PH緩衝鹼活化過硫酸鹽氧化1,2-二氯乙烷之探討

Abstract

Alkaline activated persulfate could generate the free radicals such as the oxidative sulfate and hydroxyl radicals, as well as the reductive superoxide radicals. Therefore, this study was to evaluate persulfate oxidation combining with alkaline pH buffer solution for the remediation of 1,2-dichloroethane (1,2-DCA) contamination. The alkaline buffer system can maintain the alkaline condition for persulfate activation and also buffer hydrogen ions released during persulfate decomposition to prevent the acidification of groundwater during in situ application. This study initially evaluated different alkaline buffer reagents (pH ~ 13) and determind the suitable alkaline buffer solution based on the results of acid titration tests and degradation of 1,2-DCA in aqueous phase with alkaline activation persulfate. The results showed that the phosphate buffer exhibited the higher buffer intensity and the faster 1,2-DCA degradation rate. Furthermore, the effect of phosphate alkaline buffer solution with different buffer intensities (i.e. different buffered pH and ionic strength) on persulfate oxidation was investigated. Based on the acid titration tests and the degradation rate constant of 1,2-DCA, it could be seen that the rapid degradation of 1,2-DCA occurred under the conditions of buffer solution pH of 8, and ionic strength of 1.0 M, and no byproducts were detected. The influence of soil on 1,2-DCA degradation was evaluated with fixed buffer pH of 8 and ionic strength of 0.1 M. In soil slurry systems, the optimal dose of persulfate (0.1663 M ( buffer pH set from initial 8 to final 4)) was conducted. 64.2% removal of 1,2-DCA (10 mg/L) was observed in 7 days of reaction, and the degradation rate constant was 5.1 × 10-3 hr-1. Additionally, the low and high concentration of 1,2-DCA (10 mg/L and 100 mg/L, respectively) were evaluated. The results indicated that the 1,2-DCA removal can reach 99.2% and 94.5% after 30 days with the degradation rate constant of 6.7 × 10-3 and 3.9 × 10-3 hr-1, respectively, and the persulfate consumption was less than 10%, and pH value still remained above 7.5. These experimental results confirmed that the alkaline buffer pH activated persulfate system provides a potential method for the treatment of contamination by 1,2-DCA.