Nanoscale zerovalent iron (NZVI) rapidly transforms many environmental contaminants to benign products and is a promising in-situ remediation agent. To be effective, NZVI should form stable dispersions in water such that it can delivered water-saturated porous media the contaminated area. Limited mobility of has been reported, however, attributed its rapid aggregation. This study uses dynamic light scattering investigate aggregation from single nanoparticles micrometer size aggregates,...

Concerns with the environmental and health risk of widely distributed, commonly used nanoparticles are increasing. Nanosize titanium dioxide (TiO2) is in air water remediation numerous products designed for direct human use consumption. Its effectiveness deactivating pollutants killing microorganisms relates to photoactivation resulting free radical activity. This property, coupled its multiple potential exposure routes, indicates that nanosize TiO2 could pose a biological targets sensitive...

Nanoscale Fe0 particles are a promising technology for in situ remediation of trichloroethene (TCE) plumes and TCE-DNAPL source areas, but the physical chemical properties controlling their reactivity not yet understood. Here, TCE reaction rates, pathways, efficiency two nanoscale measured batch reactors: synthesized from sodium borohydride reduction ferrous iron (Fe/B) commercially available (RNIP). Reactivity was determined under iron-limited (high [TCE]) excess (low conditions with...

The surfaces of nanoscale zerovalent iron (NZVI) used for groundwater remediation must be modified to mobile in the subsurface emplacement. Adsorbed polymers and surfactants can electrostatically, sterically, or electrosterically stabilize nanoparticle suspensions water, but their efficacy will depend on ionic strength cation type as well physical chemical heterogeneities aquifer material. Here, effect mobility bare, polymer-, surfactant-modified NZVI is evaluated water-saturated sand...

Rapid in situ degradation of chlorinated solvents present as nonaqueous phase liquids (NAPL) can be accomplished using reactive zerovalent nanoiron particles. Prior studies have shown that transport the subsurface is limited, and successful delivery essential for effective remediation. Here, physical properties bare modified are measured, laboratory column reactors used to compare three types surface-modified nanoiron; triblock polymer-modified, surfactant-modified, a commercially available...

The effect of particle concentration, size distribution (polydispersity) and magnetic attractive forces (Fe0 content) on agglomeration transport poly(styrene sulfonate) (PSS) modified NZVI was studied in water-saturated sand (dp = 300 μm) columns. Particle concentrations ranged from 0.03 to 6 g/L 5 mM NaCl/5 NaHCO3 at a pore water velocity 3.2 × 10−4 m/s. Three dispersions with different intrinsic distributions obtained sequential sedimentation are compared. influence attraction deposition...

Climate change is increasing the severity and length of heat waves. Heat stress limits crop productivity can make plants more sensitive to other biotic abiotic stresses. New methods for managing are needed. Herein, we have developed ∼30 nm diameter poly(acrylic acid)-block-poly(N-isopropylacrylamide) (PAA-b-PNIPAm) star polymers with varying block ratios temperature-programmed release a model antimicrobial agent (crystal violet, CV) at plant-relevant pH. Hyperspectral-Enhanced Dark field...

Reactive zero valent iron nanoparticles can degrade toxic nonaqueous phase liquids (NAPL) rapidly in contaminated groundwater to nontoxic products situ, provided they be delivered preferentially the NAPL/water (oil/water) interface. This study demonstrates ability of novel triblock copolymers modify nanoiron surface chemistry a way that both promotes their colloidal stability aqueous suspension and drives adsorption oil/water The drive is demonstrated by copolymer-modified nanoparticles, but...

The surfaces of reactive nanoscale zerovalent iron (NZVI) particles used for in situ groundwater remediation are modified with polymers or polyelectrolytes to enhance colloidal stability and mobility the subsurface. However, surface modification decreases NZVI reactivity. Here, TCE dechlorination rate reaction products measured as a function adsorbed polyelectrolyte mass three commercially available including poly(styrene sulfonate) (PSS), carboxymethyl cellulose (CMC), polyaspartate (PAP)....

A study is presented of emulsification by silica nanoparticles with poly(2-(dimethylamino)ethyl methacrylate) brushes grafted from their surfaces (SiO2−PDMAEMA) atom-transfer radical polymerization (ATRP). The were used to stabilize xylene-in-water and cyclohexane-in-water Pickering emulsions. PDMAEMA a water-soluble weak polyelectrolyte pH-dependent lower critical solution temperature (LCST). Accordingly, SiO2−PDMAEMA thermally responsive, as shown the fact that they displayed flocculation...

Combining optical reflectometry and atomic force microscopy (AFM), we have studied the effects of surfactant counterion on adsorption isotherms, kinetics, layer structure for cationic hexadecyltrimethylammonium (C16TA+) surfactants negatively charged silica surfaces. The kinetics suggest that mechanism changes at critical micelle concentration (cmc). A change in is also suggested by differences observed state interfacial self-assembly either side cmc. Above cmc, increasing binding affinity...

Nanoscale zerovalent iron (NZVI) particles are a promising technology for reducing trichloroethylene (TCE) contamination in the subsurface. Prior to injecting large quantities of nanoparticles into groundwater it is important understand what impact will have on geochemistry and indigenous microbial communities. Microbial populations not only nutrient cycling, but also contaminant remediation heavy metal immobilization. Microcosms were used determine effects NZVI addition three different...

Fully sulfonated poly(styrenesulfonate) brushes were grown from the surface of colloidal silica particles and used to prepare stable trichloroethylene-in-water heptane-in-water Pickering emulsions. These highly charged colloidally in water but could not be dispersed trichloroethylene or heptane. Both two-phase (emulsion plus neat water) three-phase separating oil phases) systems observed, with water-continuous emulsion phases all cases. Emulsion containing as much 83% (v/v) for over six...

The complexity of natural organic matter (NOM) motivates determination how specific components in a NOM mixture interact with and affect nanoparticle (NP) behavior. effects two Suwannee River fractions (separated by 100,000 g/mol ultrafiltration membrane) on gold NP aggregation are compared. weight-average molecular weight, Mw, for the unfractionated was 23,300 g/mol, determined size exclusion chromatography multiangle light scattering. comprised ~1.8 wt % >100,000 retentate (NOMr, Mw =...

A recent transmission electron microscopy (TEM) method using precession diffraction (PED) was used to obtain LiFePO4 and FePO4 phase mapping at the nanometer-scale level on a large number of particles sizes between 50 300 nm in partially charged cathode. Despite similarity two phases (the difference lattice parameters is <5%), gives clear results that have been confirmed high-resolution (HRTEM) energy-filtered microscopy/electron energy loss spectroscopy (EFTEM/EELS) experiments. The PED...

Nanosized zerovalent iron (nZVI) is used for in situ remediation of contaminated groundwater. Polyelectrolyte surface coatings are to inhibit nZVI aggregation and enhance mobility the subsurface emplacement. The fate interest given uncertainties regarding effects nanomaterials on environment, depends part stability these against desorption biodegradation. This study measured rate extent polyelectrolyte stabilize nZVI, including polyaspartate (PAP MW = 2.5 kg/mol 10 kg/mol), carboxymethyl...

Assessing the environmental transport and fate of manufactured nanoparticles (NPs) potential exposure risks requires models for predicting attachment NPs coated with organic macromolecules in porous media. The objective this study was to determine properties that control their behavior. Deposition data a variety different types anionic coatings, including natural matter (NOM)-coated latex hematite nanoparticles, poly(styrenesulfonate)-, carboxymethylcellulose-, polyaspartate-coated titanium...

Motivated by the need to understand environmental risks posed potentially biocidal engineered nanoparticles, effects of silver nanoparticle (AgNP) exposure on viability in single species Pseudomonas fluorescens biofilms were determined via dye staining methods. AgNP dispersions, containing both particles and dissolved originating from particles, negatively impacted biofilm a dose-dependent manner. No treatments (up 100 ppm AgNPs) resulted 100% loss, even though these same concentrations...

A fundamental understanding of attachment surface-coated nanoparticles (NPs) is essential to predict the distribution and potential risks NPs in environment. Column deposition studies were used examine effect surface-coating hydrophobicity on NP collector surfaces mixtures with varying ratios octadecylichlorosilane (OTS)-coated (hydrophobic) glass beads clean silica (hydrophilic) beads. Silver (AgNPs) coated organic coatings hydrophobicity, including citrate, polyvinylpyrrolidone (PVP), gum...

Challenges in predicting effects of macromolecules on nanoparticle behavior.

Iron oxide cores of 35 nm are coated with gold nanoparticles so that individual particle motion can be tracked in real time through the plasmonic response using dark field optical microscopy. Although Brownian and viscous drag forces pronounced for nanoparticles, we show magnetic manipulation is possible large gradients. The trajectories analyzed to separate contributions from different types forces. With gradients up 3000 T/m, as small 1.5 fN detected.

Polyelectrolyte coatings significantly increase the mobility of nanoscale zerovalent iron (NZVI) in saturated porous media. The effect can be attributed to improved colloidal stability NZVI suspensions, decreased adhesion soil surfaces, or a combination two effects. This research explicitly examines how control model surfaces. was coated with three different polyelectrolyte block copolymers based on poly(methacrylic acid), poly(methyl methacrylate butyl methacrylate), and...