Effects Of Heavy Metal Complexation On Photodegradation Of Quinolone Antibiotics

Because of their wide antimicrobial spectrum, widely distributed in the body, high tissue concentrations, strong activity, low resistance, fluoroquinolone antibiotics (FQs) are widely used in aquaculture, animal husbandry and human prescription drugs, and they have positive impact on the treatment of human and animal diseases. However, FQs are often poorly absorbed, and excreted in their pharmacologically active forms and metabolites when they are applied to animals or humans. FQs can make human central nervous system toxicity, kidney toxicity, hematologic toxicity and phototoxicity, etc., and can induce the emergence of bacterial resistance, which can cause a certain impact on the human health and the environment. FQs are not always stable in the environment, and they are generally degraded via different ways in aqueous solution and photodegradation is a main method among these degradation ways.. It is of great significance for researching the form and migration of FQs under different environmental factors, especially in combination with the heavy metals in aqueous solution. Therefore, ciprofloxacin (CIP), ofloxacin (OFL) and norfloxacin (NOR) were selected as the research object, and the main purpose was to research the effects of Cd(NO3)2, Pb(NO3)2, CdCh and PbCl2 on FQs photodegradation of under UV and natural light. The details research contents and the main findings of this paper are listed as follows:(1) By molar ratio method, the absorbance of NOR, OFL, CIP solution in combination with different proportions of Cd or Pb were detected by using UV absorbance spectrophotometer. The complexing ratio of Cd, Pb with FQs was varied between 1:2 and 1:3 from the experimental results.(2) These three targeted FQs were hardly degraded in the dark, but had rapid photodegradation efficiency under the UV. Photodegradation rate reduced with the increase of the initial FQs concentrations, which can be explained that unit concentration of targeted FQs contact less amount of photons. Both Cd(NO3)2 and Pb(NO3)2 can accelerate photodegradation of CIP. The promoting effect of them was gradually reduced with the increasing of molar ratio, and the concentration of nitrates were reduced at the same time. CdCl2 and PbCl2 suppressed the photodegradation of CIP. The inhibiting effect of them was gradually increased with the increasing of molar ratio, and the concentration of chloride was reduced. Cd(NO3)2 and Pb(NO3)2 suppressed the photodegradation of OFL; Furthermore, CdCl2 and PbCl2 suppressed the photodegradation of OFL. Both Cd(NO3)2 and Pb(NO3)2 can accelerate photodegradation of NOR; in high and low concentration of NOR, CdCl2 suppressed its photodegradation; But in the middle concentration of NOR, CdCl2 accelerated its photodegradation, and PbCl2 suppressed its photodegradation.(3) Under real natural light, the photodegradation of NOR and the effects of nitrate and chlorate on the NOR photodegradation were researched. The experiment results shown that Cd(NO3)2 and Pb(NO3)2 can accelerate the photodegradation of NOR, and also suppress its photodegradation; CdCl2 and PbCl2 accelerated the photodegradation of NOR. When the molar ratio was increased, the influence of nitrate and chloride on NOR photodegradation was so complicated that a definite changing trend cannot be given for its photodegradation.