Civil & Environmental Engineering, Center for Environmental Implications of Nanotechnology, and Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213-3890, USA.
Environ Sci Technol. 2010 May 1;44(9):3462-7. doi: 10.1021/es9031198.
Nanoscale zerovalent iron (NZVI) is used for groundwater remediation. Freshly synthesized bare, i.e. uncoated NZVI is bactericidal at low mg/L concentration, but the impact of surface modifiers and aging (partial oxidation) on its bactericidal properties have not been determined. Here we assess the effect that adsorbed synthetic polymers and natural organic matter (NOM) and aging (partial oxidation) have on the bactericidal properties of NZVI to the gram-negative bacterium, Escherichia coli. Exposure to 100 mg/L of bare NZVI with 28% Fe(0) content resulted in a 2.2-log inactivation after 10 min and a 5.2-log inactivation after 60 min. Adsorbed poly(styrene sulfonate) (PSS), poly(aspartate) (PAP), or NOM on NZVI with the same Fe(0) content significantly decreased its toxicity, causing less than 0.2-log inactivation after 60 min. TEM images and heteroaggregation studies indicate that bare NZVI adheres significantly to cells and that the adsorbed polyelectrolyte or NOM prevents adhesion, thereby decreasing NZVI toxicity. The 1.8-log inactivation observed for bare NZVI with 7% Fe(0) content was lower than the 5.2-log inactivation using NZVI with 28% Fe(0) after 1 h; however, the minimum inhibitory concentration (MIC) after 24 h was 5 mg/L regardless of Fe(0) content. The MIC of PSS, PAP, and NOM coated NZVI were much higher: 500 mg/L, 100 mg/L, and 100 mg/L, respectively. But the MIC was much lower than the typical injection concentration used in remediation (10 g/L). Complete oxidation of Fe(0) in NZVI under aerobic conditions eliminated its bactericidal effects. This study indicates that polyelectrolyte coatings and NOM will mitigate the toxicity of NZVI for exposure concentrations below 0.1 to 0.5 g/L depending on the coating and that aged NZVI without Fe(0) is relatively benign to bacteria.
纳米零价铁（NZVI）用于地下水修复。新合成的裸露的，即未涂层的 NZVI 在低毫克/升浓度下具有杀菌作用，但表面改性剂和老化（部分氧化）对其杀菌性能的影响尚未确定。在这里，我们评估了吸附合成聚合物和天然有机物（NOM）以及老化（部分氧化）对革兰氏阴性菌大肠杆菌的 NZVI 杀菌特性的影响。暴露于 100mg/L 的具有 28%Fe(0)含量的裸露 NZVI 在 10 分钟后导致 2.2-log 的失活，在 60 分钟后导致 5.2-log 的失活。具有相同 Fe(0)含量的吸附聚苯乙烯磺酸钠（PSS）、聚天冬氨酸（PAP）或 NOM 的 NZVI 显着降低了其毒性，在 60 分钟后导致小于 0.2-log 的失活。TEM 图像和异质聚集研究表明，裸露的 NZVI 显着附着在细胞上，吸附的聚电解质或 NOM 阻止了附着，从而降低了 NZVI 的毒性。对于具有 7%Fe(0)含量的裸露 NZVI，观察到的 1.8-log 失活低于在 1 小时后使用具有 28%Fe(0)含量的 NZVI 的 5.2-log 失活；然而，无论 Fe(0)含量如何，24 小时后的最小抑菌浓度（MIC）均为 5mg/L。PSS、PAP 和 NOM 涂层 NZVI 的 MIC 要高得多：分别为 500mg/L、100mg/L 和 100mg/L。但 MIC 远低于修复中使用的典型注射浓度（10g/L）。在有氧条件下，NZVI 中 Fe(0)的完全氧化消除了其杀菌作用。这项研究表明，聚电解质涂层和 NOM 将减轻 NZVI 在暴露浓度低于 0.1 至 0.5g/L 时的毒性，具体取决于涂层，而没有 Fe(0)的老化 NZVI 对细菌相对无害。
