以微波水熱法輔助過硫酸鹽降解水中全氟辛酸

Abstract

全氟化合物因具有環境持久性、生物累積性及對人體有潛在的毒性，且其碳-氟鍵結(C-F)具高穩定性，無法藉由自然程序破壞，必須研發出有效的方法，使其降解為二氧化碳(CO2)及氟離子(F-)。本研究以全氟辛酸(perfluorooctanoic acid, PFOA)做為主要污染物，以微波水熱法加速過硫酸鹽氧化PFOA，另選擇零價鐵作為過硫酸鹽的活化劑，藉由零價鐵解離出亞鐵離子活化過硫酸鹽，同樣在微波場下反應，加速PFOA降解成最終產物。實驗在不同溫度、pH值、過硫酸鹽加藥量及零價鐵加藥量下之PFOA及全氟辛烷磺酸(perfluorooctane sulphonate, PFOS) 去除效率。實驗結果顯示，藉由微波加熱的協助可加快過硫酸鹽去除PFOA的速率，在PS/MW系統130℃下，當pH值從11降到2，PFOA去除率從0%增加到84.3%；過硫酸鹽濃度對PFOA去除的影響，以PFOA的假一階反應常數(kobs)做比較，過硫酸鹽5 mM及10 mM的kobs值分別是1mM的1.29倍及4.31倍；溫度的影響在過硫酸鹽5 mM、pH3、140℃的條件下反應1小時後，PFOA去除率超過98%；而過硫酸鹽結合零價鐵粉系統下(PS /ZVI/MW)更能提升PFOA的去除效率，比較MW、PS/MW及PS/MW/ZVI系統的反應動力常數分別為 4.0×10-3 h-1，9.7 ×10-2 h-1及2.3×102 M-1h-1(二階反應動力)。最佳條件應用於PFOS上結果顯示，於PS/ZVI/MW其在反應時間30分鐘內PFOS去除率可達75.0%，具有實際的應用性。

The perfluorinated compounds (PFCs) have the environmental persistence, bioaccumulation, and potential toxicity to humans. The PFCs has high stability that ascribed to their C-F bonds, have no known natural decomposition processes. Therefore, developing effective methods to degrade PFCs becomes F- and CO2 is important. Perfluorooctanoic acid (PFOA) is the main study pollutants of this research. With the methods of oxidizing PFCAs by using persulfate under microwave field, which increasing PFOA and perfluorooctane sulphonate (PFOS) decomposition rate. And we choose the activator as the persulfate of zero valent iron utilize it from ferrous ion, which could activate persulfate to from sulfate radicals. This study discusse the PFOA decomposition at different concentration of PS and dosage of ZVI under different temperature and pH. According to the experimental results, the PS/MW processes of degradation efficiency of the PFOA at 130℃. PFOA decomposition increased from 0% to 84.3% while pH value decreased from 11 to 2 for a half hour. The influence of persulfate concentration, the pseudo first-order rate constants (k) is 1.29 times higher at 5 mM and 4.31 times higher at 10 mM than at 1 mM. Within 1 hours, more than 98% of PFOA was decomposed at 140℃ with 5 mM persulfate. And the PS/ZVI/MW processes more effective degraded PFOA. The k value of MW, PS/MW, PS/ZVI/MW processes were 4.0×10-3 h-1, 9.7×10-2 h-1 and 2.3×102 M-1h-1(second order), respectively. The best optimum condition applies on PFOS. The result demonstrated that, more than 75.0% of PFOS was decomposed within 30 minute at PS/ZVI/MW processes.