• 한국물환경학회지
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• 제35권2호
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• pp.123-130
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• 2019

Ethylenediaminetetraacetic acid-modified bentonite (EMB) was used for adsorption of zinc ion (Zn) from aqueous solution, compared with unmodified bentonite (UB). Parameters such as dose (0.750 ~ 3.125 g/L), mixing intensity (10 ~ 150 rpm), contact time (0.17 ~ 30 min), pH (2 ~ 7), and temperature (298 ~ 338 K), were studied. Zn removal efficiency for EMB was 20 ~ 30 % higher, than that for UB, in all experiments. Thermodynamic studies demonstrated that adsorption process was spontaneous with Gibb's free energy (${\Delta}G$) values, ranging between -5.211 and -7.175 kJ/mol for EMB, and -0.984 and -2.059 kJ/mol for UB, and endothermic with enthalpy (${\Delta}H$) value of 9.418 kJ/mol for EMB and 7.022 kJ/mol for UB. Adsorption kinetics was found to follow the pseudo-second order kinetics model, and its rate constant was 3.41 for EMB and $2.00g/mg{\cdot}min$ for UB. Adsorption equilibrium data for EMB were best represented by the Langmuir adsorption isotherm, and calculated maximum adsorption capacity was 2.768 mg/g. It was found that the best conditions for Zn removal of EMB within the range of operation used, were 3.125 g/L dose, 90 rpm intensity, 10 min contact time, pH 4, and 338 K. Therefore, EMB has good potential for adsorption of Zn.

• 한국지하수토양환경학회지:지하수토양환경
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• 제14권1호
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• pp.78-82
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• 2009

본 연구에서는 철도 아연유래 토염토양을 정화하기 위해 토양세척과 토양세정의 타당성은 연구하였다. 무기산인 HCI및 $H_3PO_4$와 유기산인 citric acid및 ethylene diamine tetraacetic acid(EDTA)을 이용하여 토양세척을 수행하였다. 일반적으로 중금속 오염토양에 대하여 세척효율이 우수하다고 알려진 DETA는 본 오염 토양의 세척에는 효과적이지 않았다. 무기산 중에는 HCI이 34%의 아연 제거율로 가장 우수한 효과를 보였으며, 0.1 M HCI이상을 사용하는 것은 효과적이지 않았다. 또한 연속세척을 통하여 아연의 제거율을 향상시킬수 있었다. 칼럽실험에서 아연의 평균제거율은 27% 이였으며, 토양 내 아연 잔류농도는 기준치 이하인 662mg/kg까지 감소하였다.이와 같은 실험 결과를 바탕으로 HCI을 이용한 토양 세척 및 토양 세정을 이용하여 철도유래 아연 모염토양 정화가 충분히 가능한 것으로 판단된다.

• 한국환경보건학회지
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• 제20권1호
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• pp.62-67
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• 1994

ZnO-$Fe_2O_3$ 복합금속 산화물 흡착제가 황화수소 제거능이나 황화된 흡착제의 산화적 재생반응에 미치는 영향을 고찰하였다. Zinc ferrite 흡착제가 가장 높은 황화수소 제거능을 나타내었고 혼합한 $Fe_2O_3$ 흡착제는 황화반응 도중 H$_2$S의 생성을 촉진시킴을 알 수 있었다. 또한 황화반응의 결과로 생성되는 금속황화물들이 H$_2$S 열분해의 촉매로 작용하였으며 H$_2$는 $Fe_2O_3$의 함량이 증가할수록 더 많이 발생하였다. 산화적 재생반응의 결과로부터 ZnS를 제외하고 $Fe_2O_3$를 혼합한 흡착제는 모두 잘 재생됨을 알 수 있었다. 또한 산화적 재생반응 도중 생성될 수 있다고 보고된 zinc sulfate는 생성되지 않았다. 그리고 SO$_2$ 발생 곡선의 형태나 완전재생에 소요되는 시간을 기준으로 판단해 볼 때 $Fe_2O_3$의 혼합량의 변화는 산화적 재생반응에 별다른 영향을 미치지 않음을 알 수 있었다.

• 한국물환경학회지
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• 제26권4호
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• pp.687-690
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• 2010

The objective of this study is to investigate the effect of aldehyde compounds and ploysulfide as accelerating agents on removal of heavy metals and CN in plating wastewater. As a results of the experiments, the removal efficiency of cyanide using the formaldehyde type of aldehydes was the highest at pH 9. Next types were sodium formaldehyde bisulfite addut> paraldehyde> paraformaldehyde. Also, optimum pH and dosage for treating the residual heavy metals by using polysulfide were pH 9 and 30 mg/L, respectively. The removal efficiencies of cyanide, chromium, zinc and copper were above 96.7% at optimum condition.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.267.2-267.2
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• 2016

Semiconductor photo-catalysis offers the potential for complete removal of toxic chemicals through its effective and broad potential applications. Various new compounds and materials for chemical catalysts were synthesized in the past few decades. As one of the most important II-VI group semiconductors, zinc sulfide (ZnS) with a wide direct band gap of 3.8 eV has been extensively investigated and used as a catalyst in photochemistry, environmental protection and in optoelectronic devices. In this work, the ZnS films and nanostructures have been successfully prepared by wet chemical method. We show that the agglomerates with four successive scales are always observed in the case of the homogeneous precipitation of zinc sulfide. Hydrodynamics plays a crucial role to determine the size of the largest agglomerates; however, other factors should be invoked to interpret the complete structure. In addition, studies of the photocatalytic properties by exposure to UV light irradiation demonstrated that ZnS nanocrystals (NCs) are good photo-catalysts as a result of the rapid generation of electron-hole pairs by photo-excitation and the highly negative reduction potentials of excited electrons. A combination of their unique features of high surface-to volume ratios, carrier dynamics and rich photo-catalytic suggests that these ZnS NCs will find many interesting applications in semiconductor photo-catalysis, solar cells, environmental remediation, and nano-devices.

• Restorative Dentistry and Endodontics
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• 제6권1호
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• pp.37-50
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• 1980

Scanning Electron Microscopic (SEM) examination on the labial surface of 91 permanent upper incisors were made after etching procedure with phosphoric acid, sulfuric acid, nitric acid, hydro chloric acid, oxalic acid, formic acid, citric acid and zinc phosphate liquid for 2 minutes. Following results were obtained. 1. In the surfaces etched by 10%. 50% phosphoric acid, 50% sulfuric acid, 10%. 30% nitric acid, 10%. 50% oxalic acid, 10%. 30%. 50% formic acid, 30%. 50% citric acid and zinc phosphate liquid, there appeared to be a preferential removal of prism cores, but in the surfaces etched by 10% phosphoric acid, 50% nitric acid, 10%. 30% hydrochloric acid and 30% oxalic acid, the prism peripheries were removed preferentially. 2. According to Silverstone classification on enamel etching pattern the surface treated by zinc phosphate liquid, 30. 50% citric acid, 10%. 30%. 50% formic acid, 10%. 50% oxalic acid, 10%. 30% nitric acid, 50% sulfuric acid and 10%. 50%. phosphoric acid showed Type 1, and etched by 30% oxalic acid, 10%. 30% hydrochloric acid, 50% nitric acid and 10% phosphoric acid showed Type II. Etching of prism cores was by far the most common occurence. The changes produced could be related to intrinsic differences in histology and / or solubility of enamel.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1992년도 수공학연구발표회논문집
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• pp.325-328
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• 1992

The purpose of this research is to develop the technique of heavy metal removal from wastewater. The research is divided into two parts, one part uses complex precipitation and the other uses adsorption. In the first part of the study, humic acid is used as the complex agent, humic acid is a polyelectrolyte with a high complexation affinity. Lead, copper, zinc and cadmium were studied for their complex precipitation efficiencies. In the batch studies, humic acid was effective in removing 100% of the lead and 48.2% of the copper respectively from wastewater without anytreatment. The efficiency of cadmium and zinc, however, was very low. In the second part of the study, wastewater is introduced at the top of a silicagel adsorption column and then bottom effluent concentration is analyzed. The results of the analysis are used to draw a breakthrough curve.

• Nuclear Engineering and Technology
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• 제15권2호
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• pp.149-153
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• 1983

흡착 기포 분리에 의하여 수용액으로부터 아연(II)을 회수하는 방법에 관하여 연구하였다. 그리고 흡착 기포 분리에서 용매부선 과정과 거품 분별 과정에 채용되었고 이들 분리 과정에서 카프르산을 아연의 회수 물질로 사용하였다. 이온 강도 및 수소이온의 농도가 분리 과정의 효율에 어떤 영향을 미치는지를 기술하였으며, 추출제로 벤젠에 녹은 카프르산을 이용한 용매 추출과정과도 상호 비교하였다.

• Environmental Engineering Research
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• 제25권2호
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• pp.258-265
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• 2020

Heavy metal removal by using porous mineral adsorbents bears a great potential to decontaminate sludge compost, and natural zeolite (NZ), artificial zeolite (AZ), and expanded perlite (EP) seem to be possible candidates for this purpose. A composting experiment was conducted to compare the efficiency of those adsorbents for removal of iron (Fe), manganese (Mn), chromium (Cr), copper (Cu), zinc (Zn), nickel (Ni), and lead (Pb) from sewage sludge compost with no adsorbent amendment. For this purpose, 10 g of NZ and AZ and 5 g of EP was filled in a small bag made from non-biodegradable synthetic textile and was separately mixed in composting piles. The bags were separated from compost samples at the end of the experiment. AZ and NZ exhibited different reduction potentials depending on the type of heavy metal. AZ significantly reduced Cr (43.7%), Mn (35.8%), and Fe (29.9%), while NZ more efficiently reduced Cu (24.5%), Ni (22.2%), Zn (22.1%), and Pb (21.2%). The removal efficiency of EP was smaller than both AZ and NZ. The results of this simultaneous composting and metal removing study suggest that AZ and NZ can efficiently bind metal during composting process.

• 상하수도학회지
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• 제13권2호
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• pp.47-54
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• 1999

SRB(Sulfate Reducing Bacteria) converts sulfate into sulfide using an organic carbon source as the electron donor. The sulfide formed precipitates the various metals present in the AMD (Acid Mine Drainage). This study is the fundamental research on heavy metal removal from AMD using SRB. Two completely mixed anaerobic reactors were operated for cultivation of SRB at the temperature of $30^{\circ}C$ and anaerobic batch reactors were used to evaluate the effects of carbon source, COD/sulfate($SO_4^=$) ratio and alkalinity on sulfate reduction rate and heavy metal removal efficiency. AMD used in this study was characterized by low pH 3.0 and 1000mg/l of sulfate and dissolved high concentration of heavy metals such as iron, cadmium, copper, zinc and lead. It was found that glucose was an organic carbon source better than acetate as the electron donor of SRB for sulfate reduction in AMD. Amount of sulfate reduction maximized at the COD(glucose)/sulfate ratio of 0.5 in the influent and then removal efficiencies of heavy metals were 97.5% of Cu, 100% of Pb, 100% of Cr, 49% of Mn, 98% of Zn, 100% Cd and 92.4% of Fe. Although sulfate reduction results in an increase in the alkalinity of the reactor, alkalinity of 1000mg/1 (as $CaCo_3$) should be should be added continuously to the anaerobic reactor in order to remove heavy metals from AMD.