Photocatalytic Removal Of Tetracycline From Water By Bismuth Oxybromide Doped With Metal Ions

Tetracycline antibiotics have been widely used in medical,agricultural,animal husbandry and other industries since their inception,and have made indelible contributions to improving people’s production and living standards.Tetracycline antibiotics are macromolecular organic compounds and their stability is relatively good,but their large presence in the environment can easily induce cancer,enhance bacterial drug resistance,and even form super bacteria,which are difficult to degrade and transform by conventional means.At this stage,people’s use of tetracycline is increasing,resulting in a large number of tetracycline molecules entering and depositing in the natural water and soil environment in various ways,which gradually increases its stock in nature and causes various adverse effects on the environment.In response to this problem,various methods for removing tetracyclines have been developed.However,conventional physical,chemical and biological treatment methods are difficult to achieve ideal results due to its excellent molecular stability.Since the photocatalytic technology was proposed,because of its green and economical advantages at the same time,the majority of scientific researchers have a great interest in it.However,the traditional photocatalysts represented by titanium dioxide（Ti O₂）and zinc oxide（Zn O）have disadvantages such as low utilization of photogenerated carriers and narrow photoresponse range,so their use is greatly restricted.Bismuth-based semiconductors are considered to be very promising catalysts that can respond to visible light.Bismuth oxybromide（Bi OBr）is a typical bismuth-based semiconductor with a band gap of about 2.7e V.There is a disadvantage of low separation rate of photogenerated electron-hole pairs for the intrinsic type Bi OBr,which limits its application in the field of photocatalysis to a large extent.Bi OBr also has its special structural advantage,showing a unique layered structure,so the slight change in the lattice can change its original electronic structure.The photocatalytic ability of Bi OBr can be tuned by changing its electronic structure through simple and effective ions doping.Therefore,different metal ions were selected to dope Bi OBr to adjust the photocatalytic ability of Bi OBr photocatalyst to degrade tetracycline in this paper,and the effect of different environmental factors in the whole photocatalytic system on the photocatalytic performance of photocatalyst to degrade tetracycline was systematically studied.The main results are as follows:（1）Pure Bi OBr was prepared by simple solvothermal method.During the preparation process,we synthesized a series of Bi OBr samples by controlling the ratio of Br and Bi added.The corresponding photocatalytic ability was tested with tetracycline as the pollutant.The samples were characterized by XPS,XRD and SEM,and their phase composition,morphology and surface properties were systematically studied,and the reasons for the differences in the photodegradation performance of Bi OBr samples with different ratios of Br/Bi were explored.（2）Sn⁴⁺was successfully doped into the Bi OBr lattice by a simple one-step solvothermal method,and a series of Bi OBr samples with different Sn⁴⁺doping concentrations were prepared by controlling the amount of Sn Cl₄·5H₂O added（using Sn Cl₄·5H₂O as the Sn source）.Corresponding photocatalytic experiments were carried out with tetracycline as a pollutant,and the effects of doping ion concentration,p H value and competing ions on the photocatalytic degradation of tetracycline were systematically analyzed.The corresponding samples were selected for PL,XPS,XRD and photoelectrochemical tests,various properties of the catalysts were studied,and the mechanism of enhancing the photocatalytic performance of the samples was deeply explored.（3）Al³⁺was successfully doped into the Bi OBr lattice by one-step solvothermal method,and the photodegradation properties of the samples were investigated with tetracycline as a contaminant.The principle of photocatalytic performance improvement of Bi OBr is studied by XRD,SEM,photoelectrochemical test and other characterization methods,and the ion selection method is briefly studied by comparing various data of Sn⁴⁺doped BiOBr.