Removal Of NDMA And NDEA Using Nanoscale Zero-Valent Iron Supported On Granular Activated Carbon

Nitrosamines is a kind of small molecule organic compounds with nitrogen oxygen double bond structure,as water disinfection byproducts,N-nitrosamines were widely detected in the water after disinfection of chlorine,chloramines and ozone.Given the breadth presence and the strong carcinogenic of nitrosamines,Control of these substances in the environment has become one of the current hot topics at the forefront and the field of the environment.This paper introduces the research background,formation mechanism and removal process of N-nitrosamines.It proposes the use of granular activated carbon supported nano zero valent iron removal significance of nitrosamine substances.nanoscale zero-valent iron supported on granular activated carbon?nZVI/GAC?were synthesized using liquid phase reduction method.The nZVI/GAC was characterized by X-ray diffraction?XRD?,scanning electron microscope?SEM?and transmission electron microscope?TEM?.NDMA and NDEA as the research object,investigate NDMA and NDEA removal varied with different materials,the dosage of nZVI/GAC,solution p H,DO concentration,initial NDMA and NDEA concentration,and the addition of HA.Pseudo first-order and pseudo second-order kinetics equation were used to fit the data.Through the rate constant K and the initial rate constant h,to study the effect of different influence factors on the reaction rate.This research mainly to the following conclusions:?1?Through characterized by XRD,GAC and nZVI/GAC appeared the diffraction peak of nontypical active carbon between 2?=22°³0°;nZVI/GAC and nZVI appeared the diffraction peak of ?-Fe0 between 2?=43°⁴5°.Through characterized by SEM,GAC have abundant pore structure,closely and orderly distribution channel;nZVI chains,the reunion phenomenon is severe,the diameter of nZVI between 53.09 nm and 58.98 nm;Zero-valent iron nanoparticles uniform distribution in the granular activated carbon,most embedded into the surface of activated carbon,part of the zero-valent iron nanoparticles was load to the granular activated carbon pore.Through characterized by BET,the GAC and nZVI/GAC nitrogen isothermal adsorption curve is ?.GAC BET surface area decreased 44.16 m³/g,microporous area decreased 13.18 m³/g,external surface area decreased 30.98 m³/g after nZVI supported on GAC.External surface area is much lower,indicate that most nZVI supported on External surface of GAC.?2?GAC,nZVI and nZVI/GAC for NDMA removal rates are 42.3%,8.9% and 74.8% respectively;GAC,nZVI and nZVI/GAC for NDEA removal rates were 56.8%,12.4% and 89.8%,respectively.For NDMA and NDEA,nZVI/GAC removal rate higher than that of GAC and nZVI together,shows the GAC and nZVI has synergistic effect to the NDMA and NDEA removal.The process of NDMA and NDEA removal by GAC,nZVI and nZVI/GAC followed pseudo second-order kinetics model,the correlation coefficient R₂² is higher,all above 0.994,indicate that chemical adsorption mechanism of removal process is dominate.The initial rate constant h of removing NDMA and NDEA by nZVI/GAC,GAC and nZVI decrease.?3?As the dosage of nZVI/GAC increased,the concentration of NDMA and NDEA decreased,and the removal rate of NDMA and NDEA rised.The process of NDMA and NDEA removal by different dosage of nZVI/GAC followed pseudo second-order kinetics model,the correlation coefficient R₂² is higher,all above 0.996,As the dosage of nZVI/GAC increased,the initial rate constant h increased.?4?The adsorption of NDMA and NDEA by nZVI/GAC present a rising trend with the increase of initial concentration of NDMA and NDEA.The process of differenrt initial concentration of NDMA and NDEA removal by nZVI/GAC followed pseudo second-order kinetics model,the correlation coefficient R₂² is higher,all above 0.99,As the initial concentration of NDMA and NDEA increased,the initial rate constant h increased.?5?As the solution pH increased,the removal rate of NDMA and NDEA by nZVI/GAC decreased.?6?As the concentration of DO increased,the removal rate of NDMA and NDEA by nZVI/GAC decreased.The process of NDMA and NDEA removal by nZVI/GAC at different concentration of DO followed pseudo second-order kinetics model,the correlation coefficient R₂² is higher,all above 0.998.As the concentration of DO increased,the initial rate constant h decreased.?7?The removal rate of NDMA and NDEA by nZVI/GAC had greatly reduced,and the removal rate was reduced by 32.3% and 36.6% respectively after the addition of HA.The process of NDMA and NDEA removal by nZVI/GAC at the presence of HA followed pseudo second-order kinetics model.the correlation coefficient R₂² is higher,above 0.997,and the initial rate constant h decreased.