Abstract
More and more attention is paid to dissolved organic nitrogen (DON) and some specific categories of amino acids are considered to be the direct precursors of nitrogenous disinfection byproducts (N-DBPs). Histidine was chosen to study the efficiency and mechanism of amino acid in UV/Cu-TiO2system. Moreover, the influences of pH, organics, and inorganic ion on the photocatalytic efficiency were also investigated. The results show that the degradation rate of DON in the UV/Cu-TiO2system was about 50% after 60 min, and it was much lower than that of histidine (72%), which indicated that a part of degraded histidine was oxidized to other N-containing organics. The optimal pH value was 7.0 for the photodegradation of histidine, and the presence of organic compound and inorganic ion would decrease the degradation performance to some extent. After 6 h irradiation, histidine was totally degraded intoNH4+, and in the following 2 h,NH4+was oxidized toNO3-firstly and thenNO3-was reduced to N2and overflowed from water, which should be attributed to the doping of Cu in the TiO2and provided a way to totally degrade the DON from the water.
Highlights
Total dissolved nitrogen (TDN) is presented as dissolved inorganic nitrogen NH4+ species) and (DIN) (the sum of NO3−, dissolved organic nitrogenNO2−, and (DON) in natural waters
Some special categories of amino acids were considered as the main precursor of nitrogenous disinfection byproducts (N-DBPs) according to former studies [12,13,14,15] and some other Dissolved organic nitrogen (DON) matters may change to amino acids during the water treatment
The X-ray diffraction (XRD) patterns show that Cu-TiO2 is in anatase phase, which is the most reactive form of TiO2
Summary
Total dissolved nitrogen (TDN) is presented as dissolved inorganic nitrogen NH4+ species) and (DIN) (the sum of NO3−, dissolved organic nitrogenNO2−, and (DON) in natural waters. External sources of DON arise from sewage and industrial effluents, terrestrial run-off, and atmospheric deposition [4,5,6]. This nitrogen fraction includes a large spectrum of natural compounds like free and hydrolysable amino acids, chlorophyll, and amino sugars and synthetic compounds like pesticides (e.g., atrazine) [7]. As to the dissolved organic matters, amino acids are mainly present as combined amino acids and constitute a small proportion (7.2 ± 4.3%) of the total DON [2].
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