• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.2
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• pp.127-137
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• 2019

Zr electrorefining is demonstrated herein using Zirlo tubes in a chloride-fluoride mixed molten salt in the presence of $AlF_3$. Cyclic voltammetry reveals a monotonic shift in the onset of metal reduction kinetics towards positive potential and an increase in intensity of the additional peaks associated with Zr-Al alloy formation with increasing $AlF_3$ concentration. Unlike the galvanostatic deposition mode, a radial plate-type Zr growth is evident at the top surface of the salt during Zr electrorefining at a constant potential of -1.2 V. The diameter of the plate-type Zr deposit gradually increases with increasing $AlF_3$ concentration. Scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) and X-ray photoelectron spectroscopy (XPS) analyses for the plate-type Zr deposit show that trace amount of Al is incorporated as Zr-Al alloys with different chemical compositions between the top and bottom surface of the deposit. Addition of $AlF_3$ is effective in lowering the residual salt content in the deposit and in improving the current efficiency for Zr recovery.

• Tunnel and Underground Space
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• v.31 no.5
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• pp.333-359
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• 2021

Gases such as hydrogen and radon can be generated around the canister in high-level radioactive waste disposal systems due to several reasons including the corrosion of metal materials. When the gas generation rate exceeds the gas diffusion rate in the low-permeability bentonite buffer, the gas phase will form and accumulate in the engineered barrier system. If the gas pressure exceeds the gas entry pressure, gas can migrate into the bentonite buffer, resulting in pathway dilation flow and advective flow. Because a sudden occurrence of dilation flow can cause radionuclide leakage out of the engineered barrier of the radioactive waste disposal system, it is necessary to understand the gas migration behavior in the bentonite buffer to quantitatively evaluate the long-term safety of the engineered barrier. Experimental research investigating the characteristics of gas migration in saturated bentonite and research developing numerical models capable of simulating such behaviors are being actively conducted worldwide. In this technical note, previous gas injection experiments and the numerical models proposed to verify such behaviors are introduced, and the future challenges necessary for the investigation of gas migration are summarized.

• Resources Recycling
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• v.32 no.6
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• pp.45-53
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• 2023

This study discussed the trend and future strategy of adsorption technology R&D to effectively recover ammonia emitted from the livestock fields. A proper ammonia adsorbent should incorporate acidic or hydrogen bonding functional groups on the surface, as well as a high specific surface area and a good surface structure appropriate for ammonia adsorption. Activated carbon and minerals such as zeolite have widely been used as ammonia adsorbents, but their adsorption effects are generally low, so any improvement through surface modification should be necessary. For example, incorporation of metal chloride included in a porous adsorbent can promote ammonia adsorption effectiveness. Recently, new types of adsorbents such as MOFs (Metal-Organic Frameworks) and POPs (Porous Organic Polymers) have been developed and utilized. They have shown very high ammonia adsorption capacity because of adjustable and high specific surface area and porosity. In addition, Prussian Blue exhibited high ammonia adsorption and desorption performance and selectivity. This looks relatively advantageous in relation to the recovery of ammonia from livestock waste discharge. In the future, further research should be made to evaluate ammonia adsorption/desorption efficiency and purity using various adsorbents under conditions suitable for livestock sites. Also, effective pre- and/or post-treatment processes should be integrated to maximize ammonia recovery.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.52-57
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• 2010

Although chemical sedimentation and ion exchange are usually applied to the treatment of heavy metal ions and radioactive cations, they have some serious disadvantages like a great consumption of chemicals, the disposal of valuable metals, and the secondary pollution of soil by the solid-waste. The advanced countries recently have studied the electrochemical ion exchange, combined electrochemical reduction and ion exchange, for the development of the alternative technique. This study has been performed to investigate the optimum condition for the preparation of the nickel hexacyanoferrate (NiHCNFe) which is an electrochemical ion exchanger. NiHCNFe film was deposited on the surface of nickel plate by chemical method or electrochemical method. The morphology and composition of NiHCNFe were observed by SEM and EDS, respectively. The peak current density of NiHCNFe was measured from the cyclic voltammograms of the continuous oxidation-reduction reaction in a parallel plane ion exchange electrode reactor. It was found that the chemical preparation method was better than the electrochemical method. The concentrated NiHCNFe was apparently deposited on nickel plate when dipping in the preparing solution for 118 h, especially. It also had a best durable performance as an ion exchange electrode.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.1
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• pp.41-48
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• 2016

It is estimated that over 2 million tons of non-ferrous wastes are generated after refining. Up to now, most researches were focused on extracting precious metals and there were very few research on the utilization of the slag byproduct. In this study, we studied to evaluate whether copper slag could be used as aggregates in concrete. Fresh mortar were evaluated on the particle size and replacement ratio of the copper slag with river-sand. Experimental results indicated that flow, air content and drying shrinkage of concrete varied with particle size, which confirmed that proper classification of copper slag is very important. And, setting time and unit weight of the concrete increased with replacement ratio. When particle size of the slag was similar to the river-sand, concrete with copper slag showed slump, air content, setting time, drying shrinkage and unit weight became larger compared to the concrete using river-sand only. Therefore, it is believed that proper classification and replacement ratio should be optimized for the effective use of slag in concrete.

• Journal of the Korean earth science society
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• v.37 no.4
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• pp.211-217
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• 2016

There have been found mine tailings, wastes, and mining drainage scattered in the area of Nakdong River due to the improper maintenance of the abandoned mines. These contaminants can flow into rivers during the heavy rain periods in summer. Along the study area beginning Seokpo-myeon, Bonghwa-gun of Gyeongsangbuk-do untill Dosan-myeon, Andong-si, there are one hundred five mines including sixty metalliferous mines and forty-five nonmetal mines, which can adversely affect the adjacent rivers. To verify the contamination, we collected sediments, seepage water and surface water for a year both in rainy season and dry season. This study found that sediments, containing high concentrations of heavy metals caused by mining activities, are dispersed throughout the entire river basin (68 sample points with pollution index, based on the concentration of trace element, (PI) >10 among the total of 101 samples). The results of river water analysis indicated the increased concentrations of arsenic and cadmium at branches from Seungbu, Sambo, Okbang and Janggun mine, which concerns that the river water may be contaminated by mining drainage and tailing sediments. However, it is difficult to sort out the exact sources of contamination in sediments and waters only by using the chemical compositions. Thus the control of mining pollution is challenging. To prevent water from being contaminated by mining activities, we should be able to divide inflow rates from each origin of the mines. Therefore, there should be a continued study about how to trace the source of contaminants from mining activities by analyzing stable isotopes.

• Economic and Environmental Geology
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• v.36 no.3
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• pp.177-189
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• 2003

The main purposes of this study are to utilize mineralogical studies such as optical microscope, XRD and SEM/EDS analyses to characterize the oxidation of sulfide minerals and the mechanisms controlling the movement of dissolved metals from waste rocks at the abandoned Seobo mine. Mineralogical research of the waste rocks confirms the presence of anglesite, covellite, goethite, native sulfur and nsutite as secondary minerals, suggesting that these phases control the dissolved concentrations of As, Cu, Fe, Mn, Pb and Zn. The dissolved metals are precipitated, adsorbed and/or coprecipitated with(or within) Fe(Mn)-hydroxides and Mn(Fe)-hydroxides. The main phases of secondary mineral, Fe-hydroxide, can be classified as amorphous or poorly crystalline and more crystallized phases(e.g. goethite) by crystallinity. Amorphous or poorly crystalline Fe-hydroxide has relatively high As contents(9-24 wt.%). This poorly crystalline Fe-hydroxide changes toward more crystallized phase(e.g. goethite) which contains relatively low As(0.6-7.7 wt.%). These results are mainly due to the progressive release of As with the crystallization evolution of the As-trapping poorly crystalline Fe-hydroxides. It is also attributed to the differences of specific surface areas between the poorly crystalline Fe-hydroxides and well crystallized phases. The dissolved metals from waste rocks at Seobo mine area are naturally attenuated by a series of precipitation(as Fe, Mn, Cu, Pb), coprecipitation(Fe, Mn) and adsorption(As, Cu, Pb, An) reactions. The results of mineralogical researches permit to assess the environmental impacts of mine waste rocks in the areas, and can be used as a useful data to lay available mine restoration plan.

• Resources Recycling
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• v.20 no.3
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• pp.12-27
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• 2011

DOWA group has been working on metal recycling applying the smelting and refining process of KOSAKA Smelter. DOWA has developed it's metal recycling technologies through the treatment of black ore(complex sulfide ores) that contain many kinds of non-ferrous metals. In addition to these special technologies, DOWA has strengthened its hydrometallurgical process of precious metals and ability to deal with low-grade materials such as used electrical appliances or vehicles. On the other hand, JX Nippon Mining & Metals Corporation(JX-NMMC) carries out its metal recycling and industrial waste treatment businesses employing advanced separation, extraction and refining technologies developed through its extensive experience in the smelting of non-ferrous metals. JX-NMMC collects approximately 100,000t/y of copper and precious metal scraps from waste sources such as electronic parts, mobile phones, catalytic converters, print circuit boards and gold plated parts. These items are recycled through the smelting and refining operations of Saganoseki smelter and Hitachi Metal-recycling complex(HMC). In this like, metal recycling industries combined with environmental business service in Japan have been developed through excellent technologies for mineral processing and non-ferrous smelting. Also, both group, Dowa and JX-NMMC, were contributed to establish Japan's recycling-oriented society as the typical leading company of non-ferrous smelting. Now. it is an important issue to set up the collection system for e-waste.

• Resources Recycling
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• v.22 no.2
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• pp.29-36
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• 2013

Although Korean domestic production of flat panel displays totalled more than 48 trillion KRW in 2007, most of the flat panel display wastes have been land-filled or incinerated, which greatly overshadows Korean national prestige as a world leading producer and developer of flat panel display devices. Countries such as Japan or EU possess quite limited land-fill capability and have sought ways to dispose of WEEEs from environment-friendly perspective rather than recovery of valuable materials from the wastes. Considering relatively short cycle of about 5 years for flat panel display devices, it is estimated that more than 5 million units will be accumulated as wastes by 2015. Urban mining is a most suitable countermeasures against China's monopoly of rare and rare earth metals, which are contained in flat panel display wastes. Therefore, materials recycling of waste LCD units has to be developed and commercialized soon enough for economic and environment-friendly recovery of valuable resources hidden in LCD wastes.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.279-288
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• 2014

Nuclear energy is expected to meet the growing energy demand while avoiding CO2 emission. However, the problem of accumulating spent fuel from current nuclear power plants which is mainly composed of uranium oxides should be addressed. One of the most practical solutions is to reduce the spent oxide fuel and recycle it. Next-generation fuel cycles demand innovative features such as a reduction of the environmental load, improved safety, efficient recycling of resources, and feasible economics. Pyroprocessing based on molten salt electrolysis is one of the key technologies for reducing the amount of spent nuclear fuel and destroying toxic waste products, such as the long-life fission products. The oxide reduction process based on the electrochemical reduction in a LiCl-$Li_2O$ electrolyte has been developed for the volume reduction of PWR (Pressurized Water Reactor) spent fuels and for providing metal feeds for the electrorefining process. To speed up the electrochemical reduction process, the influences of the feed form for the cathode and the type of anode shroud on the reduction rate were investigated.