Research On The Remediation Of Tetracycline Pollution In Waters With ZnFe₂O₄ Composite Photocatalyst

Tetracycline（TC）was used widely and detected out in various water matrixes.The presence of TC in water matrix caused negative impacts on the ecology and human health.Therefore,it was urgent to search for technologies with high removal efficiency,friendly to environment,and low cost for solving the problem of TC pollution in the water matrix.Among them,photocatalytic degradation of TC was considered a desirable method.While the development of photocatalysts with high efficiency,easily recoverable,low cost,and good stability was the key to the application of photocatalytic technology for the treatment of TC pollution in the water matrix.Therefore,two kinds of ZnFe₂O₄-based heterojunction photocatalysts compounding ZnFe₂O₄ photocatalyst CuWO₄ and ZnFe₂O₄ with BC and ZnO were successfully prepared,both of them had high photodegradation efficiency and were recovered easily by magnetic separation.The properties of the prepared photocatalytic materials were analyzed by XRD,XPS,SEM,EDX,TEM,FT-IR,PL,VSM,and ESR.The photocatalytic activity was evaluated using TC as the target pollutant.Primary results of this study were as follows:（1）The ZnFe₂O₄/CuWO₄（ZW）was synthesized by hydrothermal-co-precipitationcalcination method,and the photocatalytic activity was evaluated by the degradation of TC in water.ZW heterojunction enhanced the visible light absorption range and further improved its electron-hole pair separation efficiency,resulting in the improvement of photocatalytic activity.After the dark adsorption for 90 min followed by the illumination for 150 min,ZW composites could remove 86.5%of TC removed.Among the ultrapure water（UW）,municipal wastewater（MW）,and swine farm wastewater（SW）,the magnitude of the ability to remove TC was in the following order:UW（86.5%）>MW（78.2%）>SW（74.8%）.Based on the characterization and experimental results,the main active species in the catalytic system of ZW were Hydroxyl radicals（·OH）,superoxide radicals（·O2-）,and holes（h+）,and the degradation mechanism of ZW was a direct Zscheme degradation mechanism.（2）The ZnFe₂O₄/BC/ZnO（ZBO）composite photocatalysts were obtained by loading ZnFe₂O₄ and ZnO onto BC via the solvothermal-co-calcination method.The characterization results showed that the composite expand the light absorption range.Acting as a conductive channel,BC improved the electron transfer efficiency between ZnFe₂O₄ and ZnO and enhanced the electron-holes separation so that the photocatalytic activity was enhanced.After the dark adsorption equilibrium of ZBO in different water matrixes,the magnitude of TC removal after 90 min of light was in the following order:UW（85.6%）>SW（77.8%）>MW（76.9%）.From the characterization and experimental results,the main active species in the catalytic system were ·OH and ·O2-,and the degradation mechanism of ZBO was an all-solid-state Z-scheme reaction mechanism.（3）The all-solid-state Z-scheme composite photocatalyst ZBO showed superior performance over the direct Z-scheme composite photocatalyst ZW in the photocatalytic degradation of TC.The time of TC removal was reduced by 120 min for ZBO,the catalyst dosage was reduced by 30 mg,and the reaction rate was 2.47 times higher than that of the ZW composite photocatalyst.