• Membrane and Water Treatment
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• v.12 no.1
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• pp.1-9
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• 2021

This study optimized the chemical cleaning process of discarded RO membranes for reuse in less demanding separation processes. The effect of physicochemical parameters, including the temperature, cleaning time, pH of the cleaning solution, and addition of additives, on the cleaning process was investigated. The membrane performance was evaluated by testing the flux recovery rate and salt rejection before and after the cleaning process. High temperatures (45-50 ℃) resulted in a better flux recovery rate of 71% with more than 80% salt rejection. Equal time for acid and base cleaning 3-3 h presented a 72.43% flux recovery rate with salt rejection above 85%. During acid and base cleaning, the best results were achieved at pH values of 3.0 and 12.0, respectively. Moreover, 0.05% concentration of ethylenediaminetetraacetic acid presented 72.3% flux recovery, while 69.2% flux was achieved using sodium dodecyl sulfate with a concentration of 0.5%; both showed >80% salt rejection, indicating no damage to the active layer of the membrane. Conversely, 0.5% concentration of sodium percarbonate showed 83.1% flux recovery and 0.005% concentration of sodium hypochlorite presented 85.2% flux recovery, while a high concentration of these chemicals resulted in oxidation of the membrane that caused a reduction in salt rejection.

• Membrane and Water Treatment
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• v.13 no.1
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• pp.51-62
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• 2022

Vacuum-assisted air gap membrane distillation (V-AGMD) has the potential to achieve higher flux and productivity than conventional air gap membrane distillation (AGMD). Nevertheless, there is not much information on technical aspects of V-AGMD operation. Accordingly, this study aims to analyze the effect of membrane deformation on flux in V-AGMD operation. Experiments were carried out using a bench-scale V-AGMD system. Statistical models were applied to understand the flux behaviors. Statistical models based on MLR, GNN, and MLFNN techniques were developed to describe the experimental data. Results showed that the flux increased by up to 4 times with the application of vacuum in V-AGMD compared with conventional AGMD. The flux in both AGMD and V-AGMD is affected by the difference between the air gap pressure and the saturation pressure of water vapor, but their dependences were different. In V-AGMD, the membranes were found to be deformed due to the vacuum pressure because they were not fully supported by the spacer. As a result, the deformation reduced the effective air gap width. Nevertheless, the rejection and LEP were not changed even if the deformation occurred. The flux behaviors in V-AGMD were successfully interpreted by the GNN and MLFNN models. According to the model calculations, the relative impact of the membrane deformation ranges from 10.3% to 16.1%.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.7
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• pp.495-502
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• 2013

This work was performed to investigate proper condition of coagulation treatment as UF process pretreatment that consider UF permeate flux and residual Al concentration. The coagulant used an alum as $Al_2(SO_4)_3{\cdot}16H_2O$ and PACl (r = 1.5) made this study. The experiment was tested in adjusting conditions such as alum dose, flocculation time and coagulation pH of seawater. Consequently, higher coagulant dose lead to elevation of UF permeate flux while residual aluminium also increased in condition of pH 8.0. The most suitable condition which has a good permeate flux and low residual aluminium, in this works, was coagulant dose of 0.7 mg/L (as Al, alum) and 1.2 mg/L (as Al, PACl) and coagulation pH 6.5. In addition, applying the flocculation time with 1.2 mg/L of PACI reduced. The flocculation time reduced UF permeate flux in using alum.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.478-500
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• 1994

The preparation of potassium hexatitanate whisker by flux method was investigated. In this study, 8 types synthesis of flux such as $V_2O_5$, $Bi_2O_3$, $B_2O_3$, $Pb_3O_4$, KCl, $K_4P_2O_7$, $K_2WO_4$ and $K_2MoO_4$ were tested to find a suitable flux for the synthesis of potassium hexatitanate whisker. Effects of various reaction variables such as reaction temperature, time, $TiO_2$ mole ratio to $K_2CO_3$, flux mole ratio to the mixture of $K_2CO_3$ and $TiO_2$, and slow-cooling treatment on the crystallization of potassium hexatitanate whisker were investigated. $K_2MoO_4$ and $K_2WO_4$ were better flux than others tested for the synthesis of potassium hexatitanate. In the presence of $K_2MoO_4$ or $K_2WO_4$ flux, the optimum condition for the synthesis of potassium hexatitanate whisker was that reaction temperature of $1000{\sim}1100^{\circ}C$, reaction time of 5 hours, $TiO_2$ mole ratio to $K_2CO_3$ of 6.0, and flux mole ratio to mixture ($K_2O+nTiO_2$) of 4.0. Slow-cooling treatment showed good effect on the growth of long fibrous potassium hexatitanate.

• Korean Journal of Environmental Agriculture
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• v.32 no.4
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• pp.252-259
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• 2013

BACKGROUND: Salt accumulation in coastal reclaimed soil can decrease plant growth and productivity, which could lead to considerable variation of methane($CH_4$) emission in a rice paddy. The objective of this study was to evaluate the effect of salt concentration on $CH_4$ emission in a coastal reclaimed soil. METHODS AND RESULTS: The effect of salt concentration on $CH_4$ emission and rice growth characteristics was studied by pot test, which packed by reclaimed paddy soils collected from Galsa, Hadong, Gyeongnam province. Electrical conductivity(EC) of each treatment was controlled by 0.98, 2.25, 5.05 and 9.48 dS/m and $CH_4$ emission was characterized a week interval by closed chamber method during rice cultivation. The $CH_4$ emission rate was significantly decreased with increase of salt accumulation, but total $CH_4$ flux in EC 5.50 dS/m treatment was lower than those of EC 9.48 dS/m treatment. It seems because of higher content of water soluble $SO{_4}^{2-}$ in EC 5.50 dS/m treatment than those of EC 9.48 dS/m treatment. Rice growth and grain yield were significantly decreased with increase of salt accumulation. Soil properties, especially EC and pH were negatively correlated with $CH_4$ flux, while rice growth characteristics like plant height and tiller number show significantly positive correlation with $CH_4$ flux. CONCLUSION(S): Conclusively, salt accumulation significantly decreased $CH_4$ flux in a rice paddy, which could be useful information for evaluating $CH_4$ flux in reclaimed area in Korea.

• Membrane and Water Treatment
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• v.3 no.3
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• pp.141-149
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• 2012

The aeration provided in a Submerged Membrane Bioreactor (SMBR) improves membrane filtration by creating turbulence on the membrane surface and reducing membrane resistance. However, conventional hollow fiber membrane modules are generally packed in a vertical orientation which limits membrane scouring efficiency, especially when aeration is provided in the axial direction. In the present research, 3 innovative hollow-fiber membrane modules, each with a different membrane orientation, were developed to improve membrane scouring efficiency and enhance permeate flux. Pilot testing was performed to investigate the permeate flux versus time relationship over a 7-day period under different intermittent modes. The results indicated that the best module experienced an overall permeate flux decline of 3.3% after 7 days; the other two modules declined by 13.3% and 18.3%. The lower percentage of permeate flux decline indicated that permeate productivity could be sustained for a longer period of time. As a result, the operational costs associated with membrane cleaning and membrane replacement could be reduced over the lifespan of the module.

• Journal of computational fluids engineering
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• v.12 no.2
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• pp.26-31
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• 2007

A comparative study on the treatment of the turbulent heat flux with the elliptic blending second-moment closure for a natural convection flow is performed. Three cases of different treating the turbulent heat flux are considered. Those are the generalized gradient diffusion hypothesis (GGDH), the algebraic flux model (AFM) and the differential flux model (DFM). The constants in the models are adjusted with a primary emphasis placed on the accuracy of predicting the local Nusselt number. These models are implemented in a computer code specially designed for evaluation of turbulent models. Calculations are performed for a turbulent natural convection in the 1:5 rectangular cavity and the calculated results are compared with the available experimental data. The results show that the three models produce nearly the same accuracy of solutions. These results show that the GGDH, AFM and DFM models for treating the turbulent heat flux are sufficient for this simple shear flow where the shear production is dominant. It is observed that, in the weakly stratified region at the center zone of the cavity, the vertical velocity fluctuation is nearly zero in the GGDH solutions, which shows that the GGDH model may not be suitable for the strongly stratified flow. Thus, further study on the strongly stratified flow should be followed.

• Biotechnology and Bioprocess Engineering:BBE
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• v.2 no.2
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• pp.136-140
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• 1997

Direct membrane separation using nonwoven fabric was applied to saline wastewater treatment by an activated sludge process. A nonwoven fabric module was immersed in an aeration tank. The part of treated was filtered through the module by suction and the rest of that was separated by a settling tank. Various F/M ratios and salt concentrations were applied to investigate stable flux as well as pollutant removal. The pollutant removal efficiencies of nonwoven fabric separation was not affected by F/M ratios and salt concentrations and was higher than that of settling tank separation. The decline in flux was seemed to be caused by the biofilm on nonwoven fabric surface.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.53-59
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• 2023

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has no effect on normal cells, but selectively can induce apoptosis in tumor cells. Gartanin, a xanthone compound in mangosteen, has been shown to inhibit cancer cell growth by arresting the cell cycle and inducing autophage. In this study, we revealed that gartanin can sensitize TRAIL-induced human liver cancer cell death. We also found that gartanin enhances DR5 expression, a death receptor for TRAIL. This effect appears to be related to CHOP activation associated with the response of endoplasmic reticulum stress. Gartanin treatment also inhibited p62 protein expression and cleaved LC3 to activate autophagy flux, which is related with TRAIL-induced cell death. Pretreatment with autophagy flux inhibitor, LY294002, inhibited gartanin-induced DR5 expression. In summary, our results reveal that the combined treatment of gartanin and TRAIL can be a valuable tool for cancer treatment.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.1
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• pp.25-30
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• 2005

In order to decrease the high costs of membrane process, we have tried to develop two alternatives to membrane; a cartridge type filter and a metal membrane were tested for the high permeation flux with low cost and low energy. This research mainly focused on three points; 1) operation with high permeation flux by using of a cartridge type filter and a metal membrane, 2) removals of the filterable organic materials (FOC) by pretreatments for the membrane fouling control, and 3) advanced wastewater treatment by SMBR process with intermittent aeration and high MLSS. An Intermittently aerated membrane bioreactor using a submerged micro filter (cartridge type) was applied in laboratory scale for the advanced wastewater treatment. To minimize membrane fouling, intermittent aeration was applied inside of the filter with $3.0kg_f/cm^2$. The experiments was conducted for 6 months with three different HRTs (8, 10, 12 hr) and high MLSS of 6,000 and 10,000mg/L. The filtration process could be operated up to 50 days with permeation flux of 500LMH. Regardless of the operating conditions, more than 95% of COD, BOD and SS were removed. Fast and complete nitrification was accomplished, and denitrification was appeared to be the rate-limiting step. More than 75% T-N could be removed due to the endogenous denitrification. T-P removal efficiency was increased to 80% under the condition of MLSS 10,000mg/L.