A Study On The Degradation Of Trichloroethylene In Groundwater By Chitosan Coated Fe/ni Bimetal Nanoparticles

Trichloroethylene(TCE)poses a serious threat to the public health and environmental safety.In-situ injection of nano zero-valent iron(n ZVI)can be used to degrade TCE in groundwater.However in application,n ZVI is easy to be oxidized and aggregated,resulting in loss of reactivity and poor mobility.Accordingly in the present study,we used the natural polymer chitosan as a coating agent to increase the dispersion and stability,and loaded nickel as a catalyst to enhance the reactivity.A chitosan-coated nano-iron-nickel bimetallic particle(CS-Fe-Ni)was successfully prepared.The results obtained from this study provided the theoretical and experimental basis for the application of n ZVI in-situ remediation technology.The main results are as follows:1)CS-Fe-Ni was prepared by liquid-phase reduction method and fully characterized.SEM images showed that CS-Fe-Ni is spherical and chain-like and spatially tightly bound.XRD pattern analysis confirmed the existence of Fe0.XPS analysis showed that iron on the material surface contains Fe(0),Fe(II)and Fe(III).FTIR spectra showed that chitosan is coated on the surface of n ZVI.2)The dispersion stability of CS-Fe-Ni was assessed using sedimentation spectra curve and dynamic light scattering(DLS)measurements.The decrease in the absorbance of CS-Fe-Ni sedimentation spectrum became slow,indicating that the dispersion stability of n ZVI is enhanced after coating chitosan.DLS data showed that CS-Fe-Ni agglomerates have smaller particle sizes.Zeta potential analysis demonstrated the electrostatic repulsion between nanoparticles and the dispersion stability of CS-Fe-Ni are significantly enhanced.The column experiments confirmed that the mobility of modified CS-Fe-Ni was improved as well.3)The degradation rate of TCE is proportional to the dosage of CS-Fe-Ni in a certain range,and is not much affected in the presence of natural organic matter.The degradation of TCE in groundwater by CS-Fe-Ni is very fast,indicating that CS-Fe-Ni is a kind of preferred n ZVI for application.4)The Fe0 content in CS-Fe-Ni was measured according to the H2 generation method,demonstrating that the coated chitosan can enhance its antioxidant capacity.The mechanism of reductive dechlorination of TCE was addressed,and it further confirmed that CS-Fe-Ni could dechlorinate TCE completely.