Preparation Of Lipophilic Encapsulated KMnO₄for Remediation Of TCE

In order to solve the trichloroethylene (TCE) pollution in groundwater, the encapsulated technology was used to prepare the lipophilic encapsulated particles with potassium permanganate (KMnO4) as oxidant and paraffin wax as shell. Potassium permanganate can be released gradually from the encapsulated particles through the dissolution of shell in the lipophilic TCE. The purpose of encapsulation is to decrease non-selective consumption of KMnO4and to enhance the efficiency of oxidant, so that the lipophilic encapsulated KMnO4can be applied in in-situ oxidation of TCE in groundwater effectively.Firstly, the encapsulated KMnO4was prepared by molten dispersion followed by cooling method. Its optimum preparation condition and mechanism of release in water as well as TCE solution were studied. The optimum preparation conditions of encapsulated KMnOare120rpm of stirring speed,5mL of emulsifier and3:1of mass ratio of paraffin wax and KMnO4. The characteristics of IR, XRD and SEM showed that the encapsulated KMnO4had multiple-core-shell structure with the active KMnO4as core. The release study of encapsulated KMnO4in water and TCE solution showed that it is stable in water and it start to release in TCE solution because of the solubility of paraffin wax in TCE. The release time of encapsulated KMnO4is shortened with increasing the concentration of TCE solution. The encapsulated KMnO4can be effectively applied to in-situ oxidation of high concentration of TCE pollution.Secondly, especially for the character of TCE with high concentration (6.1-153.8mg/L) in the plume, the encapsulated KMnO4used to remove TCE was studied. The removal efficiency of TCE was influenced by the dosage of Encapsulated-KMnO4, pH, and initial concentration of TCE. The result showed that the removal efficiency can reach to93.7%after12h when TCE initial concentration is102.1mg/L and the dosage of encapsulated KMnO4is0.27g. The removal efficiency can be increased with the increasing initial concentration of TCE. The encapsulated KMnO4could effectively remove TCE at pH3-9in which neutral and acidic is better. The encapsulated KMnO4could sustain release two long circle6d to remove TCE.Finally，the sand reactor was designed to simulate plume in aquifers to studythe transfer of TCE in the sand, the effect of water flow on TCE transfer andremoval efficiency of TCE with different concentration. The experiment showed thatthe concentration of TCE is increased with the increasing depth in vertical and theincreasing flow in horizontal. The mathematical model of dispersion and transportequation can be used to predict the transfer of TCE in the sand. The removalefficiency of TCE by encapsulated KMnO4is increased by increasing flow rate, asthe flow increasing10mL/min to20mL/min, the removal efficicency of TCE canbe enhanced with12.4%, and the solution of oxalate can effectively remove themanganese dioxide precipitation which comes from the reaction of KMnO4andTCE.