Effects Of Nitrite On The Photodegradation Of 4-Chlorophenol In The Water

Photodegradation is an important process in the transformation of the phenols in environmental water. In recent years, more and more attention were paid to the photodegradation of 4-chlorophenol (4-CP), which is one of the typical phenol contaminants. In the water body containing a great quantity of NO2- or NO3-, the photodegradation of contaminants is likely to be affected by NO2- and NO3- due to their photochemical effects. However, most of investigation was made to the treatment efficiencies in the presence of catalysts and under UV irradiation, which only provides us limited information about their photodegradation in the natural water body due to the the differences between the natural system and experimental one. To data, Few studies were focused on the degradation of 4-CP with existence of NO2- in the natural water body. In the present paper, the following works were carried out.The effects of concentrations of NO2-, pH values on the photodegradation of 4-CP were examined under Xe lamp to simulate sunlight irradiation. The conclusions were drawed as follows:(1) GC-MS was used to characterize the products in the photodegradation of 4-CP. The chromatorgrams and the mass spectrums showed that 1,4-benzoquinone was detected in the 4-CP photodegradation process. The main nitroproduct was 2-nitro-4-chlorophenol (2N4CP). (2) 10 mg/L,20 mg/L, and 40 mg/L of NO2- were added in the reaction systems respectively.The results showed that the degradation rate of 4-CP was the highest at NO2- of 20 mg/L. However, the degradation rate of 4-CP declined at NO2- dosage of 10 mg/L and 40 mg/L. In addition, the production of 2N4CP increased with the increasing concentrations of NO2-. Moreover, the degradation of 4-CP was investigated at different pH, i.e,3.85,6.60 and 8.50, respectively. The results showed that the photodegradation rates decreased with increasing of pH, and the production of 2N4CP displayed a similar tendency. Furthermore, radical trapper test was used in the systems under different pH conditions, in which the photodegradation rates were all significantly weakened.Finally, humic acid and Fe3+ were added into the photodegradation system respectively under simulated sunlight irradiation. The results were as follows, (1) The conclusions were drawed though investigation of 4-CP phtodegradation at different concentrations of humic acid:the photodegradation rate was improved at 5 mg/L humic acid, and the production of 2N4CP also increased with increasing of degradation of 4-CP. However, the photodegradation rate decreased at 15 mg/L humic acid. (2) After 10 mg/L Fe3+ added into the photodegradation system, the photodegradation of 4-CP was inhibited, the corresponding production of 2N4CP dropped.We hope that the results in this paper could provide some useful information to better understand the photodegradation 4-CP in the water with the existence of NO2-.