Application Of Modified Nano-zero-valent Iron In Restoration Of Water Environment

Nano-scale zero-valent iron(nZVI)is one of the most intensively studied materials for environmental restoration uses over the past few decades because of its high specifific surface area and strong reducing power.However,there are many shortcomings in the practical application of nZVI,such as easy agglomeration,instability,easily passivated,which seriously limits its application in environmental remediation.A large number of studies have shown that nZVI loading on a stable carrier can effectively improve the above-mentioned defects.In many carriers,carbon materials have been paid more attention because of their well-developed pore structure,large specific surface area and green safety.In this study,Fe0/C composites were prepared by hydrothermal synthesis and carbothermal reduction.The materials were characterized by a variety of characterization instruments,and were applied to the removal of typical pollutants in water.The removal mechanism of typical pollutants in water was analyzed and clarified.The summary is as follows:(1)A11 kinds of characterization analysis show that the zero valence iron is successfully loaded on the surface of carbon material,which improves the shortcomings such as easy aggregation and instability of zero valence iron,and greatly improves the removal of pollutants from the composite material.(2)The removal rate of Cr(?)in water by Fe0/C composites which prepared in this study is 3.8 times higher than that of ZVI.The removal process of Cr(?)in water accords with the quasi-second order adsorption kinetic equation,which indicates that the removal process of Cr(?)is co-existing of physical adsorption and chemical redox,but the chemical redox is the dominant one.The main mechanism is that ZVI corrosion provides electrons for the reduction of Cr(?)to Cr(?),and then Fe(?)with Cr(?)to form iron chromium hydroxides deposited on the surface of the material.(3)The removal rate of NO3-in water by Fe0/C composites which prepared in this study is 2.9 times higher than that of ZVI.The removal rate of NO3-by composite materials under alkaline condition is still 60%,which may be due to the formation of the iron-carbon cell effect inside the composite.The mechanism study shows that the removal of NO3-in water mainly depends on redox reaction and physical adsorption.ZVI corrosion provides electrons for the reduction of NO3-to nitrogen-containing compounds such as NH3.At the same time,the existence of the carbon carrier not only has the function of adsorbing the pollutants,but also improves the defect of easy agglomeration of the ZVI.(4)The removal rate of PCE in water by Fe0/C composites which prepared in this study is 1.5 times higher than that of ZVI.Moreover,the removal rate of tetrachloroethylene is higher in acidic and alkaline conditions,which is the result of the reaction of iron and H+,OH-in solution in the composite.The mechanism study shows that the removal of the PCE in water is dependent on the redox reaction and the adsorption of the carbon material.