Chemical characterization of ultrafiltration membranes by spectroscopic techniques (original) (raw)
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Fouling analysis of polysulfone ultrafiltration membranes used for drinking water treatment
Water Supply, 2011
Natural organic matter (NOM) plays a significant role in the fouling of ultrafiltration membranes in drinking water treatment processes. For a better understanding of the interaction between fractional components of NOM and polysulfone (PS) ultrafiltration membranes used for drinking water treatment, fouling and especially the physically irreversible fouling of natural organic matter were investigated. Resin fractionation, fluorescence excitation–emission matrix (EEM) spectroscopy, fourier transform infrared spectroscopy (FTIR), contact angle and a scanning electron microscope (SEM) were employed to identify the potential foulants. The results showed that humic acid and fulvic acid of small size were likely to permeate the membrane, while the hydrophobic fraction of humic and fulvic acid and aromatic proteins tended to be rejected and retained. Organic compounds such as proteins, humic substances, and polysaccharide-like materials, were all detected in the fouling layer. The physica...
Surface modification of polysulfone ultrafiltration membranes and fouling by BSA solutions
Five different chemically modified versions of polysulfone were prepared via two different homogeneous chemical reaction pathways. They, together with the base polymer, were cast as membranes by a phase-inversion process. The surface energies of these membranes, as measured by contact angles, were used to characterize the different membranes. Streaming-potential measurements were obtained to probe the surface charge of the membranes. The surface roughness of each membrane was also determined by atomic-force microscopy. Each membrane was then exposed to deionized water, 0.08 g/1 bovine serum albumin solution and deionized water using a standard filtration procedure to simulate protein fouling and cleaning potential. Both the chemistry and the size of the grafted molecules were correlated with respect to volumetric flux during ultrafiltration of protein solutions. Surface roughness seemed to be important for filtering pure water. Hysteresis between advancing and receding contact angles increased with hydrophilicity of the membrane surfaces. One possible explanation could be that surface reorientation was more likely with hydrophilic than with hydrophobic membranes. The membrane modified by direct sulfonation had the lowest surface energy and the shortest grafted chain length and exhibited the highest volumetric flux with BSA solution. It was also the easiest to clean and exhibited the highest initial flux recovery by stirring (91%) and backflush (99%) methods with deionized water. In most cases, backflushing rather than stirring was more effective in recovering the water flux.
Journal of Applied Polymer Science, 2003
Polyethersulfone (PES) ultrafiltration (UF) membranes with and without surface-modifying macromolecules (SMMs) were prepared and characterized in terms of the mean pore size and pore-size distribution, surface porosity, and pore density. The results demonstrated that both the mean pore size and the molecular weight cutoff (MWCO) of the SMM-modified membranes are lower than those of the corresponding unmodified ones. Membrane fouling tests with humic acid as the foulant indicated that the permeate flux reduction of the SMM-modified membranes was much less than that of the unmodified ones. Therefore, fouling was more severe for the unmodified membranes. Moreover, the dry weight of the humic acid deposited on the membrane surface was considerably higher for the unmodified membranes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3132–3138, 2003
Influence of Inorganic Additives on the Performance of Polysulfone Ultrafiltration Membrane
Jurnal Teknologi, 2013
The influence of zinc oxide and silver (I) oxide in polysulfone ultrafiltration membrane was studied. The membranes were prepared via phase inversion method. The morphology, surface roughness, hydrophillicity and antibacterial properties of membrane were investigated using SEM, AFM and contact angle device consecutively. It was found that membrane with zinc oxide additive has excellent pure water flux as compared to silver (I) oxide. However silver (I) oxide has better humic acid rejection due to the tradeoff effect. SEM-EDX for PSf/silver (I) oxide reveals that the accumulation of silver on top area in cross section of membrane while for zinc oxide seems more concentrated on the bottom. Interestingly, the AFM results support the previous result when PSf/zinc oxide showed better surface roughness on the top of the membrane. Eventhough zinc oxide is known one of antibacterial material, however from qualitative experiment using disc diffusion test (e-coli), there is no inhibition ring...
Adsorptive fouling of modified and unmodified commercial polymeric ultrafiltration membranes
Journal of Membrane Science, 1999
The fouling tendency, due to adsorption on the pore walls, of two pairs of modi®ed and unmodi®ed ultra®ltration membranes, with similar observed retentions determined by dextran and gel permeation chromatography, was studied. The membranes investigated were made of modi®ed and unmodi®ed polyaramide (PA) and modi®ed and unmodi®ed polyvinylidene¯uoride (PVDF). The PVDF membrane was surface-modi®ed and the PA membrane was made from a modi®ed polymer solution. Membrane modi®cation was used to reduce fouling by adsorption. Octanoic acid was used as the fouling substance, representing a large number of small, hydrophobic compounds. It is demonstrated in this investigation that membrane modi®cation is not always successful. It was determined that at lower concentrations of octanoic acid, the modi®ed PA membrane exhibits a smaller fouling tendency than the unmodi®ed PA membrane, while the result is reversed for concentrations above 60% of the saturation concentration. The fouling tendency of the unmodi®ed PVDF membrane is much lower than that of the modi®ed PVDF membrane at all concentrations. The cross-sections of the membranes were visually examined with scanning electron microscopy, but no difference could be observed between the modi®ed and unmodi®ed membranes. The membranes were also examined with Fourier transform infrared spectroscopy. The spectra of the two PA membranes were different, while no difference was observed for the unmodi®ed and surface-modi®ed PVDF membranes. Remains of octanoic acid were found in the membranes, although they had been thoroughly rinsed with deionized water and the initial pure water¯ux was recovered.
Water Quality Research Journal
Surface modified polyethersulfone (PES) membranes via the addition of different hydrophiLic Surface Modifying Macromolecules (LSMMs) have been developed by Matsuura, Narbaitz and co-workers. This study compares the performance of the best PES-LSMM membrane with nine commercial ultrafiltration membranes manufactured using five different types of base polymers (polyethersulfone, polysulfone, celluloseacetate, polyacrylonitrile and cellulose) in the same range of molecular weight cutoff (MWCO) (from 40 to 120 kDal). All membranes were characterized by using atomic force microscopy, contact angle measurements, solute transport analysis and then evaluated through fouling tests with Ottawa River water (ORW). While PES-LSMM membranes had much lower initial flux than the commercial membranes, they had the highest total organic carbon (TOC) rejection (80%) and the lowest flux reduction (62%). For the commercial membranes, the range of TOC rejections and flux reductions were 62 to 80% and 68 ...
Impact of chemical cleaning on properties and functioning of polyethersulfone membranes
Journal of Membrane Science, 2007
In water treatment processes, membrane cleaning is of paramount economic and scientific importance. Traditionally, ultrafiltration membranes fouled with organic matter are cleaned with hypochlorite, an operation that usually results in complete restoration of the initial flux. Although the cleaned membranes are deemed suitable for continued operation, membrane integrity may have been damaged (manifested as holes in the membrane skin) by the cleaning process. To assess the degree of chemical resistance of polyethersulfone (PES)-based membranes, the membranes were fouled with bovine serum albumin and cleaned with various concentrations of sodium hypochlorite. The properties of pristine, fouled, and cleaned membranes were compared by spectrochemical analysis, mechanical testing, microscopy imaging, and streaming potential and permeability measurements. Our results suggest that cleaning does have a major impact on the performance and properties of PES membranes. Effective removal of the foulant from the membrane surface resulted in more severe fouling and increased electronegativity of the cleaned membrane. The increased electronegativity was related to chain scission of the polymer, leading to the formation of phenyl sulfonate. The deterioration in the mechanical strength of hypochlorite-treated membranes indicated a loss of membrane integrity. The transmembrane streaming potential technique provided information on membrane pore size, cleaning efficiency, and membrane integrity.
Effects of Water as Non-Solvent Additive on Performance of Polysulfone Ultrafiltration Membrane
Advanced Materials Research, 2012
In this work, polysulfone ultrafiltration membranes were prepared via simple phase inversion with distilled water as non-solvent additive. The main reason for the addition of water in polysulfone dope solution preparation was to enhance the membranes structure. In the dope, 15 wt. % of polysulfone was used and water was varied up to 6 wt. %. The effects of water on morphology, porosity and tensile properties were investigated in detail. From the porosity test, results showed that the addition of water has improved membrane porosity up to 53 %. The FESEM images revealed that membrane morphology has also been modified. However, the tensile properties of membrane decreased as water content increased which may be due to the porosity interaction between polysulfone/NMP with water.
Chemical functionalization of polymers after the synthesis of membranes has great importance for various applications separative processes of industrial or environmental interest. Polysulfone (PSf) is one of the most applied polymers for separative processes used especially in membrane technology, due to its excellent chemical, mechanical and thermal properties. The functionalization of PSf makes it very attractive to give special characteristics due to their high hydrophobicity and membrane fouling fast. In this work PSf perform functionalization by the method of Friedel-Crafts with choroethyl chloroacetate and subsequent hydrolysis of chloroetyl group (-OH). After synthesizing the membrane is characterized by FT-IR ATR spectroscopy, 1 HNMR, contact angle measurements, retention of polydisperse solutes and hydraulic permeability. Finally, the membranes tests fouling are performed with an oily wastewater emulsion. The fouling tests showed that the functionalized PSf membrane demonst...
Effect of adsorption of organic matter on fouling of ultrafiltration membranes
Journal of Membrane Science, 1993
This study examined the effect of organic matter adsorption on ultrafiltration membrane blocking and fouling. A hydrophilic cellulose derivative membrane and a hydrophobic acrylic polymer membrane, both with a hollow fiber configuration, were tested. The experiments were performed using synthetic, particle free solutions of a low molecular weight dextran and tannic acid. The effect on fouling of pretreatment of the synthetic solutions by preozonation and by preadsorption on powder activated carbon (PAC) was also evaluated. The level of adsorption was assessed by measuring the quantity of each compound adsorbed, reversibly or irreversibly, by mass or per surface unit of membrane. The level of fouling was assessed by monitoring the loss in specific flux under actual filtration conditions. The study showed that the highest level of adsorption occurred in the ultrafiltration of the aromatic compounds through the hydrophobic membrane. The filtration of a 15 mg/l tannic acid solution led to the adsorption of 6 mg of tannic acid per gram of dry membrane. This resulted in severe fouling with an 80 percent loss of initial flux after only three hours of filtration, despite the absence of particulate matter. Preozonation was very effective in preventing adsorption of tannic acid by-products on the hydrophilic membrane, but only partially reduced the fouling caused by adsorption of the hydrophobic membrane. Similarly, preaclsorption on PAC was effective when the membrane used for subsequent filtration was hydrophilic.