• Journal of the Korea Organic Resources Recycling Association
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• v.12 no.3
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• pp.134-139
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• 2004

A study was made on the synthesis of a carbonate base nitrogen-free deliming agent using a non-phosgene compound applicable to the deliming process, which is one of the biggest sources of pollutant increasing the T-N concentration in the effluent from the leather making processes. And also studied on the possibility of using the agent in the deliming process. Through measurement of T-N, BOD, COD and SS in the effluent after the agent is used, contents of Ca and Cr and TS in the leather after the deliming process were measured, by which deliming efficiency, influences to the physical properties of the chromium tanned leather and reducing effects of T-N, BOD, COD and SS concentrations in the effluent could be confirmed. Thus an eco-friendly study has been conducted.

• Journal of the Korea Organic Resources Recycling Association
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• v.2 no.1
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• pp.75-86
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• 1994

Garbage composting was studied in a controlled batch reactor with the addition of cooked rice as a biodegradable carbon source to find the effect of C/N ratio control on composting. And composting of bulking agents such as sawdust and wheat straw were tested with the addition of ammonium sulfate as a nitrogen source. As expected, biodegradation of the garbage having low C/N ratio was improved to some extent when foreign carbon was added. But bulking agents used in this study exerted slightly biodegradable carbon potential, indicating that the estimation of the dose of additional carbon considering desirable C/N ratio was not reasonable when lignocellulosic bulking material was added to garbage. It was found that the optimum moisture content increased with sawdust addition meaning the C/N ratio increment. Considering the above results, it was suggested that 78g sawdust per 100g garbage should be mixed to make C/N ratio to 25 and moisture content to 56% for effective composting of the garbage studied in this paper.

• Journal of the Korean Ceramic Society
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• v.56 no.4
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• pp.365-373
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• 2019

Pond ash is a mixture of mostly coarser fly ash and bottom ash. The recycling rate of pond ash is low because pond ash is mixed with seawater and deposited in ponds. The pond ash is also subjected to natural weathering over a period of time. In this study, we investigated whether pond ash can be used as a raw material of geopolymers, without any purification process or through a minimal purification process. In addition, we investigated whether synthetic basalt made by adding foaming agent to geopolymer or casting it into a mold can show the surface of the natural basalt as it is. The highest 7-day compressive strength in geopolymers from pond ash without purification process was 26 MPa. The highest 7-day compressive strength in geopolymers from pond ash with impurities removed through dry sieve analysis was found to improve to 80 MPa. On the other hand, synthetic basalt made with geopolymer was shown to be more advantageous aesthetically when produced by casting it in a silicone mold rather than by adding a foaming agent. Non-purified pond ash can be made into geopolymers having low strength. Pond ash purified by sieving can, without use of an aggregate, be made into geopolymer having high-strength. Also, it is possible to produce synthetic basalt with the same appearance as natural basalt and sufficient strength for commercialization. This process will contribute to the mass consumption and recycling of pond ash.

• Journal of environmental and Sanitary engineering
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• v.16 no.4
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• pp.38-46
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• 2001

The purposes of this study were to examine applicability of waste egg shells as conditioning agent, to determine the optimum conditions for improving digested sludge dewaterability and to compare with before and after adding them. It estimated that the optimum conditions were dosage 30 g/L, particle size 10mesh, temp. $30^{\circ}C$, pH 7 and dewatering pressure $2.66{\pm}10^4{\;}N/m^2$. On the basis of induced optimum conditions, if adding waste egg shells in digested sludge, its specific resistance was $1.13{\pm}10^{12}{\;}m/kg$ and was low about 3 times than raw digested sludge $3.5{\pm}10^{12}{\;}m/kg $. Therefore, in view of waste recycling, it seemed that we could utilize waste egg shells as conditioning assent for improving dewaterability of digested sludge.

• International Journal of Safety
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• v.1 no.1
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• pp.47-51
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• 2002

This study was performed by measuring the minimum ignition temperature of polyurethane form recovered from the recycling process of the end-of-life home appliances. The critical ignition temperature of polyurethane form was lower as the size of the sample vessel was increased, and that of polyurethane form using cyclopentane as the forming agent was relatively lower than the polyurethane form using CFC and the combustion of cyclopentane-polyurethane form occurred fiercely. It is considered that the recycling process of end-of-life home appliances using cyclopentane-polyurethane form as the insulator would require a special fire and dust explosion prevention measures since there exists a high potential hazard of fire and dust explosion during crushing and storage processes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.729-736
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• 2016

It is necessary to recycle and reuse waste paper for preservation of the global environment. Instead of a solid deinking agent, liquid deinking agents have been made using various fatty acids with EO/PO added for higher deinking effect. The removal efficiency of ink on waste paper was evaluated by the ERIC and brightness properties after processes of recycling pulping (sample composition ONP: OMG = 5:5, concentration 15%, temperature $45^{\circ}C$, pulping time 20 min.) and flotation (concentration 1%, temperature $45^{\circ}C$, air flow 7 L/min, time 8 min.). Also, the ink reattachment of paper was evaluated by hyperwashing. The results show that it is effective for mass-preparation to saponify oleic acid with KOH at $80^{\circ}C$ and to add EO/PO. This deinking agent was used in a paper plant, and we evaluated the brightness, color, and ERIC. The deinking agent showed excellent performance.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.477-480
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• 2003

This study discusses the fundamental properties of cement mortar with the kinds and adding ratio of stabilizing agent of recycled water. According to the results, fluidity and air content hardly make difference by the kinds and adding ratio of stabilizing agent. When recycled water is used, setting time is shortened slightly in comparison with plain mortar because of an increase of fine particle. And it is similar to the use of recycled water in the case of A, Band D(stabilizing agent), but shortened significantly in the case of C. Also, it does not show difference with variation of the adding ratio, but as the adding ratio increases, it approach to the value of plain mortar. When recycled water is used, compressive strength is similar to plain concrete, and it shows the larger value in order of D, C and A. As the adding ratio of stabilizing agent increases, it decreases at 3days, but increases at 7 and 28days. However, at the adding ratio of 0.5%, it decreases, instead. Length change ratio by drying shrinkage increases in the case of B in comparison with plain mortar, but is similar to plain mortar in the other stabilizing agent. As the adding ratio of stabilizing agent increases, it decreases, however, increases at the adding ratio of 0.5%

• KSBB Journal
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• v.25 no.1
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• pp.73-78
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• 2010

In this study, recovering agent was produced with organic sludge and modified peat moss (MPM) in pilot plant mixer to recover oil contaminated soil, and field test of it was estimated using landfarming method. Oil contaminated soil recovering agent was thought to contain more microorganisms than raw waste sludge and was no problem to come onto the market because there were not any items of specified wastes. According to the results of TPH variation with time, it was observed the initial degradation velocity of oil with produced recovering agent was rapid up to 50% after 4 days, remarkably. Because the microorganisms in the organic sludge discharged from chemical plant already acclimated with oil, therefore, it could be estimated initial degradation velocity of recovering agent might be rapid. It was concluded that the oil contaminated soil recovering agent produced in this study have high marketability because of its two aspects on recycling of wastes and initial rapid degradation capacity.

• Resources Recycling
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• v.27 no.5
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• pp.49-53
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• 2018

In developing an optimum steelmaking process, the purity of the product, environmental impact, capability and cost of the process should be considered. Desulfurization of molten iron is conducted during preliminary treatment stage before converter operation. Although fluorite is added as a desulfurizing agent in CaO and $CaCO_3$ based agents, the concentration of fluorine in slag is strictly regulated. In order to develop desulfurizing agent without fluorine, CaO was mixed with Al dross and ladle slag containing alumina. The characteristics and desulfurizing capacity of the CaO based desulfurizing agent thus prepared were tested by varying temperature of Kanvara Reactor. Our results showed that the desulfurizing capacity of the samples prepared in this work was found to be similar to that of the traditional desulfurizing agents with fluorine.

• Resources Recycling
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• v.21 no.1
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• pp.66-74
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• 2012

In order to evaluate the feasibility of selective sulfidization of uranium and rare-earth(RE) oxides, an analysis on thermodynamic data, such as $M-O_2-S_2$ phase stability diagram and changes of Gibbs free energy for sulfidization of uranium and rare-earth oxides were carried out. Comparing $RE-O_2-S_2$ with $U-O_2-S_2$ phase stability diagram at wide range of sulfur potential, $UO_2$ remains unreacted, while RE oxides are sulfidized. The Gibbs free energy change(${\Delta}G^{\circ}$) of sulfidization of RE oxides is lower than that of uranium oxides. Thus, the selective formation of RE sulfides is possible during sulfidization of RE and uranium oxides at lower temperature. $CS_2$ was selected as a sulfidizing agent, because it is a stronger sulfidizing agent than other agents and reacts at lower temperature.