• Membrane and Water Treatment
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• v.1 no.1
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• pp.49-60
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• 2010

In this study, response surface methodology (RSM) was performed in NF membrane process to evaluate the separation efficiency of membrane in the removal of salt and reactive dye by varying different variables such as pressure, temperature, pH, dye concentration and salt concentration. The significant level of both the main effects and the interaction were observed by analysis of variance (ANOVA) approach. Based on the statistical analysis, the results have provided valuable information on the relationship between these variables and the performances of membrane. The rejection of salt was found to be greatly influenced by pressure, pH and salt concentration whereas the dye rejection was relatively constant in between 96.22 and 99.43% regardless of the changes in the variables. The water flux on the other hand was found to be affected by the pressure and salt concentration. It is also found that the model predictions were in good agreement with the experimental data, indicating the validity of these models in predicting membrane performances prior to the real filtration process.

• Membrane Journal
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• v.27 no.5
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• pp.449-457
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• 2017

In this study, the 10 stages stacked module was designed by increasing the number of unit cells in the membrane capacitive deionization(MCDI) process. The aminated polysulfone and sulfonated poly(ether ether ketone) were synthesized and coated on porous carbon electrode by casting method. The salt removal efficiency was measured for the 10 stage stacked module under the operation conditions of adsorption voltage and time, desorption voltage and time, flow rate and concentration of feed water, and di-valent solutions including $CaSO_4$, $MgCl_2$ and tap water. Typically, when 100 mg/L of NaCl as the feed was used, the salt removal efficiency was 98.3% at a flow rate of 100 mL/min, the adsorption condition of 1.2 V/3 min and desorption condition of -0.5 V/5 min.

• Environmental Engineering Research
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• v.17 no.2
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• pp.111-116
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• 2012

This study investigates the complete removal of nitrate and the recovery of valuable ammonium salt by the combination of nanoscale zero-valent iron (NZVI) and a membrane contactor system. The NZVI used for the experiments was prepared by chemical reduction without a stabilizing agent. The main end-product of nitrate reduction by NZVI was ammonia, and the solution pH was stably maintained around 10.5. Effective removal of ammonia was possible with the polytetrafluoroethylene membrane contactor system in all tested conditions. Among the various operation parameters including influent pH, concentration, temperature, and contact time, contact time and solution pH showed significant effects on the ammonia removal mechanism. Also, the osmotic distillation phenomena that deteriorate the mass transfer efficiency could be minimized by pre-heating the influent wastewater. The ammonia removal rate could be maximized by optimizing operation conditions and changing the membrane configuration. The combination of NZVI and the membrane contactor system could be a solution for nitrate removal and the recovery of valuable products.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.829-835
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• 2016

An excess in the nutrients such as nitrogen and phosphate leads to a phenomenon called eutrophication. In order to avoid this, numerous methods have been used to remove excess nutrients in the water. In this study, the use of a chemical method was assessed through the formation of magnesium ammonium phosphate. The difference in the removal efficiency of seawater and sea salt solution as primary sources of $Mg^{2+}$ ions and $Ca^{2+}$ ions for the formation of magnesium ammonium phosphate (MAP) and hydroxyapatite (HAP) respectively, were observed, taking into account the changes in pH and concentration. The results showed that seawater removed about 90 % phosphate and less than 50 % ammonia in sewage water condition, whereas the sea salt solution removed almost 90 % phosphate and 70 % ammonia in solution at pH 9 and 10 mM concentration of sea salt which further increases as the optimum ${Mg/PO_4}^{3-}$, ${NH_4}^+$ ratio reaches 2. The difference in the removal efficiency of seawater and sea salt was due to the fact that the set-ups were prepared in different conditions. This study suggests that both seawater and sea salt can be used to remove nutrients from the water. The relatively higher removal of phosphate can be explained by the formation of HAP from free $Ca^{2+}$ ions initially present in seawater and sea salt solution.

• Membrane Journal
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• v.28 no.4
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• pp.271-278
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• 2018

In this study, the carbon electrodes using activated carbon fibers (ACFs) were prepared for the capacitive deionization process. The Polyvinylidene fluoride (PVDF) was used as the binder and the mixed ACFs with proper solvent was cast on the commercial graphite sheets to prepare the carbon electrodes. At this moment, the different particle sizes of ACFs were applied and the mixing ratio of solvent, PVDF and ACFs, 80 : 2 : 18 and 80 : 5 : 15, were used for the electrode preparation. Then their salt removal efficiencies were characterized under the various operating conditions, adsorption potential and time, desorption potential and time, concentration of feed NaCl solution and flow rate as well. Typically, the salt removal efficiency of 53.6% were obtained at the particle size below $32{\mu}m$, mixing ratio 80 : 2 : 18, adsorption 1.2 V and 3 min, desorption -0.1V and 1 min, and 15 mL/min flow rate of NaCl 100 mg/L.

• Membrane Journal
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• v.24 no.4
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• pp.332-339
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• 2014

In this study, an anion-exchange ionomer solution was developed by employing poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as the base material for the improvement of the capacitive deionization (CDI) performances. It was found that prepared quaternized PPO (QPPO) exhibited excellent ion conductivity superior to that of a commercial anion-exchange membrane (AMX, Astom Corp., Japan) and also the electrochemical properties were shown to be comparable with each other. The CDI tests were conducted by employing the porous carbon electrode coated with the ionomer solution and the result showed the high salt removal efficiency of about 94.9%. By comparing the desalination efficiencies in conventional CDI, membrane CDI (MCDI) with a commercial anion-exchange membrane, and coated CDI (CCDI) employing the porous carbon electrode coated with QPPO, it was confirmed that CCDI shows the high salt removal performance improved by 52.1% and 18.3% compared with those of conventional CDI and MCDI, respectively.

• Membrane and Water Treatment
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• v.7 no.2
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• pp.115-126
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• 2016

In this study, computational fluid dynamics (CFD) analysis was conducted to investigate the flow pattern and to find the occurrence of dead zones in an existing capacitive deionization (CDI) cell. Newly designed cells-specifically designed to avoid dead zones-were analyzed by CFD in accordance with the flow rates of 15, 25 and 35 ml/min. Next, the separation performances between the existing and newly designed cell were compared by conducting CDI experiments in terms of salt removal efficiency at the same flow rates. Then, the computational and experimental results were compared to each other. The salt removal efficiencies of the hexagon flow channel 1 (HFC1) and hexagon flow channel 2 (HFC2) were increased 88-124% at 15 ml/min and 49-50% at 25 ml/min, respectively. There was no difference between the existing cell and the foursquare flow cell (FFC) at 35 ml/min.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.1
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• pp.75-80
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• 2002

In this study, the initial number of bacteria before ozone sterilizing shows 290 per $1m{\ell}$ in RUN 1 and RUN 2 equally, but the removal rate shows more than 50% in RUN 1, and 100% in RUN 2 respectively when ozone injection amount is $0.28mg/{\ell}$. It is regarded as a satisfactory result that E-coli concentration without ozone contact is 890, rapid removal effect of E-coli is observed in $0.28mg/{\ell}$ of ozone, and E-coli is removed perfectly in $0.84mg/{\ell}$ of ozone. It is thought that an excellent efficiency is obtained for vibrio alginolyticus because the initial number of bacteria before ozone contact is positive, but it is altered to negative after ozone contact. CODcr shows the tendency which is somewhat reduced as the ozone injection is increased, but the general effect is appeared not so much, and it is thought that the tendency is caused by the reason that sea water contains much salt which is estimated as a component of CODcr, therefore it is regarded that ozone contact has not an important effect on salinity. It is thought that the frequency of changing salt water in the fish preserve of a sliced raw fish restaurant can be reduced to under the standard because NTU of 7 days after sea water injection is 0.70 in the experiment of turbidity, hut more than 50% of turbidity removal efficiency is appeared at $0.28mg/{\ell}$ of ozone injection, and it shows 70% at $0.84mg/{\ell}$ of ozone injection in RUN 1 and RUN 2 commonly.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.3
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• pp.256-263
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• 2010

The study was performed to evaluate the effects of chloride concentrations on the ultimate aerobic biodegradability and to use the result as the fundamental data for sea food wastewater treatment. When the organic removal efficiency by chloride concentrations (1,400~18,000 mg/L) was evaluated, microbes adapted to the saline at ${\leq}$ 6,000 mg/L of chloride but treatment efficiency was not improved at ${\geq}$ 12,000 mg/L of chloride because of delayed reaction time. Functional coefficient $Y_I$ of non-biodegradable soluble organic and inert material production coefficient Yp by microbe metabolism increased as chloride concentrations increased. Soluble organic matter ratio by chloride concentration (0~18,000 mg/L) was 10.8~13.1%, inert material production efficiency by microbes metabolism was evaluated as 7.0~24.6%. $NH_3$-N removal efficiencies were 96.2, 96.5, 90.2 and 90.3% using original wastewater HRT 18 hr, 6,000 mg/L chloride concentration HRT 22 hr, 12,000 mg/L chloride concentration HRT 30 hr, and 18,000 mg/L chloride concentration HRT 45 hr, respectively. Nitrification process was more sensitive to salt concentration than organic matter removal to salt concentration. Under ${\geq}$ 6,000 mg/L chloride concentration, conversion rate from $NO_s$-N to $NO_2$-N was low.

• Environmental Engineering Research
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• v.14 no.4
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• pp.220-225
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• 2009

The water quality in eutrophic lakes is affected by serious problems, such as abnormal increasing of Cyanobacteria. The purpose of this study was to investigate the possibility of a modified flotation system using a hybrid technique formed by chemical compounds and an electrostatic bridge. Therefore, experiments using the hybrid technique were performed to measure the zeta potential value on the phytoplankton surface and the removal efficiencies of phytoplankton, ammonia nitrogen, nitrate nitrogen and phosphoric acid. The results were as follows: Firstly, the zeta potential of M.aeruginosa was observed to approach charge neutralization due to adhesion of magnesium hydroxide precipitate on the phytoplankton surface in the pH range 10.5 to 11. Secondly, the concentration of chlorophyll-a decreased from about 150 to 20${\mu}g$g/L, with a maximum removal efficiency of 84% due to coagulation with pH values higher than 10. Thirdly, the N$H_4$-N concentration was observed to decrease from 0.62 to 0.54mg-N/L (13%), and the P$O_4$-P concentration, which is a limiting factor to the formation of algae blooms, decreased from 0.27 to 0.02mg-P/L (92%). These findings suggest that the modified flotation system can be applied for the purification of the raw water of numerous lakes containing high phytoplankton populations and elevated pH.