Efficiencies And Mechanisms Of Removing Nitrogenand Phosphorus Simultaneously Using Montmorillonite/zero Valent Iron Nanocomposites

We used the chemical reduction method with sodium borohydride to synthesize zero valent iron(Fe0)nanocomposites,in which the naturally occurring montmorillonite(Mt)that has good dispersion and absorption properties was applied as carrier.And we called Mt/Fe0.In order to know the structure of the Mt/Fe0,particle size and the element distribution,we used techniques,including X-ray diffraction(XRD),Scanning electron microscopy(FESEM),Infrared Spectroscopy(FTIR),Thermogravimetric Analysis(TGA),and X-ray photoelectron spectroscopy(XPS).Then we used the Mt/Fe0 to remove nitrogen and phosphorus from aqueous solutions,and also explore the adsorption mechanisms and the related factors by using FESEM and XPS.We can obtain some results:Fe0 particles were dispered well on the surface of montmorillonite,and the particle size is about 55 nm.There is the structure of core-shells in Fe0,and the core of a-Fe was coated by shells consisting of magnetite and/or hematite iron oxides,which was 3nm.The Mt/Fe0 has high antioxidant ability,so it can be saved in room temperature.We used 0.05 g Mt/Fe0 to removal a 25 mL liquid of PO41-(30mg/L P),NO3-(30 mg/L)respectively,we can discovery:pH is the major factor of effecting the capacity of eliminating nitrogen and phosphorus.The removal rate was higher when the pH value of solution is lower.The reaction occurring between nitrogen/phosphorus and Mt/Fe0 is rapidly,and the stabilization time is about 60 minutes.The reaction can occur in room temperature,because the temperature has less effect on removal rate.At the same time,the adsorption rate will be different because of the different Fe/N and Fe/P.The adsorption of nitrogen and phosphorus were fitted well with pseudo-second-order model.For removal of phosphorus,Freundlich adsorption isotherm other than Langmuir adsorption isotherm fits.SEM and XPS analyses indicated that the reaction mechanisms of Mt/Fe0 adsorption for phosphorus involved adsorption-precipitation-chemical precipitation,whereas the reaction mechanisms of Mt/Fe0 adsorption for nitrogen involved adsorption-reduction.The result of removal nitrogen and phosphorus simultaneously using Mt/Fe0 indicated there is the competitive relation between them.These fundamental results would be important and potential for the theoretical and practical studies of Mt/Fe0 nanocomposites used for decontamination of nitrogen and phosphorus from aqueous solution.