Air Stripping And Chemical Oxidation Techniques For 1,1,1-Trichloroethane Treatment From Groundwater

Groundwater contamination by chlorinated solvents is a worldwide problem and various remediation techniques need to be developed. In this study, three kinds of processes based on persulfate oxidation were investigated for the treatment of 1,1,1-trichloroethane (1,1,1-TCA, hereafter refer to as TCA for short) contaminated groundwater. In the experiments of air stripping/activated carbon (AC) adsorption and AC regeneration, the results showed that air stripping was more effective for TCA release from the aqueous phase to the gas phase than single process of temperature elevating and more than 99% of TCA in aqueous phase could be removed in 10 min. TCA in the exhaust gas from the stripper could be completely adsorbed by coconut AC, which showed the best adsorption performance compared to fruit shell AC, coal AC and coal bar AC. Activated carbon catalysis persulfate (PS) was efficient for TCA degradation. SO42- was posed to be an adverse factor in our study. We applied two kinds of PS dosing methods, and found that PS adding in the solution in three times averagely could enhance TCA degradation significantly and the removal rate was up to 91.45%. Oxidation processes resulted in less contribution of adsorption and increased solution acidity. Three kinds of radical quencher species were studied to valid the radical reaction mechanism; and phenol could inhibit the performance of TCA removal remarkablely. Concerning destruction of TCA,16.56% Cl- generated in the reaction. Finally, the reuse of AC was studied and the performance for TCA degradation was still good after using for three times. Ultrasound combined with PS could shorten the reaction time for TCA removal greatly, which was economy in energy consuming; the water matrices did not show significant influences on the performances of ultrasound combined with PS and good performances on various groundwater with different contaminantion level were obtained. However, in our research, utilization rate of PS is not high, suggested further researches should be done to improve the utilization rate.