• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.7-12
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• 2004

Desalination system of revers osmosis(RO) membrane has been proven to be the most economical not only for the desalination of water containing salts, but also for the concentration of solute. RO membranes were traditionally made of inorganic polymers such. as cellulose acetate(CA), Polyamide(PA). To retain more minerals in deep ocean water, a new hybrid membrane composed of tourmaline film as organic material onto inorganic layer of CA polymer in asymmetric structure was developed for RO membrane process. The performance tests were carried out in the permeability of pure water and the rejection of NaCl solution to evaluate the adaptability for DOW desalination. The results of these basic tests show possibility to apply the new hybrid RO membrane for the desalination with function control.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.4
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• pp.303-310
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• 2017

Pressure retarded osmosis(PRO) has attracted much attention as potential technology to reduce the overall energy consumption for reverse osmosis(RO) desalination. The RO/PRO hybrid process is considered as the most logical next step for future desalination. The PRO process aims to harness the osmotic energy difference of two aqueous solutions separated by a semipermeable membrane. By using the concentrated water(RO brine) discharged from existing RO plants, the PRO process can effectively exploit a greater salinity gradient to reduce the energy cost of processing concentrated water. However, in order to use RO brine as the draw solution, PRO membrane must have high water flux and enough mechanical strength to withstand the high operational pressure. This study investigates the development of a thin film composite PRO membrane and spiral wound module for high power density. Also, the influence of membrane backing layer on the overall power density was studied using the characteristic factors of PRO membranes. Finally, the performance test of an 8-inch spiral wound module was carried out under various operating conditions(i.e. hydraulic pressure, flow rate, temperature). As the flow rate and temperature increased under the same hydraulic pressure, the PRO performance increased due to the growth of water permeability coefficient and osmotic pressure. For a high performance PRO system, in order to optimize the operating conditions, it is highly recommended that the flow pressure be minimized while the flow rate is maintained at a high level.

• Membrane and Water Treatment
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• v.11 no.4
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• pp.303-312
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• 2020

This study aims to investigate at a laboratory scale fluorides removal from an industrial wastewater having excessive F^- concentration through a hybrid process combining neutralization and membrane separation. For the membrane separation operation, both Reverse Osmosis (RO) and Nanofiltration (NF) were investigated and confronted. The optimized neutralization step with hydrated lime allowed reaching fluoride removal rates of 99.1± 0.4 %. To simulate continuous process, consecutive batch treatments with full recirculation of membrane process brines were conducted. Despite the relatively high super saturations with respect to CaF₂, no membrane cloaking was observed. The RO polishing treatment allowed decreasing the permeate fluoride concentration to 0.9± 0.3 mg/L with a fluoride rejection rate of 93± 2% at the optimal transmembrane pressure of around 100 psi. When NF membrane was used to treat neutralization filtrate, the permeate fluoride concentration dropped to 1.1± 0.4 mg/L with a fluoride rejection rate of 88± 5% at the optimal pressure of around 80 psi. Thus, with respect to RO, NF allowed roughly 20% decrease of the driving pressure at the expense of only 5% drop of rejection rate. Both NF and RO permeates at optimal operating transmembrane pressures respect environmental regulations for reject streams discharge into the environment.

• Journal of Korean Society on Water Environment
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• v.18 no.4
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• pp.387-394
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• 2002

The efficiency variation of UF(tubular)/RO(spiral wound) process using acrylic wastewater treated by photo-catalyst pretreatment and coagulant-filter-neutralization pretreatment processes were discussed wit the variation of appled pressure and temperature. Ultrafiltration tubular module using acrylic wastewater treated by photo-catalyst pretreatment and coagulant-filter-neutralization pretreatment processes was shown that COD and T-N were not highly affected with the variation of appled pressure and temperature. It was shown that removal efficiency of COD and T-N was low. Removal efficiency of TDS and turbidity with ultrafiltration tubular module was better with the acrylic wastewater by photo-catalyst pretreatment than acrylic wastewater by coagulant-filter-neutralization pretreatment. T-N and TDS were shown high removal efficiency in reverse osmosis membrane process.

• Journal of Korean Society on Water Environment
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• v.30 no.5
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• pp.517-523
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• 2014

In order to remove both nitrate and sulfate present in the concentrate of RO(reverse osmosis) process, a combined bio-regeneration and ion-exchange(IX) system was studied. For this purpose, both denitrifying bacteria(DNB) and sulfate reducing bacteria(SRB) were simultaneously cultivated in a bio-reactor under anaerobic conditions. When the IX column containing a nitrate-selective A520E resin was fully exhausted by nitrate and sulfate, the IX column was bio-regenerated by pumping the supernatant of the bio-reactor, which contains MLSS concentration of $125{\pm}25mg/L$, at the flowrate of 360 BV/hr. Even though the nitrate-selective A520E resin was used, the breakthrough curves of ionic species showed that sulfate was exhausted earlier than nitrate. The reason for this result is due to the fact that the concentration of sulfate in RO concentrate was 36 to 48 times higher than nitrate. The bio-reactor was successfully operated at a volumetric loading rate of 0.6 g $COD/l{\cdot}d$, nitrate-N loading rate of 0.13 g $NO_3{^-}-N/l{\cdot}d$, and sulfate loading rate of 0.08 g $SO_4{^{2-}}/l{\cdot}d$. The removal rate of SCOD, nitrate-N, sulfate was 90, 100, and 85%, respectively. When the virgin resin was fully exhausted and consecutively bio-regenerated for 2 days, 81% of nitrate and 93% of sulfate were reduced. When the virgin resin was repeatedly used up to 4 cycles of service and bio-regeneration, the ion-exchange capacity of bio-regenerated resin decreased to 95, 91, 88, and 81% of virgin resin.

• Membrane Journal
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• v.24 no.4
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• pp.317-324
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• 2014

It is very well known that the conventional polyamide (PA) thin film composite (TFC) reverse osmosis (RO) membranes have excellent permselective properties, but their chlorine tolerance is not good enough. In this study, to improve such chlorine tolerance, microporous membranes containing hydrophilic functional groups such as -COOH were used as a support to prepare PA TFC RO membranes, employing the conventional interfacial polymerization method. Meta-phenylene diamine (MPD) and 2,6-diamine toluene (2,6-DAT) were used as diamine monomers and tri-mesoyl chloride (TMC) as an acid monomer. The membranes prepared were characterized using various instrumental analytical methods and permeation test set-up. The flux obtained from the membranes prepared so was more than $1.0m^3/m^2day$ at 800 psi of operating pressure, while the salt rejection was over 99.0%. The chlorine tolerance of them was also found to be better than that of the membrane prepared by using conventional polysulfone support without hydrophilic functional groups.

• Membrane Journal
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• v.31 no.5
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• pp.315-326
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• 2021

Lithium ion battery (LIB) demands increase every year globally to reduce the burden on fossil fuels. LIBs are used in electric vehicles, stationary storage systems and various other applications. Lithium is available in seawater, salt lakes, and brines and its extraction using environmentally friendly and inexpensive methods will greatly relieve the pressure in lithium mining. Membrane separation processes, mainly nanofiltration (NF), is an effective way for the separation of lithium metal from solutions. Electrodialysis and electrolysis are other separation processes used for lithium separation. The process of reverse osmosis (RO) is already a well-established method for the desalination of seawater; therefore, modifying RO membranes to target lithium metals is an excellent alternative method in which the only bottleneck is the interfering presence of other metal elements in the solution. Selectively removing lithium by finding or developing suitable NF membranes can be challenging, but it is nonetheless an exciting area of research. This review discusses in detail about lithium recovery via nanofiltration, electrodialysis, electrolysis and other processes.

• Membrane Journal
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• v.32 no.4
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• pp.209-217
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• 2022

Ion exchange membrane (IEM) is an important class of membrane applied in batteries, fuel cells, chloride-alkali processes, etc to separate various mono and multivalent ions. The membrane process is based on the electrically driven force, green separation method, which is an emerging area in desalination of seawater and water treatment. Electrodialysis (ED) is a technique in which cations and anions move selectively along the IEM. Anion exchange membrane (AEM) is one of the important components of the ED process which is critical to enhancing the process efficiency. The introduction of cross-linking in the IEM improves the ion-selective separation performance due to the reduction of free volume. During the desalination of seawater by reverse osmosis (RO) process, there is a lot of dissolved salt present in the concentrate of RO. So, the ED process consisting of a monovalent cation-selective membrane reduces fouling and improves membrane flux. This review is divided into three sections such as electrodialysis (ED), anion exchange membrane (AEM), and cation exchange membrane (CEM).

• Membrane Journal
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• v.32 no.6
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• pp.390-400
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• 2022

Nanofiltration (NF) membranes are more popular than reverse osmosis (RO) membranes as they can be operated at much lower pressures for applications in treatment of wastewater from industries like food processing and pharmaceutical as well as municipal sewage water. The separation mechanism in case of NF membranes is based on solution diffusion as well as sieving, for which the crosslinking density of the thin film of the composite membrane is less then RO membrane. Unlike ceramic membranes, membrane fouling is one of the chronic problems that occur during the nanofiltration process in polymeric membranes. Membrane cleaning is done to get rid of reversible as well as irreversible fouling by treatment with sodium hypochlorite. Compared to polymeric membranes, ceramic membranes show higher stability against these agents. In this review different types of ceramic membrane applied wastewater treatment by NF process are discussed.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.7
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• pp.492-497
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• 2014

This study investigated removal characteristics of organic matters in pretreatment and reverse osmosis (RO) membrane processes for seawater desalination. Also, the influence of the changes in characteristics of organic matters on the membrane fouling was assessed. The pretreatment processes included dual media filtration (DMF), pressurized membrane filtration (MF), and submerged membrane filtration (SMF). Turbidity, UV absorption at 254 nm, dissolved organic carbon, size exclusion chromatography (SEC), fluorescence excitation emission matrix (FEEM), and transparent exopolymer particles (TEP) in raw and processed waters were analyzed. Ions and minerals were not removed by any pretreatment process tested, but were removed over 99% through the RO membrane process. Hydrophobic organics, which can play major role in organic membrane fouling, were relatively readily removed compared with hydrophilic ones. Membrane based pretreatment such as MF and SMF exhibited better removals of organics than conventional DMF. As the levels of organics in pretreated water decreased, the silt density index (SDI) decreased. MF treated water exhibited the lowest SDI value; this is possibly due to the lowest TEP ($0.1-0.4{\mu}m$) concentrations.