• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.485-488
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• 2008

Recycled fine aggregate has low quality because it contains large amount of old mortar. So, its usage is limited to a lower value-add, such as the roadbed material etc. Also, alkaline water occurred from treatment process of the waste concrete is becoming the cause of environmental problem. Accordingly, this study is to develop on the high quality recycled fine aggregate produced by low speed wet abraser using sulphuric. We investigated the properties of compressive strength of the mortar which was manufactured using recycled fine aggregate containing calcined gypsum produced by earlier mentioned process. Test results indicate that mortar using recycled fine aggregate containing calcined gypsum has lowest compressive strength. It seems that low compressive strength is closely associated with the expansion of the specimen by excessive formation of ettringite.

• Korean Journal of Environmental Agriculture
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• v.6 no.1
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• pp.25-30
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• 1987

This study was conducted to find out the effect of several improvers such as triple super phosphate, slaked lime, wollastonite and gypsum for reducing Cd content in brown rice. Several improvers were applied to two different types of soils which are contaminated with copper-zinc mine wasted and sludge.(Soil I contained Cd : 7.88, Cu : 57.9, Zn : 175.0 ppm, Soil II contained Cd : 3.95, Cu : 30.2, Zn :124.0 ppm) In general, effects of improvers on reducing content of Cd, Cu and Zn in brown rice were greater in soil I than soil II. In soil I, the Cd content of brown rice was reduced to 0.4ppm below by application of triple superphosphate, fused phosphate, slaked lime and gypsum, 98, 225, 190 and 276Kg/10a, respectively. Triple superphosphate was more effective than fused phosphate in reducing uptake of Cd, Cu and Zn by applying them as an equal amount of phosphorous, also to equal alkalinity, slaked lime had the highest effect. Negatively linear effect was found between soil pH and Cd and Zn content in brown rice. As to above results, it was no doubt that triple superphosphate, fused phosphate and slaked lime would be applied to reduced heavy metals in brown rice. The slaked lime, triple super phosphate and fused phosphate were available to reduce uptake of Cd, Cu and Zn by rice plant grown in the soil contaminated with mine waste and sludge.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.11
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• pp.1075-1086
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• 2008

In order to investigate the applicability and suitability of the industrial by-products to apply mono-layer cover system for non-sanitary landfill sites, 6 different industrial by-products, such as construction waste, bottom ash, gypsum, blast furnace and steel manufacture slags, and stone powder sludge, were evaluated. Various physicochemical and hydrodynamic properties of the industrial byproducts were investigated. The environmental safety was monitored using batch and long-term leaching tests as well. In addition, the flexibility of plants was observed by cultivating them in the industrial by-products. The results for physicochemical properties indicate that most of the materials considered appeared to be suitable for landfill cover. Particularly, the concentration levels of hazardous elements regulated by the Korean Law for Waste Management did not exceed the regulatory limits in all target materials. In addition, the concentrations of regulated elements for the Korean Soil Conservation Law were examined below the regulatory limits in most of materials considered, except for the stone powder sludge. The results of batch and long-term experiments showed bottom ash and construction waste were the most suitable materials for landfill cover among the industrial by-products considered. The results of plant studies indicate that the bottom ash among industrial by-products considered was most effective in developing vegetation on landfill site, showing fast germination and large growth index. At the final covering system made of mixture of soil and bottom ash, the optimum application rate of farmyard manure was observed to be 40-50 Mg/ha.

• Journal of the Korea Convergence Society
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• v.8 no.2
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• pp.157-162
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• 2017

Inorganic stiffening agents were prepared by mixing paper sludge incineration ash, blast furnace slag fine powder quicklime, anhydrous gypsum and fly ash. The main components of the solidifying agent developed for sludge treatment were SiO, $Al_2O_3$, $TiO_2$, $Fe_2O_3$, $Mn_2O_3$, CaO, MgO, $Na_2O$, $K_2O$, $P_2O$, and $SO_3$. Unlike cement, the developed solidifying agent did not contain $Cr^{6+}$, which is known as a carcinogen. Heavy metals and oil contaminated soil were mixed with solidifying agent and cured for 7 days and the heavy metal content was below the environmental standard. Sewage sludge cake, food waste and solidifying agent were mixed with each other, and after 7 days curing, soil component test showed that the heavy metal content was below the environmental standard. After mixing the sludge, solidifying agent and additive mixture into the beaker, the ammonia concentration was measured to be 0 after 3 days.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.122-128
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• 2010

On the international provision on prohibition of ocean dumping of waste, tap water sludge has been buried or recycled on th low value added product as landfill. Due to the tap water sludge having high inorganic content, differing from the sewage sludge, it is possible to use as a usable resource by suitable process. We have studied on hydro thermal processing of tap water sludge with phosphoric acid and finally synthesize a artificial zeolite having a deodorization property. To use it as a building material, it has to be solidification. This study is on the properties of artificial zeolite synthsized and solidification properties by various types of solidifier. It is showed that the slaked lime is the best on setting property and its optimum content is 30-60 weight proportion. Solid by solidified by slaked lime has low strength and excellent deodorization performance, so it is possible to use as a functional pannel as gypsum board.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2006.05a
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• pp.78-85
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• 2006

In textile industries, waste effluent containing zinc is generated during the manufacture of rayon yarn from the wood pulp or cotton linters. Due to the strict environmental regulations and the presence of toxic metallic and other constituents, the discharge of industrial effluents in the sewage or disposal of solid sludge as landfill is restricted. Before recycling of zinc as zinc sulphate solution to the spinning-bath of the rayon manufacturing plant the zinc sulphate solution must be free from calcium, which is deleterious to the process as gypsum precipitates with the increase in concentration and forms scale in the bath. In the present work an attempt has been made to develop a process following solvent extraction technique using thiophosphinic extractants, Cyanex 272 and 302 modified with isodecanol and diluted in kerosene to recover zinc from rayon effluent. Various process parameters viz. extraction of zinc from different concentration of solution, distribution ratio, selective extraction, O/A ratio on extraction and stripping from the loaded organic, complex formation in the organic phase etc. have been studied to see the feasibility of the process. The extractant Cyanex 302 has been found selective for the recovery of 99.99% of zinc from the effluent above equilibrium pH 3.4 maintaining the O/A ratio of 1/30 leaving all the calcium in the raffinate. It selectively extracted zinc in the form of complex $[R_{2}Zn.3RH]_{org}$ and retained all the calcium in the aqueous raffinate. The zinc from the loaded Cyanex 302 can be stripped with 10% sulphuric acid at even O/A ratio of 10 without affecting the stripping efficiency. The stripped solution thus obtained could be recycled in the spinning bath of the rayon plant. The raffinate obtained after the recovery of zinc could be disposed safely without affacting environment.

• Resources Recycling
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• v.25 no.5
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• pp.44-49
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• 2016

Flue gas desulfurization(FGD) is an effective technique to remove $SO_2$ gases of coal-fired plants. Limestone is usually used as desulfurizing agent. In this study, we use the limestone sludge which is a by-product of steel industry in order to replace desulfurizing agent of FGD process. Physical and chemical characteristics analysis of desulfurizing agent was conducted. Desulfurizing agent using limestone sludge was fabricated by pre-treatment process and, then the agent was used on FGD process. Consequently, the tendency on the $SO_2$ concentration did not appear. And limestone sludge was considered as possible alternative agent for flue gas desulfurization process through absorber control system.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3631-3640
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• 2022

Uranium mill tailing ponds (UMTPs) are risk source of debris flow and a critical source of environmental U and Rn pollution. The technology of microbial induced calcium carbonate precipitation (MICP) has been extensively studied on reinforcement of UMTs, while little attention has been paid to the effects of MICP on U & Rn release, especially when incorporation of metakaolin and bacillus subtilis (MBS). In this study, the reinforcement and U & Rn immobilization role of MBS -MICP solidification in different grouting cycle for uranium mill tailings (UMTs) was comprehensively investigated. The results showed that under the action of about 166.7 g/L metakaolin and ~50% bacillus subtilis, the solidification cycle of MICP was shortened by 50%, the solidified bodies became brittle, and the axial stress increased by up to 7.9%, and U immobilization rates and Rn exhalation rates decrease by 12.6% and 0.8%, respectively. Therefore, the incorporation of MBS can enhance the triaxial compressive strength and improve the immobilization capacity of U and Rn of the UMTs bodies solidified during MICP, due to the reduction of pore volume and surface area, the formation of more crystals general gypsum and gismondine, as well as the enhancing of coprecipitation and encapsulation capacity.

• Economic and Environmental Geology
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• v.50 no.1
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• pp.27-34
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• 2017

Mineral carbonation for the storage of carbon dioxide is a CCS option that provides an alternative for the more widely advocated method of geological storage in underground formation. Carbonation of magnesium- or calcium-based minerals, especially the carbonation of waste materials and industrial by-products is expanding, even though total amounts of the industrial waste are too small to substantially reduce the $CO_2$ emissions. The mineral carbonation was performed with steelmaking reduction slag as starting material. The steelmaking reduction slag dissolution experiments were conducted in the $H_2SO_4$ and $NH_4NO_3$ solution with concentration range of 0.3 to 1 M at $100^{\circ}C$ and $150^{\circ}C$. The hydrothermal treatment was performed to the starting material via a modified direct aqueous carbonation process at the same leaching temperature. The initial pH of the solution was adjusted to 12 and $CO_2$ partial pressure was 1MPa for the carbonation. The carbonation rate after extracting $Ca^^{2+}$ under $NH_4NO_3$ was higher than that under $H_2SO_4$ and the carbonation rates in 1M $NH_4NO_3$ solution at $150^{\circ}C$ was dramatically enhanced about 93%. In this condition well-faceted rhombohedral calcite, and rod or flower-shaped aragonite were appeared together in products. As the concentration of $H_2SO_4$ increased, the formation of gypsum was predominant and the carbonation rate decreased sharply. Therefore it is considered that the selection of the leaching solution which does not affect the starting material is important in the carbonation reaction.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.1
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• pp.141-148
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• 2012

The objective of this study is to remove arsenate from artificially contaminated wastewater using CaAl-ettringite and CaAl-monosulfate which were synthesized in laboratory. The study was carried on the basis of solidification/stabilization of waste using cement. Monosulfate and ettringite are constituents of cement paste. The CaAl-ettringite has a chemical formula of $Ca_6Al_2O_6(SO_4)_3{\cdot}32H_2O$ and has a needle like morphology. Whereas CaAl-monosulfate $Ca_4Al_2O_6(SO_4){\cdot}12H_2O$ has layered double hydroxide structure (LDH) in which the mainlayer consists of Ca and Al and S as interlayer. Ettringite and monosulfate were synthesized by reaction of tricalcium aluminate and gypsum and hydrating this mixture at elevated temperature. The synthesized mineral were characterized by PXRD and FESEM to ensure purity. It was found that concentrations of As(V) in contaminated water were reduced from initial concentration of 1.335 mmol/L to 0.054 mmol/L and 0.300 mmol/L by CaAl-monosulfate and CaAl-ettringite respectively. The post experimental results of PXRD and FESEM analysis indicate that arsenate removal was by ion exchange.