Preparation Of Magnetic Molybdenum Based Photocatalyst And Its Degradation Mechanism For Tetracycline

Tetracycline antibiotics in water can cause chemical pollution and spread of resistance genes,which pose a serious threat to human health and ecological environment.The photocatalytic degradation technology is simple,efficient,safe,environment-friendly and low-cost,which shows excellent application potential for the removal of TC in water.In the application of photocatalysis,how to develop a high photocatalytic activity,low cost,stable photocatalyst is the key technology.In this paper,three kinds of magnetic photocatalysts were prepared by doping Fe3O4,g-C3N4 and biochar in molybdenum based photocatalysts.They were characterized by XRD,XPS,EDX,TEM,FT-IR,UV Vis DRS,PL,bet,VSM,ESR and photocurrent.The photocatalytic activity of the photocatalyst was evaluated by the degradation rate of tetracycline solution under visible light irradiation.In addition,the effects of different doping ratio and active material quencher on degradation were investigated.At the same time,the magnetic properties of the photocatalyst are endowed to overcome the defects of the nano powder catalyst which is difficult to recycle and further improve the economic benefits of the photocatalyst:(1)Fe3O4/g-C3N4 was synthesized by coprecipitation of g-C3N4 and Fe3O4.Furthermore,Z-type magnetic photocatalyst Fe3O4/g-C3N4/MoO3 with high photocatalytic activity was prepared by Co-calcining with H8MoN2O4 and doping MoO3.In addition,the effects of doping ratio of MoO3 and active material quencher on the degradation were investigated.The results showed that Fe3O4/g-C3N4/MOO3 nanocomposites were successfully prepared,and no impurity was detected in the characterization.Among them,Fe3O4/g-C3N4/MoO3(30%)nanocomposites have the highest ability to remove TC.Superoxide radical(·O2-)is the main reaction species of photocatalytic degradation.After 30 min dark treatment and 120 min light treatment,94%of TC is removed.Its photocatalytic activity is about 6.9,5 and 19.9 times that of MoO3,g-C3N4 and Fe3O4/g-C3N4.The excellent photocatalytic performance of the photocatalyst is mainly attributed to the Z-type structure formed between MoO3 and g-C3N4,which effectively enhances the separation of electrons and holes,and makes full use of the effective electrons and holes to produce living substances.Secondly,due to the doping of Fe3O4,the visible light absorption range and ability of the photocatalyst are expanded,and the photocatalyst is endowed with good magnetic separation characteristics,which improves the activity of the photocatalyst and enriches the effective means of its recovery.(2)Fe3O4 was deposited on the surface of poplar powder by coprecipitation method to obtain magnetic biomass.Furthermore,the composite magnetic photocatalyst MBM containing MoO3 and magnetic biochar was prepared by Co-calcination with ammonium paramolybdate.The results show that:due to the low content of MoO3,no obvious characteristic peaks can be observed in XRD and FT-IR spectra,but the characteristic peaks of Fe3O4 and BC can be clearly observed.The results of XPS,EDS,TEM,HRTEM and SEM showed that the three components were combined successfully without obvious impurities.The results showed that MBM-2 with the best composite ratio showed excellent photocatalytic degradation activity,·O2-was the main reaction species of photocatalytic degradation,except for 95%TC under 60 min dark treatment and 120 min light treatment.The improvement of photocatalytic activity is attributed to the doping of Fe3O4 and biochar,which significantly improves the light absorption range of the photocatalyst and the separation efficiency of e-and h+.In addition,the introduction of Fe3O4 can effectively produce ·O2-,which further improves the effective utilization of e-and h+in photocatalyst.The photocatalyst is endowed with excellent paramagnetism,so that it can be separated by external magnetic field,and the economic benefit in practical application is improved.(3)Fe3O4 was deposited on the surface of poplar powder by coprecipitation method to obtain magnetic biomass.PbMoO4 was prepared by deposition method using Pb(NO3)and Na2MoO4 as precursors.Magnetic biomass was added into PbMoO4 synthesis system,and the solution was mechanically stirred and evaporated to obtain fully mixed magnetic mixture powder.Furthermore,the composite magnetic photocatalyst MBL with magnetic biochar as carrier was synthesized by Co-calcining the magnetic mixture powder.The results showed that PbMoO4 in MBL was evenly distributed on the magnetic biochar,and the effective combination of the three components was confirmed in a number of characterization,and no other impurities were found.When the photocatalyst was loaded by magnetic biochar,the wavelength range of light absorption of the composite catalyst was significantly increased,the separation efficiency of e-and h+ in the catalyst was improved,and the photocatalytic degradation activity of the photocatalyst was improved.In this photocatalytic system,·O2-is the main active substance for TC degradation,and 85%of TC is removed after 60 min dark treatment and 120 min light treatment.