摘要
Microwave-hydrothermal treatment of persis- tent and bioaccumulative perfluorooctanoic acid （PFOA） in water with persulfate （S2O2-） has been found effective. However, applications of this process to effectively remediate PFOA pollution require a better understanding on free-radical scavenging reactions that also take place. The objectives of this study were to investigate the effects ofpH （pH= 2.5, 6.6, 8.8, and 10.5）, chloride concentra- tions （0.01-0.15 mol.L-1）, and temperature （60℃, 90℃, and 130℃） on persulfate oxidation of PFOA under microwave irradiation. Maximum PFOA degradation occurred at pH 2.5, while little or no degradation at pH 10.5. Lowering system pH resulted in an increase in PFOA degradation rate. Both high pH and chloride concentrations would result in more scavenging of sulfate free radicals and slow down PFOA degradation. When chloride concentrations were less than 0.04 mol.L^-1 at 90℃ and 0.06mol.L^-1 at 60℃, presence of chloride ions had insignificant impacts on PFOA degradation. However, beyond these concentration levels, PFOA degradation rates reduced significantly with an increase in chloride concentrations, especially under the higher temperature.
Microwave-hydrothermal treatment of persis- tent and bioaccumulative perfluorooctanoic acid （PFOA） in water with persulfate （S2O2-） has been found effective. However, applications of this process to effectively remediate PFOA pollution require a better understanding on free-radical scavenging reactions that also take place. The objectives of this study were to investigate the effects ofpH （pH= 2.5, 6.6, 8.8, and 10.5）, chloride concentra- tions （0.01-0.15 mol.L-1）, and temperature （60℃, 90℃, and 130℃） on persulfate oxidation of PFOA under microwave irradiation. Maximum PFOA degradation occurred at pH 2.5, while little or no degradation at pH 10.5. Lowering system pH resulted in an increase in PFOA degradation rate. Both high pH and chloride concentrations would result in more scavenging of sulfate free radicals and slow down PFOA degradation. When chloride concentrations were less than 0.04 mol.L^-1 at 90℃ and 0.06mol.L^-1 at 60℃, presence of chloride ions had insignificant impacts on PFOA degradation. However, beyond these concentration levels, PFOA degradation rates reduced significantly with an increase in chloride concentrations, especially under the higher temperature.
