Magnetite Assembled On Nanoscale Zerovalent Iron Supported On Activated Carbon Fiber For Cr(?) And Cu(?) Removal From Aqueous Solution

The heavy metals pollution commonly found in aquatic environments.Such heavy metals have caused many pollution incidents globally and pose a huge threat to human life and health.In recent years,nano-zero-valent iron?nZVI?has been used to remove the heavy metal pollutants because of its strong reducibility and high reactivity.However,there are many disadvantages in itself,such as easy to reunite,passivation and limit their scaled practical application.It is can effectively prevent the reunion of nZVI when synthesis of nZVI/magnetite?Fe₃O₄?composites.Activated carbon fiber?ACF?is a readily available porous and carbon-rich material with a large specific surface area.It can closely integrate the nZVI particles into ACF and to increase their stability and efficiency.In this study,the nZVI-Fe₃O₄/ACF composites used to remove Cr?VI?and Cu?II?from aqueous solution.The composites were characterized by field emission scanning electron microscopy?FESEM?,transmission electron microscopy?TEM?,X-ray diffraction?XRD?,and X-ray photoelectron spectroscopy?XPS?.It centres on the influencing factors of Cr?VI?removal from composites material,the simultaneous removal of Cr?VI?and Cu?II?reaction,and the mechanism of action.The specific results are as follows:1.The nZVI,nZVI-Fe₃O₄ and nZVI-Fe₃O₄/ACF nanocomposites were prepared by liquid phase reduction.According to FESEM,TEM,XRD and XPS analysis,the nZVI shown a chain-like structure and is easily agglomerated.After adding the Fe₃O₄ and ACF,the dispersion of nZVI can be effectively improved without changing the structure of nZVI,and t the nZVI-Fe₃O₄ composites were successfully synthesized and loaded on the ACF.2.In the permeable reaction column experiments,the nZVI-Fe₃O₄/ACF composites can quickly and efficiently remove Cr?VI?and Cu?II?from aqueous solution.The Fe₃O₄ and nZVI in the composites did not work alone and displayed good synergetic effects between them.It can be inferred that a high content of Fe₃O₄ in composites corresponds to an improved removal efficiency of Cr?VI?.The ACF has a large surface area and a criss-cross structure that can improve the dispersibility of the nZVI-Fe₃O₄ composites.Moreover,a portion of the generated sediment would be transferred to the ACF,thus enhancing the removal efficiency of Cr?VI?.The experimental results show that:it is beneficial for Cr?VI?removal when the solution pH value and the initial Cr?VI?concentration is 3 and 20 mg·L^-1,respectively.The HCO₃^-,NO₃^-,and Cl^-ions exhibitd inhibited effect of Cr?VI?removal,and the SO₄^2-and Ca²⁺ions can ehanced the removal efficiency of Cr?VI?.The simultaneous removal efficiency of Cu?II?and Cr?VI?can reach 100%after 45 min.The presence of Cu?II?can accelerate remove of Cr?VI?.3.The results of XPS,TEM show that the Cr?VI?removed is mainly by redox co-precipitation.Cr?VI?is reduced to Cr?III?and coprecipitates with the reaction product.The Cu?II?and Cr?VI?are reduced to Cu⁰ and Cr?III?,respectively,when Cu?II?and Cr?VI?are present in the solution.The generated of Cu⁰ can form a nano-bimetallic system with nZVI to promote the Cr?VI?removal.