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UV irradiation is one of the procedures that has been considered for membrane surface graft polymerization. It is commonly utilized for enhancing the wettability of polyethersulfone (PES) membranes. In this research study, the monomer methacrylic acid (MAA) was used for the UV grafting process of a commercial NF2 PES membrane for the preparation of a forward osmosis (FO) membrane. Three different monomer concentrations and three different UV irradiation times were considered. The intrinsic characteristics of both the surface-modified and pristine membranes were determined via a non-pressurized test method. Compared to the NF2 PES, the surface of the modified membranes was rendered more hydrophilic, as the measured water contact angle was reduced considerably from 65° to 32-58°. The membrane surface modification was also confirmed by the data collected from other techniques, such as atomic force microscopy (AFM), field emission-scanning electron microscope (FESEM) and Fourier-transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). Additionally, the modified membranes exhibited a greater water permeate flux (Jw) compared to the NF2 PES membrane. In this study, the water permeability (A), solute permeability (B) and structural parameter (S) were determined via a two-stage FO non-pressurized test method, changing the membrane orientation. Compared to the FO pressurized test, smaller S values were obtained with significantly high A and B values for the two non-pressurized tests. The adopted method in the current study is more adequate for determining the intrinsic characteristics of FO membranes., Ministry of Higher Education Malaysia, Universiti Malaysia Pahang, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2009 Elsevier B.V. One of the authors M. Khayet is thankful to the University Complutense of Madrid (UCM) for the grant., The experimental design and response surface methodology (RSM) have been used to develop predictive models for simulation and optimization of nanofiltration modified membranes by UV-initiated graft polymerization technique. The objective is to prepare optimum membrane with high nanofiltration performance and low fouling. The factors considered for experimental design were the UV-irradiation time, UV-intensity and the concentration of the monomer N-vinyl-2-pyrrolidone (NVP) in aqueous grafting solution. The dip method has been followed for membrane grafting employing 365 nm wavelength UV-lamp. The significant factors were optimized using a central composite design of orthogonal type. The nanofiltration membrane performance has been studied using humic acid model solution 15 mg/L at a pH value 7. Pure water permeation flux, permeate flux when using humic acid feed solution, rejection factor and irreversible membrane fouling parameters have been determined. The nanofiltration performance index and the recoverable flux ratio have been considered as responses. The quadratic models between each response and the independent parameters were developed and the response surface models were tested with analysis of variance (ANOVA). By applying the desirability function approach maximal output responses have been predicted and confirmed experimentally. The obtained optimal point was located in the valid region and the experimental confirmation tests were conducted showing a good accordance between the predicted optimal points and the experimental ones. The optimum operating conditions determined were a monomer concentration of 5.13 g/L, UV-intensity of 16.57 x 10(4) mW/m(2) and UV-irradiation time of 37.9 s. Under these optimal conditions maximum nanofiltration performance index, 84.88 L/m(2) h and recoverable flux ratio 88.14% have been achieved. These values are the highest compared to all experimental data carried out within the overall region of experimentation. The optimum, University Complutense of Madrid (UCM), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2009 Elsevier B.V. We would like to thank the Ministry of Higher Education, Malaysia for supporting Mazrul Abu Seman's study. We also like to thank the University Complutense of Madrid (UCM) for financially supporting M. Khayet during his stay in the UK., Nanofiltration polyester thin-film composite membranes have been prepared by interfacial polymerization using commercial polyethersulfone membrane support. Different monomer bisphenol A (BPA) concentrations in the aqueous solution and various interfacial polymerization times in the organic solution containing trimesoyl chloride (TMC) were studied. The success of the conducted interfacial polymerization procedure was corroborated by FTIR-ATR. Irreversible fouling of both the unmodified polyethersulfone and the modified polyester thin-film composite polyethersulfone membranes have been studied using humic acid model solutions at different pH values. It was observed that polyester thin-film composite membranes exhibited practically no tendency to be irreversibly fouled by humic acid molecules at neutral environment. However, the permeate flux was decreased and the irreversible fouling factor was enhanced with decreasing the pH to a value of 3., Ministry of Higher Education, Malaysia, University Complutense of Madrid (UCM), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2010 Elsevier B.V. We would like to thank the Ministry of Higher Education, Malaysia for supporting Mazrul Abu Seman's study. M. Khayet is thankful to the University Complutense of Madrid (UCM) for the grant., UV-photografting using two different monomers, acrylic acid and N-vinylpyrrolidone, with different concentrations in an aqueous solution and various irradiation times were studied. Irreversible fouling of both the un-grafted polyethersulfone and the UV-grafted membranes have been studied using humic acid model solutions at two different pH values; 7 and 3. It was observed that the UV-grafted membranes exhibited practically less tendency to be irreversibly fouled by humic acid molecules at pH 7. However at the acidic condition of pH 3, some membranes exhibited a higher degree of fouling more than the un-grafted membrane, especially for membranes with higher roughness values. The smaller pore size generated after UV-grafting of polyethersulfone membrane did not significantly affect humic acid removal due to the larger humic acid molecular size., Ministry of Higher Education, Malaysia, University Complutense of Madrid (UCM), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 The Authors. Published by Taylor & Francis., Fouling of natural organic matter is one of the common problems in water treatment plant. Despite physical and chemical treatment normally used to recover the flux loss, membrane surface properties also not less important to be considered. In this study, UV-photografting technique was applied to modify commercial nanofiltration (NF) membrane surface in order to reduce fouling tendency. Neutral hydrophilic N-vinylpyrrolidone has been chosen as the monomer for the UV-photografting. The result revealed that the grafted membrane at optimum conditions exhibits low humic acid fouling tendency compared with the unmodified membrane. In addition, both the unmodified and the UV-grafted polyethersulfone NF membranes were characterized in terms of structural properties (pore size, r(p,) and ratio of membrane thickness to porosity, x/A(k)) using Pore Model in order to evaluate the effect of UV-photografting modification on structural parameters and indirectly influence the membrane performance and fouling as well., Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2010 Elsevier B.V. One of the authors M. Khayet is thankful to the University Complutense of Madrid (UCM) for the grant., Nanofiltration polyethersulfone membrane has been modified by means of UV-initiated graft polymerization technique using the weakly acidic monomer acrylic acid and the immersion method. Different UV-irradiation times and acrylic acid concentrations in water were studied. Both the unmodified and the modified polyethersulfone nanofiltration membranes were characterized by attenuated total reflection-Fourier transform infrared spectra (FTIR-ATR) and atomic force microscopy (AFM). Irreversible membrane fouling has been studied by using humic acid model solutions at two different pH values (7 and 3). It was observed that some modified membranes exhibited higher permeance than the unmodified polyethersulfone nanofiltration membrane. The humic acid rejection factor was higher for all modified membranes compared to the unmodified membrane and the irreversible fouling by humic acid molecules was reduced after UV-initiated graft polymerization by acrylic acid., University Complutense of Madrid (UCM), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2010 Elsevier B.V. We would like to thank the Ministry of Higher Education, Malaysia for providing Mazrul Abu Seman with a scholarship to carry out this work., Two types of bisphenol monomers, Bisphenol A (BPA) and Tetramethyl Bisphenol A (TMBPA), with different concentrations of bisphenol aqueous solution (0.5% to 2.%w/v) and various interfacial polymerisation times (10 s, 30 s and 60 s) in the fixed 0.15%w/v organic solution of trimesoyl chloride (TMC)-hexane were studied. Irreversible fouling of both unmodified polyethersulfone NFPES10 and modified polyester thin-film composite polyethersulfone membranes were studied using humic acid model solutions at two different pH values, pH 7 and pH 3. It was observed that polyester thin-film composite membranes prepared by BPA exhibited fewer tendencies for irreversible fouling by humic acid molecules at neutral environment compared to unmodified NFPES10 and TMBPA-polyester series. This is most probably due to high electrostatic repulsion force between negatively charged of BPA-polyester layer and highly negative charged of humic acid at pH7. However, some modified membranes with rougher surfaces were severely fouled by humic acid molecules at acidic environment, pH 3. Under this acidic environment, carboxylic acid groups of humic acid lost their charge and the macromolecules of humic acid have smaller macromolecular configuration due to the increased hydrophobicity and reduced inter-chain electrostatic repulsion. Thus the molecules of humic acid may be preferentially accumulated at the valleys of the rougher membrane surface blocking them and resulting in a more severe fouling. In addition, the modification also affected membrane pore size and pore size distribution as shown by AFM images. It was also observed that the smaller pore size generated after modification does not have significant effect on humic acid removal due to the larger size of humic acid molecules. All the modified membranes posses smaller pore size than the unmodified NFPES10 (1.47 nm) in the range of 0.8-1.34 nm., Ministry of Higher Education, Malaysia, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub