• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.90-95
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• 2022

In the present work, biochar was prepared using Achyanthes japonica stem as a by-product of herbal medicine. In order to apply the prepared biochar to water treatment process, the adsorption characteristics of zinc and iron ions dissolved in water were investigated. When the experiments were performed for 2 h to remove 70 and 100 mg/L of zinc ions, the adsorption amounts of 32.3 and 31.0 mg/g were obtained, respectively. It was also found that the adsorption amount of Achyanthes japonica stem biochar for the removal process of zinc ion was three times higher than that of the activated carbon. In addition, when the experiments were performed for 2 h to treat 70 and 100 mg/L of iron ions, high adsorption amounts of 50.1 and 54.3 mg/g were achieved, respectively. In order to further enhance the removal efficiency of zinc and iron ions, a steam activation process was performed on the biochar of Achyanthes japonica stem. As a result, the removal efficiencies of 70 and 100 mg/L of zinc ions increased to 80 and 60%, respectively. Also, the removal efficiencies of 70 and 100 mg/L of iron ions were improved to 100 and 82%, respectively. In addition, when the biochar of Achyanthes japonica stem with a steam activation was compared with the untreated biochar of Achyanthes japonica stem, the specific surface area increased 37.3 times, and the total and macroporpous pore volumes were improved by 28.4 and 136 times, respectively. Therefore, the results can be used for economically and practically adsorbing zinc and iron ions contained in water.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.239-246
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• 2010

When galvanized steel strip is produced through a continuous hot-dip galvanizing process, the thickness of the adhered zinc film is controlled by impinging a thin plane nitrogen gas jet. The thickness of the zinc film is generally affected by impinging pressure distribution, its gradient and shearing stress at the steel strip. These factors are influenced by static pressure of gas spraying at air knife nozzle, a nozzle-to-strip distance and strip and a geometric shape of the air knife, as well. At industries, galvanized steel strip is produced by changing static pressure of gas and a distance between the air knife nozzle and strip based on experimental values but remaining a geometric shape of nozzle. Splashing and check-mark strain can generally occur when a distance between the air knife nozzle and strip is too short, while ability of zinc removal can lower due to pressure loss of impinging jet when a distance between the air knife nozzle and strip is too long. In present study, buckling of the jet and change of static pressure are observed by analyzing flow characteristics of the impinging jet. The distance from the nozzle exit to the strip varies from 6 mm to 16 mm by an increment of 2 mm. Moreover, final coating thickness with change of a distance between the air knife nozzle and strip is compared with each case. An ability of zinc removal with the various distances is predicted by numerically calculating the final coating thickness.

• Membrane and Water Treatment
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• v.13 no.3
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• pp.129-137
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• 2022

In this study, the removal of Ciprofloxacin (CPX) from aqueous solutions was investigated by a new activated carbon adsorbent prepared from orange peel (ACOP) with chemical activation using ZnCl₂. The physicochemical properties of orange peel activated carbon were characterized by proximate and ultimate analysis, scanning electron microscopy, BET surface area determination and Fourier transformation infrared spectroscopic studies. According to Brunauer-Emmett-Teller isotherm and non-local-density functional theory, the cumulative surface area, pore volume and pore size of ACOP were determined as 1193 m² g^-1, 0.83 cc g^-1 and 12.7 Å, respectively. The effects of contact time, pH, temperature and ACOP dose on the batch adsorption of CPX were studied. Adsorption equilibrium data of CPX with ACOP were found to be compatible with both the Langmuir and Freundlich isotherms. CPX adsorption capacity of ACOP was calculated as 181.8 mg g^-1 using Langmuir isotherm. The CPX adsorption kinetics were found to be harmonious with the pseudo-second-order kinetic model. Conclusively, ACOP can be assessable as an effective adsorbent for the removal of ciprofloxacin (CPX) from aqueous solutions.

• Journal of the Korean Applied Science and Technology
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• v.33 no.3
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• pp.441-448
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• 2016

Heavy metal removal study is conducted from synthetic waste water by reduction and oxidation(redox) reaction of Cu-Zn metal alloy and adsorption reaction of aluminium silicate. Heavy metal whose ionization tendency is smaller than zinc are reducted in an aqueous solution, and the concentration of ionized zinc is reduced by adsorption reaction. The average diameter of metal alloy micro fiber is about $200{\mu}m$, and the surface area is wide enough to get equilibrium in a single cycle treatment. A single cycle treatment of redox reaction of Cu-Zn metal alloy, could remove 100.0 % of Cr(III), 98.0 % of Hg, 92.0 % of Sn and 91.4 % of Cu respectively. An ionization tendency of chromium is very close to zinc, but removal efficiency of chromium by redox reaction is significant. This result shows that trivalent chromium ion is expected to generate hydroxide precipitation with $OH^-$ ion generated by redox reaction. Zinc ion generated by redox reaction is readily removed by adsorption reaction of aluminium silicate in a single cycle treatment. Other heavy metal components which are not perfectly removed by redox reaction also showed very high removal efficiency of 98.0 % or more by adsorption reaction. Aluminium ion is not increased by adsorption reaction of aluminium silicate. That means heavy metal ion removal mechanism by adsorption reaction is turned out to be not an ion exchange reaction, but an adsorption reaction.

• Journal of Soil and Groundwater Environment
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• v.15 no.3
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• pp.27-33
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• 2010

The purpose of this study was in search of native plant species showing metal-resistant property and excessively accumulating heavy metals in metal-contaminated soil or abandoned mines as well as in evaluation of applicability of phytoremediation. In the study area, species showing excessively accumulating heavy metals were a shepherd´s purse, pampas grass, a Korean lettuce, a Hwansam vine, the Korean persicary, a foxtail, a goosefoot, and a water pepper. The first screened plant species in Sambo mine were as shepherd's purse, Korean lettuce and pampas grass Among them the shepherd´s purse can be excluded because it is a seasonal plant and has lower removal capacity for heavy metals. The Korean lettuce was also excluded because of having lower removal capacity for heavy metals. Pampas grass is a highly bionic plant species constantly growing from spring. However it has weak points such as little accumulation capacity for zinc as well as small values of an accumulation factor and a translocation factor. Another problem is regarded as removal of roots after the clean up if pampas grass is applied to a farmland. In Sanyang mine, wormwood and Sorijaengi were considered as adaptable species.

• Membrane and Water Treatment
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• v.14 no.3
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• pp.121-128
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• 2023

This study introduces a NaOH/Zn-assisted hydrothermal method for the synthesis of zeolites derived from coal ash (CA). A zeolite/Zn adsorbent is successfully prepared by the activation of CA with NaOH and Zn; it is characterized by a high surface area and a negative surface charge.Methylene blue (MB) and methyl orange (MO) are selected as dye pollutants, and their adsorption onto the zeolite/Zn adsorbent is investigated. Results show the high adsorption capacities of MB and MO and that the negative surface charge facilitates electrostatic interactions between the adsorbates and adsorbents. The zeolite/Zn adsorbents shows the selective adsorption of positively charged dye MB via electrostatic interactions between the =NH+ group (positive dipole) and the oxygen functional group of the adsorbents (negative dipole). The selectivity for the positively charged dye is sufficiently high, with the removal efficiency reaching 99.41% within 10 min. By contrast, the negatively charged dye MO exhibits negligible absorption. These findings confirm the role of electrostatic interactions in the adsorption of MB, in addition to the effect of a large surface area. The results of this study are expected to facilitate the development of simple, eco-friendly, and cost-effective zeolite-based adsorptive composites from CA residuals for the selective removal of dye pollutants from CA waste.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.6
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• pp.465-476
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• 2021

Scale and rust generation in water pipes is a common phenomenon when cast iron water pipes have been used for a long time. A physical water treatment device is known among various means for suppressing rust in a water pipe, and a zinc ionization device for putting zinc metal into a pipe and emitting the zinc cation into water is one of such devices. This research measured the amount of zinc ion generated, which is known to exhibit an effect of inhibiting rust and scale generation in a pipe, and examined the scale and rust inhibition effect of the ionization device installed for ground or building water supply. In the case of distilled water, the concentration of zinc ion increased by circulating water in the ionization device several times, and it was verified to be hundreds of ㎍/L, and in the case of discharging ground or tap water, it was verified to be tens of ㎍/L. In addition, a verification pipe was installed to confirm the change inside the pipe before and after installation of the zinc ionization device, and the internal condition of the pipe was observed 3 months to several years after installation. It was confirmed that the corrosion area of the surface of the pipe was no longer increased by installing a corrosion inhibitor, and if the pipe was already filled with corrosion products, the amount of corrosion products gradually decreased every year after installation. The phenomenon of fewer corrosion products could be interpreted as expanding the space in the pipe due to the corrosion product as Fe₂O₃ adhered to the inner surface of the pipe and turned into a smaller black Fe₃O₄. In addition, we found that scale such as CaCO₃ together in the corrosion by-products gradually decreased with the attachment of the ionization device.

• Journal of environmental and Sanitary engineering
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• v.22 no.4
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• pp.1-9
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• 2007

A wastewater treatment plant, operating process is physico-chemical/biological activated sludge attached sand filtration, was selected to evaluate effluent quality and pollutants removal efficiencies consideration for deriving the technology-based effluent limitation for petroleum refining industry discharge. The results of influent and effluent analysis were as follows: Average effluent quality were 0.076mg/l of copper, 0.084mg/l of lead, 0.036mg/l of zinc, 0.005mg/l of nickel and 0.004mg/l of cadmium, and the range of coefficient of reliability from 0.007 of copper to 1.0 of lead. Also, 95% of reliability, 0.112, 0.15, 0.063, 0.015 and 0.009mg/l, respectively, were remarkably lower than their effluent limitations. And to reach 95% reliability of effluent limitation at cleanness area, designed effluent quality of copper, lead, zinc and cadmium should be 0.268, 0.099, 0.526 and 0.008mg/l, respectively.

• Journal of Environmental Impact Assessment
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• v.19 no.4
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• pp.443-452
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• 2010

본 연구에서는 도시지역의 하나인 주거지역에서 배출되는 강우유출수 내에 중금속이 장치형 비점 오염저감시설 중에 하나인 와류형시설에서 제거되는 특성을 파악하고자, 대상 중금속을 Zn으로 삼고 2007년 4월부터 2008년 11월까지 모니터링을 수행하였다. 유출수 모니터링은 와류형 시설의 유입부와 유출부에서 유량과 수질을 각각 시간변화에 따라 측정하였으며, 시설유입부와 유출부, 그리고 시설하부에 쌓인 침전물을 채취하여 침전물 모니터링도 수행하였다. 그 결과, 높은 강우강도에서 발생된 강우유출수는 와류형 시설내에 HRT를 감소시켜 Zn의 제거효율이 낮게 관측되었으며, 특히 HRT가 20분이내의 조건이 될 경우에는 처리효과가 없는 것으로 확인되었다. Zn는 입자성물질과 밀접한 관계를 맺으며 제거되는 특성을 보였으며, 입자성물질이 스크린에 의한 여과 및 침전작용이 일어날 때 입자성물질에 부착되어 거동하는 특성을 보였다. 그 중에 0.075mm 이하의 미세한 입자에 부착된 고농도의 Zn는 제거되지 못하였고, 와류형 시설 후단에 후처리시설로서 저류시설을 두어 충분한 HRT를 제공한 결과, 와류형 시설만을 운전하였을 때와 비교하여 높은 제거특성을 보이게 되었다.

• Restorative Dentistry and Endodontics
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• v.8 no.1
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• pp.45-51
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• 1982

An endodontically treated tooth is likely to be brittle than a vital tooth. Internal structure of the tooth has been weakened due to a significant removal of dentin by coronal access, canal preparation. There are many controversies concerning with various methods of reinforcing an intact anterior tooth that has endodontic treatment. In this experiment, 128 extracted maxillary anterior teeth were endodontically treated, and prepared with 4 methods of restorations; Composite resin filling with zinc phosphate cement, composite resin filling without zinc phosphate cement, composite resin filling with post, and metal crown with post. An Instron testing machine was used to measure the fracture loads of the specimens. The means of the failure loads for the 4 groups were compared by F-test statistically and the failure modes were observed. The results were as follows; 1. There were no statistically significant difference between the failure loads of the four methods of restoration. 2. Teeth without post were fractured in a horizontal or oblique plane through upper or middle third of the root. 3. In the posted teeth, fractures were occurred around the post. 4. In the metal crowned teeth with post, the fracture were occurred around the post or coronal area.