• Membrane and Water Treatment
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• v.5 no.4
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• pp.235-250
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• 2014

The impacts of membrane degradation due to chlorine attack on the rejection of inorganic salts and trace organic contaminants by nanofiltration (NF) and reverse osmosis (RO) membranes were investigated in this study. The rejection of trace contaminants was examined at environmentally relevant concentrations. Changes in the membrane surface morphology were observed as a result of chlorine exposure. A small increase in rejection was consistently observed with all four membranes selected in this study after being exposed to a low concentration of hypochlorite (100 ppm). In contrast, a higher concentration of hypochlorite (i.e., 2000 ppm) could be detrimental to the membrane separation capacity. Membranes with severe chlorine impact showed a considerable decrease in rejection over filtration time, possibly due to rearrangement of the polyamide chains under the influence of chlorine degradation and filtration pressure. The reported results indicate that loose NF membranes are more sensitive to chlorine exposure than RO membranes. The impact of hypochlorite exposure (both positive and negative) on rejection is dependent on the strength of the hypochlorite solution and is more significant for the neutral carbamazepine compound than the negatively charged sulfamethoxazole.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.4
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• pp.313-318
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• 2006

A two-stage process of nanofiltration and water-splitting electrodialysis was investigated for lactic acid recovery from fermentation broth. In this process, sodium lactate is isolated from fermentation broth in the first stage of nanofiltration by using an NTR-729HF membrane, and then is converted to lactic acid in the second stage by water-splitting electrodialysis. To determine the optimal operating conditions for nanofiltration, the effects of pressure, lactate concentration, pH, and known added impurities were studied. Lactate rejection was less than 5%, magnesium rejection approximated 45%, and calcium rejection was at 40%. In subsequent water-splitting electrodialysis, both the sodium lactate conversion to lactic acid and sodium hydroxide recovery, were about 95%, with a power requirement of $0.9{\sim}1.0\; kWh$ per kg of lactate.

• Membrane Journal
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• v.29 no.6
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• pp.348-354
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• 2019

Recently, the application range of organic solvent nanofiltration (OSN) technology has been expanding, requiring membranes with better performance. In this work, thin film composite (TFC) OSN membrane was fabricated. First, ultrafiltration support membrane was prepared via nonsolvent-induced phase separation (NIPS) technique using polysulfone (PSf) and polyethersulfone (PES). Then, the effect of pore forming additives such as polyvinylpyrrolidone (PVP) and pluronic F-127 were employed to improve the membrane permeance. The well-known interfacial polymerization technique was employed using MPD-TMC chemistry to form a thin film on top of the fabricated support, and its solvent permeance and nanofiltration performance was characterized. It was found that polyethersulfone support exhibited more reliable performance compared to polysulfone, and PVP additive was more effective compared to Pluronic F-127. As for the oSN performance, polar aprotic solvents like acetonitrile show significantly higher flux (986.5 L·m^-2·h^-1·bar^-1) compared to water and EtOH (9.5 L·m^-2·h^-1·bar^-1).

• Membrane Journal
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• v.23 no.1
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• pp.92-99
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• 2013

In this study the nanofiltration (NF) membrane treatment of a sulfuric acid waste solutions containing copper ion ($Cu^{+2}$) discharging from the etching processes of the printed circuit board (PCB) manufacturing industry has been studied for the recycling of acid etching solution. SelRO MPS-34 4040 NF membrane from Koch company was tested to obtain the basic NF data for recycling of etching solution and separation efficiency (total rejection) of copper ion. NF experiments were carried out with a dead-end membrane filtration laboratory system. The pure water flux was increased with the increasing storage time in sulfuric acid solution and lowering pH of acid solution because of the enhancement of NF membrane damage by sulfuric acid. The permeate flux of acid solution was decreased with the increasing copper ion concentration. Total rejection of copper ion was decreased with the increasing storage time in sulfuric acid solution and copper ion concentration, and lowering the pH of acid solution. The total rejection of copper ion was decreased from initial 37% to 15% minimum value.

• Proceedings of the Membrane Society of Korea Conference
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• 2002.11a
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• pp.111-115
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• 2002

No Abstract, See Full Text

• Microbiology and Biotechnology Letters
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• v.27 no.4
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• pp.320-326
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• 1999

The effects of operating pressure, lactate concentration, impurities, and pH on solution flux and lactate rejection in nanofiltration were investigated with model sodium lactate solutions (lactate 10~200g/L) as a model system. In the tested range of pressure(80~140 psig), the solution flux was observed to be proportional to the operating pressure and the rejection of lactate increased only slightly with the pressure. Both of the flux and the rejection decreased with lactate concentration, while the recovery rate of lactate increased. The effects of glucose and yeast extract as impurities on lactate rejection were negligible, but the flux decreased significantly with the addition of yeast extract. At low lactate concentrations, the rejection of lactate increased with pH due to the increased repulsion (Donnan exclusion effect) between lactate ions and membrane surface. But, at high lactate concentrations, the donnan effect was observed to be overwhelmed by the effect of sodium ions added to adjust the pH, and the rejection of lactate decreased with pH. When fermentation broth containing about 89g/L of lactate was nanofiltered, the flux and the rejection of lactate were 2.8L/$m^2$h and 5%, respectively at 120psig. Both of them were slightly lower than those with model solutions. The recovery rate was 2.6mol/$m^2$h.

• Environmental Engineering Research
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• v.17 no.4
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• pp.185-190
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• 2012

Rejection characteristics of perchlorate ($ClO_4^-$) were examined for commercially available reverse osmosis (RO) and nanofiltration (NF) membranes. A bench-scale dead-end stirred-cell filtration system was employed to determine the toxic ion rejection and the membrane flux. Model water solutions were used to prepare $ClO_4^-$ solutions (approximately, $1,000{\mu}g/L$) in the presence of background salts (NaCl, $Na_2SO_4$, and $CaCl_2$) at various pH values (3.5, 7, and 9.5) and solution ionic strengths (0.001, 0.01, and 0.01 M NaCl) in the presence of natural organic matter (NOM). Rejection by the membranes increased with increasing solution pH owing to increasingly negative membrane charge. In addition, the rejection of the target ion by the membranes increased with increasing solution ionic strength. The rejection of $ClO_4^-$ was consistently higher for the RO membrane than for the NF membrane and $ClO_4^-$ rejection followed the order $CaCl_2$ < NaCl < $Na_2SO_4$ at conditions of constant pH and ionic strength for both the RO and NF membranes. The possible influence of NOM on $ClO_4^-$ rejection by the membranes was also explored.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.11a
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• pp.128-131
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• 2003

• Membrane and Water Treatment
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• v.5 no.2
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• pp.123-146
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• 2014

Safe water has becoming a competitive resource in many parts of the world due to increasing population, prolonged droughts, climate change etc. The development of economical and stable materials and methods for providing the fresh water in adequate amounts is the need of the water industry. Nanomaterials have unique characteristics e.g., large surface areas, size, shape, and dimensions etc. that make them particularly attractive for removing various contaminants from polluted waters. Nanotechnology based multifunctional and highly efficient membrane processes are providing affordable solutions in the new era that do not rely on large infrastructures or centralizes systems. The objective of the current study is to review the possible applications of the membrane based nanomaterials/composites for the removal of various contaminations from polluted waters. The article will briefly overview the availability and practice of different nanomaterials based membranes for removal of bacteria and viruses, organic compounds and inorganic solutes etc. present in surface water, ground water, seawater and/or industrial water. Finally, recommendations are made based on the current practices of nanofiltration membranes in water industry for a stand-alone membrane filtration system in removing various types of contaminants from polluted waters.

• Membrane and Water Treatment
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• v.7 no.3
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• pp.193-207
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• 2016

Boron is one of the most problematic inorganic pollutants and is difficult to remove in water. Strict standards have been imposed for boron content in water because of their high toxicity at high concentrations. Technologies using membrane processes such as reverse osmosis (RO) and nanofiltration (NF) have increasingly been employed in many industrial sectors. In this work, removal of boron from model water solutions was investigated using polyamide reverse osmosis and nanofiltration membranes. RO-AG, RO-SG, NF-90 and NF-HL membranes were used to reduce the boron from model water at different operational conditions. To understand the boron separation properties a characterization of the four membranes was performed by determining the pure water permeability, surface charge and molecular weight cut-off. Thereafter, the effect of feed pressure, concentration, ionic strength, nature of ions in solution and pH on the rejection of boron were studied. The rejection of boron can reach up to 90% for the three membranes AG, SG and NF-90 at pH = 11. The Spiegler-Kedem model was applied to experimental results to determine the reflection coefficient of the membrane ${\sigma}$ and the solute permeability $P_s$.