Preparation and Properties of Encapsulated Potassium Ferrate for Oxidative Remediation of Trichloroethylene Contaminated Groundwater

摘要

The oxidative degradation of chlorinated ethylenes with a metal-oxo reagent, potassium ferrate (K_2FeO_4), is investigated in this paper. The encapsulated K_2FeO_4 was prepared by a molten suspension and cooling method, with paraffin wax and K_2FeO_4 solid as the encapsulating wall and encapsulated core, respectively. The effects of three main factors, stirring time, ultrasonic time and temperature of the water bath, on the preparation of encapsulated ferrate were studied. The IR and XRD spectra showed that ferrate was stable after encapsulation. Experiments also showed that the release process of K_2FeO_4 from the encapsulated particles includes two phases: (1) the uncoated ferrate was immediately dissolved (<1min); (2) the encapsulated ferrate was sustained to release in 108 h. The release kinetics were in good agreement with the Q = kt~n model. A well-defined change in the surface morphology before and after release reaction was observed by SEM. A higher amount of stable ferrate was recovered from the encapsulated paraffin when compared to pure ferrate itself. A primary research showed that trichloroethylene (TCE) degradation could be more effective in acidic medium since above 90% of the TCE was degraded after a reaction time of 60 mins in solutions with pH = 4.0 -6.0, compared to only 60% TCE degradation after 150 mins in solutions with pH = 10.