Studies On Photochemical Degradation Of Sulfamethazine In Water

SAs are emerging pollutants that have high detection rate in the aqueous environment, and it’s of important significance to research their environmental behaviors as well as effects of eco-toxicity. Sulfamethazine is a typical sort of sulfonamides, short for SM₂. The paper aimed at SM₂for the key of researches, builded detecting requirements from high performance liquid chromatography （HPLC） and observed the photolysis kinetics of SM₂under different light sources, influencing factors and mechanisms. The main results were summarized as following:（1）The photochemical degradation of SM₂in water followed the first order reaction The rates of photolysis were of significant divergence:UV＞HPML＞XL＞SL,and its photolysis half-lives under HPML﹑UV﹑XLand SL were82.5、45.3、1155、3465min respectively.（2）In the experimental concentration range and the same conditions, the photolytic rates of SM₂speeded up with dosage increase.The photolytic rates of SM₂were negatively correlated with its initial concentrations.（3）In the buffer solutions with different pH, the rates of photolysis were remarkably different: pH9＞pH2＞pH7＞pH3＞pH5. when the time of light was30min, th photolytic rates of pH9was72.77％While60min, the photolytic rates was up to92.78％.when30min, th photolytic rates of pH2and pH7were followed by50.34％and46.33％respectively th photolytic rates of pH3and pH5were slowest by32.11％and28.92％respectively.The photolysis of SM₂was much easier in zwitterionic forms than in molecular form in solution.（4）Bicarbonate and nitrate could speed up the photolysis of SM₂.In the experimental concentration range, the effect of bicarbonate became strong with the dosage increase the photosensitive efficiency of nitrate increased when the concentration was added up to1mg/L and then with the further increasing of adding concentration to range from1mg/L to5mg/L, the effect became weak When the concentration was added up to5mg/L, the effect tended to stability The nitrite showed great quenching effect on its photolysis. The photosensitive efficiency of nitrite increased with the dosage increase, when adding concentration was less than2mg/L and then with the further increasing of adding concentration of nitrite, the effect became steady,.（5） Under two different light sources, the effects of Cl-and Br-belonging to halogen ions on the photolysis of SM₂were dual. Under UV light, they showed quenching effects The quenching efficiency of Cl-increased with the dosage increase,when adding coocentration was less than1mg/L.when the concentration of Cl-ranged from1mg/L to10mg/L, the effect became weak.When the concentration of Cl-was added up to10mg/L, the effects tend to stability the quenching efficiency of Br-increased with the dosage increase, when the concentration of Br-was less than10mg/L, and then decreased with the further increasing of adding concentration of Br-. On the contrary, they accelerated the photochemical degradation of SM₂under xenon. When the concentration of Cl-was added up to0.2﹑1﹑5﹑10﹑50mg/L, the photolytic rates of SM₂were5﹑4﹑3.5﹑7﹑6times of balnk comparison respectively. When the concentration of Br-was the same as Cl-, the photolytic rates of SM₂were4﹑8﹑11.5﹑19.5﹑131.5times of balnk comparison respectively.However, different from Cl-and Br-, I-promoted the progress of photolysis of SM₂under different light sources, and its photosensitive effects were exceedingly remarkable. And thus, this paper went deep into the mechanism of I-affecting the photolysis of SM₂, and it was proved that I-accelerated the photolysis of SM₂by its being transformd into other new matter which had a character of catalyzation in the process of light.