| With the quick development of new membrane material and membrane processing technology, hollow fiber membrane technology has been widely used in the field of water treatment. However, what limited the application of membrane technology was that membrane fouling caused more energy consumption and maintenance cost, and the core issue of application of industrial membrane was membrane ageing caused by membrane bleach. Consequently, the discussion of membrane fouling mechanism and membrane ageing became the hot spot currently. The article would study the fouling mechanism and ageing mechanism from these aspectsThe main studied content of paper contained three parts:(1) The paper analyzed the influence factors of flux of microfiltration membrane, such as initial transmembrane pressure, salt concentration, the length of membrane, temperature. Results are as follows. The open degree of membrane pore became bigger while the increase of initial transmembrane pressure and function time. The higher ion concentration was, the easyer the salt saturation of membrane fiber was. Then the flux became stable more easily. The flux of unit membrane area decreased with the increase of membrane length. The higher temperature was, the force between water molecule weaker was. Then the viscosity became small. Finally, the flux became bigger. Besides, the relationship between flux and temperature, viscosity was linear correlation, respectively.(2) Membrane fouling mechanism of particles has been analyzed by microfiltration of Si O2?Cd S?Fe3O4 nanoparticles solution. Results showed fouling mechanism of little particles concluded the contriction of pores, clogging of pores, caking formation.The fouling process of big particles only contained cake formation. The change of flux during microfiltration of Si O2 nanoparticles was simulated by constructed the relationship between mass of deposition and resistance. The results suggested that at pressure below 0.025 MPa, for the concentration below 0.5 g/L, the scope of value of pressure attenuation coefficient was 0.045 to 0.061, and the value of compressibility of cake was among the range of 0.18 to 0.4, besides the properties of cake was stable. The residual sum of squares was less than two, then the equation could simulate flux change well. Besides, the difference of compressibility of cake was mainly affected by the material of support layer which was composed of glass fiber. The moving of particles in membrane channel was analyzed by the environmental scanning electron microscope. Results showed particles deposited on the membrane surface near the inlet were flushed to the deadend for the turbulent flow in the membrane channel during the initial 10 mins filtration. Then the cake was thicker near the deadend than that near the inlet. The cake was thicker near the inlet than that near the deadend for the laminar flow in membrane channel from 25 th min.(3) Membrane ageing mechanism was developed by analysis of Fourier Transform infrared spectroscopy of PVDF and PES membrane soaked in different Cl O2 concentration solution. Results are as follows. During ageing of PVDF membrane, C-H bond whose frequency was 875 cm-1 was reacted in the solution. During reaction process, the link of molecule was broke and then formed macromolecular free radical. Finally, radicals reacted each other to formed polymer, such as alkene, polyol and so on. However, during the ageing of PES membrane, C-S bond whose frequency was 1174 cm-1 was reacted. During reaction, molecule link was broke and then formed sulfonic acid group. What's more, according to the analysis of field emission scanning electron microscope image, after ageing of membrane the size of membrane pore and porosity of membrane increased, and then the flux increased. |
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