This research investigated the long-term performance of zero-valent iron for mediating reductive dechlorination trichloroethylene (TCE). Over a 2-year period, rates TCE in columns packed with filings were measured simulated groundwaters containing either 3 mM CaSO4, 5 CaCl2, or Ca(NO3)2. At early elapsed times, reaction pseudo-first-order concentration and independent solution pH. With increasing time, deviated from behavior due to reactive site saturation increased surface passivation...

This research investigated the effectiveness of electrochemical reduction for removing trichloroethylene (TCE) and carbon tetrachloride (CT) from dilute aqueous solutions. The kinetics, reaction mechanisms, current efficiencies TCE CT were using flow-through, iron electrode reactors with amperometric measurements rates. operated over a range flow rates, pH, ionic strength, dissolved oxygen concentration, working potentials. Typical half-lives in reactor 9.4 3.7 min, respectively. addition...

The contaminant of most concern in groundwater at the Oak Ridge Y-12 Plant's Bear Creek Valley Characterization Area is soluble uranium. removal mechanism uranium from by zero-valent iron (ZVI, Fe0) was investigated. X-ray photoelectron spectroscopy (XPS, ESCA) used to determine oxidation state Fe0 or oxide surface. Product speciation and relative reaction kinetics for under aerobic anaerobic conditions with ZVI are presented. Under conditions, U6+ rapidly strongly sorbed hydrous ferric...

This study investigated the mechanisms involved in removing arsenate from drinking water supplies using zero-valent iron media. Batch experiments utilizing wires suspended anaerobic solutions were performed to determine removal rates as a function of solution concentration. Corrosion determined elapsed time Tafel analysis. The kinetics batch reactors best described by dual-rate model which was pseudo-first-order at low concentrations and approached zero-order limit high concentrations....

Permeable reactive barriers containing zerovalent iron are being increasingly employed for in situ remediation of groundwater contaminated with redox active metals and chlorinated organic compounds. This research investigated the effect chromate concentration on its removal from solution by iron. Removal rates aqueous Cr(VI) wires were measured batch experiments initial chromium concentrations ranging 100 to 10 000 μg/L. Chromate was also columns packed filings over this same range....

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDesorption of halogenated organics from model solids, sediments, and soil under unsaturated conditions. 1. IsothermsJames. Farrell Martin. ReinhardCite this: Environ. Sci. Technol. 1994, 28, 1, 53–62Publication Date (Print):January 1994Publication History Published online1 May 2002Published inissue 1 January 1994https://pubs.acs.org/doi/10.1021/es00050a009https://doi.org/10.1021/es00050a009research-articleACS PublicationsRequest reuse...

This research investigated the oxidative destruction of perfluorooctane sulfonate at boron-doped diamond film electrodes. Experiments measuring oxidation rates PFOS were performed over a range in current densities and temperatures using rotating disk electrode (RDE) reactor parallel plate flow-through reactor. The yielded sulfate, fluoride, carbon dioxide, trace levels trifluoroacetic acid. Reaction RDE zeroth order concentration. mass-transfer-limited pseudo-first-order concentration, with...

This research investigated the mechanism of perchlorate (ClO(4)(-)) formation from chlorate (ClO(3)(-)) on boron-doped diamond (BDD) film anodes by use a rotating disk electrode reactor. Rates ClO(4)(-) were determined as functions potential (2.29-2.70 V/standard hydrogen electrode, SHE) and temperature (10-40 °C). At all applied potentials ClO(3)(-) concentration 1 mM, production rates zeroth-order with respect to concentration. Experimental density functional theory (DFT) results indicate...

This research investigated the removal of perfluorooctane sulfonate (PFOS) and perfluorobutane (PFBS) from water by Filtrasorb®400 granular activated carbon (GAC) Amberlite®IRA-458 ion exchange resin. Kinetic experiments showed that time required for uptake equilibrium was ∼50 hours GAC ∼10 Sorption isotherms PFOS PFBS endothermic promoted hydrophobic effects on GAC, a combination adsorption The aqueous solubility highly dependent ionic composition solution. resin hysteretic nearly...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDesorption of halogenated organics from model solids, sediments, and soil under unsaturated conditions. 2. KineticsJames. Farrell Martin. ReinhardCite this: Environ. Sci. Technol. 1994, 28, 1, 63–72Publication Date (Print):January 1994Publication History Published online1 May 2002Published inissue 1 January 1994https://pubs.acs.org/doi/10.1021/es00050a010https://doi.org/10.1021/es00050a010research-articleACS PublicationsRequest reuse...

Understanding arsenic reactions with ferric hydroxides is important in understanding transport the environment and designing systems for removing from potable water. Many experimental studies have shown that kinetics of adsorption on biphasic, where a fraction occurs time scale seconds while full equilibrium may require weeks to attain. This research employed density functional theory modeling order understand mechanisms contributing biphasic kinetics. The reaction energies activation...

Boron-doped diamond (BDD) film electrodes were use to electrochemically destroy N-nitrosodimethylamine (NDMA) in reverse osmosis (RO) concentrates. Batch experiments conducted ito investigate the effects of dissolved organic carbon (DOC), chloride (Cl(-)), bicarbonate (HCO(3-) and hardness on rates NDMA destruction via both oxidation reduction. Experimental results showed that not affected by DOC, Cl(-), or HCO(3-) at concentrations present RO However, hydroxyl radical scavenging 100 mM...

Zerovalent iron filings have been proposed as a filter medium for removing arsenic compounds from potable water supplies. This research investigated the kinetics of arsenate removal aqueous solutions by zerovalent media. Batch experiments were performed to determine effect corrosion rate on As(V) removal. Tafel analyses used concentration in anaerobic solutions. column reactors packed with was measured over 1-year period continuous operation. Comparison freely corroding and cathodically...

This research investigated the long-term performance of zero-valent iron aggregates for reductive dechlorination trichloroethylene (TCE) and perchloroethylene (PCE). The effects elapsed time, mass transfer limitations, influent halocarbon concentration on rates were using groundwater obtained from a field site contaminated with chlorinated organic compounds. Over first 300 days operation, reaction TCE PCE gradually increased due to increasing porosity aggregates. Although there was microbial...

This study investigated the reaction mechanisms of nitrate (NO3-) with zerovalent iron (ZVI) media under conditions relevantto groundwatertreatment using permeable reactive barriers (PRB). Reaction rates NO3- freely corroding and cathodically or anodically polarized wires were measured in batch reactors. Tafel analysis electrochemical impedance spectroscopy (EIS) used to investigate reactions occurring on surfaces. Reduction by resulted near stoichiometric production NO2-, which did not...

Abstract Removal of uranium from contaminated ground water using zero valent iron is currently under evaluation at several U.S. Department Energy (DOE) facilities. Uranium removal by may occur via adsorption onto corrosion products, and reduction to less soluble valence states reactions with elemental iron. This research investigated the effects chemistry surface precipitate buildup on Batch testing was performed assess solution potential magnetite a mixed amorphous oxide. simulated products...

The mechanisms involved in reductive dechlorination of carbon tetrachloride (CT) and trichloroethylene (TCE) at iron surfaces were studied to determine if their reaction rates limited by electron transfer. Chronoamperometry chronopotentiometry analyses used the kinetics CT TCE reduction a rotating disk electrode solutions constant halocarbon concentration. Rate constants for measured as function potential over temperature range from 2 42 °C. Changes rate with apparent electron-transfer...

Metallic iron filings are commonly employed as reducing agents in permeable barriers used for remediating groundwater contaminated by chlorinated solvents. Reactions of trichloroethylene (TCE) and tetrachloroethylene (PCE) with zerovalent were investigated to determine the role atomic hydrogen their reductive dechlorination. Experiments simultaneously measuring dechlorination corrosion rates performed fractions total current going toward evolution. Corrosion determined using Tafel analysis,...

The effect of current density on dosing rates and energy requirements for iron aluminum electrodes in a bench-scale electrocoagulation (EC) reactor have been investigated. Dissolution the anodes were independent bulk solution pH values. Iron followed Faraday's law, but averaged 83% greater than those predicted by law. Chemical corrosion both anode cathode contributed to extra-faradaic dosing. A method was developed determine faradaic power consumption as function density. An equation...