Synthesis Of Porphyrin Modified Bismuth Oxychloride Composites With Enhanced Photocatalytic Activities

The wastewater pollution caused by antibiotics has become one of the most difficult problems in water pollution treatment.The key to the treatment of antibiotic contaminants by photocatalytic technology is to construct green and efficient photocatalysts with visible light response and high separation rate of photogenerated carriers.In this paper,inorganic semiconductor bismuth oxychloride（BiOCl）was used as the matrix photocatalytic material,and it was further modified by porphyrin or metalloporphyrin compounds with large ring conjugated structure.This paper revealed the effects of the introduction of porphyrin on the visible light utilization rate and the improvement of the separation rate of photogenerated electron-holes.In addition,the catalytic mechanism of the prepared composite photocatalysts for the efficient removal of antibiotic pollutants was also investigated.The main research contents are as follows:（1）Defect-rich BiOCl was prepared by solvothermal method assisted by ethylene glycol（EG）,then meso-tetraphenyl porphyrin（TPP）modified BiOCl composite photocatalyst（TPP/defect-rich BiOCl）was constructed by solvothermal method.The results of characterization analysis confirmed that the composite photocatalyst presented flake structure.The influences of defects formation and TPP introduction on the performance of photocatalytic degradation of antibiotics were also investigated.The experimental results showed that the formation of defects on the surface of BiOCl reduced the migration distance of photogenerated carriers and improved the photocatalytic activity of the composite materials.Meanwhile,the introduction of large ring TPP further improved the catalytic performance of the photocatalyst.2 wt%TPP/defect-rich BiOCl showed the best photocatalytic performance,and the rate constant of tetracycline degradation(7.78×10^-3min^-1)was 4.37 times that of BiOCl(1.78×10^-3 min^-1)and 1.6 times that of defect-rich BiOCl(4.82×10^-3 min^-1).Based on the results of photoelectric performance analysis,free radical capture experiment and electron spin-resonance（ESR）test,it was concluded that the improved photocatalytic degradation performance of TPP/defect-rich BiOCl was mainly due to the enhanced utilization of solar energy and the accelerated separation and transport of photogenerated charge carriers between interfaces.Ultimately,a probable reaction mechanism was proposed.（2）Meso-tetra（4-carboxyphenyl）porphine（TCPP）modified 3D spherical BiOCl composite photocatalyst（TCPP/BiOCl）was prepared by one-step hydrothermal method assisted by ionic liquid 1-hexadecyl-3-methylimidazolium chloride([C₁₆mim]Cl).The results of SEM and TEM showed that TCPP successfully loaded on the surface of BiOCl flower composed of 2D nanosheets,and each element was uniformly distributed on the BiOCl flower.The performance of TCPP/BiOCl photocatalytic degradation of antibiotics and the influence of the amount of TCPP on the activity improvement were explored.The results showed that 1 wt%TCPP/BiOCl composite exhibited the best catalytic performance,and the degradation rate constant of TC(10.66×10^-3 min^-1)was 1.96 times that of BiOCl(5.45×10^-3min^-1).The results of optical properties,photochemical properties,free radical capture and ESR analysis revealed that the enhanced photocatalytic activity of TCPP/BiOCl composite photocatalyst was mainly due to the enhancement of its visible light absorption capacity,and the improvement of the separation rate of photogenerated electron and hole pairs.Finally,a possible photocatalytic mechanism was illustrated.（3）The[C₁₆mim]Cl assisted solvothermal method was used to prepare flower spherical BiOCl matrix material.Then,the Cu TCPP/BiOCl composite photocatalyst modified by Cu（II）meso-tetra（4-carboxyphenyl）porphine（Cu TCPP）was prepared by stirring at room temperature.The results of SEM and TEM confirmed that the rod shaped Cu TCPP was firstly successfully loaded on the BiOCl spheres assembled by2D plates and the elements were uniformly distributed.The photocatalytic activity of Cu TCPP/BiOCl composites with different Cu TCPP content ratios was investigated.The results showed that the best photocatalytic activity was 0.5 wt%Cu TCPP/BiOCl.The rate constant of TC degradation(13.37×10^-3min^-1)was 2.84 times that of BiOCl monomer(4.30×10^-3 min^-1).Based on the optical properties,photoelectric properties,free radical capture and ESR test results,it was concluded that the introduction of Cu TCPP could broaden the range of visible light absorption,and promote the separation and migration of photogenerated carriers.Therefore,the photocatalytic degradation performance of Cu TCPP/BiOCl was better than that of BiOCl monomer.Meanwhile,the photocatalytic reaction mechanism was described.