• Clean Technology
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• v.16 no.1
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• pp.1-11
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• 2010

As crude oil with heavier and/or highly oxidized components prevails, purification technologies such as desulfurization, denitrilization and demetalization have become important issues to control contents of sulfur and other impurities affecting the quality of petroleum. Also, the importance of catalyst technologies related with crude oil purification has been emphasized to control the production and yield of products. In this paper, technology trends of impurity removal such as sulfur, nitrogen and metal components from crude oil and catalysts related with purification of crude oil were studied through patent analysis. The patents published or registered in Korea, U. S. A., Japan, and Europe from mid 1970's to 2009 had been analyzed based on the application tendency, the distribution of major applicants, and their active indices, etc. The technology flow was figured out to see the technology trends.

• Clean Technology
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• v.7 no.3
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• pp.215-223
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• 2001

A present semiconductor cleaning technology is based upon RCA cleaning technology which consumes vast amounts of chemicals and ultra pure water(UPW) and is the high temperature process. Therefore, this technology gives rise to the many environmental issues, and some alternatives such as electrolyzed water(EW) are being studied. In this work, intentionally contaminated Si wafers were cleaned using the electrolyzed water. The electrolyzed water was generated by an electrolysis system which consists of three anode, cathode, and middle chambers. Oxidative water and reductive water were obtained in anode and cathode chambers, respectively. In case of NH4Cl electrolyte, the oxidation-reduction potential and pH for anode water(AW) and cathode water(CW) were measured to be +1050mV and 4.8, and -750mV and 10.0, respectively. AW and CW were deteriorated after electrolyzed, but maintained their characteristics for more than 40 minutes sufficiently enough for cleaning. Their deterioration was correlated with CO2 concentration changes dissolved from air. Contact angles of UPW, AW, and CW on DHF treated Si wafer surfaces were measured to be $65.9^{\circ}$, $66.5^{\circ}$ and $56.8^{\circ}$, respectively, which characterizes clearly the eletrolyzed water. To analyze the amount of metallic impurities on Si wafer surface, ICP-MS was introduced. It was known that AW was effective for Cu removal, while CW was more effective for Fe removal. To analyze the number of particles on Si wafer surfaces, Tencor 6220 were introduced. The particle distributions after various particle removal processes maintained the same pattern. In this work, RCA consumed about $9{\ell}$ chemicals, while EW did only $400m{\ell}$ HCl electrolyte or $600m{\ell}$ NH4Cl electrolyte. It was hence concluded that EW cleaning technology would be very effective for promoting environment, safety, and health(ESH) issues in the next generation semiconductor manufacturing.

• Resources Recycling
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• v.27 no.5
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• pp.23-29
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• 2018

Generally $NiSO_4$ and $NiCl_2$ were used as raw materials for producing nickel carbonate. In the case of the produced nickel carbonate, $Na_2SO_4$ and NaCl are generated on the surface and inside of the nickel carbonate to decrease the purity of the nickel carbonate. High purity nickel carbonate can be produced according to the degree of removal of such impurities. In this study, $NiCl_2$ produced by nickel MHP solvent extraction process was used to study the production of nickel carbonate. High purity nickel carbonate was prepared by the conditions according to the nickel salt and carbonate equivalence ratio, the reduction of Na and Cl in nickel carbonate according to the washing of nickel carbonate, and the reduction of Na and Cl according to the washing water temperature.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2349-2355
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• 2023

In the TRITIUM project, an on-site monitoring system is being developed to measure tritium (³H) levels in water near nuclear power plants. The quite low-energy betas emitted by ³H have a very short average path in water (5 ㎛ as shown by simulations for 18 keV electrons). This path would be further reduced by impurities present in the water, resulting in a significant reduction of the detection efficiency. Therefore, one of the essential requirements of the project is the elimination of these impurities through a filtration process and the removal of salts in solution. This paper describes a water treatment system developed for the project that meets the following requirements: the water produced should be of near-pure water quality according to ISO 3696 grade 3 standard (conductivity < 10 µS/cm); the system should operate autonomously and be remotely monitored.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.2
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• pp.69-76
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• 2007

As amount of waste matter rapidly increases with fast growth of cities and industry, how to dispose them has arisen as an important problem. Current policy of the government on disposal of waste is repressing generation of waste itself and in case of already generated waste, resource cycle waste management system that recycles waste after proper environmental process is getting established. Therefore recycling of waste and industrial by-products is rising hugely. One of largely wasted matters is waste gypsum, which was categorized as designated waste but changed to general since 1994. Due to disposal cost and lack of impurities removal technology, recycling of it was quite low. However, as impurities removal technology using semi-dried desulfurization process is developed lately, study on recycling of waste gypsum is going on lively. This study examines possibility of utilizing waste gypsum as alternative for concrete cement and analyzed attributes of waste gypsum before and after ball mill process to find out proper alternation ratio, and conducted strength and property tests on concrete subject whose percentage of cement use is substituted with 0, 5.0, 7.5, 10.0 and 12.5% of waste gypsum.

• Korean Journal of Materials Research
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• v.6 no.8
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• pp.817-824
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• 1996

Removal of Cu impurities on Si substrates using remote H-plasma was investigated. Si substrates were intentionally contaminated by 1ppm ${CuCI}_{2}$, standard chemical solution. To determine the optimal process condition, remote H-plasma cleaning was conducted varying the parameters of rf power, cleaning time and remoteness(the distance between the center of plasma and the surface of Si substrate). After remote H-plasma cleaning was conducted, Si surfaces were analysed by TXRF(total x-ray reflection fluorescence) and AFM(atomic force microscope). The concentration of Cu impurity was reduced by more than a factor of 10 and its RMS roughness was improved by more than 30% after remote H-plasma cleaning. TXRF analysis results show that remote H-plasma cleaning is effective in eliminating Cu impurity on Si surface when it is performed under the optimal process condition. AFM analysis results also verifies that remote H-plasma cleaning makes no damage to the Si surface. The deposition mechanism of Cu impurity may be explained by the redox potential(oxidation-reduction reaction potential) theory. Based on the XPS analysis results we could draw a conclusion that Cu impurities on the Si substrate are removed together with the oxide by a "lift-off" mechanism when the chemical oxide( which forms when Cu ions are adsorbed on the Si surface) is etched off by reactive hydrogen atoms.gen atoms.

• Resources Recycling
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• v.32 no.3
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• pp.38-44
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• 2023

Leaching tests were conducted using sulfuric acid and sodium hydroxide solutions to remove impurities from domestic graphite concentrate. As a result of the leaching experiment using sulfuric acid solution and sodium hydroxide solution, respectively, the difference of removal efficiency was insignificant when the concentration of sodium hydroxide or sulfuric acid was 2 mol/L or more. The fixed carbon content increased with increasing the temperature in the sulfuric acid solution leaching, while it remains constant above 150℃ in sodium hydroxide solution. For the repeated sequential leaching tests, the leaching conditions were 2 mol/L NaOH, 200℃, 1 hour in the sodium hydroxide solution leaching and 2 mol/L H₂SO₄, 100℃, 1 hour in the sulfuric acid solution leaching, respectively. When sulfuric acid leaching followed by sodium hydroxide solution leaching was repeated 5 times, the fixed carbon increased to 99.95% and ash content decreased to 0.048%, while the fixed carbon increased to 99.98% and ash content was reduced to 0.018 when sodium hydroxide solution leaching followed by sulfuric acid solution leaching was repeated 5 times.

• Korean Chemical Engineering Research
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• v.62 no.3
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• pp.246-252
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• 2024

In this study, impurities such as Li and F were removed from waste graphite through citric acid treatment, and changes in structural properties, capacity, and cycle stability of regenerated graphite were observed accordingly. Regenerated graphite pretreated in a nitrogen atmosphere was treated with citric acid, and its structure and characteristics were analyzed through SEM (Scanning Electron Microscope), FT-IR (Fourier Transform Infrared spectroscopy), XRD (X-ray Diffraction), and XPS (X-ray Photoelectron Spectroscopy). Waste graphite that was not treated with acid had a rapid decrease in capacity before 70 cycles, but graphite that had been treated with citric acid showed a capacity of 302.9 mAh g^-1 and a capacity retention rate of 93.1% at 100 cycles. In addition, despite changes in current density in rate performance, samples treated with citric acid showed 340.2 mAh g^-1 performance at 1.0C without change in capacity. As a result, it was confirmed that citric acid treatment not only effectively removed impurities and showed a high capacity retention rate, but also showed stability even at high current densities.

• Journal of the Korean Wood Science and Technology
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• v.50 no.5
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• pp.325-337
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• 2022

Grewia serrulata fibres were chemically treated with 3%, 6%, and 9% NaOH for the duration of 4 h. Additionally, the NaOH-treated fibres were also treated with 3 - (trimethoxysilyl) propyl methacrylate (silane). Properties such as density and tensile strength of the treated fibres were compared against the untreated fibres. The highest density was obtained in the case of 9% NaOH + silane treated fibres, which was 26.47% higher than untreated fibres, implying effective removal of hemicellulose. Likewise, the highest tensile strength was also obtained in the case of 9% NaOH + silane treated fibres. The increment observed in the tensile strength of the natural fibres was related to the removal of impurities, hemicellulose, and stress-raisers as well as deposition over the fibre surface that smoothed it. These observations were further validated by estimating changes in chemical constituents due to chemical treatment along with characterization techniques such as scanning electron microscopy and thermogravimetric analysis.

• Environmental Engineering Research
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• v.19 no.1
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• pp.15-22
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• 2014

In this study, the performances of various adsorbents-red mud, zeolite, limestone, and oyster shell-were investigated for the adsorption of multi-metal ions ($Cr^{3+}$, $Ni^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $As^{3+}$, $Cd^{2+}$, and $Pb^{2+}$) from aqueous solutions. The result of scanning electron microscopy analyses indicated that the some metal ions were adsorbed onto the surface of the media. Moreover, Fourier transform infrared spectroscopy analysis showed that the Si(Al)-O bond (red mud and zeolite) and C-O bond (limestone and oyster shell) might be involved in heavy metal adsorption. The changes in the pH of the aqueous solutions upon applying adsorbents were investigated and the adsorption kinetics of the metal ions on different adsorbents were simulated by pseudo-first-order and pseudo-second-order models. The sorption process was relatively fast and equilibrium was reached after about 60 min of contact (except for $As^{3+}$). From the maximum capacity of the adsorption kinetic model, the removal of $Pb^{2+}$ and $Cu^{2+}$ were higher than for the other metal ions. Meanwhile, the reaction rate constants ($k_{1,2}$) indicated the slowest sorption in $As^{3+}$. The adsorption mechanisms of heavy metal ions were not only surface adsorption and ion exchange, but also surface precipitation. Based on the metal ions' adsorption efficiencies, red mud was found to be the most efficient of all the tested adsorbents. In addition, impurities in seawater did not lead to a significant decrease in the adsorption performance. It is concluded that red mud is a more economic high-performance alternative than the other tested adsorption materials for applying a removal of multi-metal in seawater.