Adsorbed Polymer and NOM Limits Adhesion and Toxicity of Nano Scale Zerovalent Iron to E. coli

TitleAdsorbed Polymer and NOM Limits Adhesion and Toxicity of Nano Scale Zerovalent Iron to E. coli
Publication TypeJournal Article
Year of Publication2010
AuthorsLi ZQ, Greden K, Alvarez PJJ, Gregory KB, Lowry GV
JournalEnvironmental Science & Technology
Volume44
Pagination3462-3467
Date PublishedMay
Type of ArticleArticle
ISBN Number0013-936X
Accession Numberhttp://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ResearchSoft&SrcApp=EndNote&DestLinkType=FullRecord&DestApp=WOS&KeyUT=000277067000044
KeywordsANTIBACTERIAL ACTIVITY, CYTOTOXICITY, DECHLORINATION, ESCHERICHIA-COLI, FULLERENE WATER SUSPENSION, NATURAL ORGANIC-MATTER, SEDIMENTATION, SILVER NANOPARTICLES, SURFACE, TCE, ZERO-VALENT IRON
Abstract

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.

URLhttp://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ResearchSoft&SrcApp=EndNote&DestLinkType=FullRecord&DestApp=WOS&KeyUT=000277067000044
Alternate JournalEnviron. Sci. Technol.