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Surface modification by physical adsorption of a series of non-ionic surfactants including Tween 20, Tween 40, Tween 60, Tween 80 and Tween 85, was accomplished on polypropylene microporous hollow fiber and flat membranes. The adsorption curve of the membrane surface was analyzed by weight measurements and the typical results showed a two-platform character similarly. Differences in the degree and curve shape of adsorption resulting from such factors as concentration, temperature, as well as water cleaning time were observed for Tween 85 among other Tweens. Attenuated total reflection — Fourier transform infrared spectroscopy analysis and field emission scanning electron microscopy observation showed that the adsorption of Tween on polypropylene microporous membrane (PPMM) is effective and occurs mainly in the pores of PPMMs at low adsorption amount, and on the membrane surface also at high adsorption value. [ABSTRACT FROM AUTHOR]

Abstract: To improve the antifouling property of polypropylene hollow fiber microporous membranes (PPHFMMs) in a membrane-bioreactor (MBR) for wastewater treatment, the PPHFMMs were subjected to surface modification by CO2 plasma treatment. Structural and morphological changes on the membrane surface were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Water contact angle, which reflects the hydrophilicity of the membrane surface, was measured by the sessile drop method. Results of XPS clearly indicated that the plasma treatment introduced oxygen containing polar groups on the membrane surface. The static water contact angle of the modified membrane reduced obviously at first and then kept almost constant with the increase of CO2 plasma treatment time. To assess the relation between the plasma treatment and the membrane fouling in a MBR, filtration for activated sludge was carried out using synthetic wastewater. The PPHFMMs after CO2 plasma treatment showed better flux recovery after cleaning than that of the unmodified membrane. Fouling index (FI) for the CO2 plasma treated PPHFMMs was lower than that of the unmodified PPHFMM. [Copyright &y& Elsevier]