Construction Of Zn-based Composites And Its Degradation Of Tetracycline Hydrochloride In Water

In this paper,from the perspective of improving the performance of photocatalytic materials,a series of Zn-based composite photocatalytic materials were synthesized by roasting,compounding and doping to improve their degradation efficiency of tetracycline hydrochloride,and the degradation mechanism was discussed by means of electrochemical impedance,free radical capture,band gap structure analysis and other experimental means.The result provides some theoretical support for the rational design and preparation of efficient photocatalytic materials for antibiotic degradation.The specific research results are as follows:(1)ZnO/H4Nb6O17 nanotube composite was synthesized by hydrothermal selfassembly method,and the photocatalytic degradation of tetracycline hydrochloride(40 mg·L-1,100 mL)was carried out under visible light.The experimental results show that the removal rate of tetracycline hydrochloride by 30 mg ZnO/H4Nb6O17 nanotube composite is 68.35%,while the removal rates of monomer ZnO and H4Nb6O17 nanotube are only 48.06%and 11.02%respectively.By characterizing the electrochemical impedance of monomer catalyst and composite catalyst,it can be seen that the composite catalyst has higher photogenerated carrier separation efficiency,and superoxide radical(·O2-)and hole(h+)are the main active species for the degradation of tetracycline hydrochloride by ZnO/H4Nb6O17 nanotube composite.The study on the structure-activity relationship between the microstructure and catalytic properties of the composite catalyst shows that the excellent photodegradation performance of the composite catalyst is attributed to its strong light capture ability,large specific surface area and efficient photogenerated electron and hole separation and transfer efficiency.(2)Zn-based bimetallic hydroxides composed of different layers were synthesized by hydrothermal method,which were ZnTi,ZnCr and ZnCe layered double hydroxide respectively.Taking them as precursors and calcined at different temperatures,a series of Zn-based bimetallic oxides were obtained,which were ZnTi,ZnCr and ZnCe layered double oxide.These catalysts were used(30 mg)applied to tetracycline hydrochloride(40 mg·L-1,100 mL)Compared with the precursor,the removal rate of tetracycline hydrochloride by calcined products is significantly improved.The removal rates of tetracycline hydrochloride by ZnTi layered double oxide calcination at 300?,ZnCr layered double oxide calcination at 600? and ZnCe layered double oxide calcination at 700? are 86.81%,82.59%and 68.98%,respectively.The improvement of tetracycline hydrochloride removal rate is mainly due to the formation of metal oxides produced by calcination while improving the spectral response range of calcined products to promote the separation of photogenerated electrons and holes,so as to improve the photodegradation efficiency of zinc matrix composites for tetracycline hydrochloride.(3)Cadmium sulfide and ZnCr layered double hydroxide composites with different ratios were synthesized by hydrothermal method,and they were applied to the photocatalytic degradation of tetracycline hydrochloride.The catalyst with cadmium sulfide loading of 5%showed the best removal effect of tetracycline hydrochloride under visible light irradiation.Within 120 min,the removal rate of tetracycline hydrochloride was 84.90%,and the removal rate of ZnCr layered double hydroxide was 59.04%.The study on the structure-activity relationship between the microstructure and photocatalytic properties of the composites shows that a Z-scheme heterostructure is formed between cadmium sulfide and hydrotalcite.This structure can not only improve the redox potential of the composites,but also promote the separation of photogenerated carriers,so as to improve the photocatalytic properties of the composites.Through valence band analysis and free radical capture experiment,the photocatalytic degradation mechanism of cadmium sulfide and ZnCr layered double hydroxide composites for tetracycline hydrochloride were obtained.(4)Based on the basic structural characteristics of ZnCr layered double hydroxide,a series of rare earth metal ion La3+ doped zinc chromium hydrotalcite photocatalysts were synthesized by one-step hydrothermal method,and they were applied to the visible light photocatalytic degradation experiment of tetracycline hydrochloride.The experimental results show that the catalyst with 10%La3+doping shows the best photocatalytic degradation performance.In the reaction time of 120 min,the removal rate of tetracycline hydrochloride was 87.16%,which is significantly higher than that of ZnCr layered double hydroxide.The doping of La3+ does not cause obvious changes in the structure and morphology of ZnCr layered double hydroxide,but it enables ZnCr layered double hydroxide to obtain high photogenerated carrier separation efficiency and surface charge injection efficiency,and La3+ plays the role of hole receiver in the whole system,making it easier for laminar charges to migrate and inhibiting the recombination of photogenerated carriers,So as to improve the photocatalytic degradation performance of ZnCr layered double hydroxide for tetracycline hydrochloride.Figures 66 Tables 10 References 157...