• Environmental Engineering Research
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• v.24 no.3
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• pp.434-442
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• 2019

The present study investigated a novel calcium hydroxide-coated dairy manure-derived biochar (Ca-BC) for adsorption of phosphate from water and dairy wastewater. The Ca-BC showed much higher adsorption of phosphate than that of dairy manure-derived biochar. The Ca-BC possessed mainly the calcium hydroxide and various functional groups resulting in high reactivity between phosphate and calcium hydroxide in the Ca-BC. The adsorption of phosphate onto Ca-BC followed pseudo-second order kinetic and Freundlich isotherm models indicating chemisorptive interaction occurred on energetically heterogeneous surface of Ca-BC. The maximum adsorption capacity of the Ca-BC was higher than those of iron oxide and zinc oxide-coated biochars, but lower than those of CaO- and MgO-coated biochars. However, the Ca-BC showed high reactivity per surface area for adsorption of phosphate indicating importance of surface functionalization of biochar. On the other hand, the adsorption of phosphate in dairy wastewater on Ca-BC was lower than that in water owing to competition between other anions in wastewater and phosphate. Overall, the Ca-BC would be a low cost and effective adsorbent for recovery of phosphate from water and wastewater.

• The Korean Journal of Ceramics
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• v.5 no.2
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• pp.125-130
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• 1999

After $SnO_2$ fine powder by precipitation method, Ca as crystallization inhibitor and Pd as catalyst were added to $SnO_2$ raw material by various methods. Thick film device was fabricated on the alumina substrate by mixing ethylene glycol and such mixed powders. The sensing characteristics of the device for methane gas were investigated. The most excellent gas sensing property was shown by the thick film device fabricated by Method 3 in which Ca and Pd doped $SnO_2$ powder is prepared by mixing $SnO_2$ powder, 0.1 wt% Ca acetate and 1 wt% $PdCl_2$ in deionized water and by calcining the mixture, after $Sn(OH)_4$ is dried at $110^{\circ}C$ for 36h. The sensitivity of the sensor fabricated with $SnO_2$-0.1 wt%Ca acetate-1wt%$PdCl_2$ powder heat-treated at $700^{\circ}C$ for 1h was about 86% for 5,000 ppm methane in air at $350^{\circ}C$ of the operating temperature. Response time and recovery were also excellent.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.4
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• pp.423-428
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• 2017

Vestibular compensation is a recovery process from vestibular symptoms over time after unilateral loss of peripheral vestibular end organs. The aim of the present study was to observe time-dependent changes in long-term potentiation (LTP) at Schaffer collateral-CA1 synapses in the CA1 area of the hippocampus during vestibular compensation. The input-output (I/O) relationships of fEPSP amplitudes and LTP induced by theta burst stimulation to Schaffer's collateral commissural fibers were evaluated from the CA1 area of hippocampal slices at 1 day, 1 week, and 1 month after unilateral labyrinthectomy (UL). The I/O relationships of fEPSPs in the CA1 area was significantly reduced within 1 week post-op and then showed a non-significant reduction at 1 month after UL. Compared with sham-operated animals, there was a significant reduction of LTP induction in the hippocampus at 1 day and 1 week after UL. However, LTP induction levels in the CA1 area of the hippocampus also returned to those of sham-operated animals 1 month following UL. These data suggest that unilateral injury of the peripheral vestibular end organs results in a transient deficit in synaptic plasticity in the CA1 hippocampal area at acute stages of vestibular compensation.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.404-412
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• 2020

Herein, the properties and self-healing performance of cement mortar incorporating calcium sulfoaluminate(CSA), crystalline admixture(CA), and magnesium oxide(MgO) were investigated. Mortar strength test and water permeability experiments were conducted to analyze self-healing performance of the mortar. Also, variation in crack width were measured via digital optical microscope observation. The hydration products formed in the crack via self-healing were analyzed using x-ray diffraction(XRD), thermogravimetry(TG), and digital optical microscope. The analysis revealed that compressive strength and tensile strength increased as CA substitutional ratio increased. However, in the case of MgO replacement, the compressive strength and tensile strength decreased as the CA substitution ratio increased. The products in the recovered cracks are found to be mostly Ca(OH)2, MgCO3, and CaCO3. CaCO3 was shown to be the main healing product and had a higher portion than Ca(OH)2 and MgCO3 in the recovery products. Moreover, the optimal mix derived via water permeability and crack width results was 8% CSA + 1% CA + 2.5% MgO.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.67-69
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• 2003

The magnetic properties of single- and poly-crystalline $La_{0.7}Sr_{0.3}MnO_3/Pr_{0.65}Ca_{0.35}MnO_3$ multilayered (ML) films, and composite (CP) $(La_{0.7}Sr_{0.3})_{0.5}(Pr_{0.65}Ca_{0.35}_{0.5}MnO_3$ films, prepared by laser ablation, have been investigated in a wide temperature range. It was shown that the transformation from an incoherent to a coherent interface in the ML films leads to an enhancement of the ferromagnetic coupling between layers and to a single-phase magnetic transition. The amorphous CP films demonstrate a paramagnetic behavior of the magnetization with a sharp peak at $T_{G}\approx$45 K, which was interpreted as the formation of Griffiths phase. A short-term annealing at $750^{\circ}C$ induced the complete crystallization of film, and a recovery of the ferromagnetic and the metal-insulator transitions.

• Korean Journal of Environmental Agriculture
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• v.16 no.3
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• pp.239-244
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• 1997

To develope more effective extraction methods for paraquat in soil, some modification methods were accomplished in two different types of soil. For extraction of tightly bound-paraquat, conc. HCl 70ml were added with different shaking times, and then $H_2SO_4$ reflux were performed for an hour. In this case, 60 minutes shaking were optimum and recovery were increased more $1.09{\sim}1.50$ folds(84.0% in high clay contents soil, but 96.7% in low clay contents soil) and the long-time consuming step, filtration were easily done, with decreasing filtration time were shorter 4.6 folds(ca. $11{\sim}14min.$). than general paraquat analytical method(ca. $55{\sim}65min.$). And only $H_2O_2$ digestion with different volume and refluxing time resulted in recovery increasing. Nevertheless, considering analyst's safety, 30ml of $H_2O_2$ addition and 30 minutes reflux were regarded as optimum condition. Although, Kjeldahl digestion with $H_2O_2$ showed relatively high recovery, it is not significant statistically. For extraction of loosely bound-paraquat, 0.01, 0.1, 1.0, 10.0M of $NH_4Cl$ and of $CaCl_2$ compared with $1.5{\sim}24hr$ of different shaking time. There were no loosely bound residues of paraquat.

• Resources Recycling
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• v.6 no.3
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• pp.3-8
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• 1997

The EA.F. sleelmaking slag (slag that follow) of a cnmvany 1 Co.. containzd a simple substance of a metal, wustlte (FeO), magnetite (Fe,O,), gehlenite (CaAl,SiO,), monlicellite (CaMgSiO,), dc. To recovere a metal (Fe grade . t95%) in the slag, it is desirable that the particles of a metal are isolated from thc slag and madc for a liberated subslance. Then, the liberaled melal is easlly recoveled by a magnetic separation. If thc rcclarnalcd slag, the sizc of which ranges under 40 nun, have a mulli-stage crushing, the most of a metal in thc slag is simply isolaled as a liberated subslance. If the mad, lhat is a liberated subslance and a sphere, is recovered by a magnetic field intensity. the minimum intensity, at which a metal is attracted, is approximately IOOG and did no1 dcpcnd on the particle size of a metad in the same particles. TIe recovered material. that contdined a iron (Fe) over 95% is a metal which is crushed slag by l00G in the multi-stage. If the magnetic field intcns~ty increase, the recovery mcrcasc, but the concentration grade decrease Bewusc thc concentration eams more and more impurities, iron oxide and the coml~ound of alkali earth element. 'll~ercforc If the rccla~nated slag have the multi-stage crushing, the metal is almostly recovered in the crushed slag by lO0G on each particles. If the slag, used as a rcclamatian lhat is a amount of 350,000 tan from I Co., was undcr the multistage crushing and then separaled by 100gauss, it is possible to recova a metal approximately 2.500 Ion, lhat is 0.73% of n ~eclamated slag. in 304.7 mm particles and to recover 4.200 tan in 0.3-1.7 mm particles , that is 1.2% nf a rcclamated slag, in a year. Therefore, ihe told recoverable meld is 6,700 ton, that is 19% of a reclmated slag, in a year, too.

• Resources Recycling
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• v.17 no.2
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• pp.46-54
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• 2008

It is well known that PCB (Printed Circuit Board) is a complex mixture of various metals. In this study, pyro-metallurgical process was investigated to extract valuable metallic components from the PCB scrap. PCB scrap was shredded and oxidized to remove plastic materials, and then, quantitative analysis were made. 15 mass %$Al_2O_3-45$ mass %CaO-40 mass %$SiO_2$ and 32 mass %$SiO_2-20$ mass %$Al_2O_3-38$ mass %CaO-10 mass %MgO, were chosen as basic slag compositions which are determined based on the quantitative analysis of PCB scrap. During experiments a super kanthal rotating furnace was used to melt and separate metallic components. Moreover the revolution effect on was the recovery of valuable metals from PCB scrap also investigated.

• Resources Recycling
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• v.16 no.2 s.76
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• pp.32-39
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• 2007

The measurement of physicochemical properties of ASR incineration ash has been carried dot and the preparation of light-weight material has also been performed using ASR ash for recycling point of view as building or construction materials. For this aim, chemical composition, particle size distribution, and heavy metal leachability were examined for 2 bottom ashes and 4 fly ashes obtained from the domestic ASR incinerator. In the present work, attempt has been made to prepare the lightweight material using boiler ash as a raw material, which is prepared by forming the mixture of boiler ash, lightweisht filler and inorganic binder and followed by calcination at elevated temperature. As a result, the content of Cu in bottom ash was as high as about 3wt% so that the recovery of Cu from ash was required. The major compound of SDR #5 and Bag filter #6 was found to be $CaCl_2{\cdot}Ca(OH)_2{\cdot}H_2O\;and\;CaCl_2{\cdot}4H_2O$, respectively. It is thought that heavy metal teachability of lightweight material prepared with boiler ash was significantly decreased due to the encapsulation or stabilization of heavy metal compounds.

• Journal of Soil and Groundwater Environment
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• v.15 no.5
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• pp.8-15
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• 2010

The purpose of this research is to check the validation of an auto-analysis method combined with aqua regia digestion apparatus for improvement of water distillation method used as a fluorine test of soil. Fluorine contents of CaO used in the pretreatment course of water distillation method were 120 mg/kg ~ 5,064 mg/kg at the blank test, which was exceeded up to maximum 12.5 times of the soil standard, so it was estimated due to a effect of fluorine existing as impurities of CaO. The recovery test of the same samples indicated that water distillation method and auto-analysis method were 134.5mg/kg and 161.7mg/kg respectively, the recovery ratio of the latter was 16.8% higher than the formal. The validation test of two methods satisfied the standard, but auto analysis method was excellent more than distillation method. Also, auto analysis method could save a analysis time up to maximum 4.7 times by comparison with water distillation method.