Study On Preparation Of Bismuth Tungstate Modified Straw Biochar And Its Photocatalytic Degradation Of Tetracycline In Soil

In order to solve the problem of the increasingly serious pollution of antibiotics of tetracycline in agricultural soil,in in this study,biochar（N-Biochar）was obtained by calcining corn stover with urea mixture,and then the N-Biochar was modified with bismuth tungstate to synthesize a novel photocatalyst——Bi₂WO₆/N-Biochar.A series of characterization analyses were performed on Bi₂WO₆/N-Biochar to explore its physical and chemical properties,such as TEM、XRD、XPS etc.The photocatalytic degradation performance of Bi₂WO₆/N-Biochar was analyzed via the degradation of tetracycline hydrochloride in water and free radicals quenching test.After that,the mechanism of enhanced photocatalytic activities of Bi₂WO₆/N-Biochar was explored.Afterwards,Bi₂WO₆/N-Biochar was applied in remediation of tetracycline hydrochloride contaminated soil.The effect of Bi₂WO₆/N-Biochar on the growth and development of corn in the soil.The effect of Bi₂WO₆/N-Biochar application amount（0.67wt.%,1.33wt.%,2wt.%）and soil water content（10%,20%,40%）on degradation performance was explored,in addition,the degradation mechanism was explored.These results could provide a theoretical basis for the application of catalytical modified straw biochar in situ remediation of antibiotic pollutants in the soil.The main research contents of this study are as follows:（1）The results of characterization of Bi₂WO₆/N-Biochar showed that N-Biochar had a spatial structure similar to that of C₃N₄.The nanoparticle structure of Bi₂WO₆/N-Biochar and heterojunction structure was synthesized by coupling N-Biochar with Bi₂WO₆,which has a good specific surface area,in addition,the band gap was reduced to 2.30e V.Moreover,the iterative energy level structure of the heterojunction structure that can extend the migration path of photogenerated carriers,and has better conductivity than Bi₂WO₆,so that Bi₂WO₆/N-Biochar owned stronger photocatalytic activity.The main active substances of Bi₂WO₆/N-Biochar produced were e^-and O₂^-·,Among them,BW/N-B-2 has the best photocatalytic degradation performance.It can degrade 81.79%of TCH in water in 75 minutes,and exhibits good photocatalytic stability.（2）The results of the corn seedling pot experiment showed that there was no adverse effect on the germination of corn seeds after applying BW/N-B-2 in soil.The germination rate can still reach 100%.The content of tungsten and bismuth in the corn stems and leaves increased significantly,but the effect on the roots was small.Moreover,with the increase content of BW/N-B-2,the plant height and stem thickness of corn did not change significantly compared with the blank treatment.Hence,it can be determined that BW/N-B-2 did not affect the normal growth and development of corn.（3）After that,photocatalytic degradation of tetracycline hydrochloride in soil over BW/N-B-2 was implemented.The results showed that the degradation performance of BW/N-B-2 was positively correlated with the application amount of BW/N-B-2 and the soil water content,respectively.Among them,The best application amount was 2wt.%,and the degradation rate can reach 40.05%in 7 days.The best soil moisture content was 40%,and the degradation rate was51.80%in 7 days.And then,under the optimal application amount and soil water content（2wt.%-40%）,the photocatalytic degradation reaction kinetics of TCH in the soil was explored.It was determined that the equilibrium of degradation can be reached after 7 days with illumination.It has been identified that the main active substances generated by BW/N-B-2 were O₂^-·and photogenerated e^-,which directly or indirectly undergo redox reactions to degrade TCH in soil.During the reaction,the p H value and organic matter content of the soil were not affected,which mean that no secondary damage was caused to the soil.