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G Guisbiers,1 Q Wang,2 E Khachatryan,1 LC Mimun,1 R Mendoza-Cruz,1 P Larese-Casanova,3 TJ Webster,2,4,5 KL Nash1 1Department of Physics and Astronomy, The University of Texas at San Antonio, San Antonio, TX, 2Department of Bioengineering, 3Department of Civil and Environmental Engineering, 4Department of Chemical Engineering, Northeastern University, Boston, MA, USA; 5Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia Abstract: Nosocomial diseases are mainly caused by two common pathogens, Escherichia coli and Staphylococcus aureus, which are becoming more and more resistant to conventional antibiotics. Therefore, it is becoming increasingly necessary to find other alternative treatments than commonly utilized drugs. A promising strategy is to use nanomaterials such as selenium nanoparticles. However, the ability to produce nanoparticles free of any contamination is very challenging, especially for nano-medical applications. This paper reports the successful synthesis of pure selenium nanoparticles by laser ablation in water and determines the minimal concentration required for ~50% inhibition of either E. coli or S. aureus after 24 hours to be at least ~50 ppm. Total inhibition of E. coli and S. aureus is expected to occur at 107±12 and 79±4 ppm, respectively. In this manner, this study reports for the first time an easy synthesis process for creating pure selenium to inhibit bacterial growth. Keywords: nosocomial disease, bacteria, antibiotics resistant, cytotoxicity

Qi Wang,1 Philip Larese-Casanova,2 Thomas J Webster3,41Department of Bioengineering, College of Engineering, Northeastern University, Boston, MA, USA; 2Department of Civil and Environmental Engineering, College of Engineering, Northeastern University, Boston, MA, USA; 3Department of Chemical Engineering, College of Engineering, Northeastern University, Boston, MA, USA; 4Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi ArabiaAbstract: There are wide spread bacterial contamination issues on various paper products, such as paper towels hanging in sink splash zones or those used to clean surfaces, filter papers used in water and air purifying systems, and wrappings used in the food industry; such contamination may lead to the potential spread of bacteria and consequent severe health concerns. In this study, selenium nanoparticles were coated on normal paper towel surfaces through a quick precipitation method, introducing antibacterial properties to the paper towels in a healthy way. Their effectiveness at preventing biofilm formation was tested in bacterial assays involving Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus epidermidis. The results showed significant and continuous bacteria inhibition with about a 90% reduction from 24 to 72 hours for gram-positive bacteria including S. aureus and S. epidermidis. The selenium coated paper towels also showed significant inhibition of gram-negative bacteria like P. aeruginosa and E. coli growth at about 57% and 84%, respectively, after 72 hours of treatment. Therefore, this study established a promising selenium-based antibacterial strategy to prevent bacterial growth on paper products, which may lead to the avoidance of bacteria spreading and consequent severe health concerns.Keywords: selenium nanoparticles, paper towels, antibacterial

The purpose of the study was to examine how integrated science and disciplinary literacy instruction influenced the quality of science informational text produced by first-grade students and student perceptions these young children held about scientists. The disciplinary literacy instruction took place over the course of 8 weeks (three 20-30-min lessons/week) and incorporated reading, writing, speaking, and listening as literacy tools to make sense of science content. A single-subject design (N = 76) using a paired sample t test was used to compare results of the scores from the informational text writing samples using a writing rubric and the "Draw-a-Scientist Test." Results revealed that students were able to produce higher-quality science informational texts in all areas being examined on the weighted writing rubric. However, the perceptions the first graders had regarding scientists remained essentially unchanged from beginning to end of the study. Implications for these findings are discussed. Educators should consider disciplinary literacy instruction as a way to support young children in learning to write science informational texts effectively.

Understanding long-term impacts is essential to knowing whether an Extension program is achieving its goals. I describe a process for long-term program evaluation, using evaluation of the Utah Master Naturalist Program (UMNP) as a successful example. Surveys revealed that the UMNP had impacts on participants up to 10 years after program completion. The UMNP is achieving its goal of promoting stewardship through fostering a deeper connection to nature, encouraging lifelong learning, increasing stewardship feelings and activities, and providing effective professional development. Further long-term evaluation efforts will focus on quantifying behavior change. Overall, the UMNP evaluation process and results underscore the criticality of conducting long-term evaluation to understand lasting impacts of Extension programs.

Integrating evaluation into an Extension program offers multiple opportunities to understand program success through achieving program goals and objectives, delivering programming using the most effective techniques, and refining program audiences. It is less common that evaluation is used to guide and validate the effectiveness of program revision. Early evaluation results from Utah Master Naturalist Watersheds classes were used to make specific, targeted program revisions, and significant increases in recent evaluation results validated that the revisions were successful. Using evaluation in this way conserves time, effort, and resources, and helps achieve a high level of program success expected from Extension professionals.

Master Naturalist programs across the country have reconnected Americans with nature for >20 years. Research suggests that reconnecting humans with nature benefits personal health and wellness, educates stakeholders about the importance of conservation, and enhances individual participation in stewardship efforts. Nationally, the Alliance of Natural Resource Outreach and Service Programs coordinates and supports Master Naturalist programs through facilitating collaboration and sharing of resources, as well as organizing an annual conference. We explore the Virginia Master Naturalist and Utah Master Naturalist programs as 2 examples of different, but highly effective, statewide programs to highlight the diversity of Master Naturalist programs. The Virginia Master Naturalist was created in partnership with 5 state agencies. It is coordinated at a local chapter level, taught entirely in person, and has the primary purpose to train volunteers who support natural resource conservation in the state. The Utah Master Naturalist, in contrast, was created by Utah State University Cooperative Extension. Centrally coordinated at the state level, it is partially taught online and focuses more on connecting a highly urbanized population to the vast natural areas around the state. Master Naturalist programs provide unique opportunities for scientists and resource managers to engage the public and promote stewardship through education, volunteer opportunities, and citizen science. This mutualistic relationship benefits not only the public that learns from experts and participates in real-world management projects, but also the managers who achieve a broader impact of their work and receive valuable volunteer assistance in fulfilling their management goals.

The Utah Master Naturalist Program trains citizens who provide education, outreach, and service to promote citizen stewardship of natural resources within their communities. In 2007-2008, the Watersheds module of the program was evaluated for program success, and participant knowledge was assessed. Assessment and evaluation results indicated that amateur naturalists learned more during the course of the program and also consistently evaluated the program more positively than professional naturalists. These results were used to adjust the target audience in order to maximize learning, program success, and marketing effectiveness. (Contains 3 tables and 1 figure.)

Graphene materials represent a new carbonaceous sorbent for the removal of organic micropollutants from water, and most applications of graphene utilize an oxidized, negatively-charged surface to improve dispersibility. However, classes of anionic micropollutants may undergo less sorption than cationic or neutral compounds on graphene oxide due to electrostatic repulsion forces. This work seeks to improve the sorptive capability of graphene for anionic micropollutants through amending surfaces with positive charges. Graphene oxide was functionalized with ethylenediamine (ED-G) through an acyl chlorination and amidation process that allows a net positive surface charge at pH < 8.1. ED-G held greater sorption capacity for anionic ibuprofen compared to cationic atenolol and neutral carbamazepine for nearly all water conditions within batch reactors. Ibuprofen sorption greatly increased, and atenolol sorption decreased, at more acidic solution pH. Competitive sorption experiments showed that ibuprofen is consistently preferred on ED-G over atenolol over a wide range of concentrations, and the presence of other anionic compounds can suppress the sorption of ibuprofen. These trends in sorption extent, sorbate charge, and sorbent charge indicate electrostatic interactions largely govern the binding of sorbate molecules. Consequently, a positively-charged graphene material could enhance the removal of anionic micropollutants within water treatment systems compared to graphene oxide. [ABSTRACT FROM AUTHOR]

Short‐term field days are a common outreach tool for watershed programs, yet little is known about their effectiveness. To address this question, we conducted pre‐ and post‐tests on 4th grade students who participated in a field day at a U.S. Forest Service campground. In addition to assessing the value of the single field day, we also tested the value of additional activities on knowledge gain and retention over time. Classes that only participated in the field days demonstrated a significant increase in knowledge after 2 weeks and after 8 months, although the 8‐month scores decreased significantly compared with the 2‐week scores. We found a similar pattern for classes that received pre‐ and post‐classroom lessons on water. A third group of classes participated in a second field day toward the end of the school year. As with the other groups, this group demonstrated a significant increase in post‐test scores, but no significant decrease in post‐test scores over time. We also evaluated the single field day for evidence of changed attitudes about protecting streams. We found a heightened sense of stewardship in this group on the 2‐week post‐test. We conclude that short‐term environmental education programs can be effective at increasing knowledge and promoting feelings of stewardship. We also conclude that enhancing these programs with high‐quality lessons or additional field experiences may result in greater retention over time. [ABSTRACT FROM AUTHOR]

Both legacy munitions compounds (e.g., RDX) and new insensitive high explosives (e.g. DNAN, NQ) are being manufactured and utilized concurrently, and there exists a need for wastewater treatment systems that are able to degrade both classes of explosives. Electrochemical systems offer treatment possibilities using inexpensive materials and no chemical additions. Electrochemically induced removal of RDX, NQ, and DNAN were separately studied within an electrochemical plug flow reactor hosting a stainless steel (SS) cathode and downstream Ti/MMO anode. Varying wire mesh cathodes and operating conditions were evaluated in an effort to identify the optimal cathode material, to determine the relative contributions of cathodically-induced removal processes, to shorten time to steady-state removal conditions, and to find practical ranges of operating conditions. Applied current allowed the cathode to support munitions removal mainly by direct reduction at the cathode surface, and the secondary reactions of cathodically-induced alkaline hydrolysis and catalytic hydrogenation by adsorbed H on Ni-containing cathode surfaces might contribute to some munitions degradation. The optimal cathode material was identified as SS grade 316, possibly due to its superior Ni content and lack of corrosion protection coating. Higher current, longer cathode length, and smaller mesh pore sizes resulted in slightly greater removal extents and shorter acclimation times to steady state removal conditions, but there are practical upper limits to these properties. Higher Ni content within SS improved RDX and NQ removal but does not affect DNAN removal. Prolonged use of SS grade 316 showed no debilitating changes in electrical performance or chemical content. [Display omitted] • Dissolved RDX, NQ, and DNAN explosives were reduced electrochemically under flow. • Materials and conditions were investigated to maximize removal and minimize startup time. • The optimal cathode material was stainless steel grade 316 with mesh size #80. • Alkaline hydrolysis of explosives is a secondary reaction when pH > 12. [ABSTRACT FROM AUTHOR]

Understanding long-term impacts is essential to knowing whether an Extension program is achieving its goals. I describe a process for long-term program evaluation, using evaluation of the Utah Master Naturalist Program (UMNP) as a successful example. Surveys revealed that the UMNP had impacts on participants up to 10 years after program completion. The UMNP is achieving its goal of promoting stewardship through fostering a deeper connection to nature, encouraging lifelong learning, increasing stewardship feelings and activities, and providing effective professional development. Further long-term evaluation efforts will focus on quantifying behavior change. Overall, the UMNP evaluation process and results underscore the criticality of conducting long-term evaluation to understand lasting impacts of Extension programs. [ABSTRACT FROM AUTHOR]

Integrating evaluation into an Extension program offers multiple opportunities to understand program success through achieving program goals and objectives, delivering programming using the most effective techniques, and refining program audiences. It is less common that evaluation is used to guide and validate the effectiveness of program revision. Early evaluation results from Utah Master Naturalist Watersheds classes were used to make specific, targeted program revisions, and significant increases in recent evaluation results validated that the revisions were successful. Using evaluation in this way conserves time, effort, and resources, and helps achieve a high level of program success expected from Extension professionals. [ABSTRACT FROM AUTHOR]

The Utah Master Naturalist Program trains citizens who provide education, outreach, and service to promote citizen stewardship of natural resources within their communities. In 2007-2008, the Watersheds module of the program was evaluated for program success, and participant knowledge was assessed. Assessment and evaluation results indicated that amateur naturalists learned more during the course of the program and also consistently evaluated the program more positively than professional naturalists. These results were used to adjust the target audience in order to maximize learning, program success, and marketing effectiveness. [ABSTRACT FROM AUTHOR]

New insensitive high explosives pose great challenges to conventional explosives manufacturing wastewater treatment processes and require advanced methods to effectively and efficiently mineralize these recalcitrant pollutants. Oxidation processes that utilize the fundamental techniques of Fenton chemistry optimized to overcome conventional limitations are vital to provide efficient degradation of these pollutants while maintaining cost-effectiveness and scalability. In this manner, utilizing heterogeneous catalysts and in-situ generated H2O2 to degrade IHEs is proposed. For heterogeneous catalyst optimization, varying the surface chemistry of activated carbon for use as a catalyst removes precipitation complications associated with iron species in Fenton chemistry while including removal by adsorption. Activated carbon impregnated with 5% MnO2 in the presence of H2O2 realized a high concentration of hydroxyl radical formation - 140 μM with 10 mM H2O2 - while maintaining low cost and relative ease of synthesis. This AC-Mn5 catalyst performed effectively over a wide pH range and in the presence of varying H2O2 concentrations with a sufficient effective lifetime. In-situ generation of H2O2 removes the logistical and economic constraints associated with external H2O2, with hydrophobic carbon electrodes utilizing generated gaseous O2 for 2-electron oxygen reduction reactions. In a novel flow-through reactor, gaseous O2 is generated on a titanium/mixed metal oxide anode with subsequent H2O2 electrogeneration on a hydrophobic microporous-layered carbon cloth cathode. This reactor is able to electrogenerate 2 mM H2O2 at an optimized current intensity of 150 mA and over a wide range of flow rates, influent pH values, and through multiple iterations. Coupling these two optimization methods realizes the production of highly oxidative hydroxyl radicals by Fenton-like catalysis of electrogenerated H2O2 on the surface of an MnO2-impregnated activated carbon catalyst. This method incorporates electrochemically induced oxidation of munitions in addition to removal by adsorption while maintaining cost-effectiveness and scalability. It is anticipated this platform holds great promise to eliminate analogous contaminants.

Biofilm formation in Bacillus subtilis requires high levels of ferric iron. Here, Qin et al. show that iron accumulation requires production of dihydroxybenzoate (a precursor in siderophore biosynthesis), and matrix-associated iron may be acting as extracellular electron acceptor during respiratory electron transfer.

Magnetic carbonaceous nanomaterials are needed in water treatment applications because they can offer both carbon surfaces for sorption of organic pollutants and ease of material magnetic retrieval for regeneration and reuse. In this study, we employed a facile one-step method to synthesize a black carbon-magnetite composite (BC-Mag) by high-temperature annealing of black carbon and hematite. The nanocomposite was easily dispersed and stable in water owing to the presence of negatively charged oxygen surface functional groups. Sorption kinetics with dissolved carbamazepine showed a rapid initial uptake with equilibrium achieved within only minutes. The sorption extent can be described with the Freundlich model, and surface area normalized sorption affinity was an order of magnitude greater than conventional granular activated carbon. The sorption extent of neutral carbamazepine remained constant between pH 2−10 while surface zeta potential decreased. BC-Mag can be reused for the sorption of carbamazepine up to six times without significant loss of the sorption extent.

New insensitive high explosives pose great challenges to conventional explosives manufacturing wastewater treatment processes and require advanced methods to effectively and efficiently mineralize these recalcitrant pollutants. Oxidation processes that utilize the fundamental techniques of Fenton chemistry optimized to overcome conventional limitations are vital to provide efficient degradation of these pollutants while maintaining cost-effectiveness and scalability. In this manner, utilizing heterogeneous catalysts and in-situ generated H 2 O 2 to degrade IHEs is proposed. For heterogeneous catalyst optimization, varying the surface chemistry of activated carbon for use as a catalyst removes precipitation complications associated with iron species in Fenton chemistry while including removal by adsorption. Activated carbon impregnated with 5% MnO 2 in the presence of H 2 O 2 realized a high concentration of hydroxyl radical formation - 140 μM with 10 mM H 2 O 2 - while maintaining low cost and relative ease of synthesis. This AC-Mn5 catalyst performed effectively over a wide pH range and in the presence of varying H 2 O 2 concentrations with a sufficient effective lifetime. In-situ generation of H 2 O 2 removes the logistical and economic constraints associated with external H 2 O 2 , with hydrophobic carbon electrodes utilizing generated gaseous O 2 for 2-electron oxygen reduction reactions. In a novel flow-through reactor, gaseous O 2 is generated on a titanium/mixed metal oxide anode with subsequent H 2 O 2 electrogeneration on a hydrophobic microporous-layered carbon cloth cathode. This reactor is able to electrogenerate 2 mM H 2 O 2 at an optimized current intensity of 150 mA and over a wide range of flow rates, influent pH values, and through multiple iterations. Coupling these two optimization methods realizes the production of highly oxidative hydroxyl radicals by Fenton-like catalysis of electrogenerated H 2 O 2 on the surface of an MnO 2 -impregnated activated carbon catalyst. This method incorporates electrochemically induced oxidation of munitions in addition to removal by adsorption while maintaining cost-effectiveness and scalability. It is anticipated this platform holds great promise to eliminate analogous contaminants., Competing Interests: Conflict of Interest: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The effective and efficient degradation of persistent, recalcitrant pollutants by advanced oxidation processes is vital to both reduce hazardous waste and remediate polluted waters. One such advanced oxidation process is the use of Fenton chemistry, which can be optimized using heterogeneous catalysts. However, to make this AOP viable over conventional treatment methods, the technology needs to be optimized from both a technical and economic standpoint. From a heterogeneous catalyst optimization perspective, varying the surface chemistry of activated carbon and impregnating or doping with Fenton-like catalytic nanomaterials removes precipitation complications associated with traditional iron species in Fenton chemistry while generating effective amounts of highly oxidative hydroxyl radicals. Utilizing various techniques to synthesize heterogeneous catalysts with activated carbon as a backbone, in the presence of H 2 O 2 the formation of hydroxyl radicals and removal of benzoic acid is tested. Comparing various additives, raw activated carbon impregnated with 5% MnO 2 in the presence of H 2 O 2 realized a high concentration of hydroxyl radical formation while maintaining low cost and relative ease of synthesis. This AC-Mn5 catalyst performed effectively in varying concentrations of H 2 O 2 , utilizing various synthesis techniques, after simulated aging of the catalyst structure, and over a wide pH range with the highest radical formation at acidic pH values. Utilizing this catalytic material as a substitute for iron species associated with traditional Fenton technology, the goal of designing a full set of oxidation functions towards persistent, recalcitrant pollutant removal while maintaining cost-effectiveness and scalability is proposed. It is anticipated these catalytic materials are effective to eliminate analogous contaminants and mixtures., Competing Interests: Conflict of Interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Selenium and oxygen isotope systematics can be useful tools for tracing sources and fate of Se oxyanions in water. In order to measure δ 18 O values of selenate, SeO 4 2- must first be sequestered from water by precipitation as BaSeO 4(s) . However, other dissolved oxyanions insoluble with Ba 2+ require removal. Dissolved selenate was separated from dissolved selenite, carbonate, phosphate, and arsenate by addition of Ce 3+ cations that quantitatively removed these oxyanions by precipitation as insoluble Ce 2 (SeO 3 ) 3(s) , Ce 2 (CO 3 ) 3(s) , CePO 4(s) , and CeAsO 4(s) , respectively. δ 18 O-selenate (-8.19 ± 0.17 ‰) did not change after four replicates of selenite removal by Ce 2 (SeO 3 ) 3(s) precipitation and Ce 3+ removal by cation exchange (-8.20 ± 0.14, -8.32 ± 0.09, -8.17 ± 0.13, and -8.29 ± 0.13 ‰). δ 18 O-selenate values (-10.86 ± 0.45 ‰) were preserved also when selenate was pre-concentrated on anion exchange resin, quantitatively retrieved by elution, and processed with Ce 3+ to remove interfering oxyanions (-10.77 ± 0.07 ‰). The extraction and purification steps developed here successfully isolated dissolved selenate from interfering oxyanions while preserving δ 18 O-selenate values. This method should be useful for characterizing δ 18 O-selenate when present with the co-occurring oxyanions above in laboratory experiments and field sites with high Se concentrations, although further research is required for methods to eliminate any co-occurring sulphate.

Widespread usage of engineered metallic quantum dots (QDs) within consumer products has evoked a need to assess their fate within environmental systems. QDs are mixed-metal nanocrystals that often include Cd 2+ which poses a health risk as a nanocrystal or when leached into water. The goal of this work is to study the long-term metal cation leaching behavior and the factors affecting the dissolution processes of mercaptopropionic acid (MPA) capped CdSe/ZnS QDs in aphotic conditions. QD suspensions were prepared in different water conditions, and release of Zn 2+ and Cd 2+ cations were monitored over time by size exclusion chromatography-inductively coupled plasma-mass spectrometry. In most conditions with dissolved O 2 present, the ZnS shell degraded fairly rapidly over ~1 week, while some of the CdSe core remained up to 80 days. Additional MPA, Zn 2+ , and Cd 2+ temporarily delayed dissolution, indicating a moderate role for capping agent detachment and mineral solubility. The presence of H 2 O 2 and the ligand ethylenediaminetetraacetate accelerated dissolution, while NOM had no kinetic effect. No dissolution of CdSe core was observed when O 2 was absent or when QDs formed aggregates at higher concentrations with O 2 present. The shrinking particle model with product layer diffusion control best describes Zn 2+ and Cd 2+ dissolution kinetics. The longevity of QDs in their nanocrystal form appears to be partly controlled by environmental conditions, with anoxic, aphotic environments preserving the core mineral phase, and oxidants or complexing ligands promoting shell and core mineral dissolution., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019. Published by Elsevier B.V.)

Magnetic carbonaceous nanomaterials are needed in water treatment applications because they can offer both carbon surfaces for sorption of organic pollutants and ease of material magnetic retrieval for regeneration and reuse. In this study, we employed a facile one-step method to synthesize a black carbon-magnetite composite (BC-Mag) by high-temperature annealing of black carbon and hematite. The nanocomposite was easily dispersed and stable in water owing to the presence of negatively charged oxygen surface functional groups. Sorption kinetics with dissolved carbamazepine showed a rapid initial uptake with equilibrium achieved within only minutes. The sorption extent can be described with the Freundlich model, and surface area normalized sorption affinity was an order of magnitude greater than conventional granular activated carbon. The sorption extent of neutral carbamazepine remained constant between pH 2-10 while surface zeta potential decreased. BC-Mag can be reused for the sorption of carbamazepine up to six times without significant loss of the sorption extent., Competing Interests: Data Availability: Research data is available upon request.

The green synthesis of biomaterials is of significant interest as it enables the safe and sustainable preparation of noble metallic nanoparticles for medical applications. Microalgae polysaccharides have received attention due to their outstanding properties such as biocompatibility, biodegradability and low cost. In addition, due to their variety of remarkable biological and physicochemical properties, polysaccharide-based nanoparticles have advantageous features yet to be explored. The primary objective of the current research was to investigate exopolysaccharides isolated from green microalgae Botryococcus braunii (EPBb) and Chlorella pyrenoidosa (EPCp), as both reducing and stabilizing agents, for the green synthesis of silver nanoparticles (AgNPs). Their antibacterial activity towards Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli), and antibiotic-resistant bacteria (methicillin-resistant Staphylococcus aureus) was studied, as well as their cytotoxicity to human dermal fibroblasts. The presently synthesized AgNPs were spherical in shape and exhibited characteristic surface plasmon resonance at 430 nm. The main population had a particle size which ranged between 5 and 15 nm as analyzed by transmission electron micrographs. Zeta potentials averaged -51.81 ± 3.01 mV using EPBb and -12.16 ± 2.41 mV using EPCp. More importantly, AgNPs possessed strong antibacterial activity in a dose-dependent manner, even against drug-resistant bacteria. The enhanced antibacterial activity of these particles is explained due to extensive reactive oxygen species generation and bacterial cell membrane damage. In contrast, such AgNPs were not cytotoxic at the same therapeutic range to fibroblasts (0.5-10.0 μg/mL). In summary, these results showed that polysaccharide-capped AgNPs have a strong potential for numerous medical applications, such as antibacterial agents in pharmaceutical and biomedical areas., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Recent work has shown that iron oxides, such as goethite and hematite, may recrystallize in the presence of aqueous Fe 2+ under anoxic conditions. This process, referred to as Fe 2+ -catalyzed recrystallization, can influence water quality by causing the incorporation/release of environmental contaminants and biological nutrients. Accounting for the effects of Fe 2+ -catalyzed recrystallization on water quality requires knowing the time scale over which recrystallization occurs. Here, we tested the hypothesis that nanoparticulate goethite becomes less susceptible to Fe 2+ -catalyzed recrystallization over time. We set up two batches of reactors in which 55 Fe 2+ tracer was added at two different time points and tracked the 55 Fe partitioning in the aqueous and goethite phases over 60 days. Less 55 Fe uptake occurred between 30 and 60 days than between 0 and 30 days, suggesting goethite recrystallization slowed with time. Fitting the data with a box model indicated that 17% of the goethite recrystallized after 30 days of reaction, and an additional 2% recrystallized between 30 and 60 days. The decreasing susceptibility of goethite to recrystallize as it reacted with aqueous Fe 2+ suggested that recrystallization is likely only an important process over short time scales.

Nano metal oxides are of interest for aqueous selenium (Se) remediation, and as such, nano-hematite (nα-Fe2O3) was examined for use as a Se adsorbent. The effect of surface area on adsorption was also studied. nα-Fe2O3 particles were synthesized from Fe(NO3)3 and FeCl3 via forced hydrolysis. The resulting particles have similar sizes, morphologies, aggregate size, pore size, and PZC. The nα-Fe2O3 from FeCl3 (nα-Fe2O3-C) differs from the nα-Fe2O3 from Fe(NO3)3 (nα-Fe2O3-N) with a ∼25±2m(2)/g greater surface area. Selenite Se(IV) adsorption capacity on nα-Fe2O3 has a qmax ∼17mg/g for the freeze-dried and re-suspended nα-Fe2O3. The Δqmax for nα-Fe2O3 from Fe(NO3)3 and FeCl3 that remained in suspension was 4.6mg/g. For selenate Se(VI), the freeze-dried and re-suspended particles realize a Δqmax= 1.5mg/g for nα-Fe2O3 from Fe(NO3)3 and FeCl3. The nα-Fe2O3 from Fe(NO3)3 and FeCl3 that remained in suspension demonstrated Se(VI) Δqmax=5.4mg/g. In situ ATR-FTIR isotherm measurements completed for Se(VI) at a pH 6 suggest that Se(VI) forms primarily outer-sphere complexes with nα-Fe2O3 synthesized from both salts., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Hypothesis: Graphene nanosheet materials represent a potentially new high surface area sorbent for the treatment of endocrine disrupting compounds (EDCs) in water. However, sorption behavior has been reported only for laboratory graphene prepared by a laborious and hazardous graphite exfoliation process. A careful examination of commercially available, clean, high-volume produced graphene materials should reveal whether they are appropriate for sorbent technologies and which physicochemical properties most influence sorption performance., Experiments: In this study, three commercially available graphene oxide powders of various particle sizes, specific surface areas, and surface chemistries were evaluated for their sorption performance using carbamazepine and nine other EDCs and were compared to that of conventional granular activated carbon (GAC) and multi-walled carbon nanotubes (MWCNTs)., Findings: Sorption kinetics of carbamazepine on graphene oxide powders was rapid and reversible with alcohol washing, consistent with π-π interactions. The various sorption extents as described by Freundlich isotherms were best explained by available surface area, and only the highest surface area graphene oxide (771 m(2)/g) out-performed GAC and MWCNTs. Increasing pH caused more negative surface charge, a twofold decrease in sorption of anionic ibuprofen, a onefold increase in sorption of cationic atenolol, and no change for neutral carbamazepine, highlighting the role of electrostatic interactions., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Rationale: Past stable isotopic studies of selenium and arsenic oxyanions within a biogeochemistry context have focused solely on selenium isotopes due to monoisotopic nature of arsenic and lack of attention to oxygen. A modern quantification method of δ(18)O values in selenate, selenite, arsenate, and arsenite is presented here, similar to methods for other inorganic oxyanions such as phosphate., Methods: Dissolved oxyanions were recovered after precipitation with silver or barium cations within controlled pH ranges and purified by drying and roasting under vacuum. Oxygen isotope ratio measurements were performed on 250-450 micrograms of solids using continuous flow high-temperature conversion elemental analyzer/isotope ratio mass spectrometry (CF-TCEA/IRMS). Each Se and As solid was evaluated for reproducibility and stability of δ(18)O values and the usefulness of this method for evaluating aqueous phase Se and As oxyanion reactions was addressed., Results: Only silver arsenate and barium selenate were shown to have stable, reproducible δ(18)O values over 5 months and were calibrated to the VSMOW scale. The method was applied to confirm complete exchange of oxygen isotopes between arsenate and solvent water at pH 7 which produced an O-isotope fractionation between arsenate and water of 6.0‰. Furthermore, the method revealed the ability of oxygen in selenate to kinetically fractionate during reduction to elemental selenium by a green rust compound which produced a fractionation (20.9‰) larger than reported δ(80/76)Se values for similar reactions., Conclusions: The experimental and analytical conditions for δ(18)O analysis of Se and As oxyanions were detailed. δ(18)O analyses of As and Se oxyanions may be useful in biogeochemical studies for tracing chemical reaction pathways, determining environmental sources of Se, or diagnosing specific reaction mechanisms for As and Se oxyanions., (Copyright © 2012 John Wiley & Sons, Ltd.)

The redox state and speciation of the metalloid arsenic (As) determine its environmental fate and toxicity. Knowledge about biogeochemical processes influencing arsenic redox state is therefore necessary to understand and predict its environmental behavior. Here we quantified arsenic redox changes by pH-neutral goethite [alpha-Fe(III)OOH] mineral suspensions amended with Fe(II) using wet-chemical and synchrotron X-ray absorption (XANES) analysis. Goethite itself did not oxidize As(III) and, in contrast to thermodynamic predictions, Fe(II)-goethite systems did not reduce As(V). However, we observed rapid oxidation of As(III) to As(V) in Fe(II)-goethite systems. Mössbauer spectroscopy showed initial formation of (57)Fe-goethite after (57)Fe(II) addition plus a so far unidentified additional Fe(II) phase. No other Fe(III) phase could be detected by Mössbauer, EXAFS, SEM, XRD, or HR-TEM. This suggests that reactive Fe(III) species form as an intermediate Fe(III) phase upon Fe(II) addition and electron transfer into bulk goethite but before crystallization of the newly formed Fe(III) as goethite. In summary this study indicates that in the simultaneous presence of Fe(III) oxyhydroxides and Fe(II), as commonly observed in environments inhabited by iron-reducing microorganisms, As(III) oxidation can occur. This potentially explains the presence of As(V) in reduced groundwater aquifers.

Electron exchange between aqueous Fe(II) and structural Fe(III) in iron oxides and oxyhydroxides is important for understanding degradation of environmental pollutants through its apparent constitutive role underlying highly reactive "sorbed Fe(II)" and by catalyzing phase interconversion among these minerals. Although a mechanistic understanding of relationships between interfacial Fe(II)(ads)-Fe(III)(oxide) electron transfer, bulk electron conduction, Fe(II) release, and phase transformation behavior is emerging, much remains unclear, in part due to poorly interconnected investigations. The focus of this study is on reconciling two mutually similar observations of Fe(II)-catalyzed hematite growth documented spectroscopically and microscopically under substantially different chemical conditions. Here, we employ iron isotopic labeling to demonstrate that hematite grown on the (001) surface in Fe(II)-oxalate solution at pH 2.10 and 348 K has magnetic properties that closely correspond to those of hematite grown in Fe(II) solution at pH 7.4 and room temperature. The temperature evolution and extent of the Morin transition displayed in these two materials strongly suggest a mechanistic link involving trace structural Fe(II) incorporation into the growing hematite. Our findings indicate that Fe(II) catalyzed growth of hematite on hematite can occur under environmentally relevant conditions and may be due to bulk electron conduction previously demonstrated for hematite single crystals.

The rate and extent of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) transformation was measured in the presence of carbonate and sulfate green rust suspended in solutions containing common groundwater anions. Formaldehyde (HCHO), nitrous oxide gas (N2O(g)), and ammonium (NH4+) were the major end products, accounting for about 70% of the carbon mass balance and about half of the nitrogen mass balance. Results from experiments with both 14C-RDX and LC-MS analysis indicate that the remaining carbon products are soluble and most likely small (< 50 Da). The transient appearance of 1,3-dinitro-5-nitroso-1,3,5-triazacyclohexane (MNX), 1,3-dinitroso-5-nitro-1,3,5-triazacyclohexane (DNX), and 1,3,5-trinitroso-1,3,5-triazacyclohexane (TNX) indicate that some nitro-group reduction occurred. The kinetics of RDX transformation was rapid with a half-life of less than an hour in a pH 7.0 KBr solution. Little difference in rates of RDX transformation or product distribution was observed between carbonate and sulfate green rust, and an apparent reaction order of 1.0 was measured with respect to Fe(II) in both green rusts. Phosphate anions completely inhibited RDX reduction, and carbonate and sulfate anions resulted in slower kinetics, and in some cases, an initial lag period, compared to bromide and chloride. Our results suggest that green rusts may contribute to abiotic natural attenuation of RDX in Fe-rich subsurface environments, but that it will be important to consider groundwater composition when assessing rates of attenuation.