Preparation Of Co-g-C₃N₄/La-TiO₂ And Its Visible Light Catalytic Degradation Of Tetracycline And Ciprofloxacin In Wastewater

Antibiotic wastewater is characterized by high concentration of organic matter,difficult degradation and high biological toxicity,which widely exists in water body and brings great harm to human beings,animals,plants and even the whole ecosystem.The traditional biological method is difficult to treat antibiotic wastewater,and it will cause some disturbance to the traditional biological treatment.At present,there are many methods for the treatment of antibiotic wastewater.As one of the advanced oxidation methods,photocatalytic oxidation has become a promising method for the treatment of antibiotic wastewater because of its simple operation,environmental protection and no pollution.In this paper,we first selected g-c₃n₄and Ti O₂with excellent photocatalytic effect,and combined them to enhance the photocatalytic performance.We carried out a series of studies on the removal of tetracycline and ciprofloxacin.（1）Co doped g-C₃N₄was prepared by thermal polymerization with urea and melamine as precursors.La doped Ti O₂with different molar ratios were prepared by sol-gel method.Co-g-C₃N₄and La-Ti O₂with good catalytic effect were screened out by using tetracycline（TC）as target pollutant,and the composites were prepared for subsequent experiments.（2）Co-g-C₃N₄/La-Ti O₂with excellent photocatalytic performance was selected by compounding Co-g-C₃N₄and La-Ti O₂in the ratio of 1:10,2:10,and 3:10,and taking TC as the target pollutant.The experimental results showed that Co-g-C₃N₄/La-Ti O₂with the ratio of 2:10 had the best catalytic effect,and the subsequent experimental analysis of this sample was carried out.（3）The as prepared Co-g-C₃N₄/La-Ti O₂was characterized by SEM,XRD,XPS,UV Vis and PL.it can be clearly seen from SEM that the granular structure of La-Ti O₂is uniformly dispersed in the folds of Co-g-C₃N₄.In XRD,the characteristic peak of Co-g-C₃N₄/La-Ti O₂not only contains the characteristic peak of anatase Ti O₂,but also contains the characteristic peak of Co-g-C₃N₄at 2θ=27.5°.XPS results show that Co and La have been successfully doped into Co-g-C₃N₄/La-Ti O₂samples.UV-Vis showed that Co-g-C₃N₄/La-Ti O₂successfully broadened the absorption range of light.It can be seen from pl that the fluorescence intensity of Co-g-C₃N₄/La-Ti O₂is relatively low,which proves that the photogenerated electron recombination rate of Co-g-C₃N₄/La-Ti O₂is relatively low.（4）The optimal conditions and influencing factors of photocatalytic degradation of tetracycline and ciprofloxacin were studied,including the effects of photocatalyst dosage,p H,initial concentration and anions.The results showed that the optimal amount of catalyst was 1g/L,and the optimal p H for degradation of TC and CIP was7.Among the anions,NO₃^-had little effect on the reaction,while Cl^-,SO₄^2-and HCO₃^-showed different degrees of inhibition on the photocatalytic reaction.（5）The photocatalytic mechanism and reusability of Co-g-C₃N₄/La-Ti O₂were studied.The experimental results show that hole（h⁺）,hydroxyl radical（·OH）and superoxide radical（·O^-₂）play a certain role in the process of photocatalysis,and the contribution degree is:·OH>h⁺>·O^-₂,Co-g-C₃N₄/La-Ti O₂still has high photocatalytic activity after being reused for 4 times.