In-situ Activation Of Persulfate By Magnetite Nanoparticles For Degradation Of 1,2-dichloroethane

A critical factor to field-scale implementation of magnetite nanoparticles(MNPs)-based groundwater remediation is the mobility of MNPs in the targeted contamination zones,and the transport behaviors of nanopartiles in various soils must be controllable.The concentration of oxidants and mass of MNPs in the system are consider as the important parameters to influence degradation of refractory organics.In order to increase the stability of MNPs the in suspensions and enhance their transport in the porous media,carboxymethyl cellulose(CMC)was used to modify MNPs.Batch experiments were conducted to investigate the stability of bare MNPs and CMC-modified MNPs in artificial groundwater(AGW).Influence of CMC on MNPs transport in the quartz sand was studied using 1-D column experiments.Increase of surface charge due to CMC modification inhibited agglomeration of MNPs and thus increased stability of MNPs in the CMC solution.Such effects also greatly promoted transport of MNPs in the quartz sand.Furthermore,Column experiments were conducted to evaluate the possibility of using persulfate(PS)oxidant to degrade 1,2-dichloroethane(DCA),with different molar ratios(PS/DCA = 1:0,2:1,5:1 and 20:1),in natural silica sand embedded with different content of magnetite(Fe3O4)nanoparticles(MNPs)(0%,1.91%and 5.44%).In the absence of Fe304,persulfate caused no degradation of DCA due to the limited hydraulic retention time(～7h).In contrast,persulfate caused an enhanced degradation of DC A in the presence of 1.91%Fe304,and the highest degradation efficiency(33.4%)was at the condition when molar ratio of PS over DCA is 5.When increase in dosage of Fe304 from 1.91%to 5.44%,DCA degradation in the absence of persulfate increased by 3 times,and by 36.7%in the presence of persulfate with a mole ratio of 20.In addition,decrease in concentration of persulfate caused no significant reduction of degradation ratio,but the dechlorination efficiency.In this study,Fe304 exhibited a superior activation performance towards persulfate for degradation of DCA,besides,consumption of persulfate and production of soluble iron were both minimal compared with FeO/PS system.These findings show great potential of MNPs in enhancing persulfate-based in situ chemical oxidation for remediation of chlorinated solvent contaminated sites.