Reductive immobilization and long-term remobilization of radioactive pertechnetate using bio-macromolecules stabilized zero valent iron nanoparticles

摘要

Reductive immobilization of radioactive pertechnetate(99TcO4^-) in simulated groundwater was studied by prepared carboxymethyl cellulose(CMC) and starch stabilized zero valent iron nanoparticles(nZVI),and long-term remobilization of reduced Tc was also evaluated under anoxic and oxic conditions.The stabilized nZVI can effectively reduce soluble 99Tc(Ⅶ) to insoluble 99 Tc(Ⅳ),and they can be easily delivered into a contaminated groundwater zone and facilitate in situ remediation.In this study,CMCstabilized nZVI showed higher reactivity than that using starch as the stabilizer.Batch experiments indicated that more than 99% of 99 Tc(Ⅶ)(CO=12 mg/mL) was reduced and removed from groundwater by CMC-stabilized nZVI with a CMC content of 0.2%(w/w) at a broad pH of 5-8.X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS) analyses further confirmed that 99Tc(Ⅶ)O4^-transformed into 99Tc(Ⅳ)O2(s).The presence of bicarbonate exhibited insignificant effect on Tc immobilization,while humic acid(HA) inhibited reaction mainly due to retardation on electron transfer and formation of Tc(IV)-HA complexes.More interesting,the immobilized Tc(Ⅳ) remained insoluble even after 120 d under anoxic condition,while only^21 % was remobilized when exposed to air.Therefore,biomacromolecules stabilized nZVI nanoparticles could be a viable alternative for in situ remediation of radioactive contamination in groundwater.