Study On Characteristics Of Photocatalytic Degradation Of Oxytetracycline

With the mass production and application, antibiotics have caused pollution in theaquatic environment, and it also has become a research hotspot nowadays. Tetracyclines,utilized in medication and livestock breeding in large quantity, is one of the most widelyused antibiotics. Due to the poor biodegradability, antibiotics are difficult to be removedcompletely through conventional water treatment technologies, whilst photocatalyticoxidation, a new developed water treatment technology, is of good application prospects indegrading these compounds.In this thesis, with simulated sunlight as light source and nano-TiO2as catalyst, factorsinfluencing the reaction of photocatalytic degradation of oxytetracycline were investigatedunder varying conditions, oxytetracycline samples of the original and after degradation wereanalyzed by liquid chromatography-mass spectrometry （LC-MS）. Results of the researchindicated that: Effects of pH on the photocatalytic reaction were significant, and with the riseof solution pH, removal rate of oxytetracycline was remarkably increased. Effects of catalystdosage on the reaction were relatively considerable, and with the increase of nano-TiO2dosage,removal rate was gradually increased. The photocatalytic reaction of oxytetracycline followedfirst-order kinetics, and with the increase of initial concentration of oxytetracycline, thephotocatalytic reaction rate constant was decreased. Effects of humid acid （HA） and Ca²⁺onthe reaction were similar, and amongst the concentration range in this research, reaction waspromoted with HA and Ca²⁺in low concentration (HA≤1mg/L, Ca²⁺≤0.1mmol/L) whilstinhibited in high concentration (HA≥2mg/L, Ca²⁺≥0.2mmol/L). Reaction was bothpromoted with the presence of NO₃-（0-1.0mmol/L） and Fe³⁺（0-10μmol/L）, and amongst thestudied concentration range, the role of promotion was enhanced with the increase ofconcentration. According to the analysis of LC-MS, three kinds of main products ofphotocatalytic degradation were detected. Moreover, on the basis of these results two probabledegradation pathways were speculated.