| With the rapid progress in science and technology,the rapid social development,people's living standards improve,but followed by increasingly serious environmental problems,more and more serious pollution of heavy metals not only caused huge economic loss,but also threatens our life health and safety,and heavy metal governance problem is imminent.As one of the most common heavy metal pollution,chromium pollution has been widely concerned by the society.The treatment of chromium pollution,such as adsorption,chemical precipitation,electrodeposition,solvent extraction,photochemical reduction and reverse osmosis,has been used in the treatment of chromium pollution,and,zero-valent iron,as a cheap and environmentally friendly reducing reagent,has attracted wide attention.It is an ideal reducing agent and has been widely used in the treatment of chromium pollution,however,it still faces the key problems of poor activity towards the removal of target pollutant,narrow pH response range and low electron utilization,so it is very important to find a simple and effective modification method of zero-valent iron,therefore,in order to study a simple and effective zero-valent iron modification method and make it more suitable for the treatment of chromium pollution,our research contents are as follows:1.As a new zero-valent iron modification strategy,sulfurization method has attracted the attention of many researchers,because it can not only significantly improve the activity of zero-valent iron,but also expand its pH range and improve its electron utilization,but the widespread use of sulfadation method in aqueous results in the loss of zero-valent iron electrons and the formation of a thick iron(hydrogen)oxide layer on the surface.Therefore,this part adopts the alcohol-thermal method,a non-aqueous phase synthesis method,to achieve the sulfidation of micron-scale zero-valent iron.We successfully synthesized sulfidated micron-scale zero-valent iron with different S/Fe mass ratios by alcohol-thermal method,through XRD and TEM characterization,we found that high crystallinity FeS were generated on the surface of zero-valent iron.and applied them to the removal of Cr(?)from water,and we found that its activity was significantly improved,when the S/Fe mass ratio was 0.05,the maximum removal efficiency of Cr(?)was achieved,we found the surface area normalized Cr(?)removal rate constants(K')of S-ZVI0.05 was 120 times more than the K' of mZVI,and in alkaline condition and under the condition of high concentration of Cr(VI)also has higher activity.It was found that compared with the S-ZVI synthesized in water phase,S-ZVIs synthesized in alcohol phase has higher activity of removing hexavalent chromium,which is because the S-ZVIs synthesized by alcohol-thermal method has more ferrous ion their surface.2.In order to further improve the chromium removal performance,considering the nano zero-valent iron has better ability of reducing hexavalent chromium and carbon materials excellent adsorption performance,the advantages of alcohol-thermal method,we synthesized activated carbon loaded nano zero-valent iron,then get the n-ZVI/AC sulfidated by alcohol-thermal method,make materials have high adsorption and reduction at the same time the ability of hexavalent chromium.the results showed that at the dose of 0.04 g/L,the S-nZVI0.60/AC whose S/Fe mass ratio was 60%could almost completely remove 5 ppm Cr(VI),which has reached the national standard of 0.05 g/L for the highest concentration of chromium in drinking water,through various characterization,we found that the sulfidated material has a smaller specific surface area,a lower corrosion potential,and more surface ferrous iron.we found the surface area normalized Cr(VI)removal rate constants(K')of S-nZVI0.60/AC was 9 times more than the K' of nZVI/AC,though the XPS and TF-IR characterization,it was found that the removal of Cr(VI)with nZVI/AC and S-nZVI0.60/AC were both composed of adsorption,reduction and co-precipitation. |
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