| 1. |
- Gekas, Vassilis, et al.
(författare)
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Contact angles of ultrafiltration membranes and their possible correlation to membrane performance
- 1992
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Ingår i: Journal of Membrane Science. - 0376-7388. ; 72:3, s. 293-302
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Tidskriftsartikel (refereegranskat)abstract
- The captive bubble method was used to describe the wetting characteristics of a number of commercial ultrafiltration (UF) membranes. The membranes belonged to one of two homologous (same material, different cut-off) series made by the same manufacturer. One series was made of polysulphone and the other one of cellulose triacetate. The porosimetric characteristics of the membranes have also been measured. The combined data were used to explain the fouling behaviour of the membranes upon ultrafiltration of solutions containing dextran, whey protein concentrate and silicate sols. The cellulose triacetate series is characterized by lower receding contact angle and smaller contact angle hysteresis and shows better flux behaviour (permeate flux during UF and pure water flux recovery at the end of UF) than the polysulphone series. Within the same series the mean permeability pore size shows a better correlation with membrane flux behaviour than with contact angle hysteresis.
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| 2. |
- Jönsson, Ann-Sofi
(författare)
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Influence of shear rate on the flux during ultrafiltration of colloidal substances
- 1993
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Ingår i: Journal of Membrane Science. - 0376-7388. ; 79:1, s. 93-99
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Tidskriftsartikel (refereegranskat)abstract
- The shear rate at the surface of a membrane has a distinct influence on the membrane flux in systems containing colloidal substances. If the shear rate is decreased, flux decreases since the thickness of the boundary layer of retained solutes at the membrane surface then increases. When low molecular solutes are used, flux increases again when the shear rate is increased. However, if large solutes are used, polymeric and colloidal substances, for example, it sometimes happens that the flux cannot be increased to its original value again by increasing the shear rate: the flux decline is regarded as irreversible. Experiments, performed in a new type of turbulence-promoting module, which illustrate the influence of shear rate on flux when treating solutions containing colloidal substances, are presented in this paper. It is also shown that a flux decrease which can not be restored by increasing the shear rate, may be completely restored by a temporary interruption of the permeate flow.
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| 3. |
- Jönsson, Ann-Sofi, et al.
(författare)
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The influence of nonionic surfactants on hydrophobic and hydrophilic ultrafiltration membranes
- 1991
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Ingår i: Journal of Membrane Science. - 0376-7388. ; 56:1, s. 49-76
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Tidskriftsartikel (refereegranskat)abstract
- The influence of different types of surfactants on ultrafiltration membranes has been investigated. A basic approach to membrane-surfactant interactions is also presented. A nonionic (Triton X-100), two anionic (potassium oleate and sodium dodecylbenzenesulphonate) and a cationic (hexadecyltrimethylammonium bromide) surfactant were investigated. The effects on commercial membranes of polysulphone, poly(vinylidene fluoride) and cellulose acetate were studied. The flux reductions of the hydrophobic membranes were found to be much more pronounced than the flux variations of the hydrophilic membranes. Both the material and the molecular weight cut-off were found to influence the performance of the hydrophobic membranes. A drastic influence of hydrophobic impurities was demonstrated. The retention of the nonionic surfactant was low at concentrations below the critical micelle concentration. The retention of the ionic surfactants was quite high, even at low concentrations.
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| 4. |
- Lindau, J, et al.
(författare)
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Cleaning of ultrafiltration membranes after treatment of oily waste water
- 1994
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Ingår i: Journal of Membrane Science. - 0376-7388. ; 87:1-2, s. 71-78
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Tidskriftsartikel (refereegranskat)abstract
- The influences of different types of cleaning agents on a polysulphone ultrafiltration (UF) membrane which had been used to treat oily waste water were investigated. The cleaning experiments were performed with samples of polysulphone membranes removed from a commercial plant in which oily waste water is treated. Five different cleaning agents were used and their influences on the fluxes were investigated. The influence on the flux when cleaning with the different cleaning agents in succession was also studied. Deposits on the membrane surface, before and after cleaning, were analysed using different methods. Most of the analyses were carried out using scanning electron microscopy (SEM) in combination with energy dispersive X-ray (EDX) combined with a micro-analysis system permitting quantitative determination of elements. Some analyses were also performed using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS).
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