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Query: UMLS:C1832588 (PSS)
 2,979 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nanosized zerovalent iron (nZVI) is used for in situ remediation of contaminated groundwater. Polyelectrolyte surface coatings are used to inhibit nZVI aggregation and enhance mobility in the subsurface for emplacement. The fate of nZVI is of interest given the uncertainties regarding the effects of nanomaterials on the environment, and depends in part on the stability of these surface coatings against desorption and biodegradation. This study measured the rate and extent of desorption of polyelectrolyte coatings used to stabilize nZVI, including polyaspartate (PAP MW = 2.5 kg/mol and 10 kg/mol), carboxymethyl cellulose (CMC MW= 90 kg/nol and 700 kg/ mol), and polystyrene sulfonate (PSS MW = 70 kg/mol and 1000 kg/mol). The initial adsorbed mass of polyelectrolyte ranged from 0.85 to 3.71 mg/m2 depending on the type and molecular weight (MW). Polyelectrolyte adsorption was confirmed by an increase in nZVI electrophoretic mobility. In all cases, desorption of polyelectrolyte was slow, with less than 30 wt% desorbed after 4 months. The higher MW polyelectrolyte had a greater adsorbed mass and a slower desorption rate for PAP and CMC. nZVI mobility in sand columns after 8 month of desorption was similar to freshly modified nZVI, and significantly greater than unmodified nZVI aged for the same time under identical conditions. Based on these results, polyelectrolyte modified nanoparticles will remain more mobile than their unmodified counterparts even after-aging. Other factors potentially affecting the fate of coated nZVI must be evaluated, especially the potential for biodegradation of coatings.
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PMID:Fe0 nanoparticles remain mobile in porous media after aging due to slow desorption of polymeric surface modifiers. 1954 94

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.
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PMID:Adsorbed polymer and NOM limits adhesion and toxicity of nano scale zerovalent iron to E. coli. 2035 3