Effciency Of Degrading Quinolones Antibiotics By Modified Bi₂WO₆ Photocatalyst

With the improvement of living standards of human being,pharmaceuticals and personal care products?PPCPs?have been widely used for disease therapy.For their refractory chemical characteristics,the inefficient adsorption of those antibiotics and subsequent emission in aquatic environment caused pollution and threatened ecosystem balance and human health.Antibiotics has been widely detected in natural waters and threats to ecosystems and human health.Antibiotic Residues in environment will not only cause environmental pollution and do damage to organisms and human,but also cause bacteria drug-resistance and severely interference to microorganism ecosystem.With the development of industry,the shortage of resources and energy has become a serious social problem.Photocatalytic technology which could utilize solar energy has become a new hot spot in the environmental field.Using solar energy as energy source,the reaction is low in cost and the reaction conditions are mild without harmful by-products.As a novel photocatalyst,bismuth tungstate with narrow energy gap can make good use of visible light and have broad prospects of development.In this study,the hydrothermal conditions of bismuth tungstate were optimized by orthogonal experiments,and the activity and reusability were tested by ESR and cycle experiments.Mg²⁺,Fe³⁺,Zn²⁺and Cu²⁺were doped into photocatalyst to improve photocatalytic property.XRD,EDS,SEM,BET,FTIR and DRS methods were used to characterize the morphology and properties of samples.The photocatalytic degradation experiments of NOR and CIP using Bi₂WO₆ as catalysts were carried out to investigate the effects of doped ions and concentration under the irradiation of Xe lamp.The reaction intermediates were determined by HPLC-MS,and the group annihilation experiment and the variation of Zeta potentials were also carried out to help exploring reaction mechanism.The optimum hydrothermal synthesis conditions of Bi₂WO₆ are 20 h,160°C and precursor solution pH=5,and the effect degree was precursor pH>temperature>time.Bi₂WO₆ can produce·OH with high intensity under visible light.The activity of Bi₂WO₆after four cycles decreased by 10.3%,showing its good reusability.As-prepared samples had high purity consisting of 3D-flower-like or spherical particle about 2?m in diameter.The surface area of doped Bi₂WO₆ increased by 25.6%⁶1.1%,providing more active sites.The forbidden band width of doped samples decreased by 7.6%¹5.7%,and the absorption capacity for visible light enhanced.Mg²⁺can greatly improve the property of Bi₂WO₆ at a concentration of 1.0%,while0.5%and 2.0%both will inhibit the performance of Bi₂WO₆.The doping of Fe³⁺,Zn²⁺and Cu²⁺promote the performance of catalyst in a similar way:in the degradation of NOR,the photocatalytic performance of Bi₂WO₆ increased by 10%²0%,which was not affected by the doping concentration;in the degradation of CIP,the degradation rate was promoted from 4%to 63%with concentration in early stage but the final degradation efficiency were all close to 100%.The photocatalytic degradation process of NOR and CIP are in accordance with the quasi-first-order reaction kinetics model.The degradation of NOR and CIP are both achieved by the destruction of piperazine ring and substitution of fluorine atom.The structure of the quinolone group is relatively stable and will not be destroyed during the reaction.The role of h⁺and·O₂^-in photocatalytic reactions accounts for about 70%and 30%respectively.The metal ions doping promotes the adsorption of catalysts by means of electron pair sharing or transfer.