| Antibiotics have been widely used to treat and prevent bacterial infections in veterinary,human medicine,and agriculture.The widespread use of antibiotics and the low efficiency and poor degradation performance of traditional wastewater treatment methods have led to the continuous accumulation of antibiotics in the aquatic environment.Photocatalytic degradation seems to be the best option because of its environmental friendliness and low cost.Therefore,developing an efficient photocatalyst has become a crucial part of photocatalytic degradation technology.TiOF2 is a new type of semiconductor material that can absorb sunlight,but its development in the field of photocatalysis is limited due to its low utilization rate of sunlight,low photocatalytic degradation efficiency,and insufficient stability.g-C3N4 has significant advantages such as narrow band gap,low toxicity,high stability,easy availability,and low cost.Therefore,in order to prepare a new type of photocatalyst for efficiently degrading TCH,the gC3N4/TiOF2(CNTOF)composite photocatalyst was synthesized for the first time by the ethanol solvent method by compounding g-C3N4 and TiOF2 monomers.The TiOF2/HTiOF3(TOF)composite photocatalytic material was obtained by adjusting and controlling the composite OHTiOF2/HTiOF3(OHTOF)after it was modified with NaOH.The hole pair recombination efficiency and other properties,the photocatalytic activity has been further improved.In this paper,tetracycline hydrochloride antibiotic wastewater was taken as the degradation object,and its photocatalytic performance was investigated under simulated sunlight conditions in the laboratory.Using XRD,SEM,TEM,BET,ESR,FT-IR,XPS,UV-Vis DRS and PL and other characterization and testing methods,the crystal form,morphology,crystal plane,specific surface area and porosity,active species of photocatalytic materials were analyzed,surface functional groups,elemental composition,light absorption characteristics,and electron-hole recombination strength were analyzed to analyze the reasons for the improved performance of composite photocatalytic materials.performance impact.The repeated stability of the material was further studied,and the possible photocatalytic mechanism of CNTOF and OHTOF series materials was proposed by radical trapping experiments.The specific research content and experimental results of this paper are as follows:(1)CNTOF composite photocatalyst:g-C3N4 prepared by thermal polycondensation method and TiOF2 prepared by hydrothermal method were used as precursors,and CNTOF series samples were prepared by ethanol solvent method.The SEM and TEM results indicated that the reticulated g-C3N4 and the cubic TiOF2 were successfully recombined in the CNTOF samples.Compared with the specific surface area(7.11 m2/g)and pore volume(0.02 cm3/g)of TiOF2,the specific surface area(13.9 m2/g)and pore volume(0.05 cm3/g)of CNTOF20 were both increased by two times;UV-Vis DRS shows that the absorption in the visible light region of the CNTOF sample becomes stronger;the forbidden band width is significantly narrowed from 3.27 eV to 2.75 eV,so that it has a larger photoresponse range;PL shows that CNTOF20 shows that the fluorescence intensity is reduced,and the electron-hole pair Recombination rate is reduced.The results of ESR and trapping experiments jointly indicated that the active species of CNTOF20 in photocatalytic degradation was ·O2-.The g-C3N4/TiOF2 heterojunction can be formed by analyzing the mechanism from the above-mentioned characterization results such as Mott-Schottky curve and UV-vis,which belongs to a typical Z-type structure.The best effect was obtained by adding 300 mg/L CNTOF20 to the CNTOF series samples.The degradation rates of 100 mL 10 mg/L tetracycline hydrochloride,oxytetracycline hydrochloride and chlortetracycline hydrochloride could reach 85.5%and 61.4%within 2.5 hours.and 84.1%,the process of photocatalytic degradation of antibiotic wastewater conformed to the first-order kinetic model.And the degradation rate of CNTOF20 reused after five times can still maintain more than 80%antibiotic removal rate.(2)TOF and OHTOF composite photocatalyst:In the hydrothermal process of preparing TiOF2,g-C3N4 was added to induce the formation of intermediate product HTiOF3 to obtain TOF series samples.In order to further improve the catalyst performance,the samples were modified with NaOH,and the photocatalytic performance of the OHTOF series samples under visible light was mainly studied.SEM and TEM results showed that the cube-like TiOF2 was the majority,and with the increase of the proportion of g-C3N4,more and more HTiOF3 crystals close to hexagonal prisms were gradually produced,while the OHTOF samples showed more complex nano-networks.Compared with the specific surface area of TOF 15 monomer(7.11 m2/g),the specific surface area of OHTOF 15(29.31 m2/g)increased by four times;UV-Vis DRS showed that the NaOH modification treatment reduced the forbidden band width of TOF samples,It further enhanced its visible light absorption properties,thereby improving its visible light photocatalytic activity;PL showed that OHTOF15 indicated that the fluorescence intensity decreased and the electron-hole recombination rate decreased.The results of ESR and trapping experiments show that the active species that play an important role in photocatalytic degradation is ·O2-,and the formed TiOF2/HTiOF3 heterojunction is a typical Z-type heterojunction.The elemental analysis results of XRD,FT-IR and XPS indicated that there were only two species of HTiOF3 and TiOF2 in the catalytic material,FT-IR showed that the surface hydroxyl functional groups increased after alkali washing,and more surface hydroxyl functional groups were more conducive to the formation of free radicals.Under the same conditions as the CNTOF series,the photocatalytic effects of TOF8 and OHTOF15 were the best within 2.5 h,and the degradation rates of tetracycline hydrochloride reached 86.3%and 94.2%,respectively,and the OHTOF series was further improved.The process of photocatalytic degradation of antibiotic wastewater conformed to a first-order kinetic model.The degradation rate of OHTOF 15 reused after five times still maintained the antibiotic removal rate of more than 85%. |
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