Photochemical Behavior Of Tetracyclines In Aquatic System

In recent years, with the rapid development of the pharmaceutical industry, a significant increase in the use of antibiotics, resulting in the frequently dedetection of many antibiotics in the environmental, such as soil, surface water, groundwater, river sediment and et.al, which make people give widely attention to the environment effects and hazards of the the residues of antibiotics. The photodegradation is one of the most important transformation behavior in the aquatic.This paper investigated tetracycline,one of the most important antibiotics,which were detected frequently in aquatic system,analyzed the photochemical transformation law under simulated solar light and natural light,and discussed the degradation model in solar light,The main objectives and results of this work were presented as follows:1.This work discuss the TC in the degradation under simulated sunlight, through the pH, initial concentration, ionic strength and other factors investigated, indicating that the tetracycline (TC) of light degradation was significantly accelerated with the increase of solution pH, and TC indoor light Degradation is a first order kinetic reaction. Ionic strength to some extent affects the degradation of tetracycline.2. At the pH = 7.3, the research gains a water of the common components, such as humus (humic acid, fulvic acid ), photosensitive ion (NO₃^-, Fe3 +), metal ions ( K +, Mn2 +, Zn2 +, Ca²⁺, Mg²⁺) to the impact of tetracycline (TC), chlortetracycline (CTC) in the degradation and a great attention paid to Ca²⁺, Mg²⁺ influenceon the photodegradation of TCs mechanism. The results show that NO₃^- and Fe³⁺can speed up the tetracycline, chlortetracycline photodegradation rate, Humic acid (FA) and fulvic acid (HA) inhibited the photodegradation of tetracycline. Metal ions on photodegradation of tetracycline different, such as K + on the photodegradation of TC had no effect, but Mn2 +, Zn2 + are inhibited.3. The relationship between different pH, different concentrations of Ca²⁺, Mg²⁺ and tetracycline (TC), chlortetracycline (CTC) Degradation show that pH of Ca²⁺, Mg²⁺solution have some influence on rate of TC, CTC photodegradation. On the situation of pH = 7.3, Ca²⁺ can accelerate the photodegradation rate of TC, while Mg2 + inhibites the light degradation. However ,when at pH = 9.0, Ca²⁺ and Mg²⁺ will inhibit the photodegradation rate of TC, and with the metal ion concentration, inhibition will increase. In a word,Ca²⁺ and Mg²⁺ on the degradation of TC related to the formation of complexes with the TC, CTC. By singlet oxygen (¹O₂) in the detection and determination of reaction rate, indicating that during the photodegradation TC and CTC produced ¹O₂, which its oxidation of TC can influenced by Ca²⁺, Mg²⁺.4. In the outdoor sunlight, the study of the TC in the Dongjiang and deionized water degradation have established photodegradation half-life model . Compared with the measured value,the results show that the degradation of TC in the Dongjiang rate faster than the deionized water, and the degradation half-life of TC in Dongjiang water is between 6 min and 40 min.There are some differences between the model of the outdoor light and the experimental data, which may be affected by the substances in Dongjiang.