Performance And Mechanism Of Supported And Modificated Fe/Ni Nanoparticles For The Removal Of Heavy Metals And Chlorinated Organics

Heavy metals and persistent chlorinated organics are key contaminants in the wastewater that could be treated by nanoscale zero-valent iron.To solve the problem of aggregation and passivation of nano zero-valent iron,supported nano Fe/Ni was prepared by using nickel as doping metal and attapulgite as carrier,while surface modifier was used to enhance the performance.Zn???and 2,4-dichlorophenol were chosen as representatives,and the performance and mechanism of supported and modificated Fe/Ni nanoparticles for the removal of heavy metal and chlorinated organics were studied.The results are as follows:?1?Attapulgite was chosen as carrier,the appropriate mass ratio of Fe to attapulgite was 1:2.The problem of aggregation can be solved by supporting and the specific surface area of attapulgite supported Fe/Ni?ATP-Fe/Ni?was 2.6 times that of Fe/Ni.Carboxymethyl was served as surface modifier,and the appropriate concentration of carboxymethyl was 10mmol/L.The particle dispersion stability was improved after modification.?2?The results of influential factors indicated that larger pH and higher temperature as well as lower Zn???concentration were beneficial to the removal of Zn???by ATP-Fe/Ni.As for 2,4-dichlorophenol,lower pH and higher temperature as well as lower 2,4-dichlorophenol concentration were beneficial to the reduction.?3?The removal of Zn???by ATP-Fe/Ni and Fe/Ni supported on carboxymethyl modified attapulgite?CMC-ATP-Fe/Ni?fitted well with the Langmuir adsorption model.After modification,the maximum adsorption capacity can be increased from129.9mg/g to 141.8mg/g.The mechanism can be attributed to the coordination between Zn???and iron oxide on the surface of zero-valent iron.In addition,Zn???can also be removed by the forming of Zn?OH?₂ chemical precipitation.?4?L-H model indicated that the mechanism of 2,4-dichlorophenol removal by ATP-Fe/Ni and CMC-ATP-Fe/Ni in the water contained adsorption and reduction,and reduction was the main process.After supporting and modification,the maximum adsorption-reduction capacity can be increased from 801.1mg/g to 1003.2mg/g and1310.0mg/g respectively.The pathwayof the removal was that most2,4-dichlorophenol was directly reduced to phenol,and the rest was reduced to2-chlorophenol and 4-chlorophenol first,which was then completely reduced to phenol.