Research Of 2D-MoS₂/nZVI For Pollutants Removal In Water And First Principles

Heavy metal ions and phenolic organics are the main pollutants in environmental governance today,and the development of a low-cost and high-efficiency repair agent has become a research hotspot.Nano-zero-valent iron(nZVI)combines the advantages of nano-materials and zero-valent iron,which has the characteristics of large surface-area,strong reducibility and great potential for development in water restoration.However,the agglomeration and oxidation problems of nZVI reduce its reactivity and effectiveness,which brings giant challenges to practical application.The research applicates a typical two-dimensional material 一 molybdenum disulfide(MoS2),nZVI particles are modified by high specific surface area and steady chemical properties,and successfully synthesizes two-dimensional molybdenum disulfide supported nano-zero-valent iron(2D-MoS2/nZVI)composites.Taking Cr(Ⅵ)and 2,4,6-trichlorophenol as typical representatives,the processing performance of composite materials is studied and first-principles calculations are used to explore the mechanism.The main contents are as follows:(1)Using 2D-MoS2 as the carrier,FeSO4·7H2O and NaBH4 as raw materials,2D-MoS2/nZVI composites were prepared by the liquid-phase reduction method.The effects of the precursor mass ratio and reaction solvent on the preparation of composites were studied.Characterization by XRD,SEM-EDS,BET and XPS showed that nZVI particles were dispersed well with a diameter of 70-150 nm;the composites formed a mesoporous structure with a specific surface area of 78.52 m2/g.First-principles calculations confirm that 2D-MoS2 has good adsorption performance for Fe(Ⅱ),and there is a strong chemical interaction between them.(2)The 2D-MoS2/nZVI composites prepared under optimized conditions were used to treat Cr(Ⅵ)in water,the concentration was detected by an ultraviolet spectrophotometer.The influence of auxiliary means,pH value of the solution,initial concentration of Cr(Ⅵ),and the amount of composites added was studied.It was found that the removal capacity of Cr(Ⅵ)reached 221.22 mg/g,which is better than the removal ability of the repair agents in the current related literatures.Ultrasound can significantly accelerate the reaction rate,and low pH can promote electron transfer and stimulate reaction activity.The synergy between 2D-MoS2 and nZVI promotes the adsorption and reduction of Cr(Ⅵ).The simulation results turn out that the Fe-doped MoS2 surface can improve the adsorption of Cr atoms.Compared with the adsorption of pure MoS2,the adsorption energy increases from 1.19 eV to 2.76 eV,and the amount of charge transfer is also significantly improved.Combined with XPS analysis,the main mechanism for removing Cr(Ⅵ)is proposed:the adsorption of 2D-MoS2/nZVI to Cr(Ⅵ)and the strong reduction of nZVI.(3)The water solution containing 2,4,6-trichlorophenol was treated with 2D-MoS2/nZVI composites,and high performance liquid chromatography was used to detecte the concentration.The effects of the pH value,the initial concentration of 2,4,6-trichlorophenol and the amount of composites added were investigated,and it turns out that the removal efficiency increased as the pH value decreases.The removal process conforms to the Langmuir adsorption isotherm and pseudo-second-order kinetic model.Through simulation calculations,it was found that the presence of Fe on the surface of MoS2 enhances the binding ability with-OH and-Cl functional groups,and improves the adsorption of 2,4,6-trichlorophenol by the composites.