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This study examines the effects of Pseudomonas aeruginosa (PAO1) biofilm, with a concentration of cells similar to that reported for saturated aquifers, on the transport of poly(acrylic acid) stabilized nanoscale zero valent iron (pnZVI) in 14 cm long, saturated, laboratory packed columns, with ionic strengths (ISs) of 1 and 25 mmol NaCl. With biofilm, the retention of pnZVI increased with higher solution IS, while IS played no role in the retention of nanoparticles without biofilm. However, the Tufenkji-Elimelech correlation equation predicts 5% less pnZVI collisions in biofilm coated columns due to a sixfold reduction of the Hamaker constant. Also, DLVO energy considerations predict the most favorable attachment for uncoated porous media at the higher IS. Reasons for the disagreement between theory and experiment are shown to be due to the non-ideality of the biofilm system. This research indicates that current laboratory studies underestimate nanoparticle transport distances in the subsurface. / Environmental Science

The use of nano zerovalent iron (nZVI) for environmental remediation is a promising new technique for in situ remediation. Due to its high surface area and high reactivity, nZVI is able to dechlorinate organic contaminants and render them harmless. Limited mobility, due to fast aggregation and sedimentation of nZVI, limits the capability for source and plume remediation. Carbo-Iron is a newly developed material consisting of activated carbon particles (d50 = 0,8 µm) that are plated with nZVI particles. These particles combine the mobility of activated carbon and the reactivity of nZVI. This paper presents the rst results of the transport experiments. / Der Einsatz von elementarem Nanoeisen ist eine vielversprechende Technik zur Sanierung von Altlastenschadensfällen. Aufgrund der hohen Oberäche und der hohen Reaktivität kannn ZVI chlororganische Schadstoffe dechlorieren und zu harmlosen Substanzen umwandeln. Der Einsatz von Nanoeisen zur Quellen- und Fahnensanierung wird jedoch durch mangelnde Mobilität im Boden im eingeschränkt. Carbo-Iron ist ein neu entwickeltes Material, das aus Aktivkohlepartikeln (d50 = 0,8 µm) und nZVI besteht. Diese Partikel kombinieren die Mobilit ät von Aktivkohle mit der Reaktivität von nZVI. Dieser Artikel beschreibt erste Ergebnisse von Transportuntersuchungen.

No description available.

The lack of biodegradability of PFAS, or per- and polyfluoroalkyl substances, is due to the presence of many strong carbon-fluorine bonds. Two common PFAS that are found in the environment are perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). This work first studied an innovative pathway for PFAS removal through the adsorption of PFOA and PFOS (pre-concentrating the contaminants) by nanoscale zero-valent iron/reduced graphene oxide (rGO-nZVI) and their subsequent degradation via photocatalysis under UVC light. The GO that was later reduced in nanohybrid production was made utilizing a modified Hummer’s method. The rGO-nZVI nanohybrid was prepared for the first time via thermal reduction at high temperatures. Additionally, the nanohybrid was prepared using the wet chemistry method for comparison. LC/MS/MS analysis was conducted to determine the adsorption efficiencies for PFOA and PFOS using the nanohybrids and their successive removal under UVC light. Chlorinated hydrocarbons are another group of contaminants of concern that should be removed from the subsurface due to their harmful effects. In this study, a more complex mixture of the contaminants including PFAS and chlorinated hydrocarbons was investigated, which is usually found in the superfund and other contaminated sites. Considering the effectiveness of nZVI to remove chlorinated hydrocarbons from the subsurface, engineered nZVI coupled with rGO was utilized to enhance the removal efficiency of the mixture of contaminants, i.e., PFAS comingled with chlorinated hydrocarbons. The synthesized rGO-nZVI nanoparticle showed high adsorption efficiencies for both PFOA and PFOS, i.e., removal of 55.3%, 98.2%, and >99.9% of PFOA of 10, 1, and 0.1 mg/L, and 94.9%, 97.6%, and 85.0% of PFOS of 10, 1, and 0.1 mg/L, respectively, in 3 h. Later degradation of pre-concentrated PFAS under UVC light was also achieved. Using extracted rGO-nZVI, 55.1%, 77.6% of preconcentrated PFOS was degraded starting from 10, and 1 mg/L of initial concentrations before adsorption in the photoreactor at the end of 24 h. In comparison, 68.5% and 47.2% of PFOS and PFOA (starting from 1 mg/L each) was degraded, respectively, using rGO-nZVI directly under UVC light after 24 h. Moreover, it was found that rGO-nZVI had high adsorption capacity of 69.4% and 68.7% respectively for TCE and PFOA in a mixture of these contaminants. Under UVC irradiation, the preconcentrated mixture of TCE and PFOA were both degraded to below the detection limit in 21 h. It was also found that PFOA concentration dropped by 64.3% at 5 h and by 88.7% at 24 h by fresh rGO-nZVI in presence of 10 mg/L TCE. Short-chained PFCAs like PFHpA and PFHxA were found as the intermediates for PFOA degradation using rGO-nZVI under UVC light. Also, under UVC irradiation of a mixture of TCE and PFOA, TCE degradation was supported by the formation of intermediates during the reaction. Because of its composition, photocatalytic activity, large surface area, magnetic properties, and environmental friendliness, the thermal reduced rGO-nZVI particle demonstrated its potential to successfully remove PFAS and comingled chlorinated hydrocarbon from pre-concentration followed by degradation under UVC light. The nanohybrid is promising to be used to repair PFAS-contaminated water bodies.

This research is focused on engineering submicron spherical carbon particles as effective carriers/supports for nanoscale zerovalent iron (NZVI) particles to address the in situ remediation of soil and groundwater chlorinated contaminants. Chlorinated hydrocarbons such as trichloroethylene (TCE) and tetrachloroethylene (PCE) form a class of dense non-aqueous phase liquid (DNAPL) toxic contaminants in soil and groundwater. The in situ injection of NZVI particles to reduce DNAPLs is a potentially simple, cost-effective, and environmentally benign technology that has become a preferred method in the remediation of these compounds. However, unsupported NZVI particles exhibit ferromagnetism leading to particle aggregation and loss in mobility through the subsurface. This work demonstrates two approaches to prepare carbon supported NZVI (iron-carbon composites) particles. The objective is to establish these iron-carbon composites as extremely useful materials for the environmental remediation of chlorinated hydrocarbons and suitable materials for the in situ injection technology. This research also demonstrates that it is possible to vary the placement of iron nanoparticles either on the external surface or within the interior of carbon microspheres using a one-step aerosol-based process. The simple process of modifying iron placement has significant potential applications in heterogeneous catalysis as both the iron and carbon are widely used catalysts and catalyst supports. Furthermore, the aerosol-based process is applied to prepare new class of supported catalytic materials such as carbon-supported palladium nanoparticles for ex situ remediation of contaminated water. The iron-carbon composites developed in this research have multiple functionalities (a) they are reactive and function effectively in reductive dehalogenation (b) they are highly adsorptive thereby bringing the chlorinated compound to the proximity of the reactive sites and also serving as adsorption materials for decontamination (c) they are of the optimal size for transport through sediments (d) they have amphiphilic chemical functionalities that help stabilize them when they reach the DNAPL target zones. Finally, the iron-carbon composite microspheres prepared through aerosol-based process can used for in situ injection technology as the process is conductive to scale-up and the materials are environmentally benign. / acase@tulane.edu

The main objective of this study was to evaluate the feasibility of using nanoscale zero-valent iron (nZVI) as the source of hydrogen to enhance in situ anaerobic biodegradation of trichloroethylene (TCE). In the first part of this study, microcosms were constructed to evaluate the effects of different controlling factors [e.g., different redox conditions (aerobic and anaerobic conditions), different microorganisms (in situ microorganisms, activated sludge, and anaerobic sludge), and different sources of substrates and electron donors (phenol, cane molasses, hydrogen, and nZVI)] on TCE biodegradation. In the second part of this study, batch experiments were conducted to evaluate the feasibility of hydrogen production by nZVI and bimetallic particles. Results from the microcosm study indicate that in-situ microorganisms were capable of degrading TCE under aerobic and anaerobic conditions. Results also show that TCE removal was more effective by activated sludge and anaerobic sludge. Aerobic biodegradation of TCE was enhanced by the addition of phenol and cane molasses. Under anaerobic conditions, TCE removal could be improved when cane molasses and hydrogen were supplied. In addition, anaerobic TCE degradation was more effective with the presence of hydrogen. Results of microcosms conducted with the addition of nZVI reveal that TCE was degraded completely in both live and autoclaved microcosms. This indicates that chemical reductive dechlorination seemed to dominate the removal of TCE in microcosms. Therefore, further studies with higher TCE concentrations or lower nZVI doses need to be conducted to determine the effects of the produced hydrogen on TCE biodegradation. Results from the hydrogen production experiments indicate that efficiency of hydrogen production by nZVI ranged from 30% to 76%. Higher dose of nZVI addition resulted in higher amount of hydrogen production. The total amounts of hydrogen production were correlated with the doses of nZVI. In addition, rates and efficiency of hydrogen production by bimetallic particles were better than those of nZVI. Results of the batch experiments reveal that nZVI and bimetallic particles had good efficiency on hydrogen production. This indicates that nZVI and bimetallic particles have high potential to be used as hydrogen producers. In this study, a simple system consisted of only water and nZVI or bimetallic particles was applied to produce hydrogen. Although TCE in microcosms with nZVI addition was totally consumed by nZVI, results of microcosms with hydrogen addition demonstrated that hydrogen was able to improve the efficiency of anaerobic TCE biodegradation. Thus, it may be feasible to use nZVI as the source of hydrogen to enhance in situ anaerobic biodegradation of TCE. The advantages of using nZVI as the source of hydrogen include: (1) rapid removal of significant contaminant concentrations in the early stage of nZVI injection; (2) creation of a more reducing environment; (3) safer than liquid hydrogen, which is stored in steel containers; and (4) direct hydrogen supply without transfer of biological mechanisms compared to commercial hydrogen release compounds and other organic substrates. Results of this study suggest that biological reductive dechlorination of TCE can be enhanced if proper doses of nZVI are supplied in situ. Knowledge and comprehension obtained in this study will be helpful in designing an enhanced in situ anaerobic bioremediation system for a TCE-contaminated site.

Wastewater reclamation and reuse have been increasingly practiced as sustainable strategies to meet water demands, particularly in regions threatened by water shortages. However, one of the biggest challenges for reusing wastewater effluents (WEs) as irrigation water is to remove emerging organic contaminants such as persistent and potentially bioaccumulated per- and polyfluoroalkyl substances (PFAS), whose presence may result in adverse impacts on crops, soils, aqueous ecosystems, and human health. Photocatalysis is an effective and promising technique to remediate PFAS in aqueous media. This dissertation aims to: i) Develop a novel, environmental-friendly, and low-cost treatment process for PFAS removal and degradation for water reuse; ii) Optimize the experimental conditions and investigate the removal mechanisms of PFAS with different structures in this novel process; iii) Scale up this treatment process and apply it to treatment of WEs in a point-of-use (POU) system. First, ultraviolet (UV) C /nanoscale zero-valent iron (nZVI, Fe0 nanoparticles (NPs)) system is used for the first time to induce PFAS photocatalytic removal from aqueous solution. Oxidative and/or reductive degradation of three representative PFAS - perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctane sulfonate (PFOS) was achieved using Fe0 NPs under UVC light both with and without presence of oxygen. However, no PFAS removal was observed either under visible light and in the dark, and much lower PFAS degradation was achieved under UVA light. Higher degradation and defluorination efficiencies were obtained for longer chain PFNA compared to PFOA, and higher degradation and defluorination of PFAS were achieved without presence of O2 compared to with O2. The degradation of PFOA and PFOS followed first order reaction kinetics with the highest efficiencies achieved of 97.6, >99.9, and 98.5% without presence of O2 for PFOA, PFNA, and PFOS, respectively. The degradation efficiencies increased with the increase of nZVI concentrations in the range of 1-100 mg/L. The degradation efficiency of PFOA using bare Fe0 NPs was higher than that using 1% PVP-coated Fe0 NPs in the initial 6 h. Second, the removal mechanism of PFAS in UVC/Fe0 NPs system was obtained by testing the concentrations of iron ions (Fe2+/Fe3+), intermediate products, and reactive oxygen species (ROS, e.g., ·O2- and ·OH) generated, and conducting ROS quenching experiments. The proposed degradation pathway of PFCAs (PFNA and PFOA) was initiated from PFOA/PFNA oxidation by transferring an electron of the carboxylate terminal group of PFOA/PFNA to the Fe(III)-carboxylate complex, then followed by decarboxylation−hydroxylation−elimination−hydrolysis (DHEH) pathway and the accompanying CO2 and F− release. The generated shorter chain PFCAs also underwent degradation with time in the system. This proposed degradation pathway was confirmed by the formation of shorter chain PFCAs, e.g. PFHpA, PFHxA, PFPeA, and PFBA, F- ions, and rapid consumption of Fe3+. For PFOS, besides H/F exchange pathway and chain-shortening (DHEH pathway) to form short chain PFAS during PFCA degradation, desulfonation to form PFOA followed by PFOA degradation also happened. These pathways were suggested by the formation of intermediates — trace amount of shorter chain PFCAs, 6:2 FTS, PFHpS, and F- ions. ·O2- and ·OH were not involved in PFOA degradation in the UVC/Fe0 NPs system with presence of O2, while they may be involved in PFOS degradation, e.g., desulfonation to form PFOA, which were suggested by the results of quenching experiments. And introducing H2O2 into the UVC/Fe0 NPs system resulted in lower PFOA degradation efficiency and defluorination efficiency, which also indicated that ·OH may not be involved in PFOA degradation. Hydrated electrons e-aq that can be involved in desulfonation, defluorination, and C-C bond scission processes were likely quenched by the presence of oxygen to reduce the degradation and defluorination efficiencies; plus, presence of Fe0 NPs may promote the generation of hydrated electrons. Last, UVC/Fe0 NPs system was used to degrade PFAS from WEs in both bench scale and in a scale up POU system. The degradation efficiencies of PFAS in WEs from both wastewater treatment plants (WWTP) were lower than that in deionized water, likely reflecting the complex compositions in the environmental media. Optimal degradation efficiencies of 90±1%, 88±1%, and 46±2% were obtained for PFNA, PFOS, and PFOA, respectively, each starting from 0.5 µg/L using bare Fe0 at pH 3.0 after 2 h. PFAS removal and bacterial inactivation were achieved simultaneously in the POU system using Fe0 NPs without and with rGO support under UVC irradiation in WEs, although the PFAS levels were still above the regulation levels for discard. These pilot tests provided more data and experiences for the real applications of UVC/Fe0 NP system to PFAS contaminated wastewater or other water matrix treatment. Overall, this research demonstrated a cost-effective and environment-friendly method — UVC/Fe0 NPs method for PFAS (i.e., PFOA, PFNA, and PFOS) degradation from WEs for water reuse both with and without presence of oxygen. The possible degradation mechanisms of PFAS with different structures were obtained by testing the concentrations of iron ions, intermediate products, and reactive oxygen species (ROS) involved in the reactions. The developed technology can be potentially applied to treat other environmental media (e.g., groundwater, landfill leachate) that are contaminated by PFAS from previous anthropogenic activities.

Colloidally-stable zero valent iron nanoparticles (nZVI) were synthesized through a classical redox reaction of iron sulfate with minor modifications using cellulose nanocrystals (CNCs) as stabilizers. We obtained spherical nZVI particles with high surface roughness and a mean size of 130nm. Particles remain colloidally stable after more than two months. Cellulose nanocrystals play a dual role in nZVI stability: a foreign surface to encourage stable nucleation over fast aggregation and a stabilizer to prevent iron nanoparticles aggregating into fractal colloids. Our results highlight the impact of the presence of CNCs on the rates and mechanisms of nucleation, growth, aggregation, and aging of nZVI particles, indicating promise in controlling size and morphology of similarly redox-generated nanoparticles. Cellulose nanocrystal-stabilized nZVI nanoparticles demonstrate properties well-suited for enhanced soil and groundwater remediation. //Nanocomposites composed of carboxylated cellulose nanocrystals and iron (Fe-oxCNC) were prepared through a classical redox reaction of iron sulfate using TEMPO-oxidized cellulose nanocrystals (oxCNCs) as a template and stabilizer. Morphological control over Fe-oxCNC nanoparticles was realized by varying the amount of oxCNC added to the redox process. As the molar ratio between oxCNC and Fe was increased from 1 to 8, the morphology of Fe-oxCNC nanoparticles evolved from rounded iron aggregates supported by cellulose nanocrystals to thin film iron-coatings on cellulose nanocrystals. Transmission electron microscopy (TEM), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), and chemical analyses (EDX, EELS) revealed that oxCNCs were coated by iron. Small changes to the density and type of functional groups on the CNC surface have large impacts on the morphology and the oxidation state of adsorbed iron nanoparticles. / Thesis / Master of Applied Science (MASc)

Human senses for taste, odor, and visual assessment allow consumers to be selective when it comes to choosing their drinking water. In addition to wanting aesthetically pleasing water to drink, consumers want to know if their water is safe and may have misconceptions on what possible health risk contaminants could be lurking in their water supply. This thesis aimed to measure reaction of zerovalent nanoiron (nZVI) in water and human saliva, evaluate consumer's perceptions of taste, odor, and risk in their drinking water, and investigate the effectiveness of community water systems in communicating water quality information to their consumers. Since nZVI, including commercially available Nanofer 25S, is widely being used in water treatment processes and has future potential for use in fortifying foods, the exposure to these engineered nanoparticles will increase for humans and aquatic organisms. Thus, the first part of the thesis was to develop a quantitative analytical technique to measure the iron levels at environmentally relevant concentrations. Researchers developed a colorimetric assay using 1, 10-phenanthroline as an assay to determine the amount of ferrous ions produced from different iron materials, including ferrous(II)sulfate, nZVI, and goethite. Resulting ferrous ion measurements indicate that the maximum production of ferrous ions varied among the iron materials. Nanofer25S did not undergo 100% conversion to ferrous ions, as expected, goethite had no production of ferrous ions, and ferrous(II)sulfate was 100% ferrous ions. The total iron, as measured by atomic absorption for all iron materials were equal. The reactivity of these iron materials were also assessed in different water qualities ranging in salt concentrations. The capacity to produce ferrous ion did not change when added to nanopure water, tap water, and inorganic solution that is equivalent to the high ionic strength of saliva. Toxicology data for nZVI exposure to humans and aquatic organisms are limited. For that reason, authors of this manuscript measured salivary lipid oxidation (SLO) potential for the different iron materials in human saliva. They also developed an artificial saliva recipe to ensure repeatability and comparable results among laboratories due to human saliva's variability day by day. This simulated human saliva contained salts, proteins, and lipids. Using thiobarbituric acid reactive substances (TBARs), both Nanofer25S and ferrous(II)sulfate induced in-vitro SLO with human saliva. Goethite was unreactive. SLO results from this study have implications for flavor effects of nZVI in drinking water. The second chapter of this thesis is assessing the clarity of message communication of Consumer Confidence Reports (CCRs). In 1998, the United States Environmental Protection Agency (USEPA) mandated that community water systems (CWSs) provide annual water quality reports to their consumers. These CCRs summarize information regarding water sources, any detected contaminants, compliance with federal regulations, and educational information. Thirty CCRs across all ten USEPA regions were analyzed for clarity using the Centers for Disease Control and Prevention's (CDC) Clear Communication Index (CCI) tool. The analysis of these CCRs was a national representation of CWSs and revealed that currently distributed CCRs performed poorly on the CDC's CCI—all failing to meet the 90% passing mark. The overall average score for all CCRs was 50.3 ± 13.5%. The clarity scores were based on seven key areas: 1) Main message and call to action; 2) Language; 3) Information design; 4) State of the science; 5) Behavioral recommendations; 6) Numbers; and 7) Risk. Improvements in all seven areas—with the lowest average scores at 3.3 ± 18.1%, 21.7 ± 26.6%, and 37.7 ± 27.1%, respectively, for state of science, language, and main message and call to action—of the CCI will greatly improve the quality and educational capabilities of CCRs. The failing scores highlight the challenges facing CWSs in communicating water quality information. This assessment can serve as a tool for water utilities to effectively prepare and distribute information to their consumers in the future. CWSs must promote a two-way dialogue with their consumers. They should address consumer's concerns and wants in the CCRs, and they should also effectively communicate risks to the consumers so that they are not under the misconception that their water is unsafe to drink. CWSs should use the CCRs as a way to educate the public and promote drinking tap water. The last chapter of this thesis addresses the concerns that consumers may have about their drinking water and methods that could be implemented to quickly and efficiently respond to consumer complaints and contaminants with sensory properties. Just like CWSs, consumers are concerned about their water; they are the sentinels to water quality monitoring because they are uniquely positioned at the tap. Consumers are able to detect the slightest taste, odor, and appearance in their drinking water because it is well—instinctive! Thus, consumer feedback and complaint data provided to a utility should be taken seriously and stored for future comparisons. Any consumer complaint represents a fruitful data stream that should be harnessed routinely to gain knowledge about aesthetic water quality in the distribution system. Four utilities provided consumer complaints on water quality data that were categorized and visualized using radar and run-time plots. As a result, major taste, odor, and appearance patterns emerged that clarified the issue and could provide guidance to the utilities on the nature and extent of the problem. Consumer complaint data is valuable for water quality issue identification, but CWSs should understand that even though humans readily identify visual issues with water, such as color, cloudiness, or rust, describing specific tastes and particularly odors in drinking water is acknowledged to be a much more difficult task for humans to achieve without training. This was demonstrated with two utility groups, laboratory personnel and plant operators, and a group of consumers identifying the odor of orange, 2-MIB, and DMTS. All of the groups were able to identify the familiar orange odor. However, the two utility groups were much more able to identify the musty odor of 2-MIB; this may be due to the fact that the utility groups are more familiar with raw and finished water. DMTS, a garlic-onion odor associated with sulfur compounds in drinking water, was the least familiar to all three groups. The lab personnel group was the better describers of the odor, but the results within this group still varied significantly. These results suggest that utility personnel should be mindful of consumers who complain that their water is different, but cannot describe the problem. To reduce the inability to describe an odor or taste issue, a TandO program at a utility can be beneficial. The safety and aesthetic characteristics of drinking water is most important to consumers. They both complement each other; if consumers think their water tastes funny, they would probably assume that is unsafe to drink. Since nZVI is increasingly being introduced into the drinking water supply, researchers must be able to understand how it reacts in humans and the environment. Additionally, CCRs would be an effective method for CWSs to communicate water quality information and address any concerns consumers may have about their water. CWSs can use implement the radar and run-time plots to identify issues in the drinking water systems. Also, TandO programs will allow CWSs and their consumers to better describe and identify the issues in their drinking water as it arises so that it can be easily addressed and alleviated. Thus, promoting communication between water utilities and their consumers will improve the relationship and instill confidence in consumers about their drinking water. / Master of Science