Migration Of CMC-Ni/Fe In Porous Media And Removal Of Simulated 2,4-DCP From Groundwater

Traditional treatment methods can not effectively remove 2,4-DCP in groundwater due to 2,4-DCP is a kind of organic compound with biotoxicity and non-degrade ability.The nanozero-valent iron(n ZVI)technology is considered to be one of the most promising methods for the degradation of 2,4-DCP because of its high efficiency,no secondary pollution,and little disturbance to the underground environment.However,n ZVI is easy to agglomerate and passivate,resulting in poor migration ability in the underground environment.In addition,n ZVI has poor affinity for 2,4-DCP,so it is less degradable to 2,4-DCP.The surface modification and the addition of catalytic metals can not only solve the problem of n ZVI itself effectively,but also accelerate the degrated rate for 2,4-DCP.In this experiment,carboxymethyl cellulose(CMC)and Ni were selected as the modifier and the catalytic metal,respectivily,which used to modify n ZVI(CMC-Ni/Fe).The prepared samples were characterized by SEM,XRD and FITR.The dispersion stability,migration ability and influencing factors of CMC-Ni/Fe were studied by dispersion stability experiment and column migration experiments.The reaction activity of CMC-Ni/Fe,the factors influencing the reaction activity was investigated through batch experiments.It provides theoretical basis and technical reference for the application of CMC-Ni/Fe migration and removal of 2,4-DCP in groundwater.The characterization results of SEM,XRD and FITR showed that CMC could not only reduce the particle size of n ZVI,but also prevent its agglomeration.The structure of n ZVI,Ni/Fe and CMC-Ni/Fe prepared by the liquid phase reduction method were amorphous alloy,and there is the presence of elemental iron.And the interaction between CMC and Ni/Fe was monodentate.The dispersion stability test results indicated that CMC could increase the dispersion stability of n ZVI suspension,and the larger the amount of CMC modification,the longer the dispersion stabilization time.The suspension could be dispersed and stabilized for one month without sedimentation when the CMC modification amount was 3:1.The experimental results of column migration manifested that the removal of the unmodified Ni/Fe particles is very poor,and the migration distance is very small in the 30 eyes quartz sand column.The migration of CMC-Ni/Fe tended to increase and its residual tend to reduce with increasing the amount of CMC modification in quartz sand column.The adsorption and residual amount of CMC-Ni/Fe would decrease with increasing the particle size of quartz sand.The increase of velocity could reduce the adsorption of CMC-Ni/Fe on the surface of quartz sand,improving its penetration rate and reducing its residual capacity.The acid background solution could react Fe0 to Fe2+,resulting in increasing the migration of CMC-Ni /Fe.However,the injection concentration of CMC-Ni/Fe had a little effect on its relative filtration concentration,and the addition of Ni had no effect on the relative filtration concentration of CMC-Ni/Fe.The results of batch experiments demonstated that the initial p H value of the solution,the dosage of CMC-Ni/Fe,the amount of CMC modification,and the amount of Ni all had a significant effect on the removal of 2,4-DCP.However,it was not conducive to the removal of 2,4-DCP by CMC-Ni/Fe when the p H value was less than 3.The degradation rate and removal rate of 2,4-DCP would increase with increasing the dosage of CMC-Ni/Fe.Within the initial concentration range of 2,4-DCP examined,the dechlorination effect of 2,4-DCP is less dependent on its initial concentration.CMC could endow the affinity of Ni/Fe particles to 2,4-DCP in order to increase the degradation rate and removal rate of 2,4-DCP.However,the degradation of 2,4-DCP would be blocked when the CMC modifier(The mass ratio of CMC to Fe)was 3:1.The degradation rate and removal rate of 2,4-DCP tended to increase with increasing the addition of Ni,but the reaction rate of 2,4-dcp would be reduced when the addition of Ni was 10%.In addition,the degradation pathway of 2,4-DCP had two methods: simultaneous dechlorination and progressive dechlorination.