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CONTENTS
Volume 2, Number 1, January 2011
 

Abstract
The deficiency of clean water is a major global concern because all the living creatures rely on the drinkable water for survival. On top of this, abundant of clean water supply is also necessary for household, metropolitan inhabitants, industry, and agriculture. Among many purification processes, advances in low-energy membrane separation technology appear to be the most effective solution for water crisis because membranes have been widely recognized as one of the most direct and feasible approaches for clean water production. The aim of this article is to give an overview of (1) two new emerging membrane technologies for water reuse and desalination by forward osmosis (FO) and membrane distillation (MD), and (2) the molecular engineering and development of highly permeable hollow fiber membranes, with polyvinylidene fluoride (PVDF) and polybenzimidazole (PBI) as the main focuses for the aforementioned applications in National University of Singapore (NUS). This article presents the main results of membrane module design, separation performance, membrane characteristics, chemical modification and spinning conditions to produce novel hollow fiber membranes for FO and MD applications. As two potential solutions, MD and FO may be synergistically combined to form a hybrid system as a sustainable alternative technology for fresh water production.

Key Words
membrane distillation; forward osmosis; desalination; hollow fiber membranes; separation; nanofiltration.

Address
Dep. of Chemical & Biomolecular Engineering, National University of Singapore 4 Engineering Drive 4, Singapore 117576, Singapore

Abstract
PES UF membranes containing silver were prepared to impart antibacterial properties for waste water treatment. Asymmetric membranes for antibacterial application were prepared from polyethersulfone (PES) and silver nitrate (AgNO3) (PES/AgNO3=15/2 by weight) solution in N-Methyl-2-pyrrolidone (NMP) via simple wet phase inversion technique. These membranes were characterized by polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) of different molecular weights (1000 ppm in water) at room temperature and on operating pressure of 5 bars. It was observed that the water flux of PES-AgNO3 membrane is slightly lower than virgin PES but still increased linearly with the increment of pressure applied. The morphology of the resulting membranes was examined using Field-Emission Scanning Electron Microscope (FESEM) coupled with Energy Dispersive Spectroscopy (EDS). Elemental analysis using EDS proved that silver is successfully loaded on the membrane surfaces. Due to the success of loading silver on membrane surfaces, antibacterial activities were evaluated via agar diffusion method against Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus) culture. By incorporating 2 wt% of silver nitrate, PES-AgNO3 showed significant inhibition ring on both E.coli and S.aureus. Filtration of E.coli solution (OD 0.31) showed satisfactory rejection data with ~100% inhibition growth after 24 hours incubation at 37oC. Resultant membranes also exhibit better tensile strength (compared to virgin PES) up to 71% may be due to the suggested interactions. The residual silver during fabrication was measured using ICP-MS and result showed that the residual silver content of PES-AgNO3 membrane was only ~1% of the original silver added in the polymer solution. These studies have shown that PES-AgNO3 UF membranes are potential in improving the filtration in water treatment.

Key Words
polyethersulfone; silver nitrate; ultrafiltration; antibacterial.

Address
H. Basri: Advanced Membrane Technology Research Center (AMTEC), Universiti Teknologi Malaysia, Science and Mathematics Department, Faculty of Science, Art and Heritage
Universiti Tun Hussein Onn Malaysia
A.F. Ismail: Advanced Membrane Technology Research Center (AMTEC), Universiti Teknologi Malaysia, Faculty of Petroleum and Renewable Energy Engineering, Universiti Teknologi Malaysia
M. Aziz: Advanced Membrane Technology Research Center (AMTEC), Universiti Teknologi Malaysia, Chemistry Department, Faculty of Science, Universiti Teknologi Malaysia

Abstract
We investigated about the utilization improvement of the PDMS and fluoropolymers by mutual application in environmental analysis. We were conducted the direct fluorination with mild condition on the PDMS films and analyzed its surfaces before and after fluorination. The results of FTIR and SEM analysis on the PDMS films showed that the film surfaces were fluorinated without irreversible deformation by the fluorination. During the fluorination, the measured contact angles of water and several alcohols on the PDMS films decreased with time and that of most alcohols decreased to 0 after 30 minutes. The surface energy of fluorinated PDMS films has increased by 2 times. Also, we investigated the influence factors on the change of permeation rate of water through PDMS tubes with time. It was observed that the change of permeation rate of water through PDMS tube was affected by temperature, water phase and spatial distribution of water. From these results, we could verify the principal causes of the decrease of permeation rate of water through PDMS tube with time and proposed a new experimental setup for reducing the variation of permeation rate of water less than 2%.

Key Words
PDMS; fluoropolymers; direct fluorination; permeation rate; PDMS permeation tube.

Address
Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology 373-1 Guseong-Dong, Yuseong-Gu, Daejeon 305-701, Korea

Abstract
An alternative ultrafiltration membrane integrity test was already developed in laboratory scale. It is based on the use of magnetic nanoparticles (Fe3O4) and measurement of magnetic susceptibility. The mean size of nanoparticles used is around 35 nm and they show a good disparity between 20 and 100 nm. In this paper, validation of this membrane integrity monitoring method was achieved by industrialscale tests. Two holes with 0.6 mm internal diameter in a module containing 10 000 fibers (35 m2 surface area) was efficiently detected by injecting 750 mL of 1.7 g.L−1 nanoparticle solution during 2s when the test was operated at low TMP (0.096 bar, corresponding to a flux of 2.2 m3.h−1). In addition, it has been demonstrated that within the detectable range, this membrane integrity test with magnetic nanoparticles has a very rapid response time. The response time depends on the permeate flux and the dead-volume of the pilot. This membrane integrity test, with the advantages of on-line operation, high detection sensitivity, detection specificity and very low influence on membrane fouling, seems to be suitable for large scale drinking water plants.

Key Words
drinking water; integrity test; magnetic nanoparticles; magnetic susceptibility; industrial scale.

Address
H. Guo, Y. Wyart, P. Moulin: Universite Paul Cezanne Aix Marseille, Laboratoire de Mecanique, Modelisation et Procedes Propres (M2P2 – UMR-CNRS 6181), Europole de l\'Arbois, BP. 80, Batiment Laennec, Hall C 13545 Aix en Provence Cedex 04, France
F. Nauleau: SAUR, 1 avenue Eugene Freyssinet, 78064 Saint Quentin en Yvelines Cedex, France

Abstract
A spiral wound nanofiltration (NF) membrane (GE Osmonics, DK 4040F) was used to remove pesticides from water. Several solutions of single pesticides and their mixtures were prepared. The pesticides initial concentration ranged from ca. 50 ng/L (single pesticide) to ca. 700 ng/L (as sum of 14 pesticides) and progressively increased with time since the NF experiments were carried out in a concentration mode up to a Volume Concentration Ratio, VCR = 10. Permeate flux and pesticides retention were evaluated as a function of the Volume Concentration Ratio. The permeate flux did not practically change by varying VCR. Pesticide retention was found to be around 97-98% both in the cases of single pesticide solutions and different mixtures of pollutants, and was not affected by the VCR. Pesticides concentration in permeate samples was found to be lower than the maximum concentration level fixed in European directive.

Key Words
membrane; nanofiltration; pesticide removal.

Address
Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31
16146 Genoa, Italy

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