Paul Tratnyek

Oregon Health & Science University | OHSU · OHSU-PSU School of Public Health

The treatment of ballast water carried onboard ships is critical to reduce the spread of nonindigenous aquatic organisms that potentially include noxious and harmful taxa. We tested the efficacy of persulfate (peroxydisulfate, S2O8(2-), PS) activated with zero-valent iron (Fe(0)) as a chemical biocide against two taxa of marine phytoplankton grown...

The oxide layer that lies at the iron-water interface under environmental conditions can influence the redn. of solutes by acting as a passive film, semiconductor, or coordinating surface. As a passive film, oxides may inhibit reaction by providing a phys. barrier between the underlying metal and dissolved oxidants. Sustained redn. of solutes requi...

A review. Many redox reactions of importance in aquatic chem. involve elementary steps that occur by single-electron transfer (SET). This step is often the first and rate limiting step in redox reactions of environmental contaminants, so there has been a great deal of interest in the corresponding one-electron redn. potentials (E1). Although E1 can...

The fate of nano zero-valent iron (nZVI) during subsurface injection was examined using carboxymethylcellulose (CMC) stabilized nZVI in a very large three-dimensional physical model aquifer with detailed monitoring using multiple, complementary detection methods. A fluorescein tracer test in the aquifer plus laboratory column data suggested that th...

The reactivity of zerovalent zinc (ZVZ) toward 1,2,3-trichloropropane (TCP) was evaluated under a variety of solution conditions, including deionized water, groundwater, and artificial groundwater, over a pH range of about 6.5-12. In deionized water, first-order rate constants for TCP disappearance (k(obs)) exhibit a broad minimum between pH 8 and...

Groundwater contamination by 1,2,3-trichloropropane (TCP) poses a unique challenge due to its human toxicity and recalcitrance to degradation. Previous work suggests that nitrogenous functional groups of pyrogenic carbonaceous matter (PCM), such as biochar, are important in accelerating contaminant dechlorination by sulfide. However, the reaction m...

This study investigated the reaction pathway of 2,4-dinitroanisole (DNAN) on the pyrogenic carbonaceous matter (PCM) to assess the scope and mechanism of PCM-facilitated surface hydrolysis. DNAN degradation was observed at pH 11.5 and 25 °C with a model PCM, graphite, whereas no significant decay occurred without graphite. Experiments were performe...

To successfully understand and model the environmental fate of per- and polyfluoroalkyl substances (PFAS), it is necessary to know key physicochemical properties (PChPs) such as pKa; however, measured PChPs of PFAS are scarce and of uncertain reliability. In this study, quantitative structure-activity relationships (QSARs) were developed by correla...

Perfluoroalkyl carboxylic and sulfonic acids (PFCAs and PFSAs) have low pKa 's and are, therefore, deprotonated under most experimental and environmental conditions. Hence, the anionic species dominate their partitioning between water and organic phases, including, octanol and phospholipid bilayers which are often used as model systems for environm...

Chloroform (CF) is a widely used chemical reagent and disinfectant and a probable human carcinogen. The extensive literature on halocarbon reduction with zerovalent iron (ZVI) shows that transformation of CF is slow, even with nano, bimetallic, sulfidated, and other modified forms of ZVI. In this study, an alternative method of ZVI modification─inv...

Measured and fitted data from square-wave voltammetry (SWV) in DMSO for electron exchange capacities (EECs) of pyrogenic natural organic matter (pyDOM) and natural organic matter (NOM) standards. From Cao, H., A. S. Pavitt, J. M. Hudson, P. G. Tratnyek, and W. Xu. 2023. Electron exchange capacity of pyrogenic dissolved organic matter (DOM): Compl...

Pyrogenic dissolved organic matter (pyDOM) is derived from black carbon, which is important in the global carbon cycle and other biogeochemical redox processes. The electron-exchange capacity (EEC) of pyDOM has been characterized in water using mediated chronoamperometry (MCA), which gives precise results under specific operational conditions, but...

Many challenges remain before we can fully understand the multifaceted role that natural organic matter (NOM) plays in soil and aquatic systems. These challenges remain despite the considerable progress that has been made in understanding NOM’s properties and reactivity using the latest analytical techniques. For nearly 4 decades, the International...

Hydrolysis is a common transformation reaction that can affect the environmental fate of many organic compounds. In this study, three proposed mechanisms of alkaline hydrolysis of 2,4,6-trinitrotoluene (TNT) and 2,4-dinitroaniline (DNAN) were investigated with plane-wave density functional theory (DFT) combined with ab initio and classical molecula...

Iron (Fe) is the fourth most abundant element in the earth's crust and plays important roles in both biological and chemical processes. The redox reactivity of various Fe(II) forms has gained increasing attention over recent decades in the areas of (bio) geochemistry, environmental chemistry and engineering, and material sciences. The goal of this...

Metal(loid) oxyanions in groundwater, surface water, and wastewater can have harmful effects on human or ecological health due to their high toxicity, mobility, and lack of degradation. In recent years, the removal of metal(loid) oxyanions using zerovalent iron (ZVI) has been the subject of many studies, but the full scope of this literature has no...

Zero valent iron (ZVI) applications to remediation of shallow groundwaters can be affected by dissolved oxygen (DO) and organic ligands. To explore the intersection between these complicating factors, this study thoroughly characterized the reactions of nitrobenzene (NB) with ZVI in the presence DO and the model ligand ethylene diamine tetraacetic...

FeN X in Fe single-atom catalysts can be the active site for adsorption and activation of reactants. In addition, FeN X species have been shown to facilitate electron transfer between Fe and the carbon supports used in newly developed metal-air batteries. We hypothesized that the combination of FeN X species with granular zero-valent iron (ZVI) mig...

Due to the increasing diversity of organic contaminants discharged into anoxic water environments, reactivity prediction is necessary for chemical persistence evaluation for water treatment and risk assessment purposes. Almost all quantitative structure activity relationships (QSARs) that describe rates of contaminant transformation apply only to n...

Over the last few decades, significant progress has been made in the development and use of electronic structure and other molecular simulation methods. As these methods become more mature and are able to perform larger and more complex chemical simulations, the need for improvement in scientific visualization, molecular builders, simplified input...

Sulfidation can enhance both the reactivity and selectivity (i.e., electron efficiency, εe) of zero-valent iron (ZVI) in contaminant removal, which may make this technology cost-effective for a wider range of water treatment applications. However, current sulfidation methods involve either hazardous or unstable sulfidation agents (e.g., Na2S, Na2S2...

Organic ligands can alter the redox behavior of metal species through the generation of metal-ligand complexes. Photo-induced complexation between ligands and metals is an important, but under-appreciated, aspect of process. Acetylacetone (AA) is a good chelating agent due to keto-enol tautomerization. In the presence of AA, photoreduction of Cr(VI...

Guest editors Elizabeth Edwards, Lucy Carpenter, Sarah Blossom and Paul Tratnyek introduce the Halogenated (semi)volatile organic compounds themed issue of Environmental Science: Processes & Impacts .

The efficiency and selectivity of zerovalent iron-based treatments for organohalide contaminated groundwater can be quantified by accounting for redistribution of electrons derived from oxidation of Fe⁰. Several types of efficiency are reviewed, including (i) the efficiency of Fe(0) utilization, εFe(0), (ii) the electron efficiency of target contam...

The characteristic pathway for degradation of halogenated aliphatic compounds in groundwater or other environments with relatively anoxic and/or reducing conditions is reductive dechlorination. For 1,2-dichalocarbons, reductive dechlorination can included hydrogenolysis and dehydrohalogenation, the relative significance of which depends on various...

Abiotic reduction of contaminants in iron-based laboratory model systems has been studied extensively, but the resulting understanding is not sufficient to allow prediction of reaction rates under field conditions. This study demonstrates that rates of contaminant reduction by aquifer sediments can be predicted by combining several recent methodolo...

The complex and indeterminant composition of NOM makes characterization of its redox properties challenging. Approaches that have been taken to address this challenge include chemical probe reactions, potentiometric titrations, chronocoulometry,...

Quinones are important electron shuttles as well as micropollutants in the nature. Acetylacetone (AA) is a newly recognized electron shuttle in aqueous media exposed to UV irradiated. Herein, we studied the interactions between AA and hydroquinone (QH2) under steady-state and transient photochemical conditions to clarify the possible reactions and...

Competition among oxidizing species in groundwater and wastewater for the reductive capacity of zerovalent iron (ZVI) makes the selectivity of ZVI for target contaminant degradation over other reduction pathways a major determinant of the feasibility of ZVI-based water treatment processes. The selectivity for reduction of contaminants over water is...

Carbon materials are promising supports for heterogeneous catalysis compared to oxide supports, such as titania, alumina, mesoporous silica, and hydrotalcite, because of their stability and relative chemical inertness. Additionally, the unique surface structures of carbon supports help control the growth, aggregation, and uniformity of the catalyti...

The mixed and variable valence of iron in magnetite (Fe(III)tet[Fe(II),Fe(III)]octO42− ) give this mineral unique properties that make it an important participant in redox reactions in environmental systems. However, the variability in its stoichiometry and other physical properties complicates the determination of its effective redox potential. To...

Indexed extended abstracts from the first symposium devoted to the science and engineering of contaminant remediation with zero-valent metals, which took place as part of the 209th National Meeting of the American Chemical Society, Anaheim, California, USA (2-7 April 1995). In 1995, this booklet was prepared by excerpting the extended abstracts for...

Adding Au to Pd nanoparticles (NPs) can impart high catalytic activity with respect to hydrogenation of a wide range of substances. These materials are often synthesized by reducing metallic precursors; hence, sonochemical and solvothermal processes are commonly used to anchor these bimetals onto thin supports, including graphene. Although similar...

Research efforts on advanced oxidation processes (AOPs) have long been focused on the fundamental chemistry of activation processes and free radical reactions. Little attention has been paid to the chemistry of the precursor oxidants. Herein, we found that the precursor oxidants could lead to quite different outcomes. A counterintuitive result was...

Raw hydrogen concentration vs. time data from Qin, H., X. Guan, J. Z. Bandstra, R. L. Johnson, and P. G. Tratnyek (2018) “Modeling the kinetics of hydrogen formation by zerovalent iron: Effects of sulfidation on micro- and nano-scale particles” Environ. Sci. Technol. 52(23): 13887-13896. [10.1021/acs.est.8b04436] This manuscript reports a large se...

The hydrogen evolution reaction (HER) that generates H2 from the reduction of H2O by Fe0 is among the most fundamental of the processes that control reactivity in environmental systems containing zerovalent iron (ZVI). To develop a comprehensive kinetic model for this process, a large and high-resolution data set for HER was measured using five typ...

This document is a summary report of a SERDP and ESTCP sponsored strategic workshop to address issues associated with chlorinated solvents in groundwater. The goal of the workshop was to identify research, demonstration, and technology transfer needs that should be addressed over the next five years.

The optimization of nanoscale zero-valent iron (nZVI) for groundwater remediation applications requires consideration of properties that influence its longevity and transport in porous media and reactivity with contaminants. Here, we report on the stabilization of nZVI by controlled growth of oxide shells of varying thickness and characterization o...

Effect of Synthesis Time of Carbon Supported Pd/Au NPs on TCE degradation - Volume 24 Supplement - Candice Stauffer, Kavita Meduri, Graham O'Brien Johnson, Paul G. Tratnyek, Jun Jiao

Electron Microscopy Characterization of the Synergistic Effects between Pd, Au NPs, and Their Graphene Support - Volume 24 Supplement - Kavita Meduri, Candice Stauffer, Graham O'Brien Johnson, Paul G. Tratnyek, Jun Jiao

Palladium (Pd) and gold (Au) nanoparticles (NPs) hybridized on two types of carbon supports, graphene and granular activated carbon (GAC), were shown to be promising catalysts for the sustainable hydrodehalogenation of aqueous trichloroethylene (TCE). These catalysts are capable of degrading TCE more rapidly than commercial Pd-on-GAC catalysts. The...

Associate Editor Paul Tratnyek and Guest Editor Joe Needoba introduce the Environmental Science: Processes & Impacts Planetary Health collection.

Technetium (Tc) contamination remains a major environmental problem at nuclear reprocessing sites, e.g., the Hanford Site, Washington State, USA. At these site, Tc is present in liquid waste destined for immobilization in a waste form or has been released into the subsurface environment. The high environmental risk associated with Tc is due to its...

Recent research on contaminant removal by zerovalent iron (ZVI) has evolved from investigating simple model systems to systems that encompass increased dimensions of complexity. Sulfidation and aerobic conditions are two of the most broadly relevant complications. Combining these two, this study investigated the dynamic interactions between sulfida...

Zerovalent iron (ZVI) is commonly used for water treatment under aerobic conditions such as sequestration of metals. Sulfide-modified ZVI (S-ZVI) is attracting increasing attention for its easy preparation and high reactivity with environmental pollutants. The processes responsible for contaminant removal can be a complex mixture of redox, sorption...

Iron-based materials used in water treatment and groundwater remediation—especially micro- and nano-sized zerovalent iron (nZVI)—can be more effective when modified with lower-valent forms of sulfur (i.e., “sulfidated”). Controlled sulfidation for this purpose (using sulfide, dithionite, etc.) is the main topic of this review, but insights are deri...

In water treatment processes that involve contaminant reduction by zero-valent iron (ZVI), reduction of water to dihydrogen is a competing reaction that must be minimized to maximize the efficiency of electron utilization from the ZVI. Sulfidation has recently been shown to decrease H2 formation significantly, such that the overall electron efficie...

Accessible versions of selected figures from Tratnyek et al. (2017) "In silico environmental chemical science: Properties and processes from statistical and computational modelling" Environ. Sci. Processes Impacts 19(3): 188-202. DOI: 10.1039/C7EM00053G. The Abstract Art figure shows a classification of variables for predictive/diagnostic models u...

Effect of Synthesis Temperature on the Formation of GAC supported Pd and Au NPs - Volume 23 Issue S1 - Kavita Meduri, Candice Stauffer, Thomas Lindner, Graham O’Brien Johnson, Paul G. Tratnyek, Jun Jiao

Magnetite (Fe 3 O 4 ) is a naturally occurring iron oxide found throughout the Earth’s crust. Due to the mixed valence state of the iron in magnetite (in stoichiometric magnetite the Fe ²⁺ :Fe ³⁺ ratio is 1:2, or x = 0.5) it is one of the more redox active minerals in the environment. Magnetite can influence the fate of contaminants, both as a part...

Guest editors Kathrin Fenner and Paul Tratnyek introduce the themed issue on “QSARs and computational chemistry methods in environmental chemical sciences” of Environmental Science: Processes & Impacts .

Quantitative structure-activity relationships (QSARs) have long been used in the environmental sciences. More recently, molecular modeling and chemoinformatic methods have become widespread. These methods have the potential to expand and accelerate advances in environmental chemistry because they complement observational and experimental data with...

Phenols and anilines have been studied extensively as reductants of environmental oxidants (such as manganese dioxide) and as reductates (e.g., model contaminants) that are transformed by environmental oxidants (ozone, triple organic matter, etc.). The thermodynamics and kinetics of these reactions have been interpreted using oxidation potentials f...

Applications of zerovalent iron (ZVI) for water treatment under aerobic conditions include sequestration of metals (e.g., in acid mine drainage) and decolorization of dyes (in wastewaters from textile manufacturing). The processes responsible for contaminant removal can be a complex mixture of reduction, oxidation, sorption, and co-precipitation pr...

Nano zerovalent iron (nZVI) is a promising remediation technology utilizing in situ chemical reduction (ISCR) to clean up contaminated groundwater at hazardous waste sites. The small particle size and large surface area of nZVI result in high reactivity and rapid destruction of contaminants. Over the past 20 years, a great deal of research has adva...

The high reactivity of nano zerovalent iron (nZVI) leads to inefficient treatment due to competition with various natural reductant demand (NRD) processes, especially the reduction of water to hydrogen. Here we show that this limitation can be alleviated by sulfidation (i.e., modification by reducing sulfur compounds). nZVI synthesized on carboxylm...

div class="title">Characterization of Palladium and Gold Nanoparticles on Granular Activated Carbon as an Efficient Catalyst for Hydrodechlorination of Trichloroethylene - Volume 22 Issue S3 - Kavita Meduri, Andrew Barnum, Graham O’Brien Johnson, Paul G. Tratnyek, Jun Jiao

New energetic compounds are designed to minimize their potential environmental impacts, which includes their transformation and the fate/effects of their transformation products. The nitro groups of energetic compounds are readily reduced to amines and the resulting aromatic amines are subject to oxidation and coupling reactions. Manganese dioxide...

A variety of electrochemical methods have been used to characterize the redox properties of minerals, but few have used mineral particles (as found in the natural environment) and even fewer have used electrochemical impedance spectroscopy (EIS). We have developed protocols for forming mineral particles into packed powder electrodes (PDEs), using a...

Increasing recognition that abiotic natural attenuation (NA) of chlorinated solvents can be important has created demand for improved methods to characterize the redox properties of the aquifer materials that are responsible for abiotic NA. This study explores one promising approach: using chemical reactivity probes (CRPs) to characterize the therm...

Many oxyanion-forming metals (As, Sb, Se, Tc, etc.) can be removed from water by adsorption and/or redox reactions involving iron oxides, including the oxides associated with zerovalent iron (ZVI). The rate of antimonite (Sb(III) hydrolysis species) removal by ZVI was determined in open, well-mixed batch reactors as a function of experimental facto...

MnO4(-) was activated by HSO3(-), resulting in a process that oxidizes organic contaminants at extraordinarily high rates. The permanganate/bisulfite (PM/BS) process oxidized phenol, ciprofloxacin, and methyl blue at pHini 5.0 with rates (kobs ≈ 60-150 s(-1)) that were 5-6 orders of magnitude faster than those measured for permanganate alone, and ∼...

Nano zerovalent iron synthesized with carboxymethylcelluose (CMC-nZVI) is among the leading formulations of nZVI currently used for in-situ groundwater remediation. The main advantage of CMC-nZVI is that it forms stable suspensions, which are relatively mobile in porous media. Rapid contaminant reduction by CMC-nZVI is well documented, but the fate...

The emplacement of nano zerovalent iron (nZVI) for groundwater remediation is usually monitored by common measurements such as pH, total iron content, and oxidation-reduction potential (ORP) by potentiometry. However, the interpretation of such measurements can be misleading because of the complex interactions between the target materials (e.g., su...

The evaluation of new energetic nitroaromatic compounds (NACs) for use in green munitions formulations requires models that can predict their environmental fate. Previously invoked linear free energy relationships (LFER) relating the log of the rate constant for this reaction (log(k)) and one-electron reduction potentials for the NAC (E1NAC) normal...

Environmentally relevant abiotic reductants—such as zerovalent iron (ZVI) and divalent iron (DVI) containing minerals—react predominantly by electron-transfer mechanisms with variety of contaminant and probe compounds. Other reduction mechanisms involving activated forms of hydrogen (Hads, or H−) have been suggested, but most evidence for these is...

Our previous study has shown that formation of TcS2-like phase is favored over TcO2 under sulfidic conditions stimulated by nano zerovalent iron. This study further investigates the stability of Tc(IV) sulfide upon reoxidation by solution chemistry, solid phase characterization, and X-ray absorption spectroscopy. Tc dissolution data showed that Tc(...

The sequestration of Se(IV) by zero-valent iron (ZVI) is strongly influenced by the coupled effects of aging ZVI and presence of a weak magnetic field (WMF). ZVI aged at pH 6.0 with MES as buffer between 6 and 60 hours gives nearly constant rates of Se(IV) removal with WMF, but with rate constants that are 10- to 100-fold greater than without. XANE...

Nano zerovalent iron (nZVI) formed under sulfidic conditions results in a biphasic material (Fe/FeS) that reduces trichloroethene (TCE) more rapidly than nZVI associated only with iron oxides (Fe/FeO). Exposing Fe/FeS to dissolved metals (Pd2+, Cu2+, Ni2+, Co2+, and Mn2+) results in their sequestration by coprecipitation as dopants into FeS and FeO...

In situ chemical reduction (ISCR) is a general term for a suite of in situ groundwater remediation technologies that rely primarily on chemical reduction of contaminants. ISCR has been used for over 15 years for plume treatment, but its use for source treatment is more recent. This chapter provides the first integrated assessment of the entire suit...

This chapter provides an overview of synthesis, characterization and property measurements techniques important for making understanding the nature of zero valent iron nanoparticles. The chemical reactivity of nanometer-sized materials can be quite different from that of either bulk forms of a material or the individual atoms and molecules that com...

The reactivity of FeS-coated iron nanoparticles (nFe/FeS) toward trichloroethylene (TCE) reduction was examined in both synthetic and real groundwater matrices to evaluate the potential performance of nFe/FeS in field treatment. The rate of TCE reduction increased with increasing pH, which is consistent with the pH effect reported previously for ir...

Under anoxic conditions, soluble 99TcO4- can be reduced to less soluble TcO2•nH2O, but the oxide is highly susceptible to reoxidation. Here we investigate an alternative strategy for remediation of Tc-contaminated groundwater whereby sequestration as Tc sulfide is favored by sulfidic conditions stimulated by nano zero-valent iron (nZVI). nZVI was p...

The environmental impacts of energetic compounds can be minimized through the design and selection of new energetic materials with favorable fate properties. Building predictive models to inform this process, however, is difficult because of uncertainties and complexities in in the major fate-determining transformation reactions, such as the alkali...

The efficacy and feasibility of using zerovalent zinc (ZVZ) to treat 1,2,3-trichloropropane (TCP)-contaminated groundwater was assessed in lab. and field expts. In the first portion of the study, the reactivity of com. available granular ZVZ toward TCP was measured in bench-scale batch-reactor and column expts. These results were used to design col...

Zerovalent iron nanoparticles (Fe0 NPs or nZVI) synthesized by reductive precipitation in aqueous solution (Fe/FeO) differ in composition and reactivity from the NPs obtained by reductive precipitation in the presence of a S-source such as dithionite (Fe/FeS). To compare the redox properties of these types of NPs under a range of environmentally re...

Most of the main determinants of water quality either consist of, or are controlled by, particles. Previous water quality research has focused on particular particles in isolation or in binary combinations. In this project, we are taking a holistic approach to the characterization of the particle load in water, focusing on the collective properties...