Fouling Resistance Properties Research Articles

Probing Molecular-Level Surface Structures of Polyethersulfone/Pluronic F127 Blends Using Sum-Frequency Generation Vibrational Spectroscopy

We blended Pluronic F127 into polyethersulfone (PES) to improve surface properties of PES, which has been extensively used in biomaterial and other applications. The molecular surface structures of PES/Pluronic F127 blends have been investigated by sum-frequency generation (SFG) vibrational spectroscopy. The molecular orientation of surface functional groups of PES changed significantly when blended with a small amount of Pluornic F127. Pluronic F127 on the blend surface also exhibited different features upon contacting with water. The entanglement of PES chains with Pluronic F127 molecules rendered the blends with long-term surface stability in water in contrast to the situation where a layer of Pluronic F127 adsorbed on the PES surface. Atomic force microscopy (AFM) and quartz crystal microbalance (QCM) measurements were included to determine the relative amount of protein that adsorbed to the blend surfaces. The results showed a decreased protein adsorption amount with increasing Pluronic F127 bulk concentration. The correlations between polymer surface properties and detailed molecular structures obtained by SFG would provide insight into the designing and developing of biomedical polymers and functional membranes with improved fouling-resistant properties.

Fouling resistant membranes in desalination and water recovery

Low molecular weight cut off (MWCO<1000 Da) polyethersulfone nanofiltration membranes and polyamide brackish water thin film composite membranes containing negatively charged and / or neutral hydrophilic functional group on the surface were prepared by surface modification of the membranes by in situ redox polymerization of acrylate monomers. The NF membranes have been used for treatment of dye effluent solution whereas the composite membranes were tested for brackish water desalination without adopting chemical pretreatment protocol to assess their fouling resistance nature. The NF membranes exhibited separations of 68–85% for Na 2SO 4, 19–31% for MgSO 4, 10–26% for NaCl and 2–12% for CaCl 2 with water permeation rates of 10–50 l / m 2 h at the operating pressure of 4 kg / cm 2 for 2000 ppm feed solution. The NF membranes were tested for water recovery from reactive dye effluents containing solutes sizes in the range of 600–1000 Da along with salt solution and were found to reject the dyes >99%. The permeation rate of high flux membranes reduces gradually with time and reaches to about half of the original flux after 3 h of permeation. The original water fluxes have been recovered by simple water washing of the membranes. Surface modified RO composite membranes (flat coupons as well as 4′ modules) have shown good fouling resistant properties for brackish water desalination.

Protein-adsorption-resistance and permeation property of polyethersulfone and soybean phosphatidylcholine blend ultrafiltration membranes

Novel ultrafiltration membranes were prepared by simple blending of polyethersulfone (PES) and soybean phosphatidylcholine (SPC). X-ray photoelectron spectroscopy (XPS) and water contact angle measurements indicated SPC enrichment at the membrane surfaces. The immobilization and arrangement of PC groups at surfaces rendered the membranes more hydrophilic. BSA adsorption amount decreased from 56.2 μg/cm 2 for SPC-free PES membrane to 2.4 μg/cm 2 for PES/SPC blend membrane. The fouling-resistant property of the blend membranes was improved considerably with an increase of SPC content while the pure water permeation flux decreased remarkably. Using PEG/PVP mixture instead of PEG as pore-forming agent increased pure water flux of PES/SPC blend membrane to some extent.

Polymer adsorption on multicomponent surfaces with relevance to membrane fouling

Block copolymer thin films that include low surface energy domains are analyzed as a possible way to overcome the problem of membrane fouling by proteins and other natural organic matter. A model is presented that accounts for both fouling due to chemical interactions between the solute and surface and due to convective deposition. Guidelines for the formation of novel membranes with improved fouling-resistant properties are suggested based on comparison of the relative permeate flux decline due to fouling on different model copolymer membranes. In general, it is observed that copolymer films having small and dispersed polymer blocks that interact unfavorably with the fouling species show an overall decrease in fouling and increase in permeate flux compared with the homopolymer films.

Surface modification of ultrafiltration membranes by preadsorption of a negatively charged polymer: I. Permeation of water soluble polymers and inorganic salt solutions and fouling resistance properties

Polyethersulfone ultrafiltration membranes (MWCO: 9000, 35,000 and 85,000) were surface modified by preadsorption of poly(sodium 4-styrenesulfonate) (PSS) upon the permeation of aqueous solution of the polymer for about 100 min. Membranes with lower MWCO values were modified primarily on the top surface, whereas high MWCO membranes were modified both on the surface and pore walls as well. The IR spectra of surface modified membranes show absorption bands at 1040 cm −1 due to symmetric vibration of SO 3 − group, and at 2925 and 2852 cm −1 corresponding to asymmetric and symmetric stretchings, respectively, of aliphatic (backbone CH 2 and CH) unit present in PSS. Surface modified membranes have shown separations of 28–56% for Na 2SO 4, 11–19% for NaCl and <5% for CaCl 2 with water permeation rates of 35–102 lm h at 2 kg/cm 2 when tested for 500 ppm feed solution. The rejection of Na 2SO 4 decreases in an exponential manner when the concentration of Na 2SO 4 in the feed solution was increased from 500 to 2500 ppm, which is a characteristic of negatively charged membranes. The antifouling nature of unmodified and surface modified membranes were compared by ultrafiltration of aqueous solutions of different molecular weight polyethylene glycols and dextrans. Surface modified membranes have shown better antifouling properties compared to unmodified membranes, as indicated by flux decline with operating time.

Operational experience with a new fouling resistant reverse osmosis membrane

This paper will compare two types of thin-film composite membranes with different chemistries. Both types are produced by a process known as “interfacial polymerization”, but the two have different barrier layer chemistries. One type is manufactured using the chemistry protected by the Cadotte patent and is classified as a polyamide. The other type utilizes a new chemistry that forms a polyamide-urea barrier layer. This new barrier layer has proven superior in critical areas of reverse osmosis operation including rejections of certain dissolved species and its fouling-resistant property. These benefits, along with others, will be explored by reviewing three plants with long histories of fouling problems. Operational data from before and after the introduction of this new membrane will be presented along with interviews conducted with the engineer and/or supervisor of each location. It is this information that will differentiate this new polyamide-urea thin-film composite membrane, not only in chemistry, but, in the field where money and time can be saved.

UF-treatment of soy milk using membrane coated with soybean lecithin.

It was tried to endow the UF-membrane with a fouling-resistant property against protein by forming the protective coating of soybean lecithin on a surface of the membrane of hollow fiber UF-modules. UF-modules treated with soybean lecithin were used twice for the concentration of soy milk; as a result, the performance of treated UF-modules was unchanged during duplicates.

Polymers for Controlled Release of Organotin Toxin

Abstract An extensive investigation of organotin polymers capable of simultaneously providing long-term fouling resistance and useful engineering properties is discussed. New synthetic routes have been developed for organotin epoxy polymers utilizing (i) the crosslinking reaction of diepoxides with the free carboxyl groups present on a base polymer partially esterified with tributyltin oxide (TBTO), (ii) the polymerization of TBT acrylate and TBT methacrylate with vinyl monomers carrying functional groups capable of crosslinking, and (iii) simultaneous vinyl polymerization and epoxide crosslinking reactions. Flexible polymers curing under ambient conditions have also been developed (iv) by first preparing epoxy-terminated prepolymers by reacting TBT esters of w-amino acids with diepoxides, and then crosslinking with diethylenetriamine. Room-temperature-curable organotin polymers developed also include (v) urethanes, (vi) aziridines and (vii) polyesters. Finally, (viii) an ablating polymer is developed by ...