Effect Of Antibiotics On Photocatalytic Removal Of Heavy Metal Ions

In recent years,the interaction between antibiotics and heavy metal ions in aquaculture wastewater has led to more and more serious combined pollution,and the traditional water treatment technology is difficult to effectively remove it.Due to high efficiency,low consumption and no secondary pollution,photocatalysis technology has a good application prospect in the treatment of combined polluted water.In this study of the removal process of the combined pollution,the mechanism of the effect of SMZ on Cu2+ was mainly revealed.In addition,in order to realize practical application,this paper uses the "time interval" in the reaction process to obtain the Cu-TiO2 photocatalyst,and carries out application research on the catalyst,and evaluates its practical application potential.The main research contents and conclusions of this paper are as follows:(1)The effect of antibiotics on the removal process of heavy metal ions in the photocatalytic system was clarified.The representative antibiotics are sulfamerazine,sulfamethazine,sulfamethoxazole and trimethoprim.Cu2+,Pb2+,Cd2+ and Mn2+ are represented as heavy metal ions.g-C3N4,BiVO4,TiO2 and ZnO are used as photocatalysts.The effects of antibiotics on the removal of heavy metals in different photocatalytic systems were studied.In this technique,the interference of actual water parameters(such as anions,natural organic matter)on the above influencing process is studied.The results showed that the effect of heavy metal ions on antibiotics was mainly to inhibit the degradation of antibiotics,while the effect of antibiotics on heavy metal ions was more complex,especially the presence of SMZ caused repeated fluctuations in Cu2+ concentration and a long "time interval" phenomenon.(2)The mechanism of SMZ affecting Cu2+ photocatalytic removal process was analyzed.The mechanism of the effect of SMZ on the photocatalytic removal of Cu2+ was investigated by means of Cu2+morphologic transformation,solution pH change,zeta potential change,intermediate product analysis and DFT calculation.It is found that the concentration changes of Cu2+ is closely related to the degradation process of SMZ:On the one hand,SMZ degradation will generate many small molecules of acid,reduce the solution pH,and then weaken the adsorption of Cu2+ on the surface of TiO2,showing that the concentration of Cu2+ is constantly rising.On the other hand,the hydroxylation degradation products of SMZ can rapidly combine with Cu2+ to produce Cu-generation products.According to the calculation of DFT,these Cugeneration products have stronger reducing ability and can act as sacrificial agents to significantly accelerate the photocatalytic reduction of Cu2+,resulting in a rapid decline in the concentration of Cu2+ in solution.The dominance of these two effects changed dynamically throughout the degradation process of SMZ,which led to repeated fluctuations of Cu2+concentration.(3)The Cu-TiO2 photocatalyst was recovered successfully by using the "time interval" in the reaction process.Through the application study of the recovered photocatalyst,it is found that the in-situ prepared Cu-TiO2 photocatalyst has good photothermal performance.At the same time,it also has strong hydrogen production and nitrogen fixation performance.The sterilization capacity was also greatly improved.The results showed that photocatalysis technology has a strong practical potential in the field of simultaneously solving antibioticheavy metal combined pollution and realizing heavy metal recycling.However,preexperiments must be carried out to clarify the "time interval" of heavy metal recovery to ensure the maximum recovery efficiency of heavy metals.