrent diffusion through the product layer of calcium sulfide(CaS) formed. Maximum desulfurization capacity was observed at 0.631 mm for lime, oyster and hard-shelled mussel. The kinetics of the sorption of $H_{2}S$ by CaO is sensitive to the reaction temperature and particle size at $800^{\circ}C$, and the reaction rate of oyster was faster than the calcined limestone at $700^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• 제29권10호
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• pp.1932-1936
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• 2008

A new analytical method using 1-(2-pyridylazo)-2-naphthol modified $SiO_2$ nanoparticles as solid-phase extractant has been developed for the preconcentration of trace amounts of mercury(II) in different water samples. Conditions of the analysis such as preconcentration time, effect of pH, sample volumes, shaking time, elution conditions and effects of interfering ions for the recovery of analyte were investigated. The adsorption capacity of nanometer $SiO_2$-PAN was found to be 260 ${\mu}molg^{-1}$ at optimum pH and the detection limit (3$\sigma$) was 0.48 ${\mu}gL^{-1}$. The extractant showed rapid kinetic sorption. The adsorption equilibrium of mercury(II) on nanometer $SiO_2$-PAN was achieved just in 5 mins. Adsorbed mercury(II) was easily eluted with 5 mL of 6 M hydrochloric acid. The maximum preconcentration factor was 50. The method was applied for the determination of trace amounts of mercury(II) in various water samples and industrial effluents.

• Nuclear Engineering and Technology
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• 제49권3호
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• pp.534-540
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• 2017

The adsorption of uranium (VI) by calcium alginate beads was examined by batch experiments. The effects of environmental conditions on U (VI) adsorption were studied, including contact time, pH, initial concentration of U (VI), and temperature. The alginate beads were characterized by using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. Fourier transform infrared spectra indicated that hydroxyl and alkoxy groups are present at the surface of the beads. The experimental results showed that the adsorption of U (VI) by alginate beads was strongly dependent on pH, the adsorption increased at pH 3~7, then decreased at pH 7~9. The adsorption reached equilibrium within 2 minutes. The adsorption kinetics of U (VI) onto alginate beads can be described by a pseudo first-order kinetic model. The adsorption isotherm can be described by the Redlich-Peterson model, and the maximum adsorption capacity was 237.15 mg/g. The sorption process is spontaneous and has an exothermic reaction.

• 한국광물학회지
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• 제25권4호
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• pp.185-195
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• 2012

나노 크기 매킨나와이트(FeS)는 높은 환원력, 흡착성, 그리고 비표면적을 지니고 있어, 염소유기물의 분해와 중금속 및 비금속의 제거에 유용하다. 하지만 매킨나와이트 나노입자는 콜로이드 안정성(colloid stability)의 변화로 지하수 흐름에 따라 쉽게 확산되거나, 입자집적(particle aggregation)에 의해 대수층의 공극을 막을 수 있다. 따라서 투과반응벽(permeable reactive barrier)에 적용하기 위해서 적절한 공학적 변형이 필요하다. 본 연구에서는 코팅법을 적용해 나노크기 매킨나와이트를 변형시킴으로써 본래의 반응성을 유지하고 또한 경제적인 투과반응벽의 설치에 활용하고자 한다. 이를 위해 화학적 처리를 하지 않은 규사(non-treated silica sand, NTS)와 화학적 처리에 의해 불순물이 제거된 규사(chemically treated silica sand, CTS)를 사용해 매킨나와이트를 코팅시켰다. 두 규사 모두 약 pH 5.4에서 매킨나와이트가 최대로 코팅되었으며, 이 pH는 (1) 매킨나와이트의 용해도, (2) 규사 및 매킨나와이트의 표면전하(surface charge)에 의해 영향받았다. 최적 pH에서 NTS와 CTS에 의한 코팅량은 각각 0.101 mmol FeS/g, 0.043 mmol FeS/g으로, NTS 표면에 존재하는 산화철 등의 불순물에 의해 매킨나와이트의 코팅이 현저히 증가했다. 한편 혐기성 조건에서 코팅되지 않은 규사 2종과 최적 pH에서 코팅된 규사 2종을 이용해 아비산염(arsenite)의 흡착실험을 실시했다. pH 7에서 코팅되지 않은 NTS와 코팅된 NTS에 의한 아비산염의 상대적 제거율은 아비산염의 초기 농도에 따라 달라졌다. 낮은 농도에서 코팅되지 않은 NTS가 높은 아비산염의 제거율을 보였으나, 높은 농도에서는 코팅된 NTS가 상대적으로 높은 제거율을 보였다. 이런 차이는 아비산염은 낮은 농도에서 규사 표면에 존재하는 산화물과의 표면배위결합(surface complexation)에 의해 제거되었고, 높은 농도에서 코팅된 매킨나와이트와 반응해 황화비소(arsenic sulfides)로 침전되었기 때문이다. pH 7에서 코팅된 NTS에 비교해 코팅된 CTS는 현저히 낮은 아비산염 제거율을 보였는데, 이는 CTS의 상대적으로 낮은 매킨나와이트 코팅량에 기인했다. 따라서 코팅된 NTS는 코팅된 CTS보다 아비산염의 제거를 위한 투과반응벽의 설치에 더 적합한 물질이며, 특히 아비산염의 오염도가 심한 지하수의 복원에 유용하게 적용될 수 있다.

• 대한환경공학회지
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• 제37권4호
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• pp.210-217
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• 2015

Red mud의 염산처리와 열처리에 의한 불소의 제거 특성을 살펴보고자 동역학적 흡착, 평형흡착, pH, 흡착제의 주입량에 따른 흡착특성, 그리고 칼럼을 이용한 연속식 조건에서의 불소흡착 특성을 살펴보았다. Red mud의 산처리는 HCl 0.8 M 농도에서 효과적이었고, 열처리 온도가 높음에 따라 흡착량이 감소하였다. 0.8 M로 산처리한 Red mud (0.8 M-ATRM)의 동역학적실험 결과 초기농도 50 mg-F/L는 30분대에 평형농도에 도달하였고, 초기농도 500 mg-F/L에서는 1시간대 흡착평형을 나타내었다. 0.8 M-ATRM은 단층흡착을 가정한 Langmuir 모델에 잘 부합하였고, 최대흡착량($Q_m$)은 23.162 mg/g으로 나타났다. 또한 낮은 pH에서 높은 불소 흡착경향을 나타내었다. 이는 높은 pH에서 불소와 $OH^-$가 경쟁관계를 형성하기 때문으로 판단된다. 0.8 M-ATRM의 주입량이 증가 할수록 제거율은 높아졌지만, 단위질량당 흡착량은 감소하였다. 본 연구에서 사용된 0.8 M-ATRM은 가격이 저렴할 뿐만 아니라 불소에 높은 흡착능을 나타내어 수중 불소 제거에 효과적인 흡착소재로 판단된다.

• Environmental Engineering Research
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• 제20권1호
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• pp.73-78
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• 2015

The aim of this study was to examine the phosphate (P) removal by quintinite from aqueous solutions. Batch experiments were performed to examine the effects of reaction time, temperature, initial phosphate concentration, initial solution pH and stream water on the phosphate adsorption to quintinite. Kinetic, thermodynamic and equilibrium isotherm models were used to analyze the experimental data. Results showed that the maximum P adsorption capacity was 4.77 mgP/g under given conditions (initial P concentration = 2-20 mgP/L; adsorbent dose = 1.2 g/L; reaction time = 4 hr). Kinetic model analysis showed that the pseudo second-order model was the most suitable for describing the kinetic data. Thermodynamic analysis indicated that phosphate sorption to quintinite increased with increasing temperature from 15 to $45^{\circ}C$, indicating the spontaneous and endothermic nature of sorption process (${\Delta}H^0=487.08\;kJ/mol$; ${\Delta}S^0=1,696.12\;J/(K{\cdot}mol)$; ${\Delta}G^0=-1.67$ to -52.56 kJ/mol). Equilibrium isotherm analysis demonstrated that both Freundlich and Redlich-Peterson models were suitable for describing the equilibrium data. In the pH experiments, the phosphate adsorption to quintinite was not varied at pH 3.0-7.1 (1.50-1.55 mgP/g) but decreased considerably at a highly alkaline solution (0.70 mgP/g at pH 11.0). Results also indicated that under given conditions (initial P concentration=2 mgP/L; adsorbent dose=0.8 g/L; reaction time=4 hr), phosphate removal in the stream water (1.88 mgP/g) was lower than that in the synthetic solution (2.07 mgP/g), possibly due to the presence of anions such as (bi)carbonate and sulfate in the stream water.