W. M. Keck Laboratory, California Institute of Technology, Pasadena, California 91125, USA.
Environ Sci Technol. 2010 Jan 1;44(1):445-50. doi: 10.1021/es902651g.
Ultrasonic irradiation has been shown to effectively degrade perfluorinated chemicals (PFCs) such as perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in aqueous solution. Reduced PFC sonochemical degradation rates in organic-rich groundwater taken from beneath a landfill, however, testify to the negative kinetic effects of the organic groundwater constituents. In this study, the PFOX (X = S or A) sonochemical degradation rates in a groundwater sample with organic concentrations about 10 times lower than those in the groundwater taken from beneath a landfill are found to be 29.7% and 20.5% lower, respectively, than the rates in Milli-Q water, suggesting that inorganic groundwater constituents also negatively affect PFC sonochemical kinetics. To determine the source of the groundwater matrix effects, we evaluate the effects of various inorganic species on PFOX sonochemical kinetics. Anions over the range of 1-10 mM show Hofmeister effects on the sonochemical degradation rates of PFOX, kClO4(-) (-PFOX) > kNO3(-) (-PFOX) kCl(-) (-)PFOX > or = kMQ-PFOX > kHCO3(-) (-PFOX) kSO42(-) (-PFOX). In contrast, common cations at 5 mM have negligible effects. Initial solution pH enhances the degradation rates of PFOX at 3, but has negligible effects over the range of 4 to 11. The observed inorganic effects on sonochemical kinetics are hypothesized to be due to ions' partitioning to and interaction with the bubble-water interface. Finally, it is shown that the rate reduction in the groundwater in this study is primarily due to the presence of bicarbonate and thus can be fully rectified by pH adjustment prior to sonolysis.
超声辐射已被证明能有效地降解全氟化学品（PFCs），如全氟辛烷磺酸（PFOS）和全氟辛酸（PFOA）在水溶液中。然而，从垃圾填埋场下方采集的富含有机物的地下水的 PFC 超声降解率降低，证明了有机地下水成分的负动力学效应。在这项研究中，发现 PFOX（X = S 或 A）在有机浓度约为从垃圾填埋场下方采集的地下水低 10 倍的地下水样本中的超声降解速率分别比 Milli-Q 水中的速率低 29.7%和 20.5%，表明无机地下水成分也对 PFC 超声动力学产生负面影响。为了确定地下水基质效应的来源，我们评估了各种无机物种对 PFOX 超声动力学的影响。在 1-10 mM 范围内的阴离子对 PFOX 的超声降解速率表现出 Hofmeister 效应，kClO4(-)（-PFOX）> kNO3(-)（-PFOX）> kCl(-)（-PFOX）≥kMQ-PFOX> kHCO3(-)（-PFOX）> kSO42(-)（-PFOX）。相比之下，5 mM 的常见阳离子则几乎没有影响。初始溶液 pH 在 3 时提高了 PFOX 的降解速率，但在 4 到 11 的范围内几乎没有影响。观察到的无机对超声动力学的影响被假设是由于离子在气泡-水界面上的分配和相互作用所致。最后，研究表明，本研究中地下水的速率降低主要是由于碳酸氢盐的存在，因此在超声裂解前通过 pH 调节可以完全纠正。
