Degradation Of Tetracycline By Sulfide Nano Zero Valent Iron Supported On Biochar

Antibiotics in water have the characteristics of complex composition,high toxicity and difficult degradation,which will cause serious water pollution,and occupy a certain proportion in medical textile wastewater.Nanometer zero-valent iron（nZVI）,as a green catalytic material,can catalyze the degradation of a variety of pollutants.However,the application of nZVI is limited by the problem of easy oxidation agglomeration.Modification treatment can effectively overcome the application limitation of nZVI,which is conducive to expand the application of nZVI degradation technology in antibiotic wastewater treatment.Therefore,this paper aiming at the degradation of antibiotics（tetracycline）in the water,build a synergistic catalytic degradation process of nZVI adsorption reduction system,through the sawdust biomass carbon sulfide load and surface modification technology,preparation of the biomass carbon load sulfide nano zero-valent iron（S-nZVI/MB）materials,implement the efficient degradation of tetracycline,The possible degradation mechanism was studied as follows:（1）Optimum preparation conditions of nano-sized zero-valent iron materials supported by carbon.S-nZVI/MB materials with different molar ratios of iron sulfide（S/Fe）and mass ratios of modified biochar to sulfide nanometer zero-valent iron（MB:S-nZVI）were prepared using the degradation effect of tetracycline as the evaluation index.The results show that the optimal molar ratio of S/Fe for S-nZVI/MB material is1:100,and the optimal mass ratio of MB:S-nZVI is 1:1.（2）The prepared biochar supported zero-valent iron nanoparticles were analyzed and characterized.The morphology,element types,crystal structure,element composition and valence state of nano-iron based materials were studied.The results of SEM and TEM analysis show that the dispersion of nZVI particles on the surface of modified biochar is greatly improved.EDS analysis showed that nZVI was successfully vulcanized and uniformly loaded on modified biochar.The results of XRD and XPS analysis showed that nZVI had good crystallinity,and S-nZVI/MB contained Fe⁰ and Fe S.The successful preparation of modified biochar supported sulfated nanometer zero-valent iron was proved.（3）Optimum application conditions for degradation of tetracycline by carbon supported nanometer zero-valent iron.The effects of different factors（p H value,initial concentration of solution,dosage of S-nZVI/MB and H₂O₂,and inorganic salts）on the degradation and removal of tetracycline were investigated.The results showed that when the p H value was 3,the dosage of S-nZVI/MB was 30 mg,and the dosage of H₂O₂ was50 m M,the removal effect of tetracycline was better.In the presence of inorganic salts,the degree of influence on the degradation of tetracycline was:Na Cl>Na₂SO₄>Na NO₃.（4）The possible mechanism of S-nZVI/MB degradation to remove tetracycline was studied and analyzed.Through adsorption kinetics fitting,the adsorption mechanism of S-nZVI/MB was determined to be the result of the joint action of physical and chemical adsorption.·OH and·O₂^-radicals play an important role in the degradation of tetracycline,and·OH is the main active species.The possible degradation path of tetracycline was inferred by determining the mass/charge ratio of the degraded intermediate products by liquid/mass spectrometry.The results of cycle test showed that the degradation rate of tetracycline could reach 82.5%after 5 cycles of test.