| Summary: | 碩士 === 國立屏東科技大學 === 環境工程與科學系 === 92 === Surface water often contains a variety of natural organic matter (NOM) in dilute solutions. Some carcinogenic substances are produced by the disinfection process of water purification and those by-products have some negative effects on human health. Powdered activated carbon (PAC) was utilized in this study to remove the organic matters such as humic substances form aqueous stream that decreased the fouling degree of the membrane process and reduced the potentially harmful organic contaminants in effluents.
A commercial powdered activated carbon was obtained for the tests of its general properties and binding isotherms. A simulated solution was prepared from the commercial humic acid to study the binding behaviors of humic acid to PAC under several factors and then acquire the optimal operation parameters for the follow-up ultrafiltration (UF) experiments. The hydrophobicity/hydrophilicity fractionized by DAX-8 non-ionic macroporous resins of humic acid on the effects of PAC adsorption and membrane fouling were also investigated. The results demonstrated that the binding isotherms of PAC to humic acid was non-linear under several pH values, and the rejection measured as UV254nm absorbance, TOC (total organic carbon) and COD (chemical oxygen demand) concentration were about 54% (pH=4.0), 52% (pH=7.0) and 92% (pH=7.0), respectively. It was about 59 BV (bed volume) and about 1102 BV to reach respective breakthrough point and exhausted point for the hydrophilic portion fractionized by DAX-8 non-ionic macroporous resins. While the hydrophobic portion of humic acid was almost eluted by 0.1N NaOH at 3-4 BV. The hydrophobic and hydrophilic fraction possessed different fluorescent characteristics in varied pH values that made a shift of wave crest at wavelength of 442nm in the fluorescent emission spectra. In the experiments of PAC enhanced UF system the permeate flux of distilled water was linear with the operating pressure shown the membrane compaction effect was minimal in the range of pressure up to 30 psi for different MWCO. To the evaluation of the removal efficiency of humic acid, the variation in permeate flux of was lower than that of hydrophobic one. The removal of hydrophilic fraction was about 100% either by membranes or PAC while the rejection of hydrophobic fraction was only 80% by PAC enhanced UF process. Generally speaking, PAC can effectively remove the hydrophilic fraction but not hydrophobic one, the major fouling agents of the membrane, and the removal efficiency of hydrophobic fraction can be substantially improved by PAC enhanced UF.
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