Kinetic Studies of Visible Light Photodegradation of Sulfanilamide in Organic Effluents

• Main Authors: Shen-Jhan Hong, 洪申展
• Other Authors: Chiu-Yun Chen
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/50030923599328316348

碩士 === 國立高雄海洋科技大學 === 海洋環境工程研究所 === 103 === Sulfonamides are a kind of antibiotics widely used around the world. However, due to their own property sulfonamides can be easily flowed into sewage treatment plants through drains if used improperly or not completely metabolized in digestive system of humans and animals. Besides, removal rate of some sulfonamides in secondary sewage treatment plants is poor, so they will flow into natural environments such as river, groundwater and lake water along with effluent runoff, and when excessive sulfonamides are released into environment, environmental microbes will generate drug resistance and thereby bring risk to environment. This study first preliminarily used visible light to irradiate school sewage plant effluents containing sulfonamides, and then assessed the feasibility of using visible light to degrade sulfonamides; next, used pure water, school sewage plant effluent, and semi-mariculture effluent matrices containing different DOM, NO3-, NO2-, NH3, pH and turbidity to conduct the exploration of degradation chemical kinetic model, half-life, degradation pathway and intermediate products of sulfonamides in each matrix. Sulfonamides in each matrix were irradiated to conduct degradation reaction, and chemical kinetic model of each matrix was determined by reaction rate constant. The zero-order to second-order reaction rate constants of pure water were very small, indicating no degradation trend of sulfonamides in pure water; school ewage plant effluent was between zero-order and first-order reactions, reaction rate constant of zero-order reaction was 7.43~14.80 g·L-1·day-1, and of first-order reaction was 0.0789~0.188 day-1; while semi-mariculture effluent was in line with zero-order reaction, its reaction rate constant of zero order reaction was 0.283~2.75 g·L-1·day-1. As for photodegradation half-life of sulfonamides in each matrix, it was 1.02E+2~2.25E+4 days, 3.69~8.78 days, 29.7~444 days in pure water, school sewage plant effluent, semi-mariculture effluent respectively, indicating that half-life of sulfonamides varies very much with different matrices. No DOM and nutrients existed in the pure water, so in visible light waveband the sulfonamides in the pure water did not conduct indirect photodegradation. In the school sewage plant effluent, the main degradation pathway of sulfonamides was indirect photodegradation generated by DOM (photodegradation rate accounted for more than 95%), in the matrix the light energy absorbed by ground state DOM increased to 3DOM*, and the 3DOM* energy was transferred to sulfonamides, making sulfonamides conduct indirect photodegradation. While the pH of the semi-mariculture effluent was alkaline, so sulfonamides showed a steady state, resulting in slowdown indirect photodegradation; and because this effluent had not been treated by a sewage plant, so unique microbes existed in the matrix itself, making microbial degradation rate increase to 11~65%. This study added sulfonamides into the school sewage plant effluent to conduct photodegradation, the reaction rate was slower when acetonitrile content was more, so it was assumed that acetonitrile plays a quencher role in photochemical system. When acetonitrile is uniformly distributed in matrix with molecular state, it will collide and conduct energy transfer with 3DOM* having almost same energy, quenching 3DOM* transfers energy to sulfonamides, causing slowdown sulfonamide photodegradation reaction rate, and the proportion of acetonitrile should be less than 0.0412% in order to not cause interference to degradation reaction of sulfonamides. The qualitative results of intermediate products of the school sewage plant effluent and the semi-mariculture effluent were different, representing different matrices will affect the generation of intermediate products, and the qualitative results showed that the detected frequency was highest for p-anilinesulfonamide and p-aminobenzenesulfonic acid.