Remediation Of Chlorinated Pollution In Groundwater By Use Of Controlled-released Potassium Permanganate

The encapsulation technology is used to develop controlled-released KMnO4,a high effective oxidant, to remove TCE in the contaminated groundwater. Thecontrolled-released KMnO4will be applied in remediation of the groundwaterTCE potentially.Firstly, the controlled-released KMnO4encapsulation was prepared by oilphase separation method with stearic acid as shell and KMnO4solid as core, andthen the encapsulation mechanism, as well as release process is studied. Theencapsulation ratio can up to135%under the optimum preparation conditionswhich are70-80oC of water bath temperature,10mins of ultrasonic time,3:1ofthe ratio of shell to core,1:3of the ratio of PEG4000to shell and350r/min ofstirring speed. The release kinetics of encapsulated KMnO4particles was ingood agreement with Q=0.352*t0.6112(R2=0.967) model and the theoreticaltime of the encapsulated KMnO4to release permanganate into water continuallywere430.5d under the optimum preparation conditions. But in TCE solution,stearic acid, the shell of controlled-released KMnO4,could be dissolved b y TCE,which accelerate the release rate of KMnO4, and the effective transmission ofKMnO4to TCE contaminant would be realized. The IR spectra showed thatstearic acid bonded chemically with the surface of KMnO4, rather than adsorbedit physically.Secondly, the controlled-released KMnO4used for TCE removal in batchexperiments and the effect of different controlling factors on the removalefficiency of TCE were evaluated. The experiments results show thatencapsulation could reduce oxidant losses from the non-selective oxidation, thusimprove the oxidant efficiency and decrease the amount of oxidant needed.When pH value was2.90-10.4, the removal of TCE always met sewage drainagestandard of Grade III after12h reaction, which showed that controlled-releasedKMnO4can be used to control the TCE pollution in groundwater with differentpH level. The release mechanism of encapsulated KMnO4in water and TCEsolution showed that the release of KMnO4is through the small pores on the surface of controlled-released KMnO4into water and the release into TCE is dueto the adsorption of TCE to shell firstly, and then the dissolution of the shell,finally the release of KMnO4. TCE could be dechlorinated completely after theoxidation with enough dosage of controlled-released KMnO4.Finally, the pilot study with sand column was designed to simulate TCEpollution in groundwater environment with3series controlled-releasedoxidation. The efficiency and mechanism of TCE removal by controlled-releasedtechnology were studied. The study showed that the removal efficiency of TCEin sand column b y3series controlled-released oxidation could meet sewagedrainage standard of Grade III in16days. Compared to the use of KMnO4solution, the encapsulated KMnO4can be used more effectively because of itscontrolled-release. The oxalic acid solution can be pumped into column toremove MnO2effectively, which comes from the reaction of KMnO4and TCE.