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Photocatalytic degradation of the organic compounds enhanced by chemical oxidants

  Water for drinking and domestic purposes must not contain harmful substances. It should be transparent, colorless, odorless, have a pleasant and refreshing taste and cannot contain pathogenic bacteria [1]. One of the basic problems of water treatment is the removal of organic species, especially humic substances (HS) - compounds, which have not as yet been properly chemically defined. HS represent a major fraction of natural organic matter (NOM) in ground and surface waters. Their presence causes growth of microorganisms resulting in undesirable odor and change of color and turbidity of water [2]. NOM occurrence in water, especially that part which cannot be removed by coagulation, determines demand for chlorine in chlorination process. However, toxicological studies indicate that after chlorination carcinogenic byproducts, such as trihalomethanes, can be found. Therefore, the efficient removal of NOM leads to reduction of the required amount of disinfectant, decreases the risk of formation trihalomethanes and also prevents the formation of biofilm [3]. For these reasons there exists a strong demand for new methods for NOM removal. As photocatalysis, is a promising method for removing organic compounds from water, in recent years, TiO2 based photocatalysis of humic acids (HAs) has been extensively investigated [4-7]. In this work, the photocatalytic removal of humic acid (HA) under artificial sun light (ASL) and UV irradiation was examined by monitoring changes in the UV absorbance at 254 nm (UV254). That absorbance is the widely accepted measure for determination of the degradation rate of humic acid and is used as the surrogate parameter for the total organic carbon (TOC) - usually applied to determine degree of HA photodegradation [8]. As the alternative method, the measurements of the chemical oxygen demand (COD) were al[...]

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