• Resources Recycling
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• v.19 no.1
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• pp.40-48
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• 2010

It was investigated that effects of NaOH concentration on synthesis of mesoporous materials using municipal solid waste incinerator ash slag (MSWI-ash slag). In order to increase the purity and maximize the amount of extracted Si content the raw MSWI-ash slag was mechanically activated. Extraction of Si from the MSWI-ash slag was carried out by alkali treatment using concentrated NaOH solution, which varied from 1M to 4M. Physical properties (i.e., pore size, specific surface area and total pore volume) of the synthesized mesoporous silica were also evaluated as a function of NaOH concentration via BET, SEM, TEM and small-angle X-ray scattering analyses. Over the entire range of NaOH concentration investigated (i.e., 1-4M), the synthesized mesoporous materials were determined to be SBA-15, which exhibited a hexagonal structure with the pore size of approximately 7 nm. On the other hand, specific surface area and total pore volume increased with NaOH concentration up to 3M while the values decreased at 4M, indicating that the optimal NaOH concentration for the synthesized mesoporous silica was approximately 3M. Further comparison analysis between two conditions (3M versus 4M) showed that the decrease in two physical properties at 4M NaOH concentration was likely due to the potential inhibition by excess Na ions on the formation of mesophase and the consequent increase of pore wall thickness by remaining Si ions.

• Korean Journal of Materials Research
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• v.29 no.3
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• pp.167-174
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• 2019

To improve the performance of carbon nanofibers as electrode material in electrical double-layer capacitors (EDLCs), we prepare three types of samples with different pore control by electrospinning. The speciments display different surface structures, melting behavior, and electrochemical performance according to the process. Carbon nanofibers with two complex treatment processes show improved performance over the other samples. The mesoporous carbon nanofibers (sample C), which have the optimal conditions, have a high sepecific surface area of $696m^2g^{-1}$, a high average pore diameter of 6.28 nm, and a high mesopore volume ratio of 87.1%. In addition, the electrochemical properties have a high specific capacitance of $110.1F\;g^{-1}$ at a current density of $0.1A\;g^{-1}$ and an excellent cycling stability of 84.8% after 3,000 cycles at a current density of $0.1A\;g^{-1}$. Thus, we explain the improved electrochemical performance by the higher reaction area due to an increased surface area and a faster diffusion path due to the increased volume fraction of the mesopores. Consequently, the mesoporous carbon nanofibers are demonstrated to be a very promising material for use as electrode materials of high-performance EDLCs.

• Membrane and Water Treatment
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• v.6 no.3
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• pp.205-224
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• 2015

A novel hydrophilic poly (vinylidene fluoride)/poly (p-phenylene terephthalamide) (PVDF/PPTA) blend membrane was prepared by in situ polycondensation of p-phenylene diamine (PPD) and terephthaloyl chloride (TPC) in PVDF solution with subsequent nonsolvent induced phase separation (NIPS) process. For comparison, conventional solution blend membrane was prepared directly by adding PVDF powder into PPTA polycondensation solution. Blend membranes were characterized by means of viscometry, X-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM). The effects of different blending methods on membrane performance including water contact angle (WCA), mechanical strength, anti-fouling and anti-compression properties were investigated and compared. Stronger interactions between PVDF and PPTA in in situ blend membranes were verified by viscosity and XPS analysis. The incorporation of PPTA accelerated the demixing rate and caused the formation of a more porous structure in blend membranes. In situ blend membranes exhibited better hydrophilicity and higher tensile strength. The optimal values of WCA and tensile strength were $65^{\circ}$ and 34.1 MPa, which were reduced by 26.1% and increased by 26.3% compared with pure PVDF membrane. Additionally, antifouling properties of in situ blend membranes were greatly improved than pure PVDF membrane with an increasing of flux recovery ratio by 25%. Excellent anti-compression properties were obtained in in situ blend membranes with a stable pore morphology. The correlations among membrane formation mechanism, structure and performance were also discussed.

• Korean Journal of Materials Research
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• v.28 no.10
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• pp.544-550
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• 2018

The passivation of AZ91D Mg alloys by plasma anodization requires deliberate choice of process parameters due to the presence of large amounts of structural defects. We study the dependence of pore formation, surface roughness and corrosion resistance on voltage by comparing the direct current (DC) mode and the pulse wave (pulse) mode in which anodization is performed. In the DC plasma anodization mode, the thickness of the electrolytic oxide film of the AZ91D alloy is uneven. In the pulse mode, the thickness is relatively uniform and the formed thin film has a three-layer structure. The pulse mode creates less roughness, uniform thickness and improved corrosion resistance. Thus, the change of power mode from DC to pulse at 150 V decreases the surface roughness (Ra) from $0.9{\mu}m$ to $0.1{\mu}m$ and increases the corrosion resistance in rating number (RN) from 5 to 9.5. Our study shows that an optimal oxide film can be obtained with a pulse voltage of 150 V, which produces an excellent coating on the AZ91D casting alloy.

• Macromolecular Research
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• v.17 no.12
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• pp.1010-1014
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• 2009

Monodispersed microparticles with a poly(D,L-lactide-co-glycolide) (PLGA) core and a poly(ethyl 2-cyanoacrylate) (PE2CA) shell were prepared by Shirasu porous glass (SPG) membrane emulsification to reduce the initial burst release of doxorubicin (DOX). Solution mixtures with different weight ratios of PLGA polymer and E2CA monomer were permeated under pressure through an SPG membrane with $1.9\;{\mu}m$ pore size into a continuous water phase with sodium lauryl sulfate as a surfactant. Core-shell structured microparticles were formed by the mechanism of anionic interfacial polymerization of E2CA and precipitation of both polymers. The average diameter of the resulting microparticles with various PLGA:E2CA ratios ranged from 1.42 to $2.73\;{\mu}m$. The morphology and core-shell structure of the microparticles were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The DOX release profiles revealed that the microparticles with an equivalent PLGA:E2CA weight ratio of 1:1 exhibited the optimal condition to reduce the initial burst of DOX. The initial release rate of DOX was dependent on the PLGA:E2CA ratio, and was minimized at a 1:1 ratio.

• Membrane and Water Treatment
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• v.10 no.2
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• pp.127-137
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• 2019

The D2EHPA/TBP co-extractants immobilized PolyHIPE membrane can be used for the selective separation of Mn (II) from Co (II). By solvent-nonsolvent method, D2EHPA/TBP co-extractants can be effectively immobilized into PolyHIPE membrane. The pore structure of PolyHIPE membrane and the presence of TBP enhance the stability of immobilized co-extractants. The optimal operating conditions for the separation of Mn (II) and Co (II) are feeding phase at pH 5.5, sulfuric acid concentration in the stripping phase of about 50 g/L and stirring speed at 400 rpm. The D2EHPA/TBP co-extractants ratio of 5:1 shows synergetic effect on Mn/Co separation factor about 22.74. The removal rate and recovery rate of Mn (II) is about 98.4 and 97.1%, respectively, while for Co (II) the transport efficiency is insignificant. The kinetic study of Mn (II) transport shows that high initial flux, $J_f^o=80.1({\mu}mol/m^2s)$, and maxima stripping flux, $J_s^{max}=20.8({\mu}mol/m^2s)$, can be achieved with D2EHPA/TBP co-extractants immobilized PolyHIPE membrane. The stability and reusability study shows that the membrane can maintain a long term performance with high efficiency. High purity of Co (II) and Mn (II) can be recovered from the feeding phase and stripping phase, respectively.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.261-265
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• 2014

As the need for miniaturization in water purification filter increases, the development of filter media for single filtration with multiple function was strongly required. In this study, the molded activated carbon composed of single unit was manufactured by extrusion-sintering process, and then the flow rate, density and porosity were investigated using the molded activated carbon manufactured at various extrusion temperature. We confirmed that it was possible to manufacture the single unit-molded activated carbon when the extrusion temperature was $140{\sim}230^{\circ}C$ more than $133^{\circ}C$ being of polymer binder melting point, and the optimal extrusion temperature for the molded activated carbon with maximum flow rate was $170^{\circ}C$ since the molded activated carbon had low density and high through porosity. Also we confirmed that the flow rate through the molded activated carbon was strongly dependent upon through pore porosity compared to total porosity for the molded activated carbon.

• Membrane Journal
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• v.16 no.1
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• pp.31-38
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• 2006

The ceramic microfiltration system with periodic $N_2$-back-flushing was operated for treating paper wastewater discharged from a company making toilet papers by recycling milk or juice cartons. Two kinds of alumina membranes with 7 channels used here for recycling paper wastewater. The optimal filtration time interval for HC04 membrane with $0.4{\mu}m$ pore size was lower value of 4 min than 16 min for HC10 with $1.0{\mu}m$ pore size at fixed back-flushing time 40 sec, trans-membrane pressure $1.0kg_f/cm^2$ and back-flushing pressure $5.0kg_f/cm^2$. From the results of TMP effect at fixed filtration time interval and back-flushing time, the lower TMP was better on membrane fouling because high TMP could make easily membrane cake and fouling inside membrane structure. However, we could acquire the highest volume of total permeate at the highest TMP for the reason that TMP was driving force in our filtration system to treat paper wastewater. Then the permeate water of low turbidity was acquired in our microfiltration system using multi channels ceramic membranes, and the treated water could be reused in paper process.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.39-48
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• 2020

The present study investigates the chemical reaction and performance of ternary blended binders by mixing ferronickel slag. Cement was replaced using ground granulated blast furnace slag and ferronickel slag, combined up to 50% of the replacement rate. The blended cements were tested by setting times, length change, compressive strength at 1, 3, 7, 28 days. X-ray diffraction and scanning electron microscope were conducted for detecting hydration products while the MIP and microhydation heat were used for examining morphological characteristics. The results showed that by adding ferronickel slag, Pozzolanic reaction occurred, forming a dense pore structure and the effect of reducing hydration heat and dry shrinkage was also found. The compressive strength at 28 days was lower than that of 100% OPC control specimen (OSP0), but ternary blended cements showed no significant difference compared to binary blended (OSP50). If the optimal mix is derived later and used for the purpose, the potential for use as a cement binder is expected.

• Journal of the Korean Solar Energy Society
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• v.34 no.5
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• pp.73-80
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• 2014

This study introduces and analyzes the geothermal energy availability in Non-active volcanic region. Jeju island in Korea is situated in non-active volcanic region. The island is composed of rock with high pore and clinker, scoria geological layer formed by volcanic activity about two million ago. Volcanic geological layers with porous characteristics have air, vapor, water and a underground structure through which air or water can move easily. For this reason, it is probable that the mechanism of energy acquisition is by convective heat transfer. For this presumption, the availability of underground air as energy source has been studied here through theoretical analysis and experimental data. The energy output of our system ranged from 2,485,076 kJ/day to 4,060,978 kJ/day monitored using variable velocity air flow controller. Our system has capability to be a reliable energy source irrespective of environmental changes. Consequently, underground air can be utilized for energy source and provide the optimal design of heating/cooling system.