| Since the droplet size of oil in oily emulsion is usually very small with a magnitude of micrometer, separation of oil from oily wastewater is quite difficulty. The key to the separation of such wastewater lies in the demulsification of oily emulsion. Conventional methods of oily wastewater treatment, which often supplemented by electrolytic and flocculation demulsification process, are restricted due to the high operation cost, or the use of a variety of chemical additives leading to the effluent fail to meet the discharge standards. In recent years, membrane separation technology has attracted a great attention to oil-water emulsion separation. It has advantages of high removing rate, no chemical additives, no phase transition, which is more economical and practical. However, application of the membrane separation technology encounters several problems such as serious membrane fouling and high preparation cost. Therefore, the hydrophilic membrane modification of oil-water separation membranes as an antifouling measure becomes a research hotspot. Because the dynamic membrane (DM) has many advantages, for example, simple preparation, low cost, great flux, strong retention ability, rich material and so on, so dynamic membrane technology has been used as the popular hydrophilic membrane modification technology.Hydrophilic dynamic membranes were prepared on the inner surface of porous tubular carbon support aiming at cross-flow microfiltration of oil-in-water emulsions. Three kinds of hydrophilic inorganic particles, i.e., kaolin, zirconium oxide (ZrO2) and aluminum oxide (Al2O3) were used as coating materials, respectively. Variations of membrane permeation flux with time were examined during coating. Effects of coating material species, average support pore size, preparation pressure, cross-flow velocity, coating solution temperature and cation concentration were investigated. The effects of preparation conditions on flux decrease and the structure of the dynamic membrane were studied by membrane characterization.Secondly, the performances of three kinds of dynamic membrane in oil-in-water emulsion separation were experimental studied. Orthogonal experiments were carried out to study the effects of the operation conditions on oil-in-water emulsions separation, the variance analysis shown that the pressure and the temperature had significant effects on the oily water separation performance. The optimal operation conditions conducted from the orthogonal experiments and single factor experiments were oily emulsion concentration 0.1 g/L, temperature 25℃, separation pressure 0.12MPa, cross-flow velocity 0.85m/s. In addition, the ZrO2 DMs were applied in oil-in-water emulsion separation, the effects of support average pore size and the concentration of the coating solution were experimental studied.Based on the experiment results, the formation mechanism of three kinds of DMs were preliminary investigated, which formed on the support with average pore size of 3.0μm, the results shown that the Kaolin DM and ZrO2 DM accords with cake formation filtration, and the Al2O3 DM accords with intermediate blocking filtration. The effects of support average pore size on the formation mechanism and separation mechanism of ZrO2 DMs were investigated, and the results shown that the formation mechanism ZrO2 DMs depends on the matching relationship between the support average pore size and the particle size. Due to formation of the DMs on the supports, the separation mechanism of the ZrO2 DMs is different from the formation mechanism.
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