• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.418-424
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• 2017

Magnesium has a higher specific strength than other metals and is widely used industry wide due to its excellent vibration absorption ability and electromagnetic wave shielding property.For example, it is used for automobile parts such as car seat frames and cylinder heads, and is widely used in electronic products such as notebook cases and mobile phone cases. In addition, it is in the spotlight as a bone-implant material used to assist in the treatment of damaged bones when the bones are cracked or broken. Currently, Ti alloy, stainless steel and Co-Cr-Mo alloy are used as the implant material, and the Mg alloy remains in research stage. The current problem with bone implant implants is that the patients must undergo reoperation to remove the implants after joint surgery. Magnesium, however, can achieve sufficient strength compared to current materials. In addition, since it is self-decomposed after the recovery, reoperation is not necessary. In this paper, Mg alloys were designed by adding harmless Ca and Zn to the human body. In order to improve the strength and corrosion resistance, the final alloy was designed by adding a small amount of Sr as a grain refiner. The radioactive elements of Sr are harmful to the human body, but other naturally occurring Sr elements are harmless. Microstructure analysis of the alloys was performed by optical microscopy and scanning electron microscopy. The mechanical properties and corrosion characteristics were evaluated by tensile test, potentiodynamic test and immersion test.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.2
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• pp.119-128
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• 2013

Since the early 2000s, demand for coastal dredging projects have been significantly increased, and the dredged sediments have showed the continuing marked increases through the multiple projects with other coastal development and constructions. As significant or potential degradation of marine environment has been mounting, we checked the current situation of marine environmental impact assessment through marine water and sediment qualities in relation with dredging projects of the sea area utilization consultation statements submitted in 2011. While analysis percentages of the general items were usually higher, harmful components such as metals revealed wide variation of analysis percentages. In the event of analysis of metals, the pre-treatment process (full digestion) and analysis method were not properly implemented in accordance with the guidelines for preparation of consultation statements. Although not specified in the guidelines, verification procedures (tests of recovery efficiency and detection limit) to secure the reliability were almost ignored. As a result, most of developers did conduct poor marine environmental impact assessment on coastal dredging and related projects. We suggested that the responsible government authority should establish new detailed guidelines on the sea area utilization consultation for more strict evaluation and diagnosis of marine environment and distinctly request the developer to obey the guidelines by complementing the system of the sea area utilization consultation.

• Korean Journal of Environmental Agriculture
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• v.42 no.1
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• pp.35-43
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• 2023

The fine particulate structure of biochar limits its use as a heavy metal adsorbent, and makes separation of the biochar from the solution technically challenging, thereby reducing recovery of the heavy metals. To address this issue, this study prepared biochar beads under various mixing conditions and investigated their efficiency in removing Pb from aqueous solutions using adsorption models. The biochar beads were produced by mixing alginate and biochar at different ratios: alginate bead (AB), 1% biochar + bead (1-BB), 2.5% biochar + bead (2.5-BB), and 5% biochar + bead (5-BB). The results revealed that the Freundlich isothermal adsorption pattern of the biochar beads to Pb was of the L-type. The highest Langmuir isothermal adsorption capacity (28.736 mg/g) was observed in the 2.5-BB treatment. The dominant mechanism among the kinetic adsorption characteristics of biochar beads for Pb was chemical adsorption. Additionally, the optimal pH range for Pb adsorption was found to be between 4 and 5.5. The highest Pb removal efficiency (97.9%) was achieved when 26.6 g/L of biochar beads were used. These findings suggest that biochar beads are an economical and highly efficient adsorbent that enables separation and recovery of fine biochar particles.

• Economic and Environmental Geology
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• v.12 no.1
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• pp.41-49
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• 1979

A literature review is made on the physical and chemical characteristics of clay minerals in acidic solutions from the mineralogical and hydrometallurgical viewpoints. Some of the important characteristics of clays are their ability to cation exchange, swelling, and incongruent dissolution in acidic solutions. Various clay minerals can take up metallic ions from solution via cation exchange mechanism. Generally, cation exchange capacity increases in the following order : kaolinite, halloysite, illite, vermiculite, and montmorillonite. In acidic solutions, the cation uptake such as copper by clay minerals is strongly inhibited by hydrogen and aluminum ions and thus is not economically significant factor for recovery of metals such as uranium and copper. In acidic solutions, the cation uptake is substial. Swelling is minimal at lower pH, possibly due to lattice collapse. Swelling may be controllable with montmorillonite type clays by exchanging interlayer sodium with lithium and/or hydroxylated aluminum species. The effect of add on clay minerals are : 1. Division of aggregates into smaller plates with increase in surface area and porosity. 2. Clay-acid reactions occur in the following order: (i) $H^+$ replacement of interlayer cations, (ii) removal of octahedral cations, such as Al, Fe, and Mg, and (iii) removal of tetrahedral Al ions. Acid attack initiates, around the edges of the clay particles and continued inward, leaving hydrated silica gel residue around the edges. 3. Reaction rates of (ii) and (iii) are pseudo-1st order and proportional to acid concentration. Rate doubles for every temperature increment of $10^{\circ}C$. Implications in in-situ leaching of copper or uranium with acid are : 1. Over the life span of the operation for a year or more, clays attacked by acid will leave silica gel. If such gel covers the surface of valuable mineral surfaces being leached, recovery could be substantially delayed. 2. For a copper deposit containing 0.5% each of clay minerals and recoverable copper, the added cost due to clay-acid reaction is about 1.5c/lb of copper (or 0.93 lbs of $H_2SO_4/1b$ of copper). This acid consumption by clay may be a factor for economic evaluation of in-situ leaching of an oxide copper deposit.

• Korean Journal of Food Science and Technology
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• v.43 no.5
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• pp.525-531
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• 2011

This study was conducted to examine the contents of lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) in meat and meat products in Korea. The contents of Pb, Cd, As, and Hg in 466 samples of beef, pork, chicken, duck, ham, and sausage were measured using inductively coupled plasma mass spectrometry or a mercury analyzer. Wet ashing and microwave method were compared, and the recovery and reproducibility of the microwave method were better than those of wet ashing for meat and meat products. The recovery of the microwave method was 98.1% for Pb, 104.6% for Cd, and 103.4% for As, respectively. The best result was obtained through digestion using an acid mixture ($HNO_3$/$H_2O_2$, 6:2). Hg content was measured using a mercury analyzer. As a result, the contents of Hg and Cd in samples were lower than those of Pb and As. The average contents of Pb were 0.009 mg/kg in beef, 0.010 mg/kg in pork, 0.006 mg/kg in chicken, 0.007 mg/kg in duck, 0.005 mg/kg in ham, and 0.009 mg/kg in sausage. The average Cd contents were 0.0004 mg/kg in beef, 0.0004 mg/kg in pork, 0.0005 mg/kg in chicken, 0.0012 mg/kg in duck, 0.0015 mg/kg in ham, and 0.0019 mg/kg in sausage. The average As contents were 0.016 mg/kg in beef, 0.004 mg/kg in pork, 0.021 mg/kg in chicken, 0.010 mg/kg in duck, 0.014 mg/kg in ham, and 0.018 mg/kg in sausage. The average Hg contents were 0.713 ${\mu}g/kg$ in beef, 0.902 ${\mu}g/kg$ in pork, 0.710 ${\mu}g/kg$ in chicken, 0.796 ${\mu}g/kg$ in duck, 1.141 ${\mu}g/kg$ in ham, and 1.052 ${\mu}g/kg$ in sausage. Based on the results of the National Health and Nutrition Survey 2005, the levels of dietary exposure to heavy metal contaminants in meat and meat products were compared with the provisional tolerable weekly intake(PTWI) established by the Joint FAO/WHO Expert Committee on Food Additives. The average dietary exposure of the general population from meat and meat products was 0.03-0.2% of PTWI for Pb, Cd, As, and Hg, which indicates a safe level for public health at present.

• Journal of Food Hygiene and Safety
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• v.35 no.1
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• pp.23-30
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• 2020

This study investigated the migration levels of lead (Pb), cadmium (Cd), and arsenic (As) from food contact articles (glassware, ceramics, enamelware, and earthenware) into a food stimulant (4% v/v, acetic acid). Migration tests were performed at 25℃ for 24 h and all analyses were performed using Inductively-Coupled Plasma Mass Spectrometry (ICP-MS). The method was validated by linearity of calibration curves, limit of detection (LOD), limit of quantification (LOQ), recovery, precision, and uncertainty. In glassware, the migration concentrations ranged from not-detected (N.D.) to 752.21 ㎍/L and N.D. to 1.99 ㎍/L for Pb and Cd, respectively. In ceramics, the migration concentrations ranged from N.D. to 1,955.86 ㎍/L, N.D. to 74.06 ㎍/L, and N.D. to 302.40 ㎍/L for Pb, Cd, and As, respectively. In enamelware, the migration concentrations ranged from N.D. to 4.48 ㎍/L, N.D. to 7.00 ㎍/L, and N.D. to 52.00 ㎍/L for Pb, Cd, and Sb, respectively. In earthenware, the migration concentrations ranged from N.D. to 13.68 ㎍/L, N.D. to 0.04 ㎍/L, and N.D. to 6.71 ㎍/L for Pb, Cd, and As, respectively. All results were below the migration limits of Korea standards and specifications for food utensils, containers, and packages.

• Korean Journal of Food Science and Technology
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• v.43 no.2
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• pp.230-234
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• 2011

According to the Codex committee, the maximum allowable level for lead in fruits is 0.1 mg/kg. This survey was conducted as a surveillance program following the establishment of safety guideline for fruits in Korea. Concentrations of lead (Pb), cadmium (Cd), arsenic (As) and mercury (Hg) were measured in 927 samples using a ICP-MS and a mercury analyzer. The recoveries of microwave digestion method were 86.0-110.4% for Pb, 81.0-104.0% for Cd and 82.0-104.7% for As by standard addition method. The recovery of direct mercury analyzer was 106.5% for Hg. The average levels of Pb in ${\mu}g/kg$ were $10.0{\pm}12.8$ for apple, $8.8{\pm}10.9$ for pear, $4.1{\pm}4.4$ for persimmons, $14.9{\pm}12.3$ for mandarin, $7.1{\pm}6.5$ for orange, $3.1{\pm}3.3$ for banana, $8.8{\pm}8.9$ for kiwi, and $9.3{\pm}9.7$ for mango. The average levels of Cd in ${\mu}g/kg$ were $0.4{\pm}0.3$ for apple, $2.0{\pm}1.6$ for pear, $0.3{\pm}0.3$ for persimmon, $0.1{\pm}0.1$ for mandarin, $0.1{\pm}0.1$ for orange, $1.3{\pm}1.8$ for banana, $0.5{\pm}0.5$ for kiwi, and $0.7{\pm}0.6$ for mango. The average levels of As in ${\mu}g/kg$ were $2.0{\pm}2.1$ for apple, $1.2{\pm}1.3$ for pear, $1.5{\pm}1.2$ for persimmon, $0.8{\pm}0.3$ for mandarin, $1.5{\pm}0.5$ for orange, $1.8{\pm}1.2$ for banana, $1.6{\pm}1.5$ for kiwi, and $1.2{\pm}1.5$ for mango. The average levels of Hg in ${\mu}g/kg$ were $0.5{\pm}0.4$ for apple, $0.3{\pm}0.2$ for pear, $0.2{\pm}0.1$ for persimmon, $0.2{\pm}0.1$ for mandarin, $0.2{\pm}0.1$ for orange, $0.2{\pm}0.0$ for banana, $0.2{\pm}0.2$ for kiwi, and $0.6{\pm}0.2$ for mango. Based on the Korean public nutrition report 2005, these levels (or amounts) are calculated only at 0.17% for Pb, 0.013% for Cd and 0.006% for Hg of those presented in provisional tolerable weekly Intake (PTWI) which has been established by FAO/WHO. Therefore, the levels presented here are presumed to be adequately safe.