• 상하수도학회지
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• 제37권6호
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• pp.375-382
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• 2023

The binary oxide adsorbent using Fe and Mn (Fe-Mn) has been prepared by precipitation method to enhance the removal of phosphate. Different amounts of chitosan, a natural organic polymer, were used during preparation of Fe-Mn as a stabilizer to protect an aggregation of Fe-Mn particles. The optimal amount of chitosan has been determined considering the separation of the Fe-Mn particles by gravity from solution and highest removal efficiency of phosphate (Fe-Mn10). The application of Fe-Mn10 increased removal efficiency at least 15% compared to bare Fe-Mn. According to the Langmuir isotherm model, the maximum uptake (q_m) and affinity coefficient (b) were calculated to be 184 and 240 mg/g, and 4.28 and 7.30 L/mg for Fe-Mn and Fe-Mn10, respectively, indicating 30% and 70% increase. The effect of pH showed that the removal efficiency of phosphate was decrease with increase of pH regardless of type of adsorbent. The enhanced removal efficiency for Fe-Mn10 was maintained in entire range of pH. In the kinetics, both adsorbents obtained 70% removal efficiency within 5 min and 90% removal efficiency was achieved at 1 h. Pseudo second order (PSO) kinetic model showed higher correlation of determination (R²), suggesting chemisorption was the primary phosphate adsorption for both Fe-Mn and Fe-Mn10.

• 한국산학기술학회논문지
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• 제15권4호
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• pp.2029-2035
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• 2014

본 논문은 입상활성탄에 의해서 합성폐수에서의 용존유기탄소의 흡착평형과 회분식 실험을 통해 흡착성질을 파악하고자 하였다. 흡착평형의 새로운 모델식을 제안하였고 이 식을 바탕으로 회분식 실험데이터를 모사하였다. 합성폐수의 유기성분은 Beef extract, Peptone, Humic acid, Tannic acid, Sodium lignin sulfonate, Sodium lauryle sulfate, Arabic gum powder, Arabic acid (polysaccharide), $(NH_4)_2SO_4$, $K_2HPO_4$, $NH_4HCO_3$, $MgSO_4{\cdot}7H_2O$ 등으로 구성되었다. 농도가 낮은 영역 (0~2.5 mg/L)에서는 선형적인 흡착평형을 보여주었고, 농도가 높은 영역 (2.5~6mgl/L)에서는 우호적인 흡착평형을 보여주었다. 사용되어진 생물학적 처리방법에서 나오는 유출수의 합성폐수는 알려진 양으로 준비되어졌다. 흡착평형 모델링은 Freundlich, Langmuir, Sips 및 하이브리드 식을 이용하여 모사하였다. 특히, 선형과 Sips를 이용한 하이브리드 흡착평형식은 낮은 농도와 높은 농도 역에서 매우 좋은 흡착평형식이었다. 용수 및 폐수처리에 활성탄 흡착에 있어서, 선형식과 Sips식을 합친 새로운 하이브리드 식은 새로운 흡착평형식이 될 수 있었다. 하이브리드 흡착평형식 (선형+Sips)을 이용하여 LDFA 운동학적식을 통하여 다양한 흡착제 양에 따른 회분식 반응조에서의 실험데이터를 잘 모사할 수 있었다.

• 자원환경지질
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• 제51권2호
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• pp.87-97
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• 2018

세슘은 물속에서 고상보다는 이온이나 착염 등 용존 형태로 존재하는 특성이 강하여, 오염 수계로부터 세슘 제거가 어려운 것으로 알려져 있다. 최근 많은 연구들이 수계 내에서 세슘의 제거효율이 높은 흡착제를 개발하는데 집중하고 있다. 본 연구에서는 대나무 활성탄을 흡착제로 사용하여 수계 내에 존재하는 세슘을 효과적으로 제거하는 실내실험을 실시하였다. 수용액으로부터 대나무 활성탄의 세슘 제거효율을 측정하고, 최적의 세슘 제거능을 가지는 흡착 조건을 도출하고자 다양한 조건에서 흡착 배치실험을 수행하였다. 국내에서 유통되고 있는 5 종류의 대나무 활성탄의 표면 특성을 SEM-EDS와 XRD 분석으로 규명하였으며, 이 중에서 비표면적이 큰 3 종류의 대나무 활성탄을 대상으로 세슘 제거 배치실험을 실시하였다. 다양한 초기 세슘 농도를 가지는 인공수(0.01~10 mg/L 범위)를 대상으로 대나무 활성탄에 의한 수용액 내 세슘 제거량을 측정하여 제거효율을 계산하였고, 두 종류의 흡착 등온식들을 흡착 배치실험 결과에 대응시켜 흡착 상수값을 결정함으로서, 대나무 활성탄의 세슘 흡착 특성을 규명하였다. FE-SEM 분석 결과, 대나무 활성탄은 표면이 다수의 기공을 포함하는 대나무의 섬유질 조직을 그대로 유지하는 입자들로 구성되어, 이들 섬유질 조직 내 다양한 형태의 기공들과 엽상조직 표면들이 주요 세슘 흡착공간인 것으로 밝혀졌다. 흡착 배치실험 결과, C type 대나무 활성탄의 세슘 제거효율이 가장 높았는데, 특히 수용액의 세슘 초기 농도가 1.0 mg/L 이하인 경우에도 75 % 이상(최고 82 %)을 나타내어, 원전사고 등에 의해 오염된 현장 지하수나 지표수(해수 포함)의 세슘농도가 대부분 1.0 mg/L 이하임을 고려하면, 실제 오염수 정화 가능성이 높을 것으로 밝혀졌다. 수용액의 온도는 $5-15^{\circ}C$ 범위, pH는 3-11 범위에서 높은 세슘 제거효율이 일정하게 유지되는 것으로 나타나 다양한 오염수에 적용할 수 있을 것으로 판단되었다. 흡착 배치실험 결과는 Langmuir 흡착모델과 유사하였으며, C type 대나무 활성탄의 최대흡착농도($q_m:mg/g$)값은 63.4 mg/g으로 기존의 상용화된 흡착제 값보다 높았고, 수용액의 초기 세슘 농도가 1.0 mg/L이하인 경우 표면흡착률(surface coverage) 값도 낮게 유지되어, 적은 양의 세슘으로 오염된 수계를 효과적으로 정화할 수 있음을 입증하였다.

• ETRI Journal
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• 제30권3호
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• pp.383-393
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• 2008

The etching mechanism of $ZrO_2$ thin films and etch selectivity over some materials in both $BCl_3$/Ar and $BCl_3/CHF_3$/Ar plasmas are investigated using a combination of experimental and modeling methods. To obtain the data on plasma composition and fluxes of active species, global (0-dimensional) plasma models are developed with Langmuir probe diagnostics data. In $BCl_3$/Ar plasma, changes in gas mixing ratio result in non-linear changes of both densities and fluxes for Cl, $BCl_2$, and ${BCl_2}^+$. In this work, it is shown that the non-monotonic behavior of the $ZrO_2$ etch rate as a function of the $BCl_3$/Ar mixing ratio could be related to the ion-assisted etch mechanism and the ion-flux-limited etch regime. The addition of up to 33% $CHF_3$ to the $BCl_3$-rich $BCl_3$Ar plasma does not influence the $ZrO_2$ etch rate, but it non-monotonically changes the etch rates of both Si and $SiO_2$. The last effect can probably be associated with the corresponding behavior of the F atom density.

• KSBB Journal
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• 제14권5호
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• pp.611-615
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• 1999

우리나라 인근 해역에서 가장 쉽게 채취할 수 있는 해조류 중의 하나인 S. sagamianum을 이용한 Pb의 생체흡착 실험을 수행하였다. Pb는 1시간 내에 흡착 평형에 도달하였으며, Pb의 평형흡착량은 각각 224.5 mg Pb/g biomass 였다. Pb 흡착시에 경금속인 Ca 및 Mg가 500 mg/L 이하로 존재할 때 Ca는 약간 흡착되었으나 Mg는 전혀 흡착되지 않아 Pb만을 선택적으로 제거하는 것이 가능하였다. Pb 흡착 후에 0.1M HCl, 0.1M HNO$_3$,0.1M EDTA 및 0.1 M NaOH를 이용하여 탈착 실험을 수행하고 다시 재흡착을 시키는 과정을 6회 반복한 결과, 탈착율은 EDTA가 100%로 가장 높았으나, S. sagamianum의 재생성을 고려해 볼 때 HNO$_3$및 HCl가 효과적인 탈착 용액인 것으로 사료되었다. 특히 HNO$_3$를 이용하였을 때 Pb의 누적흡착량이 736.8 mg/g biomass로서 가장 높은 것을 알 수 있었다. 이러한 결과로 부터 S. sagamianum 은 매우 우수한 생체흡착제로 연속공정에 사용이 가능할 것으로 사료되었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제17권2호
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• pp.47-53
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• 2012

In this study, the adsorption of $Cu^{2+}$ and $Cd^{2+}$ from aqueous solution on the biochar derived from used coffee grounds at different pyrolysis temperatures has been investigated as a potential low-cost treatment method for heavy metal-containing waters. Three biochar samples prepared by heating coffee sludge at temperature of $300^{\circ}C$ (B300), $500^{\circ}C$ (B500), and $700^{\circ}C$ (B700) were tested for the adsorption capacity and kinetics of Cd and Cu. Also the influencing factor of heavy metal removal by ion exchange in terms of cation exchange capacity (CEC) of each biochar was measured. Adsorption of Ca and Cu by biochar produced at higher pyrolysis temperature showed higher adsorption capacity but the optimal pyrolysis temperature based on performance and economy was known as $500^{\circ}C$. Sorption of Cu and Cd by biochar followed a Langmuir model at pH 6~6.5, attributing mainly to surface sorption. The biochar was more effective in Cu and Cd sorption than activated carbon (AC), with BC 500 being the most effective, which indicates that sorption of Cd and Cu by coffee sludge biochar is partly influenced by chemical sorption on surface functional group as well as physical sorption.

• Journal of Applied Biological Chemistry
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• 제51권1호
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• pp.28-35
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• 2008

The physico-chemical properties of kapok fibers were altered via the combination processes of chlorite-periodate oxidation, in order to assess their efficacy as a heavy metal adsorbent. The chemically-oxidized kapok fibers were found to harbor a certain amount of polysaccharides, together with lowered lignin content. This alteration in lignin characteristics was clearly confirmed via FTIR and NBO yield. Moreover, chemically oxidized kapok fibers retained their hollow tube shape, although some changes were noted. The chemically oxidized kapok fibers evidenced elevated ability to adsorb heavy metal ions with the best fit for the Langmuir adsorption isotherm model. Three cycles of adsorption-desorption were conducted with in-between regeneration steps. Our experimental results indicated that chemically oxidized kapok fibers possessed excellent adsorption characteristics, and the modified kapok fibers could be completely regenerated with almost equimolar diluted sodium hydroxide. Pb, Cu, Cd and Zn ions evidenced adsorption rates of 93.55%, 91.83%, 89.75%, and 92.85% on the chemically oxidized kapok fibers. The regeneration efficiency showed 73.58% of Pb, 71.55% of Cu, 66.87% of Cd, and 75.00% of Zn for 3rd cycle with 0.0125N NaOH.

• Journal of Microbiology and Biotechnology
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• 제21권2호
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• pp.147-153
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• 2011

Bacillus species have been involved in metal association as biosorbents, but there is not a clear understanding of this chelating property. In order to evaluate this metal chelating capacity, cultures and spores from Grampositive bacteria of species either able or unable to produce surface layer proteins (S-layers) were analyzed for their capacity of copper biosorption. Only those endowed of S-layers, like Bacillus sphaericus and B. thuringiensis, showed a significant biosorption capacity. This capacity (nearly 50%) was retained after heating of cultures, thus supporting that structural elements of the envelopes are responsible for such activity. Purified S-layers from two Bacillus sphaericus strains had the ability to biosorb copper. Copper biosorption parameters were determined for strain B. sphaericus 2362, and after analyses by means of the Langmuir model, the affinity and capacity were shown to be comparable to other bacterial biosorbents. A competitive effect of $Ca^{2+}$ and $Zn^{2+}$, but not of $Cd^{2+}$, was also observed, thus indicating that other cations may be biosorbed by this protein. Spores that have been shown to be proficient for copper biosorption were further analyzed for the presence of S-layer content. The retention of S-layers by these spores was clearly observed, and after extensive treatment to eliminate the S-layers, the biosorption capacity of these spores was significantly reduced. For the first time, a direct correlation between S-layer protein content and metal biosorption capacity is shown. This capacity is linked to the retention of S-layer proteins attached to Bacillus spores and cells.

• Carbon letters
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• 제28권
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• pp.87-95
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• 2018

This study examined the influence of operating parameters on the electrosorptive recovery system of lithium ions from aqueous solutions using a spinel-type lithium manganese oxide adsorbent electrode and investigated the electrosorption kinetics and isotherms. The results revealed that the electrosorption data of lithium ions from the lithium containing aqueous solution were well-fitted to the Langmuir isotherm at electrical potentials lower than -0.4 V and to the Freundlich isotherm at electrical potentials higher than -0.4 V. This result may due to the formation of a thicker electrical double layer on the surface of the electrode at higher electrical potentials. The results showed that the electrosorption reached equilibrium within 200 min under an electrical potential of -1.0 V, and the pseudo-second-order kinetic model was correlated with the experimental data. Moreover, the adsorption of lithium ions was dependent on pH and temperature, and the results indicate that higher pH values and lower temperatures are more suitable for the electrosorptive adsorption of lithium ions from aqueous solutions. Thermodynamic results showed that the calculated activation energy of $22.61kJ\;mol^{-1}$ during the electrosorption of lithium ions onto the adsorbent electrode was primarily controlled by a physical adsorption process. The recovery of adsorbed lithium ions from the adsorbent electrode reached the desorption equilibrium within 200 min under reverse electrical potential of 3.5 V.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제10권S_2호
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• pp.79-88
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• 2001

Humic acids react with chlorine to produce Trihalomethanes(THMs), known as carcinogens, during disinfection, the last stage in water purification. Currently, the removal of organic humic acids is considered the best approach to solve the problem of THM formation. Accordingly, the current study examined the adsorption of organic compounds of humic acids onto an inorganic carrier prepared from oyster shell waste. The adsorbent used was activated oyster shell powder(HAP) and silver ion-exchanged oyster shell powder(HAP-Ag), with CaCO$_3$ as the control. The adsorbates were phthalic acid, chelidamic acid, catechol, dodecylpyridinium chloride(DP), and 2-ethyl phenol(2-EP). The adsorption experiments were carried out in a batch shaker at $25^{\circ}C$ for 15 hours. The equilibrium concentration of the adsorbate solution was analyzed using a UV spectrophotometer and the data fitted to the Langmuir isotherm model. Since the solution pH values were found to be greater than the pKa values of the organic compounds used as adsorbates, the compounds apparently existed in ionic form. The adsorptive affinities of the organic acid and phenolic compounds varied depending on the interaction of electrostatic forces, ion exchange, and chelation. More carboxylic acids and catechol, rather than DP and 2-EP, were adsorbed onto HAP and HAP-Ag. HAP and HAP-Ag exhibited a greater adsorptive affinity for the organic compounds than CaCO$_3$, used as the control.