Effective Enhancement Of Pyrite On Zero-valent Iron For The Removal Of Hexavalent Chromium And Tetracycline Hydrochloride

Zero-valent molten iron treatment technology has attracted more and more attention due to its high removal efficiency,low cost and environmental protection of various pollutants.However,in practical applications,its reactivity is reduced due to the presence of surface passivation and corrosion products,and the increase in p H during the reaction will inhibit its removal of contaminants.Therefore,this study intends to use natural pyrite to modify zero-valent iron and study its removal performance for heavy metals and organic matter.In this paper,hexavalent chromium and tetracycline hydrochloride are used as the representatives of heavy metals and antibiotics,and the removal process of hexavalent chromium and tetracycline hydrochloride in water by zerovalent iron,pyrite,and zerovalent iron/pyrite composite materials is discussed.and mechanism studies.Specific research contents include:（1）Preparation and characterization of zero-valent iron/pyrite composites.Supported zero-valent iron/pyrite composites were prepared by a liquid-phase reduction method.Scanning electron microscopy（SEM）results show that the addition of pyrite can effectively solve the problem of zero-valent iron agglomeration.X-ray photoelectron spectroscopy（XPS）characterization results showed that Fe S and other iron sulfides were produced on the surface of Fe0 in the zero-valent iron/pyrite composite;（2）Research on the performance of zero-valent iron/pyrite composites to remove Cr（VI）by reduction.With the increase of the dosage of the three materials,the removal rate of Cr（VI）increased,and with the increase of p H and initial concentration of Cr（VI）,the removal rate of Cr（VI）decreased.The zero-valent iron/pyrite composites can remove Cr（VI）well in the medium of p H=5.0～10.0,while the reduction and removal rate of the zero-valent iron system to hexavalent chromium decreases significantly when the initial p H≥8.0,indicating that The mixed reaction system has a wider p H applicable range.XPS characterization results show that zero-valent iron and zero-valent iron/pyrite composites have both adsorption and redox effects on Cr（VI）.After part of Cr（VI）is adsorbed on the surface of the material,part of Cr（VI）is reduced to Cr（III）,Fe⁰and Fe（II）in the material are oxidized to Fe（III）.（3）Study on the performance of zero-valent iron/pyrite composites for removal of tetracycline hydrochloride.It can be seen from the experimental data that when the initial concentration of tetracycline hydrochloride is 50 mg/L,the material dosage is 1g/L,and the initial p H is about 4.5,the removal rate of tetracycline hydrochloride by the zero-valent iron/pyrite composite material is relatively high.Zero-valent iron will reach 100%faster.In the presence of coexisting anions,in the presence of Cl^-and NO₃^-,the three materials have little effect on the removal of tetracycline hydrochloride;H₂PO₄^-,CO₃^2-,SO₄^2-have little effect on zero-valent iron,zero-valent iron/pyrite Removal of tetracycline hydrochloride by mineral composites was strongly inhibited.It can be obtained from the UV-Vis full-scan spectral data that when pyrite and zero-valent iron are combined to degrade tetracycline,the four ring structures of tetracycline hydrochloride are attacked due to the hydroxyl radicals generated during the reaction.The ring structure is ruptured.Ferric iron is easily combined with the A ring of tetracycline in solution,and the action sites of the composite material on tetracycline hydrochloride are mainly concentrated in the B,C,and D rings.