• Journal of the Korean institute of surface engineering
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• v.51 no.1
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• pp.1-10
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• 2018

Anodic oxidation treatment of metals is one of typical surface finishing methods which has been used for improving surface appearance, bioactivity, adhesion with paints and the resistances to corrosion and/or abrasion. This article provides fundamental principle, type and characteristics of the anodic oxidation treatment methods, including anodizing method and plasma electrolytic oxidation (PEO) method. The anodic oxidation can form thick oxide films on the metal surface by electrochemical reactions under the application of electric current and voltage between the working electrode and auxiliary electrode. The anodic oxide films are classified into two types of barrier type and porous type. The porous anodic oxide films include a porous anodizing film containing regular pores, nanotubes and PEO films containing irregular pores with different sizes and shapes. Thickness and defect density of the anodic oxide films are important factors which affect the corrosion resistance of metals. The anodic oxide film thickness is limited by how fast ions can migrate through the anodic oxide film. Defect density in the anodic oxide film is dependent upon alloying elements and second-phase particles in the alloys. In this article, the principle and mechanisms of formation and growth of anodic oxide films on metals are described.

• Journal of Korean Society on Water Environment
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• v.21 no.5
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• pp.505-510
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• 2005

The objective of this study was to remove non-biodegradable matters and ammonia ion in livestock wastewater using Fenton oxidation and Zeolite adsorption process. After coagulation process as 1st treatment, non-biodegradable matters remained after 1st treatment were removed by using OH radical produced in Fenton oxidation process. Zeolite as cation adsoption process was used to remove ammonia ion in 2nd treatment water. As a result of treatment using these processes, NBDCOD removal efficiency was over 90% and ammonia ion was almost removed. Most aromatics or polynuclear aromatics like benzene, phenol and scatol in livestock wastewater wasn't detected after Fenton oxidation process.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.597-600
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• 1995

The effects of surface oxidation on magnetic properties were investigated at high frequencies (10k-100MHz) for $7-18\mu\textrm{m}$ thick $Co_{70}Fe_{5}Si_{15}B_{10}$ amorphous ribbons with controlled domain structure. Oxidation was accelerated by acid-treatment or anodic oxidation treatment, and the insulation layers were prepared on the surfaces of the ribbons. The acid-treatment was effective in improving permeability and magnetic loss. Although the anodic oxidation treatment was effective in both making oxide layer and thinning, the magnetic properties were not improved compared with the case of the acid-treatment.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.3
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• pp.186-191
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• 1998

An oxidation behavior of 304 and 316 stainless steels were studied in dry air. After solution treatment, specimens were polished up to $1{\mu}m$ $A1_2O_3$ grade and then subjected to oxidation treatment in dry air at $800^{\circ}C{\sim}1200^{\circ}C$. The oxidation behavior between matrix and oxide scale was analyzed with SEM, EDS and XRD. When oxidation treatment was conducted at $1200^{\circ}C$, large thickness of Fe oxide scale was formed on top of surface and fine $(Cr,Fe)_2O_3$ oxide film was formed below it. Cr rich zone existed at interface between metal and $(Cr,Fe)_2O_3$ oxide layer, and it was believed that this zone acted as obstacle to oxidation. Most of Ni was detected at the interface between metal and $(Cr,Fe)_2O_3$ and also detected at the interface between $Fe_2O_3$ and $(Cr,Fe)_2O_3$.

• Journal of Environmental Health Sciences
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• v.24 no.3
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• pp.63-69
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• 1998

The treatment of soils and water contaminated with MTBE using the Fenton oxidation was investigated. The effects of dosage of $H_{2}O_{2}$, and Fe$^{2+}$ concentrations, and solution pH on transformation and mineralization in soil were evaluated. Generation of TBA and acetone following Fenton-oxidation of MTBE in water and generation of acetone following Fenton-oxidation of TBA were observed. Therefore TBA and acetone are degradation intermediates of MTBE. There was a large difference of treatment efficiency in Fenton oxidation of MTBE between soil and water system. This may be caused by the complex nature of soil, soil organic matter which can consumed OH $\cdot$ radicals, and interacting with inorganic-soil constituents. The pH of soil was observed to have a significant effect on the chemical oxidation efficient of MTBE in soil The data demonstrated that optimal pH range were pH 3~4 and around 6. The soil batch studies demonstrated that treatment efficiency of MTBE was enhanced by adding additional ferrous salts but Fenton-oxidation occurred in no additional iron which indicated that iron in soil can catalyze the Fenton-oxidation. The most effective parameter of Fentonoxidation was $H_{2}O_{2}$/Fe$^{2+}$ ratio which theocratical ratio is 0.5. The optimal range of this ratio was found to be 0.6~2.3. In evaluating effect of $H_{2}O_{2}$ dosage on treatment efficiency, the increase of $H_{2}O_{2}$ did not always lead to increase of decompositions of MTBE in soil. Fenton oxidation was effective in destroying MTBE in aqueous extracts of contaminated soil and water. Experimental data provided evidence that the Fenton oxidation can effectively remediate MTBE-contaminated water and soil.

• Nuclear Engineering and Technology
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• v.28 no.4
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• pp.366-372
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• 1996

The simulated spent PWR fuel pellet which is corresponding to the turnup of 33,000 MWD/MTU is prepared by adding 11 fission-product elements to UO$_2$. The simulated spent fuel pellet is treated at 40$0^{\circ}C$ in air (oxidation), at 110$0^{\circ}C$ in air (high-temperature treatment), and at $600^{\circ}C$ in hydrogen (reduction). The product is treated through additional addition and reduction up to 3 cycles. Pellets are completely pulverized by the first oxidation, and the high-temperature treatment causes particle and crystallite to grow and surface to be smooth, and thus particle size significantly increases and surface area decreases. The reduction following the high-temperature treatment decreases much the particle size by means of the formation of intercrystalline cracks. The particle size decreases a little during the second oxidation and reduction cycle and then remains nearly constant during the third and fourth cycles. Surface area of pounder increases progressively with the repetition of oxidation and reduction cycles, mainly due to the formation of Surface cracks. The degradation of surface area resulting from high-temperature treatment is restored by too subsequent resulting oxidation and reduction cycles.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.487-498
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• 2006

The oxidation processes of metal catalysis were practically applied into the flexographic inks wastewater treatment to derive the most effective and economical system among all the processes of iron-salts coagulation, iron-catalyzed air oxidation, and coagulation followed by biological treatment. The iron concentration and pH were optimized as $2.8{\times}10^{-3}mol$ and 5.5~6.0, respectively, for all the oxidation processes. At the optimal reaction conditions, the removal efficiencies of $TCOD_{Mn}$ and Color were as follows for the respective process: i) 75% $TCOD_{Mn}$ and 77% Color removals for iron-salts coagulation, ii) 91% TCODMn and 90% Color removals for iron-catalyzed air oxidation, iii) 74~92% $TCOD_{Mn}$ and 81~90% Color removals for coagulation followed by biological treatment. Based on the economical and technological aspects, iron-catalyzed air oxidation was confirmed as the most effective process in the treatment of industrial wastewater.

• Journal of the Korean Applied Science and Technology
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• v.22 no.3
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• pp.250-256
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• 2005

This study was aimed to investigate treatment feasibility of leachate from D landfill that is located in gyr대ungbuk. From the analytical results of leachate, organic and nonbiodegradable matters were contained in high concentration. Thus chemical treatment was introduced to degrade nonbiodegradable matters in pre or post biological process. Two types of Fenton oxidation were adapted in this study. The first one is pre treatment process before biological treatment. The second one is post treatment process after biological treatment. The optimal conditions of both treatment methods were investigated as follows. In case of pre treatment process, the optimal conditions appeared in $Fe^{+2}/H_2O_2$(mmol/mmol): 0.1, $H_2O_2/CODcr$(mg/mg): 27.0, pH: 3 and reaction time: 2hrs. On the other hand, in case of post treatment process, the optimal conditions appeared in $Fe^{2+}$(mmol/mmol): 0.14, $H_2O_2/COD_{cr}$(mg/mg): 57.4, pH: 3 and reaction time: 1.25hrs. In the above optimal conditions, high COD removal was obtained in pre and post treatment process. Also it can expect that Fenton oxidation converted nonbiodegradable matters into biodegradable matters.

• Advances in environmental research
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• v.9 no.3
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• pp.191-214
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• 2020

The rise in population and industrialization accounts for the generation of a huge amount of wastewaters. The treatment of this wastewater is obligatory to safeguard the environment and various life forms. Conventional methods for high strength wastewater treatment coming out to be ineffective. Advanced oxidation processes (AOPs) for such wastewater treatment proved to be very effective particularly for the removal of various refractory compounds present in the wastewater. Ozone based AOPs with its high oxidizing power and excellent disinfectant properties is considered to be an attractive choice for the elimination of a large spectrum of refractory compounds. Furthermore, it enhances the biodegradability of wastewaters after treatment which favors subsequent biological treatments. In this review, a detailed overview of the AOPs (like the Fenton process, photocatalysis, Electrochemical oxidation, wet air oxidation, and Supercritical water oxidation process) has been discussed explicitly focusing on ozone-based AOPs (like O₃, O₃/H₂O₂, O₃/UV, Ozone/Activated carbon process, Ozone/Ultrasound process, O₃/UV/H₂O₂ process). This review also comprises the involved mechanisms and applications of various ozone-based AOPs for effective municipal/industrial wastewaters and landfill leachate treatment. Process limitations and rough economical analysis were also introduced. The conclusive remarks with future research directions also underlined. It was found that ozonation in combination with other effective AOPs and biological methods enhances treatment efficacies. This review will serve as a reference document for the researchers working in the AOPs field particularly focusing on ozone-based AOPs for wastewater treatment and management systems.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.5
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• pp.227-232
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• 2012

Magnesium alloy have good physical properties such as good castability, good vibration absorption, high strength/weight ratios. Despite the desirable properties, the poor resistance of Mg alloy impedes their use in many various applications. Therefore, magnesium alloy require surface treatment to improve hardness, corrosion and wear resistance. Plasma Electrolytic Oxidation (PEO) is one the surface treatment methods to form oxide layer on Mg alloy in alkali electrolyte. In comparison with Anodizing, there is environmental process having higher hardness and faster deposition rate. In this study, the characteristics of oxide film were examined after coating the AZ31 Mg alloy through the PEO process. We changed concentration of sodium aluminate into $K_2ZrF_6$, KF base electrolyte. The morphologies of the coating layer were characterized by using scanning electron microscopy (SEM). Corrosion resistance also investigated by potentiodynamic polarization analysis. As a result, propertiy of oxide layer were changed by concentration of sodium aluminate. Increasing with concentration of sodium aluminate in electrolyte, the oxidation layer was denser and the pore size was smaller on the surface.