| Dimethyl phthalate?DMP?is a widely used synthetic organic compound in everyday life and is commonly used as a plasticizer in industrial pro duction.It is biotoxic,can be enriched along the food chain and is hazardous to human health.However,conventional water treatment processes are not effective in removing DMP from water.In the present study,carbon nitride?g-C3N4?was used as the raw material.The g-C3N4 was processed templating and protonation to obtain the templated and protonated carbon nitride?zmpg-C3N4?,followed by magnetized and compounded with bismuth bromide oxide?Bi OBr?and polythiophene?PTh?.The magnetic zmpg-C3N4/Bi OBr/PTh composite was obtained and applied to degrade DMP in water under visible light.The preparation process conditions of magnetic zmpg-C3N4/Bi OBr/PTh was optimized.The composite was characterized to analysize its microstructure,crystal phase,light absorption capacity and photoelectric properties.The effect of different photocatalytic reaction conditions on the degradation of DMP was studied.A reaction kinetics study was conducted,and a cyclic stability study was performed on the catalyst.The mechanism of DMP photocatalytic degradation was analysized and the possible degradation path of DMP was explore d.The performance of photocatalytic degradation of DMP by g-C3N4 compounded with various materials was investigated.The results showed that the effect of DMP degradation by magnetic protonated and templated g-C3N4compounded with Bi OBr and PTh was better.The optimization of preparation process of magnetic zmpg-C3N4/Bi OBr/PTh composite by orthogonal experiments revealed that the urea/Si O 2mass ratio was the main factor affecting the photocatalytic performance of the composite,while the zmpg-C3N4 acidification time had the least influence.The best preparation process conditions for magnetic zmpg-C3N4/Bi OBr/PTh are that,the mass ratio of magnetic zmpg-C3N4/Bi OBr and urea/Si O2 is 1:5 and 3:1,respectively,the zmpg-C3N4acidification time is 6 h,the hydrothermal synthesis temperature of composite is 140?.The characterizations were carried out by field emission scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,X-ray energy spectrum?EDS?,X-ray diffraction?XRD?,Fourier infrared spectroscopy?FT-TR?,X-ray photoelectron spectroscopy?XPS?,specific surface?BET?and aperture,ultraviolet-visible diffuse reflection?UV-vis DRS?,photoluminescence spectroscopy?PL?,electrochemical impedance?EIS?and magnetic determination.The results revealed that magnetic zmpg-C3N4,Bi OBr and PTh were successfully compounded to form heterogeneous junction.The magnetic zmpg-C3N4/Bi OBr/PTh has a saturated magnetization strength value of 11.31emu/g with good magnetism and the magnetic substance is iron oxide.UV-visible diffuse reflection tests showed that the absorption band edge of the magnetic zmpg-C3N4/Bi OBr/PTh was redshifted and the forbidden band width narrowed compared to g-C3N4.Fluorescence spectroscopy analysis yielded excitation peak intensities of magnetic zmpg-C3N4/Bi OBr/PTh that were much lower than those of g-C3N4 and zmpg-C3N4,indicating a significantly higher photogenic electron-hole mobility of magnetic zmpg-C3N4/Bi OBr/PTh.The electrochemical impedance mapping measure demonstrated the photobiogenic carrier transmission impedance values in the order of magnitude g-C3N4?zmpg-C3N4?magnetic zmpg-C3N4/Bi OBr?magnetic zmpg-C3N4/Bi OBr/PTh,confirming that magnetic zmpg-C3N4/Bi OBr/PTh composites have faster interfacial electron transfer efficiency.The effects of different p H,catalyst dosage,DMP initial concentration,reaction time on DMP photocatalytic degradation were investigated.The results showed that the photodegradation rate of DMP gradually increased with increasing p H,the highest rate of DMP degradation was observed at p H 7.36,while the rate of DMP degradation decreased when the p H value continued to increase.As the DMP concentration changed from5mg/L to 20mg/L,the degradation rate increased with increasing DMP concentration.However,when the DMP concentration continued to increase to 30mg/L,the DMP degradation rate showed a decreasing trend.As the photocatalyst dosage was applied in the range of 0.5g/L to 1g/L,the DMP removal effect increased with the dosage,the degradation efficiency decreased slightly as the dosage increased from 1g/L to 2g/L.Kinetic studies showed that the DMP degradation rate constants of Bi OBr,g-C3N4 and magnetic zmpg-C3N4/Bi OBr/PTh were 0.043,0.052,and 0.193 h-1,respectively,indicating that magnetic zmpg-C3N4/Bi OBr/PTh degraded DMP faster.The magnetic zmpg-C3N4/Bi OBr/PTh was under the neutral conditions of DMP solution,with 1 g/L dosage of catalyst and the initial DMP concentration is 20 mg/L,under light exposure for6 h,DMP removal rate was 78.34%.The cycling experiment was found that the magnetic zmpg-C3N4/Bi OBr/PTh degradation rate of DMP decreased to 3.57%after 2 cycles,and the magnetic retention of the material was good after 3 cycles,but its ph otocatalytic performance decreased 10.95%.While free radical quenching experiments showed that the active species of composite that magnetic zmpg-C3N4/Bi OBr/PTh photocatalytically degraded DMP were h+,·O2-and·OH,in which cavities?h+?played a major role.The possible transformation paths for DMP degradation is ring-opening reaction of the benzene ring and ring breaking until complete mineralization to produce CO2 and H2O. |
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